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Simple 555 timer circuit needed.

  1. Feb 9, 2007 #1
    Hi all, great forum here. Hope to learn a lot.

    I am looking for a sample LM555 circuit. In simple terms I am looking what I think to be a reverse of the monostable circuits I have seen.

    More or less I have a switch that needs to be held down for 1 sec before the circuit is active (pin 3 high on the LM555). Or is there another circuit? I think the 555 would do what I need, just need a sample circuit to bump me in the right direction.

    Reseting the circuit I think I can handle, but just need a simple circuit to get me there.

    Any help would be greatly appreciated.
  2. jcsd
  3. Feb 10, 2007 #2
    You could put a push button on the trigger pin to signal a start of a cycle.
  4. Feb 10, 2007 #3
    That is sort of what I a doing now. The switch needs to be held down for one second and then before pin 3 goes high.

    If that makes better sense.
  5. Feb 10, 2007 #4


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    You might want to check into the 556 chip. It's a dual 555 timer. See if you can use one to trigger the other after 3 seconds if the switch is still depressed.
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