Gadget Love: The Johnson Temperature Controller

UPDATE May 25, 2016: Eventually the copper wire on this device broke. I think a more durable version of this gadget might be this one. And the gasket on the Scandinavian fridge, sadly, proved un-repairable due to the design of the door.

A friend of mine gave me a chest freezer recently and I augmented it with a handy gizmo, a Johnson temperature controller. The temperature controller allows me to run the freezer at any temperature between 30 and 80ºF. It works by cycling on and off the power to the freezer as needed. You just stick the copper probe in the freezer and adjust the dial to the desired temperature. So far I’ve thought of the following uses:

  • Proof bread overnight at 54ºF. I used to proof my dough in my refrigerator, but the chest freezer, running at this higher temperature thanks to the temperature controller, results in a more active proofing.
  • Make lagers (which ferment at low temperatures).
  • Make ales in hot weather. The house gets too hot to make beer in the summertime. Now I can make a batch or two without having to worry about the weather.
  • Use the chest freezer as a backup when I need to repair the gasket on our Scandinavian refrigerator YET AGAIN!

Not wanting to be a profligate energy user I only use the chest freezer periodically.

Now if only I could lower the temperature of the whole house which, thanks to the first heatwave of the summer, is now warm enough to make yogurt!

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  1. Would weather stripping work for the fridge? Or can you check other fridge manufacturers to see if they sell parts that might be jury rigged to work with your fridge?

    When our washing machine broke we were able to diagnose and repair it using a site called Repair Clinic. They also sell parts. I would check them out, they have really helpful videos:

  2. Hey Mikey,

    I saw your controller on your website and was very excited about it. The possibility of doing sous vide cooking and yogurt making at higher temperatures with your controller is a great idea. I’d encourage anyone reading this post to check out your website.

    And Sara,

    After many calls to gasket fabricators I determined that my best option is to glue in strips of old bicycle tubing. I’m pretty angry about the way this fridge is made–you can’t replace the gasket without replacing the whole door. And . . . they don’t make the door anymore. If they still did make the door it would cost more than the fridge is now worth.

  3. If you are handy, you can make your own digital temperature controller with the STC-1000 Aquarium controller from ebay for $19-$25. Like this one:
    (Not my auction, just the first on a search that had many. This one is good because it has a lot of clear information about the STC-1000).

    Heating and cooling. I wired up one in a plastic box with an outlet on the back. I use it for my beer fermenting chest freezer:

    I have an aquarium heater on the heat outlet. It sits in a gallon jar of water or in a water bath with the beer carboy.

  4. Yea I put together my own digital temp controller from parts I bought of e-bay mainly high temp stuff for melting metal, you can get controllers that can “predict” how fast temps will change so the actual temp is always within a couple tenths of a degree of the target temp its called a “pid” controller, coupled with a solid stat relay your good to go for any wattage/voltage (depends on the relay).

  5. turn it into a kimchi refrigerator…. i didn’t know proofing bread is done at 54 degrees, can’t you just make a mini cellar or bury it than?

  6. I’ve heard from a beer geek friend that turning a freezer into a refrigerator, as such, can be hard on the motor and condenser… any substance to this argument?

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