Anyone have an estimated emissivity for the IVAC 9000 radiators? - Page 1
Forum section: electronics / general

author: globoy
author_rank: Frequent Contributor
timestamp: February 23, 2021, 06:06:43 pm
content: This forum is really fantastic. I am following in Frasier's 2018 footsteps to try to make some DIY blackbody radiators for learning and then to see if I can characterize and possibly improve the accuracy of a camera I have designed.I got an IVAC 9000 from ebay and have been playing with it. It seems to be operable. It warms up, displays the "Check Ready" status and seems to hold stable temperatures. I put my Agilent's K-type thermocouple into a screw hole next to the device's temperature sensor and my Lepton 3.5-based camera so the radiator fill's the camera's field of view. This lead to some questions I am hoping someone here has experience with.1. The device's instructions say an in-ear temperature probe being calibrated should read 26.0°C (+/- 0.3) for the low side and 38.0°C (+/- 0.1) for the high side. My DMM shows 24.3°C for the low side and 36.5°C for the high side. I realize that my meter has an error band and I may not be making ideal contact with its temperature sensor, but should I expect that the metal radiators are 26 and 38°C if the unit is working properly? Or is it possible that the IVAC thermometer's somehow adjust what they read to really reflect the in-ear temperature.2. What estimate should I use for the emissivity of the coating on the radiators? Could I re-coat them with a paint for which I know the emissivity?Below are images of my setup and the output from the Lepton peering at the low temperature radiator.Thanks.

author: _Wim_
author_rank: Super Contributor
timestamp: February 24, 2021, 07:50:31 pm
content: According to this paper (https://www.tandfonline.com/doi/abs/10.1080/19315775.2014.11721683) the emissivity for such a calibrator was 0.972. The emissivity of the ear canal is apparently 0.9988 according to a reference in this paper.Tip: use sci hub to access the full paper if desired.

author: globoy
author_rank: Frequent Contributor
timestamp: February 24, 2021, 09:05:22 pm
content: Thanks for that information!

author: bap2703
author_rank: Regular Contributor
timestamp: February 24, 2021, 09:22:52 pm
content: Quote from: globoy on February 23, 2021, 06:06:43 pmThe ear conduct should be quite close to a blackbody : made of water + it's a cavity.It means that when you measure the temperature in the ear, you expect a blackbody. So to calibrate an ear thermometer you do it against a blackbody simulator.Conclusion: your device should be at 26°C and 38°C and the emissivity pretty close to one.Error most likely will come from the temperature measurement/regulation electronics.Maybe you can rent a calibrated infrared thermometer to have another measurement and conclude which of your thermocouple measurement or your blackbody simulator isn't accurate.

author: globoy
author_rank: Frequent Contributor
timestamp: February 24, 2021, 09:47:37 pm
content: Quote from: bap2703 on February 24, 2021, 09:22:52 pmOk. Thanks for this too. I will look for an accurate IR thermometer - probably see if I can borrow a good in-ear thermometer.

author: _Wim_
author_rank: Super Contributor
timestamp: March 10, 2021, 08:07:12 pm
content: After seeing your post, I put in a low (15$ ) offer on one of these Ivac Core Check 9000 calibrators and the seller accepted! Today it arrived. Attached a measurement of the plates with my Flir E30 who thinks he is an E60Thermal span set to only 1°C. The 26°C plate seems a little higher in my case, but the Flir is from 2012 and has probably not been calibrated since. Emissivity was set to 0.99.

author: _Wim_
author_rank: Super Contributor
timestamp: March 10, 2021, 08:55:21 pm
content: @Fraser, in case you would buy such a toy also and it comes without a power supply, attached my investigation work to power it up.It uses normally a 5V 5A power supply (CL40 7605, datasheet attached).I currently used some clips as shown in the picture attached, but for that to work, you need a bridge at the bottom of the board. This had me looking for a bit, as the device powers correctly up without it, but does not heat up...

author: Fraser
author_rank: Super Contributor
timestamp: March 11, 2021, 07:40:34 pm
content: Thank youI own three IVAC 9000’sPost 42 onwards of this thread may be of interesthttps://www.eevblog.com/forum/thermal-imaging/black-body-thermal-references-and-fraser_s-new-black-body-project-)/msg1556140/#msg1556140I discovered the need to link the ‘on’ pin of the power connector in order to get the unit working. I do not know why that activation pin is needed.Fraser

author: _Wim_
author_rank: Super Contributor
timestamp: March 11, 2021, 08:43:11 pm
content: Quote from: Fraser on March 11, 2021, 07:40:34 pmI should have known betterThe linking of the pin in needed because the original adapter has two 5V pins in the DIN connector (pin 1 & 2), and both are used on the board but are not linked together on the pcb. So when working with only a single 5V clip like I did, the board powers up but does not heat up. This got me confused initially.

author: _Wim_
author_rank: Super Contributor
timestamp: March 11, 2021, 08:58:31 pm
content: So my best guess would be that they allowed to use a different voltage for powering the peltier elements, hence you need to connect "two" supplies to make the unit work (so not PSU ok). One of the 5V supplies draws only around 100mA, the other one draws the full power.

author: Fraser
author_rank: Super Contributor
timestamp: March 11, 2021, 09:05:29 pm
content: Interesting, thanksFraser

author: Fraser
author_rank: Super Contributor
timestamp: March 11, 2021, 09:12:17 pm
content: It would be great if there was a way to set the two black bodies to more useful temperatures for 2 point calibrations. 20C and 60C would be useful as huge temperature differences are not normally required for basic 2 point calibrations. Sadly I have not had time to delve into the design of these IVAC units and I suspect the temperature is hard coded into their firmware as they are for a specific use. Modifying the temperature sensor feedback loop to the processor or its ADC might work but that would need some investigation into how best to fool the processor. As we are trying to make fixed temperature references it may be possible, and a lot easier than making a variable temperature reference.Fraser

author: globoy
author_rank: Frequent Contributor
timestamp: March 11, 2021, 11:58:57 pm
content: What do you think about hooking one of the two radiators up to a Wells CTI FTC100d-based controller? I have one of those although it's a 12V unit currently.I did look at the circuitry of the IVAC unit. I guess one would remove the uC and the ADC chip although perhaps the ADC could still be used. The temp sensor connections to that chip were interesting. Instead of using the voltage input, they seemed to be coupled to the ohms attenuator terminals.

author: Fraser
author_rank: Super Contributor
timestamp: March 12, 2021, 06:23:59 am
content: Possibly a Pt100 RTD sensor for accuracy ?Fraser

author: _Wim_
author_rank: Super Contributor
timestamp: March 12, 2021, 07:16:39 pm
content: Quote from: Fraser on March 11, 2021, 09:12:17 pmMy intention is to have a look at something like this, but no promises. So many projects, so little time! Hopefully something fairly easy can be done be bodging in some resistors in at the right places...

author: _Wim_
author_rank: Super Contributor
timestamp: March 12, 2021, 08:50:54 pm
content: I had a quick play in the lab (no time to wait for stable or accurate results, just a quick proof on concept only).What I found so far, it that the temperature sensor is an NTC. At room temperature (+-22°C) it was around 12.5K, at 38°C is dropped to 5K.This equates to a beta of around 5300 (https://www.ametherm.com/thermistor/ntc-thermistor-beta)Knowing this beta we can calculate what the resistance would be at for example 60°C => 1.9K (https://www.electro-tech-online.com/tools/thermistor-resistance-calculator.php)We know the controller tries to adjust for around 5K, so if we put 3.1K in series with the NTC, the controller should adjust to around 60°C. Stability will be less good, because we are more in the flat region of the NTC, so temperature variation create less resistance change.My first test with 3.1K in series is attached: rise is however very slow, and not sure 60°C will be feasible, but 50°C is maybe doable this way. Will try some more later this weekend.

author: Fraser
author_rank: Super Contributor
timestamp: March 12, 2021, 09:32:27 pm
content: Excellent workFraser

author: globoy
author_rank: Frequent Contributor
timestamp: March 12, 2021, 10:47:10 pm
content: Very cool!

author: _Wim_
author_rank: Super Contributor
timestamp: March 14, 2021, 02:16:55 pm
content: Done some more testing yesterday and today.First test was to put a 12K resistor in series to test how far it would heat-up without any regulation. Ivac was powered by 5Vdc.Both voltage and average current to the peltier were logged (red trace= current in A, bleu trace=voltage).As can be seen, it was struggling to achieve 50°C. Around 14:31 I increased the power supply to 5.5Vdc, and got again more rise in temperature. So clearly a little more voltage would be beneficial.

author: _Wim_
author_rank: Super Contributor
timestamp: March 14, 2021, 02:27:26 pm
content: For the next test I removed CR1,CR2 and CR4 (TVS diodes for 5V, shorting to ground in case of excess voltage).This way I could increase power to the H-bridge powering the peltier elements, and keep still a 5V supply to the microcontroller and ADC.Attached is the pin out of the original power supply.pin 1 gives power to the peltier elements, pin 2 gives power to the micro and ADC, 3 to 5 should be tied together to ground.I tried several runs, first with 6.5V, than with 7V and finally with 8V for the peltier elements. Each time heating up went a little faster, and stability (aka "check ready") was also sooner reached.Remark: the removal of CR2 is normally not necessary, this one protects the 5V for the micro and ADC, I have later reinstalled it but forgot to take a picture of it.

author: _Wim_
author_rank: Super Contributor
timestamp: March 14, 2021, 02:32:22 pm
content: Now being able to heat-up easily to 60°C, I installed a 5K 10-turn pot in series with the NTC.This way I could adjust the pot until exactly 60°C on average was archived (remark: I had to redo it as I forgot to change the emissivity to 0.99).I used my flir E60 for the calibration, which is probably not ideal, but at least it allow me to evaluate the effect of placing a lens in front of the flir (which cause a +-2°C lower temperature with my ZnSe lenses).

author: _Wim_
author_rank: Super Contributor
timestamp: March 14, 2021, 02:46:16 pm
content: As using 2 power supplies to power this is kind of annoying, and the microcontroller and ADC draw only 50mA, I bodged in an 7805 and replaced the DIN connector by a power connector so I could easily connect a 8V 5A switch mode power supply adaptor (because 7V adaptors are not easily found on Ali-express, I opted to further increase the power to 8V).Disclaimer: I have no idea how much margin there is, do so at you own risk!I also put everything back in the housing (the front panel pcb can easily be installed behind the back body radiators), and closed the openings with some matt black tape.

author: _Wim_
author_rank: Super Contributor
timestamp: March 14, 2021, 02:47:06 pm
content: Final test:During the final heat-up test in its housing I again forgot to change the emissivity from 0.97 to 0.99, so the little jump around 14.17:40 is me adjusting the emissivity)I am very satisfied with the end result, it remains quite stable (unsure if the small fluctuations are related to my flir or the black body, but a good chance it is the flir).Final value of the series resistor (10-turn pot) in my case was 3.35K

author: _Wim_
author_rank: Super Contributor
timestamp: March 14, 2021, 02:54:44 pm
content: There is still one on Ebay for only 10$:https://www.ebay.com/itm/Ivac-Core-Check-Calibrator-9000A-15663-E42/253802723165?hash=item3b17d2375d:g:McgAAOSw6sdbadM~An absolute steal! Thanks to Fraser for pointing this out originally, and thanks to globoy for reminding us again of this excellent tip!

author: _Wim_
author_rank: Super Contributor
timestamp: March 14, 2021, 03:12:45 pm
content: Possible future improvements:- install a selector with to select between different series resistors to have multiple temperatures- bring a smaller version of the lcd to the front to have an indication when the temperature is reached & stable

author: Fraser
author_rank: Super Contributor
timestamp: March 14, 2021, 08:14:47 pm
content: _Wim_Great work, thank youFraser

author: globoy
author_rank: Frequent Contributor
timestamp: March 15, 2021, 02:54:49 am
content: Thanks for all that, _Wim_. An easier start than trying to replace the controller. As today was a very snowy day I hacked on my unit. Mostly I followed your lead but since I didn't have an 8V PSU, I modified the IVAC unit and I played a little with the cold side.I adjusted the PSU to 6V out by including a 10k resistor in parallel with a 3.3k part (R21) in the feedback path and adjusting the trim pot. Above about 6.1V the PSU crowbar fires. I suspect that could also be adjusted up but didn't pursue that today. I put a 1N4001 diode in series with the branch going to the logic circuits (in series with FB4) to drop the voltage to a legal level.I was able to achieve 50C on the hot side with no problem.I also put the largest value multi-turn trim pot I had (20k) in parallel with the NTC for the low side. Unfortunately it was too low of a resistance value and the unit could not achieve a temperature lock. I then tried some discrete resistors and had success with a 47k resistor, although that took a long time to reach stability. I think the temperature was around 19C (measured 19.2C with my Agilent temperature sensor stuffed in a screw hole on the cold-side block).I'll try again with a 100k trim-pot and try to post some plots. I'm still trying to figure out the best way for me to have a precise temperature measurement as the goal of this project is a calibrator my the camera I designed.

author: globoy
author_rank: Frequent Contributor
timestamp: March 15, 2021, 02:55:48 am
content: And pics of the display board (with wire extensions) and cold side measurement.

author: _Wim_
author_rank: Super Contributor
timestamp: March 15, 2021, 06:58:11 pm
content: Quote from: globoy on March 15, 2021, 02:54:49 amThanks for posting your tests also. I wondered how good cooling would be, but I kinda expected cooling down would only be minimal. I think cooling was only provided to achieve 26°C in hot environments, and potentially also to regulate out small overshoots in temperature during heating up to achieve a faster lock.Quote from: globoy on March 15, 2021, 02:54:49 amAccurate temperature calibration is hard. For this purpose I would expect a small pt100 connected to a high res dmm would be the most accurate (because they have a "large" contact surface and do not need a reference junction). I bought some small ones on Ali-express (https://www.aliexpress.com/item/32689032460.html?spm=a2g0s.9042311.0.0.27424c4dYv6HSk) to build a laser power meter, but have not done anything with them yet. These would fit the side entry of the black body normally.I would fill the the hole on the black body with some thermal compound so the pt100 is completely submerged in paste. This should ensure a good coupling (there will be a lag in measured temperature, but once stable, the results should be fairly accurate). The hard part is the accuracy of the PT100 itself. Maybe this weekend I will put one in boiling water and melting ice, and then compare it with the results of the flir. This should hopefully be +-1°C accurate.

author: Fraser
author_rank: Super Contributor
timestamp: March 15, 2021, 10:38:50 pm
content: Remember that Black Body units are calibrated either as ‘Actual’ or ‘Measured IR’ temperature. ‘Actual’ uses a surface contact sensor on the emission plate and ‘Measured IR’ uses an accurate IR Radiometer that is viewing the emission plate.‘Actual’ calibration requires knowledge of the emission plate emissivity‘Measured IR’ calibration takes the emissivity of the emission plate into account as part of the calibration process as the Radiometer views the emission plate. ‘Measured IR’ calibration is liable to the measurement tolerance of the Radiometer so ‘Actual’ calibration using a very accurate contact sensor can be more accurate if the emissivity of the emission plate is well documented and tested.Fraser

author: Fraser
author_rank: Super Contributor
timestamp: March 15, 2021, 11:30:38 pm
content: If you work with a true surface emissivity of 0.95, you will not be far off but tests would reveal the true emissivity of the black paint coating on the emission plate.Fraser

author: _Wim_
author_rank: Super Contributor
timestamp: March 16, 2021, 07:11:51 pm
content: Quote from: Fraser on March 15, 2021, 10:38:50 pmGood point!These were indeed adjusted to give a reading of 38°C to simulate an in ear temperature which has emissivity of almost 1 (0.9988 according to the paper I posted in the 3rd post of this thread), and this was confirmed by the initial measurements with my flir Exx (38.1°C with its emissivity set to 0.99), and also when I tested our infrared fever thermometer we have for the kids (showed exactly 38.0°C)But the paint probably on the black body will have a lower emissivity, so the actual temperature of black body must be higher to achieve this result. According to the same paper the emissivity of such a calibrator was 0.972, so the actual black body temperature should be 38°C/0.972 = 39.1°C. This small difference is already difficult to measure accurately, but it is indeed best to know what the theoretical value should be.

author: _Wim_
author_rank: Super Contributor
timestamp: March 16, 2021, 07:14:53 pm
content: Quote from: _Wim_ on March 16, 2021, 07:11:51 pmFrom the above, we could also do the reverse calculation. These are probably still perfectly in spec at 38°C, so when measuring the actual temperature, we could calculate the emissivity!

author: _Wim_
author_rank: Super Contributor
timestamp: March 16, 2021, 07:17:59 pm
content: I just reread the first post from globoy, he measured an actual temperature that was lower than 38°C. This I would not expect, or do I have some flaw in my thinking above?

author: _Wim_
author_rank: Super Contributor
timestamp: March 16, 2021, 07:21:36 pm
content: Quote from: Fraser on March 15, 2021, 11:30:38 pmI should of read that post of you tooThanks for already confirming my logic BEFORE I asked the question!

author: globoy
author_rank: Frequent Contributor
timestamp: March 16, 2021, 07:27:36 pm
content: I wouldn't trust my temperature measurements to date. It's also possible my unit is not accurate anymore.I have taken your advice and will try to incorporate two precision RTDs into the radiators (with thermal grease). I hope to try with one tonight.From the instructions on the top of the unit it seems that the in-ear IR thermometers were meant to see the 26/38°C values so assuming the paint could not match the 0.9988 emissivity of the inner ear then your assumption must be right. The block temperatures must be slightly higher. I guess measuring the radiator temperature precisely would allow deducing the actual emissivity of the paint.

author: _Wim_
author_rank: Super Contributor
timestamp: March 20, 2021, 10:50:02 am
content: Quote from: _Wim_ on March 15, 2021, 06:58:11 pmFirst step, test the above PT100's for accuracy with boiling water and ice. Result are quite accurate!The boiling water fluctuated between 138.50 and 138.55 ohm, the melting ice was quite stable between 100.03 and 100.04 ohm. Meter was zero checked with parallel short banana cable.

author: _Wim_
author_rank: Super Contributor
timestamp: March 20, 2021, 12:33:47 pm
content: Ok, and now for the actual test...FLIR indicates 38.1 °C with emissivity set to 0.99.PT100 Resistance is 114.72 ohm and very stable (very occasionally going to 114.71, but 99% of the time at 114.72 ohm).According to this PT100 calculator (https://www.peaksensors.co.uk/resources/rtd-calculator-temperature-resistance/) this equates to 37.9°CVerified also again with our in ear thermometer, was again bang on 38.0°C. If I put the FLIR emissivity to 1.00, it also indicates 37.9°CThis would mean the emissivity of this black body must be quite high, possibly >0.98, although I find that hard to believe looking at available high emissivity paints and materials. The only thing that comes close is vacuum deposited black coating (https://www.acktar.com/products-services/high-emissivity-materials/)I am on the limit here of what I can accurately measure, and also have no intention to invest in "temperature nut" equipment

author: Fraser
author_rank: Super Contributor
timestamp: March 20, 2021, 12:48:12 pm
content: Very interesting resultsEmissivity of 0.98 is very achievable so it could be a high performance coatingThese were for medical use and, as we know, the cost of such kit is often high. This may have justified using high performance emission plates and coatings. These are certainly very nice bits of kitNo need to go down the ‘temperature nut’ pathThe temperature measurement tolerance of a typical thermal camera is enough to make that path unnecessary.Thank you for spending the time doing the testsMuch appreciated as my three units are sat doing nothing under my desk. It may be time to make them useful.Fraser

author: _Wim_
author_rank: Super Contributor
timestamp: March 20, 2021, 12:49:36 pm
content: Same test at above, but now with the series resistor installed again so the black body radiator regulates to 60°C. FLIR emissivity set to 0.99.Resistance reading is 123.38ohm which equates to 60.3°C. Flir reads 60.1°C

author: _Wim_
author_rank: Super Contributor
timestamp: March 20, 2021, 12:56:44 pm
content: Quote from: Fraser on March 20, 2021, 12:48:12 pmThese are indeed very nicely made. And for prices between 15 and 20$ on the US Ebay, this is an extremely good deal if you can use it.Glad I bought one to play around with. I also had lot's of fun doing these tests.

author: globoy
author_rank: Frequent Contributor
timestamp: March 20, 2021, 02:38:12 pm
content: Great, _Wim_! Thanks for posting your results. My order for PT100s was held up but I am looking forward to again following in your footsteps.

author: globoy
author_rank: Frequent Contributor
timestamp: March 28, 2021, 06:28:55 pm
content: I finally got my temperature sensors and had a chance to instrument my unit.I measure the low side to be 26°C as well. The low side is very stable and I see a little drift after the unit has dialed in the temperature. Interestingly while the high side heats up I've seen it overshoot on occasion. But then it settles back down.At 60°C my high side series resistor was about 3303 ohms (2-wire measurement). Slightly more drift on the high side that I attribute to the resistor's temperature coefficient (for example from night to day in my lab). At 6V in I couldn't quite get the high side to 65°C but could get it to 64°C.I think this unit is now good enough to run some experiments. Thank you again, Fraser and _Wim_, for all your work. This device can become a useful piece of kit.On the chart below, the X-axis is seconds.

author: _Wim_
author_rank: Super Contributor
timestamp: March 28, 2021, 06:34:02 pm
content: Quote from: globoy on March 28, 2021, 06:28:55 pmLooks very good!

author: Fraser
author_rank: Super Contributor
timestamp: March 28, 2021, 08:16:18 pm
content: Globoy,Nice workThat is a neat dual RTD thermometer you have produced. Any chance of sharing the design ?Fraser

author: globoy
author_rank: Frequent Contributor
timestamp: March 29, 2021, 02:11:21 am
content: Thank you Fraser, and sure. It's a pretty simple build around an ESP32, a pair of MAX31865 ICs and PT100 RTDs in a 4-wire configuration and a 2x8 character LCD module. I used a random ESP32 board I had laying around but I think almost any ESP32 dev board will work fine (see notes below). Code was done in Arduino with the ESP32 add-on. It has a very simple serial interface available for logging temperature data on both the built-in HW serial and a Bluetooth SPP serial. See below for zip files with the sketch and the version of the Adafruit MAX31865 library I used. Also see below for a quick hand drawn schematic.Parts1. I used a ESP32 WROOM module on a breadboard from circuitsetup.us (https://circuitsetup.us/index.php/product/solderable-breadboard-esp32-esp8266-esp01-module-breakout-with-3-94-x-2-375-x-1-875-100x60x25mm-project-box-2-pack/). This requires an external FTDI cable pinout serial interface (and the corresponding manual pressing of IO0, press/release of RST, release of IO0 to enter bootloader mode). But any ESP32 board with the appropriate IO (see the sketch) will work.2. A pair of Adafruit MAX31865 boards I got from Mouser (https://www.mouser.com/ProductDetail/485-3328). They're ready for 4-wire connections. Just have to add the connectors and pin-header.3. A pair of Hareaus 32208550 RTD sensors I also got from Mouser (https://www.mouser.com/ProductDetail/956-32208550). They are connected up with 4 wires (2 wires per lead) - heat shrink tubing around the solder joints and covered with thermal paste when inserted into the extra screw holes on top of the IVAC 9000 forward-facing aluminum blocks (next to its own temperature sensor).4. A 2 line, 8 character LCD module I had laying around (Hantronix HDM08216L-3). But any HD44780 type display should work fine. One might have to adjust the calls to lcd.begin() and lcd.setCursor methods in the sketch to match their display.5. A couple of LDO regulators (whole system takes less than 100 mA). Either two 5V units or one 5V unit and 3.3V unit (see below).I connected the input to the IVAC power supply on the main PCB (outputs of the ferrite beads going to the digital logic) and my IVAC power supply has been adjusted up to 6V.6. Misc parts. Some 100 uF electrolytic, 1 and 0.1 uF ceramic caps, 10K pot, 10K resistor, resistor selected for the LCD module backlight, buttons as necessary, etc.Power Supply ConsiderationsMy circuit.us board requires a 3.3V LDO for input->ESP32 conversion. I included a 5V LDO to provide power for the two Adafuit boards and the LCD module. The curcuit.us board has a terminal header for the FTDI cable for programming but only connects RX, TX and GND so the system must be powered externally for programming. (Plus the ugly manual entry and exit from bootloader mode).Many ESP32 dev boards have a built-in USB Serial chip and 5V -> 3.3V LDO plus auto-bootloader circuitry making programming much easier. If you use one of these then you can replace the 3.3V LDO with a 5V LDO followed by a schottky diode to power the board's VIN terminal. The diode prevents conflict between USB supplied power and board supplied power (well ideally you'd like a schottky on the USB power in as well).Some LCD modules are backlit and some are not. Some backlit models have a built-in current-limiting resistor and some don't so you'll have to match driving the backlight LED with an appropriate external resistor connected to 5V as necessary.Firmware Command InterfaceSuper simple command interface available over serial and Bluetooth serial. Type 'H' followed by carriage return (or enter 'H' into the Arduino serial monitor and click Send) to get it printed out.Temperature of sensor 0 (low-side)Code:T0<CR>Temperature of sensor 1 (high-side)Code:T1<CR>Log both temperatures at the log interval specified in mSec (minimum 500 mSec and 500 mSec increments, L=0 to stop)Code:L=<msec><CR>Zero timestamp (useful when starting a log you want to import into something that will graph it since most of them want the X-axis to start at 0).Code:Z<CR>Typical logging looks likeCode:31726.07 26.04 64.0531731.19 26.04 64.0531736.31 26.04 64.0531741.43 26.04 64.0231746.55 26.04 64.0531751.67 26.04 64.0531756.79 26.04 64.0531761.91 26.04 64.0531767.03 26.00 64.05Where the first column is seconds, the second column is temp 0 and the third column is temp 1.This code could also be stripped of the bluetooth serial stuff and probably run just fine on any old Arduino as well with appropriate pin remapping.

author: Fraser
author_rank: Super Contributor
timestamp: March 29, 2021, 07:17:49 pm
content: Globoy,Thank you for sharing your designFraser

author: Userli
author_rank: Regular Contributor
timestamp: May 01, 2022, 06:54:51 pm
content: I also purchased an IVAC 9000 but unfortunately it doesn't heat. The display shows R0.03 NOT READY, blinking at roughly 4 Hz. The unit draws 50mA and the 4 test points all show 5V. I exchanged the MosFETS, which seemed the most obvious possible problem to me but still no luck.Does anybody know what R0.03 means? I assume it's the error description?

author: _Wim_
author_rank: Super Contributor
timestamp: May 02, 2022, 05:43:33 am
content: Quote from: Userli on May 01, 2022, 06:54:51 pmHow are you powering it? It seems like only the control section gets power, and not the H-bridge section. Have a look at this post and the datasheet attached:https://www.eevblog.com/forum/thermal-imaging/anyone-have-an-estimated-emissivity-for-the-ivac-9000-radiators/msg3504564/#msg3504564The power supply connector has 3 pins connected to ground, and 2 pins connected to 5V. All of them are not shorted in the unit, so to make is work you do need to supply all of them, or add a solder bridge as shown in my post above.

author: Userli
author_rank: Regular Contributor
timestamp: May 02, 2022, 06:45:58 am
content: Thanks for the fast reply Wim.I followed in fact your post, put the bridge and powered it even at the same points.I tested the peltiers and the temperature probes. The uP works since the display works and the ADC also shows activity. The ANDs driving the MFETs seem to work but I didn't yet re-engineer the logic, which I assume ensures the right combination of MFETs of the H bridge to be driven or switch between cooling and heating?

author: _Wim_
author_rank: Super Contributor
timestamp: May 02, 2022, 06:55:09 am
content: Quote from: Userli on May 02, 2022, 06:45:58 amHmmm, maybe try and put 5V on pin 1&2 of the DIN connector, and wire pin 3&4&5 to ground? Maybe I forgot to document something when I made that post?It really does seem like the same issue I had when powering this up.As to the heating and cooling, I also presume it can do cooling as it has a full H-bridge, but because the regulation does not overschoot I have never seen it do any cooling?

author: _Wim_
author_rank: Super Contributor
timestamp: May 02, 2022, 07:13:56 am
content: Just a question, how much power does it draw when hooked up like above? It could be that this message is displayed as long as it is heating up and not stable in temperature, and it does take quite a while unit is it stable.The micro and control logic only draw about 50mA, so it your seeing currents in excess of 500mA it is working correctly and heating up the elements.

author: _Wim_
author_rank: Super Contributor
timestamp: May 02, 2022, 07:14:58 am
content: If I remember correctly, the unmodified unit took well over 10 mins to heat up and stabilize...

author: _Wim_
author_rank: Super Contributor
timestamp: May 02, 2022, 07:24:54 am
content: I found the original display in my parts bin and connected it again to my unit, "R0.03 not ready" is indeed displayed while heating up, so that is normal behavior.

author: Userli
author_rank: Regular Contributor
timestamp: May 02, 2022, 11:13:39 am
content: Thanks for testing! It's good to know that the controller part is happy and I don't need to worry about this part.The current is always around 50mA and I indeed left it for quite some time but looking at it with the IR camera, it's clear that the peltiers don't heat at all.I'll do some more testing on the power part...

author: _Wim_
author_rank: Super Contributor
timestamp: May 02, 2022, 01:03:17 pm
content: Quote from: _Wim_ on May 02, 2022, 06:55:09 amI checked my unit again, and powering it up with the single solder bridge as shown in the previous post should be ok. So it really seems something is not correct with the H-bridge. Just ask if you need me to measure any voltages on my unit to compare.

author: _Wim_
author_rank: Super Contributor
timestamp: May 02, 2022, 01:09:13 pm
content: Maybe another question, how much amps can your power supply deliver? When the H-bridge triggers it draws quite a bit of current (+-5A), and if the power supply sags this will reset the controller causing it to never really heat-up due to the constantly resetting.

author: Userli
author_rank: Regular Contributor
timestamp: May 02, 2022, 04:54:30 pm
content: Following your explanation, I was indeed wondering about the ground bridge and finally added it.It makes sense to have the uP and the power circuit somehow separate. However, since the power input is the reference for the MOSFET gates, they have to be related.My PS is 25V 5A. When powering the peltiers directly they draw less than 2A each, so 5A should be fine to power the whole unit.I'll do a bit more measuring....

author: Userli
author_rank: Regular Contributor
timestamp: May 02, 2022, 06:45:51 pm
content: Wim, would you mind to check pins 9,10,11 and 19 on the micro controller (those drive the H bridge as far as I can see)? I only see activity on pin 19.

author: _Wim_
author_rank: Super Contributor
timestamp: May 03, 2022, 06:33:26 pm
content: Quote from: Userli on May 02, 2022, 06:45:51 pmFrom top to bottom: 9, 10,11 and 19. Measured just after power up the unit.

author: Userli
author_rank: Regular Contributor
timestamp: May 04, 2022, 06:36:54 am
content: Thank you very much Wim!This is the same for my unit. I re engineered now the path from uP to MOSFETS. (I'll try to draw the schematics and post it here.)This leaves in principle only the logic gates and the MOSFETS as culprits.I'll continue measuring tonight...