[petek]

Greg's close, but really there are two types of sensors in the center goal:
Two parallel through-beam sensors which look for balls on the ramp and also validate balls which enter the goal within 2 sec. after the end of a goal-active period. Two are needed to provide coverage of the whole ramp width.

The balls are counted by the through-beam just below the hole in the ramp where the ball drops into the hose.

These through beams are connected to a data acquisition box which talks to the ball counting computer (the PC under the drivers station). The corner goal cameras also connect to this PC. A LabView app. does the all the heavy lifting to figure out whether the signals are valid ball counts and sends the results to the scoring computer.

And we thought making the robots' autonomous work was complex!