Today I finished the PSU for the peltier element and connected the stm32f103 to the thermistor (the stm32f103 is still not measuring the voltage over the TEC). And here are the readings (sorry for the blurry photographs):
First, before the TEC was turned on:
It’s fairly hot in DK at the moment. The ambient temperature is 25-26°C.
Then after 5min with the TEC on. The voltage drop over the TEC is app. 8V, I have no idea what current draws, but the transformator is rated at 4A:
So it reaches a temperature difference of around 10°C. Not as much as I had hoped.. With some heatsink paste between the peltier element and the aluminium plates the temperature dropped another 1.5°C, still not anywhere the expected ΔT of 30°C.
So good animals are uncooked, as we say here in Denmark. I had a second look at the audine project to see if I had missed something. Most likely I have, but I didn’t find anything suspicious about my setup except that the TEC 12706 protrudes slightly on the cold side. I had some smaller TEC’s from another shopping spree, most notably the TEC 03506. You see the difference in size here:
And with the little one, it’s an entirely different story. The voltage drop across the smaller TEC was around 5.6V and the temperature difference was much greater. The CCD started to collect condensation, which is around the time I stopped the test:
The temperature at this point was -0.6°C 🙂