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DiscoverCircuits.com -- Hobby Corner
Last Updated on:
Tuesday, November 29, 2011 08:14 PM
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Alarm Circuits
Freezer / Frost Alarms |
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Freezer Over-Temperature Alarm
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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. |
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| 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 |
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Click on Drawing Below to view PDF version of Schematic |
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Alarm Circuits
Freezer / Frost Alarms
Hobby Circuits'
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eMail David A.
Johnson, P.E. about this circuit |
