Digital Clock/Calendar

Discussion in 'The Projects Forum' started by nismospecv, Apr 28, 2007.

  1. nismospecv

    Thread Starter Member

    Mar 14, 2007
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    I'm going to be making a digital clock/calendar using seven segment displays. I'm pretty sure on how to build the clock part, but I'm getting confused as to where to start when making the calendar.

    For the calendar, I would like to display day, month, year(figuring leap years also), hour, and minutes. I will not be worried about seconds so I can save some seven segment displays.

    Any direction would be much appreciated.
     
  2. recca02

    Senior Member

    Apr 2, 2007
    1,211
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    i can only try to give you some idea here.
    first try using multiplexer to save no of displays required thus saving no of 7 seg requird. this way any req quantity can be viewed as per selection signal.

    secondly,
    u might have figured it out to increment day counter using hrs counter as i/p.
    now u wud need to associate four month lengths i:e 28,29,30,31
    with different months. this u can do by designing ckt where using respective month number with lengths in logic ckt such that the month counter sets the max no of days that the day counter will reset after reaching. for
    feb u will have to add the year factor to it.
    the additional day for the feb month will be added for every four year increment in a pre set count of say 2000 which will generate a bit that wud
    help in setting 29 for second month.
    year can be incremented by month counter.also month counter must be reset after 12 counts.
    presetting the counter to existing date wud require another set of circuitory that sets each counter ff to the req bit.

    another easy method wud be to use micro controller and make a programme
    for it ,i have no idea abt microcontroller but i know programming wud be lot easier.
     
  3. hgmjr

    Moderator

    Jan 28, 2005
    9,030
    214
    I agree with those who recommend the use of a microcontroller as the basis for this project.

    To tackle this project using discrete logic, while possible, would be a more challenging effort.

    hgmjr
     
  4. Retiredguy

    Member

    Feb 24, 2007
    28
    5
    I would sugest using a "real time clock" where all the counting would be done inside a single chip and takes care of the months and years internally. Epson makes a number of these chips and when you figure the cost of the numerous chips it would take to build your project from gates and counters, you would most likely be ahead to purchase one which would be about 6 t0 7 bucks. If you want to go this way, I would recomend a RTC72421 which has seperate DATA and ADDRESS lines. I know this would work since I built something similar without using a micro-controler. If you need help give me a yell.
     
  5. cumesoftware

    Senior Member

    Apr 27, 2007
    1,330
    10
    You could use a pic, a single 7-segment decoder and control each digit at a time using transistors to do that. You will only need 4 pins for the BCD encoded output (for all digits) and 3 pins that are linked to a binary/natural decoder (a 3 to 7 decoder) to drive each digit at a time in a fast sequence. You can drive up to eight digits. You can expand it to 16 digits (4pins+4pins) by using two decoders with additional logic (a not gate linked to the /enable or /chip_select of the first decoder)
    A microcontroller would control all digits easily with the least number of pins possible (only 8 pins). 16 digits are more than enough for a clock and a calendar (4 digits for the clock and 6 to 8 digits for the calendar).
     
  6. mozikluv

    AAC Fanatic!

    Jan 22, 2004
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  7. nismospecv

    Thread Starter Member

    Mar 14, 2007
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    You have a P.M.
     
  8. Salgat

    Active Member

    Dec 23, 2006
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    I do not reccomend using a microcontroller or a single chip that does the clock for you. Having just built a digital clock using bare bones logic gates, I can firmly state that building all of the discrete gates yourself is a great way to learn, you can't learn from plopping in one chip and having it to do everything for you. Its not that you want to just achieve a clock, but also want to learn something from it all. If however you just want to skip all that and miss out on some great learning experience, by all means go for the easier ways.
     
  9. recca02

    Senior Member

    Apr 2, 2007
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    i concur with Salagat,
    though its not that using microcontroller will be super easy and one wont learn anything , but it wud really be worth it to come up with a logic ckt for it at
    least on paper.
     
  10. cumesoftware

    Senior Member

    Apr 27, 2007
    1,330
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    What you are sugesting is very difficult even for an experienced user. Complicating things it is one way for the project never to be done. What you are sugesting is impratical, unless you wan't him to give up.
     
  11. mozikluv

    AAC Fanatic!

    Jan 22, 2004
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    i believe all your suggestions has been well taken, however it's still up to the guy on what road to take. he may go for the discrete way or go straight to a single chip and his choice will entirely depend on how deep is his knowledge. but based on his rsponse i believe he will go for the suggestion of "retired guy"

    moz
     
  12. nismospecv

    Thread Starter Member

    Mar 14, 2007
    10
    0
    Well guys, I'm still learning logic. And I just am not sure how comfortable I am to do it the discrete way. It's definitely not that I don't want to learn though.
     
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