I'm trying to build a 13 count johnson ring counter (which flashes LEDs sequentially 1 thru 13 and then repeats), and I found this circuit which looks perfect: 4017 johnson counter

I assembled it with an extra LED on the 555's output pin. Oddly, when I apply power, this LED stays solid on, while none of the outputs of the 4017 are lit. In trying to troubleshoot this, I noticed that the wiring of the 555 differs from all of the standard implementations described on wikipedia (astable, monostable & bistable). QUESTIONS:

  1. Does anyone know if this is a reasonable way to use a 555? The commenters on the aforementioned post seemed to think it was.
  2. Otherwise, if you see it to be faulty, can you suggest an appropriate fix for this circuit? I tried a normal astable setup and got nothing, but I have to admit that my understanding of what the AND gates are doing is too foggy to know if this should work.

Thanks in advance for you help!

Edit: discovered a loose ground to the breadboard with the LEDs. Plugged this in, and now I see that a few of the LEDS are lit -- flickering & different brightnesses -- mostly on the second 4017. Totally stumped.

  • \$\begingroup\$ what value are you using for that anonymous cap in the diagram bottom right? I'm not sure what it should be doing, but a large enough value might prevent the 4017s from clocking? \$\endgroup\$ – Neil_UK Dec 25 '15 at 8:45
  • \$\begingroup\$ @user44635 It's a 100nF, value stuck between the two diodes, up and down. \$\endgroup\$ – user59864 Dec 25 '15 at 9:10
  • \$\begingroup\$ The schematics would be much easier to read if the pin names were also there. \$\endgroup\$ – user59864 Dec 25 '15 at 9:11
  • \$\begingroup\$ Instead of using this circuit which you don't fully understand, build the logic for johnson counter with discrete D- flip flops. \$\endgroup\$ – ammar.cma Dec 25 '15 at 9:40
  • \$\begingroup\$ @G Math 100nF ! that's a hellauv big value. What's it's supposed to do??? \$\endgroup\$ – Neil_UK Dec 25 '15 at 20:50

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