What I want to make is a circuit using only logic gates made from transistors, and not using any IC.

What I want to do:

  • There is 1 button and 8 LEDs.
  • When I press the button the first LED turns on.
  • When I press again the second led turns on and the first one is off.
  • If I press again the 2nd turns off and the 3rd one is on and so on.
  • When the 8th is on and I press the button, it turns off and the 1st one turns on.

Edit: I didn't had much time, and I made this : https://drive.google.com/file/d/1gDnuwpmMbkCDTSN9Rp9RtZGqToKvfi5S/view?usp=sharing Its it works somewhat, but if a bulb lights up the bulb before it don't turn off. I tried to connect the A output after it and to the reset button with an OR gate to its "reset" instead of connecting it to the B output of the previous.: https://drive.google.com/file/d/1mzq8qIRuFnLLbg0kcDwnM-36qrQj2Z_V/view?usp=sharing But it doesn't work. What should I do ?

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    \$\begingroup\$ Show your most recent attempt. \$\endgroup\$ – Chu Sep 2 '20 at 13:59
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    \$\begingroup\$ Hope you have alotta transistors on-hand..... That's gonna be a big circuit if you don't use IC's. \$\endgroup\$ – Kyle B Sep 2 '20 at 14:09
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    \$\begingroup\$ BTW, I think what you're looking for isn't a "counter", your description sounds like a "shift register" to me. You might Google that instead.... electronics-tutorials.ws/sequential/seq_5.html \$\endgroup\$ – Kyle B Sep 2 '20 at 14:10
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    \$\begingroup\$ It would be much easier to help you if you at least show us your ideas. Otherwise, just google for "discrete d flip flop" and work from there. There are plenty of useful links. \$\endgroup\$ – StarCat Sep 2 '20 at 14:34
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    \$\begingroup\$ "What should I do?" Add the schematics into your question, not in external links. That way we don't have to follow links to understand your question and the question will still make sense when the links die. Note that you have already accepted an answer indicating that your question has been answered to your satisfaction. Your update indicates that it hasn't. You can un-accept to attract more answers. \$\endgroup\$ – Transistor Sep 5 '20 at 7:51

The counter you are describing appears to be just a an 8 element shift register with the output of each register hooked to one LED, and the clock connected to a button.

For the clock to work you need to make some sort of a de-bounce circuit so you only get one clock edge each time you press the button.

The shift register is just a bunch of D-flip-flops set up so that the output of one feeds the input of the next one. So making the shift register ultimately boils down to figuring out how to make a D-flip-flop.

D-flip-flops can be made from a modified bi-stable latch circuit. The basic bi-stable latch is made from two transistors and four resistors. It can be modified with an extra transistor to add clocking and a data input.

This link shows how. https://hackaday.io/project/164485-flip-flops-using-discrete-transistors

You would also need a reset button to guarantee the initial state of the flip-flops (since you want one of them to be on, and all the others to be off).

  • \$\begingroup\$ Thank you very much ! That is what I was looking for. Someone finally understood what I said. \$\endgroup\$ – drmarton11 Sep 2 '20 at 16:35

You want a system that has "memory" — it needs to remember its state from one moment to the next, and move from one state to another state when you press your button.

This means that you need one or more memory devices. The simplest memory element is a flip-flop, and the simplest flip-flop can be created by cross-connecting two NAND or two NOR gates.

Start by building a single flip-flop and playing around with it. Then you can learn how to combine multiple flip-flops to build more complex circuits. The topic is far too broad to get into here, but there are plenty of resources available on the web.

For counters, shift registers, and similar circuits, the key concept is "edge triggering". You can build edge-triggered flip-flops using gates (a DFF is either six 3-input gates or eight 2-input gates), or you can get the same effect by using a two-phase clock system.

  • \$\begingroup\$ If you want that information in video format, search for Ben Eater on YouTube. Transistors to CPUs playlist - youtube.com/… \$\endgroup\$ – Martin Sep 2 '20 at 14:15
  • \$\begingroup\$ I've already made a memory like this, I'm currently working on a 8 or 16 bit memory, which made from NOR gates, a reader and a writer for it, this circuit that i want to create is for the writer, selecting which bite to write 1 or 0 to(so there is only 3 button). Everything done except for this counter, I had also had this idea but I couldn't make anything functional. \$\endgroup\$ – drmarton11 Sep 2 '20 at 14:16

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