556 with 2 4017

Discussion in 'The Projects Forum' started by BWBW, May 17, 2013.

  1. BWBW

    Thread Starter New Member

    May 17, 2013
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    Goal: use a 556 with diminishing frequency circuit to pulse 2 separate 4017 at different cycles. Breadboard setup works (only with one 4017, it seemed too much for all 3 chips on same board). Soldered it, checked it, rechecked it. Only the 'top' 4017 circuit works when outputs plugged into breadboard leds, cycles as expected. The 2nd 4017 (knight rider) doesn't cycle. It may light only one led, or none. When I remove the board's ground wire from the breadboard, all 5 led light and stay on. I'm using a 12v regulated supply through the breadboard to the board for testing.

    Is there an issue with running both 4017 like this in this way on the same board? Can someone please advise what the issue might be, and direct me to keywords and further learning targets?

    pdf of the board map attached. Left side is the 3904 to led output, right side the chips are listed. Thank you!
     
  2. wayneh

    Expert

    Sep 9, 2010
    12,156
    3,064
    Wow, I use Excel for everything but I never thought of mapping a breadboard with it.

    Do you have a picture of your board?
     
  3. BWBW

    Thread Starter New Member

    May 17, 2013
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    Here's the board, photo oriented to the xls map. The 2 green wires on middle right are for the pulse switch.
     
  4. Dodgydave

    AAC Fanatic!

    Jun 22, 2012
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    Can you post the circuit?
     
  5. LDC3

    Active Member

    Apr 27, 2013
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    I don't see the wire on the 556 from pin 10 to Vcc (although it might be hidden).

    In the lower 4017, D4 and D5 end on the same line in the picture, but not in the excel diagram.
    I believe the diode from 2a to 2a is backwards.
     
  6. sheldons

    Well-Known Member

    Oct 26, 2011
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    post your schematic....
     
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  7. BWBW

    Thread Starter New Member

    May 17, 2013
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    Thank you for your help so far, good catch on pin 4 and 10 of 556. I used xls for my schematic, but here's my first attempt at drawing one out. I only drew out the non duplicated parts, as the 2 4017 inputs are identical, aside from getting the clock from either pin 3 or 9 of the 556. I also have more than one power and ground row on the actual board, is that a design issue?

    Values for 4017s:
    - 10k pull down on pin 15
    - Q0 through 7 through 470ohm to base of 3904

    556:
    - 47k resistors
    - .22uf and .47 uf ceramic caps

    I've swapped out the chips, tested on breadboard. Multimeter not showing any bad solder spots.

    I cut the wire from pin 9 of 556 to 4017x1 to try to test output, and the 4017 cycles if I touch pin 14 input with finger.

    And, as mentioned before, if I remove the boards ground wire from the breadboard, all LEDs go on for both 4017.

    Thanks again for helping me learn and diag.
     
  8. sheldons

    Well-Known Member

    Oct 26, 2011
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    Quite a few errors with your circuit....you need a switch on reset to pin 15,the inhibit on each 4017 connect to pin 8-if connected to supply the 4017 freezes its count....the counters can be reset at any time by feeding an output back to pin 15 via a diode if required......the transistor op stage shown can be duplicated and connected to the 4017 op to drive your leds....this schematic will give you a starting point for what you need.If using a switch to pulse your 4017 circuit you need to debounce your switch or the counters wont count properly
     
    Last edited: May 19, 2013
  9. LDC3

    Active Member

    Apr 27, 2013
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    Tell me if this describes what you want.

    For the upper 4017, you want to light 7 LEDs in progression and reset the 4017 on the 8th count (which will light the 1st LED).

    For the lower 4017, you want to light 5 LEDs in an up and down sequence (0, 1, 2, 3, 4, 3, 2, 1). When the 8th line goes high, the IC resets and restarts the sequence.

    The 2 (vertical) diodes at 1a and 2a should be replaced by wires since the 7 horizontal diodes prevent feedback. Actually, all the horizontal diodes can be replaced with 1k (or higher) resistors. Since your LEDs do not light up, maybe the diodes are backwards. An easy test is to bridge one or more diodes with 1k resistors and see the results.
     
  10. BWBW

    Thread Starter New Member

    May 17, 2013
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    Thanks for your help. Updates:

    - 556: pins 4 and 10 to supply
    - added 1uf cap to each 4017 pin 15 with 10k r
    - added 3904 to each 556 output as switch (per Sheldons)
    - removed diodes, exchanged with wires.

    LDC3, yes that's the desired outcome, although 4017.1 is an 8 count.

    With these changes, 4017.1 cycles as expected. 4017.2 stays on 0 count, lights the first LED, no cycle. Both 4017 are wired the same way, in terms of pins 8, 13, 15, 16.

    Swapped out chips to confirm it's not the issue.

    Where would I go next?
     
  11. sheldons

    Well-Known Member

    Oct 26, 2011
    616
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    check your clock on pin 14 of the second 4017 goes hi and lo from your 556 output,check the wiring on pin 13,pin 8-make sure they are grounded-the 4017 is being reset as Q0 is hi-heres a way using a few diodes and 5 transistors to get the outputs to switch as you want but it does require all of the 4017 outputs
     
  12. LDC3

    Active Member

    Apr 27, 2013
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    I think there is another connection mistake. You have 1 CONT (pin 3) connected to the clock on the lower 4017. I think you want 1OUT (pin 5). At least that makes more sense to me.
     
  13. LDC3

    Active Member

    Apr 27, 2013
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    Actually, you should have resistors on the lower 4017 outputs since the outputs that are connected, one will be low and the other will be high, which will heat up the 4017 and may not allow the LED to light.
     
  14. sheldons

    Well-Known Member

    Oct 26, 2011
    616
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    the 4017 does not need pull up resistors on the outputs-heres the data sheet for the 4017
     
  15. LDC3

    Active Member

    Apr 27, 2013
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    I am not talking about pull-ups. I am saying that he will have a ground loop when line 1, 2, 3, 5, 6, or 7 is high. After thinking about it, diodes are the best way to go.
     
  16. sheldons

    Well-Known Member

    Oct 26, 2011
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    Like this....on the 4017 0utputs.....
     
  17. LDC3

    Active Member

    Apr 27, 2013
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    Not quite, since you don't get the sequence completed in 8 counts; your diagram need 9 or 10 counts. To change your diagram, remove Q9 and Q8. Place Q7 where Q8 is, place Q6 where Q7 is, and place Q5 where Q6 is.
    The 2 end LEDs only have one output attached.
     
  18. BWBW

    Thread Starter New Member

    May 17, 2013
    9
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    Thank you for all of this input. will move the 556 pin 3 to pin 5 as it should be. Will go back to diodes for 4017.2.

    On the diode note: i used 1n4007 originally, are those suitable, or is 1n4148 more appropriate in these apps?
     
  19. LDC3

    Active Member

    Apr 27, 2013
    920
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    Either one should be OK.
     
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