@▷ Automatic Fire Alarm Circuit Schematic Diagram | Diagram for Schematic

Automatic Fire Alarm Circuit Schematic Diagram

This circuit uses bulb lamp and LDR as the fire detector. Alarm will sound when there is any smoke detected by the sensor. On the normal condition, the light from the bulb will be completely catch by the LDR, this will cause low resistance on the LDR, and the current will flow through it. If a smoke block the light from the bulb, the LDR resistance will high and the voltage can not flow through LDR. Transistor will be on ON position, and IC1 will produce high voltage (5 V). The high voltage will activate IC2 (UM66). Output from IC2 will be amplified by IC3 (TDA2002). Output from IC3 will activate the speaker. D1 and D2 combination works to produce 3.5V voltage as an input to IC2.

Automatic Fire Alarm Schematic Diagram

Components :
Diode D1-D2 : 1N4007
Resistor R1 : 2.2 ohm
Resistor R2 : 220 ohm
Potentiometer R3-R4 : 100k ohm
IC1 volt regulator : 7805
IC2 tone generator : UM66
IC3 tone amplifier : TDA2002
Capacitor C1 : 470 uF
Capacitor C2 : 1000 uF
L1 : 9V bulb
Transistor Q1 : BC107
9V power supply/battery
SP1 tweeter speaker : 8 ohm

Estimated price : $3