I have a light switch that switches 240v (UK) mains. Instead of using that to directly control a light, I want to use it as an input to a controller board so I can also automate the lighting. (It's low voltage LED lighting driven via a transformer although that doesn't really affect my question).
My question is what is the best and safe way to use switched 240v mains power as an input to a low voltage microcontroller circuit? It would be best to use the existing switch to switch a low voltage control signal but I can't change the wiring at at this time so the only input I have to my control is a switched 240v mains power line.
I have other power available where the controller is so I'm not intending to power this via the original light power, I just want to see if I can use it as a control line without extensive rewiring work for now.