Upgrading a dorm fridge

I’m going to start by saying a big thanks to David Disney. Without his help this project would still only be a doc file on my desktop with ideas, notes and links.

After doing a good bit of research on the net and taking inspiration from a least a few sources I remembered to capture, I had an idea of what I wanted to do to upgrade my dorm fridge style fermenters by replacing the thermostat with an STC1000+. I also wanted to mount a computer fan inside based on some experiments I’d done monitoring temperature swings and duty cycles in a fridge with moving air and one without. I was completely uncomfortable trying this myself, but I’d talked to David in the past about how he had replaced a thermostat on a “broken” refrigerator so I knew who to ask. I rolled up to his workshop early Saturday morning and after I got over a super case of jealousy we started measuring, cutting, pulling wire, and repurposing my old STC1000+ project boxes.

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Template for STC1000+

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David using a Dremel tool and a cutoff wheel. Safety first and watch the sparks!

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We removed the old mechanical thermostat. I had previously removed the freezer tray and bent back the cold plate. I had also drilled a hole in the back as a drain and to allow me to route power lines in for a heat source.

While we had the STC out it was time to upgrade the firmware and solder in a lead to bring the 12v DC power out to run the fan. The red lead was soldered to one side of the diode and the blue lead to the last of those three pads (any would work).


I also wanted to install a double rocker switch that would let me kill power to either the hot or cold relays without having to kill power to the STC. This complicated the wiring a bit, but in the end I’m glad we built in that function.

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Almost there. We had to bring up a neutral leg (white wire middle back) since the simple thermostat that was in place before was only hot and ground. Pigtail powers the STC as well as the hot and cold side relays. I don’t have a heat source chosen yet (I don’t need it in the summer anyway) but I will wire that in later and update this page to reflect that part of the build.

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Here the fan is installed with a spacer and the wires have been contained in a cord wrap. Almost done.

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And I’m back in action! I even took the time to recalibrate the STC1000+. The new and improved fermenter has a single cord running out the back and just looks professional. I can’t thank David enough for taking the time to help me with this project. I would not have been able to make it look nearly as nice without his help (if I could have pulled it off at all).