Recently I started thinking about ways I could automate/log sensors in my home at the lowest cost possible (aka, not ripping apart walls to install wiring, and not forking out heaps of cash for ethernet shields). I really like the idea of RS-485 in general, mostly due to the simplicity and cost of transceiver chips (under $2 a piece). The general idea would be to place a 'node' in each room, which would consist of an Arduino/microcontroller and a RS-285 transceiver chip. Each node would act as a slave device and would communicate with a centrally located master. Initially I considered connecting all of the devices wirelessly via radio, which I suppose would be fairly cheap, but I prefer hard wires connections. So it got me thinking, why not use an existing CAT5 plug found in most rooms? I believe there's typically a couple of unused twisted pairs.
So basically I'm wondering how feasible this idea would actually be. Some potential problems I'm looking at: 1) With RS-485, nodes should be placed in a line-like fashion, which isn't exactly possible with the existing ethernet configuration, as the lines propagate outward from a central switch/router. There could be some impedance/resistance issues. 2) Data could be effected when passing through switch/router (which I could bypass externally from router)
Anyone have some insight on this? I'm not 100% set on RS-485 and the CAT5 approach, other ideas are most welcome. Other thought would be to transmit signals over power (bit risky, not totally comfortable with this), transmission over phone lines (illegal I'm assuming), data via ethernet (ethernet chips are pricey), or focus on wireless via radio.