Hi Tom I understand your idea but also think the sensor needs these common gnd points, not so much the N/C pins but the gnd is must.
On the subject of cooling...getting disappointing results with the 30mm SQ TEC. Supposed to be:
TES1-12703 - Voltage: 12V
- Umax(V) : 15.4V
- Imax(A) : 2A
- Qmax(W): 27W
- △TmaxQC=0(C):67 (max temp diff between module sides)
- Dimensions : 30mm x 30mm x 3.2mm
- Red = +ve, blk = -ve. Writing (or red lead on right) = cold side
- Suggested power = 12 x 2 = 24Watts. (ideal)
- Actual power = 13.45 x 2.9 = 39watts (max measured)
I only got down to around 3ºC (2.5ºC min on cold heatsink) with hot side HSF at 32ºC max. Now the hot side is difficult to measure as the cooling fans is blowing on the probe which cools it and gives bad readings, but the HSF never got hot enough, with calibrated finger mk1.
The cold side had a small heatsink on it and I even placed the cold side in a plastic case to retain this cooling. Yet it reached min ~2.5ºC and went no further.
All this was done with an ambient ~22ºC, PSU 13.44V and max draw from 3A to 2.7A. No PWM just straight cooling. I did try some PWM with a motor controller and the results pretty much mirrored this.
Which tells me either I'm doing it wrong or this TEC is not working to specs....Hmmm go figure. I tried larger fans and HSFs all the same or even worse.
