Pictured above is one (1) of twelve (12) PCB's furnished with our sensing scheme (comparators, resistors, a multiplexer, and a demultiplexer). These twelve boards will be connected together and used to detect the position of the ball as follows:
The LED's are pulsed in groups along the edge of the table. Corresponding to each LED is a phototransistor that sits across the table. When the LED is energized, the voltage across the phototransistor circuit changes. If the ball is to interrupt the infrared light going across the table, the voltage across the phototransistor circuit drops. This voltage (across the pull-down resistors in the phototransistor circuit) is compared with a reference voltage used in the comparator. The signals from all of the phototransistors are multiplexed and sent to the processor (BeagleBone Rev. A3), which demultiplexes said signals and locates the position of the ball based on the address of the phototransistor that detected the ball.
This process is repeated for sixteen (16) groups of phototransistor and LED pairs along the edges of the table to locate the position of the ball at a power-efficient and extremely fast rate. Once the position of the ball is found multiple times, a trajectory can be calculated and the position of the foosmen can be adjusted according to the future position of the ball.
Stay tuned for more updates related to the operation of the ARM processor on the BeagleBone development board as well as how motors will be used to position the foosmen and kick the ball!
-Khalil
Project Leader, Team Foosbot
Nice design!The layout is just superb..Thanks for keeping us update about its features..circuit board
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