Electrical Engineering Stack Exchange is a question and answer site for electronics and electrical engineering professionals, students, and enthusiasts. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I have recently started working on 9 LED Knight Rider Circuit on a breadboard. All the connections have been done according to the circuit diagram given in this article. But I am having a problem with it - The light is running only one way instead of coming back and forth. Can anybody identify the problem and suggest me the modifications to be done to this circuit arrangement?

share|improve this question
Sorry, but that's a truly atrocious schematic. I think it was badly copied from somewhere else. – Spehro Pefhany May 6 '14 at 7:16

Try this, which is probably the original. It's available on this website. The schematic you linked has many problems, such as outputs shorted to ground or to other outputs, inputs connected to inputs only (transistor drive) etc.

enter image description here

Connect each LED with a series resistor from each output \$Q_I\$ to ground.

share|improve this answer
Well spotted, I was just looking at the original wondering where anyone was going to start. – PeterJ May 6 '14 at 7:21
No need for resistors, there is at least 100 Ohms built in the high side driver. – user41337 May 6 '14 at 13:37
Which goes to 1000 Ohms with only 5V on this old stuff. – user41337 May 6 '14 at 13:44
At 12V you should use resistors. At 5V, with CD4017 (not 74HC4017), no need for series LED resistors. ;-) – Spehro Pefhany May 6 '14 at 13:56
I read the specs and 74HC4017 is 6V max with ESR=365 ohms typ. Based on Voh, Ioh, CD4017 on 15V has an ESR of 220 ohms and 1000 @5V and only one output is active, so Pd is low. – user41337 May 6 '14 at 14:37

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.