intruder alarm

Intruder Alarm



  Intruder alarm is very common project for diploma or basic level. Here, by dreamlover technology a verified project on intruder is published, used in door of your house for sound an alarm when anyone open or pushed the door. The circuit of intruder alarm can be used against thieves or intruders.

  The project intruder alarm consist two circuits each of transmitter and receiver separately. Transmitter section comprising a laser diode and power is given from a 9V power supply. Here the receiving section consists of LDR for sensor and work on principle of LDR. When light falling to LDR from laser diode provides base current to transistor T1 which start conducting (but not T2) and the alarm remains off.

  When door is pushed, light incident on the LDR is interrupted and it offer high resistance which stop conducting transistor T1 but transistor T2 receive base current and start conducting. The input is given to AND gate N1 from the emitter of transistor T2. Here IC2 work as latch when high output from AND gate N1 is connected to pin 1 and 14 respectively. High output form output pin 12 of IC2 is given to base of transistor T3 through R7 and it cause transistor conduction and consequent sounding of the alarm.

Parts List

Resistors (all ¼-watt, ± 5% Carbon)

R1, R2, R6, R8 = 1 KΩ

R3 = 2.2 KΩ

R4 = 10 KΩ

R5 = 100 Ω

R7 = 2.2 KΩ

Semiconductors

IC1 (N1) = 7408

IC2 = 7473 JK Flip-Flop

T1 = BEL187

T2, T3 = SL100

LED1, LED2 = RED

LD1 = Laser Diode

Miscellaneous

9V Battery

SW1, SW2 = On/Off Switch

SW3 = Push-to-On Switch

Piezo Buzzer

LDR