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One second PAUSE in 18 Stage LED Sequencer?

Discussion in 'Electronic Basics' started by locator299, Feb 13, 2006.

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  1. locator299

    locator299 Guest

    I was looking at Bill Bowden's 18 Stage LED Sequencer circuit at:

    (using cascaded 4017 decade counters) and I had a question about its
    operation - actually, about the SMOOTHNESS of its operation.

    It looks like we would have a smooth blink rate from LED 1 through LED
    9, a pause during second #10, then, starting at second #11, LEDs 10
    through 18 would light up.

    Is that correct or am I looking at this wrong?

    I was trying to find a circuit that would give me:
    1. A smooth 16 LED sequence blink rate,
    2. For one 16 LED one-way sequence,
    3. And then STOP after the 16th LED was done.

    Will Bill Bowden' s circuit do that - or does anyone know a better


  2. Deefoo

    Deefoo Guest

    There is indeed a very small pause during second 10, but it is (way) less
    than a microsec (I haven't looked up the 4017 datasheet). The main clock
    advances the right counter which activates pin 11. When this pin goes high
    it enables the clock for the left counter. If at this moment the clock is
    still active (high) the left counter will (almost) immediately see a rising
    edge on its clock input and advance one step. So there will be no visible
    pause if the clock high-time is a bit longer than the propagation delay of
    the right counter (from clock to pin 11). In Bill Bowden's circuit this
    condition is largely met.

    For your application you could use pin 9 of the left counter to block the
    clock by connecting it through a diode to pin 2 of the 555 (anode to pin 9).
    This will stop the oscillator. To get things going again you could toggle
    the power or add a reset switch (4017 pins 15 to gnd).

  3. John Fields

    John Fields Guest

  4. Deefoo

    Deefoo Guest

    The OP said "STOP after the 16th LED was done" so I suppose this means off.

  5. John Fields

    John Fields Guest

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