so ive been messing around with this for a few weeks now and im making progress but hitting some walls. basically i want to use an arduino mega to drive my rotator controller instead of using the manual knob all the time. the rotator is an old hygain T2X and the controller has the feedback pot in it already so in theory i should be able to read the voltage off that and figure out the bearing.

my problem is the ADC on the arduino is picking up a ton of noise, like the readings are jumping around by 10-15 counts even with nothing changing. i added a 100uf cap across the pot wiper to ground and it helped a little but not enough. running the thing off USB power from my laptop and wondering if thats part of the issue. also the motor drive side im just using a relay module for now which works but theres definitely some relay chatter getting into the analog side when the motor runs.

longer term i want to tie this into hamlib so i can point the beam from the logging software automatically but im not there yet. just trying to get stable bearing readings first. anyone gone down this road before?

yeah the noise issue is almost certainly your power supply and the relay transients coupling in. USB power from a laptop is notoriously noisy for analog work. try running the arduino from a separate regulated 5v supply and use a 10uf tantalum plus a 0.1uf ceramic right at the AREF pin — that made a huge difference for me on a similar project. also if you can, put a small RC filter on the pot wiper before it hits the analog input, something like 10k and 1uf, that'll roll off the high frequency garbage.

the relay chatter thing is a real problem. you probably want to add flyback diodes if you havent already and maybe put the relay coil drive on a separate ground trace that only joins at the power input. or honestly just swap to a motor driver IC like an L298 and ditch the relays entirely for a cleaner setup. the T2X motor isnt pulling that much current if i remember right.

for hamlib integration later, look at the rotctld daemon and there are already some arduino sketches floating around that speak the hamlib protocol directly over serial. saves you having to write that part yourself.

i did something similar with a cheap chinese rotator not a T2X but same idea. the noise thing drove me crazy for a while. ended up doing the ADC averaging in software, just taking like 32 samples and averaging them, which helped a lot more than i expected. not a fix for the root cause obviously but gets you usable numbers while you sort out the hardware side.

also just to mention — i eventually moved the whole thing to a raspberry pi zero W instead of arduino because i wanted to run a web interface and it was easier to just run python. but the arduino approach totally works if youre already down that path, dont let me derail you