A very simple 10 LED roulette wheel circuit is shown here. pressing the button starts the LEDs in a rotational motion (sequencing) at full swing initially, and gradually slows down, until it stops to a particular, randomly selected LED.
The randomness of the selection depends upon the time for which the push remains switched ON by the finger. Even a difference of 0.1 second is able to change the position of the final LED position, making the roulette application highly foolproof.10 LED
Simple Roulette Wheel Circuit Diagram
Wheel of Fortune
The Wheel of Fortune circuit could be categorized into a range of specific stages; the LED display stage, an wheel sound audio stage, a voltage controlled oscillator, and a touch sensitive/monostable circuit.
While in the switched "off' condition resistor R1 maintains the IC1a input high and therefore the output of this gate, rigged like an inverter, stays low and C1 is discharged. Connecting the touch pads allows the gate's output to turn high and causes C1 to charge up through D1.
As soon as the finger is taken off from the touch pads and the IC1a output becomes low again, C1 is prohibited from discharging into this gate as D1 now gets reverse biased, rather C1 discharges gradually through R2. The VCO is created through the elements involved with IC1b, c and d.
This wheel of fortune circuit actually produces a number of negative pulses with fixed time period split up by "gaps" whose length of time could be chnaged through the control voltage. As soon as the control voltage (the voltage across capacitor C1) goes under a given limit which is of about 1 / 2 supply voltage the circuit stops oscillating.
In case if it is assumed that the voltage across capacitor C1 goes up to the supply voltage level, which could happen once the touch pads are contacted with the finger, capacitor C2 will begin to slowly charge. The C2 voltage is provided by means of R4, to the schmitt trigger created by IC1a and b.
As the voltage delivered across the schmitt passes across its top switching limit, the IC1d output, which is responsible for inverting and buffering the schmitt's output, turns low.
This forces capacitor C2 to start discharging very fast through the fairly low impedance route provided by R6 and D2. As the voltage across capacitor C2 falls below the lower limit of the schmitt IC1d output turns high again allowing C2 to resume charging yet again. The time consumed for C2 voltage to get to the schmitt's trigger level relies upon the voltage across C1.
Therefore once the voltage across the capacitor C1 become large enough, causes capacitor C2 to swiftly reach the activation stage and the VCO begins generating a high frequency, this frequency goes on becoming less and less as the voltage across C1 slowly drops.
The output voltage generated from the VCO is delivered to both IC3 to operate the connected LED ring and also to IC2a, b and c to generate the "tick-tick" audio output, imitating the roulette wheel rotation sound.
The crystal earpiece which is used for producing the "clicking" sound is operated through a bridge circuit. This successfully causes voltage applied to the transducer to become twice in value and as a result, using the formula P = V^2/R, helps to create a louder audio output.
The LEDs are operated by IC3 whose cathodes can be seen hooked up by means of R7, to the IC2d output. The output of this gate normally stays high, and turns low only when the voltage across the capacitor C1 goes over the half supply threshold.
With the IC3 outputs in the active high position, the wheel of fortune LED display is as a result gets enabled for a time slot that is a little bit extended compared to the time duration of the VCO's oscillation frequency.
Capacitors C3 and C4 are incorporated to enable the decoupling of the supply voltage, and capacitor C5 is included to protect against any RF disturbance that may affect the circuit's functioning adversely.