yes it goes off.

 

Now expose the LDR to dim light, i.e. halfway between light and dark when you want the LED to switch on/off.
Then start with a very high value base resistor >1MΩ and gradually reduce the value until the LED just turns on.
Using a variable 1MΩ resistor is a convenient way of doing this.
The value resistor when this happens is the final value you need in your circuit.

 

ohk will try it. Btw I found this one that I made for laser security alarm a year ago. It shares a common circuit (almost). Will this work if I replace buzzer and capacitor with LED's?

 

View attachment 74532 ohk will try it. Btw I found this one that I made for laser security alarm a year ago. It shares a common circuit (almost). Will this work if I replace buzzer and capacitor with LED's?

Yes, but don't forget to include the current limiting resistor in series with the LEDs.

 

The circuit in post #23 runs the risk of frying the transistor if the pot is inadvertently adjusted to its minimum resistance. Put a 1k resistor in series with the pot to avoid that.
You will probably need very bright light (or an LDR with a low dark-resistance) to get the transistor to switch off.

 

okkk. Thanks for the help everybody. I will try both the circuit and the way you all said.