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Project Notes

#084 RouletteKit

Build and examine the workings of a commercial 555 Roulette kit

Hereโ€™s a quick video of it in action:

RouletteKit demo


Julian Ilett really does excellent videos on YouTube, even when heโ€™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 (๐›•) 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

About LEAP#84 555 Timer
Project Source on GitHub Project Gallery Return to the LEAP Catalog

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LEAP is my personal collection of electronics projects, 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 (IMHO!).

The projects are usually inspired by things found wild on the net, or ideas from the sources such as:

Feel free to borrow liberally, and if you spot any issues do let me know. See the individual projects for credits where due. There are even now a few projects contributed by others - send your own over in a pull request if you would also like to add to this collection.