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DiscoverCircuits.com -- Hobby Corner
Last Updated on:
Wednesday, June 02, 2021 06:28 AM
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LINK to Dave's circuit, but DO NOT COPY any files to your WEB
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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. This circuit turns on a beeper whenever the inside temperature of a freezer is
greater then zero degrees Centigrade. The circuit draws only a few microamps
from a 9 volt battery. It uses a glass bead thermistor accurate to 1
degree C.
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Click on Circuit Below to view PDF 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 |
