Not homework, but a request: how to make a LED that blinks only once when powered

Discussion in 'Homework Help' started by crashingthisplane, May 10, 2015.

  1. crashingthisplane

    Thread Starter New Member

    Apr 30, 2015
    A friend asked me this because I am a EE student. But since I am pretty much, eh, below-average, I don't really know what to do except use a capacitor or something. Anyone? It should blink once when powered, then stay off til it gets switched off and then on again.
  2. DickCappels


    Aug 21, 2008
  3. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    Power supply? LED spec? Blink duration?
  4. crashingthisplane

    Thread Starter New Member

    Apr 30, 2015
    1 second blink, LED 1.3-1.6 v, power supply is 5v

    all of the above is a quote
  5. shteii01

    AAC Fanatic!

    Feb 19, 2010
    You can use 555 Timer in Monostable Mode, in this mode it is also called one shot pulse generator. The 555 timer will generate a single pulse that will turn led ON one time and that is it because the chip reset is never engaged (it is tied to the power supply) so the chip is never reset. The only way to reset the chip is to turn off the power. The use of 555 timer also allows you to control how long the led stays on. So using this chip will allow you to accomplish both of your goals, turn led on one time, set how long led stays on.

    555 Timer wiki:
  6. crutschow


    Mar 14, 2008
    If the time interval is not critical you could use a simple circuit consisting of a transistor, a capacitor, a diode, and a few resistors.
    Below is the simulation of such a circuit.
    You can change the value of R2 to vary the LED ON time.

    One-shot LED.gif
    Last edited: May 11, 2015