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BCD Clock

Discussion in 'Electronic Design' started by demo, Jul 23, 2005.

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  1. demo

    demo Guest

    hi all,
    I`m trying to build a BCD clock using bcd counters but i`m having
    problems resetting the clock from 12:59 to 01:00; instead the clock
    restarts counting from zero 00:00 (hours and minutes) If anybody has an
    idea how to fix this please help!
  2. mmm

    mmm Guest

    You must reload the hours counter with 01 instead to reset the counter
    to fix, You must switch to a presettable counter if you are not using it
    a suitable part can be the CD4029 chip or 7416x ( x = 1,2,3,4) or
    similar part

    in alternative you can count like in Italy

    00:00 midnight

    00:00 again for half day

    and so on

    11:59 a minute before midnight

    and eventually add 1 ( one ) to hour digit before display
  3. Use military 24-hour time, running from 00:00 to 23:59.
  4. "demo" ...
    Are you a technical person? This is the change to amaze your friends!

    Just do the right thing and rollover to 00:00:00 after 23:59:59.
    And also display a (sortable) date format like 2005-07-23.

    Arie de Muynck
  5. keith

    keith Guest

    Others have already jumped on my fix (military time), so I'll suggest the
    hard way. Use a gate to detect 13 hours and do a parallel load of '1'.
    You will need a counter with a parallel load (direct set, or some such
    thing). I better way would be to detect twelve and use a counter with an
    enable (detect 59 minutes) and a synchronous load.
  6. Ben Bradley

    Ben Bradley Guest

    There must be a solution at <>.
  7. Chris Carlen

    Chris Carlen Guest

    You might have a reason to be using logic chips, but look into what
    microcontrollers can do for you. You can implement a very feature-rich
    clock using a micro, and change it any time and any way you want. To
    accomplish the same feature-richness with logic chips would be nearly
    impossible. The only other alternative, and one which you should also
    consider if this is more of an academic exercise, is to use a CPLD or
    FPGA. Then you can develop logic design skills instead of software
    skills, while avoiding the limitations of discrete logic chips.

    Good day!
  8. demo

    demo Guest

  9. Guest

    i`m having problems resetting the clock from 12:59 to 01:00; instead the clock
    The BCD clock at:

    Works like this:

    You get a falling edge at pin 1 of the hours counter which advances the
    counter to 13 hours. This produces a high level at pins 2 and 14 which
    resets the counter to 0.

    So you have that much working.

    The reset signal stays high for a few milliseconds determined by the RC
    at pin 11 of the inverter. Pin 12 of the next inverter will move high a
    short time after pin 10 moves low, which applies a high level to pin 1
    (clock input) of the counter. When pin 10 moves back high, pin 12 will
    move low a short time later applying a falling edge to the counter
    which advances it from zero to 1. So, it's now 1:00 PM instead of 0:00

    Should work with the right parts.

  10. The power went off today and the 'goofy clock' was happily reading out
    the 'fail' time and date, restore time and date, also for the last 2
    power failures. It stores 8 events. This is a microcontroller based
    device with maybe 1200 lines of assembly code. I also have a triple
    display version to do multiple time zones with 12/24 hour mode
    selectable for each zone. Are you doing a BCD clock as some sort of
    exercise to show it can be done? To prove a point? A class assignment?
    Dammit, I can do it?

    Chris Carlen is right about the feature rich possibilities of the
    microcontroller world. Next software revision of goofy will include a
    WWVB receiver from Galleon.

    I used to prefer hardware versions because they seemed simpler but the
    flexibility of microcontrollers is so great that I only use the
    hardware for things too fast for the controller, even then with PLDs,
    CPLDs, etc. A long time ago a friend pointed out that the only
    difference between hardware logic and the computer is the sequential
    nature and temporary storage of intermediate results. Reprogramming
    beats the the hell out of trace cuts.


    Always make NEW mistakes.
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