From the MAKE Flickr pool:
Flickr user P^2 – Paul created this fridge controller run by a Teensy:
This is a microcontroller-powered temperature controller for a fridge I built out of fabricated necessity and spare parts last weekend.
Backstory: We replaced our ancient 2nd fridge with a big new upright freezer, which left our little chest freezer empty. Sometimes we do need the extra fridge space though during harvest season at the farm, so I figured I could just turn the temperature up on that old chest freezer and turn it into a fridge. Nope. Highest it goes is -4C.
6 thoughts on “Teensy fridge controller”
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I hacked together something similar. Mine went the Arduino + SSR + one wire temperature sensor route. I ran until the Johnson Controls A419 arrived.
The A419 are like $60 and built for exactly this sort of application.
If you stick with your own controller. Code in a lock-out timer to avoid burning up your compressor. Also change the freezer thermostat to the coldest setting – you want the micro-controller in complete control.
Something like the powerswitch tail in the maker shed might be a good replacement for the hacked timer surge strip.
The old chest freezer with external temp controller is typically used for beer brewing. One nice thing about converting a chest freezer to refrigeration is that it is very efficient because the cold air doesn’t fall out every time you open the door.
As SKR said, there’s a long tradition of this in homebrewing. Besides getting an efficient refrigerator without having to buy a new one, you also extend the lifespan of the appliance by years. A freezer that can no longer keep up with full-power use can idle along at refrigerator temperatures for a very long time.