I am looking make my own version of theses digital relay/FET controllers so I can have more usability and matrixes.

Switch pro sp9100

it looks like to me they send a serial signal to the controller and then the controller turns the relays on and off. I believe I should be able to achieve the same thing with a arduino and a relay board. I thought about using resistors to sence voltage drop across the switches but then that would limit me to momentary switches only and no latching switches. Just need some help getting in the right direction. Does anyone know of a protocol or have a idea that would work good for this?

First idea [1]: https://raspberrypi.stackexchange.com/questions/24488/how-can-i-combine-many-inputs-on-one-pin

  • Do you have criteria for "work good"? Also what you're controlling with this device may have an impact on useful answers, with respect to FETs, relays, expanders, and what protocol. – timemage May 23 at 0:21
  • this question is unrelated to the Arduino ... it is a general electronics design question, so it is off topic here – jsotola May 23 at 1:35
  • i would use shift registers to easily get 8 buttons on just a couple pins. you could also use cheap pro minis that talk to the main MCU with serial. – dandavis May 23 at 7:24
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    I would use a simple keypad matrix. No mess, no fuss. – Majenko May 23 at 9:45