555 / 74LS107 Problems

Discussion in 'The Projects Forum' started by benjam47, Oct 4, 2013.

  1. benjam47

    Thread Starter New Member

    Oct 4, 2013
    2
    0
    Hi everyone,

    I am trying to use a 555 to drive a 74LS107 JK flip flop.

    I am using a 36k and 18k resistor, and a .1uf capicator. The 555 is producing the expected clock at a 75% duty cycle.

    However, the Q output of the 74LS107 is following the output of the clock, instead of only flipping on the negative edge. I have the J, K, and CLR lines all tied to positive.

    Pictures of the project and the scope are attached.

    I am a newbie at this, just trying out some projects for personal enjoyment, so I suspect I've done something dumb. But I have tried replacing chips, looking for wiring faults, and am now out of ideas.

    Thanks for any help!
     
  2. MrChips

    Moderator

    Oct 2, 2009
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  3. benjam47

    Thread Starter New Member

    Oct 4, 2013
    2
    0
  4. MrChips

    Moderator

    Oct 2, 2009
    12,442
    3,361
    Glad we can help.
    Next time get help fast from AAC.

    100μF across the supply might do the trick, but do put a 0.1μF capacitor across pins 1 and 8 of the 555 circuit!
     
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