25 relays and 25 physical switches

[PeteKnight]

You should probably read this:

Using the MCP23017 IO Expansion Board

EDIT NOVEMBER 2021… Anyone interested in controlling multiple relays may also want to take a look at this topic, which uses a pre-built 16-way relay board and 2x 74hc595 shift registers: END OF EDIT . I had a project recently where I wanted to use 5 physical buttons, with built-in LED indicators, to control 5 relays. That meant having 15 GPIOs available, so I built the project around an ESP32 dev board. I also needed a few more GPIO pins for other sensors, so by the time I was done I was o…

Pete.