I am attempting to send a signal triggered by a LDR that reads a light that will be on for 2-12 seconds then off for 2-8 seconds, with the goal of a short signal each time the light comes on. I built the normal light detection circuit using the LDR, resistors and a BC547 transistor and it functions as it should with a signal when the light is on. But I need the signal to be a short (.5 sec. or so) burst, which means a timer (I think). I ordered some 555 timers, but can't wrap my head around getting it to send a short signal with a long trigger (everything I read says the 555 out stays high with the trigger) then resetting until the next trigger. Or is there an easier way to do this without a timer?