Hi
I am working on an IR detector that will guide a robot into a docking station.
A IR transmitter on the docking station transmits a beam, and 2 IR
detectors on the robot detects the beam and lets the robot navigate
towards the target. The working distance is a couple of meters.
I need it to be insensitive to ambient light/sunlight.
The IR detectors are placed in a tube, to narrow in the beam angle and
to avoid sunlight (since it is seldom the sun is actually that low in
the horizon)
The IR transmitter will be modulated with 10kHz (TBD) frequency, low
duty cycle. Low duty cycle to be able to drive the LED with high
current, frequency modulated so that the receiver can ignore the effect
of daylight (DC)
If the LED on the docking station has higher radiant intensity at the
point of the robot (2 meters away) than possible IR from sunlight, then
that would be perfect.
Example of transmitter:
https://www.vishay.com/docs/83398/vsmy2850.pdf
Has up to 1000mW/sr. Seems my basic calculation for a 15 degree beam,
shows less than 10nW/m2, while sunlight has 1W/m2. So driving a beam
that has higher output than sunlight seems unlikely.
I would use a IR phototransistor at 850nm, something like this:
https://www.ttelectronics.com/TTElectronics/media/ProductFiles/Datasheet/OP505-506-535-705.pdf
Or a photo diode:
https://docs.rs-online.com/9f58/0900766b816d8a09.pdf
Fed from reverse 3.3V and into a transimpedance amplifier to boost the
signal with bandpass filter.
One can get digital IR detector used in a remote control systems:
https://www.vishay.com/docs/82491/tsop382.pdf
It has AGC, but digital output. I need analog output to be able to zero
in on the transmitter beam.
I have been looking for IR detectors that has the analog output, not
just the digital, but have not found any.
If the photodiode detector is subjected to sunlight, I am guessing I
would need very high gain on the 10kHz modulation frequency to pick up
the burried signal in the DC from sunlight.
How do I best bias the photo diode for optimum detection of the 10kHz
signal while being immune to the ambient sunlight?
I have chosen 850nm which seems to be a good wavelength. The spectrum at
sea level has some dips due to water absorption.
https://sciencetech-inc.com/web/image/49169/Spectrum%20with_out%20absorption.png
Seems like 750nm would be better, since then the IR from the sun is
lower, but does reduced the effective range of the system during
fog/rain. Probably that's why these system do not use 750nm
Other considerations?
Hi
I am working on an IR detector that will guide a robot into a docking >station.
A IR transmitter on the docking station transmits a beam, and 2 IR
detectors on the robot detects the beam and lets the robot navigate
towards the target. The working distance is a couple of meters.
I need it to be insensitive to ambient light/sunlight.
The IR detectors are placed in a tube, to narrow in the beam angle and
to avoid sunlight (since it is seldom the sun is actually that low in
the horizon)
The IR transmitter will be modulated with 10kHz (TBD) frequency, low
duty cycle. Low duty cycle to be able to drive the LED with high
current, frequency modulated so that the receiver can ignore the effect
of daylight (DC)
If the LED on the docking station has higher radiant intensity at the
point of the robot (2 meters away) than possible IR from sunlight, then
that would be perfect.
Example of transmitter:
https://www.vishay.com/docs/83398/vsmy2850.pdf
Has up to 1000mW/sr. Seems my basic calculation for a 15 degree beam,
shows less than 10nW/m2, while sunlight has 1W/m2. So driving a beam
that has higher output than sunlight seems unlikely.
I would use a IR phototransistor at 850nm, something like this:
https://www.ttelectronics.com/TTElectronics/media/ProductFiles/Datasheet/OP505-506-535-705.pdf
Or a photo diode:
https://docs.rs-online.com/9f58/0900766b816d8a09.pdf
Fed from reverse 3.3V and into a transimpedance amplifier to boost the
signal with bandpass filter.
One can get digital IR detector used in a remote control systems:
https://www.vishay.com/docs/82491/tsop382.pdf
It has AGC, but digital output. I need analog output to be able to zero
in on the transmitter beam.
I have been looking for IR detectors that has the analog output, not
just the digital, but have not found any.
If the photodiode detector is subjected to sunlight, I am guessing I
would need very high gain on the 10kHz modulation frequency to pick up
the burried signal in the DC from sunlight.
How do I best bias the photo diode for optimum detection of the 10kHz
signal while being immune to the ambient sunlight?
I have chosen 850nm which seems to be a good wavelength. The spectrum at
sea level has some dips due to water absorption.
https://sciencetech-inc.com/web/image/49169/Spectrum%20with_out%20absorption.png
Seems like 750nm would be better, since then the IR from the sun is
lower, but does reduced the effective range of the system during
fog/rain. Probably that's why these system do not use 750nm
Other considerations?
Klaus Vestergaard Kragelund <klauskvik@hotmail.com> wrote:
Hi
I am working on an IR detector that will guide a robot into a docking
station.
A IR transmitter on the docking station transmits a beam, and 2 IR
detectors on the robot detects the beam and lets the robot navigate
towards the target. The working distance is a couple of meters.
I need it to be insensitive to ambient light/sunlight.
The IR detectors are placed in a tube, to narrow in the beam angle and
to avoid sunlight (since it is seldom the sun is actually that low in
the horizon)
The IR transmitter will be modulated with 10kHz (TBD) frequency, low
duty cycle. Low duty cycle to be able to drive the LED with high
current, frequency modulated so that the receiver can ignore the effect
of daylight (DC)
If the LED on the docking station has higher radiant intensity at the
point of the robot (2 meters away) than possible IR from sunlight, then
that would be perfect.
Example of transmitter:
https://www.vishay.com/docs/83398/vsmy2850.pdf
Has up to 1000mW/sr. Seems my basic calculation for a 15 degree beam,
shows less than 10nW/m2, while sunlight has 1W/m2. So driving a beam
that has higher output than sunlight seems unlikely.
I would use a IR phototransistor at 850nm, something like this:
https://www.ttelectronics.com/TTElectronics/media/ProductFiles/Datasheet/OP505-506-535-705.pdf
Or a photo diode:
https://docs.rs-online.com/9f58/0900766b816d8a09.pdf
Fed from reverse 3.3V and into a transimpedance amplifier to boost the
signal with bandpass filter.
One can get digital IR detector used in a remote control systems:
https://www.vishay.com/docs/82491/tsop382.pdf
It has AGC, but digital output. I need analog output to be able to zero
in on the transmitter beam.
I have been looking for IR detectors that has the analog output, not
just the digital, but have not found any.
If the photodiode detector is subjected to sunlight, I am guessing I
would need very high gain on the 10kHz modulation frequency to pick up
the buried signal in the DC from sunlight.
How do I best bias the photo diode for optimum detection of the 10kHz
signal while being immune to the ambient sunlight?
I have chosen 850nm which seems to be a good wavelength. The spectrum at
sea level has some dips due to water absorption.
https://sciencetech-inc.com/web/image/49169/Spectrum%20with_out%20absorption.png
Seems like 750nm would be better, since then the IR from the sun is
lower, but does reduced the effective range of the system during
fog/rain. Probably that's why these system do not use 750nm
Other considerations?
Phototransistors are horrible for that sort of job— too small, too noisy, not repeatable, for a start.
It’s not signal/background you care about, it’s signal/noise, specifically
the shot noise of the sunlight.
An optical filter will help reject sunlight, and a bigger detector will
help more. The real win is reducing the FOV with lenses as well as baffles, tubes, and so on.
Check out the Hamamatsu S6968–super good medicine.
On Sun, 27 Oct 2024 02:19:14 +0200, Klaus Vestergaard Kragelund <klauskvik@hotmail.com> wrote:
Hi
I am working on an IR detector that will guide a robot into a docking
station.
A IR transmitter on the docking station transmits a beam, and 2 IR
detectors on the robot detects the beam and lets the robot navigate
towards the target. The working distance is a couple of meters.
I need it to be insensitive to ambient light/sunlight.
The IR detectors are placed in a tube, to narrow in the beam angle and
to avoid sunlight (since it is seldom the sun is actually that low in
the horizon)
The IR transmitter will be modulated with 10kHz (TBD) frequency, low
duty cycle. Low duty cycle to be able to drive the LED with high
current, frequency modulated so that the receiver can ignore the effect
of daylight (DC)
If the LED on the docking station has higher radiant intensity at the
point of the robot (2 meters away) than possible IR from sunlight, then
that would be perfect.
Example of transmitter:
https://www.vishay.com/docs/83398/vsmy2850.pdf
Has up to 1000mW/sr. Seems my basic calculation for a 15 degree beam,
shows less than 10nW/m2, while sunlight has 1W/m2. So driving a beam
that has higher output than sunlight seems unlikely.
I would use a IR phototransistor at 850nm, something like this:
https://www.ttelectronics.com/TTElectronics/media/ProductFiles/Datasheet/OP505-506-535-705.pdf
Or a photo diode:
https://docs.rs-online.com/9f58/0900766b816d8a09.pdf
Fed from reverse 3.3V and into a transimpedance amplifier to boost the
signal with bandpass filter.
One can get digital IR detector used in a remote control systems:
https://www.vishay.com/docs/82491/tsop382.pdf
It has AGC, but digital output. I need analog output to be able to zero
in on the transmitter beam.
I have been looking for IR detectors that has the analog output, not
just the digital, but have not found any.
If the photodiode detector is subjected to sunlight, I am guessing I
would need very high gain on the 10kHz modulation frequency to pick up
the burried signal in the DC from sunlight.
How do I best bias the photo diode for optimum detection of the 10kHz
signal while being immune to the ambient sunlight?
I have chosen 850nm which seems to be a good wavelength. The spectrum at
sea level has some dips due to water absorption.
https://sciencetech-inc.com/web/image/49169/Spectrum%20with_out%20absorption.png
Seems like 750nm would be better, since then the IR from the sun is
lower, but does reduced the effective range of the system during
fog/rain. Probably that's why these system do not use 750nm
Other considerations?
You could drive the LED with a square wave, 10 KHz or whatever. The photodiode could have +DC on one end and the other end can hit a
parallel LC to ground, resonant at 10K.
That takes out the sunlight DC component and adds bandpass filtering.
Just don't fry the photodiode in high light.
An optical bandpass filter would hugely improve things, take out most
of the sunlight.
Hi
I am working on an IR detector that will guide a robot into a docking >station.
A IR transmitter on the docking station transmits a beam, and 2 IR
detectors on the robot detects the beam and lets the robot navigate
towards the target. The working distance is a couple of meters.
I need it to be insensitive to ambient light/sunlight.
Klaus Vestergaard Kragelund <klauskvik@hotmail.com> wrote:
Hi
I am working on an IR detector that will guide a robot into a docking
station.
A IR transmitter on the docking station transmits a beam, and 2 IR
detectors on the robot detects the beam and lets the robot navigate
towards the target. The working distance is a couple of meters.
I need it to be insensitive to ambient light/sunlight.
The IR detectors are placed in a tube, to narrow in the beam angle and
to avoid sunlight (since it is seldom the sun is actually that low in
the horizon)
The IR transmitter will be modulated with 10kHz (TBD) frequency, low
duty cycle. Low duty cycle to be able to drive the LED with high
current, frequency modulated so that the receiver can ignore the effect
of daylight (DC)
If the LED on the docking station has higher radiant intensity at the
point of the robot (2 meters away) than possible IR from sunlight, then
that would be perfect.
Example of transmitter:
https://www.vishay.com/docs/83398/vsmy2850.pdf
Has up to 1000mW/sr. Seems my basic calculation for a 15 degree beam,
shows less than 10nW/m2, while sunlight has 1W/m2. So driving a beam
that has higher output than sunlight seems unlikely.
I would use a IR phototransistor at 850nm, something like this:
https://www.ttelectronics.com/TTElectronics/media/ProductFiles/Datasheet/OP505-506-535-705.pdf
Or a photo diode:
https://docs.rs-online.com/9f58/0900766b816d8a09.pdf
Fed from reverse 3.3V and into a transimpedance amplifier to boost the
signal with bandpass filter.
One can get digital IR detector used in a remote control systems:
https://www.vishay.com/docs/82491/tsop382.pdf
It has AGC, but digital output. I need analog output to be able to zero
in on the transmitter beam.
I have been looking for IR detectors that has the analog output, not
just the digital, but have not found any.
If the photodiode detector is subjected to sunlight, I am guessing I
would need very high gain on the 10kHz modulation frequency to pick up
the burried signal in the DC from sunlight.
How do I best bias the photo diode for optimum detection of the 10kHz
signal while being immune to the ambient sunlight?
I have chosen 850nm which seems to be a good wavelength. The spectrum at
sea level has some dips due to water absorption.
https://sciencetech-inc.com/web/image/49169/Spectrum%20with_out%20absorption.png
Seems like 750nm would be better, since then the IR from the sun is
lower, but does reduced the effective range of the system during
fog/rain. Probably that's why these system do not use 750nm
Other considerations?
Phototransistors are horrible for that sort of job— too small, too noisy, not repeatable, for a start.
It’s not signal/background you care about, it’s signal/noise, specifically
the shot noise of the sunlight.
An optical filter will help reject sunlight, and a bigger detector will
help more. The real win is reducing the FOV with lenses as well as baffles, tubes, and so on.
Check out the Hamamatsu S6968–super good medicine.
On a sunny day (Sun, 27 Oct 2024 02:19:14 +0200) it happened Klaus Vestergaard
Kragelund <klauskvik@hotmail.com> wrote in <vfk0u0$3u9en$1@dont-email.me>:
Hi
I am working on an IR detector that will guide a robot into a docking
station.
A IR transmitter on the docking station transmits a beam, and 2 IR
detectors on the robot detects the beam and lets the robot navigate
towards the target. The working distance is a couple of meters.
I need it to be insensitive to ambient light/sunlight.
I use a cheap camera module to track a light source in H and V direction, and just a simple Microchip PIC : for processing
It can, with some added code, track object forms too, like a cross or maybe a big character.
panteltje.nl/pub/horizontal_IR_target_tracking_4686.avi
those camara modulea are IR sensitive to some extend, sometimes you can remove the IR filter from such modules.
It may be a bit of overkill for your application, but OTOH it can do a lot more.
Mainly designed to detect and follow jet exhaust..
You could uee utrasonics too, maybe even simpler, no sun problem, like a bat. Cheap electret mikes? or modify some ebay 1 dolalr distance sensors...
can be used for anti-collision too.
On Sun, 27 Oct 2024 02:19:14 +0200, Klaus Vestergaard Kragelund <klauskvik@hotmail.com> wrote:
Hi
I am working on an IR detector that will guide a robot into a docking
station.
A IR transmitter on the docking station transmits a beam, and 2 IR
detectors on the robot detects the beam and lets the robot navigate
towards the target. The working distance is a couple of meters.
I need it to be insensitive to ambient light/sunlight.
The IR detectors are placed in a tube, to narrow in the beam angle and
to avoid sunlight (since it is seldom the sun is actually that low in
the horizon)
The IR transmitter will be modulated with 10kHz (TBD) frequency, low
duty cycle. Low duty cycle to be able to drive the LED with high
current, frequency modulated so that the receiver can ignore the effect
of daylight (DC)
If the LED on the docking station has higher radiant intensity at the
point of the robot (2 meters away) than possible IR from sunlight, then
that would be perfect.
Example of transmitter:
https://www.vishay.com/docs/83398/vsmy2850.pdf
Has up to 1000mW/sr. Seems my basic calculation for a 15 degree beam,
shows less than 10nW/m2, while sunlight has 1W/m2. So driving a beam
that has higher output than sunlight seems unlikely.
I would use a IR phototransistor at 850nm, something like this:
https://www.ttelectronics.com/TTElectronics/media/ProductFiles/Datasheet/OP505-506-535-705.pdf
Or a photo diode:
https://docs.rs-online.com/9f58/0900766b816d8a09.pdf
Fed from reverse 3.3V and into a transimpedance amplifier to boost the
signal with bandpass filter.
One can get digital IR detector used in a remote control systems:
https://www.vishay.com/docs/82491/tsop382.pdf
It has AGC, but digital output. I need analog output to be able to zero
in on the transmitter beam.
I have been looking for IR detectors that has the analog output, not
just the digital, but have not found any.
If the photodiode detector is subjected to sunlight, I am guessing I
would need very high gain on the 10kHz modulation frequency to pick up
the burried signal in the DC from sunlight.
How do I best bias the photo diode for optimum detection of the 10kHz
signal while being immune to the ambient sunlight?
I have chosen 850nm which seems to be a good wavelength. The spectrum at
sea level has some dips due to water absorption.
https://sciencetech-inc.com/web/image/49169/Spectrum%20with_out%20absorption.png
Seems like 750nm would be better, since then the IR from the sun is
lower, but does reduced the effective range of the system during
fog/rain. Probably that's why these system do not use 750nm
Other considerations?
You could drive the LED with a square wave, 10 KHz or whatever. The photodiode could have +DC on one end and the other end can hit a
parallel LC to ground, resonant at 10K.
That takes out the sunlight DC component and adds bandpass filtering.
Just don't fry the photodiode in high light.
On 27/10/2024 1:05 pm, Phil Hobbs wrote:
Klaus Vestergaard Kragelund <klauskvik@hotmail.com> wrote:
Hi
I am working on an IR detector that will guide a robot into a docking
station.
A IR transmitter on the docking station transmits a beam, and 2 IR
detectors on the robot detects the beam and lets the robot navigate
towards the target. The working distance is a couple of meters.
I need it to be insensitive to ambient light/sunlight.
The IR detectors are placed in a tube, to narrow in the beam angle and
to avoid sunlight (since it is seldom the sun is actually that low in
the horizon)
The IR transmitter will be modulated with 10kHz (TBD) frequency, low
duty cycle. Low duty cycle to be able to drive the LED with high
current, frequency modulated so that the receiver can ignore the effect
of daylight (DC)
If the LED on the docking station has higher radiant intensity at the
point of the robot (2 meters away) than possible IR from sunlight, then
that would be perfect.
Example of transmitter:
https://www.vishay.com/docs/83398/vsmy2850.pdf
Has up to 1000mW/sr. Seems my basic calculation for a 15 degree beam,
shows less than 10nW/m2, while sunlight has 1W/m2. So driving a beam
that has higher output than sunlight seems unlikely.
I would use a IR phototransistor at 850nm, something like this:
https://www.ttelectronics.com/TTElectronics/media/ProductFiles/
Datasheet/OP505-506-535-705.pdf
Or a photo diode:
https://docs.rs-online.com/9f58/0900766b816d8a09.pdf
Fed from reverse 3.3V and into a transimpedance amplifier to boost the
signal with bandpass filter.
One can get digital IR detector used in a remote control systems:
https://www.vishay.com/docs/82491/tsop382.pdf
It has AGC, but digital output. I need analog output to be able to zero
in on the transmitter beam.
I have been looking for IR detectors that has the analog output, not
just the digital, but have not found any.
If the photodiode detector is subjected to sunlight, I am guessing I
would need very high gain on the 10kHz modulation frequency to pick up
the buried signal in the DC from sunlight.
If the sunlight signal doesn't just saturate the signal chain, which
wrecks the gain.
How do I best bias the photo diode for optimum detection of the 10kHz
signal while being immune to the ambient sunlight?
Bias doesn't really matter unless you are looking for avalanche multiplication of the charge carriers - if there there's enough bias to
let you collect all of them. Single photon avalanche diodes are a
different can of worms, but you should have plenty of photons, so why
would you bother?
More bias does reduce the capacitance across the detection diode, making
it a bit faster, but the reduction is a hyperbolic function of bias, so
each extra volt makes progressively less difference.
I have chosen 850nm which seems to be a good wavelength. The spectrum at >>> sea level has some dips due to water absorption.
https://sciencetech-inc.com/web/image/49169/
Spectrum%20with_out%20absorption.png
Seems like 750nm would be better, since then the IR from the sun is
lower, but does reduced the effective range of the system during
fog/rain. Probably that's why these system do not use 750nm
Other considerations?
Phototransistors are horrible for that sort of job— too small, too noisy, >> not repeatable, for a start.
It’s not signal/background you care about, it’s signal/noise,
specifically
the shot noise of the sunlight.
An optical filter will help reject sunlight, and a bigger detector will
help more. The real win is reducing the FOV with lenses as well as
baffles,
tubes, and so on.
In a vaguely similar sort of situation I got my mechanical colleagues to
put a graphite liner inside the tube, and cut a screw thread into the
liner. They thought I was nuts, until they skipped cutting the screw
thread and I promptly complained about the loss of performance.
Check out the Hamamatsu S6968–super good medicine.
Hamamatsu do seem to have good products.
On 27-10-2024 03:26, john larkin wrote:
On Sun, 27 Oct 2024 02:19:14 +0200, Klaus Vestergaard Kragelund
<klauskvik@hotmail.com> wrote:
Hi
I am working on an IR detector that will guide a robot into a docking
station.
A IR transmitter on the docking station transmits a beam, and 2 IR
detectors on the robot detects the beam and lets the robot navigate
towards the target. The working distance is a couple of meters.
I need it to be insensitive to ambient light/sunlight.
The IR detectors are placed in a tube, to narrow in the beam angle and
to avoid sunlight (since it is seldom the sun is actually that low in
the horizon)
The IR transmitter will be modulated with 10kHz (TBD) frequency, low
duty cycle. Low duty cycle to be able to drive the LED with high
current, frequency modulated so that the receiver can ignore the effect
of daylight (DC)
If the LED on the docking station has higher radiant intensity at the
point of the robot (2 meters away) than possible IR from sunlight, then
that would be perfect.
Example of transmitter:
https://www.vishay.com/docs/83398/vsmy2850.pdf
Has up to 1000mW/sr. Seems my basic calculation for a 15 degree beam,
shows less than 10nW/m2, while sunlight has 1W/m2. So driving a beam
that has higher output than sunlight seems unlikely.
I would use a IR phototransistor at 850nm, something like this:
https://www.ttelectronics.com/TTElectronics/media/ProductFiles/
Datasheet/OP505-506-535-705.pdf
Or a photo diode:
https://docs.rs-online.com/9f58/0900766b816d8a09.pdf
Fed from reverse 3.3V and into a transimpedance amplifier to boost the
signal with bandpass filter.
One can get digital IR detector used in a remote control systems:
https://www.vishay.com/docs/82491/tsop382.pdf
It has AGC, but digital output. I need analog output to be able to zero
in on the transmitter beam.
I have been looking for IR detectors that has the analog output, not
just the digital, but have not found any.
If the photodiode detector is subjected to sunlight, I am guessing I
would need very high gain on the 10kHz modulation frequency to pick up
the burried signal in the DC from sunlight.
How do I best bias the photo diode for optimum detection of the 10kHz
signal while being immune to the ambient sunlight?
I have chosen 850nm which seems to be a good wavelength. The spectrum at >>> sea level has some dips due to water absorption.
https://sciencetech-inc.com/web/image/49169/
Spectrum%20with_out%20absorption.png
Seems like 750nm would be better, since then the IR from the sun is
lower, but does reduced the effective range of the system during
fog/rain. Probably that's why these system do not use 750nm
Other considerations?
You could drive the LED with a square wave, 10 KHz or whatever. The
photodiode could have +DC on one end and the other end can hit a
parallel LC to ground, resonant at 10K.
That takes out the sunlight DC component and adds bandpass filtering.
That's a very nice idea. The Q should not matter much, just as long as
DC is removed.
The photodiode will still be subjected to the high ambient light, but
the gain would be close to zero for the stage after. I would then still
need to be sure the photodiode is never saturated by ambient light.
On 27-10-2024 13:26, Klaus Vestergaard Kragelund wrote:
On 27-10-2024 03:26, john larkin wrote:Actually, wont a simple high pass filter work equally well?
On Sun, 27 Oct 2024 02:19:14 +0200, Klaus Vestergaard Kragelund
<klauskvik@hotmail.com> wrote:
Hi
I am working on an IR detector that will guide a robot into a docking
station.
A IR transmitter on the docking station transmits a beam, and 2 IR
detectors on the robot detects the beam and lets the robot navigate
towards the target. The working distance is a couple of meters.
I need it to be insensitive to ambient light/sunlight.
The IR detectors are placed in a tube, to narrow in the beam angle and >>>> to avoid sunlight (since it is seldom the sun is actually that low in
the horizon)
The IR transmitter will be modulated with 10kHz (TBD) frequency, low
duty cycle. Low duty cycle to be able to drive the LED with high
current, frequency modulated so that the receiver can ignore the effect >>>> of daylight (DC)
If the LED on the docking station has higher radiant intensity at the
point of the robot (2 meters away) than possible IR from sunlight, then >>>> that would be perfect.
Example of transmitter:
https://www.vishay.com/docs/83398/vsmy2850.pdf
Has up to 1000mW/sr. Seems my basic calculation for a 15 degree beam,
shows less than 10nW/m2, while sunlight has 1W/m2. So driving a beam
that has higher output than sunlight seems unlikely.
I would use a IR phototransistor at 850nm, something like this:
https://www.ttelectronics.com/TTElectronics/media/ProductFiles/
Datasheet/OP505-506-535-705.pdf
Or a photo diode:
https://docs.rs-online.com/9f58/0900766b816d8a09.pdf
Fed from reverse 3.3V and into a transimpedance amplifier to boost the >>>> signal with bandpass filter.
One can get digital IR detector used in a remote control systems:
https://www.vishay.com/docs/82491/tsop382.pdf
It has AGC, but digital output. I need analog output to be able to zero >>>> in on the transmitter beam.
I have been looking for IR detectors that has the analog output, not
just the digital, but have not found any.
If the photodiode detector is subjected to sunlight, I am guessing I
would need very high gain on the 10kHz modulation frequency to pick up >>>> the burried signal in the DC from sunlight.
How do I best bias the photo diode for optimum detection of the 10kHz
signal while being immune to the ambient sunlight?
I have chosen 850nm which seems to be a good wavelength. The
spectrum at
sea level has some dips due to water absorption.
https://sciencetech-inc.com/web/image/49169/
Spectrum%20with_out%20absorption.png
Seems like 750nm would be better, since then the IR from the sun is
lower, but does reduced the effective range of the system during
fog/rain. Probably that's why these system do not use 750nm
Other considerations?
You could drive the LED with a square wave, 10 KHz or whatever. The
photodiode could have +DC on one end and the other end can hit a
parallel LC to ground, resonant at 10K.
That takes out the sunlight DC component and adds bandpass filtering.
That's a very nice idea. The Q should not matter much, just as long as
DC is removed.
The photodiode will still be subjected to the high ambient light, but
the gain would be close to zero for the stage after. I would then
still need to be sure the photodiode is never saturated by ambient light.
Photo diode with bias -> capacitor to gain block....
On 27-10-2024 03:05, Phil Hobbs wrote:
Klaus Vestergaard Kragelund <klauskvik@hotmail.com> wrote:
Hi
I am working on an IR detector that will guide a robot into a docking
station.
A IR transmitter on the docking station transmits a beam, and 2 IR
detectors on the robot detects the beam and lets the robot navigate
towards the target. The working distance is a couple of meters.
I need it to be insensitive to ambient light/sunlight.
The IR detectors are placed in a tube, to narrow in the beam angle and
to avoid sunlight (since it is seldom the sun is actually that low in
the horizon)
The IR transmitter will be modulated with 10kHz (TBD) frequency, low
duty cycle. Low duty cycle to be able to drive the LED with high
current, frequency modulated so that the receiver can ignore the effect
of daylight (DC)
If the LED on the docking station has higher radiant intensity at the
point of the robot (2 meters away) than possible IR from sunlight, then
that would be perfect.
Example of transmitter:
https://www.vishay.com/docs/83398/vsmy2850.pdf
Has up to 1000mW/sr. Seems my basic calculation for a 15 degree beam,
shows less than 10nW/m2, while sunlight has 1W/m2. So driving a beam
that has higher output than sunlight seems unlikely.
I would use a IR phototransistor at 850nm, something like this:
https://www.ttelectronics.com/TTElectronics/media/ProductFiles/Datasheet/OP505-506-535-705.pdf
Or a photo diode:
https://docs.rs-online.com/9f58/0900766b816d8a09.pdf
Fed from reverse 3.3V and into a transimpedance amplifier to boost the
signal with bandpass filter.
One can get digital IR detector used in a remote control systems:
https://www.vishay.com/docs/82491/tsop382.pdf
It has AGC, but digital output. I need analog output to be able to zero
in on the transmitter beam.
I have been looking for IR detectors that has the analog output, not
just the digital, but have not found any.
If the photodiode detector is subjected to sunlight, I am guessing I
would need very high gain on the 10kHz modulation frequency to pick up
the burried signal in the DC from sunlight.
How do I best bias the photo diode for optimum detection of the 10kHz
signal while being immune to the ambient sunlight?
I have chosen 850nm which seems to be a good wavelength. The spectrum at >>> sea level has some dips due to water absorption.
https://sciencetech-inc.com/web/image/49169/Spectrum%20with_out%20absorption.png
Seems like 750nm would be better, since then the IR from the sun is
lower, but does reduced the effective range of the system during
fog/rain. Probably that's why these system do not use 750nm
Other considerations?
Phototransistors are horrible for that sort of job— too small, too noisy, >> not repeatable, for a start.
It’s not signal/background you care about, it’s signal/noise,
specifically
the shot noise of the sunlight.
An optical filter will help reject sunlight, and a bigger detector will
help more. The real win is reducing the FOV with lenses as well as
baffles,
tubes, and so on.
I have tried to search for optical filters. Where would one get those?
Hi
I am working on an IR detector that will guide a robot into a docking station.
A IR transmitter on the docking station transmits a beam, and 2 IR detectors on
the robot detects the beam and lets the robot navigate towards the target. The
working distance is a couple of meters.
john larkin <JL@gct.com> wrote:
On Sun, 27 Oct 2024 02:19:14 +0200, Klaus Vestergaard Kragelund <klauskvik@hotmail.com> wrote:
Hi
I am working on an IR detector that will guide a robot into a docking
station.
A IR transmitter on the docking station transmits a beam, and 2 IR
detectors on the robot detects the beam and lets the robot navigate
towards the target. The working distance is a couple of meters.
I need it to be insensitive to ambient light/sunlight.
The IR detectors are placed in a tube, to narrow in the beam angle and
to avoid sunlight (since it is seldom the sun is actually that low in
the horizon)
The IR transmitter will be modulated with 10kHz (TBD) frequency, low
duty cycle. Low duty cycle to be able to drive the LED with high
current, frequency modulated so that the receiver can ignore the effect
of daylight (DC)
If the LED on the docking station has higher radiant intensity at the
point of the robot (2 meters away) than possible IR from sunlight, then
that would be perfect.
Example of transmitter:
https://www.vishay.com/docs/83398/vsmy2850.pdf
Has up to 1000mW/sr. Seems my basic calculation for a 15 degree beam,
shows less than 10nW/m2, while sunlight has 1W/m2. So driving a beam
that has higher output than sunlight seems unlikely.
I would use a IR phototransistor at 850nm, something like this:
https://www.ttelectronics.com/TTElectronics/media/ProductFiles/Datashee
t/OP505-506-535-705.pdf
Or a photo diode:
https://docs.rs-online.com/9f58/0900766b816d8a09.pdf
Fed from reverse 3.3V and into a transimpedance amplifier to boost the
signal with bandpass filter.
One can get digital IR detector used in a remote control systems:
https://www.vishay.com/docs/82491/tsop382.pdf
It has AGC, but digital output. I need analog output to be able to zero
in on the transmitter beam.
I have been looking for IR detectors that has the analog output, not
just the digital, but have not found any.
If the photodiode detector is subjected to sunlight, I am guessing I
would need very high gain on the 10kHz modulation frequency to pick up
the burried signal in the DC from sunlight.
How do I best bias the photo diode for optimum detection of the 10kHz
signal while being immune to the ambient sunlight?
I have chosen 850nm which seems to be a good wavelength. The spectrum at >> sea level has some dips due to water absorption.
https://sciencetech-inc.com/web/image/49169/Spectrum%20with_out%20absor
ption.png
Seems like 750nm would be better, since then the IR from the sun is
lower, but does reduced the effective range of the system during
fog/rain. Probably that's why these system do not use 750nm
Other considerations?
You could drive the LED with a square wave, 10 KHz or whatever. The photodiode could have +DC on one end and the other end can hit a
parallel LC to ground, resonant at 10K.
That takes out the sunlight DC component and adds bandpass filtering.
Just don't fry the photodiode in high light.
An optical bandpass filter would hugely improve things, take out most
of the sunlight.
Yes, the classic solution was to operate PD into an inductor so DC didn’t overload.
On 10/26/2024 5:19 PM, Klaus Vestergaard Kragelund wrote:
Hi
I am working on an IR detector that will guide a robot into a docking
station.
A IR transmitter on the docking station transmits a beam, and 2 IR
detectors on the robot detects the beam and lets the robot navigate
towards the target. The working distance is a couple of meters.
Can the robot ALWAYS see the docking station? What happens if an
obstacle (wall?) comes between the two?
Can either device (robot/dock) ever slip out of the shared plane?
Can the docking station be moved, from day to day, site to site, etc.?
Is the arena indoors?
I have become particularly fond of using cameras to interface with
the real world. Of course, it requires a bit more horsepower but
seems to be able to overcome all of the issues that have crept up...
piglet <erichpwagner@hotmail.com> wrote:
john larkin <JL@gct.com> wrote:
On Sun, 27 Oct 2024 02:19:14 +0200, Klaus Vestergaard Kragelund
<klauskvik@hotmail.com> wrote:
Hi
I am working on an IR detector that will guide a robot into a docking
station.
A IR transmitter on the docking station transmits a beam, and 2 IR
detectors on the robot detects the beam and lets the robot navigate
towards the target. The working distance is a couple of meters.
I need it to be insensitive to ambient light/sunlight.
The IR detectors are placed in a tube, to narrow in the beam angle and >>>> to avoid sunlight (since it is seldom the sun is actually that low in
the horizon)
The IR transmitter will be modulated with 10kHz (TBD) frequency, low
duty cycle. Low duty cycle to be able to drive the LED with high
current, frequency modulated so that the receiver can ignore the effect >>>> of daylight (DC)
If the LED on the docking station has higher radiant intensity at the
point of the robot (2 meters away) than possible IR from sunlight, then >>>> that would be perfect.
Example of transmitter:
https://www.vishay.com/docs/83398/vsmy2850.pdf
Has up to 1000mW/sr. Seems my basic calculation for a 15 degree beam,
shows less than 10nW/m2, while sunlight has 1W/m2. So driving a beam
that has higher output than sunlight seems unlikely.
I would use a IR phototransistor at 850nm, something like this:
https://www.ttelectronics.com/TTElectronics/media/ProductFiles/Datashee >>>> t/OP505-506-535-705.pdf
Or a photo diode:
https://docs.rs-online.com/9f58/0900766b816d8a09.pdf
Fed from reverse 3.3V and into a transimpedance amplifier to boost the >>>> signal with bandpass filter.
One can get digital IR detector used in a remote control systems:
https://www.vishay.com/docs/82491/tsop382.pdf
It has AGC, but digital output. I need analog output to be able to zero >>>> in on the transmitter beam.
I have been looking for IR detectors that has the analog output, not
just the digital, but have not found any.
If the photodiode detector is subjected to sunlight, I am guessing I
would need very high gain on the 10kHz modulation frequency to pick up >>>> the burried signal in the DC from sunlight.
How do I best bias the photo diode for optimum detection of the 10kHz
signal while being immune to the ambient sunlight?
I have chosen 850nm which seems to be a good wavelength. The spectrum at >>>> sea level has some dips due to water absorption.
https://sciencetech-inc.com/web/image/49169/Spectrum%20with_out%20absor >>>> ption.png
Seems like 750nm would be better, since then the IR from the sun is
lower, but does reduced the effective range of the system during
fog/rain. Probably that's why these system do not use 750nm
Other considerations?
You could drive the LED with a square wave, 10 KHz or whatever. The
photodiode could have +DC on one end and the other end can hit a
parallel LC to ground, resonant at 10K.
That takes out the sunlight DC component and adds bandpass filtering.
Just don't fry the photodiode in high light.
An optical bandpass filter would hugely improve things, take out most
of the sunlight.
Yes, the classic solution was to operate PD into an inductor so DC didn’t
overload.
Go one step further and make the indusctor part of a parallel resonant circuit tuned to the modulation frequency.
On 27-10-2024 13:40, Klaus Vestergaard Kragelund wrote:
On 27-10-2024 13:26, Klaus Vestergaard Kragelund wrote:
On 27-10-2024 03:26, john larkin wrote:
On Sun, 27 Oct 2024 02:19:14 +0200, Klaus Vestergaard Kragelund
<klauskvik@hotmail.com> wrote:
Hi
I am working on an IR detector that will guide a robot into a docking >>>>> station.
A IR transmitter on the docking station transmits a beam, and 2 IR
detectors on the robot detects the beam and lets the robot navigate
towards the target. The working distance is a couple of meters.
I need it to be insensitive to ambient light/sunlight.
The IR detectors are placed in a tube, to narrow in the beam angle and >>>>> to avoid sunlight (since it is seldom the sun is actually that low in >>>>> the horizon)
The IR transmitter will be modulated with 10kHz (TBD) frequency, low >>>>> duty cycle. Low duty cycle to be able to drive the LED with high
current, frequency modulated so that the receiver can ignore the effect >>>>> of daylight (DC)
If the LED on the docking station has higher radiant intensity at the >>>>> point of the robot (2 meters away) than possible IR from sunlight, then >>>>> that would be perfect.
Example of transmitter:
https://www.vishay.com/docs/83398/vsmy2850.pdf
Has up to 1000mW/sr. Seems my basic calculation for a 15 degree beam, >>>>> shows less than 10nW/m2, while sunlight has 1W/m2. So driving a beam >>>>> that has higher output than sunlight seems unlikely.
I would use a IR phototransistor at 850nm, something like this:
https://www.ttelectronics.com/TTElectronics/media/ProductFiles/
Datasheet/OP505-506-535-705.pdf
Or a photo diode:
https://docs.rs-online.com/9f58/0900766b816d8a09.pdf
Fed from reverse 3.3V and into a transimpedance amplifier to boost the >>>>> signal with bandpass filter.
One can get digital IR detector used in a remote control systems:
https://www.vishay.com/docs/82491/tsop382.pdf
It has AGC, but digital output. I need analog output to be able to zero >>>>> in on the transmitter beam.
I have been looking for IR detectors that has the analog output, not >>>>> just the digital, but have not found any.
If the photodiode detector is subjected to sunlight, I am guessing I >>>>> would need very high gain on the 10kHz modulation frequency to pick up >>>>> the burried signal in the DC from sunlight.
How do I best bias the photo diode for optimum detection of the 10kHz >>>>> signal while being immune to the ambient sunlight?
I have chosen 850nm which seems to be a good wavelength. The
spectrum at
sea level has some dips due to water absorption.
https://sciencetech-inc.com/web/image/49169/
Spectrum%20with_out%20absorption.png
Seems like 750nm would be better, since then the IR from the sun is
lower, but does reduced the effective range of the system during
fog/rain. Probably that's why these system do not use 750nm
Other considerations?
You could drive the LED with a square wave, 10 KHz or whatever. The
photodiode could have +DC on one end and the other end can hit a
parallel LC to ground, resonant at 10K.
That takes out the sunlight DC component and adds bandpass filtering.
That's a very nice idea. The Q should not matter much, just as long as
DC is removed.
The photodiode will still be subjected to the high ambient light, but
the gain would be close to zero for the stage after. I would then
still need to be sure the photodiode is never saturated by ambient light.
Actually, wont a simple high pass filter work equally well?
Photo diode with bias -> capacitor to gain block....
Like this:
https://electronics.stackexchange.com/questions/416184/how-does-this-op-amp-photodiode-circuit-behave
On 27-10-2024 03:05, Phil Hobbs wrote:
Klaus Vestergaard Kragelund <klauskvik@hotmail.com> wrote:
Hi
I am working on an IR detector that will guide a robot into a docking
station.
A IR transmitter on the docking station transmits a beam, and 2 IR
detectors on the robot detects the beam and lets the robot navigate
towards the target. The working distance is a couple of meters.
I need it to be insensitive to ambient light/sunlight.
The IR detectors are placed in a tube, to narrow in the beam angle and
to avoid sunlight (since it is seldom the sun is actually that low in
the horizon)
The IR transmitter will be modulated with 10kHz (TBD) frequency, low
duty cycle. Low duty cycle to be able to drive the LED with high
current, frequency modulated so that the receiver can ignore the effect
of daylight (DC)
If the LED on the docking station has higher radiant intensity at the
point of the robot (2 meters away) than possible IR from sunlight, then
that would be perfect.
Example of transmitter:
https://www.vishay.com/docs/83398/vsmy2850.pdf
Has up to 1000mW/sr. Seems my basic calculation for a 15 degree beam,
shows less than 10nW/m2, while sunlight has 1W/m2. So driving a beam
that has higher output than sunlight seems unlikely.
I would use a IR phototransistor at 850nm, something like this:
https://www.ttelectronics.com/TTElectronics/media/ProductFiles/Datasheet/OP505-506-535-705.pdf
Or a photo diode:
https://docs.rs-online.com/9f58/0900766b816d8a09.pdf
Fed from reverse 3.3V and into a transimpedance amplifier to boost the
signal with bandpass filter.
One can get digital IR detector used in a remote control systems:
https://www.vishay.com/docs/82491/tsop382.pdf
It has AGC, but digital output. I need analog output to be able to zero
in on the transmitter beam.
I have been looking for IR detectors that has the analog output, not
just the digital, but have not found any.
If the photodiode detector is subjected to sunlight, I am guessing I
would need very high gain on the 10kHz modulation frequency to pick up
the burried signal in the DC from sunlight.
How do I best bias the photo diode for optimum detection of the 10kHz
signal while being immune to the ambient sunlight?
I have chosen 850nm which seems to be a good wavelength. The spectrum at >>> sea level has some dips due to water absorption.
https://sciencetech-inc.com/web/image/49169/Spectrum%20with_out%20absorption.png
Seems like 750nm would be better, since then the IR from the sun is
lower, but does reduced the effective range of the system during
fog/rain. Probably that's why these system do not use 750nm
Other considerations?
Phototransistors are horrible for that sort of job— too small, too noisy,
not repeatable, for a start.
It’s not signal/background you care about, it’s signal/noise, specifically >> the shot noise of the sunlight.
An optical filter will help reject sunlight, and a bigger detector will
help more. The real win is reducing the FOV with lenses as well as baffles, >> tubes, and so on.
I have tried to search for optical filters. Where would one get those?
Baffles and tubes, we can do ourselves, any guideline on the best
surface of the inner tube?
Check out the Hamamatsu S6968–super good medicine.
Looks like a very big die. Is that the main reason to use that one, to
get better sensitivity?
On a sunny day (Sun, 27 Oct 2024 02:19:14 +0200) it happened Klaus Vestergaard >Kragelund <klauskvik@hotmail.com> wrote in <vfk0u0$3u9en$1@dont-email.me>:
Hi
I am working on an IR detector that will guide a robot into a docking >>station.
A IR transmitter on the docking station transmits a beam, and 2 IR >>detectors on the robot detects the beam and lets the robot navigate
towards the target. The working distance is a couple of meters.
I need it to be insensitive to ambient light/sunlight.
I use a cheap camera module to track a light source in H and V direction, and just a simple Microchip PIC : for processing
It can, with some added code, track object forms too, like a cross or maybe a big character.
panteltje.nl/pub/horizontal_IR_target_tracking_4686.avi
those camara modulea are IR sensitive to some extend, sometimes you can remove the IR filter from such modules.
It may be a bit of overkill for your application, but OTOH it can do a lot more.
Mainly designed to detect and follow jet exhaust..
You could uee utrasonics too, maybe even simpler, no sun problem, like a bat. >Cheap electret mikes? or modify some ebay 1 dolalr distance sensors...
can be used for anti-collision too.
On 27-10-2024 14:05, Don Y wrote:
On 10/26/2024 5:19 PM, Klaus Vestergaard Kragelund wrote:
I am working on an IR detector that will guide a robot into a docking station.
A IR transmitter on the docking station transmits a beam, and 2 IR detectors
on the robot detects the beam and lets the robot navigate towards the
target. The working distance is a couple of meters.
Can the robot ALWAYS see the docking station? What happens if an
obstacle (wall?) comes between the two?
Yes, we have RTK GPS to position it within a cm at a location right in front of
the docking, 2 meters away.
Can either device (robot/dock) ever slip out of the shared plane?
No, should be locked
Can the docking station be moved, from day to day, site to site, etc.?
That is fixed
Is the arena indoors?
Outdoors
I have become particularly fond of using cameras to interface with
the real world. Of course, it requires a bit more horsepower but
seems to be able to overcome all of the issues that have crept up...
That's also a solution we have been working on. The Worx Vision uses that
https://eu.worx.com/da-dk/landroid/vision-technology/
That is for a future version. Cameras can also be blinded, lenses needs to be cleaned etc
On Sun, 27 Oct 2024 13:42:27 +0100, Klaus Vestergaard Kragelund ><klauskvik@hotmail.com> wrote:
On 27-10-2024 13:40, Klaus Vestergaard Kragelund wrote:
On 27-10-2024 13:26, Klaus Vestergaard Kragelund wrote:
On 27-10-2024 03:26, john larkin wrote:
On Sun, 27 Oct 2024 02:19:14 +0200, Klaus Vestergaard Kragelund
<klauskvik@hotmail.com> wrote:
Hi
I am working on an IR detector that will guide a robot into a docking >>>>>> station.
A IR transmitter on the docking station transmits a beam, and 2 IR >>>>>> detectors on the robot detects the beam and lets the robot navigate >>>>>> towards the target. The working distance is a couple of meters.
I need it to be insensitive to ambient light/sunlight.
The IR detectors are placed in a tube, to narrow in the beam angle and >>>>>> to avoid sunlight (since it is seldom the sun is actually that low in >>>>>> the horizon)
The IR transmitter will be modulated with 10kHz (TBD) frequency, low >>>>>> duty cycle. Low duty cycle to be able to drive the LED with high
current, frequency modulated so that the receiver can ignore the effect >>>>>> of daylight (DC)
If the LED on the docking station has higher radiant intensity at the >>>>>> point of the robot (2 meters away) than possible IR from sunlight, then >>>>>> that would be perfect.
Example of transmitter:
https://www.vishay.com/docs/83398/vsmy2850.pdf
Has up to 1000mW/sr. Seems my basic calculation for a 15 degree beam, >>>>>> shows less than 10nW/m2, while sunlight has 1W/m2. So driving a beam >>>>>> that has higher output than sunlight seems unlikely.
I would use a IR phototransistor at 850nm, something like this:
https://www.ttelectronics.com/TTElectronics/media/ProductFiles/
Datasheet/OP505-506-535-705.pdf
Or a photo diode:
https://docs.rs-online.com/9f58/0900766b816d8a09.pdf
Fed from reverse 3.3V and into a transimpedance amplifier to boost the >>>>>> signal with bandpass filter.
One can get digital IR detector used in a remote control systems:
https://www.vishay.com/docs/82491/tsop382.pdf
It has AGC, but digital output. I need analog output to be able to zero >>>>>> in on the transmitter beam.
I have been looking for IR detectors that has the analog output, not >>>>>> just the digital, but have not found any.
If the photodiode detector is subjected to sunlight, I am guessing I >>>>>> would need very high gain on the 10kHz modulation frequency to pick up >>>>>> the burried signal in the DC from sunlight.
How do I best bias the photo diode for optimum detection of the 10kHz >>>>>> signal while being immune to the ambient sunlight?
I have chosen 850nm which seems to be a good wavelength. The
spectrum at
sea level has some dips due to water absorption.
https://sciencetech-inc.com/web/image/49169/
Spectrum%20with_out%20absorption.png
Seems like 750nm would be better, since then the IR from the sun is >>>>>> lower, but does reduced the effective range of the system during
fog/rain. Probably that's why these system do not use 750nm
Other considerations?
You could drive the LED with a square wave, 10 KHz or whatever. The
photodiode could have +DC on one end and the other end can hit a
parallel LC to ground, resonant at 10K.
That takes out the sunlight DC component and adds bandpass filtering. >>>>>
That's a very nice idea. The Q should not matter much, just as long as >>>> DC is removed.
The photodiode will still be subjected to the high ambient light, but
the gain would be close to zero for the stage after. I would then
still need to be sure the photodiode is never saturated by ambient light.
A photodiode won't saturate as long as it has a few volts of DC across
it. It might melt if there's no current limiting.
Actually, wont a simple high pass filter work equally well?
Photo diode with bias -> capacitor to gain block....
Like this:
https://electronics.stackexchange.com/questions/416184/how-does-this-op-amp-photodiode-circuit-behave
The LC tank combines background light rejection and bandpass filtering
and has high signal gain, with two parts.
I think there are photodiodes with colored plastic, essentially a
cheap optical bandpass filter. Used in TV remote receivers.
The windows in TVs may be optical bandpass filters too. They work with
very little signal from the remote, in high room light.
On Sun, 27 Oct 2024 09:03:20 GMT, Jan Panteltje <alien@comet.invalid>
wrote:
On a sunny day (Sun, 27 Oct 2024 02:19:14 +0200) it happened Klaus >Vestergaard Kragelund <klauskvik@hotmail.com> wrote in ><vfk0u0$3u9en$1@dont-email.me>:
Hi
I am working on an IR detector that will guide a robot into a docking >>station.
A IR transmitter on the docking station transmits a beam, and 2 IR >>detectors on the robot detects the beam and lets the robot navigate >>towards the target. The working distance is a couple of meters.
I need it to be insensitive to ambient light/sunlight.
I use a cheap camera module to track a light source in H and V direction, >and just a simple Microchip PIC : for processing It can, with some added >code, track object forms too, like a cross or maybe a big character. >panteltje.nl/pub/horizontal_IR_target_tracking_4686.avi those camara >modulea are IR sensitive to some extend, sometimes you can remove the IR >filter from such modules. It may be a bit of overkill for your
application, but OTOH it can do a lot more. Mainly designed to detect and >follow jet exhaust.. You could uee utrasonics too, maybe even simpler, no >sun problem, like a bat. Cheap electret mikes? or modify some ebay 1
dolalr distance sensors... can be used for anti-collision too.
Right. A sonic scheme could measure the phase between two mikes to
determine the direction of the source with high resolution. That could
be an analog multiplier or a bit of code. The amplitudes would be
useful too.
One could compute direction, distance, and velocity almost for free.
No problem with sunlight!
On 27-10-2024 13:26, Klaus Vestergaard Kragelund wrote:
On 27-10-2024 03:26, john larkin wrote:Actually, wont a simple high pass filter work equally well?
On Sun, 27 Oct 2024 02:19:14 +0200, Klaus Vestergaard Kragelund
<klauskvik@hotmail.com> wrote:
Hi
I am working on an IR detector that will guide a robot into a docking
station.
A IR transmitter on the docking station transmits a beam, and 2 IR
detectors on the robot detects the beam and lets the robot navigate
towards the target. The working distance is a couple of meters.
I need it to be insensitive to ambient light/sunlight.
The IR detectors are placed in a tube, to narrow in the beam angle and >>>> to avoid sunlight (since it is seldom the sun is actually that low in
the horizon)
The IR transmitter will be modulated with 10kHz (TBD) frequency, low
duty cycle. Low duty cycle to be able to drive the LED with high
current, frequency modulated so that the receiver can ignore the effect >>>> of daylight (DC)
If the LED on the docking station has higher radiant intensity at the
point of the robot (2 meters away) than possible IR from sunlight, then >>>> that would be perfect.
Example of transmitter:
https://www.vishay.com/docs/83398/vsmy2850.pdf
Has up to 1000mW/sr. Seems my basic calculation for a 15 degree beam,
shows less than 10nW/m2, while sunlight has 1W/m2. So driving a beam
that has higher output than sunlight seems unlikely.
I would use a IR phototransistor at 850nm, something like this:
https://www.ttelectronics.com/TTElectronics/media/ProductFiles/
Datasheet/OP505-506-535-705.pdf
Or a photo diode:
https://docs.rs-online.com/9f58/0900766b816d8a09.pdf
Fed from reverse 3.3V and into a transimpedance amplifier to boost the >>>> signal with bandpass filter.
One can get digital IR detector used in a remote control systems:
https://www.vishay.com/docs/82491/tsop382.pdf
It has AGC, but digital output. I need analog output to be able to zero >>>> in on the transmitter beam.
I have been looking for IR detectors that has the analog output, not
just the digital, but have not found any.
If the photodiode detector is subjected to sunlight, I am guessing I
would need very high gain on the 10kHz modulation frequency to pick up >>>> the burried signal in the DC from sunlight.
How do I best bias the photo diode for optimum detection of the 10kHz
signal while being immune to the ambient sunlight?
I have chosen 850nm which seems to be a good wavelength. The spectrum at >>>> sea level has some dips due to water absorption.
https://sciencetech-inc.com/web/image/49169/
Spectrum%20with_out%20absorption.png
Seems like 750nm would be better, since then the IR from the sun is
lower, but does reduced the effective range of the system during
fog/rain. Probably that's why these system do not use 750nm
Other considerations?
You could drive the LED with a square wave, 10 KHz or whatever. The
photodiode could have +DC on one end and the other end can hit a
parallel LC to ground, resonant at 10K.
That takes out the sunlight DC component and adds bandpass filtering.
That's a very nice idea. The Q should not matter much, just as long as
DC is removed.
The photodiode will still be subjected to the high ambient light, but
the gain would be close to zero for the stage after. I would then still
need to be sure the photodiode is never saturated by ambient light.
Photo diode with bias -> capacitor to gain block....
Klaus Vestergaard Kragelund <klauskvik@hotmail.com> wrote:
On 27-10-2024 13:26, Klaus Vestergaard Kragelund wrote:
On 27-10-2024 03:26, john larkin wrote:Actually, wont a simple high pass filter work equally well?
On Sun, 27 Oct 2024 02:19:14 +0200, Klaus Vestergaard Kragelund
<klauskvik@hotmail.com> wrote:
Hi
I am working on an IR detector that will guide a robot into a docking >>>>> station.
A IR transmitter on the docking station transmits a beam, and 2 IR
detectors on the robot detects the beam and lets the robot navigate
towards the target. The working distance is a couple of meters.
I need it to be insensitive to ambient light/sunlight.
The IR detectors are placed in a tube, to narrow in the beam angle and >>>>> to avoid sunlight (since it is seldom the sun is actually that low in >>>>> the horizon)
The IR transmitter will be modulated with 10kHz (TBD) frequency, low >>>>> duty cycle. Low duty cycle to be able to drive the LED with high
current, frequency modulated so that the receiver can ignore the effect >>>>> of daylight (DC)
If the LED on the docking station has higher radiant intensity at the >>>>> point of the robot (2 meters away) than possible IR from sunlight, then >>>>> that would be perfect.
Example of transmitter:
https://www.vishay.com/docs/83398/vsmy2850.pdf
Has up to 1000mW/sr. Seems my basic calculation for a 15 degree beam, >>>>> shows less than 10nW/m2, while sunlight has 1W/m2. So driving a beam >>>>> that has higher output than sunlight seems unlikely.
I would use a IR phototransistor at 850nm, something like this:
https://www.ttelectronics.com/TTElectronics/media/ProductFiles/
Datasheet/OP505-506-535-705.pdf
Or a photo diode:
https://docs.rs-online.com/9f58/0900766b816d8a09.pdf
Fed from reverse 3.3V and into a transimpedance amplifier to boost the >>>>> signal with bandpass filter.
One can get digital IR detector used in a remote control systems:
https://www.vishay.com/docs/82491/tsop382.pdf
It has AGC, but digital output. I need analog output to be able to zero >>>>> in on the transmitter beam.
I have been looking for IR detectors that has the analog output, not >>>>> just the digital, but have not found any.
If the photodiode detector is subjected to sunlight, I am guessing I >>>>> would need very high gain on the 10kHz modulation frequency to pick up >>>>> the burried signal in the DC from sunlight.
How do I best bias the photo diode for optimum detection of the 10kHz >>>>> signal while being immune to the ambient sunlight?
I have chosen 850nm which seems to be a good wavelength. The spectrum at >>>>> sea level has some dips due to water absorption.
https://sciencetech-inc.com/web/image/49169/
Spectrum%20with_out%20absorption.png
Seems like 750nm would be better, since then the IR from the sun is
lower, but does reduced the effective range of the system during
fog/rain. Probably that's why these system do not use 750nm
Other considerations?
You could drive the LED with a square wave, 10 KHz or whatever. The
photodiode could have +DC on one end and the other end can hit a
parallel LC to ground, resonant at 10K.
That takes out the sunlight DC component and adds bandpass filtering.
That's a very nice idea. The Q should not matter much, just as long as
DC is removed.
The photodiode will still be subjected to the high ambient light, but
the gain would be close to zero for the stage after. I would then still
need to be sure the photodiode is never saturated by ambient light.
Photo diode with bias -> capacitor to gain block....
If you make it part of the bias network yes, a gyrator either a single >transistor or op amp could take the role of inductor.
john larkin <JL@gct.com> wrote:
On Sun, 27 Oct 2024 09:03:20 GMT, Jan Panteltje <alien@comet.invalid>
wrote:
On a sunny day (Sun, 27 Oct 2024 02:19:14 +0200) it happened Klaus
Vestergaard Kragelund <klauskvik@hotmail.com> wrote in
<vfk0u0$3u9en$1@dont-email.me>:
Hi
I am working on an IR detector that will guide a robot into a docking
station.
A IR transmitter on the docking station transmits a beam, and 2 IR
detectors on the robot detects the beam and lets the robot navigate
towards the target. The working distance is a couple of meters.
I need it to be insensitive to ambient light/sunlight.
I use a cheap camera module to track a light source in H and V direction, >> >and just a simple Microchip PIC : for processing It can, with some added
code, track object forms too, like a cross or maybe a big character.
panteltje.nl/pub/horizontal_IR_target_tracking_4686.avi those camara
modulea are IR sensitive to some extend, sometimes you can remove the IR
filter from such modules. It may be a bit of overkill for your
application, but OTOH it can do a lot more. Mainly designed to detect and >> >follow jet exhaust.. You could uee utrasonics too, maybe even simpler, no >> >sun problem, like a bat. Cheap electret mikes? or modify some ebay 1
dolalr distance sensors... can be used for anti-collision too.
Right. A sonic scheme could measure the phase between two mikes to
determine the direction of the source with high resolution. That could
be an analog multiplier or a bit of code. The amplitudes would be
useful too.
One could compute direction, distance, and velocity almost for free.
No problem with sunlight!
Terrible problems with acoustic reflections.
On Sun, 27 Oct 2024 13:42:27 +0100, Klaus Vestergaard Kragelund <klauskvik@hotmail.com> wrote:
On 27-10-2024 13:40, Klaus Vestergaard Kragelund wrote:
On 27-10-2024 13:26, Klaus Vestergaard Kragelund wrote:
On 27-10-2024 03:26, john larkin wrote:
On Sun, 27 Oct 2024 02:19:14 +0200, Klaus Vestergaard Kragelund
<klauskvik@hotmail.com> wrote:
Hi
I am working on an IR detector that will guide a robot into a docking >>>>>> station.
A IR transmitter on the docking station transmits a beam, and 2 IR >>>>>> detectors on the robot detects the beam and lets the robot navigate >>>>>> towards the target. The working distance is a couple of meters.
I need it to be insensitive to ambient light/sunlight.
The IR detectors are placed in a tube, to narrow in the beam angle and >>>>>> to avoid sunlight (since it is seldom the sun is actually that low in >>>>>> the horizon)
The IR transmitter will be modulated with 10kHz (TBD) frequency, low >>>>>> duty cycle. Low duty cycle to be able to drive the LED with high
current, frequency modulated so that the receiver can ignore the effect >>>>>> of daylight (DC)
If the LED on the docking station has higher radiant intensity at the >>>>>> point of the robot (2 meters away) than possible IR from sunlight, then >>>>>> that would be perfect.
Example of transmitter:
https://www.vishay.com/docs/83398/vsmy2850.pdf
Has up to 1000mW/sr. Seems my basic calculation for a 15 degree beam, >>>>>> shows less than 10nW/m2, while sunlight has 1W/m2. So driving a beam >>>>>> that has higher output than sunlight seems unlikely.
I would use a IR phototransistor at 850nm, something like this:
https://www.ttelectronics.com/TTElectronics/media/ProductFiles/
Datasheet/OP505-506-535-705.pdf
Or a photo diode:
https://docs.rs-online.com/9f58/0900766b816d8a09.pdf
Fed from reverse 3.3V and into a transimpedance amplifier to boost the >>>>>> signal with bandpass filter.
One can get digital IR detector used in a remote control systems:
https://www.vishay.com/docs/82491/tsop382.pdf
It has AGC, but digital output. I need analog output to be able to zero >>>>>> in on the transmitter beam.
I have been looking for IR detectors that has the analog output, not >>>>>> just the digital, but have not found any.
If the photodiode detector is subjected to sunlight, I am guessing I >>>>>> would need very high gain on the 10kHz modulation frequency to pick up >>>>>> the burried signal in the DC from sunlight.
How do I best bias the photo diode for optimum detection of the 10kHz >>>>>> signal while being immune to the ambient sunlight?
I have chosen 850nm which seems to be a good wavelength. The
spectrum at
sea level has some dips due to water absorption.
https://sciencetech-inc.com/web/image/49169/
Spectrum%20with_out%20absorption.png
Seems like 750nm would be better, since then the IR from the sun is >>>>>> lower, but does reduced the effective range of the system during
fog/rain. Probably that's why these system do not use 750nm
Other considerations?
You could drive the LED with a square wave, 10 KHz or whatever. The
photodiode could have +DC on one end and the other end can hit a
parallel LC to ground, resonant at 10K.
That takes out the sunlight DC component and adds bandpass filtering. >>>>>
That's a very nice idea. The Q should not matter much, just as long as >>>> DC is removed.
The photodiode will still be subjected to the high ambient light, but
the gain would be close to zero for the stage after. I would then
still need to be sure the photodiode is never saturated by ambient light.
A photodiode won't saturate as long as it has a few volts of DC across
it. It might melt if there's no current limiting.
Actually, wont a simple high pass filter work equally well?
Photo diode with bias -> capacitor to gain block....
Like this:
https://electronics.stackexchange.com/questions/416184/how-does-this-op-amp-photodiode-circuit-behave
The LC tank combines background light rejection and bandpass filtering
and has high signal gain, with two parts.
I think there are photodiodes with colored plastic, essentially a
cheap optical bandpass filter. Used in TV remote receivers.
The windows in TVs may be optical bandpass filters too. They work with
very little signal from the remote, in high room light.
On Sun, 27 Oct 2024 10:49:27 -0700, john larkin <JL@gct.com> wrote:
On Sun, 27 Oct 2024 13:42:27 +0100, Klaus Vestergaard Kragelund
<klauskvik@hotmail.com> wrote:
On 27-10-2024 13:40, Klaus Vestergaard Kragelund wrote:A photodiode won't saturate as long as it has a few volts of DC across
On 27-10-2024 13:26, Klaus Vestergaard Kragelund wrote:
On 27-10-2024 03:26, john larkin wrote:
On Sun, 27 Oct 2024 02:19:14 +0200, Klaus Vestergaard Kragelund
<klauskvik@hotmail.com> wrote:
Hi
I am working on an IR detector that will guide a robot into a docking >>>>>>> station.
A IR transmitter on the docking station transmits a beam, and 2 IR >>>>>>> detectors on the robot detects the beam and lets the robot navigate >>>>>>> towards the target. The working distance is a couple of meters.
I need it to be insensitive to ambient light/sunlight.
The IR detectors are placed in a tube, to narrow in the beam angle and >>>>>>> to avoid sunlight (since it is seldom the sun is actually that low in >>>>>>> the horizon)
The IR transmitter will be modulated with 10kHz (TBD) frequency, low >>>>>>> duty cycle. Low duty cycle to be able to drive the LED with high >>>>>>> current, frequency modulated so that the receiver can ignore the effect >>>>>>> of daylight (DC)
If the LED on the docking station has higher radiant intensity at the >>>>>>> point of the robot (2 meters away) than possible IR from sunlight, then >>>>>>> that would be perfect.
Example of transmitter:
https://www.vishay.com/docs/83398/vsmy2850.pdf
Has up to 1000mW/sr. Seems my basic calculation for a 15 degree beam, >>>>>>> shows less than 10nW/m2, while sunlight has 1W/m2. So driving a beam >>>>>>> that has higher output than sunlight seems unlikely.
I would use a IR phototransistor at 850nm, something like this:
https://www.ttelectronics.com/TTElectronics/media/ProductFiles/
Datasheet/OP505-506-535-705.pdf
Or a photo diode:
https://docs.rs-online.com/9f58/0900766b816d8a09.pdf
Fed from reverse 3.3V and into a transimpedance amplifier to boost the >>>>>>> signal with bandpass filter.
One can get digital IR detector used in a remote control systems: >>>>>>>
https://www.vishay.com/docs/82491/tsop382.pdf
It has AGC, but digital output. I need analog output to be able to zero >>>>>>> in on the transmitter beam.
I have been looking for IR detectors that has the analog output, not >>>>>>> just the digital, but have not found any.
If the photodiode detector is subjected to sunlight, I am guessing I >>>>>>> would need very high gain on the 10kHz modulation frequency to pick up >>>>>>> the burried signal in the DC from sunlight.
How do I best bias the photo diode for optimum detection of the 10kHz >>>>>>> signal while being immune to the ambient sunlight?
I have chosen 850nm which seems to be a good wavelength. The
spectrum at
sea level has some dips due to water absorption.
https://sciencetech-inc.com/web/image/49169/
Spectrum%20with_out%20absorption.png
Seems like 750nm would be better, since then the IR from the sun is >>>>>>> lower, but does reduced the effective range of the system during >>>>>>> fog/rain. Probably that's why these system do not use 750nm
Other considerations?
You could drive the LED with a square wave, 10 KHz or whatever. The >>>>>> photodiode could have +DC on one end and the other end can hit a
parallel LC to ground, resonant at 10K.
That takes out the sunlight DC component and adds bandpass filtering. >>>>>>
That's a very nice idea. The Q should not matter much, just as long as >>>>> DC is removed.
The photodiode will still be subjected to the high ambient light, but >>>>> the gain would be close to zero for the stage after. I would then
still need to be sure the photodiode is never saturated by ambient light. >>
it. It might melt if there's no current limiting.
Actually, wont a simple high pass filter work equally well?
Photo diode with bias -> capacitor to gain block....
Like this:
https://electronics.stackexchange.com/questions/416184/how-does-this-op-amp-photodiode-circuit-behave
The LC tank combines background light rejection and bandpass filtering
and has high signal gain, with two parts.
I think there are photodiodes with colored plastic, essentially a
cheap optical bandpass filter. Used in TV remote receivers.
The windows in TVs may be optical bandpass filters too. They work with
very little signal from the remote, in high room light.
To this I would add a trick. We know something very useful about the
10 KHz modulation, its exact frequency, given that it is (or can be) generated electronically, and thus its frequency is ultimately
controlled by a logic-clock crystal oscillator.
So feed the amplified signal from the 10 KHz LC tank to a I+Q homodyne circuit, filter to pass signals from DC to a 10 Hz and compute the
magnitude of the received signal - this is used for figuring out the direction to the docking station.
The phase of the received signal is discarded, as it is effectively
random because the TX oscillator phase with respect to the RX
oscillator phases is uncontrolled and unknown.
The advantage over a high-Q LC tank is that the resonant frequency of
the tank need not be that precise.
On Sun, 27 Oct 2024 09:03:20 GMT, Jan Panteltje <alien@comet.invalid>
wrote:
On a sunny day (Sun, 27 Oct 2024 02:19:14 +0200) it happened Klaus Vestergaard
Kragelund <klauskvik@hotmail.com> wrote in <vfk0u0$3u9en$1@dont-email.me>: >>
Hi
I am working on an IR detector that will guide a robot into a docking
station.
A IR transmitter on the docking station transmits a beam, and 2 IR
detectors on the robot detects the beam and lets the robot navigate
towards the target. The working distance is a couple of meters.
I need it to be insensitive to ambient light/sunlight.
I use a cheap camera module to track a light source in H and V direction, and just a simple Microchip PIC : for processing
It can, with some added code, track object forms too, like a cross or maybe a big character.
panteltje.nl/pub/horizontal_IR_target_tracking_4686.avi
those camara modulea are IR sensitive to some extend, sometimes you can remove the IR filter from such modules.
It may be a bit of overkill for your application, but OTOH it can do a lot more.
Mainly designed to detect and follow jet exhaust..
You could uee utrasonics too, maybe even simpler, no sun problem, like a bat.
Cheap electret mikes? or modify some ebay 1 dolalr distance sensors...
can be used for anti-collision too.
Right. A sonic scheme could measure the phase between two mikes to
determine the direction of the source with high resolution. That could
be an analog multiplier or a bit of code. The amplitudes would be
useful too.
One could compute direction, distance, and velocity almost for free.
No problem with sunlight!
On 10/27/2024 7:33 AM, Klaus Vestergaard Kragelund wrote:
On 27-10-2024 14:05, Don Y wrote:
On 10/26/2024 5:19 PM, Klaus Vestergaard Kragelund wrote:
I am working on an IR detector that will guide a robot into a
docking station.
A IR transmitter on the docking station transmits a beam, and 2 IR
detectors on the robot detects the beam and lets the robot navigate
towards the target. The working distance is a couple of meters.
Can the robot ALWAYS see the docking station? What happens if an
obstacle (wall?) comes between the two?
Yes, we have RTK GPS to position it within a cm at a location right in
front of the docking, 2 meters away.
Then why can't you move to the GPS location of the dock with the
same degree of accuracy?
Can either device (robot/dock) ever slip out of the shared plane?
No, should be locked
"Outdoors" (from below). Presumably on pavement/concrete (not a "lawn") that wouldn't have dips and bumps?
Can the docking station be moved, from day to day, site to site, etc.?
That is fixed
Is the arena indoors?
Outdoors
I have become particularly fond of using cameras to interface with
the real world. Of course, it requires a bit more horsepower but
seems to be able to overcome all of the issues that have crept up...
That's also a solution we have been working on. The Worx Vision uses that
https://eu.worx.com/da-dk/landroid/vision-technology/
That is for a future version. Cameras can also be blinded, lenses
needs to be cleaned etc
Yes, but a camera can be "queried" to verify that it is functioning correctly: "What do you see? Is it THIS?"
I test my cameras by storing previously viewed scenes to verify they
are still "reasonably" intact. Ideally, I would move something into
the field of view but that requires additional capabilities.
You, however, could move the robot (assuming IT has the eyes) and
verify that the scene changes accordingly.
A IR transmitter on the docking station transmits a beam, and 2 IR
detectors on the robot detects the beam and lets the robot navigate
towards the target. The working distance is a couple of meters.
Can the robot ALWAYS see the docking station? What happens if an
obstacle (wall?) comes between the two?
Yes, we have RTK GPS to position it within a cm at a location right in front
of the docking, 2 meters away.
Then why can't you move to the GPS location of the dock with the
same degree of accuracy?
The docking station is typically in a shed, or close to a building where the GPS signal disappears.
Can either device (robot/dock) ever slip out of the shared plane?
No, should be locked
"Outdoors" (from below). Presumably on pavement/concrete (not a "lawn")
that wouldn't have dips and bumps?
It's moving on grass, and can have bumps etc, so for IR the lope needs to be perhaps 20degrees to avoid loss of signal
I have become particularly fond of using cameras to interface with
the real world. Of course, it requires a bit more horsepower but
seems to be able to overcome all of the issues that have crept up...
That's also a solution we have been working on. The Worx Vision uses that >>>
https://eu.worx.com/da-dk/landroid/vision-technology/
That is for a future version. Cameras can also be blinded, lenses needs to >>> be cleaned etc
Yes, but a camera can be "queried" to verify that it is functioning
correctly: "What do you see? Is it THIS?"
I test my cameras by storing previously viewed scenes to verify they
are still "reasonably" intact. Ideally, I would move something into
the field of view but that requires additional capabilities.
You, however, could move the robot (assuming IT has the eyes) and
verify that the scene changes accordingly.
Could be done. The guys in charge are worried with change of environment, so what happens when it snows heavily, fog or other surroundings changing effects.
On 27-10-2024 20:06, Don Y wrote:
On 10/27/2024 7:33 AM, Klaus Vestergaard Kragelund wrote:
On 27-10-2024 14:05, Don Y wrote:
On 10/26/2024 5:19 PM, Klaus Vestergaard Kragelund wrote:
I am working on an IR detector that will guide a robot into a
docking station.
A IR transmitter on the docking station transmits a beam, and 2 IR
detectors on the robot detects the beam and lets the robot navigate
towards the target. The working distance is a couple of meters.
Can the robot ALWAYS see the docking station? What happens if an
obstacle (wall?) comes between the two?
Yes, we have RTK GPS to position it within a cm at a location right in
front of the docking, 2 meters away.
Then why can't you move to the GPS location of the dock with the
same degree of accuracy?
The docking station is typically in a shed, or close to a building where
the GPS signal disappears.
Can either device (robot/dock) ever slip out of the shared plane?
No, should be locked
"Outdoors" (from below). Presumably on pavement/concrete (not a "lawn")
that wouldn't have dips and bumps?
It's moving on grass, and can have bumps etc, so for IR the lope needs
to be perhaps 20degrees to avoid loss of signal
Can the docking station be moved, from day to day, site to site, etc.?
That is fixed
Is the arena indoors?
Outdoors
I have become particularly fond of using cameras to interface with
the real world. Of course, it requires a bit more horsepower but
seems to be able to overcome all of the issues that have crept up...
That's also a solution we have been working on. The Worx Vision uses that >>>
https://eu.worx.com/da-dk/landroid/vision-technology/
That is for a future version. Cameras can also be blinded, lenses
needs to be cleaned etc
Yes, but a camera can be "queried" to verify that it is functioning
correctly: "What do you see? Is it THIS?"
I test my cameras by storing previously viewed scenes to verify they
are still "reasonably" intact. Ideally, I would move something into
the field of view but that requires additional capabilities.
You, however, could move the robot (assuming IT has the eyes) and
verify that the scene changes accordingly.
Could be done. The guys in charge are worried with change of
environment, so what happens when it snows heavily, fog or other
surroundings changing effects.
On Sun, 27 Oct 2024 22:59:59 -0000 (UTC), piglet
<erichpwagner@hotmail.com> wrote:
Klaus Vestergaard Kragelund <klauskvik@hotmail.com> wrote:
On 27-10-2024 13:26, Klaus Vestergaard Kragelund wrote:
On 27-10-2024 03:26, john larkin wrote:Actually, wont a simple high pass filter work equally well?
On Sun, 27 Oct 2024 02:19:14 +0200, Klaus Vestergaard Kragelund
<klauskvik@hotmail.com> wrote:
Hi
I am working on an IR detector that will guide a robot into a docking >>>>>> station.
A IR transmitter on the docking station transmits a beam, and 2 IR >>>>>> detectors on the robot detects the beam and lets the robot navigate >>>>>> towards the target. The working distance is a couple of meters.
I need it to be insensitive to ambient light/sunlight.
The IR detectors are placed in a tube, to narrow in the beam angle and >>>>>> to avoid sunlight (since it is seldom the sun is actually that low in >>>>>> the horizon)
The IR transmitter will be modulated with 10kHz (TBD) frequency, low >>>>>> duty cycle. Low duty cycle to be able to drive the LED with high
current, frequency modulated so that the receiver can ignore the effect >>>>>> of daylight (DC)
If the LED on the docking station has higher radiant intensity at the >>>>>> point of the robot (2 meters away) than possible IR from sunlight, then >>>>>> that would be perfect.
Example of transmitter:
https://www.vishay.com/docs/83398/vsmy2850.pdf
Has up to 1000mW/sr. Seems my basic calculation for a 15 degree beam, >>>>>> shows less than 10nW/m2, while sunlight has 1W/m2. So driving a beam >>>>>> that has higher output than sunlight seems unlikely.
I would use a IR phototransistor at 850nm, something like this:
https://www.ttelectronics.com/TTElectronics/media/ProductFiles/
Datasheet/OP505-506-535-705.pdf
Or a photo diode:
https://docs.rs-online.com/9f58/0900766b816d8a09.pdf
Fed from reverse 3.3V and into a transimpedance amplifier to boost the >>>>>> signal with bandpass filter.
One can get digital IR detector used in a remote control systems:
https://www.vishay.com/docs/82491/tsop382.pdf
It has AGC, but digital output. I need analog output to be able to zero >>>>>> in on the transmitter beam.
I have been looking for IR detectors that has the analog output, not >>>>>> just the digital, but have not found any.
If the photodiode detector is subjected to sunlight, I am guessing I >>>>>> would need very high gain on the 10kHz modulation frequency to pick up >>>>>> the burried signal in the DC from sunlight.
How do I best bias the photo diode for optimum detection of the 10kHz >>>>>> signal while being immune to the ambient sunlight?
I have chosen 850nm which seems to be a good wavelength. The spectrum at >>>>>> sea level has some dips due to water absorption.
https://sciencetech-inc.com/web/image/49169/
Spectrum%20with_out%20absorption.png
Seems like 750nm would be better, since then the IR from the sun is >>>>>> lower, but does reduced the effective range of the system during
fog/rain. Probably that's why these system do not use 750nm
Other considerations?
You could drive the LED with a square wave, 10 KHz or whatever. The
photodiode could have +DC on one end and the other end can hit a
parallel LC to ground, resonant at 10K.
That takes out the sunlight DC component and adds bandpass filtering. >>>>>
That's a very nice idea. The Q should not matter much, just as long as >>>> DC is removed.
The photodiode will still be subjected to the high ambient light, but
the gain would be close to zero for the stage after. I would then still >>>> need to be sure the photodiode is never saturated by ambient light.
Photo diode with bias -> capacitor to gain block....
If you make it part of the bias network yes, a gyrator either a single
transistor or op amp could take the role of inductor.
When you need an inductor, an inductor makes an excellent inductor.
But the dual microphone thing, electret or mems, sounds like a much
better way to go.
E.g., I use them to "watch" the garage door rails (which have a specific shape) to see if any objects have come between the camera and the rails.
(The rails define the plane that the garage door will occupy as
it closes)Â Of course, everything around the rails is highly variable
as garages are notorious for clutter and dynamism.
Hi
I am working on an IR detector that will guide a robot into a docking station.
A IR transmitter on the docking station transmits a beam, and 2 IR
detectors on the robot detects the beam and lets the robot navigate
towards the target. The working distance is a couple of meters.
I need it to be insensitive to ambient light/sunlight.
The IR detectors are placed in a tube, to narrow in the beam angle and
to avoid sunlight (since it is seldom the sun is actually that low in
the horizon)
The IR transmitter will be modulated with 10kHz (TBD) frequency, low
duty cycle. Low duty cycle to be able to drive the LED with high
current, frequency modulated so that the receiver can ignore the effect
of daylight (DC)
john larkin <JL@gct.com> wrote:
On Sun, 27 Oct 2024 22:59:59 -0000 (UTC), piglet
<erichpwagner@hotmail.com> wrote:
Klaus Vestergaard Kragelund <klauskvik@hotmail.com> wrote:
On 27-10-2024 13:26, Klaus Vestergaard Kragelund wrote:
On 27-10-2024 03:26, john larkin wrote:Actually, wont a simple high pass filter work equally well?
On Sun, 27 Oct 2024 02:19:14 +0200, Klaus Vestergaard Kragelund
<klauskvik@hotmail.com> wrote:
Hi
I am working on an IR detector that will guide a robot into a docking >>>>>>> station.
A IR transmitter on the docking station transmits a beam, and 2 IR >>>>>>> detectors on the robot detects the beam and lets the robot navigate >>>>>>> towards the target. The working distance is a couple of meters.
I need it to be insensitive to ambient light/sunlight.
The IR detectors are placed in a tube, to narrow in the beam angle and >>>>>>> to avoid sunlight (since it is seldom the sun is actually that low in >>>>>>> the horizon)
The IR transmitter will be modulated with 10kHz (TBD) frequency, low >>>>>>> duty cycle. Low duty cycle to be able to drive the LED with high >>>>>>> current, frequency modulated so that the receiver can ignore the effect >>>>>>> of daylight (DC)
If the LED on the docking station has higher radiant intensity at the >>>>>>> point of the robot (2 meters away) than possible IR from sunlight, then >>>>>>> that would be perfect.
Example of transmitter:
https://www.vishay.com/docs/83398/vsmy2850.pdf
Has up to 1000mW/sr. Seems my basic calculation for a 15 degree beam, >>>>>>> shows less than 10nW/m2, while sunlight has 1W/m2. So driving a beam >>>>>>> that has higher output than sunlight seems unlikely.
I would use a IR phototransistor at 850nm, something like this:
https://www.ttelectronics.com/TTElectronics/media/ProductFiles/
Datasheet/OP505-506-535-705.pdf
Or a photo diode:
https://docs.rs-online.com/9f58/0900766b816d8a09.pdf
Fed from reverse 3.3V and into a transimpedance amplifier to boost the >>>>>>> signal with bandpass filter.
One can get digital IR detector used in a remote control systems: >>>>>>>
https://www.vishay.com/docs/82491/tsop382.pdf
It has AGC, but digital output. I need analog output to be able to zero >>>>>>> in on the transmitter beam.
I have been looking for IR detectors that has the analog output, not >>>>>>> just the digital, but have not found any.
If the photodiode detector is subjected to sunlight, I am guessing I >>>>>>> would need very high gain on the 10kHz modulation frequency to pick up >>>>>>> the burried signal in the DC from sunlight.
How do I best bias the photo diode for optimum detection of the 10kHz >>>>>>> signal while being immune to the ambient sunlight?
I have chosen 850nm which seems to be a good wavelength. The spectrum at
sea level has some dips due to water absorption.
https://sciencetech-inc.com/web/image/49169/
Spectrum%20with_out%20absorption.png
Seems like 750nm would be better, since then the IR from the sun is >>>>>>> lower, but does reduced the effective range of the system during >>>>>>> fog/rain. Probably that's why these system do not use 750nm
Other considerations?
You could drive the LED with a square wave, 10 KHz or whatever. The >>>>>> photodiode could have +DC on one end and the other end can hit a
parallel LC to ground, resonant at 10K.
That takes out the sunlight DC component and adds bandpass filtering. >>>>>>
That's a very nice idea. The Q should not matter much, just as long as >>>>> DC is removed.
The photodiode will still be subjected to the high ambient light, but >>>>> the gain would be close to zero for the stage after. I would then still >>>>> need to be sure the photodiode is never saturated by ambient light.
Photo diode with bias -> capacitor to gain block....
If you make it part of the bias network yes, a gyrator either a single
transistor or op amp could take the role of inductor.
When you need an inductor, an inductor makes an excellent inductor.
But the dual microphone thing, electret or mems, sounds like a much
better way to go.
Some folk are scared of inductors. 10kHz does mean quite a few milli
henries.
Of course they might be able to reverse the process and have one receiver
on the robot and two emitters on the docking station, a bit like aircraft
VOR
On 27-10-2024 18:56, john larkin wrote:
On Sun, 27 Oct 2024 09:03:20 GMT, Jan Panteltje <alien@comet.invalid>Could also be done with a chirp and auto-correlation, although this does
wrote:
On a sunny day (Sun, 27 Oct 2024 02:19:14 +0200) it happened Klaus Vestergaard
Kragelund <klauskvik@hotmail.com> wrote in <vfk0u0$3u9en$1@dont-email.me>: >>>
Hi
I am working on an IR detector that will guide a robot into a docking
station.
A IR transmitter on the docking station transmits a beam, and 2 IR
detectors on the robot detects the beam and lets the robot navigate
towards the target. The working distance is a couple of meters.
I need it to be insensitive to ambient light/sunlight.
I use a cheap camera module to track a light source in H and V direction, and just a simple Microchip PIC : for processing
It can, with some added code, track object forms too, like a cross or maybe a big character.
panteltje.nl/pub/horizontal_IR_target_tracking_4686.avi
those camara modulea are IR sensitive to some extend, sometimes you can remove the IR filter from such modules.
It may be a bit of overkill for your application, but OTOH it can do a lot more.
Mainly designed to detect and follow jet exhaust..
You could uee utrasonics too, maybe even simpler, no sun problem, like a bat.
Cheap electret mikes? or modify some ebay 1 dolalr distance sensors...
can be used for anti-collision too.
Right. A sonic scheme could measure the phase between two mikes to
determine the direction of the source with high resolution. That could
be an analog multiplier or a bit of code. The amplitudes would be
useful too.
One could compute direction, distance, and velocity almost for free.
No problem with sunlight!
not use the phase, but a beacon reference instead
On 27-10-2024 03:05, Phil Hobbs wrote:
Klaus Vestergaard Kragelund <klauskvik@hotmail.com> wrote:
Hi
I am working on an IR detector that will guide a robot into a docking
station.
A IR transmitter on the docking station transmits a beam, and 2 IR
detectors on the robot detects the beam and lets the robot navigate
towards the target. The working distance is a couple of meters.
I need it to be insensitive to ambient light/sunlight.
The IR detectors are placed in a tube, to narrow in the beam angle and
to avoid sunlight (since it is seldom the sun is actually that low in
the horizon)
The IR transmitter will be modulated with 10kHz (TBD) frequency, low
duty cycle. Low duty cycle to be able to drive the LED with high
current, frequency modulated so that the receiver can ignore the effect
of daylight (DC)
If the LED on the docking station has higher radiant intensity at the
point of the robot (2 meters away) than possible IR from sunlight, then
that would be perfect.
Example of transmitter:
https://www.vishay.com/docs/83398/vsmy2850.pdf
Has up to 1000mW/sr. Seems my basic calculation for a 15 degree beam,
shows less than 10nW/m2, while sunlight has 1W/m2. So driving a beam
that has higher output than sunlight seems unlikely.
I would use a IR phototransistor at 850nm, something like this:
https://www.ttelectronics.com/TTElectronics/media/ProductFiles/Datasheet/OP505-506-535-705.pdf
Or a photo diode:
https://docs.rs-online.com/9f58/0900766b816d8a09.pdf
Fed from reverse 3.3V and into a transimpedance amplifier to boost the
signal with bandpass filter.
One can get digital IR detector used in a remote control systems:
https://www.vishay.com/docs/82491/tsop382.pdf
It has AGC, but digital output. I need analog output to be able to zero
in on the transmitter beam.
I have been looking for IR detectors that has the analog output, not
just the digital, but have not found any.
If the photodiode detector is subjected to sunlight, I am guessing I
would need very high gain on the 10kHz modulation frequency to pick up
the burried signal in the DC from sunlight.
How do I best bias the photo diode for optimum detection of the 10kHz
signal while being immune to the ambient sunlight?
I have chosen 850nm which seems to be a good wavelength. The spectrum at >>> sea level has some dips due to water absorption.
https://sciencetech-inc.com/web/image/49169/Spectrum%20with_out%20absorption.png
Seems like 750nm would be better, since then the IR from the sun is
lower, but does reduced the effective range of the system during
fog/rain. Probably that's why these system do not use 750nm
Other considerations?
Phototransistors are horrible for that sort of job— too small, too noisy, >> not repeatable, for a start.
It’s not signal/background you care about, it’s signal/noise,
specifically
the shot noise of the sunlight.
An optical filter will help reject sunlight, and a bigger detector will
help more. The real win is reducing the FOV with lenses as well as
baffles,
tubes, and so on.
I have tried to search for optical filters. Where would one get those?
Baffles and tubes, we can do ourselves, any guideline on the best
surface of the inner tube?
Check out the Hamamatsu S6968–super good medicine.
Looks like a very big die. Is that the main reason to use that one, to
get better sensitivity?
On 27-10-2024 03:26, john larkin wrote:
On Sun, 27 Oct 2024 02:19:14 +0200, Klaus Vestergaard Kragelund
<klauskvik@hotmail.com> wrote:
Hi
I am working on an IR detector that will guide a robot into a docking
station.
A IR transmitter on the docking station transmits a beam, and 2 IR
detectors on the robot detects the beam and lets the robot navigate
towards the target. The working distance is a couple of meters.
I need it to be insensitive to ambient light/sunlight.
The IR detectors are placed in a tube, to narrow in the beam angle and
to avoid sunlight (since it is seldom the sun is actually that low in
the horizon)
The IR transmitter will be modulated with 10kHz (TBD) frequency, low
duty cycle. Low duty cycle to be able to drive the LED with high
current, frequency modulated so that the receiver can ignore the effect
of daylight (DC)
If the LED on the docking station has higher radiant intensity at the
point of the robot (2 meters away) than possible IR from sunlight, then
that would be perfect.
Example of transmitter:
https://www.vishay.com/docs/83398/vsmy2850.pdf
Has up to 1000mW/sr. Seems my basic calculation for a 15 degree beam,
shows less than 10nW/m2, while sunlight has 1W/m2. So driving a beam
that has higher output than sunlight seems unlikely.
I would use a IR phototransistor at 850nm, something like this:
https://www.ttelectronics.com/TTElectronics/media/ProductFiles/Datasheet/OP505-506-535-705.pdf
Or a photo diode:
https://docs.rs-online.com/9f58/0900766b816d8a09.pdf
Fed from reverse 3.3V and into a transimpedance amplifier to boost the
signal with bandpass filter.
One can get digital IR detector used in a remote control systems:
https://www.vishay.com/docs/82491/tsop382.pdf
It has AGC, but digital output. I need analog output to be able to zero
in on the transmitter beam.
I have been looking for IR detectors that has the analog output, not
just the digital, but have not found any.
If the photodiode detector is subjected to sunlight, I am guessing I
would need very high gain on the 10kHz modulation frequency to pick up
the burried signal in the DC from sunlight.
How do I best bias the photo diode for optimum detection of the 10kHz
signal while being immune to the ambient sunlight?
I have chosen 850nm which seems to be a good wavelength. The spectrum at >>> sea level has some dips due to water absorption.
https://sciencetech-inc.com/web/image/49169/Spectrum%20with_out%20absorption.png
Seems like 750nm would be better, since then the IR from the sun is
lower, but does reduced the effective range of the system during
fog/rain. Probably that's why these system do not use 750nm
Other considerations?
You could drive the LED with a square wave, 10 KHz or whatever. The
photodiode could have +DC on one end and the other end can hit a
parallel LC to ground, resonant at 10K.
That takes out the sunlight DC component and adds bandpass filtering.
That's a very nice idea. The Q should not matter much, just as long as
DC is removed.
The photodiode will still be subjected to the high ambient light, but
the gain would be close to zero for the stage after. I would then still
need to be sure the photodiode is never saturated by ambient light.
Just don't fry the photodiode in high light.
So adding a resistance in series with the diode?
On 2024-10-27 08:26, Klaus Vestergaard Kragelund wrote:
On 27-10-2024 03:26, john larkin wrote:
On Sun, 27 Oct 2024 02:19:14 +0200, Klaus Vestergaard Kragelund
<klauskvik@hotmail.com> wrote:
Hi
I am working on an IR detector that will guide a robot into a docking
station.
A IR transmitter on the docking station transmits a beam, and 2 IR
detectors on the robot detects the beam and lets the robot navigate
towards the target. The working distance is a couple of meters.
I need it to be insensitive to ambient light/sunlight.
The IR detectors are placed in a tube, to narrow in the beam angle and >>>> to avoid sunlight (since it is seldom the sun is actually that low in
the horizon)
The IR transmitter will be modulated with 10kHz (TBD) frequency, low
duty cycle. Low duty cycle to be able to drive the LED with high
current, frequency modulated so that the receiver can ignore the effect >>>> of daylight (DC)
If the LED on the docking station has higher radiant intensity at the
point of the robot (2 meters away) than possible IR from sunlight, then >>>> that would be perfect.
Example of transmitter:
https://www.vishay.com/docs/83398/vsmy2850.pdf
Has up to 1000mW/sr. Seems my basic calculation for a 15 degree beam,
shows less than 10nW/m2, while sunlight has 1W/m2. So driving a beam
that has higher output than sunlight seems unlikely.
I would use a IR phototransistor at 850nm, something like this:
https://www.ttelectronics.com/TTElectronics/media/ProductFiles/Datasheet/OP505-506-535-705.pdf
Or a photo diode:
https://docs.rs-online.com/9f58/0900766b816d8a09.pdf
Fed from reverse 3.3V and into a transimpedance amplifier to boost the >>>> signal with bandpass filter.
One can get digital IR detector used in a remote control systems:
https://www.vishay.com/docs/82491/tsop382.pdf
It has AGC, but digital output. I need analog output to be able to zero >>>> in on the transmitter beam.
I have been looking for IR detectors that has the analog output, not
just the digital, but have not found any.
If the photodiode detector is subjected to sunlight, I am guessing I
would need very high gain on the 10kHz modulation frequency to pick up >>>> the burried signal in the DC from sunlight.
How do I best bias the photo diode for optimum detection of the 10kHz
signal while being immune to the ambient sunlight?
I have chosen 850nm which seems to be a good wavelength. The spectrum at >>>> sea level has some dips due to water absorption.
https://sciencetech-inc.com/web/image/49169/Spectrum%20with_out%20absorption.png
Seems like 750nm would be better, since then the IR from the sun is
lower, but does reduced the effective range of the system during
fog/rain. Probably that's why these system do not use 750nm
Other considerations?
You could drive the LED with a square wave, 10 KHz or whatever. The
photodiode could have +DC on one end and the other end can hit a
parallel LC to ground, resonant at 10K.
That takes out the sunlight DC component and adds bandpass filtering.
That's a very nice idea. The Q should not matter much, just as long as
DC is removed.
The photodiode will still be subjected to the high ambient light, but
the gain would be close to zero for the stage after. I would then still
need to be sure the photodiode is never saturated by ambient light.
Just don't fry the photodiode in high light.
So adding a resistance in series with the diode?
Nah, the Johnson noise kills you. It's easier to just calculate or
measure the photocurrent from direct sunlight and design around that.
You only need enough bias to ensure linear operation at high current,
maybe a volt or so.
You will want to put a filter in the second stage to get rid of the
nasty high-frequency noise peak. I usually use a two-pole Sallen-Key
with equal resistor values, which has predictable gain (1.00) and low >component-value sensitivity, and is super simple.
Resist the temptation to do anything floral with the TIA stage, such as
LC or *especially* gyrator filtering. A large inductor is a disaster in
a TIA, because if it doesn't cause instability, it'll still pick up crap
from every VF motor drive on the block, and deposit it right into the
summing junction, where you really really don't want it.
On 2024-10-27 08:20, Klaus Vestergaard Kragelund wrote:
On 27-10-2024 03:05, Phil Hobbs wrote:
Klaus Vestergaard Kragelund <klauskvik@hotmail.com> wrote:
Hi
I am working on an IR detector that will guide a robot into a docking
station.
A IR transmitter on the docking station transmits a beam, and 2 IR
detectors on the robot detects the beam and lets the robot navigate
towards the target. The working distance is a couple of meters.
I need it to be insensitive to ambient light/sunlight.
The IR detectors are placed in a tube, to narrow in the beam angle and >>>> to avoid sunlight (since it is seldom the sun is actually that low in
the horizon)
The IR transmitter will be modulated with 10kHz (TBD) frequency, low
duty cycle. Low duty cycle to be able to drive the LED with high
current, frequency modulated so that the receiver can ignore the effect >>>> of daylight (DC)
If the LED on the docking station has higher radiant intensity at the
point of the robot (2 meters away) than possible IR from sunlight, then >>>> that would be perfect.
Example of transmitter:
https://www.vishay.com/docs/83398/vsmy2850.pdf
Has up to 1000mW/sr. Seems my basic calculation for a 15 degree beam,
shows less than 10nW/m2, while sunlight has 1W/m2. So driving a beam
that has higher output than sunlight seems unlikely.
I would use a IR phototransistor at 850nm, something like this:
https://www.ttelectronics.com/TTElectronics/media/ProductFiles/
Datasheet/OP505-506-535-705.pdf
Or a photo diode:
https://docs.rs-online.com/9f58/0900766b816d8a09.pdf
Fed from reverse 3.3V and into a transimpedance amplifier to boost the >>>> signal with bandpass filter.
One can get digital IR detector used in a remote control systems:
https://www.vishay.com/docs/82491/tsop382.pdf
It has AGC, but digital output. I need analog output to be able to zero >>>> in on the transmitter beam.
I have been looking for IR detectors that has the analog output, not
just the digital, but have not found any.
If the photodiode detector is subjected to sunlight, I am guessing I
would need very high gain on the 10kHz modulation frequency to pick up >>>> the burried signal in the DC from sunlight.
How do I best bias the photo diode for optimum detection of the 10kHz
signal while being immune to the ambient sunlight?
I have chosen 850nm which seems to be a good wavelength. The
spectrum at
sea level has some dips due to water absorption.
https://sciencetech-inc.com/web/image/49169/
Spectrum%20with_out%20absorption.png
Seems like 750nm would be better, since then the IR from the sun is
lower, but does reduced the effective range of the system during
fog/rain. Probably that's why these system do not use 750nm
Other considerations?
Phototransistors are horrible for that sort of job— too small, too
noisy,
not repeatable, for a start.
It’s not signal/background you care about, it’s signal/noise,
specifically
the shot noise of the sunlight.
An optical filter will help reject sunlight, and a bigger detector will
help more. The real win is reducing the FOV with lenses as well as
baffles,
tubes, and so on.
I have tried to search for optical filters. Where would one get those?
700-nm plastic longpass filter material comes in sheets. You can get smallish chunks of it on the jungle website and various other emporia.
Fancier things, such as narrowish bandpasses and custom wavelengths,
tend to be glass and quite a lot more expensive. I usually get those
from Omega Optical, but there are European suppliers as well.
For this use, a regular 700-nmm plastic longpass will get rid of most of
the daylight, which is what you want. You can also get photodiodes with
the filter material included, e.g. the ever-popular BPW34F.
Baffles and tubes, we can do ourselves, any guideline on the best
surface of the inner tube?
Regular old flat black paint. But a lens on the transmitter will be the biggest win.
Check out the Hamamatsu S6968–super good medicine.
Looks like a very big die. Is that the main reason to use that one, to
get better sensitivity?
It has very low capacitance for its area, it has a lens to increase the detection area, and (crucially for my uses, which are generally at
higher frequency) it has very very low series resistance.
The series resistance of the diode contributes Johnson noise that can't
be removed by bootstrapping. You don't care too much at 10 kHz, but at higher frequency the 50-300 ohms' worth of Rseries in most diodes will
trash the SNR--there's not much use in a 300-pV/sqrt(Hz) TIA if the
diode itself contributes way over a nanovolt.
john larkin <JL@gct.com> wrote:
On Sun, 27 Oct 2024 22:59:59 -0000 (UTC), piglet
<erichpwagner@hotmail.com> wrote:
Klaus Vestergaard Kragelund <klauskvik@hotmail.com> wrote:
On 27-10-2024 13:26, Klaus Vestergaard Kragelund wrote:
On 27-10-2024 03:26, john larkin wrote:Actually, wont a simple high pass filter work equally well?
On Sun, 27 Oct 2024 02:19:14 +0200, Klaus Vestergaard Kragelund
<klauskvik@hotmail.com> wrote:
Hi
I am working on an IR detector that will guide a robot into a docking >>>>>>> station.
A IR transmitter on the docking station transmits a beam, and 2 IR >>>>>>> detectors on the robot detects the beam and lets the robot navigate >>>>>>> towards the target. The working distance is a couple of meters.
I need it to be insensitive to ambient light/sunlight.
The IR detectors are placed in a tube, to narrow in the beam angle and >>>>>>> to avoid sunlight (since it is seldom the sun is actually that low in >>>>>>> the horizon)
The IR transmitter will be modulated with 10kHz (TBD) frequency, low >>>>>>> duty cycle. Low duty cycle to be able to drive the LED with high >>>>>>> current, frequency modulated so that the receiver can ignore the effect >>>>>>> of daylight (DC)
If the LED on the docking station has higher radiant intensity at the >>>>>>> point of the robot (2 meters away) than possible IR from sunlight, then >>>>>>> that would be perfect.
Example of transmitter:
https://www.vishay.com/docs/83398/vsmy2850.pdf
Has up to 1000mW/sr. Seems my basic calculation for a 15 degree beam, >>>>>>> shows less than 10nW/m2, while sunlight has 1W/m2. So driving a beam >>>>>>> that has higher output than sunlight seems unlikely.
I would use a IR phototransistor at 850nm, something like this:
https://www.ttelectronics.com/TTElectronics/media/ProductFiles/
Datasheet/OP505-506-535-705.pdf
Or a photo diode:
https://docs.rs-online.com/9f58/0900766b816d8a09.pdf
Fed from reverse 3.3V and into a transimpedance amplifier to boost the >>>>>>> signal with bandpass filter.
One can get digital IR detector used in a remote control systems: >>>>>>>
https://www.vishay.com/docs/82491/tsop382.pdf
It has AGC, but digital output. I need analog output to be able to zero >>>>>>> in on the transmitter beam.
I have been looking for IR detectors that has the analog output, not >>>>>>> just the digital, but have not found any.
If the photodiode detector is subjected to sunlight, I am guessing I >>>>>>> would need very high gain on the 10kHz modulation frequency to pick up >>>>>>> the burried signal in the DC from sunlight.
How do I best bias the photo diode for optimum detection of the 10kHz >>>>>>> signal while being immune to the ambient sunlight?
I have chosen 850nm which seems to be a good wavelength. The spectrum at
sea level has some dips due to water absorption.
https://sciencetech-inc.com/web/image/49169/
Spectrum%20with_out%20absorption.png
Seems like 750nm would be better, since then the IR from the sun is >>>>>>> lower, but does reduced the effective range of the system during >>>>>>> fog/rain. Probably that's why these system do not use 750nm
Other considerations?
You could drive the LED with a square wave, 10 KHz or whatever. The >>>>>> photodiode could have +DC on one end and the other end can hit a
parallel LC to ground, resonant at 10K.
That takes out the sunlight DC component and adds bandpass filtering. >>>>>>
That's a very nice idea. The Q should not matter much, just as long as >>>>> DC is removed.
The photodiode will still be subjected to the high ambient light, but >>>>> the gain would be close to zero for the stage after. I would then still >>>>> need to be sure the photodiode is never saturated by ambient light.
Photo diode with bias -> capacitor to gain block....
If you make it part of the bias network yes, a gyrator either a single
transistor or op amp could take the role of inductor.
When you need an inductor, an inductor makes an excellent inductor.
But the dual microphone thing, electret or mems, sounds like a much
better way to go.
Some folk are scared of inductors. 10kHz does mean quite a few milli
henries.
Of course they might be able to reverse the process and have one receiver
on the robot and two emitters on the docking station, a bit like aircraft
VOR
On 27-10-2024 21:39, Joe Gwinn wrote:
On Sun, 27 Oct 2024 10:49:27 -0700, john larkin <JL@gct.com> wrote:
On Sun, 27 Oct 2024 13:42:27 +0100, Klaus Vestergaard Kragelund
<klauskvik@hotmail.com> wrote:
On 27-10-2024 13:40, Klaus Vestergaard Kragelund wrote:
On 27-10-2024 13:26, Klaus Vestergaard Kragelund wrote:
On 27-10-2024 03:26, john larkin wrote:
On Sun, 27 Oct 2024 02:19:14 +0200, Klaus Vestergaard Kragelund
<klauskvik@hotmail.com> wrote:
Hi
I am working on an IR detector that will guide a robot into a docking >>>>>>>> station.
A IR transmitter on the docking station transmits a beam, and 2 IR >>>>>>>> detectors on the robot detects the beam and lets the robot navigate >>>>>>>> towards the target. The working distance is a couple of meters. >>>>>>>>
I need it to be insensitive to ambient light/sunlight.
The IR detectors are placed in a tube, to narrow in the beam angle and >>>>>>>> to avoid sunlight (since it is seldom the sun is actually that low in >>>>>>>> the horizon)
The IR transmitter will be modulated with 10kHz (TBD) frequency, low >>>>>>>> duty cycle. Low duty cycle to be able to drive the LED with high >>>>>>>> current, frequency modulated so that the receiver can ignore the effect
of daylight (DC)
If the LED on the docking station has higher radiant intensity at the >>>>>>>> point of the robot (2 meters away) than possible IR from sunlight, then
that would be perfect.
Example of transmitter:
https://www.vishay.com/docs/83398/vsmy2850.pdf
Has up to 1000mW/sr. Seems my basic calculation for a 15 degree beam, >>>>>>>> shows less than 10nW/m2, while sunlight has 1W/m2. So driving a beam >>>>>>>> that has higher output than sunlight seems unlikely.
I would use a IR phototransistor at 850nm, something like this: >>>>>>>>
https://www.ttelectronics.com/TTElectronics/media/ProductFiles/ >>>>>>>> Datasheet/OP505-506-535-705.pdf
Or a photo diode:
https://docs.rs-online.com/9f58/0900766b816d8a09.pdf
Fed from reverse 3.3V and into a transimpedance amplifier to boost the >>>>>>>> signal with bandpass filter.
One can get digital IR detector used in a remote control systems: >>>>>>>>
https://www.vishay.com/docs/82491/tsop382.pdf
It has AGC, but digital output. I need analog output to be able to zero
in on the transmitter beam.
I have been looking for IR detectors that has the analog output, not >>>>>>>> just the digital, but have not found any.
If the photodiode detector is subjected to sunlight, I am guessing I >>>>>>>> would need very high gain on the 10kHz modulation frequency to pick up >>>>>>>> the burried signal in the DC from sunlight.
How do I best bias the photo diode for optimum detection of the 10kHz >>>>>>>> signal while being immune to the ambient sunlight?
I have chosen 850nm which seems to be a good wavelength. The
spectrum at
sea level has some dips due to water absorption.
https://sciencetech-inc.com/web/image/49169/
Spectrum%20with_out%20absorption.png
Seems like 750nm would be better, since then the IR from the sun is >>>>>>>> lower, but does reduced the effective range of the system during >>>>>>>> fog/rain. Probably that's why these system do not use 750nm
Other considerations?
You could drive the LED with a square wave, 10 KHz or whatever. The >>>>>>> photodiode could have +DC on one end and the other end can hit a >>>>>>> parallel LC to ground, resonant at 10K.
That takes out the sunlight DC component and adds bandpass filtering. >>>>>>>
That's a very nice idea. The Q should not matter much, just as long as >>>>>> DC is removed.
The photodiode will still be subjected to the high ambient light, but >>>>>> the gain would be close to zero for the stage after. I would then
still need to be sure the photodiode is never saturated by ambient light.
A photodiode won't saturate as long as it has a few volts of DC across
it. It might melt if there's no current limiting.
Actually, wont a simple high pass filter work equally well?
Photo diode with bias -> capacitor to gain block....
Like this:
https://electronics.stackexchange.com/questions/416184/how-does-this-op-amp-photodiode-circuit-behave
The LC tank combines background light rejection and bandpass filtering
and has high signal gain, with two parts.
I think there are photodiodes with colored plastic, essentially a
cheap optical bandpass filter. Used in TV remote receivers.
The windows in TVs may be optical bandpass filters too. They work with
very little signal from the remote, in high room light.
To this I would add a trick. We know something very useful about the
10 KHz modulation, its exact frequency, given that it is (or can be)
generated electronically, and thus its frequency is ultimately
controlled by a logic-clock crystal oscillator.
So feed the amplified signal from the 10 KHz LC tank to a I+Q homodyne
circuit, filter to pass signals from DC to a 10 Hz and compute the
magnitude of the received signal - this is used for figuring out the
direction to the docking station.
Very nice, sort of like for lock-in detection, I have done that before,
works great. Would take the tolerances out of the passive components.
On Mon, 28 Oct 2024 11:08:50 +0100, Klaus Vestergaard Kragelund <klauskvik@hotmail.com> wrote:
On 27-10-2024 21:39, Joe Gwinn wrote:
On Sun, 27 Oct 2024 10:49:27 -0700, john larkin <JL@gct.com> wrote:
On Sun, 27 Oct 2024 13:42:27 +0100, Klaus Vestergaard Kragelund
<klauskvik@hotmail.com> wrote:
On 27-10-2024 13:40, Klaus Vestergaard Kragelund wrote:
On 27-10-2024 13:26, Klaus Vestergaard Kragelund wrote:
On 27-10-2024 03:26, john larkin wrote:
On Sun, 27 Oct 2024 02:19:14 +0200, Klaus Vestergaard Kragelund >>>>>>>> <klauskvik@hotmail.com> wrote:
Hi
I am working on an IR detector that will guide a robot into a docking >>>>>>>>> station.
A IR transmitter on the docking station transmits a beam, and 2 IR >>>>>>>>> detectors on the robot detects the beam and lets the robot navigate >>>>>>>>> towards the target. The working distance is a couple of meters. >>>>>>>>>
I need it to be insensitive to ambient light/sunlight.
The IR detectors are placed in a tube, to narrow in the beam angle and
to avoid sunlight (since it is seldom the sun is actually that low in >>>>>>>>> the horizon)
The IR transmitter will be modulated with 10kHz (TBD) frequency, low >>>>>>>>> duty cycle. Low duty cycle to be able to drive the LED with high >>>>>>>>> current, frequency modulated so that the receiver can ignore the effect
of daylight (DC)
If the LED on the docking station has higher radiant intensity at the >>>>>>>>> point of the robot (2 meters away) than possible IR from sunlight, then
that would be perfect.
Example of transmitter:
https://www.vishay.com/docs/83398/vsmy2850.pdf
Has up to 1000mW/sr. Seems my basic calculation for a 15 degree beam, >>>>>>>>> shows less than 10nW/m2, while sunlight has 1W/m2. So driving a beam >>>>>>>>> that has higher output than sunlight seems unlikely.
I would use a IR phototransistor at 850nm, something like this: >>>>>>>>>
https://www.ttelectronics.com/TTElectronics/media/ProductFiles/ >>>>>>>>> Datasheet/OP505-506-535-705.pdf
Or a photo diode:
https://docs.rs-online.com/9f58/0900766b816d8a09.pdf
Fed from reverse 3.3V and into a transimpedance amplifier to boost the
signal with bandpass filter.
One can get digital IR detector used in a remote control systems: >>>>>>>>>
https://www.vishay.com/docs/82491/tsop382.pdf
It has AGC, but digital output. I need analog output to be able to zero
in on the transmitter beam.
I have been looking for IR detectors that has the analog output, not >>>>>>>>> just the digital, but have not found any.
If the photodiode detector is subjected to sunlight, I am guessing I >>>>>>>>> would need very high gain on the 10kHz modulation frequency to pick up
the burried signal in the DC from sunlight.
How do I best bias the photo diode for optimum detection of the 10kHz >>>>>>>>> signal while being immune to the ambient sunlight?
I have chosen 850nm which seems to be a good wavelength. The >>>>>>>>> spectrum at
sea level has some dips due to water absorption.
https://sciencetech-inc.com/web/image/49169/
Spectrum%20with_out%20absorption.png
Seems like 750nm would be better, since then the IR from the sun is >>>>>>>>> lower, but does reduced the effective range of the system during >>>>>>>>> fog/rain. Probably that's why these system do not use 750nm
Other considerations?
You could drive the LED with a square wave, 10 KHz or whatever. The >>>>>>>> photodiode could have +DC on one end and the other end can hit a >>>>>>>> parallel LC to ground, resonant at 10K.
That takes out the sunlight DC component and adds bandpass filtering. >>>>>>>>
That's a very nice idea. The Q should not matter much, just as long as >>>>>>> DC is removed.
The photodiode will still be subjected to the high ambient light, but >>>>>>> the gain would be close to zero for the stage after. I would then >>>>>>> still need to be sure the photodiode is never saturated by ambient light.
A photodiode won't saturate as long as it has a few volts of DC across >>>> it. It might melt if there's no current limiting.
Actually, wont a simple high pass filter work equally well?
Photo diode with bias -> capacitor to gain block....
Like this:
https://electronics.stackexchange.com/questions/416184/how-does-this-op-amp-photodiode-circuit-behave
The LC tank combines background light rejection and bandpass filtering >>>> and has high signal gain, with two parts.
I think there are photodiodes with colored plastic, essentially a
cheap optical bandpass filter. Used in TV remote receivers.
The windows in TVs may be optical bandpass filters too. They work with >>>> very little signal from the remote, in high room light.
To this I would add a trick. We know something very useful about the
10 KHz modulation, its exact frequency, given that it is (or can be)
generated electronically, and thus its frequency is ultimately
controlled by a logic-clock crystal oscillator.
So feed the amplified signal from the 10 KHz LC tank to a I+Q homodyne
circuit, filter to pass signals from DC to a 10 Hz and compute the
magnitude of the received signal - this is used for figuring out the
direction to the docking station.
Very nice, sort of like for lock-in detection, I have done that before,
works great. Would take the tolerances out of the passive components.
Yes, it is a form of lock-in detection, adapted to the lack of phase
data, other than to know that it changes slowly.
But there is another issue, interference from artificial light, such
as streetlamps, at dawn and dusk. Many streetlamps are strongly
modulated at a harmonic of the local prime power frequency, 50 Hz or
60 Hz. Also, the receiver itself will have a noise floor that is
essentially constant random noise.
A classic remedy is correlated double sampling (CDS), where the sample
period is exactly one tenth of a second in duration, into which an
integral number of power cycles will fit exactly, and so will
integrate to zero.
Originally, CDS modulated the transmitter to alternate between on and
off, so external light would fall in both odd and even numbered
samples, while real data would only fall in one set of samples. Here
the TX runs continuously, and it would be a nuisance to synchronize
it, so we need a way to do the same in the RX units.
The simplest approach would be to receive at two modulation
frequencies, 10 KHz and say 11 KHz, alternating between them. Only
the 10 KHz will have data, while both frequencies will have system
noise and power-frequency modulated stray light.
There are two identical integrators and a switch. The odd-numbered
cycles go into the first integrator and the even-numbered cycles go to
the second integrator. These integrator are leaky. One reports their difference as the 10 KHz modulation strength.
There are many schemes like this that could work.
Joe Gwinn
On 2024-10-27 08:26, Klaus Vestergaard Kragelund wrote:
On 27-10-2024 03:26, john larkin wrote:
On Sun, 27 Oct 2024 02:19:14 +0200, Klaus Vestergaard Kragelund
<klauskvik@hotmail.com> wrote:
Hi
I am working on an IR detector that will guide a robot into a docking
station.
A IR transmitter on the docking station transmits a beam, and 2 IR
detectors on the robot detects the beam and lets the robot navigate
towards the target. The working distance is a couple of meters.
I need it to be insensitive to ambient light/sunlight.
The IR detectors are placed in a tube, to narrow in the beam angle and >>>> to avoid sunlight (since it is seldom the sun is actually that low in
the horizon)
The IR transmitter will be modulated with 10kHz (TBD) frequency, low
duty cycle. Low duty cycle to be able to drive the LED with high
current, frequency modulated so that the receiver can ignore the effect >>>> of daylight (DC)
If the LED on the docking station has higher radiant intensity at the
point of the robot (2 meters away) than possible IR from sunlight, then >>>> that would be perfect.
Example of transmitter:
https://www.vishay.com/docs/83398/vsmy2850.pdf
Has up to 1000mW/sr. Seems my basic calculation for a 15 degree beam,
shows less than 10nW/m2, while sunlight has 1W/m2. So driving a beam
that has higher output than sunlight seems unlikely.
I would use a IR phototransistor at 850nm, something like this:
https://www.ttelectronics.com/TTElectronics/media/ProductFiles/
Datasheet/OP505-506-535-705.pdf
Or a photo diode:
https://docs.rs-online.com/9f58/0900766b816d8a09.pdf
Fed from reverse 3.3V and into a transimpedance amplifier to boost the >>>> signal with bandpass filter.
One can get digital IR detector used in a remote control systems:
https://www.vishay.com/docs/82491/tsop382.pdf
It has AGC, but digital output. I need analog output to be able to zero >>>> in on the transmitter beam.
I have been looking for IR detectors that has the analog output, not
just the digital, but have not found any.
If the photodiode detector is subjected to sunlight, I am guessing I
would need very high gain on the 10kHz modulation frequency to pick up >>>> the burried signal in the DC from sunlight.
How do I best bias the photo diode for optimum detection of the 10kHz
signal while being immune to the ambient sunlight?
I have chosen 850nm which seems to be a good wavelength. The
spectrum at
sea level has some dips due to water absorption.
https://sciencetech-inc.com/web/image/49169/
Spectrum%20with_out%20absorption.png
Seems like 750nm would be better, since then the IR from the sun is
lower, but does reduced the effective range of the system during
fog/rain. Probably that's why these system do not use 750nm
Other considerations?
You could drive the LED with a square wave, 10 KHz or whatever. The
photodiode could have +DC on one end and the other end can hit a
parallel LC to ground, resonant at 10K.
That takes out the sunlight DC component and adds bandpass filtering.
That's a very nice idea. The Q should not matter much, just as long as
DC is removed.
The photodiode will still be subjected to the high ambient light, but
the gain would be close to zero for the stage after. I would then
still need to be sure the photodiode is never saturated by ambient light.
Just don't fry the photodiode in high light.
So adding a resistance in series with the diode?
Nah, the Johnson noise kills you. It's easier to just calculate or
measure the photocurrent from direct sunlight and design around that.
You only need enough bias to ensure linear operation at high current,
maybe a volt or so.
You will want to put a filter in the second stage to get rid of the
nasty high-frequency noise peak. I usually use a two-pole Sallen-Key
with equal resistor values, which has predictable gain (1.00) and low component-value sensitivity, and is super simple.
Resist the temptation to do anything floral with the TIA stage, such as
LC or *especially* gyrator filtering. A large inductor is a disaster in
a TIA, because if it doesn't cause instability, it'll still pick up crap
from every VF motor drive on the block, and deposit it right into the
summing junction, where you really really don't want it.
You don't need a bootstrap at 10 kHz, but a sufficiently carefully
designed DC restore loop can help sometimes. A badly designed one will trash the SNR. At low frequency, the only way to make a quiet current
source is to put a large voltage across a large resistor. I usually do
that in the emitter circuit of a BJT, to get higher Zout, but you can
also do it barefoot.
The thing is, you're going to be dominated by the shot noise of the DC restore current unless its resistor is much larger than the feedback
resistor of the TIA. (At high frequency you can use filtering tricks,
but not easily at 10 kHz.)Â Since the DC restore is going to have the
same supply headroom as the TIA, it really doesn't help.
If you pick the TIA's feedback resistance so that the IR signal produces
50 mV of output, you're in the shot noise limit, at least in the dark. However, since the sunlight's shot noise is going to be the limit most
of the time, just pick a feedback resistor so the TIA nearly rails at
the worst-case background light level, and see if that gives you enough
SNR to be going on with. If so, AC-couple it into the second stage and you're done.
If not, you need to reduce the background with a better filter, or
(better) reduce the field of view by using a lens on the receiver, and increase the signal by using one on the transmitter. You win by the
square of the angular magnification, which can be a fairly startling
number.
Either way, you need to control your detection bandwidth to something reasonable, and remember that LP filter to get rid of the noise peak!
On Mon, 28 Oct 2024 11:11:38 +0100, Klaus Vestergaard Kragelund <klauskvik@hotmail.com> wrote:
On 27-10-2024 18:56, john larkin wrote:
On Sun, 27 Oct 2024 09:03:20 GMT, Jan Panteltje <alien@comet.invalid>Could also be done with a chirp and auto-correlation, although this does
wrote:
On a sunny day (Sun, 27 Oct 2024 02:19:14 +0200) it happened Klaus Vestergaard
Kragelund <klauskvik@hotmail.com> wrote in <vfk0u0$3u9en$1@dont-email.me>: >>>>
Hi
I am working on an IR detector that will guide a robot into a docking >>>>> station.
A IR transmitter on the docking station transmits a beam, and 2 IR
detectors on the robot detects the beam and lets the robot navigate
towards the target. The working distance is a couple of meters.
I need it to be insensitive to ambient light/sunlight.
I use a cheap camera module to track a light source in H and V direction, and just a simple Microchip PIC : for processing
It can, with some added code, track object forms too, like a cross or maybe a big character.
panteltje.nl/pub/horizontal_IR_target_tracking_4686.avi
those camara modulea are IR sensitive to some extend, sometimes you can remove the IR filter from such modules.
It may be a bit of overkill for your application, but OTOH it can do a lot more.
Mainly designed to detect and follow jet exhaust..
You could uee utrasonics too, maybe even simpler, no sun problem, like a bat.
Cheap electret mikes? or modify some ebay 1 dolalr distance sensors... >>>> can be used for anti-collision too.
Right. A sonic scheme could measure the phase between two mikes to
determine the direction of the source with high resolution. That could
be an analog multiplier or a bit of code. The amplitudes would be
useful too.
One could compute direction, distance, and velocity almost for free.
No problem with sunlight!
not use the phase, but a beacon reference instead
Could that tell the direction of the mother ship?
Three or four omni mems microphones could tell the robot which
direction to go with full 360 degree coverage.
Maybe even estimate range.
On 10/28/2024 3:17 AM, Klaus Vestergaard Kragelund wrote:
A IR transmitter on the docking station transmits a beam, and 2 IR >>>>>> detectors on the robot detects the beam and lets the robot
navigate towards the target. The working distance is a couple of
meters.
Can the robot ALWAYS see the docking station? What happens if an
obstacle (wall?) comes between the two?
Yes, we have RTK GPS to position it within a cm at a location right
in front of the docking, 2 meters away.
Then why can't you move to the GPS location of the dock with the
same degree of accuracy?
The docking station is typically in a shed, or close to a building
where the GPS signal disappears.
Ah, OK.
Can either device (robot/dock) ever slip out of the shared plane?
No, should be locked
"Outdoors" (from below). Presumably on pavement/concrete (not a "lawn") >>> that wouldn't have dips and bumps?
It's moving on grass, and can have bumps etc, so for IR the lope needs
to be perhaps 20degrees to avoid loss of signal
And, presumably, they are short (time and space) transients? *Faster*
than the response time of the robots controls?
I have become particularly fond of using cameras to interface with
the real world. Of course, it requires a bit more horsepower but
seems to be able to overcome all of the issues that have crept up...
That's also a solution we have been working on. The Worx Vision uses
that
https://eu.worx.com/da-dk/landroid/vision-technology/
That is for a future version. Cameras can also be blinded, lenses
needs to be cleaned etc
Yes, but a camera can be "queried" to verify that it is functioning
correctly: "What do you see? Is it THIS?"
I test my cameras by storing previously viewed scenes to verify they
are still "reasonably" intact. Ideally, I would move something into
the field of view but that requires additional capabilities.
You, however, could move the robot (assuming IT has the eyes) and
verify that the scene changes accordingly.
Could be done. The guys in charge are worried with change of
environment, so what happens when it snows heavily, fog or other
surroundings changing effects.
You extract salient "features" from the scene and use them.
The robot doesn't need to be concerned about whether the ground is
green, brown or white. Or, if the shed is in shade, blanketed
with snow, etc.
E.g., I use them to "watch" the garage door rails (which have a specific shape) to see if any objects have come between the camera and the rails.
(The rails define the plane that the garage door will occupy as
it closes)Â Of course, everything around the rails is highly variable
as garages are notorious for clutter and dynamism.
Another camera "watches" the mailbox by the road. In addition to
the surroundings changing, there can be pedestrian and vehicular
traffic passing at any time. In our case, it is illegal to
drive while using a phone so folks often pull over to answer
phone calls -- our mailbox is in a shaded area that seems to be
highly desirable to such motorists-in-need. But, *their*
vehicles don't look like "mail trucks" so no chance of thinking that
*they* are delivering our mail...
As I said before, it is a really great "sensor"! The downside is
that you need resources to use it (your optical approach is likely
possible with far less resources -- think of how robot vaccuum cleaners operate wrt their charging docks)
On 28-10-2024 20:16, Phil Hobbs wrote:
On 2024-10-27 08:20, Klaus Vestergaard Kragelund wrote:
On 27-10-2024 03:05, Phil Hobbs wrote:
Klaus Vestergaard Kragelund <klauskvik@hotmail.com> wrote:
Hi
I am working on an IR detector that will guide a robot into a docking >>>>> station.
A IR transmitter on the docking station transmits a beam, and 2 IR
detectors on the robot detects the beam and lets the robot navigate
towards the target. The working distance is a couple of meters.
I need it to be insensitive to ambient light/sunlight.
The IR detectors are placed in a tube, to narrow in the beam angle and >>>>> to avoid sunlight (since it is seldom the sun is actually that low in >>>>> the horizon)
The IR transmitter will be modulated with 10kHz (TBD) frequency, low >>>>> duty cycle. Low duty cycle to be able to drive the LED with high
current, frequency modulated so that the receiver can ignore the
effect
of daylight (DC)
If the LED on the docking station has higher radiant intensity at the >>>>> point of the robot (2 meters away) than possible IR from sunlight,
then
that would be perfect.
Example of transmitter:
https://www.vishay.com/docs/83398/vsmy2850.pdf
Has up to 1000mW/sr. Seems my basic calculation for a 15 degree beam, >>>>> shows less than 10nW/m2, while sunlight has 1W/m2. So driving a beam >>>>> that has higher output than sunlight seems unlikely.
I would use a IR phototransistor at 850nm, something like this:
https://www.ttelectronics.com/TTElectronics/media/ProductFiles/
Datasheet/OP505-506-535-705.pdf
Or a photo diode:
https://docs.rs-online.com/9f58/0900766b816d8a09.pdf
Fed from reverse 3.3V and into a transimpedance amplifier to boost the >>>>> signal with bandpass filter.
One can get digital IR detector used in a remote control systems:
https://www.vishay.com/docs/82491/tsop382.pdf
It has AGC, but digital output. I need analog output to be able to
zero
in on the transmitter beam.
I have been looking for IR detectors that has the analog output, not >>>>> just the digital, but have not found any.
If the photodiode detector is subjected to sunlight, I am guessing I >>>>> would need very high gain on the 10kHz modulation frequency to pick up >>>>> the burried signal in the DC from sunlight.
How do I best bias the photo diode for optimum detection of the 10kHz >>>>> signal while being immune to the ambient sunlight?
I have chosen 850nm which seems to be a good wavelength. The
spectrum at
sea level has some dips due to water absorption.
https://sciencetech-inc.com/web/image/49169/
Spectrum%20with_out%20absorption.png
Seems like 750nm would be better, since then the IR from the sun is
lower, but does reduced the effective range of the system during
fog/rain. Probably that's why these system do not use 750nm
Other considerations?
Phototransistors are horrible for that sort of job— too small, too
noisy,
not repeatable, for a start.
It’s not signal/background you care about, it’s signal/noise,
specifically
the shot noise of the sunlight.
An optical filter will help reject sunlight, and a bigger detector will >>>> help more. The real win is reducing the FOV with lenses as well as
baffles,
tubes, and so on.
I have tried to search for optical filters. Where would one get those?
700-nm plastic longpass filter material comes in sheets. You can get
smallish chunks of it on the jungle website and various other emporia.
Fancier things, such as narrowish bandpasses and custom wavelengths,
tend to be glass and quite a lot more expensive. I usually get those
from Omega Optical, but there are European suppliers as well.
For this use, a regular 700-nmm plastic longpass will get rid of most
of the daylight, which is what you want. You can also get photodiodes
with the filter material included, e.g. the ever-popular BPW34F.
Great recommendations, thanks. I have purchased a bunch of the BPW34F.
So in fact the devil is in the detail. I have not done higher
Baffles and tubes, we can do ourselves, any guideline on the best
surface of the inner tube?
Regular old flat black paint. But a lens on the transmitter will be
the biggest win.
Check out the Hamamatsu S6968–super good medicine.
Looks like a very big die. Is that the main reason to use that one,
to get better sensitivity?
It has very low capacitance for its area, it has a lens to increase
the detection area, and (crucially for my uses, which are generally at
higher frequency) it has very very low series resistance.
The series resistance of the diode contributes Johnson noise that
can't be removed by bootstrapping. You don't care too much at 10 kHz,
but at higher frequency the 50-300 ohms' worth of Rseries in most
diodes will trash the SNR--there's not much use in a 300-pV/sqrt(Hz)
TIA if the diode itself contributes way over a nanovolt.
performance optics before, so riding on the learning curve.
Klaus Vestergaard Kragelund <klauskvik@hotmail.com> wrote:
On 27-10-2024 13:26, Klaus Vestergaard Kragelund wrote:
On 27-10-2024 03:26, john larkin wrote:Actually, wont a simple high pass filter work equally well?
On Sun, 27 Oct 2024 02:19:14 +0200, Klaus Vestergaard Kragelund
<klauskvik@hotmail.com> wrote:
Hi
I am working on an IR detector that will guide a robot into a docking >>>>> station.
A IR transmitter on the docking station transmits a beam, and 2 IR
detectors on the robot detects the beam and lets the robot navigate
towards the target. The working distance is a couple of meters.
I need it to be insensitive to ambient light/sunlight.
The IR detectors are placed in a tube, to narrow in the beam angle and >>>>> to avoid sunlight (since it is seldom the sun is actually that low in >>>>> the horizon)
The IR transmitter will be modulated with 10kHz (TBD) frequency, low >>>>> duty cycle. Low duty cycle to be able to drive the LED with high
current, frequency modulated so that the receiver can ignore the effect >>>>> of daylight (DC)
If the LED on the docking station has higher radiant intensity at the >>>>> point of the robot (2 meters away) than possible IR from sunlight, then >>>>> that would be perfect.
Example of transmitter:
https://www.vishay.com/docs/83398/vsmy2850.pdf
Has up to 1000mW/sr. Seems my basic calculation for a 15 degree beam, >>>>> shows less than 10nW/m2, while sunlight has 1W/m2. So driving a beam >>>>> that has higher output than sunlight seems unlikely.
I would use a IR phototransistor at 850nm, something like this:
https://www.ttelectronics.com/TTElectronics/media/ProductFiles/
Datasheet/OP505-506-535-705.pdf
Or a photo diode:
https://docs.rs-online.com/9f58/0900766b816d8a09.pdf
Fed from reverse 3.3V and into a transimpedance amplifier to boost the >>>>> signal with bandpass filter.
One can get digital IR detector used in a remote control systems:
https://www.vishay.com/docs/82491/tsop382.pdf
It has AGC, but digital output. I need analog output to be able to zero >>>>> in on the transmitter beam.
I have been looking for IR detectors that has the analog output, not >>>>> just the digital, but have not found any.
If the photodiode detector is subjected to sunlight, I am guessing I >>>>> would need very high gain on the 10kHz modulation frequency to pick up >>>>> the burried signal in the DC from sunlight.
How do I best bias the photo diode for optimum detection of the 10kHz >>>>> signal while being immune to the ambient sunlight?
I have chosen 850nm which seems to be a good wavelength. The spectrum at >>>>> sea level has some dips due to water absorption.
https://sciencetech-inc.com/web/image/49169/
Spectrum%20with_out%20absorption.png
Seems like 750nm would be better, since then the IR from the sun is
lower, but does reduced the effective range of the system during
fog/rain. Probably that's why these system do not use 750nm
Other considerations?
You could drive the LED with a square wave, 10 KHz or whatever. The
photodiode could have +DC on one end and the other end can hit a
parallel LC to ground, resonant at 10K.
That takes out the sunlight DC component and adds bandpass filtering.
That's a very nice idea. The Q should not matter much, just as long as
DC is removed.
The photodiode will still be subjected to the high ambient light, but
the gain would be close to zero for the stage after. I would then still
need to be sure the photodiode is never saturated by ambient light.
Photo diode with bias -> capacitor to gain block....
If you make it part of the bias network yes, a gyrator either a single transistor or op amp could take the role of inductor.
As I said before, it is a really great "sensor"! The downside is
that you need resources to use it (your optical approach is likely
possible with far less resources -- think of how robot vaccuum cleaners
operate wrt their charging docks)
Correct, all though high resolutionn cameraes are very cheap nowadays. And they
have a Linux maching running the application SW, so adding a camera does not add much extra cost, just a camera interface IC.
It's Burr-Brown(I'm old) OPT201.
https://electronix.org.ru/datasheet/Burr-Brown/AB-061%20-%20OPT201%20to%20reject%20ambient%20light.pdf
john larkin <JL@gct.com> wrote:
On Sun, 27 Oct 2024 22:59:59 -0000 (UTC), piglet
<erichpwagner@hotmail.com> wrote:
Klaus Vestergaard Kragelund <klauskvik@hotmail.com> wrote:
On 27-10-2024 13:26, Klaus Vestergaard Kragelund wrote:
On 27-10-2024 03:26, john larkin wrote:Actually, wont a simple high pass filter work equally well?
On Sun, 27 Oct 2024 02:19:14 +0200, Klaus Vestergaard Kragelund
<klauskvik@hotmail.com> wrote:
Hi
I am working on an IR detector that will guide a robot into a docking >>>>>>> station.
A IR transmitter on the docking station transmits a beam, and 2 IR >>>>>>> detectors on the robot detects the beam and lets the robot navigate >>>>>>> towards the target. The working distance is a couple of meters.
I need it to be insensitive to ambient light/sunlight.
The IR detectors are placed in a tube, to narrow in the beam angle and >>>>>>> to avoid sunlight (since it is seldom the sun is actually that low in >>>>>>> the horizon)
The IR transmitter will be modulated with 10kHz (TBD) frequency, low >>>>>>> duty cycle. Low duty cycle to be able to drive the LED with high >>>>>>> current, frequency modulated so that the receiver can ignore the effect >>>>>>> of daylight (DC)
If the LED on the docking station has higher radiant intensity at the >>>>>>> point of the robot (2 meters away) than possible IR from sunlight, then >>>>>>> that would be perfect.
Example of transmitter:
https://www.vishay.com/docs/83398/vsmy2850.pdf
Has up to 1000mW/sr. Seems my basic calculation for a 15 degree beam, >>>>>>> shows less than 10nW/m2, while sunlight has 1W/m2. So driving a beam >>>>>>> that has higher output than sunlight seems unlikely.
I would use a IR phototransistor at 850nm, something like this:
https://www.ttelectronics.com/TTElectronics/media/ProductFiles/
Datasheet/OP505-506-535-705.pdf
Or a photo diode:
https://docs.rs-online.com/9f58/0900766b816d8a09.pdf
Fed from reverse 3.3V and into a transimpedance amplifier to boost the >>>>>>> signal with bandpass filter.
One can get digital IR detector used in a remote control systems: >>>>>>>
https://www.vishay.com/docs/82491/tsop382.pdf
It has AGC, but digital output. I need analog output to be able to zero >>>>>>> in on the transmitter beam.
I have been looking for IR detectors that has the analog output, not >>>>>>> just the digital, but have not found any.
If the photodiode detector is subjected to sunlight, I am guessing I >>>>>>> would need very high gain on the 10kHz modulation frequency to pick up >>>>>>> the burried signal in the DC from sunlight.
How do I best bias the photo diode for optimum detection of the 10kHz >>>>>>> signal while being immune to the ambient sunlight?
I have chosen 850nm which seems to be a good wavelength. The spectrum at
sea level has some dips due to water absorption.
https://sciencetech-inc.com/web/image/49169/
Spectrum%20with_out%20absorption.png
Seems like 750nm would be better, since then the IR from the sun is >>>>>>> lower, but does reduced the effective range of the system during >>>>>>> fog/rain. Probably that's why these system do not use 750nm
Other considerations?
You could drive the LED with a square wave, 10 KHz or whatever. The >>>>>> photodiode could have +DC on one end and the other end can hit a
parallel LC to ground, resonant at 10K.
That takes out the sunlight DC component and adds bandpass filtering. >>>>>>
That's a very nice idea. The Q should not matter much, just as long as >>>>> DC is removed.
The photodiode will still be subjected to the high ambient light, but >>>>> the gain would be close to zero for the stage after. I would then still >>>>> need to be sure the photodiode is never saturated by ambient light.
Photo diode with bias -> capacitor to gain block....
If you make it part of the bias network yes, a gyrator either a single
transistor or op amp could take the role of inductor.
When you need an inductor, an inductor makes an excellent inductor.
But the dual microphone thing, electret or mems, sounds like a much
better way to go.
Some folk are scared of inductors. 10kHz does mean quite a few milli
henries.
Of course they might be able to reverse the process and have one receiver
on the robot and two emitters on the docking station, a bit like aircraft
VOR
On Mon, 28 Oct 2024 15:49:30 -0400, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:
On 2024-10-27 08:26, Klaus Vestergaard Kragelund wrote:
On 27-10-2024 03:26, john larkin wrote:
On Sun, 27 Oct 2024 02:19:14 +0200, Klaus Vestergaard Kragelund
<klauskvik@hotmail.com> wrote:
Hi
I am working on an IR detector that will guide a robot into a docking >>>>> station.
A IR transmitter on the docking station transmits a beam, and 2 IR
detectors on the robot detects the beam and lets the robot navigate
towards the target. The working distance is a couple of meters.
I need it to be insensitive to ambient light/sunlight.
The IR detectors are placed in a tube, to narrow in the beam angle and >>>>> to avoid sunlight (since it is seldom the sun is actually that low in >>>>> the horizon)
The IR transmitter will be modulated with 10kHz (TBD) frequency, low >>>>> duty cycle. Low duty cycle to be able to drive the LED with high
current, frequency modulated so that the receiver can ignore the effect >>>>> of daylight (DC)
If the LED on the docking station has higher radiant intensity at the >>>>> point of the robot (2 meters away) than possible IR from sunlight, then >>>>> that would be perfect.
Example of transmitter:
https://www.vishay.com/docs/83398/vsmy2850.pdf
Has up to 1000mW/sr. Seems my basic calculation for a 15 degree beam, >>>>> shows less than 10nW/m2, while sunlight has 1W/m2. So driving a beam >>>>> that has higher output than sunlight seems unlikely.
I would use a IR phototransistor at 850nm, something like this:
https://www.ttelectronics.com/TTElectronics/media/ProductFiles/Datasheet/OP505-506-535-705.pdf
Or a photo diode:
https://docs.rs-online.com/9f58/0900766b816d8a09.pdf
Fed from reverse 3.3V and into a transimpedance amplifier to boost the >>>>> signal with bandpass filter.
One can get digital IR detector used in a remote control systems:
https://www.vishay.com/docs/82491/tsop382.pdf
It has AGC, but digital output. I need analog output to be able to zero >>>>> in on the transmitter beam.
I have been looking for IR detectors that has the analog output, not >>>>> just the digital, but have not found any.
If the photodiode detector is subjected to sunlight, I am guessing I >>>>> would need very high gain on the 10kHz modulation frequency to pick up >>>>> the burried signal in the DC from sunlight.
How do I best bias the photo diode for optimum detection of the 10kHz >>>>> signal while being immune to the ambient sunlight?
I have chosen 850nm which seems to be a good wavelength. The spectrum at >>>>> sea level has some dips due to water absorption.
https://sciencetech-inc.com/web/image/49169/Spectrum%20with_out%20absorption.png
Seems like 750nm would be better, since then the IR from the sun is
lower, but does reduced the effective range of the system during
fog/rain. Probably that's why these system do not use 750nm
Other considerations?
You could drive the LED with a square wave, 10 KHz or whatever. The
photodiode could have +DC on one end and the other end can hit a
parallel LC to ground, resonant at 10K.
That takes out the sunlight DC component and adds bandpass filtering.
That's a very nice idea. The Q should not matter much, just as long as
DC is removed.
The photodiode will still be subjected to the high ambient light, but
the gain would be close to zero for the stage after. I would then still
need to be sure the photodiode is never saturated by ambient light.
Just don't fry the photodiode in high light.
So adding a resistance in series with the diode?
Nah, the Johnson noise kills you. It's easier to just calculate or
measure the photocurrent from direct sunlight and design around that.
You only need enough bias to ensure linear operation at high current,
maybe a volt or so.
You will want to put a filter in the second stage to get rid of the
nasty high-frequency noise peak. I usually use a two-pole Sallen-Key
with equal resistor values, which has predictable gain (1.00) and low
component-value sensitivity, and is super simple.
Resist the temptation to do anything floral with the TIA stage, such as
LC or *especially* gyrator filtering. A large inductor is a disaster in
a TIA, because if it doesn't cause instability, it'll still pick up crap >>from every VF motor drive on the block, and deposit it right into the
summing junction, where you really really don't want it.
Small shielded inductors are cheap, and 10 KHz is not a common
switching frequency.
Put the two inductors close together. They will see mostly the same
mag fields, so a couple of resistors added somewhere will cancel the
pickup.
Or add a third, between them, to drive their bottom ends, again
canceling mag field pickup.
Or make each L from a pair, arranged so the pickups cancel.
TV remotes work if you bounce the light off the ceiling in a well-lit
room.
But the acoustic approach would be better. Omni MEMS microphones have built-in amps and cost 20 cents.
On 28-10-2024 20:49, Phil Hobbs wrote:
On 2024-10-27 08:26, Klaus Vestergaard Kragelund wrote:
On 27-10-2024 03:26, john larkin wrote:
On Sun, 27 Oct 2024 02:19:14 +0200, Klaus Vestergaard Kragelund
<klauskvik@hotmail.com> wrote:
Hi
I am working on an IR detector that will guide a robot into a docking >>>>> station.
A IR transmitter on the docking station transmits a beam, and 2 IR
detectors on the robot detects the beam and lets the robot navigate
towards the target. The working distance is a couple of meters.
I need it to be insensitive to ambient light/sunlight.
The IR detectors are placed in a tube, to narrow in the beam angle and >>>>> to avoid sunlight (since it is seldom the sun is actually that low in >>>>> the horizon)
The IR transmitter will be modulated with 10kHz (TBD) frequency, low >>>>> duty cycle. Low duty cycle to be able to drive the LED with high
current, frequency modulated so that the receiver can ignore the
effect
of daylight (DC)
If the LED on the docking station has higher radiant intensity at the >>>>> point of the robot (2 meters away) than possible IR from sunlight,
then
that would be perfect.
Example of transmitter:
https://www.vishay.com/docs/83398/vsmy2850.pdf
Has up to 1000mW/sr. Seems my basic calculation for a 15 degree beam, >>>>> shows less than 10nW/m2, while sunlight has 1W/m2. So driving a beam >>>>> that has higher output than sunlight seems unlikely.
I would use a IR phototransistor at 850nm, something like this:
https://www.ttelectronics.com/TTElectronics/media/ProductFiles/
Datasheet/OP505-506-535-705.pdf
Or a photo diode:
https://docs.rs-online.com/9f58/0900766b816d8a09.pdf
Fed from reverse 3.3V and into a transimpedance amplifier to boost the >>>>> signal with bandpass filter.
One can get digital IR detector used in a remote control systems:
https://www.vishay.com/docs/82491/tsop382.pdf
It has AGC, but digital output. I need analog output to be able to
zero
in on the transmitter beam.
I have been looking for IR detectors that has the analog output, not >>>>> just the digital, but have not found any.
If the photodiode detector is subjected to sunlight, I am guessing I >>>>> would need very high gain on the 10kHz modulation frequency to pick up >>>>> the burried signal in the DC from sunlight.
How do I best bias the photo diode for optimum detection of the 10kHz >>>>> signal while being immune to the ambient sunlight?
I have chosen 850nm which seems to be a good wavelength. The
spectrum at
sea level has some dips due to water absorption.
https://sciencetech-inc.com/web/image/49169/
Spectrum%20with_out%20absorption.png
Seems like 750nm would be better, since then the IR from the sun is
lower, but does reduced the effective range of the system during
fog/rain. Probably that's why these system do not use 750nm
Other considerations?
You could drive the LED with a square wave, 10 KHz or whatever. The
photodiode could have +DC on one end and the other end can hit a
parallel LC to ground, resonant at 10K.
That takes out the sunlight DC component and adds bandpass filtering.
That's a very nice idea. The Q should not matter much, just as long
as DC is removed.
The photodiode will still be subjected to the high ambient light, but
the gain would be close to zero for the stage after. I would then
still need to be sure the photodiode is never saturated by ambient
light.
Just don't fry the photodiode in high light.
So adding a resistance in series with the diode?
Nah, the Johnson noise kills you. It's easier to just calculate or
measure the photocurrent from direct sunlight and design around that.
You only need enough bias to ensure linear operation at high current,
maybe a volt or so.
You will want to put a filter in the second stage to get rid of the
nasty high-frequency noise peak. I usually use a two-pole Sallen-Key
with equal resistor values, which has predictable gain (1.00) and low
component-value sensitivity, and is super simple.
Resist the temptation to do anything floral with the TIA stage, such
as LC or *especially* gyrator filtering. A large inductor is a
disaster in a TIA, because if it doesn't cause instability, it'll
still pick up crap from every VF motor drive on the block, and deposit
it right into the summing junction, where you really really don't want
it.
You don't need a bootstrap at 10 kHz, but a sufficiently carefully
designed DC restore loop can help sometimes. A badly designed one
will trash the SNR. At low frequency, the only way to make a quiet
current source is to put a large voltage across a large resistor. I
usually do that in the emitter circuit of a BJT, to get higher Zout,
but you can also do it barefoot.
The thing is, you're going to be dominated by the shot noise of the DC
restore current unless its resistor is much larger than the feedback
resistor of the TIA. (At high frequency you can use filtering tricks,
but not easily at 10 kHz.)Â Since the DC restore is going to have the
same supply headroom as the TIA, it really doesn't help.
If you pick the TIA's feedback resistance so that the IR signal
produces 50 mV of output, you're in the shot noise limit, at least in
the dark. However, since the sunlight's shot noise is going to be the
limit most of the time, just pick a feedback resistor so the TIA
nearly rails at the worst-case background light level, and see if that
gives you enough SNR to be going on with. If so, AC-couple it into
the second stage and you're done.
If not, you need to reduce the background with a better filter, or
(better) reduce the field of view by using a lens on the receiver, and
increase the signal by using one on the transmitter. You win by the
square of the angular magnification, which can be a fairly startling
number.
Either way, you need to control your detection bandwidth to something
reasonable, and remember that LP filter to get rid of the noise peak!
Sounds like I should hire you in a reviewer, if I get stuck :-)
On 2024-10-28 08:14, piglet wrote:
john larkin <JL@gct.com> wrote:
On Sun, 27 Oct 2024 22:59:59 -0000 (UTC), piglet
<erichpwagner@hotmail.com> wrote:
Klaus Vestergaard Kragelund <klauskvik@hotmail.com> wrote:
On 27-10-2024 13:26, Klaus Vestergaard Kragelund wrote:
On 27-10-2024 03:26, john larkin wrote:
On Sun, 27 Oct 2024 02:19:14 +0200, Klaus Vestergaard Kragelund
<klauskvik@hotmail.com> wrote:
Of course they might be able to reverse the process and have one receiver
on the robot and two emitters on the docking station, a bit like aircraft
VOR
Or like certain radio navigation systems popular in Western Europe, 80
or so years ago. ;)
That's a good example of Horace Darwin's maxim, "Always try it the other
way round", quoted in "Instruments and Experiences" by R. V. Jones.
Jones is one of my technical heroes, and was instrumental in defeating a couple of the aforementioned navigation systems, specifically
"Knickebein" and "X-Geraet", as explained in his book, "The Wizard War" (entitled "Most Secret War" in the UK). Horace Darwin was a grandson of Charles Darwin, and a colleague of Jones's at Aberdeen after the war.
On 2024-10-27 08:26, Klaus Vestergaard Kragelund wrote:
On 27-10-2024 03:26, john larkin wrote:
On Sun, 27 Oct 2024 02:19:14 +0200, Klaus Vestergaard Kragelund
<klauskvik@hotmail.com> wrote:
Hi
I am working on an IR detector that will guide a robot into a docking
station.
A IR transmitter on the docking station transmits a beam, and 2 IR
detectors on the robot detects the beam and lets the robot navigate
towards the target. The working distance is a couple of meters.
I need it to be insensitive to ambient light/sunlight.
The IR detectors are placed in a tube, to narrow in the beam angle and >>>> to avoid sunlight (since it is seldom the sun is actually that low in
the horizon)
The IR transmitter will be modulated with 10kHz (TBD) frequency, low
duty cycle. Low duty cycle to be able to drive the LED with high
current, frequency modulated so that the receiver can ignore the effect >>>> of daylight (DC)
If the LED on the docking station has higher radiant intensity at the
point of the robot (2 meters away) than possible IR from sunlight, then >>>> that would be perfect.
Example of transmitter:
https://www.vishay.com/docs/83398/vsmy2850.pdf
Has up to 1000mW/sr. Seems my basic calculation for a 15 degree beam,
shows less than 10nW/m2, while sunlight has 1W/m2. So driving a beam
that has higher output than sunlight seems unlikely.
I would use a IR phototransistor at 850nm, something like this:
https://www.ttelectronics.com/TTElectronics/media/ProductFiles/Datasheet/OP505-506-535-705.pdf
Or a photo diode:
https://docs.rs-online.com/9f58/0900766b816d8a09.pdf
Fed from reverse 3.3V and into a transimpedance amplifier to boost the >>>> signal with bandpass filter.
One can get digital IR detector used in a remote control systems:
https://www.vishay.com/docs/82491/tsop382.pdf
It has AGC, but digital output. I need analog output to be able to zero >>>> in on the transmitter beam.
I have been looking for IR detectors that has the analog output, not
just the digital, but have not found any.
If the photodiode detector is subjected to sunlight, I am guessing I
would need very high gain on the 10kHz modulation frequency to pick up >>>> the burried signal in the DC from sunlight.
How do I best bias the photo diode for optimum detection of the 10kHz
signal while being immune to the ambient sunlight?
I have chosen 850nm which seems to be a good wavelength. The
spectrum at
sea level has some dips due to water absorption.
https://sciencetech-inc.com/web/image/49169/Spectrum%20with_out%20absorption.png
Seems like 750nm would be better, since then the IR from the sun is
lower, but does reduced the effective range of the system during
fog/rain. Probably that's why these system do not use 750nm
Other considerations?
You could drive the LED with a square wave, 10 KHz or whatever. The
photodiode could have +DC on one end and the other end can hit a
parallel LC to ground, resonant at 10K.
That takes out the sunlight DC component and adds bandpass filtering.
That's a very nice idea. The Q should not matter much, just as long as
DC is removed.
The photodiode will still be subjected to the high ambient light, but
the gain would be close to zero for the stage after. I would then
still need to be sure the photodiode is never saturated by ambient light.
Just don't fry the photodiode in high light.
So adding a resistance in series with the diode?
Nah, the Johnson noise kills you. It's easier to just calculate or
measure the photocurrent from direct sunlight and design around that.
You only need enough bias to ensure linear operation at high current,
maybe a volt or so.
You will want to put a filter in the second stage to get rid of the
nasty high-frequency noise peak. I usually use a two-pole Sallen-Key
with equal resistor values, which has predictable gain (1.00) and low component-value sensitivity, and is super simple.
Resist the temptation to do anything floral with the TIA stage, such as
LC or *especially* gyrator filtering. A large inductor is a disaster in
a TIA, because if it doesn't cause instability, it'll still pick up crap
from every VF motor drive on the block, and deposit it right into the
summing junction, where you really really don't want it.
You don't need a bootstrap at 10 kHz, but a sufficiently carefully
designed DC restore loop can help sometimes. A badly designed one will trash the SNR. At low frequency, the only way to make a quiet current
source is to put a large voltage across a large resistor. I usually do
that in the emitter circuit of a BJT, to get higher Zout, but you can
also do it barefoot.
The thing is, you're going to be dominated by the shot noise of the DC restore current unless its resistor is much larger than the feedback
resistor of the TIA. (At high frequency you can use filtering tricks,
but not easily at 10 kHz.)Â Since the DC restore is going to have the
same supply headroom as the TIA, it really doesn't help.
If you pick the TIA's feedback resistance so that the IR signal produces
50 mV of output, you're in the shot noise limit, at least in the dark. However, since the sunlight's shot noise is going to be the limit most
of the time, just pick a feedback resistor so the TIA nearly rails at
the worst-case background light level, and see if that gives you enough
SNR to be going on with. If so, AC-couple it into the second stage and you're done.
If not, you need to reduce the background with a better filter, or
(better) reduce the field of view by using a lens on the receiver, and increase the signal by using one on the transmitter. You win by the
square of the angular magnification, which can be a fairly startling
number.
Either way, you need to control your detection bandwidth to something reasonable, and remember that LP filter to get rid of the noise peak!
If the chirp arrives at the same time at each mike, the robot is on the
right path, If one is delayed, the robot eases into the that direction
Klaus Vestergaard Kragelund <klauskvik@hotmail.com> wrote:
[...]
If the chirp arrives at the same time at each mike, the robot is on the
right path, If one is delayed, the robot eases into the that direction
If one of the chirps has been reflected from a distant hard surface the
long delay could interfere with the next pulse. Something like that
happened to an early-warning radar sytem when the moon rose and
reflected long-delayed pulses.
A slow pulse rate or a variable one would overcome this.
In LORAN, the carrier was modulated with a specific envelope
(as well as a pulse code pattern) to let the receiver identify
a specific reference point on the carrier. (because multiple
signal sources could be present in a given geographical area)
On 28-10-2024 20:05, john larkin wrote:
On Mon, 28 Oct 2024 11:11:38 +0100, Klaus Vestergaard Kragelund
<klauskvik@hotmail.com> wrote:
On 27-10-2024 18:56, john larkin wrote:
On Sun, 27 Oct 2024 09:03:20 GMT, Jan Panteltje <alien@comet.invalid>Could also be done with a chirp and auto-correlation, although this does >>> not use the phase, but a beacon reference instead
wrote:
On a sunny day (Sun, 27 Oct 2024 02:19:14 +0200) it happened Klaus Vestergaard
Kragelund <klauskvik@hotmail.com> wrote in <vfk0u0$3u9en$1@dont-email.me>:
Hi
I am working on an IR detector that will guide a robot into a docking >>>>>> station.
A IR transmitter on the docking station transmits a beam, and 2 IR >>>>>> detectors on the robot detects the beam and lets the robot navigate >>>>>> towards the target. The working distance is a couple of meters.
I need it to be insensitive to ambient light/sunlight.
I use a cheap camera module to track a light source in H and V direction, and just a simple Microchip PIC : for processing
It can, with some added code, track object forms too, like a cross or maybe a big character.
panteltje.nl/pub/horizontal_IR_target_tracking_4686.avi
those camara modulea are IR sensitive to some extend, sometimes you can remove the IR filter from such modules.
It may be a bit of overkill for your application, but OTOH it can do a lot more.
Mainly designed to detect and follow jet exhaust..
You could uee utrasonics too, maybe even simpler, no sun problem, like a bat.
Cheap electret mikes? or modify some ebay 1 dolalr distance sensors... >>>>> can be used for anti-collision too.
Right. A sonic scheme could measure the phase between two mikes to
determine the direction of the source with high resolution. That could >>>> be an analog multiplier or a bit of code. The amplitudes would be
useful too.
One could compute direction, distance, and velocity almost for free.
No problem with sunlight!
Could that tell the direction of the mother ship?
If the chirp arrives at the same time at each mike, the robot is on the
right path, If one is delayed, the robot eases into the that direction
Three or four omni mems microphones could tell the robot whichI did a design based on a rectangular wire loop, with 4 pickup coils in
direction to go with full 360 degree coverage.
Maybe even estimate range.
a star formation. That configuration could tell the robot how much it
was off directly without using a search pattern.
But, they do not want that, all though it performance very good.
On 2024-10-28 08:14, piglet wrote:
john larkin <JL@gct.com> wrote:
On Sun, 27 Oct 2024 22:59:59 -0000 (UTC), piglet
<erichpwagner@hotmail.com> wrote:
Klaus Vestergaard Kragelund <klauskvik@hotmail.com> wrote:
On 27-10-2024 13:26, Klaus Vestergaard Kragelund wrote:
On 27-10-2024 03:26, john larkin wrote:Actually, wont a simple high pass filter work equally well?
On Sun, 27 Oct 2024 02:19:14 +0200, Klaus Vestergaard Kragelund
<klauskvik@hotmail.com> wrote:
Hi
I am working on an IR detector that will guide a robot into a docking >>>>>>>> station.
A IR transmitter on the docking station transmits a beam, and 2 IR >>>>>>>> detectors on the robot detects the beam and lets the robot navigate >>>>>>>> towards the target. The working distance is a couple of meters. >>>>>>>>
I need it to be insensitive to ambient light/sunlight.
The IR detectors are placed in a tube, to narrow in the beam angle and >>>>>>>> to avoid sunlight (since it is seldom the sun is actually that low in >>>>>>>> the horizon)
The IR transmitter will be modulated with 10kHz (TBD) frequency, low >>>>>>>> duty cycle. Low duty cycle to be able to drive the LED with high >>>>>>>> current, frequency modulated so that the receiver can ignore the effect
of daylight (DC)
If the LED on the docking station has higher radiant intensity at the >>>>>>>> point of the robot (2 meters away) than possible IR from sunlight, then
that would be perfect.
Example of transmitter:
https://www.vishay.com/docs/83398/vsmy2850.pdf
Has up to 1000mW/sr. Seems my basic calculation for a 15 degree beam, >>>>>>>> shows less than 10nW/m2, while sunlight has 1W/m2. So driving a beam >>>>>>>> that has higher output than sunlight seems unlikely.
I would use a IR phototransistor at 850nm, something like this: >>>>>>>>
https://www.ttelectronics.com/TTElectronics/media/ProductFiles/ >>>>>>>> Datasheet/OP505-506-535-705.pdf
Or a photo diode:
https://docs.rs-online.com/9f58/0900766b816d8a09.pdf
Fed from reverse 3.3V and into a transimpedance amplifier to boost the >>>>>>>> signal with bandpass filter.
One can get digital IR detector used in a remote control systems: >>>>>>>>
https://www.vishay.com/docs/82491/tsop382.pdf
It has AGC, but digital output. I need analog output to be able to zero
in on the transmitter beam.
I have been looking for IR detectors that has the analog output, not >>>>>>>> just the digital, but have not found any.
If the photodiode detector is subjected to sunlight, I am guessing I >>>>>>>> would need very high gain on the 10kHz modulation frequency to pick up >>>>>>>> the burried signal in the DC from sunlight.
How do I best bias the photo diode for optimum detection of the 10kHz >>>>>>>> signal while being immune to the ambient sunlight?
I have chosen 850nm which seems to be a good wavelength. The spectrum at
sea level has some dips due to water absorption.
https://sciencetech-inc.com/web/image/49169/
Spectrum%20with_out%20absorption.png
Seems like 750nm would be better, since then the IR from the sun is >>>>>>>> lower, but does reduced the effective range of the system during >>>>>>>> fog/rain. Probably that's why these system do not use 750nm
Other considerations?
You could drive the LED with a square wave, 10 KHz or whatever. The >>>>>>> photodiode could have +DC on one end and the other end can hit a >>>>>>> parallel LC to ground, resonant at 10K.
That takes out the sunlight DC component and adds bandpass filtering. >>>>>>>
That's a very nice idea. The Q should not matter much, just as long as >>>>>> DC is removed.
The photodiode will still be subjected to the high ambient light, but >>>>>> the gain would be close to zero for the stage after. I would then still >>>>>> need to be sure the photodiode is never saturated by ambient light. >>>>>>
Photo diode with bias -> capacitor to gain block....
If you make it part of the bias network yes, a gyrator either a single >>>> transistor or op amp could take the role of inductor.
When you need an inductor, an inductor makes an excellent inductor.
But the dual microphone thing, electret or mems, sounds like a much
better way to go.
Some folk are scared of inductors. 10kHz does mean quite a few milli
henries.
Of course they might be able to reverse the process and have one receiver
on the robot and two emitters on the docking station, a bit like aircraft
VOR
Or like certain radio navigation systems popular in Western Europe, 80
or so years ago. ;)
That's a good example of Horace Darwin's maxim, "Always try it the other
way round", quoted in "Instruments and Experiences" by R. V. Jones.
Jones is one of my technical heroes, and was instrumental in defeating a >couple of the aforementioned navigation systems, specifically
"Knickebein" and "X-Geraet", as explained in his book, "The Wizard War" >(entitled "Most Secret War" in the UK). Horace Darwin was a grandson of >Charles Darwin, and a colleague of Jones's at Aberdeen after the war.
Cheers
Phil Hobbs
On Mon, 28 Oct 2024 20:19:25 -0400, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:
On 2024-10-28 08:14, piglet wrote:
john larkin <JL@gct.com> wrote:
On Sun, 27 Oct 2024 22:59:59 -0000 (UTC), piglet
<erichpwagner@hotmail.com> wrote:
Klaus Vestergaard Kragelund <klauskvik@hotmail.com> wrote:
On 27-10-2024 13:26, Klaus Vestergaard Kragelund wrote:
On 27-10-2024 03:26, john larkin wrote:Actually, wont a simple high pass filter work equally well?
On Sun, 27 Oct 2024 02:19:14 +0200, Klaus Vestergaard Kragelund >>>>>>>> <klauskvik@hotmail.com> wrote:
Hi
I am working on an IR detector that will guide a robot into a docking >>>>>>>>> station.
A IR transmitter on the docking station transmits a beam, and 2 IR >>>>>>>>> detectors on the robot detects the beam and lets the robot navigate >>>>>>>>> towards the target. The working distance is a couple of meters. >>>>>>>>>
I need it to be insensitive to ambient light/sunlight.
The IR detectors are placed in a tube, to narrow in the beam angle and
to avoid sunlight (since it is seldom the sun is actually that low in >>>>>>>>> the horizon)
The IR transmitter will be modulated with 10kHz (TBD) frequency, low >>>>>>>>> duty cycle. Low duty cycle to be able to drive the LED with high >>>>>>>>> current, frequency modulated so that the receiver can ignore the effect
of daylight (DC)
If the LED on the docking station has higher radiant intensity at the >>>>>>>>> point of the robot (2 meters away) than possible IR from sunlight, then
that would be perfect.
Example of transmitter:
https://www.vishay.com/docs/83398/vsmy2850.pdf
Has up to 1000mW/sr. Seems my basic calculation for a 15 degree beam, >>>>>>>>> shows less than 10nW/m2, while sunlight has 1W/m2. So driving a beam >>>>>>>>> that has higher output than sunlight seems unlikely.
I would use a IR phototransistor at 850nm, something like this: >>>>>>>>>
https://www.ttelectronics.com/TTElectronics/media/ProductFiles/ >>>>>>>>> Datasheet/OP505-506-535-705.pdf
Or a photo diode:
https://docs.rs-online.com/9f58/0900766b816d8a09.pdf
Fed from reverse 3.3V and into a transimpedance amplifier to boost the
signal with bandpass filter.
One can get digital IR detector used in a remote control systems: >>>>>>>>>
https://www.vishay.com/docs/82491/tsop382.pdf
It has AGC, but digital output. I need analog output to be able to zero
in on the transmitter beam.
I have been looking for IR detectors that has the analog output, not >>>>>>>>> just the digital, but have not found any.
If the photodiode detector is subjected to sunlight, I am guessing I >>>>>>>>> would need very high gain on the 10kHz modulation frequency to pick up
the burried signal in the DC from sunlight.
How do I best bias the photo diode for optimum detection of the 10kHz >>>>>>>>> signal while being immune to the ambient sunlight?
I have chosen 850nm which seems to be a good wavelength. The spectrum at
sea level has some dips due to water absorption.
https://sciencetech-inc.com/web/image/49169/
Spectrum%20with_out%20absorption.png
Seems like 750nm would be better, since then the IR from the sun is >>>>>>>>> lower, but does reduced the effective range of the system during >>>>>>>>> fog/rain. Probably that's why these system do not use 750nm
Other considerations?
You could drive the LED with a square wave, 10 KHz or whatever. The >>>>>>>> photodiode could have +DC on one end and the other end can hit a >>>>>>>> parallel LC to ground, resonant at 10K.
That takes out the sunlight DC component and adds bandpass filtering. >>>>>>>>
That's a very nice idea. The Q should not matter much, just as long as >>>>>>> DC is removed.
The photodiode will still be subjected to the high ambient light, but >>>>>>> the gain would be close to zero for the stage after. I would then still >>>>>>> need to be sure the photodiode is never saturated by ambient light. >>>>>>>
Photo diode with bias -> capacitor to gain block....
If you make it part of the bias network yes, a gyrator either a single >>>>> transistor or op amp could take the role of inductor.
When you need an inductor, an inductor makes an excellent inductor.
But the dual microphone thing, electret or mems, sounds like a much
better way to go.
Some folk are scared of inductors. 10kHz does mean quite a few milli
henries.
Of course they might be able to reverse the process and have one receiver >>> on the robot and two emitters on the docking station, a bit like aircraft >>> VOR
Or like certain radio navigation systems popular in Western Europe, 80
or so years ago. ;)
That's a good example of Horace Darwin's maxim, "Always try it the other
way round", quoted in "Instruments and Experiences" by R. V. Jones.
Jones is one of my technical heroes, and was instrumental in defeating a
couple of the aforementioned navigation systems, specifically
"Knickebein" and "X-Geraet", as explained in his book, "The Wizard War"
(entitled "Most Secret War" in the UK). Horace Darwin was a grandson of
Charles Darwin, and a colleague of Jones's at Aberdeen after the war.
Cheers
Phil Hobbs
https://www.amazon.com/Instruments-Experiences-Measurement-Instrument-Technology/dp/047191763X
On 2024-10-28 17:10, john larkin wrote:
On Mon, 28 Oct 2024 15:49:30 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
On 2024-10-27 08:26, Klaus Vestergaard Kragelund wrote:
On 27-10-2024 03:26, john larkin wrote:
On Sun, 27 Oct 2024 02:19:14 +0200, Klaus Vestergaard Kragelund
<klauskvik@hotmail.com> wrote:
Hi
I am working on an IR detector that will guide a robot into a docking >>>>>> station.
A IR transmitter on the docking station transmits a beam, and 2 IR >>>>>> detectors on the robot detects the beam and lets the robot navigate >>>>>> towards the target. The working distance is a couple of meters.
I need it to be insensitive to ambient light/sunlight.
The IR detectors are placed in a tube, to narrow in the beam angle and >>>>>> to avoid sunlight (since it is seldom the sun is actually that low in >>>>>> the horizon)
The IR transmitter will be modulated with 10kHz (TBD) frequency, low >>>>>> duty cycle. Low duty cycle to be able to drive the LED with high
current, frequency modulated so that the receiver can ignore the effect >>>>>> of daylight (DC)
If the LED on the docking station has higher radiant intensity at the >>>>>> point of the robot (2 meters away) than possible IR from sunlight, then >>>>>> that would be perfect.
Example of transmitter:
https://www.vishay.com/docs/83398/vsmy2850.pdf
Has up to 1000mW/sr. Seems my basic calculation for a 15 degree beam, >>>>>> shows less than 10nW/m2, while sunlight has 1W/m2. So driving a beam >>>>>> that has higher output than sunlight seems unlikely.
I would use a IR phototransistor at 850nm, something like this:
https://www.ttelectronics.com/TTElectronics/media/ProductFiles/Datasheet/OP505-506-535-705.pdf
Or a photo diode:
https://docs.rs-online.com/9f58/0900766b816d8a09.pdf
Fed from reverse 3.3V and into a transimpedance amplifier to boost the >>>>>> signal with bandpass filter.
One can get digital IR detector used in a remote control systems:
https://www.vishay.com/docs/82491/tsop382.pdf
It has AGC, but digital output. I need analog output to be able to zero >>>>>> in on the transmitter beam.
I have been looking for IR detectors that has the analog output, not >>>>>> just the digital, but have not found any.
If the photodiode detector is subjected to sunlight, I am guessing I >>>>>> would need very high gain on the 10kHz modulation frequency to pick up >>>>>> the burried signal in the DC from sunlight.
How do I best bias the photo diode for optimum detection of the 10kHz >>>>>> signal while being immune to the ambient sunlight?
I have chosen 850nm which seems to be a good wavelength. The spectrum at >>>>>> sea level has some dips due to water absorption.
https://sciencetech-inc.com/web/image/49169/Spectrum%20with_out%20absorption.png
Seems like 750nm would be better, since then the IR from the sun is >>>>>> lower, but does reduced the effective range of the system during
fog/rain. Probably that's why these system do not use 750nm
Other considerations?
You could drive the LED with a square wave, 10 KHz or whatever. The
photodiode could have +DC on one end and the other end can hit a
parallel LC to ground, resonant at 10K.
That takes out the sunlight DC component and adds bandpass filtering. >>>>>
That's a very nice idea. The Q should not matter much, just as long as >>>> DC is removed.
The photodiode will still be subjected to the high ambient light, but
the gain would be close to zero for the stage after. I would then still >>>> need to be sure the photodiode is never saturated by ambient light.
Just don't fry the photodiode in high light.
So adding a resistance in series with the diode?
Nah, the Johnson noise kills you. It's easier to just calculate or
measure the photocurrent from direct sunlight and design around that.
You only need enough bias to ensure linear operation at high current,
maybe a volt or so.
You will want to put a filter in the second stage to get rid of the
nasty high-frequency noise peak. I usually use a two-pole Sallen-Key
with equal resistor values, which has predictable gain (1.00) and low
component-value sensitivity, and is super simple.
Resist the temptation to do anything floral with the TIA stage, such as
LC or *especially* gyrator filtering. A large inductor is a disaster in >>> a TIA, because if it doesn't cause instability, it'll still pick up crap >>>from every VF motor drive on the block, and deposit it right into the
summing junction, where you really really don't want it.
Small shielded inductors are cheap, and 10 KHz is not a common
switching frequency.
VFDs put out large amounts of magnetic crap from the hundreds of hertz
on up. I saw your VFD EMI filters at your Otis St shop. ;)
Put the two inductors close together. They will see mostly the same
mag fields, so a couple of resistors added somewhere will cancel the
pickup.
Or add a third, between them, to drive their bottom ends, again
canceling mag field pickup.
Or make each L from a pair, arranged so the pickups cancel.
Or just do three lines of algebra to pick the right resistor value, AC >couple, and be done.
TV remotes work if you bounce the light off the ceiling in a well-lit
room.
"Well-lit", as in probably 1000 lumens of LED or fluorescent light,
which has very little output in the >700 nm region.
But the acoustic approach would be better. Omni MEMS microphones have
built-in amps and cost 20 cents.
There are lots of imponderables there, though. For instance, on account
of the slow speed of sound in air, a 1 m/s breeze (2.2 mph) will make
the apparent direction of the acoustic source move by 3 mrad.
Cheers
Phil Hobbs
On Mon, 28 Oct 2024 20:31:14 -0400, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:
On 2024-10-28 17:10, john larkin wrote:
On Mon, 28 Oct 2024 15:49:30 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
On 2024-10-27 08:26, Klaus Vestergaard Kragelund wrote:
On 27-10-2024 03:26, john larkin wrote:
On Sun, 27 Oct 2024 02:19:14 +0200, Klaus Vestergaard Kragelund
<klauskvik@hotmail.com> wrote:
Hi
I am working on an IR detector that will guide a robot into a docking >>>>>>> station.
A IR transmitter on the docking station transmits a beam, and 2 IR >>>>>>> detectors on the robot detects the beam and lets the robot navigate >>>>>>> towards the target. The working distance is a couple of meters.
I need it to be insensitive to ambient light/sunlight.
The IR detectors are placed in a tube, to narrow in the beam angle and >>>>>>> to avoid sunlight (since it is seldom the sun is actually that low in >>>>>>> the horizon)
The IR transmitter will be modulated with 10kHz (TBD) frequency, low >>>>>>> duty cycle. Low duty cycle to be able to drive the LED with high >>>>>>> current, frequency modulated so that the receiver can ignore the effect >>>>>>> of daylight (DC)
If the LED on the docking station has higher radiant intensity at the >>>>>>> point of the robot (2 meters away) than possible IR from sunlight, then >>>>>>> that would be perfect.
Example of transmitter:
https://www.vishay.com/docs/83398/vsmy2850.pdf
Has up to 1000mW/sr. Seems my basic calculation for a 15 degree beam, >>>>>>> shows less than 10nW/m2, while sunlight has 1W/m2. So driving a beam >>>>>>> that has higher output than sunlight seems unlikely.
I would use a IR phototransistor at 850nm, something like this:
https://www.ttelectronics.com/TTElectronics/media/ProductFiles/Datasheet/OP505-506-535-705.pdf
Or a photo diode:
https://docs.rs-online.com/9f58/0900766b816d8a09.pdf
Fed from reverse 3.3V and into a transimpedance amplifier to boost the >>>>>>> signal with bandpass filter.
One can get digital IR detector used in a remote control systems: >>>>>>>
https://www.vishay.com/docs/82491/tsop382.pdf
It has AGC, but digital output. I need analog output to be able to zero >>>>>>> in on the transmitter beam.
I have been looking for IR detectors that has the analog output, not >>>>>>> just the digital, but have not found any.
If the photodiode detector is subjected to sunlight, I am guessing I >>>>>>> would need very high gain on the 10kHz modulation frequency to pick up >>>>>>> the burried signal in the DC from sunlight.
How do I best bias the photo diode for optimum detection of the 10kHz >>>>>>> signal while being immune to the ambient sunlight?
I have chosen 850nm which seems to be a good wavelength. The spectrum at
sea level has some dips due to water absorption.
https://sciencetech-inc.com/web/image/49169/Spectrum%20with_out%20absorption.png
Seems like 750nm would be better, since then the IR from the sun is >>>>>>> lower, but does reduced the effective range of the system during >>>>>>> fog/rain. Probably that's why these system do not use 750nm
Other considerations?
You could drive the LED with a square wave, 10 KHz or whatever. The >>>>>> photodiode could have +DC on one end and the other end can hit a
parallel LC to ground, resonant at 10K.
That takes out the sunlight DC component and adds bandpass filtering. >>>>>>
That's a very nice idea. The Q should not matter much, just as long as >>>>> DC is removed.
The photodiode will still be subjected to the high ambient light, but >>>>> the gain would be close to zero for the stage after. I would then still >>>>> need to be sure the photodiode is never saturated by ambient light.
Just don't fry the photodiode in high light.
So adding a resistance in series with the diode?
Nah, the Johnson noise kills you. It's easier to just calculate or
measure the photocurrent from direct sunlight and design around that.
You only need enough bias to ensure linear operation at high current,
maybe a volt or so.
You will want to put a filter in the second stage to get rid of the
nasty high-frequency noise peak. I usually use a two-pole Sallen-Key
with equal resistor values, which has predictable gain (1.00) and low
component-value sensitivity, and is super simple.
Resist the temptation to do anything floral with the TIA stage, such as >>>> LC or *especially* gyrator filtering. A large inductor is a disaster in >>>> a TIA, because if it doesn't cause instability, it'll still pick up crap >>>> from every VF motor drive on the block, and deposit it right into the
summing junction, where you really really don't want it.
Small shielded inductors are cheap, and 10 KHz is not a common
switching frequency.
VFDs put out large amounts of magnetic crap from the hundreds of hertz
on up. I saw your VFD EMI filters at your Otis St shop. ;)
That was conducted EMI. 20 volt spikes everywhere on the top floor.
Mag fields drop rapidly with distance, 3rd power or something.
Put the two inductors close together. They will see mostly the same
mag fields, so a couple of resistors added somewhere will cancel the
pickup.
Or add a third, between them, to drive their bottom ends, again
canceling mag field pickup.
Or make each L from a pair, arranged so the pickups cancel.
Or just do three lines of algebra to pick the right resistor value, AC
couple, and be done.
TV remotes work if you bounce the light off the ceiling in a well-lit
room.
"Well-lit", as in probably 1000 lumens of LED or fluorescent light,
which has very little output in the >700 nm region.
But the acoustic approach would be better. Omni MEMS microphones have
built-in amps and cost 20 cents.
There are lots of imponderables there, though. For instance, on account
of the slow speed of sound in air, a 1 m/s breeze (2.2 mph) will make
the apparent direction of the acoustic source move by 3 mrad.
It's homing into the mother ship so a breeze will very slightly curve
the path.
You're an optics guy, so maybe don't like the sound thing.
john larkin <jl@glen--canyon.com> wrote:
On Mon, 28 Oct 2024 20:31:14 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
On 2024-10-28 17:10, john larkin wrote:
On Mon, 28 Oct 2024 15:49:30 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
On 2024-10-27 08:26, Klaus Vestergaard Kragelund wrote:
On 27-10-2024 03:26, john larkin wrote:
On Sun, 27 Oct 2024 02:19:14 +0200, Klaus Vestergaard Kragelund
<klauskvik@hotmail.com> wrote:
Hi
I am working on an IR detector that will guide a robot into a docking >>>>>>>> station.
A IR transmitter on the docking station transmits a beam, and 2 IR >>>>>>>> detectors on the robot detects the beam and lets the robot navigate >>>>>>>> towards the target. The working distance is a couple of meters. >>>>>>>>
I need it to be insensitive to ambient light/sunlight.
The IR detectors are placed in a tube, to narrow in the beam angle and >>>>>>>> to avoid sunlight (since it is seldom the sun is actually that low in >>>>>>>> the horizon)
The IR transmitter will be modulated with 10kHz (TBD) frequency, low >>>>>>>> duty cycle. Low duty cycle to be able to drive the LED with high >>>>>>>> current, frequency modulated so that the receiver can ignore the effect
of daylight (DC)
If the LED on the docking station has higher radiant intensity at the >>>>>>>> point of the robot (2 meters away) than possible IR from sunlight, then
that would be perfect.
Example of transmitter:
https://www.vishay.com/docs/83398/vsmy2850.pdf
Has up to 1000mW/sr. Seems my basic calculation for a 15 degree beam, >>>>>>>> shows less than 10nW/m2, while sunlight has 1W/m2. So driving a beam >>>>>>>> that has higher output than sunlight seems unlikely.
I would use a IR phototransistor at 850nm, something like this: >>>>>>>>
https://www.ttelectronics.com/TTElectronics/media/ProductFiles/Datasheet/OP505-506-535-705.pdf
Or a photo diode:
https://docs.rs-online.com/9f58/0900766b816d8a09.pdf
Fed from reverse 3.3V and into a transimpedance amplifier to boost the >>>>>>>> signal with bandpass filter.
One can get digital IR detector used in a remote control systems: >>>>>>>>
https://www.vishay.com/docs/82491/tsop382.pdf
It has AGC, but digital output. I need analog output to be able to zero
in on the transmitter beam.
I have been looking for IR detectors that has the analog output, not >>>>>>>> just the digital, but have not found any.
If the photodiode detector is subjected to sunlight, I am guessing I >>>>>>>> would need very high gain on the 10kHz modulation frequency to pick up >>>>>>>> the burried signal in the DC from sunlight.
How do I best bias the photo diode for optimum detection of the 10kHz >>>>>>>> signal while being immune to the ambient sunlight?
I have chosen 850nm which seems to be a good wavelength. The spectrum at
sea level has some dips due to water absorption.
https://sciencetech-inc.com/web/image/49169/Spectrum%20with_out%20absorption.png
Seems like 750nm would be better, since then the IR from the sun is >>>>>>>> lower, but does reduced the effective range of the system during >>>>>>>> fog/rain. Probably that's why these system do not use 750nm
Other considerations?
You could drive the LED with a square wave, 10 KHz or whatever. The >>>>>>> photodiode could have +DC on one end and the other end can hit a >>>>>>> parallel LC to ground, resonant at 10K.
That takes out the sunlight DC component and adds bandpass filtering. >>>>>>>
That's a very nice idea. The Q should not matter much, just as long as >>>>>> DC is removed.
The photodiode will still be subjected to the high ambient light, but >>>>>> the gain would be close to zero for the stage after. I would then still >>>>>> need to be sure the photodiode is never saturated by ambient light. >>>>>>
Just don't fry the photodiode in high light.
So adding a resistance in series with the diode?
Nah, the Johnson noise kills you. It's easier to just calculate or
measure the photocurrent from direct sunlight and design around that. >>>>> You only need enough bias to ensure linear operation at high current, >>>>> maybe a volt or so.
You will want to put a filter in the second stage to get rid of the
nasty high-frequency noise peak. I usually use a two-pole Sallen-Key >>>>> with equal resistor values, which has predictable gain (1.00) and low >>>>> component-value sensitivity, and is super simple.
Resist the temptation to do anything floral with the TIA stage, such as >>>>> LC or *especially* gyrator filtering. A large inductor is a disaster in >>>>> a TIA, because if it doesn't cause instability, it'll still pick up crap >>>>> from every VF motor drive on the block, and deposit it right into the >>>>> summing junction, where you really really don't want it.
Small shielded inductors are cheap, and 10 KHz is not a common
switching frequency.
VFDs put out large amounts of magnetic crap from the hundreds of hertz
on up. I saw your VFD EMI filters at your Otis St shop. ;)
That was conducted EMI. 20 volt spikes everywhere on the top floor.
Mag fields drop rapidly with distance, 3rd power or something.
Put the two inductors close together. They will see mostly the same
mag fields, so a couple of resistors added somewhere will cancel the
pickup.
Or add a third, between them, to drive their bottom ends, again
canceling mag field pickup.
Or make each L from a pair, arranged so the pickups cancel.
Or just do three lines of algebra to pick the right resistor value, AC
couple, and be done.
TV remotes work if you bounce the light off the ceiling in a well-lit
room.
"Well-lit", as in probably 1000 lumens of LED or fluorescent light,
which has very little output in the >700 nm region.
But the acoustic approach would be better. Omni MEMS microphones have
built-in amps and cost 20 cents.
There are lots of imponderables there, though. For instance, on account >>> of the slow speed of sound in air, a 1 m/s breeze (2.2 mph) will make
the apparent direction of the acoustic source move by 3 mrad.
It's homing into the mother ship so a breeze will very slightly curve
the path.
You're an optics guy, so maybe don't like the sound thing.
Hidebound prejudice is the only possible explanation. ;)
Cheers
Phil Hobbs
(I don’t necessarily dislike the sound idea, but it’s more of a science >project than the LED approach. )
On 29/10/2024 17:26, john larkin wrote:
On Tue, 29 Oct 2024 17:02:02 -0000 (UTC), Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
john larkin <jl@glen--canyon.com> wrote:
On Mon, 28 Oct 2024 20:31:14 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
On 2024-10-28 17:10, john larkin wrote:
On Mon, 28 Oct 2024 15:49:30 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
On 2024-10-27 08:26, Klaus Vestergaard Kragelund wrote:
On 27-10-2024 03:26, john larkin wrote:
On Sun, 27 Oct 2024 02:19:14 +0200, Klaus Vestergaard Kragelund >>>>>>>>> <klauskvik@hotmail.com> wrote:
Hi
I am working on an IR detector that will guide a robot into a docking
station.
A IR transmitter on the docking station transmits a beam, and 2 IR >>>>>>>>>> detectors on the robot detects the beam and lets the robot navigate >>>>>>>>>> towards the target. The working distance is a couple of meters. >>>>>>>>>>
I need it to be insensitive to ambient light/sunlight.
The IR detectors are placed in a tube, to narrow in the beam angle and
to avoid sunlight (since it is seldom the sun is actually that low in
the horizon)
The IR transmitter will be modulated with 10kHz (TBD) frequency, low >>>>>>>>>> duty cycle. Low duty cycle to be able to drive the LED with high >>>>>>>>>> current, frequency modulated so that the receiver can ignore the effect
of daylight (DC)
If the LED on the docking station has higher radiant intensity at the
point of the robot (2 meters away) than possible IR from sunlight, then
that would be perfect.
Example of transmitter:
https://www.vishay.com/docs/83398/vsmy2850.pdf
Has up to 1000mW/sr. Seems my basic calculation for a 15 degree beam,
shows less than 10nW/m2, while sunlight has 1W/m2. So driving a beam >>>>>>>>>> that has higher output than sunlight seems unlikely.
I would use a IR phototransistor at 850nm, something like this: >>>>>>>>>>
https://www.ttelectronics.com/TTElectronics/media/ProductFiles/Datasheet/OP505-506-535-705.pdf
Or a photo diode:
https://docs.rs-online.com/9f58/0900766b816d8a09.pdf
Fed from reverse 3.3V and into a transimpedance amplifier to boost the
signal with bandpass filter.
One can get digital IR detector used in a remote control systems: >>>>>>>>>>
https://www.vishay.com/docs/82491/tsop382.pdf
It has AGC, but digital output. I need analog output to be able to zero
in on the transmitter beam.
I have been looking for IR detectors that has the analog output, not >>>>>>>>>> just the digital, but have not found any.
If the photodiode detector is subjected to sunlight, I am guessing I >>>>>>>>>> would need very high gain on the 10kHz modulation frequency to pick up
the burried signal in the DC from sunlight.
How do I best bias the photo diode for optimum detection of the 10kHz
signal while being immune to the ambient sunlight?
I have chosen 850nm which seems to be a good wavelength. The spectrum at
sea level has some dips due to water absorption.
https://sciencetech-inc.com/web/image/49169/Spectrum%20with_out%20absorption.png
Seems like 750nm would be better, since then the IR from the sun is >>>>>>>>>> lower, but does reduced the effective range of the system during >>>>>>>>>> fog/rain. Probably that's why these system do not use 750nm >>>>>>>>>>
Other considerations?
You could drive the LED with a square wave, 10 KHz or whatever. The >>>>>>>>> photodiode could have +DC on one end and the other end can hit a >>>>>>>>> parallel LC to ground, resonant at 10K.
That takes out the sunlight DC component and adds bandpass filtering. >>>>>>>>>
That's a very nice idea. The Q should not matter much, just as long as >>>>>>>> DC is removed.
The photodiode will still be subjected to the high ambient light, but >>>>>>>> the gain would be close to zero for the stage after. I would then still
need to be sure the photodiode is never saturated by ambient light. >>>>>>>>
Just don't fry the photodiode in high light.
So adding a resistance in series with the diode?
Nah, the Johnson noise kills you. It's easier to just calculate or >>>>>>> measure the photocurrent from direct sunlight and design around that. >>>>>>> You only need enough bias to ensure linear operation at high current, >>>>>>> maybe a volt or so.
You will want to put a filter in the second stage to get rid of the >>>>>>> nasty high-frequency noise peak. I usually use a two-pole Sallen-Key >>>>>>> with equal resistor values, which has predictable gain (1.00) and low >>>>>>> component-value sensitivity, and is super simple.
Resist the temptation to do anything floral with the TIA stage, such as >>>>>>> LC or *especially* gyrator filtering. A large inductor is a disaster in
a TIA, because if it doesn't cause instability, it'll still pick up crap
from every VF motor drive on the block, and deposit it right into the >>>>>>> summing junction, where you really really don't want it.
Small shielded inductors are cheap, and 10 KHz is not a common
switching frequency.
VFDs put out large amounts of magnetic crap from the hundreds of hertz >>>>> on up. I saw your VFD EMI filters at your Otis St shop. ;)
That was conducted EMI. 20 volt spikes everywhere on the top floor.
Mag fields drop rapidly with distance, 3rd power or something.
Put the two inductors close together. They will see mostly the same >>>>>> mag fields, so a couple of resistors added somewhere will cancel the >>>>>> pickup.
Or add a third, between them, to drive their bottom ends, again
canceling mag field pickup.
Or make each L from a pair, arranged so the pickups cancel.
Or just do three lines of algebra to pick the right resistor value, AC >>>>> couple, and be done.
TV remotes work if you bounce the light off the ceiling in a well-lit >>>>>> room.
"Well-lit", as in probably 1000 lumens of LED or fluorescent light,
which has very little output in the >700 nm region.
But the acoustic approach would be better. Omni MEMS microphones have >>>>>> built-in amps and cost 20 cents.
There are lots of imponderables there, though. For instance, on account >>>>> of the slow speed of sound in air, a 1 m/s breeze (2.2 mph) will make >>>>> the apparent direction of the acoustic source move by 3 mrad.
It's homing into the mother ship so a breeze will very slightly curve
the path.
You're an optics guy, so maybe don't like the sound thing.
Hidebound prejudice is the only possible explanation. ;)
Cheers
Phil Hobbs
(I don’t necessarily dislike the sound idea, but it’s more of a science
project than the LED approach. )
Think so? A quick experiment would be easy. Two MEMS mikes would feed
an oscilloscope directly. No inductors or TIAs or filters needed. One
could trigger the scope from the source and signal average for extra
fun.
The phase difference between two microphones would be a great
direction sensor. This would be so easy in production, a couple of
surface-mout MEMS mikes on a PC board.
You would need more than two microphones to get unambiguous results.
John
On Tue, 29 Oct 2024 17:31:03 +0000, John R Walliker
<jrwalliker@gmail.com> wrote:
On 29/10/2024 17:26, john larkin wrote:
On Tue, 29 Oct 2024 17:02:02 -0000 (UTC), Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
john larkin <jl@glen--canyon.com> wrote:
On Mon, 28 Oct 2024 20:31:14 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
On 2024-10-28 17:10, john larkin wrote:
On Mon, 28 Oct 2024 15:49:30 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
On 2024-10-27 08:26, Klaus Vestergaard Kragelund wrote:
On 27-10-2024 03:26, john larkin wrote:
On Sun, 27 Oct 2024 02:19:14 +0200, Klaus Vestergaard Kragelund >>>>>>>>>> <klauskvik@hotmail.com> wrote:
Hi
I am working on an IR detector that will guide a robot into a docking
station.
A IR transmitter on the docking station transmits a beam, and 2 IR >>>>>>>>>>> detectors on the robot detects the beam and lets the robot navigate >>>>>>>>>>> towards the target. The working distance is a couple of meters. >>>>>>>>>>>
I need it to be insensitive to ambient light/sunlight.
The IR detectors are placed in a tube, to narrow in the beam angle and
to avoid sunlight (since it is seldom the sun is actually that low in
the horizon)
The IR transmitter will be modulated with 10kHz (TBD) frequency, low
duty cycle. Low duty cycle to be able to drive the LED with high >>>>>>>>>>> current, frequency modulated so that the receiver can ignore the effect
of daylight (DC)
If the LED on the docking station has higher radiant intensity at the
point of the robot (2 meters away) than possible IR from sunlight, then
that would be perfect.
Example of transmitter:
https://www.vishay.com/docs/83398/vsmy2850.pdf
Has up to 1000mW/sr. Seems my basic calculation for a 15 degree beam,
shows less than 10nW/m2, while sunlight has 1W/m2. So driving a beam
that has higher output than sunlight seems unlikely.
I would use a IR phototransistor at 850nm, something like this: >>>>>>>>>>>
https://www.ttelectronics.com/TTElectronics/media/ProductFiles/Datasheet/OP505-506-535-705.pdf
Or a photo diode:
https://docs.rs-online.com/9f58/0900766b816d8a09.pdf
Fed from reverse 3.3V and into a transimpedance amplifier to boost the
signal with bandpass filter.
One can get digital IR detector used in a remote control systems: >>>>>>>>>>>
https://www.vishay.com/docs/82491/tsop382.pdf
It has AGC, but digital output. I need analog output to be able to zero
in on the transmitter beam.
I have been looking for IR detectors that has the analog output, not
just the digital, but have not found any.
If the photodiode detector is subjected to sunlight, I am guessing I
would need very high gain on the 10kHz modulation frequency to pick up
the burried signal in the DC from sunlight.
How do I best bias the photo diode for optimum detection of the 10kHz
signal while being immune to the ambient sunlight?
I have chosen 850nm which seems to be a good wavelength. The spectrum at
sea level has some dips due to water absorption.
https://sciencetech-inc.com/web/image/49169/Spectrum%20with_out%20absorption.png
Seems like 750nm would be better, since then the IR from the sun is >>>>>>>>>>> lower, but does reduced the effective range of the system during >>>>>>>>>>> fog/rain. Probably that's why these system do not use 750nm >>>>>>>>>>>
Other considerations?
You could drive the LED with a square wave, 10 KHz or whatever. The >>>>>>>>>> photodiode could have +DC on one end and the other end can hit a >>>>>>>>>> parallel LC to ground, resonant at 10K.
That takes out the sunlight DC component and adds bandpass filtering.
That's a very nice idea. The Q should not matter much, just as long as
DC is removed.
The photodiode will still be subjected to the high ambient light, but >>>>>>>>> the gain would be close to zero for the stage after. I would then still
need to be sure the photodiode is never saturated by ambient light. >>>>>>>>>
Just don't fry the photodiode in high light.
So adding a resistance in series with the diode?
Nah, the Johnson noise kills you. It's easier to just calculate or >>>>>>>> measure the photocurrent from direct sunlight and design around that. >>>>>>>> You only need enough bias to ensure linear operation at high current, >>>>>>>> maybe a volt or so.
You will want to put a filter in the second stage to get rid of the >>>>>>>> nasty high-frequency noise peak. I usually use a two-pole Sallen-Key >>>>>>>> with equal resistor values, which has predictable gain (1.00) and low >>>>>>>> component-value sensitivity, and is super simple.
Resist the temptation to do anything floral with the TIA stage, such as
LC or *especially* gyrator filtering. A large inductor is a disaster in
a TIA, because if it doesn't cause instability, it'll still pick up crap
from every VF motor drive on the block, and deposit it right into the >>>>>>>> summing junction, where you really really don't want it.
Small shielded inductors are cheap, and 10 KHz is not a common
switching frequency.
VFDs put out large amounts of magnetic crap from the hundreds of hertz >>>>>> on up. I saw your VFD EMI filters at your Otis St shop. ;)
That was conducted EMI. 20 volt spikes everywhere on the top floor.
Mag fields drop rapidly with distance, 3rd power or something.
Put the two inductors close together. They will see mostly the same >>>>>>> mag fields, so a couple of resistors added somewhere will cancel the >>>>>>> pickup.
Or add a third, between them, to drive their bottom ends, again
canceling mag field pickup.
Or make each L from a pair, arranged so the pickups cancel.
Or just do three lines of algebra to pick the right resistor value, AC >>>>>> couple, and be done.
TV remotes work if you bounce the light off the ceiling in a well-lit >>>>>>> room.
"Well-lit", as in probably 1000 lumens of LED or fluorescent light, >>>>>> which has very little output in the >700 nm region.
But the acoustic approach would be better. Omni MEMS microphones have >>>>>>> built-in amps and cost 20 cents.
There are lots of imponderables there, though. For instance, on account >>>>>> of the slow speed of sound in air, a 1 m/s breeze (2.2 mph) will make >>>>>> the apparent direction of the acoustic source move by 3 mrad.
It's homing into the mother ship so a breeze will very slightly curve >>>>> the path.
You're an optics guy, so maybe don't like the sound thing.
Hidebound prejudice is the only possible explanation. ;)
Cheers
Phil Hobbs
(I donÂ’t necessarily dislike the sound idea, but itÂ’s more of a science >>>> project than the LED approach. )
Think so? A quick experiment would be easy. Two MEMS mikes would feed
an oscilloscope directly. No inductors or TIAs or filters needed. One
could trigger the scope from the source and signal average for extra
fun.
The phase difference between two microphones would be a great
direction sensor. This would be so easy in production, a couple of
surface-mout MEMS mikes on a PC board.
You would need more than two microphones to get unambiguous results.
John
It would be better than two photodiodes in black tubes.
Three or four mikes would give 360 degree sensing.
As I understood the problem, the robot is probably pointing at the
mother ship, and just needs to be guided the final few feet.
So simple. Some engineers don't like simple.
Hi
I am working on an IR detector that will guide a robot into a docking station.
john larkin <jl@glen--canyon.com> wrote:
On Tue, 29 Oct 2024 17:31:03 +0000, John R Walliker
<jrwalliker@gmail.com> wrote:
On 29/10/2024 17:26, john larkin wrote:
On Tue, 29 Oct 2024 17:02:02 -0000 (UTC), Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
john larkin <jl@glen--canyon.com> wrote:
On Mon, 28 Oct 2024 20:31:14 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
On 2024-10-28 17:10, john larkin wrote:
On Mon, 28 Oct 2024 15:49:30 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
On 2024-10-27 08:26, Klaus Vestergaard Kragelund wrote:
On 27-10-2024 03:26, john larkin wrote:
On Sun, 27 Oct 2024 02:19:14 +0200, Klaus Vestergaard Kragelund >>>>>>>>>>> <klauskvik@hotmail.com> wrote:
Hi
I am working on an IR detector that will guide a robot into a docking
station.
A IR transmitter on the docking station transmits a beam, and 2 IR >>>>>>>>>>>> detectors on the robot detects the beam and lets the robot navigate
towards the target. The working distance is a couple of meters. >>>>>>>>>>>>
I need it to be insensitive to ambient light/sunlight. >>>>>>>>>>>>
The IR detectors are placed in a tube, to narrow in the beam angle and
to avoid sunlight (since it is seldom the sun is actually that low in
the horizon)
The IR transmitter will be modulated with 10kHz (TBD) frequency, low
duty cycle. Low duty cycle to be able to drive the LED with high >>>>>>>>>>>> current, frequency modulated so that the receiver can ignore the effect
of daylight (DC)
If the LED on the docking station has higher radiant intensity at the
point of the robot (2 meters away) than possible IR from sunlight, then
that would be perfect.
Example of transmitter:
https://www.vishay.com/docs/83398/vsmy2850.pdf
Has up to 1000mW/sr. Seems my basic calculation for a 15 degree beam,
shows less than 10nW/m2, while sunlight has 1W/m2. So driving a beam
that has higher output than sunlight seems unlikely.
I would use a IR phototransistor at 850nm, something like this: >>>>>>>>>>>>
https://www.ttelectronics.com/TTElectronics/media/ProductFiles/Datasheet/OP505-506-535-705.pdf
Or a photo diode:
https://docs.rs-online.com/9f58/0900766b816d8a09.pdf
Fed from reverse 3.3V and into a transimpedance amplifier to boost the
signal with bandpass filter.
One can get digital IR detector used in a remote control systems: >>>>>>>>>>>>
https://www.vishay.com/docs/82491/tsop382.pdf
It has AGC, but digital output. I need analog output to be able to zero
in on the transmitter beam.
I have been looking for IR detectors that has the analog output, not
just the digital, but have not found any.
If the photodiode detector is subjected to sunlight, I am guessing I
would need very high gain on the 10kHz modulation frequency to pick up
the burried signal in the DC from sunlight.
How do I best bias the photo diode for optimum detection of the 10kHz
signal while being immune to the ambient sunlight?
I have chosen 850nm which seems to be a good wavelength. The spectrum at
sea level has some dips due to water absorption.
https://sciencetech-inc.com/web/image/49169/Spectrum%20with_out%20absorption.png
Seems like 750nm would be better, since then the IR from the sun is
lower, but does reduced the effective range of the system during >>>>>>>>>>>> fog/rain. Probably that's why these system do not use 750nm >>>>>>>>>>>>
Other considerations?
You could drive the LED with a square wave, 10 KHz or whatever. The >>>>>>>>>>> photodiode could have +DC on one end and the other end can hit a >>>>>>>>>>> parallel LC to ground, resonant at 10K.
That takes out the sunlight DC component and adds bandpass filtering.
That's a very nice idea. The Q should not matter much, just as long as
DC is removed.
The photodiode will still be subjected to the high ambient light, but
the gain would be close to zero for the stage after. I would then still
need to be sure the photodiode is never saturated by ambient light. >>>>>>>>>>
Just don't fry the photodiode in high light.
So adding a resistance in series with the diode?
Nah, the Johnson noise kills you. It's easier to just calculate or >>>>>>>>> measure the photocurrent from direct sunlight and design around that. >>>>>>>>> You only need enough bias to ensure linear operation at high current, >>>>>>>>> maybe a volt or so.
You will want to put a filter in the second stage to get rid of the >>>>>>>>> nasty high-frequency noise peak. I usually use a two-pole Sallen-Key >>>>>>>>> with equal resistor values, which has predictable gain (1.00) and low >>>>>>>>> component-value sensitivity, and is super simple.
Resist the temptation to do anything floral with the TIA stage, such as
LC or *especially* gyrator filtering. A large inductor is a disaster in
a TIA, because if it doesn't cause instability, it'll still pick up crap
from every VF motor drive on the block, and deposit it right into the >>>>>>>>> summing junction, where you really really don't want it.
Small shielded inductors are cheap, and 10 KHz is not a common >>>>>>>> switching frequency.
VFDs put out large amounts of magnetic crap from the hundreds of hertz >>>>>>> on up. I saw your VFD EMI filters at your Otis St shop. ;)
That was conducted EMI. 20 volt spikes everywhere on the top floor. >>>>>> Mag fields drop rapidly with distance, 3rd power or something.
Put the two inductors close together. They will see mostly the same >>>>>>>> mag fields, so a couple of resistors added somewhere will cancel the >>>>>>>> pickup.
Or add a third, between them, to drive their bottom ends, again >>>>>>>> canceling mag field pickup.
Or make each L from a pair, arranged so the pickups cancel.
Or just do three lines of algebra to pick the right resistor value, AC >>>>>>> couple, and be done.
TV remotes work if you bounce the light off the ceiling in a well-lit >>>>>>>> room.
"Well-lit", as in probably 1000 lumens of LED or fluorescent light, >>>>>>> which has very little output in the >700 nm region.
But the acoustic approach would be better. Omni MEMS microphones have >>>>>>>> built-in amps and cost 20 cents.
There are lots of imponderables there, though. For instance, on account
of the slow speed of sound in air, a 1 m/s breeze (2.2 mph) will make >>>>>>> the apparent direction of the acoustic source move by 3 mrad.
It's homing into the mother ship so a breeze will very slightly curve >>>>>> the path.
You're an optics guy, so maybe don't like the sound thing.
Hidebound prejudice is the only possible explanation. ;)
Cheers
Phil Hobbs
(I don?t necessarily dislike the sound idea, but it?s more of a science >>>>> project than the LED approach. )
Think so? A quick experiment would be easy. Two MEMS mikes would feed
an oscilloscope directly. No inductors or TIAs or filters needed. One
could trigger the scope from the source and signal average for extra
fun.
The phase difference between two microphones would be a great
direction sensor. This would be so easy in production, a couple of
surface-mout MEMS mikes on a PC board.
You would need more than two microphones to get unambiguous results.
John
It would be better than two photodiodes in black tubes.
Maybe so. Depends on the numbers.
Some of them actually have to build the gizmo that we’re all busily opining >about.
Three or four mikes would give 360 degree sensing.
As I understood the problem, the robot is probably pointing at the
mother ship, and just needs to be guided the final few feet.
So simple. Some engineers don't like simple.
;)
Cheers
Phil Hobbs
On Tue, 29 Oct 2024 17:31:03 +0000, John R Walliker
<jrwalliker@gmail.com> wrote:
On 29/10/2024 17:26, john larkin wrote:
On Tue, 29 Oct 2024 17:02:02 -0000 (UTC), Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
john larkin <jl@glen--canyon.com> wrote:
On Mon, 28 Oct 2024 20:31:14 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
On 2024-10-28 17:10, john larkin wrote:
On Mon, 28 Oct 2024 15:49:30 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
On 2024-10-27 08:26, Klaus Vestergaard Kragelund wrote:
On 27-10-2024 03:26, john larkin wrote:
On Sun, 27 Oct 2024 02:19:14 +0200, Klaus Vestergaard Kragelund >>>>>>>>>> <klauskvik@hotmail.com> wrote:
Hi
I am working on an IR detector that will guide a robot into a docking
station.
A IR transmitter on the docking station transmits a beam, and 2 IR >>>>>>>>>>> detectors on the robot detects the beam and lets the robot navigate >>>>>>>>>>> towards the target. The working distance is a couple of meters. >>>>>>>>>>>
I need it to be insensitive to ambient light/sunlight.
The IR detectors are placed in a tube, to narrow in the beam angle and
to avoid sunlight (since it is seldom the sun is actually that low in
the horizon)
The IR transmitter will be modulated with 10kHz (TBD) frequency, low
duty cycle. Low duty cycle to be able to drive the LED with high >>>>>>>>>>> current, frequency modulated so that the receiver can ignore the effect
of daylight (DC)
If the LED on the docking station has higher radiant intensity at the
point of the robot (2 meters away) than possible IR from sunlight, then
that would be perfect.
Example of transmitter:
https://www.vishay.com/docs/83398/vsmy2850.pdf
Has up to 1000mW/sr. Seems my basic calculation for a 15 degree beam,
shows less than 10nW/m2, while sunlight has 1W/m2. So driving a beam
that has higher output than sunlight seems unlikely.
I would use a IR phototransistor at 850nm, something like this: >>>>>>>>>>>
https://www.ttelectronics.com/TTElectronics/media/ProductFiles/Datasheet/OP505-506-535-705.pdf
Or a photo diode:
https://docs.rs-online.com/9f58/0900766b816d8a09.pdf
Fed from reverse 3.3V and into a transimpedance amplifier to boost the
signal with bandpass filter.
One can get digital IR detector used in a remote control systems: >>>>>>>>>>>
https://www.vishay.com/docs/82491/tsop382.pdf
It has AGC, but digital output. I need analog output to be able to zero
in on the transmitter beam.
I have been looking for IR detectors that has the analog output, not
just the digital, but have not found any.
If the photodiode detector is subjected to sunlight, I am guessing I
would need very high gain on the 10kHz modulation frequency to pick up
the burried signal in the DC from sunlight.
How do I best bias the photo diode for optimum detection of the 10kHz
signal while being immune to the ambient sunlight?
I have chosen 850nm which seems to be a good wavelength. The spectrum at
sea level has some dips due to water absorption.
https://sciencetech-inc.com/web/image/49169/Spectrum%20with_out%20absorption.png
Seems like 750nm would be better, since then the IR from the sun is >>>>>>>>>>> lower, but does reduced the effective range of the system during >>>>>>>>>>> fog/rain. Probably that's why these system do not use 750nm >>>>>>>>>>>
Other considerations?
You could drive the LED with a square wave, 10 KHz or whatever. The >>>>>>>>>> photodiode could have +DC on one end and the other end can hit a >>>>>>>>>> parallel LC to ground, resonant at 10K.
That takes out the sunlight DC component and adds bandpass filtering.
That's a very nice idea. The Q should not matter much, just as long as
DC is removed.
The photodiode will still be subjected to the high ambient light, but >>>>>>>>> the gain would be close to zero for the stage after. I would then still
need to be sure the photodiode is never saturated by ambient light. >>>>>>>>>
Just don't fry the photodiode in high light.
So adding a resistance in series with the diode?
Nah, the Johnson noise kills you. It's easier to just calculate or >>>>>>>> measure the photocurrent from direct sunlight and design around that. >>>>>>>> You only need enough bias to ensure linear operation at high current, >>>>>>>> maybe a volt or so.
You will want to put a filter in the second stage to get rid of the >>>>>>>> nasty high-frequency noise peak. I usually use a two-pole Sallen-Key >>>>>>>> with equal resistor values, which has predictable gain (1.00) and low >>>>>>>> component-value sensitivity, and is super simple.
Resist the temptation to do anything floral with the TIA stage, such as
LC or *especially* gyrator filtering. A large inductor is a disaster in
a TIA, because if it doesn't cause instability, it'll still pick up crap
from every VF motor drive on the block, and deposit it right into the >>>>>>>> summing junction, where you really really don't want it.
Small shielded inductors are cheap, and 10 KHz is not a common
switching frequency.
VFDs put out large amounts of magnetic crap from the hundreds of hertz >>>>>> on up. I saw your VFD EMI filters at your Otis St shop. ;)
That was conducted EMI. 20 volt spikes everywhere on the top floor.
Mag fields drop rapidly with distance, 3rd power or something.
Put the two inductors close together. They will see mostly the same >>>>>>> mag fields, so a couple of resistors added somewhere will cancel the >>>>>>> pickup.
Or add a third, between them, to drive their bottom ends, again
canceling mag field pickup.
Or make each L from a pair, arranged so the pickups cancel.
Or just do three lines of algebra to pick the right resistor value, AC >>>>>> couple, and be done.
TV remotes work if you bounce the light off the ceiling in a well-lit >>>>>>> room.
"Well-lit", as in probably 1000 lumens of LED or fluorescent light, >>>>>> which has very little output in the >700 nm region.
But the acoustic approach would be better. Omni MEMS microphones have >>>>>>> built-in amps and cost 20 cents.
There are lots of imponderables there, though. For instance, on account >>>>>> of the slow speed of sound in air, a 1 m/s breeze (2.2 mph) will make >>>>>> the apparent direction of the acoustic source move by 3 mrad.
It's homing into the mother ship so a breeze will very slightly curve >>>>> the path.
You're an optics guy, so maybe don't like the sound thing.
Hidebound prejudice is the only possible explanation. ;)
Cheers
Phil Hobbs
(I don’t necessarily dislike the sound idea, but it’s more of a science
project than the LED approach. )
Think so? A quick experiment would be easy. Two MEMS mikes would feed
an oscilloscope directly. No inductors or TIAs or filters needed. One
could trigger the scope from the source and signal average for extra
fun.
The phase difference between two microphones would be a great
direction sensor. This would be so easy in production, a couple of
surface-mout MEMS mikes on a PC board.
You would need more than two microphones to get unambiguous results.
John
It would be better than two photodiodes in black tubes.
Three or four mikes would give 360 degree sensing.
As I understood the problem, the robot is probably pointing at the
mother ship, and just needs to be guided the final few feet.
So simple. Some engineers don't like simple.
Klaus Vestergaard Kragelund <klauskvik@hotmail.com> wrote:
Hi
I am working on an IR detector that will guide a robot into a docking
station.
It sounds as though the problem could be solved easily and reliably with
a VLF magnetic field, rather than light. Something along the lines of
the Lorenz blind landing beacon. By using dot-dash modulation, the
receiver would know which side of the centre line it was on.
The only problem would be convincing your client that it wasn't radio -
but that sounds like a much easier problem than all the solutions so far suggested.
On Tue, 29 Oct 2024 17:02:02 -0000 (UTC), Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:
john larkin <jl@glen--canyon.com> wrote:
On Mon, 28 Oct 2024 20:31:14 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
On 2024-10-28 17:10, john larkin wrote:
On Mon, 28 Oct 2024 15:49:30 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
On 2024-10-27 08:26, Klaus Vestergaard Kragelund wrote:
On 27-10-2024 03:26, john larkin wrote:
On Sun, 27 Oct 2024 02:19:14 +0200, Klaus Vestergaard Kragelund >>>>>>>> <klauskvik@hotmail.com> wrote:
Hi
I am working on an IR detector that will guide a robot into a docking >>>>>>>>> station.
A IR transmitter on the docking station transmits a beam, and 2 IR >>>>>>>>> detectors on the robot detects the beam and lets the robot navigate >>>>>>>>> towards the target. The working distance is a couple of meters. >>>>>>>>>
I need it to be insensitive to ambient light/sunlight.
The IR detectors are placed in a tube, to narrow in the beam angle and
to avoid sunlight (since it is seldom the sun is actually that low in >>>>>>>>> the horizon)
The IR transmitter will be modulated with 10kHz (TBD) frequency, low >>>>>>>>> duty cycle. Low duty cycle to be able to drive the LED with high >>>>>>>>> current, frequency modulated so that the receiver can ignore the effect
of daylight (DC)
If the LED on the docking station has higher radiant intensity at the >>>>>>>>> point of the robot (2 meters away) than possible IR from sunlight, then
that would be perfect.
Example of transmitter:
https://www.vishay.com/docs/83398/vsmy2850.pdf
Has up to 1000mW/sr. Seems my basic calculation for a 15 degree beam, >>>>>>>>> shows less than 10nW/m2, while sunlight has 1W/m2. So driving a beam >>>>>>>>> that has higher output than sunlight seems unlikely.
I would use a IR phototransistor at 850nm, something like this: >>>>>>>>>
https://www.ttelectronics.com/TTElectronics/media/ProductFiles/Datasheet/OP505-506-535-705.pdf
Or a photo diode:
https://docs.rs-online.com/9f58/0900766b816d8a09.pdf
Fed from reverse 3.3V and into a transimpedance amplifier to boost the
signal with bandpass filter.
One can get digital IR detector used in a remote control systems: >>>>>>>>>
https://www.vishay.com/docs/82491/tsop382.pdf
It has AGC, but digital output. I need analog output to be able to zero
in on the transmitter beam.
I have been looking for IR detectors that has the analog output, not >>>>>>>>> just the digital, but have not found any.
If the photodiode detector is subjected to sunlight, I am guessing I >>>>>>>>> would need very high gain on the 10kHz modulation frequency to pick up
the burried signal in the DC from sunlight.
How do I best bias the photo diode for optimum detection of the 10kHz >>>>>>>>> signal while being immune to the ambient sunlight?
I have chosen 850nm which seems to be a good wavelength. The spectrum at
sea level has some dips due to water absorption.
https://sciencetech-inc.com/web/image/49169/Spectrum%20with_out%20absorption.png
Seems like 750nm would be better, since then the IR from the sun is >>>>>>>>> lower, but does reduced the effective range of the system during >>>>>>>>> fog/rain. Probably that's why these system do not use 750nm
Other considerations?
You could drive the LED with a square wave, 10 KHz or whatever. The >>>>>>>> photodiode could have +DC on one end and the other end can hit a >>>>>>>> parallel LC to ground, resonant at 10K.
That takes out the sunlight DC component and adds bandpass filtering. >>>>>>>>
That's a very nice idea. The Q should not matter much, just as long as >>>>>>> DC is removed.
The photodiode will still be subjected to the high ambient light, but >>>>>>> the gain would be close to zero for the stage after. I would then still >>>>>>> need to be sure the photodiode is never saturated by ambient light. >>>>>>>
Just don't fry the photodiode in high light.
So adding a resistance in series with the diode?
Nah, the Johnson noise kills you. It's easier to just calculate or >>>>>> measure the photocurrent from direct sunlight and design around that. >>>>>> You only need enough bias to ensure linear operation at high current, >>>>>> maybe a volt or so.
You will want to put a filter in the second stage to get rid of the >>>>>> nasty high-frequency noise peak. I usually use a two-pole Sallen-Key >>>>>> with equal resistor values, which has predictable gain (1.00) and low >>>>>> component-value sensitivity, and is super simple.
Resist the temptation to do anything floral with the TIA stage, such as >>>>>> LC or *especially* gyrator filtering. A large inductor is a disaster in >>>>>> a TIA, because if it doesn't cause instability, it'll still pick up crap >>>>>> from every VF motor drive on the block, and deposit it right into the >>>>>> summing junction, where you really really don't want it.
Small shielded inductors are cheap, and 10 KHz is not a common
switching frequency.
VFDs put out large amounts of magnetic crap from the hundreds of hertz >>>> on up. I saw your VFD EMI filters at your Otis St shop. ;)
That was conducted EMI. 20 volt spikes everywhere on the top floor.
Mag fields drop rapidly with distance, 3rd power or something.
Put the two inductors close together. They will see mostly the same
mag fields, so a couple of resistors added somewhere will cancel the >>>>> pickup.
Or add a third, between them, to drive their bottom ends, again
canceling mag field pickup.
Or make each L from a pair, arranged so the pickups cancel.
Or just do three lines of algebra to pick the right resistor value, AC >>>> couple, and be done.
TV remotes work if you bounce the light off the ceiling in a well-lit >>>>> room.
"Well-lit", as in probably 1000 lumens of LED or fluorescent light,
which has very little output in the >700 nm region.
But the acoustic approach would be better. Omni MEMS microphones have >>>>> built-in amps and cost 20 cents.
There are lots of imponderables there, though. For instance, on account >>>> of the slow speed of sound in air, a 1 m/s breeze (2.2 mph) will make
the apparent direction of the acoustic source move by 3 mrad.
It's homing into the mother ship so a breeze will very slightly curve
the path.
You're an optics guy, so maybe don't like the sound thing.
Hidebound prejudice is the only possible explanation. ;)
Cheers
Phil Hobbs
(I don’t necessarily dislike the sound idea, but it’s more of a science >> project than the LED approach. )
Think so? A quick experiment would be easy. Two MEMS mikes would feed
an oscilloscope directly. No inductors or TIAs or filters needed. One
could trigger the scope from the source and signal average for extra
fun.
The phase difference between two microphones would be a great
direction sensor. This would be so easy in production, a couple of surface-mout MEMS mikes on a PC board.
On 29-10-2024 18:26, john larkin wrote:
On Tue, 29 Oct 2024 17:02:02 -0000 (UTC), Phil HobbsThe advantage of the photo diode solution, is that it's all analog, so
<pcdhSpamMeSenseless@electrooptical.net> wrote:
john larkin <jl@glen--canyon.com> wrote:
On Mon, 28 Oct 2024 20:31:14 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
On 2024-10-28 17:10, john larkin wrote:
On Mon, 28 Oct 2024 15:49:30 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
On 2024-10-27 08:26, Klaus Vestergaard Kragelund wrote:
On 27-10-2024 03:26, john larkin wrote:
On Sun, 27 Oct 2024 02:19:14 +0200, Klaus Vestergaard Kragelund >>>>>>>>> <klauskvik@hotmail.com> wrote:
Hi
I am working on an IR detector that will guide a robot into a docking
station.
A IR transmitter on the docking station transmits a beam, and 2 IR >>>>>>>>>> detectors on the robot detects the beam and lets the robot navigate >>>>>>>>>> towards the target. The working distance is a couple of meters. >>>>>>>>>>
I need it to be insensitive to ambient light/sunlight.
The IR detectors are placed in a tube, to narrow in the beam angle and
to avoid sunlight (since it is seldom the sun is actually that low in
the horizon)
The IR transmitter will be modulated with 10kHz (TBD) frequency, low >>>>>>>>>> duty cycle. Low duty cycle to be able to drive the LED with high >>>>>>>>>> current, frequency modulated so that the receiver can ignore the effect
of daylight (DC)
If the LED on the docking station has higher radiant intensity at the
point of the robot (2 meters away) than possible IR from sunlight, then
that would be perfect.
Example of transmitter:
https://www.vishay.com/docs/83398/vsmy2850.pdf
Has up to 1000mW/sr. Seems my basic calculation for a 15 degree beam,
shows less than 10nW/m2, while sunlight has 1W/m2. So driving a beam >>>>>>>>>> that has higher output than sunlight seems unlikely.
I would use a IR phototransistor at 850nm, something like this: >>>>>>>>>>
https://www.ttelectronics.com/TTElectronics/media/ProductFiles/Datasheet/OP505-506-535-705.pdf
Or a photo diode:
https://docs.rs-online.com/9f58/0900766b816d8a09.pdf
Fed from reverse 3.3V and into a transimpedance amplifier to boost the
signal with bandpass filter.
One can get digital IR detector used in a remote control systems: >>>>>>>>>>
https://www.vishay.com/docs/82491/tsop382.pdf
It has AGC, but digital output. I need analog output to be able to zero
in on the transmitter beam.
I have been looking for IR detectors that has the analog output, not >>>>>>>>>> just the digital, but have not found any.
If the photodiode detector is subjected to sunlight, I am guessing I >>>>>>>>>> would need very high gain on the 10kHz modulation frequency to pick up
the burried signal in the DC from sunlight.
How do I best bias the photo diode for optimum detection of the 10kHz
signal while being immune to the ambient sunlight?
I have chosen 850nm which seems to be a good wavelength. The spectrum at
sea level has some dips due to water absorption.
https://sciencetech-inc.com/web/image/49169/Spectrum%20with_out%20absorption.png
Seems like 750nm would be better, since then the IR from the sun is >>>>>>>>>> lower, but does reduced the effective range of the system during >>>>>>>>>> fog/rain. Probably that's why these system do not use 750nm >>>>>>>>>>
Other considerations?
You could drive the LED with a square wave, 10 KHz or whatever. The >>>>>>>>> photodiode could have +DC on one end and the other end can hit a >>>>>>>>> parallel LC to ground, resonant at 10K.
That takes out the sunlight DC component and adds bandpass filtering. >>>>>>>>>
That's a very nice idea. The Q should not matter much, just as long as >>>>>>>> DC is removed.
The photodiode will still be subjected to the high ambient light, but >>>>>>>> the gain would be close to zero for the stage after. I would then still
need to be sure the photodiode is never saturated by ambient light. >>>>>>>>
Just don't fry the photodiode in high light.
So adding a resistance in series with the diode?
Nah, the Johnson noise kills you. It's easier to just calculate or >>>>>>> measure the photocurrent from direct sunlight and design around that. >>>>>>> You only need enough bias to ensure linear operation at high current, >>>>>>> maybe a volt or so.
You will want to put a filter in the second stage to get rid of the >>>>>>> nasty high-frequency noise peak. I usually use a two-pole Sallen-Key >>>>>>> with equal resistor values, which has predictable gain (1.00) and low >>>>>>> component-value sensitivity, and is super simple.
Resist the temptation to do anything floral with the TIA stage, such as >>>>>>> LC or *especially* gyrator filtering. A large inductor is a disaster in
a TIA, because if it doesn't cause instability, it'll still pick up crap
from every VF motor drive on the block, and deposit it right into the >>>>>>> summing junction, where you really really don't want it.
Small shielded inductors are cheap, and 10 KHz is not a common
switching frequency.
VFDs put out large amounts of magnetic crap from the hundreds of hertz >>>>> on up. I saw your VFD EMI filters at your Otis St shop. ;)
That was conducted EMI. 20 volt spikes everywhere on the top floor.
Mag fields drop rapidly with distance, 3rd power or something.
Put the two inductors close together. They will see mostly the same >>>>>> mag fields, so a couple of resistors added somewhere will cancel the >>>>>> pickup.
Or add a third, between them, to drive their bottom ends, again
canceling mag field pickup.
Or make each L from a pair, arranged so the pickups cancel.
Or just do three lines of algebra to pick the right resistor value, AC >>>>> couple, and be done.
TV remotes work if you bounce the light off the ceiling in a well-lit >>>>>> room.
"Well-lit", as in probably 1000 lumens of LED or fluorescent light,
which has very little output in the >700 nm region.
But the acoustic approach would be better. Omni MEMS microphones have >>>>>> built-in amps and cost 20 cents.
There are lots of imponderables there, though. For instance, on account >>>>> of the slow speed of sound in air, a 1 m/s breeze (2.2 mph) will make >>>>> the apparent direction of the acoustic source move by 3 mrad.
It's homing into the mother ship so a breeze will very slightly curve
the path.
You're an optics guy, so maybe don't like the sound thing.
Hidebound prejudice is the only possible explanation. ;)
Cheers
Phil Hobbs
(I don’t necessarily dislike the sound idea, but it’s more of a science
project than the LED approach. )
Think so? A quick experiment would be easy. Two MEMS mikes would feed
an oscilloscope directly. No inductors or TIAs or filters needed. One
could trigger the scope from the source and signal average for extra
fun.
The phase difference between two microphones would be a great
direction sensor. This would be so easy in production, a couple of
surface-mout MEMS mikes on a PC board.
can be build and tested quickly, without ordering a PCB
On 29-10-2024 19:27, john larkin wrote:
On Tue, 29 Oct 2024 17:31:03 +0000, John R Walliker
<jrwalliker@gmail.com> wrote:
On 29/10/2024 17:26, john larkin wrote:
On Tue, 29 Oct 2024 17:02:02 -0000 (UTC), Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
john larkin <jl@glen--canyon.com> wrote:
On Mon, 28 Oct 2024 20:31:14 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
On 2024-10-28 17:10, john larkin wrote:
On Mon, 28 Oct 2024 15:49:30 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
On 2024-10-27 08:26, Klaus Vestergaard Kragelund wrote:
On 27-10-2024 03:26, john larkin wrote:
On Sun, 27 Oct 2024 02:19:14 +0200, Klaus Vestergaard Kragelund >>>>>>>>>>> <klauskvik@hotmail.com> wrote:
Hi
I am working on an IR detector that will guide a robot into a docking
station.
A IR transmitter on the docking station transmits a beam, and 2 IR >>>>>>>>>>>> detectors on the robot detects the beam and lets the robot navigate
towards the target. The working distance is a couple of meters. >>>>>>>>>>>>
I need it to be insensitive to ambient light/sunlight. >>>>>>>>>>>>
The IR detectors are placed in a tube, to narrow in the beam angle and
to avoid sunlight (since it is seldom the sun is actually that low in
the horizon)
The IR transmitter will be modulated with 10kHz (TBD) frequency, low
duty cycle. Low duty cycle to be able to drive the LED with high >>>>>>>>>>>> current, frequency modulated so that the receiver can ignore the effect
of daylight (DC)
If the LED on the docking station has higher radiant intensity at the
point of the robot (2 meters away) than possible IR from sunlight, then
that would be perfect.
Example of transmitter:
https://www.vishay.com/docs/83398/vsmy2850.pdf
Has up to 1000mW/sr. Seems my basic calculation for a 15 degree beam,
shows less than 10nW/m2, while sunlight has 1W/m2. So driving a beam
that has higher output than sunlight seems unlikely.
I would use a IR phototransistor at 850nm, something like this: >>>>>>>>>>>>
https://www.ttelectronics.com/TTElectronics/media/ProductFiles/Datasheet/OP505-506-535-705.pdf
Or a photo diode:
https://docs.rs-online.com/9f58/0900766b816d8a09.pdf
Fed from reverse 3.3V and into a transimpedance amplifier to boost the
signal with bandpass filter.
One can get digital IR detector used in a remote control systems: >>>>>>>>>>>>
https://www.vishay.com/docs/82491/tsop382.pdf
It has AGC, but digital output. I need analog output to be able to zero
in on the transmitter beam.
I have been looking for IR detectors that has the analog output, not
just the digital, but have not found any.
If the photodiode detector is subjected to sunlight, I am guessing I
would need very high gain on the 10kHz modulation frequency to pick up
the burried signal in the DC from sunlight.
How do I best bias the photo diode for optimum detection of the 10kHz
signal while being immune to the ambient sunlight?
I have chosen 850nm which seems to be a good wavelength. The spectrum at
sea level has some dips due to water absorption.
https://sciencetech-inc.com/web/image/49169/Spectrum%20with_out%20absorption.png
Seems like 750nm would be better, since then the IR from the sun is
lower, but does reduced the effective range of the system during >>>>>>>>>>>> fog/rain. Probably that's why these system do not use 750nm >>>>>>>>>>>>
Other considerations?
You could drive the LED with a square wave, 10 KHz or whatever. The >>>>>>>>>>> photodiode could have +DC on one end and the other end can hit a >>>>>>>>>>> parallel LC to ground, resonant at 10K.
That takes out the sunlight DC component and adds bandpass filtering.
That's a very nice idea. The Q should not matter much, just as long as
DC is removed.
The photodiode will still be subjected to the high ambient light, but
the gain would be close to zero for the stage after. I would then still
need to be sure the photodiode is never saturated by ambient light. >>>>>>>>>>
Just don't fry the photodiode in high light.
So adding a resistance in series with the diode?
Nah, the Johnson noise kills you. It's easier to just calculate or >>>>>>>>> measure the photocurrent from direct sunlight and design around that. >>>>>>>>> You only need enough bias to ensure linear operation at high current, >>>>>>>>> maybe a volt or so.
You will want to put a filter in the second stage to get rid of the >>>>>>>>> nasty high-frequency noise peak. I usually use a two-pole Sallen-Key >>>>>>>>> with equal resistor values, which has predictable gain (1.00) and low >>>>>>>>> component-value sensitivity, and is super simple.
Resist the temptation to do anything floral with the TIA stage, such as
LC or *especially* gyrator filtering. A large inductor is a disaster in
a TIA, because if it doesn't cause instability, it'll still pick up crap
from every VF motor drive on the block, and deposit it right into the >>>>>>>>> summing junction, where you really really don't want it.
Small shielded inductors are cheap, and 10 KHz is not a common >>>>>>>> switching frequency.
VFDs put out large amounts of magnetic crap from the hundreds of hertz >>>>>>> on up. I saw your VFD EMI filters at your Otis St shop. ;)
That was conducted EMI. 20 volt spikes everywhere on the top floor. >>>>>> Mag fields drop rapidly with distance, 3rd power or something.
Put the two inductors close together. They will see mostly the same >>>>>>>> mag fields, so a couple of resistors added somewhere will cancel the >>>>>>>> pickup.
Or add a third, between them, to drive their bottom ends, again >>>>>>>> canceling mag field pickup.
Or make each L from a pair, arranged so the pickups cancel.
Or just do three lines of algebra to pick the right resistor value, AC >>>>>>> couple, and be done.
TV remotes work if you bounce the light off the ceiling in a well-lit >>>>>>>> room.
"Well-lit", as in probably 1000 lumens of LED or fluorescent light, >>>>>>> which has very little output in the >700 nm region.
But the acoustic approach would be better. Omni MEMS microphones have >>>>>>>> built-in amps and cost 20 cents.
There are lots of imponderables there, though. For instance, on account
of the slow speed of sound in air, a 1 m/s breeze (2.2 mph) will make >>>>>>> the apparent direction of the acoustic source move by 3 mrad.
It's homing into the mother ship so a breeze will very slightly curve >>>>>> the path.
You're an optics guy, so maybe don't like the sound thing.
Hidebound prejudice is the only possible explanation. ;)
Cheers
Phil Hobbs
(I don’t necessarily dislike the sound idea, but it’s more of a science >>>>> project than the LED approach. )
Think so? A quick experiment would be easy. Two MEMS mikes would feed
an oscilloscope directly. No inductors or TIAs or filters needed. One
could trigger the scope from the source and signal average for extra
fun.
The phase difference between two microphones would be a great
direction sensor. This would be so easy in production, a couple of
surface-mout MEMS mikes on a PC board.
You would need more than two microphones to get unambiguous results.
John
It would be better than two photodiodes in black tubes.
Three or four mikes would give 360 degree sensing.
As I understood the problem, the robot is probably pointing at the
mother ship, and just needs to be guided the final few feet.
So simple. Some engineers don't like simple.
This one cost just less than 2USD, goes to 80kHz:
https://www.st.com/resource/en/datasheet/imp23absu.pdf
But, the S/N is only 64dB. I don't see how you can do averaging, no
access to the source. It would need to acquire continuously, doing FFT
to detect the chirp. Would need to add filter to remove noise from >surroundings, and it's own motors.
Adding them on a PCB would could be tricky, since reflections still is a >major hassle.
john larkin <jl@glen--canyon.com> wrote:
On Tue, 29 Oct 2024 17:31:03 +0000, John R Walliker
<jrwalliker@gmail.com> wrote:
On 29/10/2024 17:26, john larkin wrote:
On Tue, 29 Oct 2024 17:02:02 -0000 (UTC), Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
john larkin <jl@glen--canyon.com> wrote:
On Mon, 28 Oct 2024 20:31:14 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
On 2024-10-28 17:10, john larkin wrote:
On Mon, 28 Oct 2024 15:49:30 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
On 2024-10-27 08:26, Klaus Vestergaard Kragelund wrote:
On 27-10-2024 03:26, john larkin wrote:
On Sun, 27 Oct 2024 02:19:14 +0200, Klaus Vestergaard Kragelund >>>>>>>>>>> <klauskvik@hotmail.com> wrote:
Hi
I am working on an IR detector that will guide a robot into a docking
station.
A IR transmitter on the docking station transmits a beam, and 2 IR >>>>>>>>>>>> detectors on the robot detects the beam and lets the robot navigate
towards the target. The working distance is a couple of meters. >>>>>>>>>>>>
I need it to be insensitive to ambient light/sunlight. >>>>>>>>>>>>
The IR detectors are placed in a tube, to narrow in the beam angle and
to avoid sunlight (since it is seldom the sun is actually that low in
the horizon)
The IR transmitter will be modulated with 10kHz (TBD) frequency, low
duty cycle. Low duty cycle to be able to drive the LED with high >>>>>>>>>>>> current, frequency modulated so that the receiver can ignore the effect
of daylight (DC)
If the LED on the docking station has higher radiant intensity at the
point of the robot (2 meters away) than possible IR from sunlight, then
that would be perfect.
Example of transmitter:
https://www.vishay.com/docs/83398/vsmy2850.pdf
Has up to 1000mW/sr. Seems my basic calculation for a 15 degree beam,
shows less than 10nW/m2, while sunlight has 1W/m2. So driving a beam
that has higher output than sunlight seems unlikely.
I would use a IR phototransistor at 850nm, something like this: >>>>>>>>>>>>
https://www.ttelectronics.com/TTElectronics/media/ProductFiles/Datasheet/OP505-506-535-705.pdf
Or a photo diode:
https://docs.rs-online.com/9f58/0900766b816d8a09.pdf
Fed from reverse 3.3V and into a transimpedance amplifier to boost the
signal with bandpass filter.
One can get digital IR detector used in a remote control systems: >>>>>>>>>>>>
https://www.vishay.com/docs/82491/tsop382.pdf
It has AGC, but digital output. I need analog output to be able to zero
in on the transmitter beam.
I have been looking for IR detectors that has the analog output, not
just the digital, but have not found any.
If the photodiode detector is subjected to sunlight, I am guessing I
would need very high gain on the 10kHz modulation frequency to pick up
the burried signal in the DC from sunlight.
How do I best bias the photo diode for optimum detection of the 10kHz
signal while being immune to the ambient sunlight?
I have chosen 850nm which seems to be a good wavelength. The spectrum at
sea level has some dips due to water absorption.
https://sciencetech-inc.com/web/image/49169/Spectrum%20with_out%20absorption.png
Seems like 750nm would be better, since then the IR from the sun is
lower, but does reduced the effective range of the system during >>>>>>>>>>>> fog/rain. Probably that's why these system do not use 750nm >>>>>>>>>>>>
Other considerations?
You could drive the LED with a square wave, 10 KHz or whatever. The >>>>>>>>>>> photodiode could have +DC on one end and the other end can hit a >>>>>>>>>>> parallel LC to ground, resonant at 10K.
That takes out the sunlight DC component and adds bandpass filtering.
That's a very nice idea. The Q should not matter much, just as long as
DC is removed.
The photodiode will still be subjected to the high ambient light, but
the gain would be close to zero for the stage after. I would then still
need to be sure the photodiode is never saturated by ambient light. >>>>>>>>>>
Just don't fry the photodiode in high light.
So adding a resistance in series with the diode?
Nah, the Johnson noise kills you. It's easier to just calculate or >>>>>>>>> measure the photocurrent from direct sunlight and design around that. >>>>>>>>> You only need enough bias to ensure linear operation at high current, >>>>>>>>> maybe a volt or so.
You will want to put a filter in the second stage to get rid of the >>>>>>>>> nasty high-frequency noise peak. I usually use a two-pole Sallen-Key >>>>>>>>> with equal resistor values, which has predictable gain (1.00) and low >>>>>>>>> component-value sensitivity, and is super simple.
Resist the temptation to do anything floral with the TIA stage, such as
LC or *especially* gyrator filtering. A large inductor is a disaster in
a TIA, because if it doesn't cause instability, it'll still pick up crap
from every VF motor drive on the block, and deposit it right into the >>>>>>>>> summing junction, where you really really don't want it.
Small shielded inductors are cheap, and 10 KHz is not a common >>>>>>>> switching frequency.
VFDs put out large amounts of magnetic crap from the hundreds of hertz >>>>>>> on up. I saw your VFD EMI filters at your Otis St shop. ;)
That was conducted EMI. 20 volt spikes everywhere on the top floor. >>>>>> Mag fields drop rapidly with distance, 3rd power or something.
Put the two inductors close together. They will see mostly the same >>>>>>>> mag fields, so a couple of resistors added somewhere will cancel the >>>>>>>> pickup.
Or add a third, between them, to drive their bottom ends, again >>>>>>>> canceling mag field pickup.
Or make each L from a pair, arranged so the pickups cancel.
Or just do three lines of algebra to pick the right resistor value, AC >>>>>>> couple, and be done.
TV remotes work if you bounce the light off the ceiling in a well-lit >>>>>>>> room.
"Well-lit", as in probably 1000 lumens of LED or fluorescent light, >>>>>>> which has very little output in the >700 nm region.
But the acoustic approach would be better. Omni MEMS microphones have >>>>>>>> built-in amps and cost 20 cents.
There are lots of imponderables there, though. For instance, on account
of the slow speed of sound in air, a 1 m/s breeze (2.2 mph) will make >>>>>>> the apparent direction of the acoustic source move by 3 mrad.
It's homing into the mother ship so a breeze will very slightly curve >>>>>> the path.
You're an optics guy, so maybe don't like the sound thing.
Hidebound prejudice is the only possible explanation. ;)
Cheers
Phil Hobbs
(I donÂ’t necessarily dislike the sound idea, but itÂ’s more of a science >>>>> project than the LED approach. )
Think so? A quick experiment would be easy. Two MEMS mikes would feed
an oscilloscope directly. No inductors or TIAs or filters needed. One
could trigger the scope from the source and signal average for extra
fun.
The phase difference between two microphones would be a great
direction sensor. This would be so easy in production, a couple of
surface-mout MEMS mikes on a PC board.
You would need more than two microphones to get unambiguous results.
John
It would be better than two photodiodes in black tubes.
Maybe so. Depends on the numbers.
Some of them actually have to build the gizmo that we’re all busily opining >about.
Three or four mikes would give 360 degree sensing.
As I understood the problem, the robot is probably pointing at the
mother ship, and just needs to be guided the final few feet.
So simple. Some engineers don't like simple.
;)
On Wed, 30 Oct 2024 00:02:34 +0100, Klaus Vestergaard Kragelund <klauskvik@hotmail.com> wrote:
On 29-10-2024 18:26, john larkin wrote:
On Tue, 29 Oct 2024 17:02:02 -0000 (UTC), Phil HobbsThe advantage of the photo diode solution, is that it's all analog, so
<pcdhSpamMeSenseless@electrooptical.net> wrote:
john larkin <jl@glen--canyon.com> wrote:
On Mon, 28 Oct 2024 20:31:14 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
On 2024-10-28 17:10, john larkin wrote:
On Mon, 28 Oct 2024 15:49:30 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
On 2024-10-27 08:26, Klaus Vestergaard Kragelund wrote:
On 27-10-2024 03:26, john larkin wrote:
On Sun, 27 Oct 2024 02:19:14 +0200, Klaus Vestergaard Kragelund >>>>>>>>>> <klauskvik@hotmail.com> wrote:
Hi
I am working on an IR detector that will guide a robot into a docking
station.
A IR transmitter on the docking station transmits a beam, and 2 IR >>>>>>>>>>> detectors on the robot detects the beam and lets the robot navigate >>>>>>>>>>> towards the target. The working distance is a couple of meters. >>>>>>>>>>>
I need it to be insensitive to ambient light/sunlight.
The IR detectors are placed in a tube, to narrow in the beam angle and
to avoid sunlight (since it is seldom the sun is actually that low in
the horizon)
The IR transmitter will be modulated with 10kHz (TBD) frequency, low
duty cycle. Low duty cycle to be able to drive the LED with high >>>>>>>>>>> current, frequency modulated so that the receiver can ignore the effect
of daylight (DC)
If the LED on the docking station has higher radiant intensity at the
point of the robot (2 meters away) than possible IR from sunlight, then
that would be perfect.
Example of transmitter:
https://www.vishay.com/docs/83398/vsmy2850.pdf
Has up to 1000mW/sr. Seems my basic calculation for a 15 degree beam,
shows less than 10nW/m2, while sunlight has 1W/m2. So driving a beam
that has higher output than sunlight seems unlikely.
I would use a IR phototransistor at 850nm, something like this: >>>>>>>>>>>
https://www.ttelectronics.com/TTElectronics/media/ProductFiles/Datasheet/OP505-506-535-705.pdf
Or a photo diode:
https://docs.rs-online.com/9f58/0900766b816d8a09.pdf
Fed from reverse 3.3V and into a transimpedance amplifier to boost the
signal with bandpass filter.
One can get digital IR detector used in a remote control systems: >>>>>>>>>>>
https://www.vishay.com/docs/82491/tsop382.pdf
It has AGC, but digital output. I need analog output to be able to zero
in on the transmitter beam.
I have been looking for IR detectors that has the analog output, not
just the digital, but have not found any.
If the photodiode detector is subjected to sunlight, I am guessing I
would need very high gain on the 10kHz modulation frequency to pick up
the burried signal in the DC from sunlight.
How do I best bias the photo diode for optimum detection of the 10kHz
signal while being immune to the ambient sunlight?
I have chosen 850nm which seems to be a good wavelength. The spectrum at
sea level has some dips due to water absorption.
https://sciencetech-inc.com/web/image/49169/Spectrum%20with_out%20absorption.png
Seems like 750nm would be better, since then the IR from the sun is >>>>>>>>>>> lower, but does reduced the effective range of the system during >>>>>>>>>>> fog/rain. Probably that's why these system do not use 750nm >>>>>>>>>>>
Other considerations?
You could drive the LED with a square wave, 10 KHz or whatever. The >>>>>>>>>> photodiode could have +DC on one end and the other end can hit a >>>>>>>>>> parallel LC to ground, resonant at 10K.
That takes out the sunlight DC component and adds bandpass filtering.
That's a very nice idea. The Q should not matter much, just as long as
DC is removed.
The photodiode will still be subjected to the high ambient light, but >>>>>>>>> the gain would be close to zero for the stage after. I would then still
need to be sure the photodiode is never saturated by ambient light. >>>>>>>>>
Just don't fry the photodiode in high light.
So adding a resistance in series with the diode?
Nah, the Johnson noise kills you. It's easier to just calculate or >>>>>>>> measure the photocurrent from direct sunlight and design around that. >>>>>>>> You only need enough bias to ensure linear operation at high current, >>>>>>>> maybe a volt or so.
You will want to put a filter in the second stage to get rid of the >>>>>>>> nasty high-frequency noise peak. I usually use a two-pole Sallen-Key >>>>>>>> with equal resistor values, which has predictable gain (1.00) and low >>>>>>>> component-value sensitivity, and is super simple.
Resist the temptation to do anything floral with the TIA stage, such as
LC or *especially* gyrator filtering. A large inductor is a disaster in
a TIA, because if it doesn't cause instability, it'll still pick up crap
from every VF motor drive on the block, and deposit it right into the >>>>>>>> summing junction, where you really really don't want it.
Small shielded inductors are cheap, and 10 KHz is not a common
switching frequency.
VFDs put out large amounts of magnetic crap from the hundreds of hertz >>>>>> on up. I saw your VFD EMI filters at your Otis St shop. ;)
That was conducted EMI. 20 volt spikes everywhere on the top floor.
Mag fields drop rapidly with distance, 3rd power or something.
Put the two inductors close together. They will see mostly the same >>>>>>> mag fields, so a couple of resistors added somewhere will cancel the >>>>>>> pickup.
Or add a third, between them, to drive their bottom ends, again
canceling mag field pickup.
Or make each L from a pair, arranged so the pickups cancel.
Or just do three lines of algebra to pick the right resistor value, AC >>>>>> couple, and be done.
TV remotes work if you bounce the light off the ceiling in a well-lit >>>>>>> room.
"Well-lit", as in probably 1000 lumens of LED or fluorescent light, >>>>>> which has very little output in the >700 nm region.
But the acoustic approach would be better. Omni MEMS microphones have >>>>>>> built-in amps and cost 20 cents.
There are lots of imponderables there, though. For instance, on account >>>>>> of the slow speed of sound in air, a 1 m/s breeze (2.2 mph) will make >>>>>> the apparent direction of the acoustic source move by 3 mrad.
It's homing into the mother ship so a breeze will very slightly curve >>>>> the path.
You're an optics guy, so maybe don't like the sound thing.
Hidebound prejudice is the only possible explanation. ;)
Cheers
Phil Hobbs
(I don’t necessarily dislike the sound idea, but it’s more of a science
project than the LED approach. )
Think so? A quick experiment would be easy. Two MEMS mikes would feed
an oscilloscope directly. No inductors or TIAs or filters needed. One
could trigger the scope from the source and signal average for extra
fun.
The phase difference between two microphones would be a great
direction sensor. This would be so easy in production, a couple of
surface-mout MEMS mikes on a PC board.
can be build and tested quickly, without ordering a PCB
You can solder some wires onto a MEMS microphone.
Optical: imagine that the docking station has a small vertical wall
inside a cavity or equivalent. There's an LED set back on each side,
so the robot sees one LED or the other as it moves side to side. The
robot has a single photodiode staring ahead.
Drive the two LEDs at different frequencies. Too far left, you will
hear BEEP. Too far right, hear BOOP. Sort of like the old airplane
landing thing.
Looks promising with two LEDs and a business card.
On 29-10-2024 20:59, Liz Tuddenham wrote:
Klaus Vestergaard Kragelund <klauskvik@hotmail.com> wrote:
Hi
I am working on an IR detector that will guide a robot into a docking
station.
It sounds as though the problem could be solved easily and reliably with
a VLF magnetic field, rather than light. Something along the lines of
the Lorenz blind landing beacon. By using dot-dash modulation, the receiver would know which side of the centre line it was on.
The only problem would be convincing your client that it wasn't radio -
but that sounds like a much easier problem than all the solutions so far suggested.
I did look into that, but did not go deeper.
The Lorenz beacon was very ingenious.
The solution with a rectangular loop in the base of the docking station worked well, but the client doesn't want that.
Maybe it's time to convince him to look at other solutions again :-)
On 30-10-2024 00:31, john larkin wrote:
On Wed, 30 Oct 2024 00:02:34 +0100, Klaus Vestergaard KragelundYes, that's how the Luba does it:
<klauskvik@hotmail.com> wrote:
On 29-10-2024 18:26, john larkin wrote:
On Tue, 29 Oct 2024 17:02:02 -0000 (UTC), Phil HobbsThe advantage of the photo diode solution, is that it's all analog, so
<pcdhSpamMeSenseless@electrooptical.net> wrote:
john larkin <jl@glen--canyon.com> wrote:
On Mon, 28 Oct 2024 20:31:14 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
On 2024-10-28 17:10, john larkin wrote:
On Mon, 28 Oct 2024 15:49:30 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
On 2024-10-27 08:26, Klaus Vestergaard Kragelund wrote:
On 27-10-2024 03:26, john larkin wrote:
On Sun, 27 Oct 2024 02:19:14 +0200, Klaus Vestergaard Kragelund >>>>>>>>>>> <klauskvik@hotmail.com> wrote:
Hi
I am working on an IR detector that will guide a robot into a docking
station.
A IR transmitter on the docking station transmits a beam, and 2 IR >>>>>>>>>>>> detectors on the robot detects the beam and lets the robot navigate
towards the target. The working distance is a couple of meters. >>>>>>>>>>>>
I need it to be insensitive to ambient light/sunlight. >>>>>>>>>>>>
The IR detectors are placed in a tube, to narrow in the beam angle and
to avoid sunlight (since it is seldom the sun is actually that low in
the horizon)
The IR transmitter will be modulated with 10kHz (TBD) frequency, low
duty cycle. Low duty cycle to be able to drive the LED with high >>>>>>>>>>>> current, frequency modulated so that the receiver can ignore the effect
of daylight (DC)
If the LED on the docking station has higher radiant intensity at the
point of the robot (2 meters away) than possible IR from sunlight, then
that would be perfect.
Example of transmitter:
https://www.vishay.com/docs/83398/vsmy2850.pdf
Has up to 1000mW/sr. Seems my basic calculation for a 15 degree beam,
shows less than 10nW/m2, while sunlight has 1W/m2. So driving a beam
that has higher output than sunlight seems unlikely.
I would use a IR phototransistor at 850nm, something like this: >>>>>>>>>>>>
https://www.ttelectronics.com/TTElectronics/media/ProductFiles/Datasheet/OP505-506-535-705.pdf
Or a photo diode:
https://docs.rs-online.com/9f58/0900766b816d8a09.pdf
Fed from reverse 3.3V and into a transimpedance amplifier to boost the
signal with bandpass filter.
One can get digital IR detector used in a remote control systems: >>>>>>>>>>>>
https://www.vishay.com/docs/82491/tsop382.pdf
It has AGC, but digital output. I need analog output to be able to zero
in on the transmitter beam.
I have been looking for IR detectors that has the analog output, not
just the digital, but have not found any.
If the photodiode detector is subjected to sunlight, I am guessing I
would need very high gain on the 10kHz modulation frequency to pick up
the burried signal in the DC from sunlight.
How do I best bias the photo diode for optimum detection of the 10kHz
signal while being immune to the ambient sunlight?
I have chosen 850nm which seems to be a good wavelength. The spectrum at
sea level has some dips due to water absorption.
https://sciencetech-inc.com/web/image/49169/Spectrum%20with_out%20absorption.png
Seems like 750nm would be better, since then the IR from the sun is
lower, but does reduced the effective range of the system during >>>>>>>>>>>> fog/rain. Probably that's why these system do not use 750nm >>>>>>>>>>>>
Other considerations?
You could drive the LED with a square wave, 10 KHz or whatever. The >>>>>>>>>>> photodiode could have +DC on one end and the other end can hit a >>>>>>>>>>> parallel LC to ground, resonant at 10K.
That takes out the sunlight DC component and adds bandpass filtering.
That's a very nice idea. The Q should not matter much, just as long as
DC is removed.
The photodiode will still be subjected to the high ambient light, but
the gain would be close to zero for the stage after. I would then still
need to be sure the photodiode is never saturated by ambient light. >>>>>>>>>>
Just don't fry the photodiode in high light.
So adding a resistance in series with the diode?
Nah, the Johnson noise kills you. It's easier to just calculate or >>>>>>>>> measure the photocurrent from direct sunlight and design around that. >>>>>>>>> You only need enough bias to ensure linear operation at high current, >>>>>>>>> maybe a volt or so.
You will want to put a filter in the second stage to get rid of the >>>>>>>>> nasty high-frequency noise peak. I usually use a two-pole Sallen-Key >>>>>>>>> with equal resistor values, which has predictable gain (1.00) and low >>>>>>>>> component-value sensitivity, and is super simple.
Resist the temptation to do anything floral with the TIA stage, such as
LC or *especially* gyrator filtering. A large inductor is a disaster in
a TIA, because if it doesn't cause instability, it'll still pick up crap
from every VF motor drive on the block, and deposit it right into the >>>>>>>>> summing junction, where you really really don't want it.
Small shielded inductors are cheap, and 10 KHz is not a common >>>>>>>> switching frequency.
VFDs put out large amounts of magnetic crap from the hundreds of hertz >>>>>>> on up. I saw your VFD EMI filters at your Otis St shop. ;)
That was conducted EMI. 20 volt spikes everywhere on the top floor. >>>>>> Mag fields drop rapidly with distance, 3rd power or something.
Put the two inductors close together. They will see mostly the same >>>>>>>> mag fields, so a couple of resistors added somewhere will cancel the >>>>>>>> pickup.
Or add a third, between them, to drive their bottom ends, again >>>>>>>> canceling mag field pickup.
Or make each L from a pair, arranged so the pickups cancel.
Or just do three lines of algebra to pick the right resistor value, AC >>>>>>> couple, and be done.
TV remotes work if you bounce the light off the ceiling in a well-lit >>>>>>>> room.
"Well-lit", as in probably 1000 lumens of LED or fluorescent light, >>>>>>> which has very little output in the >700 nm region.
But the acoustic approach would be better. Omni MEMS microphones have >>>>>>>> built-in amps and cost 20 cents.
There are lots of imponderables there, though. For instance, on account
of the slow speed of sound in air, a 1 m/s breeze (2.2 mph) will make >>>>>>> the apparent direction of the acoustic source move by 3 mrad.
It's homing into the mother ship so a breeze will very slightly curve >>>>>> the path.
You're an optics guy, so maybe don't like the sound thing.
Hidebound prejudice is the only possible explanation. ;)
Cheers
Phil Hobbs
(I don’t necessarily dislike the sound idea, but it’s more of a science >>>>> project than the LED approach. )
Think so? A quick experiment would be easy. Two MEMS mikes would feed
an oscilloscope directly. No inductors or TIAs or filters needed. One
could trigger the scope from the source and signal average for extra
fun.
The phase difference between two microphones would be a great
direction sensor. This would be so easy in production, a couple of
surface-mout MEMS mikes on a PC board.
can be build and tested quickly, without ordering a PCB
You can solder some wires onto a MEMS microphone.
Optical: imagine that the docking station has a small vertical wall
inside a cavity or equivalent. There's an LED set back on each side,
so the robot sees one LED or the other as it moves side to side. The
robot has a single photodiode staring ahead.
Drive the two LEDs at different frequencies. Too far left, you will
hear BEEP. Too far right, hear BOOP. Sort of like the old airplane
landing thing.
Looks promising with two LEDs and a business card.
https://youtu.be/tKSR9LqHPDI?si=0V9nWtexG4yKP_wO&t=110
I have shifted to that too, then only a single receiver is needed.
On the topic of optics, some LIDAR system uses 940nm, since water
absorption removes most of the sunlight interference:
https://www.e-motec.net/wp-content/uploads/2022/02/10.png
But, for this IR system, the power output is close to a million times
lower than a LIDAR, and water absorbtion could reduce the beam strength
from emitter to receiver if there's fog or rain.
Would 940nm be a good choice for a IR system?
On Wed, 30 Oct 2024 09:45:42 +0100, Klaus Vestergaard Kragelund <klauskvik@hotmail.com> wrote:
On 30-10-2024 00:31, john larkin wrote:
On Wed, 30 Oct 2024 00:02:34 +0100, Klaus Vestergaard Kragelund
<klauskvik@hotmail.com> wrote:
On 29-10-2024 18:26, john larkin wrote:
On Tue, 29 Oct 2024 17:02:02 -0000 (UTC), Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
john larkin <jl@glen--canyon.com> wrote:
On Mon, 28 Oct 2024 20:31:14 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
On 2024-10-28 17:10, john larkin wrote:
On Mon, 28 Oct 2024 15:49:30 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
On 2024-10-27 08:26, Klaus Vestergaard Kragelund wrote:
On 27-10-2024 03:26, john larkin wrote:
On Sun, 27 Oct 2024 02:19:14 +0200, Klaus Vestergaard Kragelund >>>>>>>>>>>> <klauskvik@hotmail.com> wrote:
The credit card experiment is morally equivalent to using two square
tubes stuck together.
Now mount two LEDS, red and green, to the common
wall, at the back of the tubes. Shine that at a wall. It should
project two fuzzy squares, red and green, barely overlapping, with a
fuzzy orange stripe between them.
That could actually be two IR LEDs modulated at different frequencies,
or two photodiodes.
TV remotes work very well, so I wouldn't expect s/n problems with the
emitter and detector staring at one another a few feet apart.
Use multiple LEDs stacked vertically along both sides of that back
wall (which should actually be a PCB) and apply a lot of square-wave
current.
We like the Osram right-angle surface-mount LEDs, but there are lots
of parts like that around.
https://www.vishay.com/docs/82491/tsop382.pdf
It has AGC, but digital output. I need analog output to be able to zero
in on the transmitter beam.
john larkin <JL@gct.com> wrote:
On Mon, 28 Oct 2024 20:19:25 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
On 2024-10-28 08:14, piglet wrote:
john larkin <JL@gct.com> wrote:
On Sun, 27 Oct 2024 22:59:59 -0000 (UTC), piglet
<erichpwagner@hotmail.com> wrote:
Klaus Vestergaard Kragelund <klauskvik@hotmail.com> wrote:
On 27-10-2024 13:26, Klaus Vestergaard Kragelund wrote:
On 27-10-2024 03:26, john larkin wrote:Actually, wont a simple high pass filter work equally well?
On Sun, 27 Oct 2024 02:19:14 +0200, Klaus Vestergaard Kragelund >>>>>>>>> <klauskvik@hotmail.com> wrote:
Hi
I am working on an IR detector that will guide a robot into a docking
station.
A IR transmitter on the docking station transmits a beam, and 2 IR >>>>>>>>>> detectors on the robot detects the beam and lets the robot navigate >>>>>>>>>> towards the target. The working distance is a couple of meters. >>>>>>>>>>
I need it to be insensitive to ambient light/sunlight.
The IR detectors are placed in a tube, to narrow in the beam angle and
to avoid sunlight (since it is seldom the sun is actually that low in
the horizon)
The IR transmitter will be modulated with 10kHz (TBD) frequency, low >>>>>>>>>> duty cycle. Low duty cycle to be able to drive the LED with high >>>>>>>>>> current, frequency modulated so that the receiver can ignore the effect
of daylight (DC)
If the LED on the docking station has higher radiant intensity at the
point of the robot (2 meters away) than possible IR from sunlight, then
that would be perfect.
Example of transmitter:
https://www.vishay.com/docs/83398/vsmy2850.pdf
Has up to 1000mW/sr. Seems my basic calculation for a 15 degree beam,
shows less than 10nW/m2, while sunlight has 1W/m2. So driving a beam >>>>>>>>>> that has higher output than sunlight seems unlikely.
I would use a IR phototransistor at 850nm, something like this: >>>>>>>>>>
https://www.ttelectronics.com/TTElectronics/media/ProductFiles/ >>>>>>>>>> Datasheet/OP505-506-535-705.pdf
Or a photo diode:
https://docs.rs-online.com/9f58/0900766b816d8a09.pdf
Fed from reverse 3.3V and into a transimpedance amplifier to boost the
signal with bandpass filter.
One can get digital IR detector used in a remote control systems: >>>>>>>>>>
https://www.vishay.com/docs/82491/tsop382.pdf
It has AGC, but digital output. I need analog output to be able to zero
in on the transmitter beam.
I have been looking for IR detectors that has the analog output, not >>>>>>>>>> just the digital, but have not found any.
If the photodiode detector is subjected to sunlight, I am guessing I >>>>>>>>>> would need very high gain on the 10kHz modulation frequency to pick up
the burried signal in the DC from sunlight.
How do I best bias the photo diode for optimum detection of the 10kHz
signal while being immune to the ambient sunlight?
I have chosen 850nm which seems to be a good wavelength. The spectrum at
sea level has some dips due to water absorption.
https://sciencetech-inc.com/web/image/49169/
Spectrum%20with_out%20absorption.png
Seems like 750nm would be better, since then the IR from the sun is >>>>>>>>>> lower, but does reduced the effective range of the system during >>>>>>>>>> fog/rain. Probably that's why these system do not use 750nm >>>>>>>>>>
Other considerations?
You could drive the LED with a square wave, 10 KHz or whatever. The >>>>>>>>> photodiode could have +DC on one end and the other end can hit a >>>>>>>>> parallel LC to ground, resonant at 10K.
That takes out the sunlight DC component and adds bandpass filtering. >>>>>>>>>
That's a very nice idea. The Q should not matter much, just as long as >>>>>>>> DC is removed.
The photodiode will still be subjected to the high ambient light, but >>>>>>>> the gain would be close to zero for the stage after. I would then still
need to be sure the photodiode is never saturated by ambient light. >>>>>>>>
Photo diode with bias -> capacitor to gain block....
If you make it part of the bias network yes, a gyrator either a single >>>>>> transistor or op amp could take the role of inductor.
When you need an inductor, an inductor makes an excellent inductor.
But the dual microphone thing, electret or mems, sounds like a much
better way to go.
Some folk are scared of inductors. 10kHz does mean quite a few milli
henries.
Of course they might be able to reverse the process and have one receiver >>>> on the robot and two emitters on the docking station, a bit like aircraft >>>> VOR
Or like certain radio navigation systems popular in Western Europe, 80
or so years ago. ;)
That's a good example of Horace Darwin's maxim, "Always try it the other >>> way round", quoted in "Instruments and Experiences" by R. V. Jones.
Jones is one of my technical heroes, and was instrumental in defeating a >>> couple of the aforementioned navigation systems, specifically
"Knickebein" and "X-Geraet", as explained in his book, "The Wizard War"
(entitled "Most Secret War" in the UK). Horace Darwin was a grandson of >>> Charles Darwin, and a colleague of Jones's at Aberdeen after the war.
Cheers
Phil Hobbs
https://www.amazon.com/Instruments-Experiences-Measurement-Instrument-Technology/dp/047191763X
Cheap at twice the price!
It’s a unique book—a collection of Jones’s groundbreaking papers on things >like measuring the ether drag on light in a moving dielectric, which would
be a niche interest except that each one is paired with an essay of about >equal length explaining how the measurement was done.
Those pieces are of lasting value—they’re confidential in tone, including
the inventions required, the blind alleys, and very often, how somebody
made a big difference with a piece of hard-won advice, like that remark of >Darwin’s.
Cheers
Phil Hobbs
On Tue, 29 Oct 2024 16:03:12 -0000 (UTC), Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:
john larkin <JL@gct.com> wrote:
On Mon, 28 Oct 2024 20:19:25 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
On 2024-10-28 08:14, piglet wrote:
john larkin <JL@gct.com> wrote:
On Sun, 27 Oct 2024 22:59:59 -0000 (UTC), piglet
<erichpwagner@hotmail.com> wrote:
Klaus Vestergaard Kragelund <klauskvik@hotmail.com> wrote:
On 27-10-2024 13:26, Klaus Vestergaard Kragelund wrote:
On 27-10-2024 03:26, john larkin wrote:Actually, wont a simple high pass filter work equally well?
On Sun, 27 Oct 2024 02:19:14 +0200, Klaus Vestergaard Kragelund >>>>>>>>>> <klauskvik@hotmail.com> wrote:
Hi
I am working on an IR detector that will guide a robot into a docking
station.
A IR transmitter on the docking station transmits a beam, and 2 IR >>>>>>>>>>> detectors on the robot detects the beam and lets the robot navigate >>>>>>>>>>> towards the target. The working distance is a couple of meters. >>>>>>>>>>>
I need it to be insensitive to ambient light/sunlight.
The IR detectors are placed in a tube, to narrow in the beam angle and
to avoid sunlight (since it is seldom the sun is actually that low in
the horizon)
The IR transmitter will be modulated with 10kHz (TBD) frequency, low
duty cycle. Low duty cycle to be able to drive the LED with high >>>>>>>>>>> current, frequency modulated so that the receiver can ignore the effect
of daylight (DC)
If the LED on the docking station has higher radiant intensity at the
point of the robot (2 meters away) than possible IR from sunlight, then
that would be perfect.
Example of transmitter:
https://www.vishay.com/docs/83398/vsmy2850.pdf
Has up to 1000mW/sr. Seems my basic calculation for a 15 degree beam,
shows less than 10nW/m2, while sunlight has 1W/m2. So driving a beam
that has higher output than sunlight seems unlikely.
I would use a IR phototransistor at 850nm, something like this: >>>>>>>>>>>
https://www.ttelectronics.com/TTElectronics/media/ProductFiles/ >>>>>>>>>>> Datasheet/OP505-506-535-705.pdf
Or a photo diode:
https://docs.rs-online.com/9f58/0900766b816d8a09.pdf
Fed from reverse 3.3V and into a transimpedance amplifier to boost the
signal with bandpass filter.
One can get digital IR detector used in a remote control systems: >>>>>>>>>>>
https://www.vishay.com/docs/82491/tsop382.pdf
It has AGC, but digital output. I need analog output to be able to zero
in on the transmitter beam.
I have been looking for IR detectors that has the analog output, not
just the digital, but have not found any.
If the photodiode detector is subjected to sunlight, I am guessing I
would need very high gain on the 10kHz modulation frequency to pick up
the burried signal in the DC from sunlight.
How do I best bias the photo diode for optimum detection of the 10kHz
signal while being immune to the ambient sunlight?
I have chosen 850nm which seems to be a good wavelength. The spectrum at
sea level has some dips due to water absorption.
https://sciencetech-inc.com/web/image/49169/
Spectrum%20with_out%20absorption.png
Seems like 750nm would be better, since then the IR from the sun is >>>>>>>>>>> lower, but does reduced the effective range of the system during >>>>>>>>>>> fog/rain. Probably that's why these system do not use 750nm >>>>>>>>>>>
Other considerations?
You could drive the LED with a square wave, 10 KHz or whatever. The >>>>>>>>>> photodiode could have +DC on one end and the other end can hit a >>>>>>>>>> parallel LC to ground, resonant at 10K.
That takes out the sunlight DC component and adds bandpass filtering.
That's a very nice idea. The Q should not matter much, just as long as
DC is removed.
The photodiode will still be subjected to the high ambient light, but >>>>>>>>> the gain would be close to zero for the stage after. I would then still
need to be sure the photodiode is never saturated by ambient light. >>>>>>>>>
Photo diode with bias -> capacitor to gain block....
If you make it part of the bias network yes, a gyrator either a single >>>>>>> transistor or op amp could take the role of inductor.
When you need an inductor, an inductor makes an excellent inductor. >>>>>>
But the dual microphone thing, electret or mems, sounds like a much >>>>>> better way to go.
Some folk are scared of inductors. 10kHz does mean quite a few milli >>>>> henries.
Of course they might be able to reverse the process and have one receiver >>>>> on the robot and two emitters on the docking station, a bit like aircraft >>>>> VOR
Or like certain radio navigation systems popular in Western Europe, 80 >>>> or so years ago. ;)
That's a good example of Horace Darwin's maxim, "Always try it the other >>>> way round", quoted in "Instruments and Experiences" by R. V. Jones.
Jones is one of my technical heroes, and was instrumental in defeating a >>>> couple of the aforementioned navigation systems, specifically
"Knickebein" and "X-Geraet", as explained in his book, "The Wizard War" >>>> (entitled "Most Secret War" in the UK). Horace Darwin was a grandson of >>>> Charles Darwin, and a colleague of Jones's at Aberdeen after the war.
Cheers
Phil Hobbs
https://www.amazon.com/Instruments-Experiences-Measurement-Instrument-Technology/dp/047191763X
Cheap at twice the price!
It’s a unique book—a collection of Jones’s groundbreaking papers on things
like measuring the ether drag on light in a moving dielectric, which would >> be a niche interest except that each one is paired with an essay of about
equal length explaining how the measurement was done.
Those pieces are of lasting value—they’re confidential in tone, including >> the inventions required, the blind alleys, and very often, how somebody
made a big difference with a piece of hard-won advice, like that remark of >> DarwinÂ’s.
Cheers
Phil Hobbs
One of my summer jobs in high school was working in the electronics
shop of the physics depertment of a local university. They registered
me as a fake student so they could pay me 70 cents per hour. I learned
a lot.
I designed some stuff for Mössbauer spectroscopy, which is astounding physics. Gamma-ray absorption lines turn out to be pretty high Q.
https://en.wikipedia.org/wiki/M%C3%B6ssbauer_spectroscopy
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