First thing to know is that the main component in detecting the fire is the 10 k thermistor. Everyone is aware that when anything catches fire, smoke is produced. Pin on 555 Timer Projects This project is available at: Fire alarm circuit diagram using ic 555 . Here this circuit is constructed to give alarm buzzer sound for four different timing intervals that is 5,10,15 and 30 minutes, so we can change the timing of this circuit easily as we want. Fire alarm using thermistor and ne555. A lot of electronic circuits using ne555 timer ic are already published here and this is just another one.here is the circuit diagram of a police siren… read more in 555 timer ic We often use astable multivibrator mode. V+ and gnd are connected to +5v and gnd respectively. In this circuit germanium diode play very important role in detecting the fire. This simple fire alarm circuit can be used as a indicator or warning circuit for excessive fire and temperature. Fire alarm circuit u...