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Visitor Alarm Circuit Diagram Using IC 555




Description

                  Figure shows the circuit diagram of the 'Visitor Alarm' . Here I have used a LDR and a mono stable Multi Vibrator for making this circuit . When who breaking the LED ray, the LDR has high resistance so the transistor will be OFF and the pin number two of the IC 555 is negative then the IC 555 will be triggering so the output is ON. When who don't breaking the LED ray, the LDR has low resistance so the transistor will be ON and the pin number two of the IC 555 is positive after that the IC 555 doesn't triggering so the output is OFF.

Circuit Idea



Making Of LDR and LED

           Cover both items with a black insulation tape. See the below images for further details.

LED
LDR



Arrangement Of LDR and LED




Parts List 

Component No:Value
R110K
R210K
R3680R
R410K
C110MF
C2103pF
Q1BC548
D1White LED Or LASER

LDR
U1NE555
B16V Buzzer

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