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generating pulse

Discussion in 'Electronic Basics' started by prateek, Jun 23, 2006.

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  1. prateek

    prateek Guest

    I need about 5% duty cycle pulse of about 1 sec time period. A second
    pulse required should be of same characteristics but delayed by a
    duration by about the 'on' time of the second pulse. ie the first
    pulse should go on and then the secoond pulse should go on. Need a
    simple solution please
     
  2. Mochuelo

    Mochuelo Guest

    Cheapest is a microcontroller running on its internal RC oscillator,
    which you may have more or less calibrated.

    If you don't want to use microcontrollers, you can use a 1 Hz
    oscillator that feeds a monostable that generates 50 ms wide, high
    logic-level pulses. A second monostable is set to trigger on the
    high-to-low transitions of the first monostable's output, and also
    generates 50 ms wide, high logic-level pulses. You can do the whole
    thing with a 40106 (hex inverter with schmitt-trigger), three
    capacitors, three resistors and two diodes, as shown in the figure.

    http://80.35.195.131/ng/ng_20060623A01.png

    R1 & C1 such that period is 1 s.
    R2 & C2 such that A and B pulses are 50 ms wide.
    D1 can be 1N4148.

    Best,
     
  3. Tim Williams

    Tim Williams Guest

    So, you want:
    ___
    Trig ___| . . . (doesn't matter?)
    __________
    A ___| |________________ . . . (until next trigger)
    __________
    B ______________| |_____ . . .

    ???

    You can do that with two of these.
    http://webpages.charter.net/dawill/Images/One-shot Timer.gif
    Trig is the input. Connect Q' (Q bar) to Trig of the second one. Use Q
    from each for the "A" and "B" output above. Adjust Rt and Ct for one
    second.

    Tim
     
  4. ehsjr

    ehsjr Guest

    _ _ _ _
    | | | | | | | |
    -- -- --------------------- -- ---
    T 0 1 2 3 Repeat

    So you want T0-T1 = 50 mS, T1-T2 = 50mS,
    T0-Repeat = 1000 mS?

    Count to 20 in 50 mS steps (drive 4017's with
    a 555 running at 20 hZ, set the 4017 chain
    to reset at count 20). Use counter output 0 and
    2 for your pulses. Actually you can use any
    pair of counts such that there is one count
    between them, like 1 and 3, 2 and 4, 3 and 5, etc.

    Ed
     
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