Frost Alarm
Notes:
The thermistor used has a resistance of 15k at 25 degrees and 45k at 0 degrees
celsius. A suitable bead type thermistor is found in the Maplin catalogue. The
100k pot allows this circuit to trigger over a wide range of temperatures. A
slight amount of hysteresis is provided by inclusion of the 270k resistor. This
prevents relay chatter when temperature is near the switching threshold of this
circuit.
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Title: Frost Alarm
electronic circuit
Source: www.electronics-lab.com
Published on: 2005-02-10
Reads: 767
Print version: 
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