so ive been messing around with this idea for a while and finally started putting something together. basically i want the arduino to read my band data output from the radio (IC-7300, it puts out voltage levels on the ACC port corresponding to which band youre on) and then automatically switch my antenna relay box accordingly. right now i have like 4 antennas and im manually switching between them every time i qsy which gets old fast especially during contests.

ive got a Mega i had laying around and already wrote some basic code to read the analog voltages and map them to bands. thats working fine on the bench. the part im stuck on is driving the relays - i have a 4-channel relay module from amazon and when the arduino triggers it the whole thing kind of resets or glitches for a second. pretty sure its a power issue because the relays are pulling more current than the arduino can handle but im not 100% sure how to fix it without buying a whole separate supply just for the relay board.

also thinking about eventually tying a raspberry pi into this so i can log which antenna is active and maybe control it remotely over the network but thats way down the road. anyone gone down this rabbit hole already? what did you use for the relay driving side of things?

yeah the relay module issue is almost definitely the inrush current browning out the arduino. those cheap relay boards pull a decent spike when the coil energizes and the arduino 5v regulator just cant keep up, especially if youre powering the relay board from the arduino itself. what you want to do is power the relay module from a separate 5v supply - even a little phone charger brick works fine - and just share the ground between that and the arduino. the IN pins on the relay module only need signal current from the arduino so that part is fine, its just the coil power that needs to be separate.

i did something pretty similar with a UNO and a 8-relay board for my amp and tuner switching. ran the relays off a old 5v 2A wall wart and never had another glitch. also worth putting a 100uf cap across the relay board power rails just to smooth things out a bit.

the pi integration idea is actually really nice once you get there, i run a pi 4 here that handles logging, cluster spotting, and i have it talking to an arduino nano over serial for some shack automation stuff. the serial link is dead simple to set up and you can write a little python script on the pi side to listen for the antenna status and do whatever with it - write to a file, push it to a web dashboard, whatever. i use flask for a basic web page that shows me whats active in the shack from my phone.

one thing to watch out for is the 3.3v vs 5v thing if you ever connect the pi GPIO directly to the arduino - pi is not 5v tolerant on its pins so either use a logic level shifter or just do everything through USB serial and avoid the headache entirely.