Thanks for the input Robert

As you put it, I am moving coke cans, indoors at normal temperatures.

No need for accuracy, I understand about the optical sensor, all I need to know is the pinion will not try to run off the end of the track, either end, after a hiccup, if that happens it just needs to get the signal from the switch, exit the current loop, "find centre" then revert back to whatever the pots are telling it, it will never be left alone, the user/operator will always be present as the items its pushing/pulling will vary.