Ultrasonic Help

[apalrd]

We have a 10-turn pot sensing drum rotations. The drum rotates slightly more than 10 times, so it is chained (with plastic sprockets) to the drum shaft, providing a slight reduction. We now use about 8 turns of the pot over the entire travel distance.

We don't like encoders for absolute positioning because we don't know exactly where we are, only where we think we should be based on where we assumed (or sensed, with another sensor) we started. The largest issue is that, if we don't start at home, we have to move to home to reset. If we have a practice robot and we don't fold it up into the start position before running it, or we stop running deployed code to change something without folding up into start position, we no longer know exactly where we are. That said, for some mechanisms, it's the best way to do it.