Smoke Detector Circuit using 555 Timer with Working Operation

Here is a simple smoke detector circuit using a 555 timer. This circuit is used to notice smoke and generate an alarm when the air is polluted. The circuit uses a 555 timer and sensor and the sensor module activates the oscillator and produces an alarm through the loudspeaker.

The photo interrupter module comprises a phototransistor and an LED. The light which is generated from the light-emitting diode falls onto the phototransistor, this creates the collector terminal to go potential of the ground and triggers the reset control of the IC 555 timer.
If there is an intrude on the track of LED and Phototransistor as smoke, the light emitted from the LED doesn’t reach the transistor, producing the collector voltage around equal to the supply voltage. It is directly fed to the RST (reset) pin of IC NE555, which is wired as an astable multivibrator.

The high voltage at the reset pin allows the IC and it generates square waves continuously, which in turn pushes the speaker through a coupling capacitor. Here the astable multivibrator is designed as an AF oscillator with 379Hz frequency and also a loudspeaker is used to hear the alarm.

Applications of Smoke Detectors
Smoke detectors are suggested for common use as they give the maximum level of protection. These devices can be used in leakage routes to offer sufficient early warning to let the clearing of residents.

There are two kinds of smoke detectors namely ionization and optical that are familiar as well general-purpose detectors and they are accessible in both analogs addressable and conventional.

Ionization smoke detectors are highly sensitive to burn quickly and flaming fires that generate small smoke particles. These detectors are used widely for workshop printings, paint stores, paper mills and also used for general purpose