BURGLAR ALARM USING IC TIMER 555/556 ELECTRONIC DIAGRAM circuit diagram of burglar alarm using IC timer 555/556 is functioned as an alarm to prevent thief entering your house. The alarm would produce loud sound when a thin wire connecting resistor R1 with IC pin no 4 is broken. Thin fiber is used as the wire. The thinner the wire, the more responsive the alarm. This circuit needs 5-15V power supply, buzzer is used as a speaker. Here is the circuit schematic : Parts list : Resistor R1 : 10k Resistor R2 : 68k Resistor R3 : 1k Polar capacitor C1 : 1uF/15 B Capacitor C2-C3 : 0.01uF IC Timer : NE555