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Temperature Alarms
Last Updated on:
Monday, April 16, 2012 07:59 AM |
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Circuits Designed by Dave Johnson, P.E. : |
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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.
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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....
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- MICRO
POWER OVER-TEMPERATURE ALARM
The circuit is powered for years by a single 3 volt lithium battery. It sounds
an alarm when the temperature exceeds a certain point. With some minor changes the
circuit could also be configured for an under temperature (freeze) alarm. The
circuit uses a cheap but accurate thermistor as the temperature sensor.
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Links to electronic circuits,
electronic schematics, designs for engineers, hobbyists, students & inventors:
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| Temperature Alarms |
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