I used to know all this many years ago... how to work out the flux
density, and choose a material which doesn't saturate, but I have long >forgotten!
It needs to be good with a 13V peak square wave, 500Hz.
So we have 13V across 8mH for 1ms, which from v = L (di/dt) yields
1.625A. A quick hack in LTspice confirms this, for the first 5 cycles.
I had a lot of trouble generating a square wave from -13V to +13V :)
so I am not sure what the current waveform will look like when you
switch to -13V when the current flowing is still 1.625A; I suspect it
will not ever exceed 1.625A later though. With a 13V peak sinewave (a >predefined function in LTspice) it looked to be just under 1A, but all >positive which is obviously BS.
The bit I have forgotten is how to calculate the flux density in the
core. I would prefer the whole thing to be something the size of an
RM10 core
https://www.farnell.com/datasheets/528671.pdf
In 3C95 material you have 5500nH/T^2.
A toroid would have less stray flux, and again there is a vast choice.
I have a bag of these from many years ago >https://www.tme.eu/gb/details/tn16_9.6-3f3/ring-ferrites/ferroxcube/tn16-9-6-6-3-3f3/
which with 83 turns would achieve 8mH.
What I don't get is how much current this will carry. 83 turns at 1.6A
is 132 AT which sounds an awful lot. I thus suspect I will need a
bigger core, probably iron.
Looking on Ebay for ready made stuff, 10mH, I see e.g. >https://www.ebay.co.uk/itm/115852064002
but I am instinctively damn sure that won't carry the current.
Another option is some toroidal transformer, and ignore the existing
winding and put more turns on it. Ebay is full of vintage transformers
but most are pretty big.
I was going to wind the TN16 with some turns and see what it does. I
have an HP 3314 pulse generator and a power amp which can output 9V
peak.
The 8mH needs to be +/- 0.3mH. It was determined experimentally using
this amazing thing
https://www.ebay.co.uk/itm/224101042113
but that obviously contains massive magnetics - it weighs about 1kg.
I also have an LCR meter.
I'd be grateful for any suggestions.
To make a square wave in LT Spice, use a voltage source, right-click >'advanced' and then 'pulse' and set the params to get what looks
right.
Or run a sine wave through a BV block with some equation. That makes
it easy to change the frequency and keep 50% duty cycle.
The easy way to 'design' an inductor is to buy one. Most suppliers
specify L and R and max current and saturation current. Even if you
enjoy winding inductors, a standard part is a good sanity check.
LCR meters usually lie when measuring power inductors.
What's your application?
John Larkin <jl@997PotHill.com> wrote
To make a square wave in LT Spice, use a voltage source, right-click >>'advanced' and then 'pulse' and set the params to get what looks
right.
Or run a sine wave through a BV block with some equation. That makes
it easy to change the frequency and keep 50% duty cycle.
The easy way to 'design' an inductor is to buy one. Most suppliers
specify L and R and max current and saturation current. Even if you
enjoy winding inductors, a standard part is a good sanity check.
LCR meters usually lie when measuring power inductors.
What's your application?
It is to reduce the output from an LVDT, by putting this in series
with the input. The reason for reducing the output is a bit obscure...
I used to know all this many years ago... how to work out the flux
density, and choose a material which doesn't saturate, but I have long >forgotten!
It needs to be good with a 13V peak square wave, 500Hz.
So we have 13V across 8mH for 1ms, which from v = L (di/dt) yields
1.625A. A quick hack in LTspice confirms this, for the first 5 cycles.
I had a lot of trouble generating a square wave from -13V to +13V :)
so I am not sure what the current waveform will look like when you
switch to -13V when the current flowing is still 1.625A; I suspect it
will not ever exceed 1.625A later though. With a 13V peak sinewave (a >predefined function in LTspice) it looked to be just under 1A, but all >positive which is obviously BS.
The bit I have forgotten is how to calculate the flux density in the
core. I would prefer the whole thing to be something the size of an
RM10 core
https://www.farnell.com/datasheets/528671.pdf
In 3C95 material you have 5500nH/T^2.
A toroid would have less stray flux, and again there is a vast choice.
I have a bag of these from many years ago >https://www.tme.eu/gb/details/tn16_9.6-3f3/ring-ferrites/ferroxcube/tn16-9-6-6-3-3f3/
which with 83 turns would achieve 8mH.
What I don't get is how much current this will carry. 83 turns at 1.6A
is 132 AT which sounds an awful lot. I thus suspect I will need a
bigger core, probably iron.
Looking on Ebay for ready made stuff, 10mH, I see e.g. >https://www.ebay.co.uk/itm/115852064002
but I am instinctively damn sure that won't carry the current.
Another option is some toroidal transformer, and ignore the existing
winding and put more turns on it. Ebay is full of vintage transformers
but most are pretty big.
I was going to wind the TN16 with some turns and see what it does. I
have an HP 3314 pulse generator and a power amp which can output 9V
peak.
The 8mH needs to be +/- 0.3mH. It was determined experimentally using
this amazing thing
https://www.ebay.co.uk/itm/224101042113
but that obviously contains massive magnetics - it weighs about 1kg.
I also have an LCR meter.
I'd be grateful for any suggestions.
On Tue, 30 Jan 2024 16:13:41 +0000, Peter ><occassionally-confused@nospam.co.uk> wrote:
I used to know all this many years ago... how to work out the flux
density, and choose a material which doesn't saturate, but I have long >>forgotten!
Don't be surprised. It's common to have to brush up on basics, if
you don't use them regularly.
It needs to be good with a 13V peak square wave, 500Hz.
So we have 13V across 8mH for 1ms, which from v = L (di/dt) yields
1.625A. A quick hack in LTspice confirms this, for the first 5 cycles.
I had a lot of trouble generating a square wave from -13V to +13V :)
so I am not sure what the current waveform will look like when you
switch to -13V when the current flowing is still 1.625A; I suspect it
will not ever exceed 1.625A later though. With a 13V peak sinewave (a >>predefined function in LTspice) it looked to be just under 1A, but all >>positive which is obviously BS.
Your AC source is seen by the sim to have the polarity of the first
+ pulse. The -pulse that follows can only return mag current to
zero, hence a net +DC can show up in early portions of the sim.
Ad a load to get AC-only current, eventually.
The bit I have forgotten is how to calculate the flux density in the
core. I would prefer the whole thing to be something the size of an
RM10 core
https://www.farnell.com/datasheets/528671.pdf
In 3C95 material you have 5500nH/T^2.
A toroid would have less stray flux, and again there is a vast choice.
I have a bag of these from many years ago >>https://www.tme.eu/gb/details/tn16_9.6-3f3/ring-ferrites/ferroxcube/tn16-9-6-6-3-3f3/
which with 83 turns would achieve 8mH.
What I don't get is how much current this will carry. 83 turns at 1.6A
is 132 AT which sounds an awful lot. I thus suspect I will need a
bigger core, probably iron.
RM10 DC saturation current will depend on turns count and
gap. Saturation flux in ferrite is ~0.33T.
B = u N I / lm
B = flux density in Teslas
u = 4.pi.E-7
N = turns count
I = current in Amps
lm = magnetic path length (or gap width, if present) in meters.
For pulsed DC
deltsB = V T / N Ae
deltaB = flux density change in Teslas
V = applied volts in Volts
T = time in seconds
N = turns count
Ae = cross-sectional area of flux path im meters^2
inductance of gapped structure
L = 4.pi.E-7 N^2 Ae / lg
L = inductance in Henries
N = turns count
Ae = cross-sectional area of flux path im meters^2
lg = gap width in meters
Looking on Ebay for ready made stuff, 10mH, I see e.g. >>https://www.ebay.co.uk/itm/115852064002
but I am instinctively damn sure that won't carry the current.
Another option is some toroidal transformer, and ignore the existing >>winding and put more turns on it. Ebay is full of vintage transformers
but most are pretty big.
Solutions will depend on whether or not you intend to use the part
in AC-only, small signal situations, or whether the part is intended
to do some work in a resonant power or filter circuit.
I was going to wind the TN16 with some turns and see what it does. I
have an HP 3314 pulse generator and a power amp which can output 9V
peak.
The 8mH needs to be +/- 0.3mH. It was determined experimentally using
this amazing thing
https://www.ebay.co.uk/itm/224101042113
but that obviously contains massive magnetics - it weighs about 1kg.
I also have an LCR meter.
I'd be grateful for any suggestions.
Check what's on offer in distributors' catalogs. This will give
you a ball park idea of the size and shape of stuff you'll be
aiming for and may offer a simple solution off the shelf.
RL
I used to know all this many years ago... how to work out the flux
density, and choose a material which doesn't saturate, but I have long >forgotten!
It needs to be good with a 13V peak square wave, 500Hz.
core. I would prefer the whole thing to be something the size of an
RM10 core
https://www.farnell.com/datasheets/528671.pdf
In 3C95 material you have 5500nH/T^2.
I have a bag of these from many years ago >https://www.tme.eu/gb/details/tn16_9.6-3f3/ring-ferrites/ferroxcube/tn16-9-6-6-3-3f3/<snip>
which with 83 turns would achieve 8mH.
What I don't get is how much current this will carry.
Looking on Ebay for ready made stuff, 10mH, I see e.g. >https://www.ebay.co.uk/itm/115852064002
but I am instinctively damn sure that won't carry the current.
I was going to wind the TN16 with some turns and see what it does. I<snip..
have an HP 3314 pulse generator and a power amp which can output 9V
peak.
It is unusual to run a square wave into an LVDT. If the source is a
too-big square wave, a simple circuit would shape it into the
appropriate amplitude sine. Two or three parts.
It is unusual to run a square wave into an LVDT. If the source is a
too-big square wave, a simple circuit would shape it into the
appropriate amplitude sine. Two or three parts.
I see no reference to an LVDT application in the Peter's posting.
On Wed, 31 Jan 2024 09:04:20 -0800, John Larkin <jl@997PotHill.com>
wrote:
<snip>
It is unusual to run a square wave into an LVDT. If the source is a
too-big square wave, a simple circuit would shape it into the
appropriate amplitude sine. Two or three parts.
I see no reference to an LVDT application in the Peter's posting.
RL
On Thu, 01 Feb 2024 09:35:56 -0500, legg <legg@nospam.magma.ca> wrote:
On Wed, 31 Jan 2024 09:04:20 -0800, John Larkin <jl@997PotHill.com>
wrote:
<snip>
It is unusual to run a square wave into an LVDT. If the source is a >>>too-big square wave, a simple circuit would shape it into the
appropriate amplitude sine. Two or three parts.
I see no reference to an LVDT application in the Peter's posting.
RL
Subject: Re: How to make an 8mH inductor which can handle 13V peak
square wave without saturation
Date: Tue, 30 Jan 2024 20:32:25 +0000
legg <legg@nospam.magma.ca> wrote:
It is unusual to run a square wave into an LVDT. If the source is a >>>too-big square wave, a simple circuit would shape it into the
appropriate amplitude sine. Two or three parts.
I see no reference to an LVDT application in the Peter's posting.
It is an instrument which contains an LVDT bent into a half circle, to
return an angle.
It is excited with 500Hz, and it is pretty well a square wave. I
didn't design that bit :) And the output is too high, for reasons too
complex to explain. So I need to reduce the output somehow.
On Thu, 01 Feb 2024 08:01:11 -0800, John Larkin <jl@997PotHill.com>
wrote:
On Thu, 01 Feb 2024 09:35:56 -0500, legg <legg@nospam.magma.ca> wrote:
On Wed, 31 Jan 2024 09:04:20 -0800, John Larkin <jl@997PotHill.com> >>>wrote:
<snip>
It is unusual to run a square wave into an LVDT. If the source is a >>>>too-big square wave, a simple circuit would shape it into the >>>>appropriate amplitude sine. Two or three parts.
I see no reference to an LVDT application in the Peter's posting.
RL
Subject: Re: How to make an 8mH inductor which can handle 13V peak
square wave without saturation
Date: Tue, 30 Jan 2024 20:32:25 +0000
Not on this reader. I have only:
Tue, 30 Jan 2024 16:13:41
RL
legg <legg@nospam.magma.ca> wrote:
It is unusual to run a square wave into an LVDT. If the source is a
too-big square wave, a simple circuit would shape it into the
appropriate amplitude sine. Two or three parts.
I see no reference to an LVDT application in the Peter's posting.
It is an instrument which contains an LVDT bent into a half circle, to
return an angle.
It is excited with 500Hz, and it is pretty well a square wave. I
didn't design that bit :) And the output is too high, for reasons too
complex to explain. So I need to reduce the output somehow.
legg <legg@nospam.magma.ca> wrote:
It is unusual to run a square wave into an LVDT. If the source is a >>>too-big square wave, a simple circuit would shape it into the
appropriate amplitude sine. Two or three parts.
I see no reference to an LVDT application in the Peter's posting.
It is an instrument which contains an LVDT bent into a half circle, to
return an angle.
It is excited with 500Hz, and it is pretty well a square wave. I
didn't design that bit :) And the output is too high, for reasons too
complex to explain. So I need to reduce the output somehow.
On Thu, 01 Feb 2024 15:37:48 +0000, Peter ><occassionally-confused@nospam.co.uk> wrote:
legg <legg@nospam.magma.ca> wrote:
It is unusual to run a square wave into an LVDT. If the source is a >>>>too-big square wave, a simple circuit would shape it into the >>>>appropriate amplitude sine. Two or three parts.
I see no reference to an LVDT application in the Peter's posting.
It is an instrument which contains an LVDT bent into a half circle, to >>return an angle.
It is excited with 500Hz, and it is pretty well a square wave. I
didn't design that bit :) And the output is too high, for reasons too >>complex to explain. So I need to reduce the output somehow.
About LVDTs, I know nada.
RL
Anyhow, he said he wanted to reduce the drive level into an LVDT.
I think he could use a simple LC or RLC to make a nice lower-amplitude
sine from his big square wave.
A toroid would have less stray flux, and again there is a vast choice.
I have a bag of these from many years ago https://www.tme.eu/gb/details/tn16_9.6-3f3/ring-ferrites/ferroxcube/tn16-9-6-6-3-3f3/
which with 83 turns would achieve 8mH.
On 30/01/2024 16:13, Peter wrote:
<snip>
A toroid would have less stray flux, and again there is a vast choice.
I have a bag of these from many years ago
https://www.tme.eu/gb/details/tn16_9.6-3f3/ring-ferrites/ferroxcube/tn16-9-6-6-3-3f3/
which with 83 turns would achieve 8mH.
...but nowhere near enough current. Ferroxcube have (or had) a free >downloadable calculator.
As you have already some cores, you could stack several into a tube
shape. I've done this where the available space made it the only game
in town. Tricky to wind but fun, FSVO 'fun'.
On 01/02/2024 23:17, john larkin wrote:
<snip>
Anyhow, he said he wanted to reduce the drive level into an LVDT.Depends how the demodulation works, it's often synched to the drive
I think he could use a simple LC or RLC to make a nice lower-amplitude
sine from his big square wave.
signal and there may be no phase adjustment.
On Fri, 02 Feb 2024 10:08:46 -0500, legg <legg@nospam.magma.ca> wrote:
On Thu, 01 Feb 2024 15:37:48 +0000, Peter >><occassionally-confused@nospam.co.uk> wrote:
legg <legg@nospam.magma.ca> wrote:
It is unusual to run a square wave into an LVDT. If the source is a >>>>>too-big square wave, a simple circuit would shape it into the >>>>>appropriate amplitude sine. Two or three parts.
I see no reference to an LVDT application in the Peter's posting.
It is an instrument which contains an LVDT bent into a half circle, to >>>return an angle.
It is excited with 500Hz, and it is pretty well a square wave. I
didn't design that bit :) And the output is too high, for reasons too >>>complex to explain. So I need to reduce the output somehow.
About LVDTs, I know nada.
RL
They can be interesting.
https://en.wikipedia.org/wiki/Linear_variable_differential_transformer
but there are many varieties and most are not well documented. I get
them and test them to understand them better. I recently bought some
from ebay, the kind that are used in machine tools, with micro-inch >resolution.
I'm planning another LVDT/synchro measurement/simulation box and maybe >machine tools could be a new market. For some reason the LVDTs and
synchros used in machining run at much higher frequencies than the
aerospace stuff, maybe because the cables are typically shorter.
There are LVDT-based inclinometers too.
I used to know all this many years ago... how to work out the flux
density, and choose a material which doesn't saturate, but I have long >forgotten!
It needs to be good with a 13V peak square wave, 500Hz.
So we have 13V across 8mH for 1ms, which from v = L (di/dt) yields
1.625A. A quick hack in LTspice confirms this, for the first 5 cycles.
I had a lot of trouble generating a square wave from -13V to +13V :)
so I am not sure what the current waveform will look like when you
switch to -13V when the current flowing is still 1.625A; I suspect it
will not ever exceed 1.625A later though. With a 13V peak sinewave (a >predefined function in LTspice) it looked to be just under 1A, but all >positive which is obviously BS.
The bit I have forgotten is how to calculate the flux density in the
core. I would prefer the whole thing to be something the size of an
RM10 core
https://www.farnell.com/datasheets/528671.pdf
In 3C95 material you have 5500nH/T^2.
A toroid would have less stray flux, and again there is a vast choice.
I have a bag of these from many years ago >https://www.tme.eu/gb/details/tn16_9.6-3f3/ring-ferrites/ferroxcube/tn16-9-6-6-3-3f3/
which with 83 turns would achieve 8mH.
What I don't get is how much current this will carry. 83 turns at 1.6A
is 132 AT which sounds an awful lot. I thus suspect I will need a
bigger core, probably iron.
Looking on Ebay for ready made stuff, 10mH, I see e.g. >https://www.ebay.co.uk/itm/115852064002
but I am instinctively damn sure that won't carry the current.
Another option is some toroidal transformer, and ignore the existing
winding and put more turns on it. Ebay is full of vintage transformers
but most are pretty big.
I was going to wind the TN16 with some turns and see what it does. I
have an HP 3314 pulse generator and a power amp which can output 9V
peak.
The 8mH needs to be +/- 0.3mH. It was determined experimentally using
this amazing thing
https://www.ebay.co.uk/itm/224101042113
but that obviously contains massive magnetics - it weighs about 1kg.
I also have an LCR meter.
I'd be grateful for any suggestions.
On Fri, 2 Feb 2024 16:17:45 +0000, Clive Arthur
<clive@nowaytoday.co.uk> wrote:
On 30/01/2024 16:13, Peter wrote:
<snip>
A toroid would have less stray flux, and again there is a vast choice.
I have a bag of these from many years ago
https://www.tme.eu/gb/details/tn16_9.6-3f3/ring-ferrites/ferroxcube/tn16-9-6-6-3-3f3/
which with 83 turns would achieve 8mH.
...but nowhere near enough current. Ferroxcube have (or had) a free
downloadable calculator.
As you have already some cores, you could stack several into a tube
shape. I've done this where the available space made it the only game
in town. Tricky to wind but fun, FSVO 'fun'.
An LVDT is not likely to need a lot of excitation current.
On 02/02/2024 17:08, John Larkin wrote:
On Fri, 2 Feb 2024 16:17:45 +0000, Clive Arthur
<clive@nowaytoday.co.uk> wrote:
On 30/01/2024 16:13, Peter wrote:
<snip>
A toroid would have less stray flux, and again there is a vast choice. >>>> I have a bag of these from many years ago
https://www.tme.eu/gb/details/tn16_9.6-3f3/ring-ferrites/ferroxcube/tn16-9-6-6-3-3f3/
which with 83 turns would achieve 8mH.
...but nowhere near enough current. Ferroxcube have (or had) a free
downloadable calculator.
As you have already some cores, you could stack several into a tube
shape. I've done this where the available space made it the only game
in town. Tricky to wind but fun, FSVO 'fun'.
An LVDT is not likely to need a lot of excitation current.
Probably, but the OP didn't specify the application. LVDTs can be
*very* long - the materials testing machines I worked on often used
short stroke LVDTs for test coupon strain measurement and long stroke -
0.5m - for clamp positioning, but in some applications much longer
devices can be used.
I'm assuming the OP has tried an 8mH inductor, is happy with the result,
and doesn't want any more complication.
On Thu, 01 Feb 2024 15:37:48 +0000, Peter ><occassionally-confused@nospam.co.uk> wrote:
legg <legg@nospam.magma.ca> wrote:
It is unusual to run a square wave into an LVDT. If the source is a >>>>too-big square wave, a simple circuit would shape it into the >>>>appropriate amplitude sine. Two or three parts.
I see no reference to an LVDT application in the Peter's posting.
It is an instrument which contains an LVDT bent into a half circle, to >>return an angle.
It is excited with 500Hz, and it is pretty well a square wave. I
didn't design that bit :) And the output is too high, for reasons too >>complex to explain. So I need to reduce the output somehow.
About LVDTs, I know nada.
On Friday, February 2, 2024 at 9:59:46 PM UTC-8, Jan Panteltje wrot=
e:
On a sunny day (Fri, 02 Feb 2024 10:08:46 -0500) it happened legg
<le...@nospam.magma.ca> wrote in <ga1qrit5bgm4if71l...@4ax.com>:
On Thu, 01 Feb 2024 15:37:48 +0000, Peter
<occassional...@nospam.co.uk> wrote:
legg <le...@nospam.magma.ca> wrote:
It is unusual to run a square wave into an LVDT. If the source is a=
too-big square wave, a simple circuit would shape it into the
appropriate amplitude sine. Two or three parts.
I see no reference to an LVDT application in the Peter's posting.
It is an instrument which contains an LVDT bent into a half circle, to=
return an angle.
It is excited with 500Hz, and it is pretty well a square wave. I
didn't design that bit :) And the output is too high, for reasons too=
Same here,complex to explain. So I need to reduce the output somehow.
About LVDTs, I know nada.
but reducing he output of a square wave is simple by adding some series d= >iodes..
Not so! That's an inductor being driven, the diodes will cause flyback vo= >ltage excursions unless you're
doing them in back-to-back antiparallel pairs.
On a sunny day (Fri, 2 Feb 2024 22:38:31 -0800 (PST)) it happened whit3rd ><whit3rd@gmail.com> wrote in ><be0e988c-ecb5-4ee8-9aae-926dbb2c7878n@googlegroups.com>:
On Friday, February 2, 2024 at 9:59:46 PM UTC-8, Jan Panteltje wrot=
e:
On a sunny day (Fri, 02 Feb 2024 10:08:46 -0500) it happened legg
<le...@nospam.magma.ca> wrote in <ga1qrit5bgm4if71l...@4ax.com>:
On Thu, 01 Feb 2024 15:37:48 +0000, Peter
<occassional...@nospam.co.uk> wrote:
legg <le...@nospam.magma.ca> wrote:
It is unusual to run a square wave into an LVDT. If the source is a=
too-big square wave, a simple circuit would shape it into the
appropriate amplitude sine. Two or three parts.
I see no reference to an LVDT application in the Peter's posting.
It is an instrument which contains an LVDT bent into a half circle, to= >>
return an angle.
It is excited with 500Hz, and it is pretty well a square wave. I
didn't design that bit :) And the output is too high, for reasons too=
Same here,complex to explain. So I need to reduce the output somehow.
About LVDTs, I know nada.
but reducing he output of a square wave is simple by adding some series d= >>iodes..
Not so! That's an inductor being driven, the diodes will cause flyback vo= >>ltage excursions unless you're
doing them in back-to-back antiparallel pairs.
Yes of course 2 anti parallel.
On a sunny day (Sat, 03 Feb 2024 10:45:19 GMT) it happened Jan Panteltje ><alien@comet.invalid> wrote in <upl5fv$19m8g$1@solani.org>:
On a sunny day (Fri, 2 Feb 2024 22:38:31 -0800 (PST)) it happened whit3rd >><whit3rd@gmail.com> wrote in >><be0e988c-ecb5-4ee8-9aae-926dbb2c7878n@googlegroups.com>:
On Friday, February 2, 2024 at 9:59:46 PM UTC-8, Jan Panteltje wrot=
e:
On a sunny day (Fri, 02 Feb 2024 10:08:46 -0500) it happened legg
<le...@nospam.magma.ca> wrote in <ga1qrit5bgm4if71l...@4ax.com>:
On Thu, 01 Feb 2024 15:37:48 +0000, PeterSame here,
<occassional...@nospam.co.uk> wrote:
legg <le...@nospam.magma.ca> wrote:
It is unusual to run a square wave into an LVDT. If the source is a= >>>
too-big square wave, a simple circuit would shape it into the
appropriate amplitude sine. Two or three parts.
I see no reference to an LVDT application in the Peter's posting.
It is an instrument which contains an LVDT bent into a half circle, to= >>>
return an angle.
It is excited with 500Hz, and it is pretty well a square wave. I
didn't design that bit :) And the output is too high, for reasons too= >>>
complex to explain. So I need to reduce the output somehow.
About LVDTs, I know nada.
but reducing he output of a square wave is simple by adding some series d= >>>iodes..
Not so! That's an inductor being driven, the diodes will cause flyback vo= >>>ltage excursions unless you're
doing them in back-to-back antiparallel pairs.
Yes of course 2 anti parallel.
But only if on the primary driving the inductor.
The output square wave can just be dropped by diodes
or even a resistor divider
You could even use a bridge recifier and use the DC level in a capacitor.
Or does that setop look for phase?
Then you can still use the zero crossings!
One transistor input into base via resistor,
s diode to protect against reverse Vbe..
We need to know more about the setup.
On a sunny day (Sat, 03 Feb 2024 11:02:39 GMT) it happened Jan Panteltje <alien@comet.invalid> wrote in <upl6gg$1akff$1@solani.org>:
On a sunny day (Sat, 03 Feb 2024 10:45:19 GMT) it happened Jan Panteltje
<alien@comet.invalid> wrote in <upl5fv$19m8g$1@solani.org>:
On a sunny day (Fri, 2 Feb 2024 22:38:31 -0800 (PST)) it happened whit3rd >>> <whit3rd@gmail.com> wrote in
<be0e988c-ecb5-4ee8-9aae-926dbb2c7878n@googlegroups.com>:
On Friday, February 2, 2024 at 9:59:46 PM UTC-8, Jan Panteltje wrot= >>>> e:
On a sunny day (Fri, 02 Feb 2024 10:08:46 -0500) it happened legg
<le...@nospam.magma.ca> wrote in <ga1qrit5bgm4if71l...@4ax.com>:
On Thu, 01 Feb 2024 15:37:48 +0000, Peter <occassional...@nospam.co.uk> wrote:
legg <le...@nospam.magma.ca> wrote:
you could use a simple bridge rectifier in series with the drive coil
short the + and - output and use the AC input terminals.
One or more bridges in series like that too.
On a sunny day (Sat, 03 Feb 2024 10:45:19 GMT) it happened Jan Panteltje ><alien@comet.invalid> wrote in <upl5fv$19m8g$1@solani.org>:
On a sunny day (Fri, 2 Feb 2024 22:38:31 -0800 (PST)) it happened whit3rd >><whit3rd@gmail.com> wrote in >><be0e988c-ecb5-4ee8-9aae-926dbb2c7878n@googlegroups.com>:
On Friday, February 2, 2024 at 9:59:46 PM UTC-8, Jan Panteltje wrot=
e:
On a sunny day (Fri, 02 Feb 2024 10:08:46 -0500) it happened legg
<le...@nospam.magma.ca> wrote in <ga1qrit5bgm4if71l...@4ax.com>:
On Thu, 01 Feb 2024 15:37:48 +0000, PeterSame here,
<occassional...@nospam.co.uk> wrote:
legg <le...@nospam.magma.ca> wrote:
It is unusual to run a square wave into an LVDT. If the source is a= >>>
too-big square wave, a simple circuit would shape it into the
appropriate amplitude sine. Two or three parts.
I see no reference to an LVDT application in the Peter's posting.
It is an instrument which contains an LVDT bent into a half circle, to= >>>
return an angle.
It is excited with 500Hz, and it is pretty well a square wave. I
didn't design that bit :) And the output is too high, for reasons too= >>>
complex to explain. So I need to reduce the output somehow.
About LVDTs, I know nada.
but reducing he output of a square wave is simple by adding some series d= >>>iodes..
Not so! That's an inductor being driven, the diodes will cause flyback vo= >>>ltage excursions unless you're
doing them in back-to-back antiparallel pairs.
Yes of course 2 anti parallel.
But only if on the primary driving the inductor.
The output square wave can just be dropped by diodes
or even a resistor divider
You could even use a bridge recifier and use the DC level in a capacitor.
Or does that setop look for phase?
Then you can still use the zero crossings!
One transistor input into base via resistor,
s diode to protect against reverse Vbe..
We need to know more about the setup.
On Saturday, February 3, 2024 at 10:28:58?PM UTC-8, Bill Sloman wrote:
It's not a good idea to excite an LVDT with a square wave.
The OP should set up a circuit to provide a stable sine wave of the
right amplitude, rather than waste time trying to cut down the amplitude
of the square wave with temperature dependent voltage drops through diodes.
Just to elaborate: an ideal drive for an LVDT would include a transformer coupling
with a grounded center-tap. You want inductive coupling, any capacitive effect
is distortion, so low voltage/high current is best, and the high harmonics
of a square wave put more current through a capacitor than the fundamental.
In the old days, an IF strip (three inductor/capacitor cans) was a good
and convenient sort of square-to-sine filter. Those aren't easy to
buy this week. If 450 kHz works, there's some ceramic filters
still on the market.
On Sat, 03 Feb 2024 11:02:39 GMT, Jan Panteltje <alien@comet.invalid>
wrote:
On a sunny day (Sat, 03 Feb 2024 10:45:19 GMT) it happened Jan Panteltje >><alien@comet.invalid> wrote in <upl5fv$19m8g$1@solani.org>:
On a sunny day (Fri, 2 Feb 2024 22:38:31 -0800 (PST)) it happened whit3rd >>><whit3rd@gmail.com> wrote in >>><be0e988c-ecb5-4ee8-9aae-926dbb2c7878n@googlegroups.com>:
On Friday, February 2, 2024 at 9:59:46 PM UTC-8, Jan Panteltje wrot= >>>>e:
On a sunny day (Fri, 02 Feb 2024 10:08:46 -0500) it happened leggiodes..
<le...@nospam.magma.ca> wrote in <ga1qrit5bgm4if71l...@4ax.com>:
On Thu, 01 Feb 2024 15:37:48 +0000, PeterSame here,
<occassional...@nospam.co.uk> wrote:
legg <le...@nospam.magma.ca> wrote:
It is an instrument which contains an LVDT bent into a half circle, to= >>>>It is unusual to run a square wave into an LVDT. If the source is a= >>>>
too-big square wave, a simple circuit would shape it into the
appropriate amplitude sine. Two or three parts.
I see no reference to an LVDT application in the Peter's posting. >>>>> >>
return an angle.
It is excited with 500Hz, and it is pretty well a square wave. I
didn't design that bit :) And the output is too high, for reasons too= >>>>
complex to explain. So I need to reduce the output somehow.
About LVDTs, I know nada.
but reducing he output of a square wave is simple by adding some series d=
Not so! That's an inductor being driven, the diodes will cause flyback vo=
ltage excursions unless you're
doing them in back-to-back antiparallel pairs.
Yes of course 2 anti parallel.
But only if on the primary driving the inductor.
The output square wave can just be dropped by diodes
or even a resistor divider
You could even use a bridge recifier and use the DC level in a capacitor. >>Or does that setop look for phase?
Then you can still use the zero crossings!
One transistor input into base via resistor,
s diode to protect against reverse Vbe..
We need to know more about the setup.
LVDTs usually use sine wave excitation and a phase-sensitive detector
to convert the signal output into a signed position. The output of an
LVDT is typically zero at the center position. We do most of that
digitally.
There are various LVDT types, too.
One of my manuals has some examples:
http://www.highlandtechnology.com/DSS/P545DS.shtml
On a sunny day (Sun, 04 Feb 2024 08:26:46 -0800) it happened John Larkin ><jl@997PotHill.com> wrote in <f7evri511ku1p9f312ln3v6dg9cipmfebs@4ax.com>:
On Sat, 03 Feb 2024 11:02:39 GMT, Jan Panteltje <alien@comet.invalid> >>wrote:
On a sunny day (Sat, 03 Feb 2024 10:45:19 GMT) it happened Jan Panteltje >>><alien@comet.invalid> wrote in <upl5fv$19m8g$1@solani.org>:
On a sunny day (Fri, 2 Feb 2024 22:38:31 -0800 (PST)) it happened whit3rd >>>><whit3rd@gmail.com> wrote in >>>><be0e988c-ecb5-4ee8-9aae-926dbb2c7878n@googlegroups.com>:
On Friday, February 2, 2024 at 9:59:46 PM UTC-8, Jan Panteltje wrot= >>>>>e:
On a sunny day (Fri, 02 Feb 2024 10:08:46 -0500) it happened leggiodes..
<le...@nospam.magma.ca> wrote in <ga1qrit5bgm4if71l...@4ax.com>:
On Thu, 01 Feb 2024 15:37:48 +0000, Peter
<occassional...@nospam.co.uk> wrote:
legg <le...@nospam.magma.ca> wrote:
It is an instrument which contains an LVDT bent into a half circle, to=It is unusual to run a square wave into an LVDT. If the source is a= >>>>>
too-big square wave, a simple circuit would shape it into the
appropriate amplitude sine. Two or three parts.
I see no reference to an LVDT application in the Peter's posting. >>>>>> >>
Same here,return an angle.
It is excited with 500Hz, and it is pretty well a square wave. I >>>>>> >>didn't design that bit :) And the output is too high, for reasons too= >>>>>
complex to explain. So I need to reduce the output somehow.
About LVDTs, I know nada.
but reducing he output of a square wave is simple by adding some series d=
Not so! That's an inductor being driven, the diodes will cause flyback vo=
ltage excursions unless you're
doing them in back-to-back antiparallel pairs.
Yes of course 2 anti parallel.
But only if on the primary driving the inductor.
The output square wave can just be dropped by diodes
or even a resistor divider
You could even use a bridge recifier and use the DC level in a capacitor. >>>Or does that setop look for phase?
Then you can still use the zero crossings!
One transistor input into base via resistor,
s diode to protect against reverse Vbe..
We need to know more about the setup.
LVDTs usually use sine wave excitation and a phase-sensitive detector
to convert the signal output into a signed position. The output of an
LVDT is typically zero at the center position. We do most of that >>digitally.
There are various LVDT types, too.
One of my manuals has some examples:
http://www.highlandtechnology.com/DSS/P545DS.shtml
Thank you, manual wants a login with pasword though.
On Mon, 05 Feb 2024 05:21:19 GMT, Jan Panteltje <alien@comet.invalid>
wrote:
On a sunny day (Sun, 04 Feb 2024 08:26:46 -0800) it happened John Larkin >><jl@997PotHill.com> wrote in <f7evri511ku1p9f312ln3v6dg9cipmfebs@4ax.com>:
On Sat, 03 Feb 2024 11:02:39 GMT, Jan Panteltje <alien@comet.invalid> >>>wrote:
On a sunny day (Sat, 03 Feb 2024 10:45:19 GMT) it happened Jan Panteltje >>>><alien@comet.invalid> wrote in <upl5fv$19m8g$1@solani.org>:
On a sunny day (Fri, 2 Feb 2024 22:38:31 -0800 (PST)) it happened whit3rd >>>>><whit3rd@gmail.com> wrote in >>>>><be0e988c-ecb5-4ee8-9aae-926dbb2c7878n@googlegroups.com>:
On Friday, February 2, 2024 at 9:59:46 PM UTC-8, Jan Panteltje wrot= >>>>>>e:
On a sunny day (Fri, 02 Feb 2024 10:08:46 -0500) it happened legg >>>>>>> <le...@nospam.magma.ca> wrote in <ga1qrit5bgm4if71l...@4ax.com>: >>>>>>> >On Thu, 01 Feb 2024 15:37:48 +0000, Peteriodes..
<occassional...@nospam.co.uk> wrote:
legg <le...@nospam.magma.ca> wrote:
It is unusual to run a square wave into an LVDT. If the source is a=
It is an instrument which contains an LVDT bent into a half circle, to=too-big square wave, a simple circuit would shape it into the >>>>>>> >>>>appropriate amplitude sine. Two or three parts.
I see no reference to an LVDT application in the Peter's posting. >>>>>>> >>
return an angle.
It is excited with 500Hz, and it is pretty well a square wave. I >>>>>>> >>didn't design that bit :) And the output is too high, for reasons too=
Same here,complex to explain. So I need to reduce the output somehow.
About LVDTs, I know nada.
but reducing he output of a square wave is simple by adding some series d=
Not so! That's an inductor being driven, the diodes will cause flyback vo=
ltage excursions unless you're
doing them in back-to-back antiparallel pairs.
Yes of course 2 anti parallel.
But only if on the primary driving the inductor.
The output square wave can just be dropped by diodes
or even a resistor divider
You could even use a bridge recifier and use the DC level in a capacitor. >>>>Or does that setop look for phase?
Then you can still use the zero crossings!
One transistor input into base via resistor,
s diode to protect against reverse Vbe..
We need to know more about the setup.
LVDTs usually use sine wave excitation and a phase-sensitive detector
to convert the signal output into a signed position. The output of an >>>LVDT is typically zero at the center position. We do most of that >>>digitally.
There are various LVDT types, too.
One of my manuals has some examples:
http://www.highlandtechnology.com/DSS/P545DS.shtml
Thank you, manual wants a login with pasword though.
They want you to register. You might get a newsletter about once a
year.
On a sunny day (Mon, 05 Feb 2024 07:08:16 -0800) it happened John Larkin ><jl@997PotHill.com> wrote in <vbu1sihfc7dtubu0v0mjs8hgb67t8g0k36@4ax.com>:
On Mon, 05 Feb 2024 05:21:19 GMT, Jan Panteltje <alien@comet.invalid> >>wrote:
On a sunny day (Sun, 04 Feb 2024 08:26:46 -0800) it happened John Larkin >>><jl@997PotHill.com> wrote in <f7evri511ku1p9f312ln3v6dg9cipmfebs@4ax.com>: >>>
On Sat, 03 Feb 2024 11:02:39 GMT, Jan Panteltje <alien@comet.invalid> >>>>wrote:
On a sunny day (Sat, 03 Feb 2024 10:45:19 GMT) it happened Jan Panteltje >>>>><alien@comet.invalid> wrote in <upl5fv$19m8g$1@solani.org>:
On a sunny day (Fri, 2 Feb 2024 22:38:31 -0800 (PST)) it happened whit3rd >>>>>><whit3rd@gmail.com> wrote in >>>>>><be0e988c-ecb5-4ee8-9aae-926dbb2c7878n@googlegroups.com>:
On Friday, February 2, 2024 at 9:59:46 PM UTC-8, Jan Panteltje wrot= >>>>>>>e:
On a sunny day (Fri, 02 Feb 2024 10:08:46 -0500) it happened legg >>>>>>>> <le...@nospam.magma.ca> wrote in <ga1qrit5bgm4if71l...@4ax.com>: >>>>>>>> >On Thu, 01 Feb 2024 15:37:48 +0000, Peteriodes..
<occassional...@nospam.co.uk> wrote:
legg <le...@nospam.magma.ca> wrote:
It is unusual to run a square wave into an LVDT. If the source is a=
It is an instrument which contains an LVDT bent into a half circle, to=too-big square wave, a simple circuit would shape it into the >>>>>>>> >>>>appropriate amplitude sine. Two or three parts.
I see no reference to an LVDT application in the Peter's posting. >>>>>>>> >>
return an angle.
It is excited with 500Hz, and it is pretty well a square wave. I >>>>>>>> >>didn't design that bit :) And the output is too high, for reasons too=
Same here,complex to explain. So I need to reduce the output somehow.
About LVDTs, I know nada.
but reducing he output of a square wave is simple by adding some series d=
Not so! That's an inductor being driven, the diodes will cause flyback vo=
ltage excursions unless you're
doing them in back-to-back antiparallel pairs.
Yes of course 2 anti parallel.
But only if on the primary driving the inductor.
The output square wave can just be dropped by diodes
or even a resistor divider
You could even use a bridge recifier and use the DC level in a capacitor. >>>>>Or does that setop look for phase?
Then you can still use the zero crossings!
One transistor input into base via resistor,
s diode to protect against reverse Vbe..
We need to know more about the setup.
LVDTs usually use sine wave excitation and a phase-sensitive detector >>>>to convert the signal output into a signed position. The output of an >>>>LVDT is typically zero at the center position. We do most of that >>>>digitally.
There are various LVDT types, too.
One of my manuals has some examples:
http://www.highlandtechnology.com/DSS/P545DS.shtml
Thank you, manual wants a login with pasword though.
They want you to register. You might get a newsletter about once a
year.
Yea, I was thinking adding genocide@whitehouse.gov as email with password biden
but do not want to spam anybody.
On Tue, 06 Feb 2024 05:04:35 GMT, Jan Panteltje <alien@comet.invalid>
wrote:
On a sunny day (Mon, 05 Feb 2024 07:08:16 -0800) it happened John Larkin >><jl@997PotHill.com> wrote in <vbu1sihfc7dtubu0v0mjs8hgb67t8g0k36@4ax.com>:
On Mon, 05 Feb 2024 05:21:19 GMT, Jan Panteltje <alien@comet.invalid> >>>wrote:
On a sunny day (Sun, 04 Feb 2024 08:26:46 -0800) it happened John Larkin >>>><jl@997PotHill.com> wrote in <f7evri511ku1p9f312ln3v6dg9cipmfebs@4ax.com>: >>>>
On Sat, 03 Feb 2024 11:02:39 GMT, Jan Panteltje <alien@comet.invalid> >>>>>wrote:
On a sunny day (Sat, 03 Feb 2024 10:45:19 GMT) it happened Jan Panteltje >>>>>><alien@comet.invalid> wrote in <upl5fv$19m8g$1@solani.org>:
On a sunny day (Fri, 2 Feb 2024 22:38:31 -0800 (PST)) it happened whit3rd
<whit3rd@gmail.com> wrote in >>>>>>><be0e988c-ecb5-4ee8-9aae-926dbb2c7878n@googlegroups.com>:
On Friday, February 2, 2024 at 9:59:46 PM UTC-8, Jan Panteltje wrot= >>>>>>>>e:
On a sunny day (Fri, 02 Feb 2024 10:08:46 -0500) it happened legg >>>>>>>>> <le...@nospam.magma.ca> wrote in <ga1qrit5bgm4if71l...@4ax.com>: >>>>>>>>> >On Thu, 01 Feb 2024 15:37:48 +0000, Peteriodes..
<occassional...@nospam.co.uk> wrote:
legg <le...@nospam.magma.ca> wrote:
It is unusual to run a square wave into an LVDT. If the source is a=
It is an instrument which contains an LVDT bent into a half circle, to=too-big square wave, a simple circuit would shape it into the >>>>>>>>> >>>>appropriate amplitude sine. Two or three parts.
I see no reference to an LVDT application in the Peter's posting. >>>>>>>>> >>
return an angle.
It is excited with 500Hz, and it is pretty well a square wave. I >>>>>>>>> >>didn't design that bit :) And the output is too high, for reasons too=
Same here,complex to explain. So I need to reduce the output somehow. >>>>>>>>> >About LVDTs, I know nada.
but reducing he output of a square wave is simple by adding some series d=
Not so! That's an inductor being driven, the diodes will cause flyback vo=
ltage excursions unless you're
doing them in back-to-back antiparallel pairs.
Yes of course 2 anti parallel.
But only if on the primary driving the inductor.
The output square wave can just be dropped by diodes
or even a resistor divider
You could even use a bridge recifier and use the DC level in a capacitor. >>>>>>Or does that setop look for phase?
Then you can still use the zero crossings!
One transistor input into base via resistor,
s diode to protect against reverse Vbe..
We need to know more about the setup.
LVDTs usually use sine wave excitation and a phase-sensitive detector >>>>>to convert the signal output into a signed position. The output of an >>>>>LVDT is typically zero at the center position. We do most of that >>>>>digitally.
There are various LVDT types, too.
One of my manuals has some examples:
http://www.highlandtechnology.com/DSS/P545DS.shtml
Thank you, manual wants a login with pasword though.
They want you to register. You might get a newsletter about once a
year.
Yea, I was thinking adding genocide@whitehouse.gov as email with password biden
but do not want to spam anybody.
The next tme that Russia or France or Germany wants to invade your
tiny damp country, we'll sit it out.
I'm assuming the OP has tried an 8mH inductor, is happy with the result, >>and doesn't want any more complication.
Somehow I doubt that. He calculated 1.6 amps of LVDT excitation
current.
John Larkin <jl@997PotHill.com> wrote:
I'm assuming the OP has tried an 8mH inductor, is happy with the result, >>>and doesn't want any more complication.
Somehow I doubt that. He calculated 1.6 amps of LVDT excitation
current.
That is exactly what I did.
I bought a 0-10mH (in 1mH steps) variable inductor off Ebay and found
8mH does the perfect job. General Radio 940 >https://www.ebay.co.uk/itm/224101042113
Got this from Mouser and will test it >https://www.mouser.co.uk/datasheet/2/54/5700_series-777305.pdf
The 1.6 amps is real, give or take a bit. Yesit surprises me it is
that much. But I can't change the drive circuit. It's simply crap.
Honeywell, BTW ;) Well, actually, from the last days of Bendix King,
around 24 years ago.
On Tue, 13 Feb 2024 13:47:06 +0000, Peter <occassionally-confused@nospam.co.uk> wrote:
John Larkin <jl@997PotHill.com> wrote:
I'm assuming the OP has tried an 8mH inductor, is happy with the result, >>>> and doesn't want any more complication.
Somehow I doubt that. He calculated 1.6 amps of LVDT excitation
current.
That is exactly what I did.
I bought a 0-10mH (in 1mH steps) variable inductor off Ebay and found
8mH does the perfect job. General Radio 940
https://www.ebay.co.uk/itm/224101042113
Got this from Mouser and will test it
https://www.mouser.co.uk/datasheet/2/54/5700_series-777305.pdf
The 1.6 amps is real, give or take a bit. Yesit surprises me it is
that much. But I can't change the drive circuit. It's simply crap.
Honeywell, BTW ;) Well, actually, from the last days of Bendix King,
around 24 years ago.
1.6 amps of square wave into an LVDT is shocking. Maybe the same
person designed the LVDT and the driver.
What does it do? I mean, what mechanical thing does it measure?
Always a good question. The answer is probably to get some ancient lump pf rubbish working with the minimum investment of effort.
It's rarely a wise approach, but people under pressure can't afford wisdom.
legg <legg@nospam.magma.ca> wrote:
It is unusual to run a square wave into an LVDT. If the source is a >>>too-big square wave, a simple circuit would shape it into the
appropriate amplitude sine. Two or three parts.
I see no reference to an LVDT application in the Peter's posting.
It is an instrument which contains an LVDT bent into a half circle, to
return an angle.
It is excited with 500Hz, and it is pretty well a square wave. I
didn't design that bit :) And the output is too high, for reasons too
complex to explain. So I need to reduce the output somehow.
Just an update.
I tested that 8mH coil from Mouser. Verified at 8mH with an LCR meter
and with the $500 micro tweezer thingy.
Doesn't work!! It behaves like it was 20mH or something like that. The attenuation is way too high. But 8mH was the perfect value with that
funny milspec 0-10mH box I got off Ebay, which was heavy enough to
contain pretty big inductors.
So what is happening?
Must be something in the waveform which is buggering up the way these inductors behave, in conjunction with the demodulation scheme used to "decode" the LVDT position.
Maybe it is saturating, but saturation has the opposite effect: it
*lowers* the effective inductance.
So I bought a 2.5mH one from Mouser, again one which can do 1.5A or
so, and will try that, after the potting compound has gone off :)
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