AUDIO CIRCUITS BATTERY CHARGER 555 TIMER CIRCUITS DC DC CONVERTERS LED DRIVER MOTOR DRIVERS PINOUT POWER SUPPLIES RADIO CIRCUITS SENSORS VARIOUS CIRCUITS PCB DESIGN PROCESS .
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Smoke detector using 555 timer circuit
Smoke detector using 555 timer circuit
DC motor speed controller with 555 timer
Capacitive touch sensor using 555 timer circuit
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 light 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. The photo transistor and LED must be housed inside an enclosure with holes to allow entry of smoke.
Comments I have designed the circuit Permalink Submitted by Anonymous on Sat, 03/26/2016 - 12:06.
I have designed the circuit using PCB but when the buzzer is connected it automaticaly sounds without having any smoke. So, anyone please suggest about this. reply
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Audio circuits Battery charger 555 timer circuits DC DC Converters Led driver Motor drivers Pinout Power Supplies Radio Circuits Sensors Various circuits
