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DIY freezer door alarm

August 12, 2010

I’ve twice not fully closed the freezer door recently. The trouble is; by the time the tiny red warning light comes on food has already started to defrost and once we didn’t spot the light for nearly 24 hours.

So I decided to make an audible alarm. Obtaining a battery, connector, buzzer and micro-switch was easy. Making an activator was less easy. You may have noticed that, when you first close a freezer door, the low pressure created inside as the air cools pulls the door in hard and squashes the rubber seal. Then it relaxes a millimetre or so. So the thing that operated the micro-switch couldn’t be a fixed object. Version 5 finally worked. The buzzer was a bit loud which is why it’s wrapped in some bubble-wrap in the box with the battery.

The main thing is; it works.

Oh, I know it looks ugly and primitive but the door opening and hardware are next to a wall and normally invisible. The photo was taken using a mirror held against the wall.

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