Low power (12V and less) in ceiling/walls safe? and permit required Washington State
As I will be soon putting the ceiling back on my kitchen, I was thinking I might want to put in some low voltage wires for 12V DC and below to power sensor devices/ micro processors if I want to automated my house. Literally, I will just leave wire in the ceiling beams, and know where I left it, so in the future I can make a small hole and connect low power devices into the ceiling if needed (maybe temperature sensors or something like a raspberry pi < 5W)
To power the circuit I will either just have a wire poke out a wall then connect it to a AC to DC transformer powered off the mains, or wire it into a 12V transformer into the wall (do they exist - you can get USB wall sockets).
Is this something i can do safely, and without the need of a permit?