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Flip Flop madness

Discussion in 'Electronic Basics' started by Glenn Ashmore, Feb 9, 2005.

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  1. Maybe I am working under a misconception but I have tried everything and
    can't seem to get this to work.

    The problem I am having is with the 4013. I can get it to work in the basic
    bi-stable mode by pulsing CLK and it latches fine until the next pulse but I
    want to use SET to bring Q high on stay latched until a RESET from the
    counter turns it off. Nothing I try will work. I am delivering a clean
    square 200ms pulse and Q stays high only as long as the pulse lasts. Do
    set and reset not latch the way CLK does? I have all the inputs on the
    second flip flop and CLK and DATA tied to low.

    Glenn Ashmore

    I'm building a 45' cutter in strip/composite. Watch my progress (or lack
    there of) at:
    Shameless Commercial Division:
  2. I seem to recall that the 4013 has active high set and
    reset inputs. The behavior you describe is what is
    supposed to occur when both are driven active at
    the same time. Are you sure you have the other
    forcing input inactive?

    For what its worth, I've seen the 4013 used in a
    number of different circuits and it does what the
    datasheet claims. So, if my above guess is not
    enough to do the trick, perhaps you could post
    more details of how you are driving it.
  3. Check the power pins. If the power pin isn't connected, it'll look like
    the thing is working because it'll get powered by the pulse. When the
    pulse goes away, it'll drop back to ground.

    Can you make it flip (or is that flop?) by triggering it manually?

    Robert Monsen

    "Your Highness, I have no need of this hypothesis."
    - Pierre Laplace (1749-1827), to Napoleon,
    on why his works on celestial mechanics make no mention of God.
  4. Figured it out. When all else fails, replace the chip.

  5. Bob Masta

    Bob Masta Guest

    I see you've figured it out already. But for what it's worth,
    I recall many times where 4013s wouldn't clock properly
    on a protoboard, even though the same circuit worked
    fine on a PC board. The common "fix" around the lab
    was to put a 10K resistor in series with the chip clock
    or data line. Nobody could ever determine exactly
    what was going on (think we only had 20 MHz scopes
    back then), but the assumption was that the protoboard
    inter-hole capacitance was causing mischief somewhere.
    The typical circuits were not at high clock rates, probably
    all under 100 kHz, and the problems existed even when
    we slowed the clock way down. 4013s with 10K resistors
    got to be a joke around the lab. Never seemed to have
    these problems with anything else.

    Best regards,

    Bob Masta

    D A Q A R T A
    Data AcQuisition And Real-Time Analysis
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