• cheap ADC

    From jlarkin@highlandsniptechnology.com@21:1/5 to All on Thu Jan 20 08:31:07 2022
    This uses an FPGA LVDS input as a comparator, and one external RC, to
    make an ADC. Just need an algorithm to process the flop output.

    A simpler ADC should be possible.


    Version 4
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    TEXT 558 200 Left 2 !.tran 10m
    TEXT 512 80 Left 2 ;Cheap FPGA ADC
    TEXT 528 128 Left 2 ;JL Jan 17 2022




    --

    I yam what I yam - Popeye

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Lasse Langwadt Christensen@21:1/5 to All on Thu Jan 20 11:51:16 2022
    torsdag den 20. januar 2022 kl. 17.31.18 UTC+1 skrev jla...@highlandsniptechnology.com:
    This uses an FPGA LVDS input as a comparator, and one external RC, to
    make an ADC. Just need an algorithm to process the flop output.

    A simpler ADC should be possible.


    more than one way to do it, one is basically successive approximation with a pwm dac
    another is delta-sigma with RC as "integrator" that might have an advantage in that the
    comparator doesn't follow the input signal it is always ~1/2 Vcc


    Version 4
    SHEET 1 1316 680
    WIRE -96 -992 -176 -992
    WIRE -176 -960 -176 -992
    WIRE 496 -832 -320 -832
    WIRE -96 -752 -96 -992
    WIRE -96 -752 -128 -752
    WIRE -128 -720 -128 -752
    WIRE -96 -720 -96 -752
    WIRE -320 -688 -320 -752
    WIRE -304 -688 -320 -688
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    SYMATTR Value PULSE(0 3 0 0 0 50n 100n)
    TEXT -712 488 Left 2 !.tran 5m
    RECTANGLE Normal 576 480 144 -128 2
    RECTANGLE Normal 576 -288 144 -896 2

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From jlarkin@highlandsniptechnology.com@21:1/5 to langwadt@fonz.dk on Thu Jan 20 18:07:56 2022
    On Thu, 20 Jan 2022 11:51:16 -0800 (PST), Lasse Langwadt Christensen <langwadt@fonz.dk> wrote:

    torsdag den 20. januar 2022 kl. 17.31.18 UTC+1 skrev jla...@highlandsniptechnology.com:
    This uses an FPGA LVDS input as a comparator, and one external RC, to
    make an ADC. Just need an algorithm to process the flop output.

    A simpler ADC should be possible.


    more than one way to do it, one is basically successive approximation with a pwm dac
    another is delta-sigma with RC as "integrator" that might have an advantage in that the
    comparator doesn't follow the input signal it is always ~1/2 Vcc

    That's certainly better; the FPGA LVDS receivers are mediocre
    comparators. But the game was to minimize the number of external
    parts. I'll be digitizing a thermistor on a heat sink, so it's not a
    precision thing.

    If we go with an available Lattice FPGA, it doesn't have an ADC.

    Some sort of delta-sigma signal processing would be interesting.

    I could use an LM71, SPI temp sensor, which is just not as
    interesting.






    Version 4
    SHEET 1 1316 680
    WIRE -96 -992 -176 -992
    WIRE -176 -960 -176 -992
    WIRE 496 -832 -320 -832
    WIRE -96 -752 -96 -992
    WIRE -96 -752 -128 -752
    WIRE -128 -720 -128 -752
    WIRE -96 -720 -96 -752
    WIRE -320 -688 -320 -752
    WIRE -304 -688 -320 -688
    WIRE -144 -688 -304 -688
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    SYMBOL cap 896 -576 R0
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    WINDOW 123 0 0 Left 2
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    WINDOW 123 0 0 Left 2
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    SYMATTR Value PULSE(0 3 0 0 0 50n 100n)
    TEXT -712 488 Left 2 !.tran 5m
    RECTANGLE Normal 576 480 144 -128 2
    RECTANGLE Normal 576 -288 144 -896 2


    --

    I yam what I yam - Popeye

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Rick C@21:1/5 to lang...@fonz.dk on Thu Jan 20 21:05:30 2022
    On Thursday, January 20, 2022 at 2:51:20 PM UTC-5, lang...@fonz.dk wrote:
    torsdag den 20. januar 2022 kl. 17.31.18 UTC+1 skrev jla...@highlandsniptechnology.com:
    This uses an FPGA LVDS input as a comparator, and one external RC, to
    make an ADC. Just need an algorithm to process the flop output.

    A simpler ADC should be possible.

    more than one way to do it, one is basically successive approximation with a pwm dac
    another is delta-sigma with RC as "integrator" that might have an advantage in that the
    comparator doesn't follow the input signal it is always ~1/2 Vcc

    That is important in an FPGA because the differential inputs are not rail to rail. In fact, they are rated to work over a very limited range. I'm not sure how well they will serve in this application. A good comparator is rated for offset voltage.
    The spec on an LVDS mode input in an FPGA has a very loose spec for that. Given that the input circuit is basically a voltage divider it works to increase the significance of input offset relative to the input signal.

    If you are trying to set an alarm for some condition with a loose input spec for accuracy or offset, then this can work fine. It only costs 3 pins on the FPGA. I worked on a design that used 8 such ADCs. Rather than use resistors to set the reference
    point I used another output with a 50/50 duty cycle to get an accurate Vcc/2 point that follows the rail without resistors removing some source of error and could be shared with all the ADCs. It also allowed you to adjust the reference voltage if there
    became a need to make an adjustment.

    --

    Rick C.

    - Get 1,000 miles of free Supercharging
    - Tesla referral code - https://ts.la/richard11209

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  • From Jan Panteltje@21:1/5 to All on Fri Jan 21 10:44:29 2022
    <fd3jugh4hv2mlbl9dfchcql4cf93udatav@4ax.com> a ecrit

    This uses an FPGA LVDS input as a comparator, and one external RC, to
    make an ADC. Just need an algorithm to process the flop output.

    A simpler ADC should be possible.
    WINDOW 0 46 12 Left 2
    I yam what I yam - Popeye

    Probiblie bEst iz too juice a FLIR IR camarade wiz Anna Log outpud
    ant prozes ze vidio on 1 FPGAYE pin.
    Ze moost rat airraids r ze hot test

    Tom

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  • From Lasse Langwadt Christensen@21:1/5 to All on Fri Jan 21 03:41:56 2022
    fredag den 21. januar 2022 kl. 03.08.06 UTC+1 skrev jla...@highlandsniptechnology.com:
    On Thu, 20 Jan 2022 11:51:16 -0800 (PST), Lasse Langwadt Christensen <lang...@fonz.dk> wrote:

    torsdag den 20. januar 2022 kl. 17.31.18 UTC+1 skrev jla...@highlandsniptechnology.com:
    This uses an FPGA LVDS input as a comparator, and one external RC, to
    make an ADC. Just need an algorithm to process the flop output.

    A simpler ADC should be possible.


    more than one way to do it, one is basically successive approximation with a pwm dac
    another is delta-sigma with RC as "integrator" that might have an advantage in that the
    comparator doesn't follow the input signal it is always ~1/2 Vcc
    That's certainly better; the FPGA LVDS receivers are mediocre
    comparators. But the game was to minimize the number of external
    parts. I'll be digitizing a thermistor on a heat sink, so it's not a precision thing.

    If we go with an available Lattice FPGA, it doesn't have an ADC.

    Some sort of delta-sigma signal processing would be interesting.

    I could use an LM71, SPI temp sensor, which is just not as
    interesting.

    even simpler tmp05/tmp06 which is pwm output so all you need is a counter in the fpga

    or for easy mounting on a heat sink, https://dk.farnell.com/smartec/smt172-220/temperature-sensor-1deg-c-to-220/dp/2543396

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Klaus Vestergaard Kragelund@21:1/5 to Lasse Langwadt Christensen on Fri Jan 21 15:49:03 2022
    On 21/01/2022 12.41, Lasse Langwadt Christensen wrote:
    fredag den 21. januar 2022 kl. 03.08.06 UTC+1 skrev jla...@highlandsniptechnology.com:
    On Thu, 20 Jan 2022 11:51:16 -0800 (PST), Lasse Langwadt Christensen
    <lang...@fonz.dk> wrote:

    torsdag den 20. januar 2022 kl. 17.31.18 UTC+1 skrev jla...@highlandsniptechnology.com:
    This uses an FPGA LVDS input as a comparator, and one external RC, to
    make an ADC. Just need an algorithm to process the flop output.

    A simpler ADC should be possible.


    more than one way to do it, one is basically successive approximation with a pwm dac
    another is delta-sigma with RC as "integrator" that might have an advantage in that the
    comparator doesn't follow the input signal it is always ~1/2 Vcc
    That's certainly better; the FPGA LVDS receivers are mediocre
    comparators. But the game was to minimize the number of external
    parts. I'll be digitizing a thermistor on a heat sink, so it's not a
    precision thing.

    If we go with an available Lattice FPGA, it doesn't have an ADC.

    Some sort of delta-sigma signal processing would be interesting.

    I could use an LM71, SPI temp sensor, which is just not as
    interesting.

    even simpler tmp05/tmp06 which is pwm output so all you need is a counter in the fpga

    or for easy mounting on a heat sink, https://dk.farnell.com/smartec/smt172-220/temperature-sensor-1deg-c-to-220/dp/2543396

    Who in their right mind comes up with a device name "tmp05"? ;-)

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From jlarkin@highlandsniptechnology.com@21:1/5 to langwadt@fonz.dk on Fri Jan 21 07:09:53 2022
    On Fri, 21 Jan 2022 03:41:56 -0800 (PST), Lasse Langwadt Christensen <langwadt@fonz.dk> wrote:

    fredag den 21. januar 2022 kl. 03.08.06 UTC+1 skrev jla...@highlandsniptechnology.com:
    On Thu, 20 Jan 2022 11:51:16 -0800 (PST), Lasse Langwadt Christensen
    <lang...@fonz.dk> wrote:

    torsdag den 20. januar 2022 kl. 17.31.18 UTC+1 skrev jla...@highlandsniptechnology.com:
    This uses an FPGA LVDS input as a comparator, and one external RC, to
    make an ADC. Just need an algorithm to process the flop output.

    A simpler ADC should be possible.


    more than one way to do it, one is basically successive approximation with a pwm dac
    another is delta-sigma with RC as "integrator" that might have an advantage in that the
    comparator doesn't follow the input signal it is always ~1/2 Vcc
    That's certainly better; the FPGA LVDS receivers are mediocre
    comparators. But the game was to minimize the number of external
    parts. I'll be digitizing a thermistor on a heat sink, so it's not a
    precision thing.

    If we go with an available Lattice FPGA, it doesn't have an ADC.

    Some sort of delta-sigma signal processing would be interesting.

    I could use an LM71, SPI temp sensor, which is just not as
    interesting.

    even simpler tmp05/tmp06 which is pwm output so all you need is a counter in the fpga

    or for easy mounting on a heat sink, https://dk.farnell.com/smartec/smt172-220/temperature-sensor-1deg-c-to-220/dp/2543396

    74 cookies! A record!

    That would be a good way to couple thermally to the heat sink. We have
    LM35 in stock, in TO220, too, but that would require an ADC and
    probebly an opamp, which isn't bad.

    I want to simulate the mosfet junction temperatures in realtime, and
    the heatsink temp is part of that math.



    --

    I yam what I yam - Popeye

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Rick C@21:1/5 to lang...@fonz.dk on Fri Jan 21 19:28:54 2022
    On Friday, January 21, 2022 at 6:42:00 AM UTC-5, lang...@fonz.dk wrote:
    fredag den 21. januar 2022 kl. 03.08.06 UTC+1 skrev jla...@highlandsniptechnology.com:
    On Thu, 20 Jan 2022 11:51:16 -0800 (PST), Lasse Langwadt Christensen <lang...@fonz.dk> wrote:

    torsdag den 20. januar 2022 kl. 17.31.18 UTC+1 skrev jla...@highlandsniptechnology.com:
    This uses an FPGA LVDS input as a comparator, and one external RC, to >> make an ADC. Just need an algorithm to process the flop output.

    A simpler ADC should be possible.


    more than one way to do it, one is basically successive approximation with a pwm dac
    another is delta-sigma with RC as "integrator" that might have an advantage in that the
    comparator doesn't follow the input signal it is always ~1/2 Vcc
    That's certainly better; the FPGA LVDS receivers are mediocre
    comparators. But the game was to minimize the number of external
    parts. I'll be digitizing a thermistor on a heat sink, so it's not a precision thing.

    If we go with an available Lattice FPGA, it doesn't have an ADC.

    Some sort of delta-sigma signal processing would be interesting.

    I could use an LM71, SPI temp sensor, which is just not as
    interesting.
    even simpler tmp05/tmp06 which is pwm output so all you need is a counter in the fpga

    or for easy mounting on a heat sink, https://dk.farnell.com/smartec/smt172-220/temperature-sensor-1deg-c-to-220/dp/2543396

    Isn't the FPGA the place where you put arbitrarily complex logic? Why try to minimize it? The filter typically used in the ADC you indicated above is often an integrate and dump, otherwise known as a counter. The filter characteristics are such that
    frequency multiples of half the sample rate are on nulls. This helps with the antialias filtering, but to get a sharper response near the half sample rate requires a FIR filter or similar. In fact, best is a filter that compensates with some boost to
    compensate for the integrate and dump roll off. A design example I saw from Lattice included both an integrate and dump followed by a FIR filter. However, I believe the FIR coefficients were all just 1, so after decimation it was also an integrate and
    dump equivalent. I suppose you could add any coefficients you wished. It was only a app note after all.

    Often the application does not require any significant filtering and the integrate and dump is simply the way of increasing the resolution from 1 bit to N bits by counting 2^N input samples.

    --

    Rick C.

    + Get 1,000 miles of free Supercharging
    + Tesla referral code - https://ts.la/richard11209

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  • From Lasse Langwadt Christensen@21:1/5 to All on Sat Jan 22 15:29:28 2022
    lørdag den 22. januar 2022 kl. 04.28.58 UTC+1 skrev gnuarm.del...@gmail.com:
    On Friday, January 21, 2022 at 6:42:00 AM UTC-5, lang...@fonz.dk wrote:
    fredag den 21. januar 2022 kl. 03.08.06 UTC+1 skrev jla...@highlandsniptechnology.com:
    On Thu, 20 Jan 2022 11:51:16 -0800 (PST), Lasse Langwadt Christensen <lang...@fonz.dk> wrote:

    torsdag den 20. januar 2022 kl. 17.31.18 UTC+1 skrev jla...@highlandsniptechnology.com:
    This uses an FPGA LVDS input as a comparator, and one external RC, to >> make an ADC. Just need an algorithm to process the flop output.

    A simpler ADC should be possible.


    more than one way to do it, one is basically successive approximation with a pwm dac
    another is delta-sigma with RC as "integrator" that might have an advantage in that the
    comparator doesn't follow the input signal it is always ~1/2 Vcc
    That's certainly better; the FPGA LVDS receivers are mediocre comparators. But the game was to minimize the number of external
    parts. I'll be digitizing a thermistor on a heat sink, so it's not a precision thing.

    If we go with an available Lattice FPGA, it doesn't have an ADC.

    Some sort of delta-sigma signal processing would be interesting.

    I could use an LM71, SPI temp sensor, which is just not as
    interesting.
    even simpler tmp05/tmp06 which is pwm output so all you need is a counter in the fpga

    or for easy mounting on a heat sink, https://dk.farnell.com/smartec/smt172-220/temperature-sensor-1deg-c-to-220/dp/2543396
    Isn't the FPGA the place where you put arbitrarily complex logic? Why try to minimize it?

    why spend time to implement a SPI, use three/four pins, or logic and extra parts to fudge an ADC and calibrate that
    when you can get a calibrated part that only need a single pin and very simple logic

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Rick C@21:1/5 to lang...@fonz.dk on Sat Jan 22 19:14:32 2022
    On Saturday, January 22, 2022 at 6:29:32 PM UTC-5, lang...@fonz.dk wrote:
    lørdag den 22. januar 2022 kl. 04.28.58 UTC+1 skrev gnuarm.del...@gmail.com:
    On Friday, January 21, 2022 at 6:42:00 AM UTC-5, lang...@fonz.dk wrote:
    fredag den 21. januar 2022 kl. 03.08.06 UTC+1 skrev jla...@highlandsniptechnology.com:
    On Thu, 20 Jan 2022 11:51:16 -0800 (PST), Lasse Langwadt Christensen <lang...@fonz.dk> wrote:

    torsdag den 20. januar 2022 kl. 17.31.18 UTC+1 skrev jla...@highlandsniptechnology.com:
    This uses an FPGA LVDS input as a comparator, and one external RC, to
    make an ADC. Just need an algorithm to process the flop output.

    A simpler ADC should be possible.


    more than one way to do it, one is basically successive approximation with a pwm dac
    another is delta-sigma with RC as "integrator" that might have an advantage in that the
    comparator doesn't follow the input signal it is always ~1/2 Vcc That's certainly better; the FPGA LVDS receivers are mediocre comparators. But the game was to minimize the number of external parts. I'll be digitizing a thermistor on a heat sink, so it's not a precision thing.

    If we go with an available Lattice FPGA, it doesn't have an ADC.

    Some sort of delta-sigma signal processing would be interesting.

    I could use an LM71, SPI temp sensor, which is just not as interesting.
    even simpler tmp05/tmp06 which is pwm output so all you need is a counter in the fpga

    or for easy mounting on a heat sink, https://dk.farnell.com/smartec/smt172-220/temperature-sensor-1deg-c-to-220/dp/2543396
    Isn't the FPGA the place where you put arbitrarily complex logic? Why try to minimize it?
    why spend time to implement a SPI, use three/four pins, or logic and extra parts to fudge an ADC and calibrate that
    when you can get a calibrated part that only need a single pin and very simple logic

    Not sure what you are comparing to what. An ADC inside the FPGA uses no external parts other than perhaps resistors and capacitors. You are talking about a temperature sensor, I was only talking about an ADC. If the cost is paramount, the passives
    are cheaper than the TMP05/06, only a few of them are active, in stock in small quantities at Digikey and cost dollars!!! Am I looking at the wrong parts? I've used an analog temperature sensor that was only $0.10 in quantity, the TMP236! Well, looks
    like they are a bit more now, $0.27. I got a penny happy group of designers to use that instead of a thermistor which was the same price.

    The semiconductor shortage seems to have decimated the inventory of temperature sensors. Digikey will show 15 or more parts, but only 2 in stock and 52 week lead times once those are gone!

    Yeah, resistors and capacitors with a thermistor are looking pretty good.

    --

    Rick C.

    -- Get 1,000 miles of free Supercharging
    -- Tesla referral code - https://ts.la/richard11209

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  • From Jan Panteltje@21:1/5 to gnuarm.deletethisbit@gmail.com on Sun Jan 23 07:15:56 2022
    On a sunny day (Sat, 22 Jan 2022 19:14:32 -0800 (PST)) it happened Rick C <gnuarm.deletethisbit@gmail.com> wrote in <79d8ba05-633a-4166-ab31-140807936482n@googlegroups.com>:

    On Saturday, January 22, 2022 at 6:29:32 PM UTC-5, lang...@fonz.dk wrote:
    l=C3=B8rdag den 22. januar 2022 kl. 04.28.58 UTC+1 skrev gnuarm.del...@gmail.com:

    On Friday, January 21, 2022 at 6:42:00 AM UTC-5, lang...@fonz.dk wrote:

    fredag den 21. januar 2022 kl. 03.08.06 UTC+1 skrev jla...@highlandsniptechnology.com:

    On Thu, 20 Jan 2022 11:51:16 -0800 (PST), Lasse Langwadt Christensen

    <lang...@fonz.dk> wrote:

    torsdag den 20. januar 2022 kl. 17.31.18 UTC+1 skrev jla...@highlandsniptechnology.com:

    This uses an FPGA LVDS input as a comparator, and one external RC, >to
    make an ADC. Just need an algorithm to process the flop output.


    A simpler ADC should be possible.


    more than one way to do it, one is basically successive approximation >with a pwm dac
    another is delta-sigma with RC as "integrator" that might have an advantage
    in that the
    comparator doesn't follow the input signal it is always ~1/2 Vcc

    That's certainly better; the FPGA LVDS receivers are mediocre
    comparators. But the game was to minimize the number of external
    parts. I'll be digitizing a thermistor on a heat sink, so it's not a >>
    precision thing.

    If we go with an available Lattice FPGA, it doesn't have an ADC.

    Some sort of delta-sigma signal processing would be interesting.

    I could use an LM71, SPI temp sensor, which is just not as
    interesting.
    even simpler tmp05/tmp06 which is pwm output so all you need is a counter
    in the fpga

    or for easy mounting on a heat sink,
    https://dk.farnell.com/smartec/smt172-220/temperature-sensor-1deg-c-to-220/dp/2543396

    Isn't the FPGA the place where you put arbitrarily complex logic? Why try >to minimize it?
    why spend time to implement a SPI, use three/four pins, or logic and extra >parts to fudge an ADC and calibrate that
    when you can get a calibrated part that only need a single pin and very simple
    logic

    Not sure what you are comparing to what. An ADC inside the FPGA uses no external
    parts other than perhaps resistors and capacitors. You are talking
    about a temperature sensor, I was only talking about an ADC. If the cost is >paramount, the passives are cheaper than the TMP05/06, only a few of them
    are active, in stock in small quantities at Digikey and cost dollars!!! Am
    I looking at the wrong parts? I've used an analog temperature sensor that >was only $0.10 in quantity, the TMP236! Well, looks like they are a bit
    more now, $0.27. I got a penny happy group of designers to use that instead >of a thermistor which was the same price.

    The semiconductor shortage seems to have decimated the inventory of temperature
    sensors. Digikey will show 15 or more parts, but only 2 in stock and 52
    week lead times once those are gone!

    Yeah, resistors and capacitors with a thermistor are looking pretty good.

    Any diode will function as temperature sensor.
    Been there done that, even used the forward biased cb junction from a TO220 transistor screwed to the heatsink.
    Is sort of linear, and takes only one calibration point, collector at ground potential from heatsink, no isolation needed.
    Any old TO220 will do :-)
    http://panteltje.com/panteltje/tri_pic/tritium_decay_experiment_black_box_circuit_diagram_IMG_3883.GIF
    on pin 9 of the PIC.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Rick C@21:1/5 to Jan Panteltje on Sun Jan 23 04:06:46 2022
    On Sunday, January 23, 2022 at 2:17:19 AM UTC-5, Jan Panteltje wrote:
    On a sunny day (Sat, 22 Jan 2022 19:14:32 -0800 (PST)) it happened Rick C

    Yeah, resistors and capacitors with a thermistor are looking pretty good. Any diode will function as temperature sensor.
    Been there done that, even used the forward biased cb junction from a TO220 transistor screwed to the heatsink.
    Is sort of linear, and takes only one calibration point, collector at ground potential from heatsink, no isolation needed.
    Any old TO220 will do :-) http://panteltje.com/panteltje/tri_pic/tritium_decay_experiment_black_box_circuit_diagram_IMG_3883.GIF
    on pin 9 of the PIC.

    What was the temperature resolution of this setup? When you mention calibration point, do you mean a one time design calibration or a calibration for each device? I know they use diode junctions on chips to measure temperature, but typically they use a
    special circuit to drive with two known currents, eliminating the need for calibration, no?


    --

    Rick C.

    -+ Get 1,000 miles of free Supercharging
    -+ Tesla referral code - https://ts.la/richard11209

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  • From Jan Panteltje@21:1/5 to gnuarm.deletethisbit@gmail.com on Sun Jan 23 13:14:39 2022
    On a sunny day (Sun, 23 Jan 2022 04:06:46 -0800 (PST)) it happened Rick C <gnuarm.deletethisbit@gmail.com> wrote in <bae72651-1e98-43de-b7ee-9ff379eb6470n@googlegroups.com>:

    On Sunday, January 23, 2022 at 2:17:19 AM UTC-5, Jan Panteltje wrote:
    On a sunny day (Sat, 22 Jan 2022 19:14:32 -0800 (PST)) it happened Rick C


    Yeah, resistors and capacitors with a thermistor are looking pretty good. >>
    Any diode will function as temperature sensor.
    Been there done that, even used the forward biased cb junction from a TO220 >transistor screwed to the heatsink.
    Is sort of linear, and takes only one calibration point, collector at ground >potential from heatsink, no isolation needed.
    Any old TO220 will do :-)
    http://panteltje.com/panteltje/tri_pic/tritium_decay_experiment_black_box_circuit_diagram_IMG_3883.GIF

    on pin 9 of the PIC.

    What was the temperature resolution of this setup? When you mention calibration
    point, do you mean a one time design calibration or a calibration for
    each device? I know they use diode junctions on chips to measure temperature, >but typically they use a special circuit to drive with two known currents, >eliminating the need for calibration, no?

    Well in this case I wanted to stabilize the temperature,
    so measured the ADC steps for the temperature I wanted
    and the control loop then steered towards that.
    http://panteltje.com/panteltje/tri_pic/
    In the same way you can set an alarm level.
    There is a linear slope of about -2.1 mV / degree C for a Si diode, accurate enough for calculating heatsink temperature.
    If you power the junction via a resistor from some higher voltage, say 5V or 12V then the current change due to
    Vcb change is not really that much over a normal range.
    https://electronics.stackexchange.com/questions/13195/diode-temperature-effect

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Rick C@21:1/5 to Jan Panteltje on Sun Jan 23 06:09:48 2022
    On Sunday, January 23, 2022 at 8:16:09 AM UTC-5, Jan Panteltje wrote:
    On a sunny day (Sun, 23 Jan 2022 04:06:46 -0800 (PST)) it happened Rick C <gnuarm.del...@gmail.com> wrote in
    <bae72651-1e98-43de...@googlegroups.com>:
    On Sunday, January 23, 2022 at 2:17:19 AM UTC-5, Jan Panteltje wrote:
    On a sunny day (Sat, 22 Jan 2022 19:14:32 -0800 (PST)) it happened Rick C >>

    Yeah, resistors and capacitors with a thermistor are looking pretty good. >>
    Any diode will function as temperature sensor.
    Been there done that, even used the forward biased cb junction from a TO220
    transistor screwed to the heatsink.
    Is sort of linear, and takes only one calibration point, collector at ground
    potential from heatsink, no isolation needed.
    Any old TO220 will do :-)
    http://panteltje.com/panteltje/tri_pic/tritium_decay_experiment_black_box_circuit_diagram_IMG_3883.GIF

    on pin 9 of the PIC.

    What was the temperature resolution of this setup? When you mention calibration
    point, do you mean a one time design calibration or a calibration for
    each device? I know they use diode junctions on chips to measure temperature,
    but typically they use a special circuit to drive with two known currents, >eliminating the need for calibration, no?
    Well in this case I wanted to stabilize the temperature,
    so measured the ADC steps for the temperature I wanted
    and the control loop then steered towards that. http://panteltje.com/panteltje/tri_pic/
    In the same way you can set an alarm level.
    There is a linear slope of about -2.1 mV / degree C for a Si diode, accurate enough for calculating heatsink temperature.
    If you power the junction via a resistor from some higher voltage, say 5V or 12V then the current change due to
    Vcb change is not really that much over a normal range. https://electronics.stackexchange.com/questions/13195/diode-temperature-effect

    Would you need to do the calibration for every unit built, or just once for the design? Does the voltage for your set point vary with normal device variations?

    I ask this because I thought it was the slope with temperature that is pretty consistent between devices while the details of the measured voltage would vary. So to avoid having to calibrate each device measurements were required at two currents?

    Or are you saying your requirements simply don't require that much accuracy?

    --

    Rick C.

    +- Get 1,000 miles of free Supercharging
    +- Tesla referral code - https://ts.la/richard11209

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  • From Jan Panteltje@21:1/5 to gnuarm.deletethisbit@gmail.com on Sun Jan 23 14:29:03 2022
    On a sunny day (Sun, 23 Jan 2022 06:09:48 -0800 (PST)) it happened Rick C <gnuarm.deletethisbit@gmail.com> wrote in <302ce5e5-314e-41f2-a8a6-530b06367752n@googlegroups.com>:

    On Sunday, January 23, 2022 at 8:16:09 AM UTC-5, Jan Panteltje wrote:
    On a sunny day (Sun, 23 Jan 2022 04:06:46 -0800 (PST)) it happened Rick C
    <gnuarm.del...@gmail.com> wrote in
    <bae72651-1e98-43de...@googlegroups.com>:
    On Sunday, January 23, 2022 at 2:17:19 AM UTC-5, Jan Panteltje wrote:
    On a sunny day (Sat, 22 Jan 2022 19:14:32 -0800 (PST)) it happened Rick C >> >>

    Yeah, resistors and capacitors with a thermistor are looking pretty good.

    Any diode will function as temperature sensor.
    Been there done that, even used the forward biased cb junction from a TO220
    transistor screwed to the heatsink.
    Is sort of linear, and takes only one calibration point, collector at ground
    potential from heatsink, no isolation needed.
    Any old TO220 will do :-)
    http://panteltje.com/panteltje/tri_pic/tritium_decay_experiment_black_box_circuit_diagram_IMG_3883.GIF

    on pin 9 of the PIC.

    What was the temperature resolution of this setup? When you mention calibration
    point, do you mean a one time design calibration or a calibration for
    each device? I know they use diode junctions on chips to measure temperature,
    but typically they use a special circuit to drive with two known currents, >> >eliminating the need for calibration, no?
    Well in this case I wanted to stabilize the temperature,
    so measured the ADC steps for the temperature I wanted
    and the control loop then steered towards that.
    http://panteltje.com/panteltje/tri_pic/
    In the same way you can set an alarm level.
    There is a linear slope of about -2.1 mV / degree C for a Si diode, accurate enough for calculating heatsink temperature.
    If you power the junction via a resistor from some higher voltage, say 5V or 12V then the current change due to
    Vcb change is not really that much over a normal range.
    https://electronics.stackexchange.com/questions/13195/diode-temperature-effect

    Would you need to do the calibration for every unit built, or just once for the design? Does the voltage for your set point
    vary with normal device variations?

    I ask this because I thought it was the slope with temperature that is pretty consistent between devices while the details of
    the measured voltage would vary. So to avoid having to calibrate each device measurements were required at two currents?

    Or are you saying your requirements simply don't require that much accuracy?

    Driving the heatsink (in my case the alu plate that holds the photo diodes, opamp amplifier and tritium light) to
    a specific temperature and maintaining it from there from the ADC steps gives very very high accuracy.
    The system is basically a thermostat
    So calibrated at a specific temperature for that specific instrument once as there is only one.


    If you wanted to know ADC steps for other temperatures do the mV / C thing. John wants to measure heatsink temperature over a big range I think, this would work fine with same small error.
    But you could just as well glue some LM35 or so to the heatsinks .. I have used those too.
    Or some other sensor chip with i2c or spi interface.
    Tom was joking about using a FLIR camera and doing the video processing in FPGA, gives you about +-2 degrees C accuracy or so.

    On the other end of the spectrum: we had 'clicksons' in the past that would open at some high temperature.
    No idea what his specs are
    https://www.budgetronics.eu/en/switching/other-switches/clickson-switches-off-above-180-celcius-16a-manual-reset/a-18639-10000073

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Lasse Langwadt Christensen@21:1/5 to All on Sun Jan 23 09:50:14 2022
    søndag den 23. januar 2022 kl. 04.14.36 UTC+1 skrev gnuarm.del...@gmail.com:
    On Saturday, January 22, 2022 at 6:29:32 PM UTC-5, lang...@fonz.dk wrote:
    lørdag den 22. januar 2022 kl. 04.28.58 UTC+1 skrev gnuarm.del...@gmail.com:
    On Friday, January 21, 2022 at 6:42:00 AM UTC-5, lang...@fonz.dk wrote:
    fredag den 21. januar 2022 kl. 03.08.06 UTC+1 skrev jla...@highlandsniptechnology.com:
    On Thu, 20 Jan 2022 11:51:16 -0800 (PST), Lasse Langwadt Christensen <lang...@fonz.dk> wrote:

    torsdag den 20. januar 2022 kl. 17.31.18 UTC+1 skrev jla...@highlandsniptechnology.com:
    This uses an FPGA LVDS input as a comparator, and one external RC, to
    make an ADC. Just need an algorithm to process the flop output. >>
    A simpler ADC should be possible.


    more than one way to do it, one is basically successive approximation with a pwm dac
    another is delta-sigma with RC as "integrator" that might have an advantage in that the
    comparator doesn't follow the input signal it is always ~1/2 Vcc That's certainly better; the FPGA LVDS receivers are mediocre comparators. But the game was to minimize the number of external parts. I'll be digitizing a thermistor on a heat sink, so it's not a precision thing.

    If we go with an available Lattice FPGA, it doesn't have an ADC.

    Some sort of delta-sigma signal processing would be interesting.

    I could use an LM71, SPI temp sensor, which is just not as interesting.
    even simpler tmp05/tmp06 which is pwm output so all you need is a counter in the fpga

    or for easy mounting on a heat sink, https://dk.farnell.com/smartec/smt172-220/temperature-sensor-1deg-c-to-220/dp/2543396
    Isn't the FPGA the place where you put arbitrarily complex logic? Why try to minimize it?
    why spend time to implement a SPI, use three/four pins, or logic and extra parts to fudge an ADC and calibrate that
    when you can get a calibrated part that only need a single pin and very simple logic
    Not sure what you are comparing to what. An ADC inside the FPGA uses no external parts other than perhaps resistors and capacitors. You are talking about a temperature sensor, I was only talking about an ADC. If the cost is paramount, the passives are
    cheaper than the TMP05/06, only a few of them are active, in stock in small quantities at Digikey and cost dollars!!! Am I looking at the wrong parts? I've used an analog temperature sensor that was only $0.10 in quantity, the TMP236! Well, looks like
    they are a bit more now, $0.27. I got a penny happy group of designers to use that instead of a thermistor which was the same price.

    The semiconductor shortage seems to have decimated the inventory of temperature sensors. Digikey will show 15 or more parts, but only 2 in stock and 52 week lead times once those are gone!

    Yeah, resistors and capacitors with a thermistor are looking pretty good.

    sure if you need to build thousands, if you only 100 maybe not so much


    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Rick C@21:1/5 to lang...@fonz.dk on Sun Jan 23 10:03:48 2022
    On Sunday, January 23, 2022 at 12:50:18 PM UTC-5, lang...@fonz.dk wrote:
    søndag den 23. januar 2022 kl. 04.14.36 UTC+1 skrev gnuarm.del...@gmail.com:
    On Saturday, January 22, 2022 at 6:29:32 PM UTC-5, lang...@fonz.dk wrote:
    lørdag den 22. januar 2022 kl. 04.28.58 UTC+1 skrev gnuarm.del...@gmail.com:
    On Friday, January 21, 2022 at 6:42:00 AM UTC-5, lang...@fonz.dk wrote:
    fredag den 21. januar 2022 kl. 03.08.06 UTC+1 skrev jla...@highlandsniptechnology.com:
    On Thu, 20 Jan 2022 11:51:16 -0800 (PST), Lasse Langwadt Christensen
    <lang...@fonz.dk> wrote:

    torsdag den 20. januar 2022 kl. 17.31.18 UTC+1 skrev jla...@highlandsniptechnology.com:
    This uses an FPGA LVDS input as a comparator, and one external RC, to
    make an ADC. Just need an algorithm to process the flop output. >>
    A simpler ADC should be possible.


    more than one way to do it, one is basically successive approximation with a pwm dac
    another is delta-sigma with RC as "integrator" that might have an advantage in that the
    comparator doesn't follow the input signal it is always ~1/2 Vcc That's certainly better; the FPGA LVDS receivers are mediocre comparators. But the game was to minimize the number of external parts. I'll be digitizing a thermistor on a heat sink, so it's not a
    precision thing.

    If we go with an available Lattice FPGA, it doesn't have an ADC.

    Some sort of delta-sigma signal processing would be interesting.

    I could use an LM71, SPI temp sensor, which is just not as interesting.
    even simpler tmp05/tmp06 which is pwm output so all you need is a counter in the fpga

    or for easy mounting on a heat sink, https://dk.farnell.com/smartec/smt172-220/temperature-sensor-1deg-c-to-220/dp/2543396
    Isn't the FPGA the place where you put arbitrarily complex logic? Why try to minimize it?
    why spend time to implement a SPI, use three/four pins, or logic and extra parts to fudge an ADC and calibrate that
    when you can get a calibrated part that only need a single pin and very simple logic
    Not sure what you are comparing to what. An ADC inside the FPGA uses no external parts other than perhaps resistors and capacitors. You are talking about a temperature sensor, I was only talking about an ADC. If the cost is paramount, the passives
    are cheaper than the TMP05/06, only a few of them are active, in stock in small quantities at Digikey and cost dollars!!! Am I looking at the wrong parts? I've used an analog temperature sensor that was only $0.10 in quantity, the TMP236! Well, looks
    like they are a bit more now, $0.27. I got a penny happy group of designers to use that instead of a thermistor which was the same price.

    The semiconductor shortage seems to have decimated the inventory of temperature sensors. Digikey will show 15 or more parts, but only 2 in stock and 52 week lead times once those are gone!

    Yeah, resistors and capacitors with a thermistor are looking pretty good.
    sure if you need to build thousands, if you only 100 maybe not so much

    Building 100 still requires 100 ICs... if you can get them. Whatever.

    --

    Rick C.

    ++ Get 1,000 miles of free Supercharging
    ++ Tesla referral code - https://ts.la/richard11209

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