I have the following plans: I want to use a 555 timer in astable mode to light up 5 different LEDs. These should light up one after the other (i.e. not two at the same time). After that, there should be a pause for the same period of time as for the lighting of an LED. Then, it starts from the beginning again.

I already checked a little today: I need a ring counter. Unfortunately, I don't have one in the library. I'm using PSpice for TI 2020, so I don't have all imaginable parts. Could you suggest how I can use simple means to build a ring counter with 6 outputs? I don't expect you to solve everything, I'm just asking for ideas so that I can start.

I would like to use a typical 9V battery as the source. (If that's too much, I'll just use something smaller or a voltage divider. That shouldn't stop us.)

I can do that with the timer. Did you see in the last thread. How fast can the timer actually get, in terms of frequency?

However, if you have a completely different approach, always give me your opinion! :)

  • 2
    \$\begingroup\$ PSpice isn't going to necessarily provide a pre-assembled Ring Counter, but a ring counter is nothing more than a composition of flipflops and some logic for feedback and pattern generation. The individual parts (flipflops and logic gates) are almost certainly available in a simulator designed for digital tasks. \$\endgroup\$
    – nanofarad
    Nov 8, 2021 at 19:14
  • \$\begingroup\$ After that, there should be a pause for the same period of time as for the lighting of an LED. ... what happens after the pause? \$\endgroup\$
    – jsotola
    Nov 8, 2021 at 19:25
  • \$\begingroup\$ @jsotola It starts from the beginning again. \$\endgroup\$
    – Daniel
    Nov 8, 2021 at 19:33
  • 1
    \$\begingroup\$ that information belongs in the question, not in a comment ... please edit your post \$\endgroup\$
    – jsotola
    Nov 8, 2021 at 19:34
  • \$\begingroup\$ @nanofarad a composition of flipflops Yeah that's the thing. I tried to build a 4-bit asynchronous counter with flip-flops this afternoon, but it went wrong and I realized that I needed a "digital source". \$\endgroup\$
    – Daniel
    Nov 8, 2021 at 22:21

2 Answers 2


Here's a possible solution to to this problem. What you can do is make a simple FSM (finite state machine) with a counter and some logic gates. Below is one I did to get a LED 'pixel' to cycle between red, green, blue, and white.

enter image description here

You could do something similar with a 3 bit counter (you need at least 7 states). Could use a decoder to turn on one LED per state.


I think the easiest way would be to use a 4017 with the LEDs connected to outputs 0-4 and output 6 fed back into MR.

  • \$\begingroup\$ Absolutely!!!!! \$\endgroup\$
    – user173271
    Nov 16, 2021 at 10:54

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