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Problem encountered on building a 24 hr digital clock,only hours portion.Help needed

Discussion in 'Homework Help' started by coolkid, Jan 6, 2018.

  1. coolkid

    coolkid New Member

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    Still very new to this,I hope you guys will help me in this journey.I am tasked to create a 24hr clock using 74ls93 ic and im using 74ls47 bcd decoder and 7seg anode led.
    Image below shows what i have done so far,and i not sure why the numbers are liddat.Please help
     

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  2. atferrari

    atferrari Well-Known Member

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    Liddat?
     
  3. coolkid

    coolkid New Member

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    I mean i am not sure why the number are displayed like that.
     
  4. dave miyares

    Dave New Member

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  5. JimB

    JimB Super Moderator Most Helpful Member

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    Does this exist in real hardware, or is it just a simulation?

    I notice that you are running the clock at 1kHz, if this was real hardware your eye would see the LS digit as an 8, your eye is not fast enough to see the changes.

    If this is a simulation, the simulator software will display who knows what?

    I suggest that you slow the clock to 1 or 0.5 Hz and see what happens.

    JimB
     
  6. coolkid

    coolkid New Member

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    Thks for the tip,but after slowing the clock,the result is still the same,the numbers kept "jumping".
    i tried 1hz and 0.5 hz.(see the images attached)
     

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  7. coolkid

    coolkid New Member

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    Im trying to cascade a mod 2 and mod 12 counter to form a mod 24 counter that counts to 24 then resets to zero.(at least thats what i think im doing).
    i also need to add :
    Two push button (or pulse) switches .One of the pulse switch will function as the manual clock signal generator used for adjusting the start time

    . The second pulse switch will be used as a toggle switch to select either the manual clock pulse or the free running clock signal.

    An LED indicator is also required to light up whenever the manual (or adjust) mode is selected.
     
  8. dave miyares

    Dave New Member

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  9. Ian Rogers

    Ian Rogers User Extraordinaire Forum Supporter Most Helpful Member

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    You have the second nand pair connected to 2 only.... To count to twelve you need to feed the output of the first nand to the input of the second... As the second nand needs to see the 2 and the 10. The first nand needs to be connected to 2 and 4 ( 10)
     
    Last edited: Jan 7, 2018
  10. Ian Rogers

    Ian Rogers User Extraordinaire Forum Supporter Most Helpful Member

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    This one counts to 12
    upload_2018-1-7_9-37-44.png

    And this one counts to 24
    upload_2018-1-7_9-39-1.png

    When you build you will need resistors on the 7 segment displays...
     
  11. coolkid

    coolkid New Member

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    works fine now,thks for the help.Can i ask what the freq on the clk you used in your simulation?(your design).

    Also could you explain a bit more for this part,i want to learn,as i was amaze by how a little tweaking solved the problem.(i dint know what i was doing the whole time)

    And lastly ,It'll be great too if you can recommend some ideas to implement "set time mode" using pulse switches,i have the general idea how it should work,but i just dont know where to start or what to use.

     
  12. atferrari

    atferrari Well-Known Member

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    ???
     
  13. coolkid

    coolkid New Member

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    I am not sure what are you asking me
     
  14. Ian Rogers

    Ian Rogers User Extraordinaire Forum Supporter Most Helpful Member

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    1) frequency was 2hz ( just for testing )

    2) Your nand gate reset at 12.... decimal doesn't go to 12 only 9.. Set the reset at 10 and the thing counts up to nine and resets. The second has to look at 2 on the second register and 4 on the first... Then it resets when the total count hits 24..

    To set the time you will need to clock each manually .. Set a debounced switch... Ored with the clock input... When the switch is pressed the hours increment..
     
  15. coolkid

    coolkid New Member

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    Im pretty sure i am wrong on this one,i am trying to make use of two pulse switches(push switches),the first acting as the mode selection(between "free run" and "adjustment" mode),and the second acting as a manual clocking.(see attached image).I need the switches to latch,like a on-off switch,i found out that i need jk ff in order to do so.Also i want to add a led that will light when "adjustment" mode is on.
    Help and tips will be appreciated.
     

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  16. Ian Rogers

    Ian Rogers User Extraordinaire Forum Supporter Most Helpful Member

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    You still need an or gate... The clock is an output and so is the JK flipflop...( erm! Smell something!!)

    Most use the "Adjust Mode" button as a through switch If it isn't pressed nothing happens.
     
  17. coolkid

    coolkid New Member

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    These are the changes that i have made,the led still doesn't seems to work.However the switches are okay now,and im able to choose between 'free run' and 'adjust' mode just fine.
    However the numbers sometimes are laggy and jerks a lot,is there something still wrong? also could you explain more about the Adjust Mode" button being a through switch?
     

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  18. Ian Rogers

    Ian Rogers User Extraordinaire Forum Supporter Most Helpful Member

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    Led's upside down...
     
  19. coolkid

    coolkid New Member

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    hows this
     

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  20. coolkid

    coolkid New Member

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    Looks like it is finally working,it was the resistor fault.
     

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  21. Ian Rogers

    Ian Rogers User Extraordinaire Forum Supporter Most Helpful Member

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    Cool... I'm a bit busy, so I only get on now and then...

    I'm glad it works... ( Remember the LED current limiting resistors when you build it!! )
     
  22. Nicolas de PAOLI

    Nicolas de PAOLI New Member

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    Hello !

    Voici ma création, une horloge réveil multiplexée à base de 33 TTL IC.

    Translation: Here is my creation, a multiplexed clock based on 33 TTL ICs



    <Mod note: ETO is an English-speaking site. If you want to post, please first translate it to English. Thank you.>
     
    Last edited by a moderator: Feb 15, 2018
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