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Project Notes

#107 RingCounter

Test the classic CD4017 walking-ring counter


This is a classic circuit, often marketed as a hobby kit under various names like “water flow effect” or somesuch.

In fact, it is a straight-forward demonstration of the basic operation of the CD4017 Decade Counter/Divider with 10 Decoded Outputs:

  • a 555 astable oscillator provides a clock pulse to the CD4017
  • the CD4017 counts in the “1 of 10” cyclic manner
  • the CD4017 outputs directly drive a series of LEDs
  • so one LED will be on at a time

In this circuit, the variable resistor R1 gives control of the pulse frequency between 11Hz and 64Hz.

The circuit can be powered over a wide range - from about 4.5V to 15V, depending on the ratings of the specific chips. LED brightness will be affected by the supply voltage, and below 9V it might be desirable to replace the 1kΩ current-limiting resistors with a lower value. When powered by 9V battery source, the maximum current drawn is around 11.2mA.

Note that since only a single LED should be on at a given time, the 10 x 1kΩ current-limiting resistors could be replaced by a single resistor on a common cathode ground link for the LEDs. But it depends on the specific LED ratings, as this subjects all the “off” LEDs to a reverse voltage equal to the voltage drop across the resistor.

See RingCounterController for a variant of this project using an Arduino to control the 4017.

Interesting side-note: a very similar circuit is used in some SMD soldering training kits, such as this kit on aliexpress:

SMD kit



The Schematic

The Build

Credits and References

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This page is a web-friendly rendering of my project notes shared in the LEAP GitHub repository.

LEAP is just my personal collection of projects. Two main themes have emerged in recent years, sometimes combined:

  • electronics - usually involving an Arduino or other microprocessor in one way or another. Some are full-blown projects, while many are trivial breadboard experiments, intended to learn and explore something interesting
  • scale modelling - I caught the bug after deciding to build a Harrier during covid to demonstrate an electronic jet engine simulation. Let the fun begin..
To be honest, I haven't quite figured out if these two interests belong in the same GitHub repo or not. But for now - they are all here!

Projects are often inspired by things found wild on the net, or ideas from the many great electronics and scale modelling podcasts and YouTube channels. Feel free to borrow liberally, and if you spot any issues do let me know (or send a PR!). See the individual projects for credits where due.