Wheel of FORTUNE


This circuit turn on one LED at a time on the circle of LEDs when the push button is pressed.
When it is released, the LEDs slow down and finally stop on your lucky number.

Principle of Operation
The circuit consists of a 555 IC configured to oscillate and the frequency of oscillation depending on the voltage on the 47u electrolytic.
When the button is pressed, the voltage on this capacitor is very close to rail voltage because the push switch charges the 100u on the base of the BC547 transistor and this effectively create a power supply for the timing section of the 555.
The transistor is called an emitter-follower and it will deliver current via the emitter, through the 1k to the 47u. As it delivers current, a very small (about 100th) is also taken from the 100u and to speed-up the discharge of the 100u it has a 470k across it.
As the 100u discharges, it takes longer for the 47u to charge to 2.3 rail voltage and the output frequency of the 555 gradually decreases.
Eventually the voltage supplied by the transistor is not sufficient to keep the 555 oscillating and it "freezes." The circuit stops on your lucky number. 





The Circuit


Wheel Of Fortune Circuit

The photo identifies all the components and how to fit them to the printed circuit board.
Use a constant-heat soldering iron (320 degrees C) and fine solder (0.8mm).
Fit one component and splay the legs slightly so it doesn't fall out of the holes. Turn the board over and hold the soldering iron on one side of the lead and the solder on the other side. The solder will melt and flow across to the iron. This will take less than one second.
Snip the leads close to the solder-joint. Solder one component at a time. Use the photo below to identify each component and how it is fitted to the board. All the components must be fitted around the correct way, and there is only one way to fit them. However the 4 resistors can be fitted around either way as they are classified as a "non-polar component."


The Complete Wheel of Fortune


Wheel Of Fortune Components

You can see the flat on the side of the LED and the placement of the two electrolytics. The two 1k resistors are in the centre with the to 470k resistors.
The cut-out in the end of the IC sockets goes over the semicircle on the board and the notch in the end of each IC is also fitted over this semi-circle. The switch only fits around one way and the electrolytics are identified by the stripe down the side being the negative lead and this lead is the short lead.
Connect a 3v to 9v supply to the 2-terminal connector with the positive on the left and the negative on the right.
 

You can buy this kit for about $5.00 post-free

21-7-2013