Background
My plan is to use a bunch of Arduinos (say one per room) to connect to a number of sensors and actuators in the given room. For example a cheap £1.20 PIR in the ceiling, vibration/open/close sensors in doors and windows, temperature and humidity sensors in discreet locations. Each Arduino will be placed in a deep wall back-box, powered by mains, and CAT6 cabled back to a central server (using MQTT as a transport protocol).
My questions
I'm looking for the smallest, cheapest, fire-safe equivalent to the wall transformer for supplying 5V to Arduino, which can be mounted in a ceiling void or light switch back box. Something perhaps like the 12V transformers you find powering halogen spots, mounted in the ceiling. I'm sure I can hack one from a wall-wart, but I'd rather do something a little more electrician-friendly. Has anyone seen such a thing?
Has anyone looked into the effect of using long cables between an Arduino and a given component? This is a general question and I know it comes down to exactly what signal I'm putting down the wire, shielding, wire gauge, etc. But I'm hoping perhaps for some initial guidance - maybe someone has already connected their ebay PIR, humidity sensor, rotary controller, or LED to an Arduino over 20m of CAT6 (using just a single pair) and found it works perfectly? Or what about powering bog-standard backlit 16x2 displays over 3x bonded CAT5 cables? Is this a ridiculous idea?
General architecture. My current idea is to have 1x Arduino per room, each room cabled back to the server cupboard. Any advances on that idea? Is it always best to run CAT5 where possible, or perhaps just rely on wireless?
Interfaces. Anyone designed their own? I'm talking 4 gang custom made wall plates, made to look really nice, perhaps with a small display to show current track playing, etc. Anyone know of any UK suppliers or manufacturers I can get stuff shipped in? I'd like to avoid the modular style of wall-plate, I find them really ugly!
I'm looking for the smallest, cheapest, fire-safe equivalent to the wall transformer for supplying 5V to Arduino, which can be mounted in a ceiling void or light switch back box. Something perhaps like the 12V transformers you find powering halogen spots, mounted in the ceiling. I'm sure I can hack one from a wall-wart, but I'd rather do something a little more electrician-friendly. Has anyone seen such a thing?
Mains powered devices need to be enclosed to get FCC approval.
You can get ones like this with screw terminals though:
(Search for "5v regulated power supply" on eBay to get an idea...)
hazymat:
Has anyone looked into the effect of using long cables between an Arduino and a given component? This is a general question and I know it comes down to exactly what signal I'm putting down the wire, shielding, wire gauge, etc. But I'm hoping perhaps for some initial guidance - maybe someone has already connected their ebay PIR, humidity sensor, rotary controller, or LED to an Arduino over 20m of CAT6 (using just a single pair) and found it works perfectly? Or what about powering bog-standard backlit 16x2 displays over 3x bonded CAT5 cables? Is this a ridiculous idea?
Lots of people have.
For low current it's not a massive problem. 20m should be OK.
For long distances you need a thing called RS485.
hazymat:
General architecture. My current idea is to have 1x Arduino per room, each room cabled back to the server cupboard. Any advances on that idea? Is it always best to run CAT5 where possible, or perhaps just rely on wireless?
Wired is always more reliable but that's really up to you. You're the one who has to install the cables.
hazymat:
Interfaces. Anyone designed their own? I'm talking 4 gang custom made wall plates, made to look really nice, perhaps with a small display to show current track playing, etc. Anyone know of any UK suppliers or manufacturers I can get stuff shipped in? I'd like to avoid the modular style of wall-plate, I find them really ugly!
That's down to your budget, and how much time you want to spend programming
eg. An Arduino Mega with large TFT touch screen should cover most usage scenarios... but will cost you $100 each.
Wireless can be much cheaper, the price of copper is the limiting factor for cables,
whereas ISM transceivers and the like can be a few pounds/dollars.
Have you considered battery power? A sensor node that wakes up every so often to
send one packet of data can have a very low average current drain. I'd suggest
looking at JeeNodes for a good example of this approach:
Hazymat
I'm doing the exact same thing, fully wired ethernet.
My plan is similar to yours but I am going to likely use an Arduino with power over ethernet. That way there is no extra power line required or transformers.
As far as an interface, I am going to investigate a windows tablet running a custom Rainmeter type interface (rainmeter.net) that accesses a MySql database for the status of all the sensors as well as access the security feeds etc.... Each individual room won't have an interface, but I plan on maybe 3 wall mounted tablets (master bedroom, Kitchen/Living area, and basement entertainment area) and a 'mobile' one that can be carried around.
I am using cat5 to run things that i have some times questioned the safeness of sometimes joined pairs sometimes not and its held up very well so far (don't push it to hard tho it will burn). I built my smart house foundation in during a re model and ran individual wires to output things like dim-able cfls the stereo amps and things and cat5 to everything input wall switches touch switches rfid temp sensors and such in the house. All is controlled from my phone and a mega 2560 it did take a lot more wire tho. If i had it to do over i would probably use 2.4 ghz wireless.
hazymat:
I'm looking for the smallest, cheapest, fire-safe equivalent to the wall transformer for supplying 5V to Arduino, which can be mounted in a ceiling void or light switch back box.
