Quick n' Dirty Freezer Door Alarm

My freezer will now text me when the door stays open too long.

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My fridge tends to work it's way up against the wall, and the freezer door will occasionally get stuck just before closing all the way. Food melts. It's a bummer.

I rigged up an alarm system using an ESP-32, a reed switch, a magnet, and a LiPo - all of which I had sitting around, fortunately. The magnet attaches to the freezer door, and the reed switch + ESP-32 sit across from it on the roof of the fridge. The ESP-32 wakes up every few minutes to check the switch. If it detects an open switch on two consecutive checks, it assumes the freezer has been open for more than a few minutes. It then connects to WiFi and triggers a notification!

With a wake-up period of 120 seconds, a 400mah battery lasts a bit more than 3 weeks. Eventually I'd like to set up a low battery alert as well.

Full instructional video below!

  • 1 × ESP-32 "Lolin-32" board with built in battery connector / charging circuit. Any web-connected board will do.
  • 1 × Reed Switch
  • 1 × Magnet Inductors, Chokes, Coils and Magnetics / Fixed Inductors, Chokes and Coils
  • 1 × Lipo Battery I used the 400mah "Ideal for Feather" battery from Adafruit. Fit nicely.

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Dan Maloney wrote 11/16/2020 at 23:16 point

Quick and dirty, I love tactical projects like this.

My freezer problem is a little different -- freezer is in the garage, and if the compressor fails or the breaker trips, I'll never find out about it until hundreds of dollars of food are spoiled. I might try something like this, but with a temperature probe instead. Plus a door-open switch that texts every time someone opens the freezer, just as a "positive control" that the whole system is working. Think I've got everything I need to make that happen right now.

Thanks for the inspiration!

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Guy Dupont wrote 11/17/2020 at 02:34 point

Thanks, Dan! I dig the temperature probe idea. Now I'm kinda curious how quickly the internally temp actually goes down.  Also - "Think I've got everything I need to make that happen right now." - isn't that the best? I've only recently gotten into this territory.

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