https://www.dropbox.com/scl/fi/weo0og6siaf5ano8thng3/Opto_Shift_Reg.jpg?rlkey=g170fs3jzg6zftzrrvr3phmd4&raw=1
A short low pulse shifts a 1 and a long pulse shifts a 0.
On 12/18/23 10:24, john larkin wrote:
https://www.dropbox.com/scl/fi/weo0og6siaf5ano8thng3/Opto_Shift_Reg.jpg?rlkey=g170fs3jzg6zftzrrvr3phmd4&raw=1Well,that's cute, but not useful without some guaranteed resting high
A short low pulse shifts a 1 and a long pulse shifts a 0.
time for the pulse train. If the cap doesn't recharge fully between low >intervals, it gets indeterminate as to what happens.
https://www.dropbox.com/scl/fi/weo0og6siaf5ano8thng3/Opto_Shift_Reg.jpg?rlkey=g170fs3jzg6zftzrrvr3phmd4&raw=1
A short low pulse shifts a 1 and a long pulse shifts a 0.
mandag den 18. december 2023 kl. 19.24.58 UTC+1 skrev john larkin:
https://www.dropbox.com/scl/fi/weo0og6siaf5ano8thng3/Opto_Shift_Reg.jpg?rlkey=g170fs3jzg6zftzrrvr3phmd4&raw=1
A short low pulse shifts a 1 and a long pulse shifts a 0.
sorta similar to these LED drivers, https://www.tme.eu/dk/en/details/ws2811-m/led-drivers/worldsemi/ws2811-msop8/
https://www.dropbox.com/scl/fi/weo0og6siaf5ano8thng3/Opto_Shift_Reg.jpg?rlkey=g170fs3jzg6zftzrrvr3phmd4&raw=1
A short low pulse shifts a 1 and a long pulse shifts a 0.
mandag den 18. december 2023 kl. 19.24.58 UTC+1 skrev john larkin:
https://www.dropbox.com/scl/fi/weo0og6siaf5ano8thng3/Opto_Shift_Reg.jpg?rlkey=g170fs3jzg6zftzrrvr3phmd4&raw=1
A short low pulse shifts a 1 and a long pulse shifts a 0.
sorta similar to these LED drivers, https://www.tme.eu/dk/en/details/ws2811-m/led-drivers/worldsemi/ws2811-msop8/
tirsdag den 19. december 2023 kl. 07.16.02 UTC+1 skrev Jan Panteltje:
On a sunny day (Mon, 18 Dec 2023 16:40:42 -0800 (PST)) it happened Lasse
Langwadt Christensen <lang...@fonz.dk> wrote in
<50752cee-2eb8-4219...@googlegroups.com>:
mandag den 18. december 2023 kl. 19.24.58 UTC+1 skrev john larkin:Interesting, thanks you.
https://www.dropbox.com/scl/fi/weo0og6siaf5ano8thng3/Opto_Shift_Reg.jpg?rlkey=g170fs3jzg6zftzrrvr3phmd4&raw=1
A short low pulse shifts a 1 and a long pulse shifts a 0.
sorta similar to these LED drivers, https://www.tme.eu/dk/en/details/ws2811-m/led-drivers/worldsemi/ws2811-msop8/
it is the same or similar IC build into an RGB led that is in those cheap individually addressable LED strips
https://www.aliexpress.com/item/4001322411818.html
On a sunny day (Mon, 18 Dec 2023 10:24:39 -0800) it happened john larkin ><jl@650pot.com> wrote in <re31oid9dqb1136cj5rctmnruvvhrm47nl@4ax.com>:
https://www.dropbox.com/scl/fi/weo0og6siaf5ano8thng3/Opto_Shift_Reg.jpg?rlkey=g170fs3jzg6zftzrrvr3phmd4&raw=1
A short low pulse shifts a 1 and a long pulse shifts a 0.
What,s the use?
tirsdag den 19. december 2023 kl. 16.32.07 UTC+1 skrev John Larkin:
On Tue, 19 Dec 2023 06:04:01 GMT, Jan Panteltje <al...@comet.invalid>
wrote:
On a sunny day (Mon, 18 Dec 2023 10:24:39 -0800) it happened john larkinOne channel of an isolated temperature acquisition box. It will do
<j...@650pot.com> wrote in <re31oid9dqb1136cj...@4ax.com>:
https://www.dropbox.com/scl/fi/weo0og6siaf5ano8thng3/Opto_Shift_Reg.jpg?rlkey=g170fs3jzg6zftzrrvr3phmd4&raw=1
A short low pulse shifts a 1 and a long pulse shifts a 0.
What,s the use?
RTDs, thermocouples, IC sensors, and cryo diodes. I need several
isolated logic levels to switch ranges and such, and a multi-channel
logic isolator is big and expensive. I don't need speed.
there's also, SN74LV8153, uart to 8 bit
On a sunny day (Tue, 19 Dec 2023 01:55:16 -0800 (PST)) it happened Lasse >Langwadt Christensen <langwadt@fonz.dk> wrote in ><0d59e35a-6272-49ea-aef6-51176f2b798dn@googlegroups.com>:
tirsdag den 19. december 2023 kl. 07.16.02 UTC+1 skrev Jan Panteltje:
On a sunny day (Mon, 18 Dec 2023 16:40:42 -0800 (PST)) it happened Lasse >>> Langwadt Christensen <lang...@fonz.dk> wrote in
<50752cee-2eb8-4219...@googlegroups.com>:
mandag den 18. december 2023 kl. 19.24.58 UTC+1 skrev john larkin:Interesting, thanks you.
https://www.dropbox.com/scl/fi/weo0og6siaf5ano8thng3/Opto_Shift_Reg.jpg?rlkey=g170fs3jzg6zftzrrvr3phmd4&raw=1
A short low pulse shifts a 1 and a long pulse shifts a 0.
sorta similar to these LED drivers, https://www.tme.eu/dk/en/details/ws2811-m/led-drivers/worldsemi/ws2811-msop8/
it is the same or similar IC build into an RGB led that is in those cheap individually addressable LED strips
https://www.aliexpress.com/item/4001322411818.html
Yea, if figured that, I have some normal LED strips here for Christmas
with those individual addressable strips you could make interesting displays >-but- I also have an old iconnect laser projector :-)
Really cool thing :-) Connected to a Raspberry Pi.
So I had not ordered those special LED strips.
On Tue, 19 Dec 2023 06:04:01 GMT, Jan Panteltje <alien@comet.invalid>
wrote:
On a sunny day (Mon, 18 Dec 2023 10:24:39 -0800) it happened john larkin >><jl@650pot.com> wrote in <re31oid9dqb1136cj5rctmnruvvhrm47nl@4ax.com>:
https://www.dropbox.com/scl/fi/weo0og6siaf5ano8thng3/Opto_Shift_Reg.jpg?rlkey=g170fs3jzg6zftzrrvr3phmd4&raw=1
A short low pulse shifts a 1 and a long pulse shifts a 0.
What,s the use?
One channel of an isolated temperature acquisition box. It will do
RTDs, thermocouples, IC sensors, and cryo diodes. I need several
isolated logic levels to switch ranges and such, and a multi-channel
logic isolator is big and expensive. I don't need speed.
The alternative is to use a bunch of single-lane SSRs.
Or maybe float a uP per channel and talk to it with one bidirectional >isolator.
Early stages of design, many possibilities.
On Tue, 19 Dec 2023 06:04:01 GMT, Jan Panteltje <alien@comet.invalid>
wrote:
On a sunny day (Mon, 18 Dec 2023 10:24:39 -0800) it happened john larkin
<jl@650pot.com> wrote in <re31oid9dqb1136cj5rctmnruvvhrm47nl@4ax.com>:
https://www.dropbox.com/scl/fi/weo0og6siaf5ano8thng3/Opto_Shift_Reg.jpg?rlkey=g170fs3jzg6zftzrrvr3phmd4&raw=1
A short low pulse shifts a 1 and a long pulse shifts a 0.
What,s the use?
One channel of an isolated temperature acquisition box. It will do
RTDs, thermocouples, IC sensors, and cryo diodes. I need several
isolated logic levels to switch ranges and such, and a multi-channel
logic isolator is big and expensive. I don't need speed.
The alternative is to use a bunch of single-lane SSRs.
Or maybe float a uP per channel and talk to it with one bidirectional isolator.
Early stages of design, many possibilities.
On a sunny day (Tue, 19 Dec 2023 07:31:03 -0800) it happened John Larkin ><jl@997PotHill.com> wrote in <r9d3oipchi8i1no29gu1rlccg0mlnn3llc@4ax.com>:
On Tue, 19 Dec 2023 06:04:01 GMT, Jan Panteltje <alien@comet.invalid> >>wrote:
On a sunny day (Mon, 18 Dec 2023 10:24:39 -0800) it happened john larkin >>><jl@650pot.com> wrote in <re31oid9dqb1136cj5rctmnruvvhrm47nl@4ax.com>:
https://www.dropbox.com/scl/fi/weo0og6siaf5ano8thng3/Opto_Shift_Reg.jpg?rlkey=g170fs3jzg6zftzrrvr3phmd4&raw=1
A short low pulse shifts a 1 and a long pulse shifts a 0.
What,s the use?
One channel of an isolated temperature acquisition box. It will do
RTDs, thermocouples, IC sensors, and cryo diodes. I need several
isolated logic levels to switch ranges and such, and a multi-channel
logic isolator is big and expensive. I don't need speed.
The alternative is to use a bunch of single-lane SSRs.
Or maybe float a uP per channel and talk to it with one bidirectional >>isolator.
Early stages of design, many possibilities.
For that, if I understand your description right,
I usually grab a Microchip PIC micro.
It has many outputs that can drive optocouplers,
both for in - and outputs.
Then it can do Ethernet to a main computer too with one extra chip.
I am a bit worried about the timing capacitors in your idea,
caps may drift over time and temperature?
On Wed, 20 Dec 2023 05:18:42 GMT, Jan Panteltje <alien@comet.invalid>
wrote:
On a sunny day (Tue, 19 Dec 2023 07:31:03 -0800) it happened John Larkin >><jl@997PotHill.com> wrote in <r9d3oipchi8i1no29gu1rlccg0mlnn3llc@4ax.com>:
On Tue, 19 Dec 2023 06:04:01 GMT, Jan Panteltje <alien@comet.invalid> >>>wrote:
On a sunny day (Mon, 18 Dec 2023 10:24:39 -0800) it happened john larkin >>>><jl@650pot.com> wrote in <re31oid9dqb1136cj5rctmnruvvhrm47nl@4ax.com>:
https://www.dropbox.com/scl/fi/weo0og6siaf5ano8thng3/Opto_Shift_Reg.jpg?rlkey=g170fs3jzg6zftzrrvr3phmd4&raw=1
A short low pulse shifts a 1 and a long pulse shifts a 0.
What,s the use?
One channel of an isolated temperature acquisition box. It will do
RTDs, thermocouples, IC sensors, and cryo diodes. I need several
isolated logic levels to switch ranges and such, and a multi-channel >>>logic isolator is big and expensive. I don't need speed.
The alternative is to use a bunch of single-lane SSRs.
Or maybe float a uP per channel and talk to it with one bidirectional >>>isolator.
Early stages of design, many possibilities.
For that, if I understand your description right,
I usually grab a Microchip PIC micro.
It has many outputs that can drive optocouplers,
both for in - and outputs.
Then it can do Ethernet to a main computer too with one extra chip.
I am a bit worried about the timing capacitors in your idea,
caps may drift over time and temperature?
I plan to use one RP2040 in the box, as the top level manager. The
question is then how to talk to four isolated temprature measurement >channels. People sometimes weld thermocouples to whatever, or bolt raw
cryo diodes to metal things, so I need true isolation.
A uP per channel is probably overkill. I've done that before but it's
a nuisance.
If I do the long/short pulse thing, the pulse width ratio can be 10:1
or 100:1 so capacitor tolerance wouldn't matter.
On Monday, December 18, 2023 at 1:24:58?PM UTC-5, john larkin wrote:
https://www.dropbox.com/scl/fi/weo0og6siaf5ano8thng3/Opto_Shift_Reg.jpg?rlkey=g170fs3jzg6zftzrrvr3phmd4&raw=1
A short low pulse shifts a 1 and a long pulse shifts a 0.
You can't beat that for simplicity and reliability. The first bit always has to be a 0,
and you probably want to blank the output whenever you put the register into a new state.
https://www.dropbox.com/scl/fi/weo0og6siaf5ano8thng3/Opto_Shift_Reg.jpg?rlkey=g170fs3jzg6zftzrrvr3phmd4&raw=1A short low pulse shifts a 1 and a long pulse shifts a 0.
On a sunny day (Wed, 20 Dec 2023 04:20:54 -0800) it happened John Larkin ><jl@997PotHill.com> wrote in <lim5oi5afhvee38tb5can9id36k1bgcic9@4ax.com>:
On Wed, 20 Dec 2023 05:18:42 GMT, Jan Panteltje <alien@comet.invalid> >>wrote:
On a sunny day (Tue, 19 Dec 2023 07:31:03 -0800) it happened John Larkin >>><jl@997PotHill.com> wrote in <r9d3oipchi8i1no29gu1rlccg0mlnn3llc@4ax.com>: >>>
On Tue, 19 Dec 2023 06:04:01 GMT, Jan Panteltje <alien@comet.invalid> >>>>wrote:
On a sunny day (Mon, 18 Dec 2023 10:24:39 -0800) it happened john larkin >>>>><jl@650pot.com> wrote in <re31oid9dqb1136cj5rctmnruvvhrm47nl@4ax.com>: >>>>> >>>>>>https://www.dropbox.com/scl/fi/weo0og6siaf5ano8thng3/Opto_Shift_Reg.jpg?rlkey=g170fs3jzg6zftzrrvr3phmd4&raw=1
A short low pulse shifts a 1 and a long pulse shifts a 0.
What,s the use?
One channel of an isolated temperature acquisition box. It will do >>>>RTDs, thermocouples, IC sensors, and cryo diodes. I need several >>>>isolated logic levels to switch ranges and such, and a multi-channel >>>>logic isolator is big and expensive. I don't need speed.
The alternative is to use a bunch of single-lane SSRs.
Or maybe float a uP per channel and talk to it with one bidirectional >>>>isolator.
Early stages of design, many possibilities.
For that, if I understand your description right,
I usually grab a Microchip PIC micro.
It has many outputs that can drive optocouplers,
both for in - and outputs.
Then it can do Ethernet to a main computer too with one extra chip.
I am a bit worried about the timing capacitors in your idea,
caps may drift over time and temperature?
I plan to use one RP2040 in the box, as the top level manager. The
question is then how to talk to four isolated temprature measurement >>channels. People sometimes weld thermocouples to whatever, or bolt raw
cryo diodes to metal things, so I need true isolation.
A uP per channel is probably overkill. I've done that before but it's
a nuisance.
Well the thing will have to understand commands, and sent data..
or is it just one-way traffic? sensor to raspberry?
Using logic takes more chips than a micro.
If I do the long/short pulse thing, the pulse width ratio can be 10:1
or 100:1 so capacitor tolerance wouldn't matter.
Looks like a simple serial protocol like for example used via PC serial port would be OK.
2 photo couplers per channel, one for each direction,
You need supply insulation too, so one potcore at RF with a few flat cable thick windings, one for each sensor unit
https://www.panteltje.online/pub/1_to_1_transformer_in_1_minute.jpg
1 transistor sine wave oscillator to power all units:
https://www.panteltje.online/pub/tuned_eprom_programmer_voltage_generator.gif
Raspi can mimic several serial ports via the GPIO pins.
Depends a bit how many task interups happen via the software.
On the Pi4 there seem to be 4 hardware serial ports?
https://forums.raspberrypi.com/viewtopic.php?t=244528
I only ever used ttyAMA0 (GPS module connected to it).
On Tue, 19 Dec 2023 06:04:01 GMT, Jan Panteltje <alien@comet.invalid>
wrote:
On a sunny day (Mon, 18 Dec 2023 10:24:39 -0800) it happened john larkin >><jl@650pot.com> wrote in <re31oid9dqb1136cj5rctmnruvvhrm47nl@4ax.com>:
https://www.dropbox.com/scl/fi/weo0og6siaf5ano8thng3/Opto_Shift_Reg.jpg?rlkey=g170fs3jzg6zftzrrvr3phmd4&raw=1
A short low pulse shifts a 1 and a long pulse shifts a 0.
What,s the use?
One channel of an isolated temperature acquisition box. It will do
RTDs, thermocouples, IC sensors, and cryo diodes. I need several
isolated logic levels to switch ranges and such, and a multi-channel
logic isolator is big and expensive. I don't need speed.
The alternative is to use a bunch of single-lane SSRs.
Or maybe float a uP per channel and talk to it with one bidirectional >isolator.
Early stages of design, many possibilities.
On Tue, 19 Dec 2023 07:31:03 -0800, John Larkin <jl@997PotHill.com>
wrote:
On Tue, 19 Dec 2023 06:04:01 GMT, Jan Panteltje <alien@comet.invalid> >>wrote:
On a sunny day (Mon, 18 Dec 2023 10:24:39 -0800) it happened john larkin >>><jl@650pot.com> wrote in <re31oid9dqb1136cj5rctmnruvvhrm47nl@4ax.com>:
https://www.dropbox.com/scl/fi/weo0og6siaf5ano8thng3/Opto_Shift_Reg.jpg?rlkey=g170fs3jzg6zftzrrvr3phmd4&raw=1
A short low pulse shifts a 1 and a long pulse shifts a 0.
What,s the use?
One channel of an isolated temperature acquisition box. It will do
RTDs, thermocouples, IC sensors, and cryo diodes. I need several
isolated logic levels to switch ranges and such, and a multi-channel
logic isolator is big and expensive. I don't need speed.
The alternative is to use a bunch of single-lane SSRs.
Or maybe float a uP per channel and talk to it with one bidirectional >>isolator.
Early stages of design, many possibilities.
Incidentally, cryo diodes are interesting parts. They are just >well-charactized small diodes, or maybe diode-connected transistors.
They act like normal diodes down to around 20K, and then "carrier
freeze-out" kicks in and voltage drop goes way up as temp goes down. I
think they get ohmic too.
Lakeshore makes good ones. They are specified at 10 uA forward
current, probably to minimize self-heating.
https://www.lakeshore.com/products/categories/overview/temperature-products/cryogenic-temperature-sensors/dt-670-silicon-diodes
I think transistor action stops below 20K too. I recall that jfets
still work cold.
On Wed, 20 Dec 2023 13:04:58 GMT, Jan Panteltje <alien@comet.invalid>
wrote:
On a sunny day (Wed, 20 Dec 2023 04:20:54 -0800) it happened John Larkin >><jl@997PotHill.com> wrote in <lim5oi5afhvee38tb5can9id36k1bgcic9@4ax.com>:
On Wed, 20 Dec 2023 05:18:42 GMT, Jan Panteltje <alien@comet.invalid> >>>wrote:
On a sunny day (Tue, 19 Dec 2023 07:31:03 -0800) it happened John Larkin >>>><jl@997PotHill.com> wrote in <r9d3oipchi8i1no29gu1rlccg0mlnn3llc@4ax.com>: >>>>
On Tue, 19 Dec 2023 06:04:01 GMT, Jan Panteltje <alien@comet.invalid> >>>>>wrote:
On a sunny day (Mon, 18 Dec 2023 10:24:39 -0800) it happened john larkin >>>>>><jl@650pot.com> wrote in <re31oid9dqb1136cj5rctmnruvvhrm47nl@4ax.com>: >>>>>> >>>>>>>https://www.dropbox.com/scl/fi/weo0og6siaf5ano8thng3/Opto_Shift_Reg.jpg?rlkey=g170fs3jzg6zftzrrvr3phmd4&raw=1
A short low pulse shifts a 1 and a long pulse shifts a 0.
What,s the use?
One channel of an isolated temperature acquisition box. It will do >>>>>RTDs, thermocouples, IC sensors, and cryo diodes. I need several >>>>>isolated logic levels to switch ranges and such, and a multi-channel >>>>>logic isolator is big and expensive. I don't need speed.
The alternative is to use a bunch of single-lane SSRs.
Or maybe float a uP per channel and talk to it with one bidirectional >>>>>isolator.
Early stages of design, many possibilities.
For that, if I understand your description right,
I usually grab a Microchip PIC micro.
It has many outputs that can drive optocouplers,
both for in - and outputs.
Then it can do Ethernet to a main computer too with one extra chip.
I am a bit worried about the timing capacitors in your idea,
caps may drift over time and temperature?
I plan to use one RP2040 in the box, as the top level manager. The >>>question is then how to talk to four isolated temprature measurement >>>channels. People sometimes weld thermocouples to whatever, or bolt raw >>>cryo diodes to metal things, so I need true isolation.
A uP per channel is probably overkill. I've done that before but it's
a nuisance.
Well the thing will have to understand commands, and sent data..
or is it just one-way traffic? sensor to raspberry?
Using logic takes more chips than a micro.
If I do the long/short pulse thing, the pulse width ratio can be 10:1
or 100:1 so capacitor tolerance wouldn't matter.
Looks like a simple serial protocol like for example used via PC serial port would be OK.
2 photo couplers per channel, one for each direction,
You need supply insulation too, so one potcore at RF with a few flat cable thick windings, one for each sensor unit
https://www.panteltje.online/pub/1_to_1_transformer_in_1_minute.jpg
It will take more than a minute to mount and connect that on a PCB.
1 transistor sine wave oscillator to power all units:
https://www.panteltje.online/pub/tuned_eprom_programmer_voltage_generator.gif
A stock tiny surface-mount isolated dc/dc converter costs about $2.
Raspi can mimic several serial ports via the GPIO pins.
Depends a bit how many task interups happen via the software.
On the Pi4 there seem to be 4 hardware serial ports?
https://forums.raspberrypi.com/viewtopic.php?t=244528
I only ever used ttyAMA0 (GPS module connected to it).
I could bit-bang it too. But I'll use the Pico processor, the RP2040
chip. The Pi4 is about as big as my entire product!
One might use Ethernet magnetics, two transformers, as a logic
isolator too. Clock and data.
On a sunny day (Wed, 20 Dec 2023 17:53:13 -0800) it happened John Larkin ><jl@997PotHill.com> wrote in <eo57oi5oooqal8g9hc60c0iq2i87mmbs4f@4ax.com>:
On Tue, 19 Dec 2023 07:31:03 -0800, John Larkin <jl@997PotHill.com>
wrote:
On Tue, 19 Dec 2023 06:04:01 GMT, Jan Panteltje <alien@comet.invalid> >>>wrote:
On a sunny day (Mon, 18 Dec 2023 10:24:39 -0800) it happened john larkin >>>><jl@650pot.com> wrote in <re31oid9dqb1136cj5rctmnruvvhrm47nl@4ax.com>:
https://www.dropbox.com/scl/fi/weo0og6siaf5ano8thng3/Opto_Shift_Reg.jpg?rlkey=g170fs3jzg6zftzrrvr3phmd4&raw=1
A short low pulse shifts a 1 and a long pulse shifts a 0.
What,s the use?
One channel of an isolated temperature acquisition box. It will do
RTDs, thermocouples, IC sensors, and cryo diodes. I need several
isolated logic levels to switch ranges and such, and a multi-channel >>>logic isolator is big and expensive. I don't need speed.
The alternative is to use a bunch of single-lane SSRs.
Or maybe float a uP per channel and talk to it with one bidirectional >>>isolator.
Early stages of design, many possibilities.
Incidentally, cryo diodes are interesting parts. They are just >>well-charactized small diodes, or maybe diode-connected transistors.
They act like normal diodes down to around 20K, and then "carrier >>freeze-out" kicks in and voltage drop goes way up as temp goes down. I >>think they get ohmic too.
Lakeshore makes good ones. They are specified at 10 uA forward
current, probably to minimize self-heating.
https://www.lakeshore.com/products/categories/overview/temperature-products/cryogenic-temperature-sensors/dt-670-silicon-diodes
I think transistor action stops below 20K too. I recall that jfets
still work cold.
Thermocouples work fine too:
https://panteltje.online/pub/cryo/
you can make your own, and the electronics that comes with it:
https://panteltje.online/panteltje/pic/th_pic/
Exploring things is fun.
Curiosity :-)
and then apply it when needed!
On Thu, 21 Dec 2023 06:13:42 GMT, Jan Panteltje <alien@comet.invalid>
wrote:
On a sunny day (Wed, 20 Dec 2023 17:53:13 -0800) it happened John Larkin
<jl@997PotHill.com> wrote in <eo57oi5oooqal8g9hc60c0iq2i87mmbs4f@4ax.com>: >>> On Tue, 19 Dec 2023 07:31:03 -0800, John Larkin <jl@997PotHill.com>
wrote:
On Tue, 19 Dec 2023 06:04:01 GMT, Jan Panteltje <alien@comet.invalid>
wrote:
On a sunny day (Mon, 18 Dec 2023 10:24:39 -0800) it happened john larkin >>>>> <jl@650pot.com> wrote in <re31oid9dqb1136cj5rctmnruvvhrm47nl@4ax.com>:
Temperature measurement is generally nasty. I could rant about Global
Warming instrumentation but I won't.
On Thursday, December 21, 2023 at 5:15:27?AM UTC-8, John Larkin wrote:
On Thu, 21 Dec 2023 06:13:42 GMT, Jan Panteltje <al...@comet.invalid>
wrote:
Thermocouples work fine too:
https://panteltje.online/pub/cryo/
you can make your own, and the electronics that comes with it:
https://panteltje.online/panteltje/pic/th_pic/
How low can a thermocouple work?It's not so great at the lowest temperatures; I've used gold/ 0.7%Fe versus gold
for helium temperatures, but sensitivity is poor. That third law of thermodynamics
says it fails at zero.
On Thu, 21 Dec 2023 06:13:42 GMT, Jan Panteltje <alien@comet.invalid>
wrote:
On a sunny day (Wed, 20 Dec 2023 17:53:13 -0800) it happened John Larkin >><jl@997PotHill.com> wrote in <eo57oi5oooqal8g9hc60c0iq2i87mmbs4f@4ax.com>:
On Tue, 19 Dec 2023 07:31:03 -0800, John Larkin <jl@997PotHill.com> >>>wrote:
On Tue, 19 Dec 2023 06:04:01 GMT, Jan Panteltje <alien@comet.invalid> >>>>wrote:
On a sunny day (Mon, 18 Dec 2023 10:24:39 -0800) it happened john larkin >>>>><jl@650pot.com> wrote in <re31oid9dqb1136cj5rctmnruvvhrm47nl@4ax.com>: >>>>> >>>>>>https://www.dropbox.com/scl/fi/weo0og6siaf5ano8thng3/Opto_Shift_Reg.jpg?rlkey=g170fs3jzg6zftzrrvr3phmd4&raw=1
A short low pulse shifts a 1 and a long pulse shifts a 0.
What,s the use?
One channel of an isolated temperature acquisition box. It will do >>>>RTDs, thermocouples, IC sensors, and cryo diodes. I need several >>>>isolated logic levels to switch ranges and such, and a multi-channel >>>>logic isolator is big and expensive. I don't need speed.
The alternative is to use a bunch of single-lane SSRs.
Or maybe float a uP per channel and talk to it with one bidirectional >>>>isolator.
Early stages of design, many possibilities.
Incidentally, cryo diodes are interesting parts. They are just >>>well-charactized small diodes, or maybe diode-connected transistors.
They act like normal diodes down to around 20K, and then "carrier >>>freeze-out" kicks in and voltage drop goes way up as temp goes down. I >>>think they get ohmic too.
Lakeshore makes good ones. They are specified at 10 uA forward
current, probably to minimize self-heating.
https://www.lakeshore.com/products/categories/overview/temperature-products/cryogenic-temperature-sensors/dt-670-silicon-diodes
I think transistor action stops below 20K too. I recall that jfets
still work cold.
Thermocouples work fine too:
https://panteltje.online/pub/cryo/
you can make your own, and the electronics that comes with it:
https://panteltje.online/panteltje/pic/th_pic/
Exploring things is fun.
For sure. And the physics boys often need help with electronics. You
would think...
Curiosity :-)
and then apply it when needed!
How low can a thermocouple work? Any error in the reference junction
temp measurement is additive (or worse) and that matters near 0K. What
did you use for the ref junction measurement?
We usually use a platinum RTD working against a Susumu super-resistor.
Old carbon comp resistors have been used as cryo temp sensors, but I
think they need to be individually calibrated.
Lakeshore has a bunch of exotic cryo sensors.
Temperature measurement is generally nasty. I could rant about Global
Warming instrumentation but I won't.
A short low pulse shifts a 1 and a long pulse shifts a 0.
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