smoke detector device | Electronic Schematic Diagram https://electronicscheme.net Schematic Diagram & PCB Design Thu, 24 Nov 2016 11:55:00 +0000 en-US hourly 1 https://i0.wp.com/electronicscheme.net/wp-content/uploads/2017/05/cropped-transparent_text_effect.png?fit=32%2C32&ssl=1 smoke detector device | Electronic Schematic Diagram https://electronicscheme.net 32 32 129969089 Simple Smoke Alarm using Photo Interrupter Module https://electronicscheme.net/simple-smoke-alarm-photo-interrupter-module/?utm_source=rss&utm_medium=rss&utm_campaign=simple-smoke-alarm-photo-interrupter-module https://electronicscheme.net/simple-smoke-alarm-photo-interrupter-module/#respond Thu, 24 Nov 2016 11:07:07 +0000 http://electronicscheme.net/?p=3972 This is a really simple smoke alarm circuit design. The circuit consists of two important modules that are sensor module using a photo interrupter module […]

The post Simple Smoke Alarm using Photo Interrupter Module first appeared on Electronic Schematic Diagram.]]> Really Simple Smoke Alarm Circuit
This is a really simple smoke alarm circuit design. The circuit consists of two important modules that are sensor module using a photo interrupter module and alarm module using a tone generator IC NE555 with astable multivibrator configuration and then connected to the speaker, so you can hear the alarm sound.

How the Simple Smoke Alarm Works

If no smoke presence around the device, 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.

Photo Interrupter Module Configuration
Photo Interrupter Module Configuration

However, 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 pin 4 (reset) of IC 555 goes high to activate the alarm.

Take a note that this simple smoke alarm must be housed inside an enclosure with holes to allow the smoke to enter the box.

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