Help about building a Digital Clock

Discussion in 'The Projects Forum' started by zarabotkalesna, Dec 6, 2015.

  1. zarabotkalesna

    Thread Starter New Member

    Nov 22, 2015
    Hello everyone.

    I have intention to build a Digital Clock.
    I want to reduce the number of ICs on breadboard to the minimum.

    My first thought was to use 4026 counters because they have the BCD decoder integrated, but they count from 0 to 9 and I didn't find a way to reset them when count reaches 3, or 5 (if you know any method for resetting please tell me).

    Second thought, to use 6 x 74LS193 (or 4510) counters plus 6 x 74LS47 (or 4511) BCD to 7-Segment Display Decoders plus 4 x AND gates for resetting 4 counters. That's a huge number of ICs so I don't want to use that option.

    I also read that the NE555 is not very stable when it's used for large timing intervals, e.g. 1 minute or larger.
    So I thought it might be wise to remove the "seconds" from my circuit and use a LM555 as a timer providing 1 minute clock (F = 0,0167Hz). But I would still have 4 counters and 4 BCD decoders. So I don't know how to reduce more this number of ICs.

    I also don't want to use microcontrollers such as PIC or Arduino or others...

    What would you suggest me?


  2. ISB123

    Well-Known Member

    May 21, 2014
    You are going to have to ask Ahmed Mohamed, he is an expert when it comes to building digital clocks.

    If you are new to electronics I would advise against building a digital clock since its fairly advanced project.
    KJ6EAD likes this.
  3. spinnaker

    AAC Fanatic!

    Oct 29, 2009
  4. k7elp60

    Active Member

    Nov 4, 2008
    Here is a circuit for a 1Hz clock. If you are in the U.S I would be glad to send you the parts, as I have multiple of each part. 1hz.png
    There still are digital clock IC's available that have all the necessary counters, decoders etc.
    KJ6EAD likes this.
  5. Sensacell

    Well-Known Member

    Jun 19, 2012
    A 555 timer circuit will not provide an accurate enough time base for a clock- unless you are ok with gaining / losing 15 minutes a day?

    Most electronic clocks use:

    (1) 32.768 Khz clock crystal oscillator.
    (2) 50 / 60 Hz mains frequency as a time base.
    KJ6EAD likes this.
  6. KeepItSimpleStupid

    Well-Known Member

    Mar 4, 2014
    Look at that 19x series to figure which one is more appropriate. You only need the gates for the count to 5 and reset.

    24 hour is easier to do than 12 hr with AM/PM.

    You can always multiplex the digits.

    Don't forget leading zero blanking for a 12 hr clock.

    A power line timebase works. So, does something that uses a 32768 Hz crystal. The power line has very good long term accuracy.
  7. KJ6EAD

    Senior Member

    Apr 30, 2011
    Last edited: Dec 7, 2015
  8. zarabotkalesna

    Thread Starter New Member

    Nov 22, 2015
    Thank you all guys.

    I couldn't find that IC... can you please provide me a link or something?

  9. GopherT

    AAC Fanatic!

    Nov 23, 2012
    There is likely on in an ok digital clock already in your house or a nearby second hand store.
  10. AnalogKid

    Distinguished Member

    Aug 1, 2013
    First, you can surf for digital clock schematic and get tons of schematics to help you decide on chip technology/count/complexity.

    Please give us a little background. What is your intent for the project? you said no PIC and I totally support that, but it still leaves some options. All TTL / CMOS, a fully integrated clock chip, direct drive displays, multiplexed displays, power line reference clock, crystal oscillator...? Also, what is your skill set for designing and building electronic circuits? Will this be hand-wired on perf board or are you going for a pc board? Is a kit that is all TTL chips and a pc board out of the question?

    The more we know about the entirety of your project, the better the guidance will be.

  11. Picbuster


    Dec 2, 2013
    Building a clock for normal use is simple.
    Use a lm8705, fuse, 3 caps, 3 resistors, pic one, xtal and a display.

    When wanted I can supply schematic and basic program.
  12. hp1729

    Well-Known Member

    Nov 23, 2015
    Are chips like the MM5314 still available? Single chip clocks.
  13. zarabotkalesna

    Thread Starter New Member

    Nov 22, 2015
    Thanks to all.

    Can you please provide me schematic?