Fire alarm circuit

The utility model discloses a fire alarm circuit, including NPN triode Q1, thermistor R1, LED lamp D1, resistance R2, resistance R3, electric capacity C1, electric capacity C2, 555 timer U1, NPN triode Q2, buzzer LS. The utility model provides a simple structure, fire alarm circuit with low costs utilize 555 timers to constitute multivibrator, and draw forth the asynchronous clear terminal of 4 pins and meet thermistor R1, when the conflagration takes place, also be exactly that thermistor R1 reduces when the temperature risees, 4 pins be the high level this moment, and LED lamp D1 shines just that multivibrator starts working, exports the square wave, and it is vocal to drive the buzzer, reaches the warning effect. If the not happening conflagration, on the contrary then, D1 is dark for the LED lamp, and the buzzer is not sounded.