Methods to generate a single low pulse ?

Discussion in 'General Electronics Chat' started by Externet, Dec 14, 2008.

  1. Externet

    Thread Starter AAC Fanatic!

    Nov 29, 2005
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    A pulse generating circuit senses a DC level increasing from 0V to 5V in about a minute.
    When the voltage is increasing and crosses 3V, a momentary low pulse of ~100ms (from +5 to gnd) is desired. --------_---------

    A comparator with a capacitive output could do it; can you suggest other methods ?
     
  2. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    As you say you can use a comparator to detect the change over 3 Volts.
    This signal can trigger a monostable multivibrator like the cd4047, to make the pulse.

    Greetings,
    Bertus
     
  3. Externet

    Thread Starter AAC Fanatic!

    Nov 29, 2005
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    Thanks.
    Yes, am using a window comparator but the window is detected also when the voltage returns to low, not only when increases.
    Miguel
     
  4. SgtWookie

    Expert

    Jul 17, 2007
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    When it's triggered on the falling edge, the output will have a positive pulse instead of the negative pulse. You can use a diode to clamp the positive pulse.
     
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