# Bright Hub Engineering

## Make a Simple Electronic Casino Home Game: A Roulette Wheel

written by: Swagatam • edited by: Lamar Stonecypher • updated: 4/12/2010

A simple voltage controlled oscillator (VCO) wired around the IC 555 and counter/divider IC 4017 together form a wonderful circuit of an interesting and visually stunning roulette wheel game. Read on the easy instructions to build your own simple electronic game.

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### Introduction

Roulette games can be commonly seen in casinos and clubs. It is a playing device having a large conical shaped wheel with numbers or scores printed on its pockets in a special random manner. It is normally used for betting and wining cash amounts.

The wheel is rotated manually and few balls are thrown into its pockets which shuffles its position as the wheel rotates and eventually settles down into one of the randomly selected pockets with either a winning or a losing number.

The electronic version of such a roulette game is presented here and is perhaps one of the simplest electronic casino home games. Though not as complex as its original mechanical counterpart but nevertheless can be pretty amusing to actually build it and witness the results.

Let’s see how we can carry out the instructions to build your own simple electronic game of this roulette wheel.

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### How the Circuit Functions

The heart of the circuit is the IC 4017 which is a 10 stage decade counter/divider. It is driven by another versatile IC 555 configured as a voltage controlled oscillator (VCO). Let’s try to understand the functioning from the below given explanation:

In one my previous articles I have already explained regarding the pin outs of the IC 4017. We have learnt that the output of the IC changes state from a logic hi to a logic lo sequentially in the influence of rising edges of the clock pulse at its pin 14.

In this circuit the pulse is generated by the IC 555. This IC is wired as an astable multivibrator, but looking into the figure you can find that the supply line to its timing components has been interrupted through a switch. This clever modification is done to effectively convert it into a voltage controlled oscillator (VCO).

On pressing the Switch S1, the reservoir capacitor C1 almost instantly gets charged, also at this point of time a constant stable clock is fed to the IC 4017 and the LEDs at its outputs light up in a cyclic manner producing a revolving effect. The speed may be predetermined by adjusting VR1.

Now as soon as the switch is released, the main supply is cut-OFF, C1 discharges and transfers its charge to C2 through the pot VR1 and the other resistors on its path. This forces the freely running astable to gradually stretch and slow down the time period of its output pulses so that eventually the oscillations stop within a stipulated time. In response to these dying pulses the “rotation" of the LEDs connected to the output of IC 4017 also slow down gradually and stops to select a random score marked on the board. This score will always be selected in random way depending on how long the switch S1 remains depressed and thus can never be predicted accurately.

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### How to Build The Circuit?

Begin by assembling the circuit board first with the help of the given circuit schematic. As usual it may be simply done by inserting all the procured electronic components on a general PCB and interconnecting their leads through soldering.

For the enclosure you will have to procure a suitable circular plastic box with a locking type of lid. You can get plenty of them in wholesale plastic marts.

Next, drill holes on the lid of the box as per the size of the LED in a circular fashion; neatly do the necessary drawings and markings of numbers as per your own liking. Fix all the LEDs into the drilled holes to form a large circle of a chain of LEDs. Also make provision for fitting the" start" button on the center of the lid.

Interconnect all the LED leads from the rear side as per the circuit diagram.

Join the output wires from the circuit to the appropriate points of the LED assembly and the “start" switch.

Finally strap the battery connector to a 9 volt PP3 type battery.

Fix the lid over the box enclosing the circuit and the battery inside it.

Initially you will find that out of the 10 odd LEDs only one is lit up.

On pressing the “start" button, the LEDs get illuminated one after the other in a sequential manner producing a rotating effect.

Initially the speed of its “rotation" is quite fast. It gradually slows down and ultimately after few seconds only one of its LEDs remains lit over a particular unpredictable position.

This position of this lit LED will always vary; no matter how many times the switch is initiated, perfectly imitating a casino roulette wheel.

The above instructions to build your own simple electronic game must have certainly helped you to understand regarding the easy construction procedure of this little roulette game. You may use this only as a fun project to amuse your friends but remember "no betting please!"

Image Credit: http://www.globalsources.com/gsol/I/Roulette-wheel/p/bg/1025194582.htm