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Project Notes

#084 RouletteKit

Build and examine the workings of a commercial 555 Roulette kit

Here’s a quick video of it in action:

RouletteKit demo


Julian Ilett really does excellent videos on YouTube, even when he’s just building a dinky electronic kit like this 555 Roulette.

So I got myself one of the kits too - mine was all of USD1.11 with free shipping from aliexpress. Dang, now it is only USD1.05!!

And surprise, surprise - mine also came with surface mount components despite the product info online that clearly details DIPs and through-the-hole parts. No mind, a chance to steady my hand for a bit of surface-mount soldering. The IC pin pitch is not too fine, but you definitely need tweezers to get deal with the MELFs.

I must say I was also a little surprised when the unit worked first go - I was sure there would be at least one dry solder joint or bridged connection somewhere.

So how does it work? Basically like this I think:

  • pressing the switch charges the R1/C1 network and turns on the Q1 NPN
  • Q1 will remain on while C1 discharges through R1 with time constant (𝛕) of 22s.
  • Q1 activates the 555 in astable configuration, with a decaying frequency governed by the discharge of C2 through R3 when Q1 turns off.
  • pulse stream from 555 pin 3 feeds the CD4017 pin 14 clock signal
  • the CD4017 will enable its 10 output pins in sequence, lighting the attached LED, until the pulse stream stops


The Breadboard

The Schematic

The Build

Credits and References

Project Source on GitHub Project Gallery Return to the LEAP Catalog

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.