I've been seriously considering using various flavors of the Arduino for home control and security. Based upon my experiments and research it has enough horsepower for my application (basically communicating with the control server and obeying commands sent). The two issues I see are power supply and communication.
I'd love to simply hang a bunch of these off of CAT6 cable, since my house is structurally wired, but many will be in places where there is no AC (or DC for that matter). I briefly considered running very low power over the CAT5 but voltage drop and potential fire risk make it a non-starter.
I don't see why running 9V from a current-limited supply over CAT5 cable would be a fire risk, and as long as you don't draw too much current the voltage drop will be negligible.
I'd reconsider the non-starter, as distributing low-voltage current-limited DC throughout your house would actually be pretty cool (and useful).
One of my (fire related) concerns was someone plugging in a device to my ethernet+power lines that wasn't expecting it. It looks that may not be a problem after all.
Daveg360 - thanks. I had heard of ethernet over power but not the converse. That looks very useful.
RuggedCircuits/bld - thank you for the links. I am digesting them this morning over a steaming mug of joe.
What "granularity" are you aiming for with this network. For example will you want node to read a light switch (fine granularity, nodes can just perform a single operation), or will there be a node for each room (coarse granularity).
If you're going the fine approach an Arduino and shield for every node will get very expensive, PoE or not.
Sure, you can roll your own provided the shield doesn't interfere. I'll have to order one and see how accessable the pins are for the RS485 connector. Plug-n-play would be even better but I suspect that won't happen unless I design my own ethernet shield.
Graynomad - I am primarily designing for security but the control portion will likely be coarse granularity. I haven't completely thought that all out yet. I have some low voltage (12vdc) controls already in place (light switches, etc) so the interfacing should be fairly simple. I may have to mux a few things if my granularity gets too coarse.
I know this is somewhat off-topic for the forum but it is germain to the discussion. I have a driveway gate that I want to control with an Arduino but it is ~500 feet from the house. Since that seems to be well beyond the limit of cat6 without a repeater would I be better off using some form of wireless signal?
The communication will be fairly primitive: open, close, and perhaps an entry alert/notify.
RS485 works to 4000' over twisted pair (at slower speeds), wouldn't it be OK on cat6?
Yes, RS485 would work fine on cat6 from what I can tell. It would be close to the limit though for powering the Arduino. If I went wireless I would have to install a solar panel and battery which suddenly makes RS485 begin to look more attractive. :-/