A Little help required!

wayneh

Joined Sep 9, 2010
17,496
The circuit works on the relative resistance of the LDR versus R3, which form a voltage divider. This impacts the voltage on the base of the transistor, via R2. When that voltage exceeds ~0.6V, the transistor starts to conduct and the LED lights up. R4 limits the current to prevent damage to the LED.

The circuit has some problems but probably works.
 
Top