Optical sensor for use with retroflective tape

[apalrd]

We used a Banner red-light or IR light adjustable object sensor and an aluminum wheel with black gaffer's tape lines. It worked really well. We had one of each sensor, so the practice bot got one and the comp bot got the other. We had a 4-line disc with very uneven dark/light spacing and not terribly accurate angular spacing, but if we setup the counter to average 12 samples then any phase error between the lines would cancel out and we got a really nice clean signal.

We were running our wheel up to 2800rpm last year. If we were dropping pulses, we could have made a half black half aluminum disc and still had plenty of resolution due to the extremely high speed.

For cheaper sequencing object detection, we found some really nice, light sensors made by Sick that could detect balls easily. They look kinda like the Banner ones but they're not adjustable and have a clear housing. We weighed them at 28g including cable (1m or so) and plastic locking nut. By comparison, the 2011 KOP and FIRST Choice ones weighted around 1/3rd lb EACH including cable. I don't think we found a speed spec for the SICK sensor, but it was perfect for detecting balls.