Smoke detector using 555 timer circuit


Posted on Feb 5, 2014

This smoke detector is designed using 555 timer circuit and some common electronic components. The photo interrupter module is used as the smoke detector, while timer 555 is wired in astable configuration as an AF oscillator for sounding alarm via a loudspeaker. In the absence of any smoke, the gap of photo interrupter module is clear and the ligh


Smoke detector using 555 timer circuit
Click here to download the full size of the above Circuit.

t from LED falls on the phototransistor through the slot. As a result, the collector of phototransistor is pulled towards ground. This causes reset pin 4 of IC 555 to go low. Accordingly, the timer is reset and hence the alarm does not sound. When smoke is present in the gap of the photo interrupter module, the light beam from LED to the phototransistor is obstructed. As a result, the phototransistor stops conducting and pin4 (reset) of IC 555 goes high to activate the alarm.




Leave Comment

characters left:

Related Circuits

  • New Circuits

    .

     


    Popular Circuits

    Single Supply RS232 Interface for Bipolar AD converters
    simple and cheap dark detecting led
    preamp
    Long Delay TimerCircuit
    ELECTRONIC COMBINATION LOCK
    Light control circuit diagram
    Frequency sensitive rheostat manually start reversing circuit



    Top