I'm trying to use a 555 and LDR. The idea will be like this when the LDR sense darkness and the darkness will remain for a long time. The Led should On and will remain on until the preferred time and it will not turn on unless the LDR will sense light and then dark again. Can I get these result by using an LDR for the input trigger and 555 for the delay timer? pls help.

 

Yeah, you can do that. It would probably be simpler to use a 555 connected to the the LDR and feed a second 555 that is the timer.

The first 555 converts the light signal into something digital.

 

exactly that's what im going to do sir, thank you for the reply.

 

exactly that's what im going to do sir, thank you for the reply.

A genuine comparator would produce the same result, and possibly give you more control over the sensitivity and hysteresis - when the LDR is right on the edge of switching