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Help needed on designing a circuit for a digital clock (A level project)

Discussion in 'Electronic Projects Design/Ideas/Reviews' started by MutantNoodles, Feb 28, 2010.

  1. MutantNoodles

    MutantNoodles New Member

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    like this?
     

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  2. Hero999

    Hero999 Banned

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    No.

    Look at the datasheet for the ICs and note which pins go to the power supply.

    Hint: the capacitor is short circuited how you've shown it.
     
  3. MutantNoodles

    MutantNoodles New Member

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    okay, but sorry i dont get what you mean by putting it accross?:confused:
     
  4. dave

    Dave New Member

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  5. Hero999

    Hero999 Banned

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    I mean to connect the capacitor from one power rail to the other, from positive to 0V.
     
  6. MutantNoodles

    MutantNoodles New Member

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    like this? just roughly.
    But the reset of the first ic is connected to the ground pin, so wont the capacitor reset the ic?
     

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  7. Hero999

    Hero999 Banned

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    That's it, you got there, in the end.

    Now you can research why the capacitors are required, because if you're doing a course which is worth its salt, then it's the kind of question you'll be asked in the exam.
     
  8. MutantNoodles

    MutantNoodles New Member

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    actually, i am doing a product design course, which doesn't involv any electronics, but i decided to do a project with electronics for extra credit. But ill research it so i have a better understanding :).
     
  9. MutantNoodles

    MutantNoodles New Member

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    this is the minute circuit layout i made
    is that what you mean by a capacitor across? only one?
    and on the first ic, the circuit diagram that mbarazeen put up, the reset is attached to the 0V pin of the ic, wouldnt that reset the chip? or is that that the purpose?
    could you reply asap please, its urgent.



    edit*
    ive just realised the first ic power pins are connected to the wrong rails
     

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    Last edited: Apr 22, 2010
  10. Hero999

    Hero999 Banned

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    Each IC should have a capacitor across its supply rails.

    The reset pin is activated by a logic high so no.

    All unused inputs should be connected to either high or low.
     
  11. MutantNoodles

    MutantNoodles New Member

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    here is the final circuit layout.
    I have looked over it and all the connections are correct.
    I am just asking if the connections i did with the unused pins to the ground rail are correct?
    and if the circuit would work.
     

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  12. MutantNoodles

    MutantNoodles New Member

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    ohh wait, should i have only connected unused inputs?
    not the outputs.
     
  13. Hero999

    Hero999 Banned

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    Yes, all unused inputs should go to 0V.

    Don't connect an output to a supply rail because you could destry the IC.

    You should be able to get rid of most of those ugly jumper wires by routing the PCB more carefully; connecting wires are not good and should be avoided wherever possible.

    To ensure propper etching, it's good practise to chamfer all 90° corners.
     
  14. MutantNoodles

    MutantNoodles New Member

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    i did all that.
    is this it?
     

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  15. Hero999

    Hero999 Banned

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    Another jumper can be eliminated, possibly even more but I've not looked that hard.

    Ideally the supply decoupling capacitors should be nearer the ICs, as close as possible.

    As many corners should be removed as possible.
     

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  16. mbarazeen

    mbarazeen Member

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    MutantNoodles,

    you need a small correction on the diagram i posted, its a mistake, to make divide by 12,000..the pin connections are wrong.
    all should be shifted by one down on the diagram, ie:
    the out puts 7,5,4,14,13,15 &2 has to be connected to AND gates. on the circuit it has been connected to 5,4,6,13,15,1,3 its wrong.
    (Pin 3 is 15th bit out put and when it goes hight the ocunter resets. i confused this point before.)

    about PCB layout, you can rotate and shift ICs so get short paths to make a good look, also the out puts of 4060 can be connected to any of the inputs of AND gate, so change the connections to minimize jumpers. if possible i will post you an example how it can be.

    Edit: see the PCB for an example with corrected circuit, you can follow your own style to improve your self.
     

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  17. MutantNoodles

    MutantNoodles New Member

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    are you sure that circuit is correct?
    i have to make the circuit and finish it by tommorow.
     
  18. MutantNoodles

    MutantNoodles New Member

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    for example, on the and gates, why are two of the 3rd input pins connected together?
    please reply asap its urgent
     

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  19. MutantNoodles

    MutantNoodles New Member

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    and also where do i connect the voltage (5v & 0v) wires to?
     
  20. MutantNoodles

    MutantNoodles New Member

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    When you say outputs do you mean pins, or outputs?
    because when you say outputs 7 5 and 4, like you did in the diagram, thats the pins, and the outputs are Q4, Q5, Q6.
    ?
     
  21. mbarazeen

    mbarazeen Member

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    hopefully the circuit will work, the IC i selected for AND gate is 74HC11, see the datasheet, if you want to use 4073 then you have to make a minor change. on PCB rouite.
    ( swipe track to pin 8 & 9, connect 10 & 11, pin 14 of 4060 connect it to pin 12 of 4073)

    for power supply, give the input across capacitor C1.
     

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