Synchronous Counters.

Discussion in 'The Projects Forum' started by jdouglasusn, Aug 7, 2012.

  1. jdouglasusn

    Thread Starter New Member

    Aug 7, 2012
    14
    0
    This circuit is suppose to spell out "CLUE" and repeat. I can get it to work great on multisim. But when I physically build the circuit. It doesn't work.

    It spits out a seemingly random "CLCECULECLECU" Those letters are in no particular order everytime. It's something different everytime other than "CLUECLUE..."

    I checked my wiring ALOT, over and over....then checked it over and over again.

    I swapped both 74LS76 IC's, samething. Swapped them again with another pair, samething.
    I swapped the 7 Seg display, samething.

    I moved the circuit to a different part of the breadboard, and alas, same thing again.

    I know the diagram is correct, and it works 100% on Multisim.

    Question about the Function Generator, too. I applied a 5V square wave, but it also goes to -5V below the 0V line. Would this be an issue? If so, how can I get a positive only 5V. Will I need a diode?
     
    Last edited: Aug 7, 2012
  2. Papabravo

    Expert

    Feb 24, 2006
    10,148
    1,791
    The 74LSxx chips will not be happy with below ground voltages and I'm surprised you didn't let any magic smoke out of them. RTFDS!
     
  3. absf

    Senior Member

    Dec 29, 2010
    1,493
    372
  4. jdouglasusn

    Thread Starter New Member

    Aug 7, 2012
    14
    0
    That is something to consider. Thanks a bunch.
    The generator wasn't liking the offset anyways, it wouldn't go far enough. I still had a negative peaks. I'll try the 555 timer. Thanks man. :)
     
  5. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    You MUST use bypass capacitors across Vcc and GND for the 555 timer. I suggest an 0.1uF poly metal film or ceramic cap, plus a 10uF or larger aluminum electrolytic cap.

    You should also have an 0.1uF cap across Vcc & GND of each and every 74xx IC.

    You need to keep your wiring short. If you have breadboarded it and have long, loopy jumpers, you need to make them as short and direct as you can. Long loopy jumpers will make them inductive, and you will have lots of "ringing" on the wiring. This will cause what seems to be random extra clocks in your circuit.
     
  6. jdouglasusn

    Thread Starter New Member

    Aug 7, 2012
    14
    0
    I did that, it had no change.
     
  7. jdouglasusn

    Thread Starter New Member

    Aug 7, 2012
    14
    0
    I was hopeful... but it didn't work. It didn't do anything.
     
  8. jdouglasusn

    Thread Starter New Member

    Aug 7, 2012
    14
    0
    The only thing that happened for for this was D2 lit up.

    Thanks for the help though :)
     
  9. jdouglasusn

    Thread Starter New Member

    Aug 7, 2012
    14
    0
    Did some tweeking....THANKS it all came together like a charm now :) thank you.:D
     
  10. absf

    Senior Member

    Dec 29, 2010
    1,493
    372
    Is this how your circuit looked like? I run it on proteus and it works.

    Allen
     
  11. jdouglasusn

    Thread Starter New Member

    Aug 7, 2012
    14
    0
    For the most part yes, the only difference is the values of a few components. Other than that, exactly the same. This circuit works on my simulator too. I also got it working on my board. Add to mess with a few things, though.
     
Loading...