CD4029 counter - How to change number without CLK?

Discussion in 'The Projects Forum' started by MrEARTHSHAcKER, Jul 3, 2013.


    Thread Starter New Member

    Jun 20, 2013
    Hello everyone,

    I have CD4029 binary/decade up/down counter connected on my breadboard with NE555, adjusted to count each 1s ( I'm making a stopwatch, that's why).

    I wish to connect a button, so I can adjust current number in the counter, by pressing on it.
    The idea that had come up to my mind was to connect a button between source and clock input, therefore whenever I pressed the button, it would send a positive ramp to CLK of CD4029 and force it make a change, i.e. count up/down by one.

    However, this doesn't work.
    I have never done anything similar, so I need your advice.
    By some kind of logic... shouldn't the counter make a change whenever I set its CLK to logical 1? Or does it exclusively needs a square pulse to trigger the change?

    Thank you.
  2. Dodgydave

    Distinguished Member

    Jun 22, 2012
    The counter will only count on a square wave it needs a change from low to high to low, datasheet page 5

    you can preset the outputs by using the Jam inputs , so you can start counting from say 5 by putting 5 on the jam inputs , set jam enable on start clocking and the turn of the jam enable continue clocking it will start at 5 then increment by 1 clock pulse 6,7,8 etc,,,
    Last edited: Jul 3, 2013

    Thread Starter New Member

    Jun 20, 2013
    Yeah, but that would require 4 switches and require that the user knows binary :D

    I am looking for the solution with one button. So... could it be possible to connect CLK by default to the ground and when you press the button the CLK input goes high and drops low again ( because the button is automatically released)?
  4. GopherT

    AAC Fanatic!

    Nov 23, 2012
    You can also buy rotary switches that encode 0-9 (on the dial) and output 0-9 in binary to four pins (plus ground) as output. The rotary switches get pricy but that is an option.
    Other option would be up/down arrow buttons and control input/setup time with microcontroller (but that microcontroller could also handle the full function of the CD4029 as well).
  5. absf

    Senior Member

    Dec 29, 2010
    I dont know how to do it with just one button, so I designed one with 3 buttons.
    UP = step up one count on the LED
    DOWN = step down one count.
    START/STOP = start/stop counting.

    The last time you press "UP", on "START/STOP", it would start counting up.
    When it reaching the max count, it would roll over and start from the minimum count until you press "start/stop".

    Though not elegant, it is just an example to trigger your imaginations. The chips used are

    U2 = 555
    U3 = 4023
    U4 = 4069
    U5 = 4013
    U6 = 4066
    U1 = 4029 of course.

  6. absf

    Senior Member

    Dec 29, 2010
    Just noticed that the U6 4066 funcction can be replaced with the spare 4023 gates.

    May be it's time for you to learn how to program a PIC....

  7. wayneh


    Sep 9, 2010
    I think you need the opposite, a pull-up resistor on the CLK so it is held high unless it receives a negative-going pulse from the 555 or from a manual pushbutton that connects it to ground. You might need to debounce the switch with yet another 555 to prevent the CLK from incrementing multiple times when the pushbutton is pressed. But it might work OK without denounce, maybe just use an RC as a low-pass to avoid multiple triggers.