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Dave's Circuits
Circuits designed by David Johnson, P.E.

Master Category List - Dave's Circuits
Last Updated on: Tuesday, October 13, 2009 01:24 PM

Alarm Circuits    Freezer / Frost Alarms
 
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.

Click on Drawing Below to view PDF version of Schematic

Circuit Freezing Temperature Alarm Circuit designed by David A. Johnson, P.E. (July 7, 2006)

Alarm Circuits    Freezer / Frost Alarms
Master Schematic Category List - David A. Johnson, P.E.
 
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