If you like games and DIY electronics, Elektor has the project for you. This roulette circuit features 40 LEDs controlled by a microcontroller. Take a look.

Roulette Circuit

First presented in 2004, the Roulette circuit is built around an AT89C2051 MCU (IC1), which requires only a few external components. "C12 and R41 generate a reset signal when the supply voltage is switched on. X1, C1 and C2 ensure that the internal oscillator of IC1 generates a 12-MHz clock signal."
 
roulette circuit
The project features an AT89C2051. The software was written in C.
A regular switch and a push-button switch (S2 and S1), each of which is directly connected to an I/O pin of the microcontroller, enable user control. The visual representation of the simulated ball is provided by 40 LEDs (D1–D40). Each LED has its own series resistor (R1–R40).
 
roulette circuit
The roulette circuit: 40 LEDs controlled by a microcontroller.

The PCB

The project features a double-sided printed circuit board. The PCB holds the entire circuit except for the 9-V battery.

"You must pay attention to the correct polarisation of the LEDs, ICs and electrolytic capacitors," explains the designer P. Goossens. "Sockets can be used for the ICs, but they are not necessary if you have a certain amount experience with soldering."
 
roulette PCB
The double-sided PCB holds the entire circuit except for the 9-V battery

The Original Project

The article, “LED Roulette: Using LEDs Instead of a Ball,” appeared in Elektor January 2004. You can download the article for free during the two weeks following the publication of this post. Enjoy the article and let us know if you start a project of your own!
Editor's Note: The article first appeared in a 2004 edition of ElektorMag. Some of the components, products, PCBs, and/or links may no longer be available. Yet, we feel the educational content is valuable, and we think it will inspire you to start a project of your own.
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