Dough Proofer Box

 My family like to buy frozen balls of pizza dough. This is a cheap way to make pizza which tastes good and can be customized. To use the frozen dough, it has to be thawed in the fridge overnight and then set out to rise at room temperature for 6 hours. But room temperature during the winter can be too cold for dough. Setting the dough on top of the DVR helps keep it warm, but I thought of a better solution.

I had a small electric cooler. It's like a tiny fridge, but uses peltier cooling. It's not very efficient and is only advertised for keeping drinks cool, not for safe food refrigeration. It has no temperature controls, just runs at full power all the time it's plugged in. I knew that it's simple to reverse peltier cooling to make a heater. Then I just needed a way to regulate the temperature. I needed a way to automatically turn it off if it gets too hot, and turn it back on if it gets too cool.

I found a thermostat that would work. It's the kind you might find on the wall to control your air conditioning or heat. It has an easy-to-read dial to set a temperature and show the current temperature. It's ridiculously large for this project, but it was on sale for only $2. I looked at the simplicity of the description and pictures on the box and incorrectly assumed it was an old school mechanical thermostat. It turned out to be a newer one, requiring a CR2450 battery plus 24 volts AC all the time.

It took some experimenting with power supplies to figure out how to get it to turn on and send signals. Then I needed to add a relay. I ordered one from Amazon, but it took longer to ship than I wanted. I finished all the other parts of mounting a project enclosure box, transformer, fuse, fan, and heat sink, then testing to make sure the thermostat measured temperatures accurately, and making sure the peltier produced heat well when run in reverse. 

I used metal strips to hold the project box onto the cooler. I also added a small board with red and green LEDs to show the status of whether the heater was on (not at correct temperature) or off (up to temperature).

I was very impatient for the relay shipment to arrive because I had finished everything else I could on this project.

Amazon Affiliate link for the relay: https://amzn.to/3qk6cpP

Finally, the relay arrived, and it took less than half an hour to install it. It worked perfectly. I haven't tested the dough proofer with dough yet, but we did use it to melt chocolate.

If you need a dough proofer, there are commercial solutions out there. Some ovens might even have a low temperature setting for this. There are probably easier ways to convert a cooler to a proofer, or at least with a smaller thermostat. But this project was good because it helped me learn about thermostats without having to spend much money.