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DiscoverCircuits.com
-- Hobby Corner
Last Updated on:
03/19/2008 06:54:11 AM |
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| Freezer Over-Temperature Alarm |
A typical freezer can contain hundreds of dollars with of food. If the device
becomes unplugged or if the door is left open too long, the food inside can quickly become spoiled. The hobby circuit below is a battery
powered alarm system, which is attached to the outside of the freezer using a couple strong magnets. Two small gage wires are fed from
the alarm box to a thermistor temperature sensor, mounted inside the freezer. The alarm beeper will be activated, whenever the
electronic circuit detects a freezer temperature warmer than 0 degrees C (32 F). The overall current is so low that the 9v battery
powering the device will last for many years
Click on Drawing to view PDF |
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