JK Flip-Flop binary counter using 555 as clock

Discussion in 'The Projects Forum' started by CaptainPrice, Sep 30, 2011.

  1. CaptainPrice

    Thread Starter Active Member

    Aug 12, 2009
    49
    0
    Im trying to make a binary counter. "ripple through" counter

    I'm using a 555 chip to make a square wave. however when the output of the 555 is fed to the first Flip-Flop it doesnt appear to do anything. [ as opposed to when i manually touch the F-F to GND]
    I'm using SN54LS73A JK master slave flip-flop. its negative edge triggered.
    I want to use 3 bits so it cycles between 0to7 on the output.

    Right now, I have all J&Ks connects to positive. and Q feeding clk2 and q2 feeding clk3. LED outputs are q1,q2,q3 correct?
    The output right now appears random, but does cycle a bit(not completely in binary order) when i manually use a wire to momentary put clk1 to ground.

    Any idea how i can get this thing working right?



    Datasheets
    http://www.datasheetcatalog.org/datasheets/208/338045_DS.pdf
    http://www.taydaelectronics.com/datasheets/A-032.pdf

    555 connected like so
    http://www.ohmslawcalculator.com/555_astable.php
    R1=1k
    R2=12k
    C=220uf

    Trying to connect flip flops like this
    http://www.wisc-online.com/objects/ViewObject.aspx?ID=DIG4203
     
  2. #12

    Expert

    Nov 30, 2010
    16,283
    6,795
    You did an excellent job of showing us the instructions, and they are good. You must show what you did for us to find the mistake. Got camera?
     
    CaptainPrice likes this.
  3. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    Make the 555 go slow, say 1 hz or less. You can use a simple probe using something like this to see what the logic is doing...

    [​IMG]

    Be sure all the inputs are connected to the correct logic levels, don't leave them floating. You will note the worksheet you are referencing to shows them at a logic 1. Be sure all the inputs are covered, such as set and reset.
     
    CaptainPrice likes this.
  4. CaptainPrice

    Thread Starter Active Member

    Aug 12, 2009
    49
    0
    Haha!!
    I had left the Clear pins floating, I connected them to Positive, and now it works!!

    now to go make it more complicated....
     
Loading...