Circuit to create a single pulse from switch independent of switch state or duration at that state.

Discussion in 'General Electronics Chat' started by MikeDav, Apr 19, 2016.

  1. MikeDav

    Thread Starter New Member

    Apr 19, 2016
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    0
    I need to be able to press and hold a down a push button switch and this send a single short pulse to trigger a 555 timer (monostable mode operation). Holding the push button must not keep the trigger input to the timer high. Any suggestions would be very much appreciated.
     
  2. ericgibbs

    Senior Member

    Jan 29, 2010
    2,499
    380
    hi Mike,
    Use an AC [capacitor] coupled Trigger to the 555 input.
    Do you follow OK.?
    E
    Image is an example.
     
  3. MikeDav

    Thread Starter New Member

    Apr 19, 2016
    2
    0
    Thanks for the reply and offer of help.

    Am I correct in assuming that by including the circuit to the left of the 555 in your circuit diagram...Q1, R3, R4, R5 , D1 and C3 and substituting the rocker switch for V2 will create a short pulse to the trigger input of the 555 when the state of the the rocker switch opens or closes?

    Regards

    Mike
     
  4. ericgibbs

    Senior Member

    Jan 29, 2010
    2,499
    380
    Last edited: Apr 19, 2016
  5. ericgibbs

    Senior Member

    Jan 29, 2010
    2,499
    380
    hi GT,
    If the 555 Trig is held low, the Output will be held high while the Trig is held low.

    Eric
     
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