Fridge/Freezer Alarm
Approx construction cost US$15
Many people have a sizeable amount of capital tied up in their deep-freeze. A long power cut or a failure of the freezer itself can lead to significant financial loss, not to mention the prospect of losing the delicious smoked trout from last summer’s fishing holiday. There are also accidents. If the lead on the freezer is a little too short, someone catching their foot in it by chance may drag the plug from the socket without noticing.
Usually, the disaster is not discovered until later, when it’s too late to do anything about it. Similar remarks apply to the contents of a refrigerator, though it may be more a matter of disappointment than loss when somebody (who was it?) leaves the door ajar and the chilled lemonade warms up on a summer’s day.
This simple alarm project circuit sits in the freezer and simply waits for the temperature to rise above a preset limit. Then it turns on a loud buzzer, one that is loud enough to be heard with the freezer door shut.
More details on this construction project can be found in the October 2000 issue of EPE Online, the world's first web-delivered electronics and computing hobbyist magazine.
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