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Operation of 3-minutes Digital Counter

Discussion in 'Homework Help' started by Wjs, Jun 9, 2016.

  1. Wjs

    Wjs New Member

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    Hi,

    When I simulation this only one display working.

    What goes wrong or the gate i used wrong.

    Please advise.
     

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  2. mvs sarma

    mvs sarma Well-Known Member

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    try with RBO pulled UP
     
  3. Wjs

    Wjs New Member

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    what you mean.
     
  4. dave

    Dave New Member

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  5. mvs sarma

    mvs sarma Well-Known Member

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    please download and see the function table of 74LS247 and the note 3 below the tables. People believe that unused pin is High, but need not always be.

    Hence the condition needed sappers to be RBO pin to be pulled UP . You might use 1K resistor for that.
     
  6. Ian Rogers

    Ian Rogers Super Moderator Most Helpful Member

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    I just sim'd the exact circuit.... It worked fine... The only difference is I didn't use the R/C on the PL line and I used a digital clock input...
     
  7. mvs sarma

    mvs sarma Well-Known Member

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    Fine Ian Rogers,
    for some reason the OP did get only 1 digit.
    i suggested him to add pull up on 74LS247 "rbo' pin.
    the truth table shows like that and He need not leave them open, i suppose.
     

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    Last edited: Jun 10, 2016
  8. Wjs

    Wjs New Member

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    I tried but still same only one display is counting another two display not counting. are the gate issues ?
     
  9. mvs sarma

    mvs sarma Well-Known Member

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    Can you perform Lamp Test(LT) checking how to do from the datasheet for the respective digits that refused to glow?

    possibilities are that displays either faulty or model changed , unless the number tallies. you could sawap the LS247 chips one by one to the working display to check their performance.
    Later restore to original locations and try swapping the display devices.
    I assuem that you are working on Breadboard.
     
  10. Wjs

    Wjs New Member

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    breadboard it work but in circuit maker it doesn't work
     
  11. mvs sarma

    mvs sarma Well-Known Member

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    i see
    once it works on breadboard, forget it
    the simulators might have their own deficiencies.
    all the best
     
  12. JoeJester

    JoeJester Active Member

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    When you breadboarded it, did it count past 59 without advancing the minute digit to 1 the first time you fired it up?

    If you built it like you drew it, it will.
     

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