2836 has been using Allen-Bradley IR sensors. While I don't remember the exact part numbers, I believe they were in the 7000 series (
http://www.ab.com/sensors/photoelect...alty/7000.html). There's a transmitter on the left side of our ball collection area, and a receiver on the right side. When a ball enters the area, the IR beam is broken, sending 4 volts to the digital sidecar. The transmitter is powered by a 20 amp breaker on the power distribution board.
At the moment we're only using the IR sensors for autonomous, such that as soon as a ball is detected, the kicker activates, launching the ball to the next zone. These sensors have worked perfectly, and we've successfully scored in autonomous at the NYC Regional.