How to combine an LDR (Light Sensor Circuit) to an LED Driver using 555 Timer?

[PamieBeverly]

Can someone help me how do I do a circuit that has a blinking LED operated by 555 timer but only triggers when light is sensed. I know I have to use an LDR but how do I combine this with LED driver if it also uses 555 timer? Please reply as soon as possible. Thank you.

 

[ericgibbs]

hi P,
What is the specification of the LDR, ie: light/dark resistance.?
Also the Blink rate required and LED type.

E

 

[large_ghostman]

Blast Eric got there first!! Grr.

Ermmm welcome to the forum BTW

 

[AnalogKid]

One way to do this is to first design the 555 oscillator and LED driver and get that going. Then add a small circuit that connects the LDR to the 555 Reset pin. If you are using a CMOS 555 (LMC555, etc.) it might be as simple as a resistor from Reset to Vcc and the LDR from Reset to GND. The 555 Reset input has a reputation for being a bit strange, but there is no harm in trying this simple way first; it may not work, but it will not damage the 555.

ak