The basic controlling devices which I used for this design were Altera chips which I programmed. I learned the Altera software, and used some of the macrofunctions provided by Altera to develop the logic that I needed. One 24 pin, 610 Series Altera chip was used to control one players controls and another for the other.

The Altera program consists of a BCD Counter, and a BCD to Seven-Segment Driver. It was also necessary to make the two chips interact with each other in order to perform the lockout function described in the overview. An and gate was used to detect when both the QD and QA outputs were active, which indicates a score of nine. This would then turn on the winner light, and send high signal to the GN input pin of the other Altera chip. As can be seen in the table below, a high GN signal holds the count of the opponents score. The rest function was performed by setting the a, b, c, and d inputs to the BCD Counter to ground within the Altera chip, and then using a normal closed switch on the LDN input to load the a-d settings of low.

The score light and the score buzzer were controlled by a 555 (one-shot) timer. Upon receiving an input pulse, the one-shot circuit provides a longer high logic level, the length of which is dependent on a capacitor and resistor value. The relationship between the time step (T) and the two components is T=1.1RC. Both the Altera chips, and the timer circuit was powered by a 5 volt power supply. However, the score light, buzzer, and large LED seven segment displays were powered by a 12 volt DC supply. Therefor, these components are switched on and off by 2n2222 transistors.

The major problem which I ran into with my design was that I did not debounce the limit switch signals. Therefore it was necessary to reprogram the Altera chips to include an SR Latch. Then, the pulse coming from the limit switch was first sent through this latch, and then into the BCD Counter. Once this was added to the program, the entire system worked extremely well. I would recommend this design to anyone who is looking for a inexpensive ($65-$80) way to control an air hockey or fuseball table.

The entire circuit for the air hockey controller can be seen on my home page.

74190 (Counter)

4-Bit Decade Up/Down Counter with Asynchronous Load

Inputs | Outputs

CLK_ GN_ LDN_ DNUP_ D_ C_ B_ A | QD_ QC_ QB_ QA

X___ X ____L_____X____d__ c__ b__a | d ___c ____b __a

X ___L ____H_____ L_______________ H___ L___L ___H

X ___L_____H _____H_______________L____L ___L ___L

_____L ____H_____ L |__________________ Count Up

_____L ____H _____H |__________________ Count Down

_____H ____H _____X |__________________ Hold Count