transistors as a darlington pair. The circuit is also using a thermistor to detect or sense the heat. A 12K variable resistor is used to adjust the activation of the buzzer on the desired temperature.
Working of the circuit is simple when the thermistor will sense temperature or heat its resistance will become lower due to which the transistors become switch on and activate the buzzer.  





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The schematic presented here is a project of a temperature alarm circuit or heat alarm circuit. The circuit will detect or sense the heat and activate a buzzer alarm. The circuit is very simple and using only five components. For increasing the sensitivity of the circuit we have connected the two BC547
 
Temperature Alarm Circuit Schematic