TEC controller

[NickMu]

Hi All,

After gathering all the stock ingredients I ventured to prototype something to get me started (see attached schematic). Most of the stuff was already made from older projects so I just needed some re-wiring.
To my surprise, at the first try, I was able to drive a TEC with an 80KHz output from an older PIC 12F683 board. I will have to look back to find the code that runs it but it basically outputs 80KHz of about 40% duty cycle PWM for about 3 seconds and about 75% for 3 seconds.
The output voltage to the TEC goes from 5.5V to 8.5V with a current draw of 1A and respectively 3A.
Checking with an old scope the TEC voltage is pretty clean.
I separately built a refrigeration box out of ¾” Styrofoam and I was able to maintain a bottle of wine at about 45⁰F for two days running the TEC under 5.5 V from a separate PSU. I will do some more testing like this to figure out the minimum voltage that is needed to maintain a decent temperature in the cooler without having to turn the TEC OFF. I will do so after replacing the first wine bottle which became “a casualty of the project” and I opened it to celebrate the first successful test. This is becoming a fun project. LOL
Next step will be to fine tune the switching frequency for efficiency and the needed PWM range to get my lowest and highest output.

I will keep you posted and I might come back with some clarifications and maybe questions. I will also post the code that I’m running after I get it optimized.

Nick