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replace triggering with switching

Discussion in 'General Electronics Discussion' started by waynebonnici, Nov 19, 2014.

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  1. waynebonnici


    Sep 25, 2014
    Hello there. I have this combined circuit using both monostable and astable modes of the NE555. The problem is that monostable works by triggering the push-to-make switch and NOT on switching it. If I just keep pressing the switch it obviously doesn't stop counting. How can I make this circuit work when the first IC is switched on AND the switch is not just triggered?:(

    Attached Files:

  2. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    Nov 28, 2011
    I'm not sure what you're asking. Do you want the first 555 to trigger when you first press the switch, but not remain triggered while the switch is held down? If so, you can modify the trigger circuit like this:
    (image found on the net somewhere...)

    Keep the rest of your circuit the same; just copy the part of that circuit between the pushbutton and pin 2.

    This is not an ideal solution because the 555 may retrigger when the pushbutton is released, due to contact bounce.

    Also the rest of your circuit is not ideal; you can probably avoid the relay and make other improvements. If you can describe clearly exactly what the circuit needs to do, I (or someone else) can design an improved circuit for you.
    waynebonnici likes this.
  3. waynebonnici


    Sep 25, 2014
    Thanks :)
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