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: 768
Print version: Print version

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