Timed puch button help

Discussion in 'The Projects Forum' started by nebelr, Sep 17, 2008.

  1. nebelr

    Thread Starter New Member

    Sep 17, 2008
    I am trying to build a circuit that when a push button is pushed a relay(1) is activated and held closed then X seconds later another relay is activated for a split second and then X seconds later relay(1) returns to open. It seems simple but i just need help with what components to use and how arrange them. any help would be appreciated.
  2. RiJoRI

    Well-Known Member

    Aug 15, 2007
    I'd use either a small microcontroller, or a couple of 555s. A ULN2003 would drive the relays. I would experiment with the output of the first 555 driving pin #4 of the second 555. ("Experiment" == "I'm not sure about this. It may or may not work.")

  3. mik3

    Senior Member

    Feb 4, 2008
    You can do it with three 555 or a 556 and a 555. The one of the three 555 will be used to turn on relay 1 for X secs you want. The second 555 will be triggered at the same moment as the first 555 and will produce the delay needed for relay 2 to turn on. Also, the output of the second 555 will drive pin 2 of the third 555 and not relay 2. Relay 2 will be driven by the third 555. After you trigger the first and second 555, the second will output a high at pin 2 of the third 555 so its output is low. After a while the second 555 will drive its output low and the third 555 will trigger producing the small pulse you want for relay 2. Finally, after X secs relay 1 will turn off.