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Freezing Temperature Alarm
This circuit turns on a beeper whenever the outside air temperature is
less than 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.
Freezer Over-Temperature Alarm This electronic hobby circuit below is designed to activate a
beeper alarm, whenever the outside air temperature is below 0 degrees C
(32F). A 9v battery powers the hobby circuit. The average 9ua
current is so low that the battery should last for many years....
