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When Light Falls on LDR the Resistance of LDR start Decreasing and its low resistance make the Transistor 1 in to Conduction mode and Cut off the Second transistor but when no Light falling on LDR so it,s Resistance start increasing so transistor 1 stop conducting and now we all knows that current always chose the path where Resistance low so it turn on the second transistor Because the 1k ohm resistor is low resistance so thats why transitor 2 start conduction and Led,s Start glowing;


Components you needed :

DC 5V source ( use old Cellphone Charger )

Battery 3.5v Dc ( Like Mobile Phone Battery )

Two Transistors BC547

LDR Resistors 33k,1k,100 ohm

One Diode 1n4007

One switch Button for On off

Led,s Red + Three White Led Connect 100 or 470 ohm Resistor with Every led

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Bio: Electronicslovers started in July 2011 with the mission to produce ideas to student and engineer or hobbyist to learn electronics practically. Electronicslovers provides information by ... More »
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