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how to generate a single pulse from a switch closure

Discussion in 'Electronic Basics' started by [email protected], Jan 16, 2009.

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  1. Guest

    if I close a switch (non momentary) how can I trigger a 555 by
    generating a single pulse?

    example: relay contacts close, debounce the closure, generate a pulse
    triggering a 555.
     
  2. Rich Webb

    Rich Webb Guest

    Basically, by with a capacitor on the trigger input so that the 555 is
    sensitive to edges, not levels. Google for "555 edge trigger" for
    examples.

    There are software packages (e.g.,
    <http://www.schematica.com/555_Timer_design/555_Timer_PRO.htm>) that
    could help as well.
     
  3. neon

    neon

    1,325
    0
    Oct 21, 2006
    What you describe is a monostable lm555. USE pin 2 to trigger once it fires another pulse doesn't reset it not until the set time expires. There are gabs of info on this timer.
     
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