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.
cheap ADC
Started by ●January 20, 2022
Reply by ●January 23, 20222022-01-23
Reply by ●January 23, 20222022-01-23
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
Reply by ●January 23, 20222022-01-23
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
Reply by ●January 23, 20222022-01-23
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-effectWould 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
Reply by ●January 23, 20222022-01-23
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
Reply by ●January 23, 20222022-01-23
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
Reply by ●January 23, 20222022-01-23
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 muchBuilding 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
