so ive been working on this for a few weeks now and figured id post here in case anyone else has gone down this rabbit hole. basically i have an old prop pitch rotator that i picked up at a hamfest a few years back and i finally decided to do something useful with it instead of letting it sit in the garage. the goal is to have an arduino mega reading az/el from my logging software over serial and then driving the motor controller accordingly.

the motor side is mostly sorted, im using an IBT-2 h-bridge module which handles the current just fine. the problem im running into is the feedback pot — its a 10-turn pot and the ADC on the arduino is only 10 bit so im getting some jitter in the position readings. ive tried averaging like 16 samples but it still drifts a few degrees back and forth and the motor just keeps hunting around the target heading. its not terrible but its annoying enough that i cant really call it done.

wondering if anyone has dealt with this. i was thinking maybe switch to an ADS1115 for 16-bit resolution but not sure if thats overkill or if the issue is somewhere else entirely. also running the whole thing off a raspberry pi 4 now for the rotctld interface which is actually working really well — hamlib picks it up no problem and flrig talks to it fine too.

yeah the hunting problem is almost always a deadband issue rather than resolution. even with perfect ADC readings if your control loop doesnt have a wide enough deadband the motor will never settle. i went through the exact same thing with a similar setup and the fix for me was just defining like a 3-4 degree window where the controller says good enough and stops driving. once i did that the jitter basically disappeared even with the stock arduino ADC.

that said the ADS1115 isnt a bad idea anyway especially if you ever want to do precise satellite tracking where a degree or two actually matters. but id try the deadband fix first because its literally a few lines of code change and you might find you dont need anything else. also check your power supply — if the arduino and the motor controller are sharing a supply the noise from the motor switching can mess with your analog readings pretty badly. learned that one the hard way too.

im running almost the same stack actually, pi 4 with hamlib rotctld and an arduino handling the low level stuff. works great for my yagi on 2m. one thing i did was add a small cap across the wiper and ground on the feedback pot, like 100nF or so, helped clean up the ADC readings noticeably. probably not your whole problem but worth trying before you spend money on external ADC hardware.