Accidentally leaving a door open for a long time will ruin the contents of a freezer if nobody knows about it. This alarm will notify folks when the door has been left open for more than 10 minutes, and it will start beeping after 5 minutes. A motion sensor will restart the door timers when activated, as someone could spend >5 minutes loading the freezer. This alarm is designed to fit a double door commercial freezer.

There are 3 phases of the alarm

  1. Door(s) open <5 minutes - no action.
  2. Door(s) open >5 minutes with no motion - pre-alarm beeping.
  3. Door(s) open >10 minutes with no motion - beep more and email a notification.

The purpose of the pre-alarm beeping is to draw attention to the freezer so someone can close it before the alarm goes off.


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2 x Buzzer
5v breadboard friendly
2 x Magnetic contact switch
Door sensor, with mounting screws
1 x Header Kit for Feather
12-pin and 16-pin Female Header Set
1 x Hook-up Wire Spool Set
22AWG Solid Core - 6 x 25 ft
1 x 1 Ft Jumper Wires
Jumper wires
1 x Mounting Tape
Gorilla Glue Heavy Duty Mounting Tape
1 x USB-C cable


Soldering Iron
Wire Stripper/Cutter
3D Printer

This guide was first published on Oct 12, 2022. It was last updated on Oct 12, 2022.

This page (Overview) was last updated on Apr 28, 2022.

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