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This series of high temperature, serves to warn us about the increase in temperature, a temperature sensor which is used thermistor (TH1), the normal temperature of approximately 25 ° C the resistance of the thermistor approximately 10 K and at increased temperature reaches 94 ° C thermistor will resistant to change until they reach of about 1 K, the existence of this value changes that would enable Darlington Q1 and Q2 to drive the relay which is connected to the alarm. Power supply 9 VDC using the voltage, this circuit can be used to control the fire.

Part List R1= 820 ohm D1= 5.6V 0.5W Zener K1= 6V 200 ohm Relay R2-3= 1Kohm D2-3= 1N4148 BZ1= Buzzer C1= 220uF 16V Q1-2= BC 550C S1= 1×2 Switch TR1= 2.2Kohm Trimmer TH1= Thermistor 10Kohm at 25° C BATT= Battery 9V or external supply