3 pulse trigger

Discussion in 'The Projects Forum' started by sfaizan77, Mar 12, 2015.

  1. sfaizan77

    Thread Starter New Member

    Mar 12, 2015
    Hi , I want to use 555 timer to operate a relay when input is applied. I can generate pulses of 1 sec each but i want it to stop after generating 3 pulses even if input is available. Any help is appreciated.
  2. R!f@@

    AAC Fanatic!

    Apr 2, 2009
    Welcome to AAC

    For this you would need a pulse counter
    I do not think a simple 555 could do this. But then again there may be someone who could do this.
  3. blocco a spirale

    AAC Fanatic!

    Jun 18, 2008
    You could use another 555 to inhibit the pulse generating 555 after the time for 3 pulses has elapsed.
  4. Dodgydave

    Distinguished Member

    Jun 22, 2012
  5. Reloadron

    Active Member

    Jan 15, 2015
    I am not sure what you are asking? You could for example configure a 4017 decade counter / divider to count to N and halt where N=3 and for each pulse (3 pulses) the 555 is triggered with a 1 sec out pulse (one shot) or on the third pulse the 555 triggers as a one shot giving a pulse out. Then a manual reset? Can you explain exactly what you want?

  6. sfaizan77

    Thread Starter New Member

    Mar 12, 2015
    Thanks @Dodgydave .. seems what I was looking for. I have a contactor relay from which I will trigger the timer to generate 1 sec pulse astable mode. Then 4017 decade counter Q4 to pic 4 (reset) so that it remains high till the ckt starts again. Means contactor goes NO and then NC again to generate 3 pulses again. In my scenario contactor is using manual button. I have to generate 3 pulses whenever somene push the contactor start button no matter how long. It seems this will work for me.
    Dodgydave likes this.
  7. KL7AJ

    Senior Member

    Nov 4, 2008
    An old school solution is to use an integrator and a comparator. Each time a pulse comes through, it will charge up the integrator to a certain voltage, which can then trip a comparator. If your pulses are all the same duty cycle and rep rate, this works great...if not.....not so great.
  8. sfaizan77

    Thread Starter New Member

    Mar 12, 2015
    Yes it may work, But Dodgydave solution works best. I tested on Yenka Simulator its working gr8, besides it give me option from 1 to 9 pulses that I want to generate. Very simple circuit.
    Dodgydave likes this.