I want to design a circuit to blinking three LED in a row with 2 second delay for shifting/changing using analog elements only (using Resistors, Capacitors and Transistors and without Micro Controllers).

To be more clear, let assume I have three LED on my board that named LED1, LED2 and LED3.

This is the procedure:

  1. LED1 turns on at the power up and the two others are off now.
  2. After 2 seconds, LED1 turns off and LED2 turns on.
  3. After 2 seconds, LED2 turns off and LED3 turns on.
  4. After two second go to step 1 and repeat again.

How can I design it?

Thanks in advance.


closed as too broad by Matt Young, Sparky256, Steve G, Daniel Grillo, Transistor Jul 28 '16 at 11:13

Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

  • \$\begingroup\$ Are you open to using something simple like a 555 timer? Check it out, its a handy little device. \$\endgroup\$ – Sada93 May 20 '15 at 8:19
  • \$\begingroup\$ @Sada93 Its OK. But the best solution/design for my case is the one that has no IC inside. I already worked with 555 timer. \$\endgroup\$ – Abraham May 20 '15 at 8:21
  • 2
    \$\begingroup\$ Then again a 555 is nothing but transistors and resistors on the inside, which you can build too but it would just be bulky.According to this post you cant use only passive elements electronics.stackexchange.com/questions/3734/… \$\endgroup\$ – Sada93 May 20 '15 at 8:29
  • \$\begingroup\$ @Sada93 I think I can do it using benefit of Zener diodes. Is it an active element? I don't think so. \$\endgroup\$ – Abraham May 20 '15 at 8:40
  • \$\begingroup\$ Define "analog". You are trying to turn lights on an off, which is a digital activity. You're going to run transistors into saturation to turn them on and off, which is digital. \$\endgroup\$ – iAdjunct Jun 26 '15 at 20:12

555 is not a right component for the task; it is okay to use for two LEDs, but things quickly get hairy for more than two LEDs. You need a Ring Counter + astable multivibrator (Examples of ring counters can be seen here: https://www.google.com/search?q=ring+counter+circuit&source=lnms&tbm=isch).

You can try this one for example: http://www.tradeofic.com/uploadfile/ic-circuit/20097142649472.gif

Keep in mind, most of the schematics are ancient and use antique components, so you'll have to find modern equivalents.

  • \$\begingroup\$ +1 for the ring counter made up of discrete transistors. \$\endgroup\$ – tcrosley Jun 26 '15 at 17:21

How about an astable multivibrator? In a 2-LED configuration, they one is on while the other is off, and the frequency determined by your resistor/capacitor choice. You can find the schematic for a 2-LED astable multivibrator on the internet (wiki article here), and I don't see why it wouldn't work for 3 LEDs.

  • \$\begingroup\$ No, it will not work for three; try to analyze it yourself, and you'll see why. The OP needs Ring Counter. \$\endgroup\$ – ilkhd May 20 '15 at 9:21
  • \$\begingroup\$ My bad. A 3-LED astable multivibrator would have 2 LEDs on at all times while it cycles through, which isn't what the OP wants. \$\endgroup\$ – justinrjy May 20 '15 at 9:44

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