Title:
Fire alert systems for homes, hospitals, other buildings.
Circuit Diagram:
Component list:
- 1 Photo interrupter module
- 2.Speaker 8 ohms 1 w
- Ic 555
- Capacitor c1 – 0.04 uf , c2 0.01 uf, c3 100 uf 25 v
- Resistor r1 = 470 ohms,r2 = 4.7k, r3 = 1k ,r4 = 47k
- Variable resistor vr1 1k.
- Wires for connection
Description:
This is a simple fire alert
project. This project activates alarm when smoke is detected. Here smoke is
detected by photo interrupter module (at bottom left of circuit).
The photo interrupter module
consists of an LED and a Photo transistor. The light coming from the led falls
directly on the photo transistor, this makes the collector terminal to go
ground potential and activates the reset control of 555 timer. If there is an
interrupt on the path of LED and Photo transistor such as smoke, the light does not reach the photo-transistor, causing the collector voltage approximately equal
to supply voltage which is supplied directly to the reset pin of IC 555, which
is wired as astable multivibrator. The high voltage at this pin enables the IC
and it produce square waves continuously, which in turn drives the speaker
through a coupling capacitor.Thus alert sound is generated.
Applications:
This system can be used in places
where fire alert is required. Places like homes, hospitals, banks.