encoder for cam-driven kicker?

[Ether]

As part of a feasibility study, our team has just prototyped a cam-driven kicker.

A motor-driven cam pushes a cam follower at the end of a lever arm which forces the kicking arm back, stretching the latex tubing. When the cam reaches its largest radius, we want to motor to stop. Then to fire, the motor continues rotating in the same direction, and the cam-follower falls off the edge of the cam (down to the lowest cam radius, that is), allowing the kicking arm to kick, and the cycle repeats.

I'm seeking suggestions as to what type of sensor to use. I'm thinking an absolute encoder would be what I need, but the one in the kit of parts is a relative encoder (as far as I can tell). Is there a way to make that work for this application?


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