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Light circuit that flashes an LED once when a light is detected? Answered

I'm kinda a new to circuits and i would really like your help guys! I'm trying to create a circuit that flashes an LED once if light is detected. I also want it with a 2-3secs delay which means after the LED flashes once the circuit turns off for 2-3secs (even if light was detected after the led flashes it will not flash again until after 2-3secs). Can i use a 555 timer to do so...and if yes how is the setup.



Best Answer 4 years ago

Here is a dual 555 or single 556 circuit.
  • Adjust the pot for triggering on your light LDR
  • The first will oscillate pin 3 about every 2.5 seconds.
  • Each rise of that output fires the red LED for a fraction of a second.
  • This repeats until the light goes low.
  • It still will not let a re-light to the LDR to cause a red LED until 95% of the Time is delayed because of D1 keeping the Reset pin 4 High !

Oh yea .........
use any NPN transistor like the 2N2222 etc..
and the small C = .01uF

A deeper circuit allows the adjustment of the time out period.


4 years ago

To be  clear
  • light pulse ⇒led flashes for 1 second
  • light turns on ⇒ led flashes for 1 second ⇒ 2 seconds later the led flashes for 1 second add infinitum............
  • light turns on ⇒ led flashes for 1 second ⇒ light goes off ⇒ 2 seconds later the led flashes for 1 second..

Thanks for the reply,

Yes like you said if..

light turns on => LED flashes for 1sec => 5sec later if there is still light the LED will flash again if not it will not flash.