Invisible Intruder Alarm

                                     Invisible Intruder Alarm

Description: In this post we are giving the circuit of invisible alarm which is simple and also having large number of applications this can be used as Intruder alarm by fitting this in either sides of the door ie., Transmitter on one side and receiver on the other side whenever some one passes through that door the alarm will ring.

Working Procedure: The IR LED's present in the Transmitter will give out the Ir rays which are invisible human eyes but can be seen by watching through camera,these IR rays are continuously observed by the D4 which is an IR LED which senses the IR rays transmitted by the transmitter when the obstacle come in between the transmitter and receiver the IR rays will not reach the receiver thus the buzzer rings.

PARTS:
R1 : 68 ohm
R2 : 10M
R3 : 1K
R4 : 470 ohm
R5 : 4.7 K 
R6 : 4.7 k
R7 : 100 ohm

D1,D6 : 1N4001
D4 : IR ray sensing diode
D2,D3 : IR ray emitting diode
D5,D7 : LED's red and green
Q1,Q2 : 2N2222
SCR 
IC-1 : LM324

Micro Buzzer,
9V battery;s two

S1,S2 : On/Off switch

Note: if IR emitters and sensors are not available in the store ask for normal TV remote Led and It's sensor



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