Three way switch and Lamp Status

Hello Guys,

Does someone could help me with GPIO and Three Way Switches?

I 'm plannining usage the BBB with relays and my current electrical structure including the Switches, (like the draw attached).

My main problem is identify when the Lamp is High when used by Switch. I cant get the current lamp status.

Does someone have idea how todo this?

best regards,


i would use a photodector of some kind, keeps the mains voltages from
the BBB and will use less parts

Hi Wulf Man, thank you by your response.

But with this I will need add one more “device”(photodector). I would like to usage the current structure, but I dont have idea how dectect Lamp status when using 3 way switch.

Best regards


a photodetector will isolate your BBB from mains voltages. any other way
and you will still need a way to isolate your AC light from mains.
if you need to know which switch of a 3 way switch array has turned on
the light you will need to monitor the crossover wires from each 3 way
you will still need a way to somehow isolate your BBB from the mains

Have you any example this?
Any diagram, code?




Do you have any example (code/connections) this using your photoresitor suggestion ?

Thanks again