Chest freezer temperature controller

[Mikey Sklar] finds himself in need of a temperature regulated refrigerator for fermenting foods like yogurt, kimchi, bread, and beer. After some testing he found that by building his own controller he can get a chest freezer to outperform an upright refrigerator at this task by 2-to-1.

The controller is based around an ATmega48. It includes a remote temperature sensors which you can see connected to the lower left header in the image above. On the back of the board there’s a relay used to switch the freezer’s power on and off. [Mikey] is selling a kit but the hardware and software for the project are both open source so build it yourself if you have the know-how.

A chest freezer is a great place to store Cornelius kegs… we’ll keep our eyes open for one.


  1. JB says:

    nice Mikey! Good seeing your project posted here!

  2. PanicOpticon says:
  3. pcmofo says:

    I made a temp controller for a chest freezer for my kegerator. I made it with all analog components, comparators etc. It was cool and it was like 5-10$ in parts. But it requires a separate power source for the DC.

    I finally just bought a LOVE temperature controller, and wired it into the chest freezer. Now I have two chest freezers that I can reprogram and also displays the temp, they both run on AC input so you really only need 3 wires, Hot in, hot switched out, and neutral to both power the temp controller and switch on the compressor. Also, these cost about $50, the same price as this is being sold for….

  4. Kevin Lura says:

    Has this same mod been done several times on Hackaday?

  5. Dominic says:

    Nice. I was looking into buying a pid temperature controller off of ebay to do sous vide cooking.

  6. Scott says:

    I’d hope that they program a compressor-start delay in to keep the compressor from burning out.

  7. ss says:

    This is very cool. With winter coming it would be awesome to have a controller like this, but with a tweak to open a vent if the air outside is cooler than the room air. That way it would really cut down on the electricity needed. The controller would still be able to kick the fridge on if it got warm out again.

  8. John says:

    I Believe a chest freezer has an advantage of holding temps because the cold air does not escape like an upright does when opening the door.

  9. Rectifier says:

    Built something like this to keep my corny kegs cold too. Yes, a compressor delay is essential to avoid smoking your freezer (learned the hard way when my freezer kept stalling – fortunately it survived). There’s no need to use outdoor air, as cool as that sounds – chest freezers are extremely efficient, and even more so when running low temp differentials as a fridge.

    Only problem was, my chest freezer did not like being a fridge – humidity constantly built up in it for some reason and it was always swampy – since I like to keep my beer around 5C, the sides and bottom (submerged in 2″ of water after a month) always grew mold, despite regular applications of bleach. Gross.

  10. cgmark says:

    I would use the ds1620 chip . It does everything needed on one 8 pin chip, programmable and all you have to add is a relay, transistor to switch the relay and a diode to protect the output. Total about $10 for all the parts.

  11. Johnathon says:

    I have no hacking experience at all but am getting married in the UK next year in the middle of a field Glastonbury style. I’m trying to find a solution to keep all of the beers and wines cold that doesn’t involve paying for tons of ice.

    This looks to me as though it would be a great solution so:

    1) does this sound suitable for my event and is it reliable?
    2) are there many UK hackers visit this site who may help?

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