Synchronous Counters.

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?

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!

Instead of using your troubled function generator, why not just make a simple LM555 timer circuit to generate 1 Hz pulses for your circuit clock input? LM555 is easy to use and would not give -5V on the ouput.

http://forum.allaboutcircuits.com/showpost.php?p=117640&postcount=5

Allen

absf said:

Instead of using your troubled function generator, why not just make a simple LM555 timer circuit to generate 1 Hz pulses for your circuit clock input? LM555 is easy to use and would not give -5V on the ouput.

http://forum.allaboutcircuits.com/showpost.php?p=117640&postcount=5

Allen

Click to expand...

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.

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.

SgtWookie said:

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.

Click to expand...

I did that, it had no change.

absf said:

Instead of using your troubled function generator, why not just make a simple LM555 timer circuit to generate 1 Hz pulses for your circuit clock input? LM555 is easy to use and would not give -5V on the ouput.

http://forum.allaboutcircuits.com/showpost.php?p=117640&postcount=5

Allen

Click to expand...

I was hopeful... but it didn't work. It didn't do anything.

absf said:

Instead of using your troubled function generator, why not just make a simple LM555 timer circuit to generate 1 Hz pulses for your circuit clock input? LM555 is easy to use and would not give -5V on the ouput.

http://forum.allaboutcircuits.com/showpost.php?p=117640&postcount=5

Allen

Click to expand...

The only thing that happened for for this was D2 lit up.

Thanks for the help though

jdouglasusn said:

I was hopeful... but it didn't work. It didn't do anything.

Click to expand...

Did some tweeking....THANKS it all came together like a charm now thank you.

Is this how your circuit looked like? I run it on proteus and it works.

Allen

absf said:

Is this how your circuit looked like? I run it on proteus and it works.

Allen

Click to expand...

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.