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When there is a fire breakout in the room the temperature increases. This simple ultra compact and low cost fire alarm circuit will senses the heat and activate the alarm.Transistor BC177 (Q1) is used as the fire sensor here. When the temperature increases the leakage current of this transistor also increases. The circuit is designed [...]

This is a fire alarm circuit diagram that using a thermistor and a timer IC 555. The circuit is as simple and straight forward so that, it can be easily implemented. The thermistor offers a low resistance at high temperature and high resistance at low temperature. This phenomenon is employed here for sensing the fire.The [...]