4017 cascade problem...?

Discussion in 'General Electronics Chat' started by noddyspuncture, Dec 4, 2015.

  1. noddyspuncture

    Thread Starter New Member

    Jan 15, 2014
    22
    0
    Hi folks,

    I was wondering if anyone could help me please?
    I have built this 4017 decade counter circuit (below) and seem to be having a few problems....

    I am hoping to trigger some percussion modules with it (if it lights LED's it can trigger the modules...) so the timing needs to be *steady*.
    And I can move the "reset" - pin11 (Q9) of the last 4017 to any LED output to change the count, and it all works, but...

    My problem is that when I attach it to say, pin4 of the second 4017 - to get a count of 10 then, if if this is an example of a steady count:
    1-2-3-4-5-6-7-8-9-10 .... what I am actually getting is: 12-3-4-5-6-7-8-9---10

    So basically '1' is quick... and '9' hangs a while (during the change over to the second 4017...?)
    I can see this really clearly on the LED's so no doubt I shall also hear it when it is triggering...!

    Is this normal or should it be seamless...? Would anyone have any ideas please...?
    All my wiring and soldering seems fine and has been quadruple checked.
    If it is normal I shall need to go back to the drawing board...;(

    Cheers for any help...
    Tom



    4017_sequencer.png
     
  2. nerdegutta

    Moderator

    Dec 15, 2009
    2,515
    785
  3. AnalogKid

    Distinguished Member

    Aug 1, 2013
    4,515
    1,246
    The 4011 is a NAND gate, not an AND gate, so your clock signals to stages 2 and 3 are inverted with respect to the clock for stage 1. That extra 1/2 width clock cycle is the cause of the blink you are seeing. The circuit linked above uses two diodes and a resistor to form a true AND gate at stages 2 and 3. Or use a 4081 gate.

    ak
     
  4. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    5,773
    1,103
    Another solution is to drive all clock inputs directly and use the NAND gate as a simple inverter between the Q9 output of one counter and the CE pin of the next counter.
     
  5. nerdegutta

    Moderator

    Dec 15, 2009
    2,515
    785
    This is me thinking out loud:
    The circuitry around the 555-ic looks odd. Why aren't pin 4 and pin 7 connected to anything? And pin 5 connected to VSS with a 0.01uF cap?
    Are the LEDs resistors high enough? (Supply Vs - LED Vf) / I) = (12-3.2)/0.02 = 440R

    Now it doesn't say what type of LEDs he has.

    How much current can a CD4017 source? 15mA?

    I'm sure this doesn't have anything to do with his problem, but still...?
     
  6. dl324

    Distinguished Member

    Mar 30, 2015
    3,234
    619
    Are you using a NAND or AND for clock gating? The datasheet shows AND.

    The timer configuration seems strange. You have the timing resistors tied to the output; I won't bother trying to analyze the timer because it has to be a mistake. Could you label the timer pins for those of us who don't use it often enough to memorize them?
     
  7. noddyspuncture

    Thread Starter New Member

    Jan 15, 2014
    22
    0
    Thank you so much everyone...!
    I replaced the 4011 in my circuit with the diodes and the other extra components and it all looks to be working exactly as I need now..!

    I have still only run it up to 10 steps but all the anomalies which were there before have now been cleared up so I'll assume taking it to 24 steps will also be good..!

    Again, many thanks for helping me with this...;)
    Cheers,
    Tom
     
  8. AnalogKid

    Distinguished Member

    Aug 1, 2013
    4,515
    1,246
    nerd and dl -

    The 555 is configured as a symmetrical squarewave oscillator. The output provides both the source and sink current for the timing resistor. Fewer parts. easier math, almost a perfectly 50% duty cycle. The output pulls the timing resistor low to discharge the timing cap, which is why there is no connection to the discharge output pin 7.

    ak
     
    nerdegutta and dl324 like this.
  9. dl324

    Distinguished Member

    Mar 30, 2015
    3,234
    619
    Thanks. I like it when I learn something new...
     
  10. noddyspuncture

    Thread Starter New Member

    Jan 15, 2014
    22
    0
    Hello again,

    I was really hoping that I had sorted this... when I got it working the other day I ditched the 4011 for the discrete diodes/resistors in the diagram suggested by nerdegutta. I quickly "Christmas tree" assembled it and worked - I checked each stage, I had only wired up 10 LED's - to make sure that it cycled all the different counts cleanly. I then proceeded to transfer the "Christmas tree" to the actual Veroboard.

    After finishing the circuit I've been getting really strange symptoms. It works apart from these points:

    If I reset on the 10th step... it cycles 2 > 9.... missing out LED1...!
    If I reset on the 6th step.... it cycles to step 5 and then just stops and stays on 5... no matter what.
    If I reset on the 4th step.... it cycles to step 3 and it stops and stays on 3 - however, if I put my fingers across LED1 it then cycles 1-2-3 as it should...!

    Would anyone have any ideas please...? I even reversed my tidy build and recreated the "Christmas tree" but it stays the same.
    I've swapped out the 4017's as well... still the same.

    I have only wired in 10 LED's so far... as I thought it would make sense to sort this before progressing any further.
    Starting to do my head in... :)

    Cheers,
    Tom
     
  11. eetech00

    Active Member

    Jun 8, 2013
    647
    110
    Hi

    How do you change the counts? Are you using a switch? Can you post the current version of the complete circuit?
     
  12. noddyspuncture

    Thread Starter New Member

    Jan 15, 2014
    22
    0
    :)
    This is the circuit... and I am using the "reduce count" input and tying that point to the relevant number LED output.
    Cheers,
    Tom


    4017_sequencer_2.GIF
     
  13. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    5,773
    1,103
    :confused: To do what?
     
  14. noddyspuncture

    Thread Starter New Member

    Jan 15, 2014
    22
    0
    To vary the amount of LED's it cycles though..!?
    If you connect say, LED 8's feed to it then it should cycle through 7 LED's...?
     
  15. eetech00

    Active Member

    Jun 8, 2013
    647
    110
    At what point in the output circuit are you making the connection to the reduce count input?
     
  16. noddyspuncture

    Thread Starter New Member

    Jan 15, 2014
    22
    0
    I have tried on all currently wired LED output points (except for point 1) ... I tried: 2,3,4,5,6,7,8,9,&10.

    I am getting the strange symptoms (as explained above...) on points 4, 6 & 10.

    Cheers,
    Tom
     
  17. GopherT

    AAC Fanatic!

    Nov 23, 2012
    5,986
    3,729

    @Wendy
    I think the OP misunderstands what this circuit does. see post 12.
     
  18. eetech00

    Active Member

    Jun 8, 2013
    647
    110
    Hi

    Ok...but how are you making the connection? Are you holding wires together? Are you using a switch?
     
  19. Wendy

    Moderator

    Mar 24, 2008
    20,764
    2,535
    That is my circuit on post #12, I drew it and tested it.

    So you are wanting to light the LEDs sequentially using this schematic. How many LED? Is it being use strictly for LEDs?

    Diodes 1- 35 are so you can do patterns, like wig wag lights or police lights. For a straight sequencer they are not needed.

    I'll be glad to work with you. Have you built this on a proto-board or what?
     
  20. Wendy

    Moderator

    Mar 24, 2008
    20,764
    2,535
    That is funny, I had finished a PCB design but never up loaded it. That little detail has been address. I am a pack rat, data and other wise. I may have a board built that I never got around to testing.
     
Loading...