Got myself a mini fridge

Purchased a cheap mini fridge for converting into a sous-vide cooker. I hear these things are pretty rubbish at cooling your beer with, but from experience, peltier devices are much better at heating duty.

Not much space inside, but that’s a good thing – less thermal mass to worry about, and as long as it fits a steak or two, all good.

The thing has a three way switch to enable cooling or heating mode, that’s good, just what we need for sous vide

As an engineer, the urge to take this thing apart to see how it works is overwhelming.

So the insides look pretty standard, but they are EXACTLY what is needed.

At the top there is a heatsink, under which must be the peltier device.

On the right is the yellow mains AC to 12V DC board, with its rectification and smoothing and regulation circuits. Two wires come off this board carrying 12V DC and GND to the green switch board on the left.

This green switch board on the left does two things – switch between mains power and 12V DC power from the external socket, and switch between heat and cool mode. It does this by simply reversing the polarity of the peltier device – feeding in 12V one way causes the inside of the fridge to cool down (and the back to heat up), and feeding in 12V in the other direction causes the inside of the fridge to heat up (and the back to cool down).

So it looks like all I need to do is to add a transistor in there to control the power to the green board, and add some temperature sensors.

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