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I am experimenting with different ways to heat up and cool down a peltier to a specific setpoint. Heating up the peltier to a setpoint using a PID has been relatively simple, and right now I am working on optimizing the speed of cooling it down.

My design right now is to use a DPDT relay to flip the polarity, and reversing the PID. This seems to work well in theory, but I have concerns that the rapid temperature difference might hurt or break the peltier over time (like running cold water over hot glass). Does anyone know if this concern is valid? If it is, does anyone have any advise on how quickly I can cool down the peltier without damaging it?

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There is plenty of info on the web regarding this subject. The biggest problem is fast rise time as a pletier acts as a voltage source. Last time I checked its bad to plug in power supplies backwards. Rate limit any control signal into a peltier and avoid switching it from postive to negative instantly.

I can't speak for the time because it is application specific and device specific. I've seen a half to 1 second to wait in some applications for the peltier to 'settle' and reduce the delta-T across the device before switching polarity. In your application this could also be accomplished by zeroing out the PID before and after switching or a relay before the DPDT. Some applications use an inductor to limit inrush current.

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