[mluckham]

A limit switch is any kind of switch that closes when your mechanism reaches a "limit" of travel.

We use microswitches (some were included in the KOP), you could use anything including optical detector that you are using, bumper switch, etc.

They are easiest to use when there are only two "limits" (eg: - fully clockwise, fully counter-clockwise). When you have intermediate positions (as in your case) you have to be creative in how and where to place the switches. There would normally be two "limits" (bottom-most position, top-most position) and then a detector for intermediate position.

Hope this is clear - it's been a long day.