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:
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:
- Does anyone know if this is a reasonable way to use a 555? The commenters on the aforementioned post seemed to think it was.
- 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.