I'm working on a home automation/security system (Only in my head at this point) and stumbled upon RS-485 transceivers. using RS-485 with PoE seems to be like a great idea to keep cords to a minimum.
In a Cat5 cable, I'll have 4 twisted pairs, I'll need two conductors for the RS-485 bus, but I was hoping to use the remaining 3 pairs for a modified Power over Ethernet setup.
Can I run a long Cat5 and use 1 pair for a RS-485 bus, and the remaining 3 for a PoE bus? So I'll inject 48V DC into the other 3 pairs, so at each node I'll have 2 data lines, and combine 3 grounds and 3 VCCs.
I'm going to use Arduino's that hopefully will be drawing very little current (under 10ma each is my estimation) but can you bus PoE the same way that RS-485 lets you?