so ive been messing around with an arduino mega for a few weeks now trying to get it to drive my old prop pitch rotator and honestly its going better than i expected but im running into some weirdness with the feedback pot reading. the pot itself is a 5k linear and im reading it on A0 but the values jump around like crazy when the motor is actually running, like 50-100 counts of noise even with a cap across the wiper and ground. im guessing its RF or just the motor brushes dumping noise into everything.

the basic logic is done, i have it talking to hamlib via a python script on a raspberry pi 4 that sits next to the radio and it all chains together pretty cleanly - hamlib talks to the pi, pi sends serial commands to the arduino, arduino runs an H-bridge. works great when its just sitting still. its the feedback loop thats killing me right now.

anyone dealt with motor noise on analog inputs like this? im wondering if i should just switch to a 10-turn pot and do some software averaging or if theres a better hardware fix. also open to just scrapping the pot entirely and going with a gray code encoder if anyone has done that on a rotator.

yeah the motor noise thing is super common with prop pitch setups, those old motors are brutal on analog lines. what worked for me was a combo of things - i put a 100nF ceramic cap right at the arduino pin to ground, then added a 1k resistor in series on the wiper line before the pin, basically an RC filter right at the input. that alone got me down to like 5-10 counts of noise which was manageable. then i did 32-sample averaging in software with a circular buffer and that smoothed it out completely.

i did also run separate ground returns for the motor side and the logic side, tied together at one point only at the power supply. made a noticeable difference. if youre still getting problems after that then yeah maybe look at an encoder but honestly the pot approach should work fine once you get the filtering sorted out.

ive been doing something similar with a pi zero instead of an arduino and just running everything in python, skipping the middle layer. not saying thats better for your setup but worth knowing its possible if the serial latency ever becomes a pain. the gpio on the pi can do PWM fine for motor control and the ADC you just hang an MCP3208 off the SPI bus, works great.

the gray code encoder idea is solid though if you want to redo it. i used a cheap optical encoder from aliexpress on a different project and it was rock solid, no noise issues at all. bit more wiring but you never have to worry about pot wear either which matters if youre spinning that thing a lot during contests or whatever.