Getting a false count on a PIC circuit driving cascaded 4029 and 4511

Discussion in 'The Projects Forum' started by MrsSTechnology, Feb 8, 2015.

  1. MrsSTechnology

    Thread Starter New Member

    Feb 8, 2015
    4
    1
    Really hope someone can help me!

    I have a GENIE PIC circuit that I am using to create an up/down counter for a scoreboard. Pretty simple program and all is working well except when the first pulse goes to the 4029s the second chip is also getting a pulse so the first output reads '11' instead of '01' on the 2 7 seg displays (common cathode). This then delays the second chips could so the 10s unit is 1 out throughout the count so '19, 10, 21...'

    I have tried a few configs including adding an OR Gate from the clock and carry out of the first chip to the enable of the second. It looks like the rising edge of that first pulse is the culprit.

    Has anyone else had this problem? Any solutions you can offer? I have studies the 4029 data sheet and am truly stumped.

    TIA!!
     
  2. ericgibbs

    AAC Fanatic!

    Jan 29, 2010
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    380
    hi,
    Look at this clip from the 4029 d/s for cascading devices.
    E
     
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  3. MrsSTechnology

    Thread Starter New Member

    Feb 8, 2015
    4
    1
    Hi Eric
    Thanks so much. I had tried that and found that I now get no cascading pulse at all with the OR gate. Am I missing something? (see updated attached)Wondering if it is a connection to the 4511?
    Any help is greatly appreciated. This has been a head scratcher for 2 weeks now :(
    L
     
  4. MrsSTechnology

    Thread Starter New Member

    Feb 8, 2015
    4
    1
    Also, I had found a thread that you did about 4 years ago that started out with someone having the same problem (which spiralled into a massive circuit using optical switches and the likes. Nightmare!) I noticed at the end of that thread that someone mentioned that the simulation software might be the problem. I would hope that four years later New Wave would have figured this out but perhaps not. I did everything you instructed (I think :oops:) and am getting the same outcome. I will breadboard the circuit and see if it has the same problem too.

    Thanks so much for your help. It is for a student of mine and I am so frustrated not being able to help him. I'm a bit of a rookie too.;)

    L
     
  5. absf

    Senior Member

    Dec 29, 2010
    1,492
    371
    I simulated the circuit in proteus and it works fine counting 0.... 19,20,21,22 .....even without the OR gate. May be the problem is in the simulator. Is this GENIE PIC a real hardware or just a simulation file?

    If I were to confirm this, I would try it out in real hardware. See my sim attached.

    Allen

    p/s I noticed the CO of the second 4029 is connected to Vdd. I think it should be left open.
    MRSTECHNOLOGY.PNG
     
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  6. ScottWang

    Moderator

    Aug 23, 2012
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    If the clk key is a push button then in the real world we have to considering the key debounce circuit.
     
  7. ericgibbs

    AAC Fanatic!

    Jan 29, 2010
    2,501
    380
    hi L,
    Lets know the results of your bread board test goes, it should work.
    Note: Scott's point about the de-bounce, its a must for an actual circuit build.

    E
     
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  8. MrsSTechnology

    Thread Starter New Member

    Feb 8, 2015
    4
    1
    Thanks for advice about debounce . Would I need it when the pic is driving the clock? The 4029 chips arrived today so hopefully we'll get it going in the next couple of days.
    I'll post some pics.
     
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  9. ScottWang

    Moderator

    Aug 23, 2012
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    If you using the pic to drive the clock then the debounce is no need, but if the pic has key to input then you will need the software debounce.
     
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