[Jon Stratis]

for that use, I prefer a potentiometer, as it's the easiest for getting an absolute position reading out of. And if you set it up correctly, you can get it mounted without too much difficulty.

The key for mounting is planning ahead. You really just need to ensure that the hole in your mounting plate is aligned with the shaft. There are several ways to do this, depending on the exact situation, but I find it's easiest to get everything set up and then drill through everything all at once with a pilot hole, then use that as your center to enlarge everything to the sizes you need for shaft, bearing, potentiometer, etc.

After that, you just need to put a hole in the middle of the shaft with a lathe, if you have one. If not, surgical tubing does work great for joining those together!

May potentiometers also have a flat on one side of their shafts - this is a great place to locate a set screw, ensuring the shaft and potentiometer rotate together.

Many potentiometers are also designed for easy stable mounting, by having a small raised peg to one side of the shaft - you just need to drill a small through-hole for that, and the potentiometer won't move once it's mounted!


Whenever possible, I like to add limit switches to both extremes as well. It'll help make sure your arm doesn't tear itself apart if the potentiometer fails!