Temperature Window switch by IC 741

This circuit, is basically a resistance ï¿½ sensing window switch, except that the ï¿½resistorï¿½ takes the form of an NTC thermistor and the circuit thus responds to temperature. TH1 must have a resistance in the range 500ohm - 9Kohm. RV1 is used to set half ï¿½ supply volts on the RV1 ï¿½ TH1 junction at the ï¿½meanï¿½ temperature

Part List

R1=4.7Kohm TH1=NTC thermistor 500ohm…..9Kohm Q2=BC214L
R2=2.2Kohm D1-2=1N4148 RL1=12V Relay >120ohm
RV1-2-3=10Kohm pot. D3=1N4001

Read more source:
http://users.otenet.gr/~athsam/temperature_window_switch.htm
Thank you.

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