so ive been messing around with a raspberry pi zero w for the past few weeks trying to get it to handle antenna switching based on what band im on. the idea is it reads the band data output from my ic-7300 (the one on the back, acc port i think) and then fires the appropriate relay to route the coax to whichever antenna makes sense. right now i have 4 antennas and im sick of manually swapping things around especially during contests when im moving bands fast.

i got the basic python script talking to the serial port fine and i can read the CI-V data no problem, wrote a little loop that polls it every half second or so. the part im stuck on is the relay board. i picked up one of those 8 channel 5v relay modules off amazon and when i try to drive it from the pi gpio the relays kind of half-trigger sometimes, like i can hear them click but they dont always latch properly. wondering if its a power issue or if i need to add transistors or something between the gpio and the relay coils. the module has a VCC and a JD-VCC jumper and im honestly not 100% sure i have that set up right.

anyone gone down this road before? im comfortable with basic electronics but i dont have a ton of experience with driving inductive loads from gpio pins

yeah the JD-VCC thing is the classic gotcha with those cheap relay boards. basically if you leave the jumper on it ties the relay coil power to the same 5v as the logic side, which means your relays are pulling current through the pi's gpio which really cant handle that. what you want to do is remove that jumper and feed JD-VCC from a separate 5v supply — even a cheap phone charger brick works fine. the logic inputs on the board have optoisolators so they'll still talk to your pi gpio just fine but the coil current comes from the external supply instead. the half-triggering is almost certainly the pi's 3.3v gpio not having enough oomph to properly pull those inputs low, combined with not enough current available. separate the power rails and i bet it just works.

i did something pretty similar with a mega 2560 actually instead of a pi, used arduino because i didnt need the overhead of linux for something that simple. but the pi zero approach is fine especially if you want to run a web interface to override it manually which is honestly really handy.

those relay modules are a pain, been there. one thing i'd add is put some flyback diodes across your relay coils if the board doesnt already have them — when the relay de-energizes it spikes voltage back and over time that can do weird things. most of the chinese boards do have them but worth checking. also half second polling might be a bit slow if youre band hopping fast in a contest, i run mine closer to 100ms and it feels pretty snappy. not a huge deal but something to think about