Does anyone have any ideas on how to secure a potentiometer so that it does not move with the rest of the mechanism? When have two on our lift currently and they work fine, but if we lift, then lower, the maximum and minimum values change. Any ideas on how to prevent them from turning? They are currently mounted on 1x2x30 c-channels and axles with a screw and 2 zipties each.
Generally, people use two screws, one on each side, to mount the pots through the semi-circular slits. Have a look at this from the instruction sheet:
https://vexforum.com/gallery/files/8/1/4/0/1/7/_691027.jpg
The use of zip ties might be causing too much shift.
Also, before you secure your pot (before you give the final tightening to the mounting screws), make sure that you can move your arm or whatever and that the pot (red structure body) will not be dragged around. If the shaft going through the pot is too much off-center because the shaft is bent or the arm is experiencing some sort of eccentric movement, then the shaft can put too much force on the pot and stress the pot too much. If the pot is getting stressed, it might be flexing and maybe causing strange values.
Also, make sure you are not running the pot beyond its normal operating range. Pots are usually operational only about a max of 230-250 degrees, but you should probably try to keep your use of them away from the fringes (away from the very highest and lowest values).
I’ve made sure the limits on the pot are well buffered. Our lift is only measuring a change of about 150 degrees and we have a 1000-1200 extra amount of turning in both directions. I’ll try to secure it with standoffs like in the photo and I’ll make sure its not tilted at all.
Sometimes when mounting a pot, it’s all about finding a “sweet spot” at which to do the final tightening of the mounting screws. The pot’s pale rubbery hole through which your shaft passes has a little “give” to it so it can accommodate a small amount of eccentricity in the shaft’s movement, but finding the best place at which to finally lock down the mounting screws might take a few iterations/successions of moving the arm/shaft while tightening the mounting screws a little bit at a time.
If for some reason the shaft is bent too much or the eccentricity is too great and there is no way to fix it, you might have to mount the pot in a way that allows it to “float” a little while still maintaining its orientation to the frame. That’s tricky to do but I’ve seen some teams do that out of desperation.
Jam that puppy down with the hex driver and maybe a little loc tite to boot.
Sometimes having the flat side of the pot along a motor or c-channel helps seat the pot in place too.