Digital CD40110BE Up / Down Counter help needed

Discussion in 'The Projects Forum' started by smilem, Nov 7, 2010.

  1. smilem

    Thread Starter Active Member

    Jul 23, 2008
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    Hello, I'm trying to make a digital up / down counter.
    I got the idea from this site http://www3.telus.net/chemelec/Projects/Counter-UD/Counter-UD.htm

    I made a 5 digit counter, see attached PCB schematic, it is identical to the one shown on the site above but has 5 digits instead of 4. At least I thought so. Unfortunately it does not work as expected.

    The first digit does not count, it shows a zero.
    The counter resets to zeros OK with reset switch, so that part works.
    Counting mode is chosen correctly as if I connect ground to other IC pin 9 or 7 it counts on other 4 digits skipping the first.

    I think there is an error in my PCB schematic, please help me to find it.

    PS What is "Logic supply in this schematic" ?
    http://www3.telus.net/chemelec/Projects/Counter-UD/Counter-UD2.png

    I'm trying to count by shorting signal ground to UP/down sw1 pins, perhaps this is not how I should use this?
     
    Last edited: Nov 7, 2010
  2. SgtWookie

    Expert

    Jul 17, 2007
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    IC2 is different. You have pins 6,7,8 shorted together; Latch Enable, Clock Down, and Vss respectively. You may have blown IC1 due to Clock Down being shorted to ground.
     
  3. smilem

    Thread Starter Active Member

    Jul 23, 2008
    132
    0
    Thank you for quick reply,
    On my PCB IC2 pins 6,7,8 are not connected together. (that was just image typo, sorry.)

    IC2 is like IC1, pins 6 and 8 connected together and then connected to GND
    Pin 7 of IC2 is connected to pin 11 of IC1
     
    Last edited: Nov 7, 2010
  4. SgtWookie

    Expert

    Jul 17, 2007
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    Then I don't see any mistakes.

    Check your actual board for solder splashes/bridges, bad solder joints and wiring errors.
     
  5. smilem

    Thread Starter Active Member

    Jul 23, 2008
    132
    0
    It seems that misterious "Logic-supply", pull-up output needs to be connected to UP/DOWN switch middle pin.

    Then it works. With pin 9 it counts up, pin7 counts down.
    Should it work this way? I thought that I need to connect ground to pin 9 or pin 7 IC1 ?

    I have noticed that mechanical contact makes it count by tens of counts. How can I make it count by 1 ?

    I'm wanted to use a relay as this is what should be counted (connect - disconnect cycles). Would solid-state relay work?
     
    Last edited: Nov 8, 2010
  6. SgtWookie

    Expert

    Jul 17, 2007
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    A mechanical switch or relay has what is known as 'contact bounce' - there is a lot of making and breaking of the connection when an attempt to change the state is performed.

    Read up on debouncing here:
    http://www.ganssle.com/debouncing.htm
    It's a very good write-up. Anyone who is contemplating using mechanical switches or relays should read it.

    If you use a solid-state relay, you won't have to worry about "bounce".
     
  7. smilem

    Thread Starter Active Member

    Jul 23, 2008
    132
    0
    Thank you for the link. I have to use solid-state relay then.

    You did not answer the part about input signal.
    In the image below we see that IN is shown as GND and UP/DOWN switch.

    I could not make it work this way, the unused output on the image labeled "optional pull-up output" connected to UP/DOWN switch makes the counter count UP or DOWN depending to what position is the switch toggled.

    Any insights why? Nobody would make printed circuit board that did not work:confused:
    I tried to connect square wave output to same pins and GND that did not work too :(

    BTW The pins pin 9 or pin 7 IC1 have 0volts between them and GND.
     
  8. smilem

    Thread Starter Active Member

    Jul 23, 2008
    132
    0
    Here is my final schematic, had no time to finish it until now.
    I have everything soldered as shown. (wiring for all digits not shown)

    The problem I have is that first digit omits some numbers.

    When counting UP the first digit never shows 7.
    When counting DOWN the first digit count like 9, 7, 4 , 1

    I have tried changing the IC's second in first port etc. but it did not make any difference. Weird thing is that in second port the same IC counts fine.

    What can be the problem. When reset all IC's shows zeros.

    I'm beginning to think my IC's are faulty as there are no other components except few caps and resistors. And because all digits shows zeros when reset LEDs and their resistors are fine.
     
  9. SgtWookie

    Expert

    Jul 17, 2007
    22,182
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    Where is your schematic?

    You posted the board layout. The schematic must accompany the board layout. Otherwise, it takes too much time and effort to reverse-engineer what you have done.

    Don't expect many replies until you have posted both a schematic and a board layout together.
     
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