I'm still trying to flesh out my vocabulary, so I'm looking for some project direction.
Here's the scenario: One or more Arduino's in central location (telecom closet/workbench) with an incoming (say a 48-port) cat5 patch panel. Each port in the patch panel leads to a sensor (pir/motion, temperature, humidity, luminosity, etc), display (16x2 lcd), relay, or (stepper) motor somewhere else in the house. Any voltage (3.3V/5V/7.5V/12V/30V/48V) and also power over Ethernet (802.3af) is available at the workbench and can be patched into any port. Multiple (reasonable number of) cat5 cables can be run to any location (currently). Let's assume that each cat5 could be up to 100m in length (it won't be, hopefully closer to 60 ft max).
I'd love to simply run Ethernet to every location, assign an IP address to every sensor and collect the data over the network. From what I've found so far, it looks like any option which includes TCP/IP instantly starts looking like $60 per location. It needs to be cheaper than that.
What technologies should I investigate in this scenario?
Ideally, everything would be powered from the central location either by running voltage directly over cat5 or using PoE (and splitting it out on the other end with something like TRENDnet TPE-104S) if necessary.
Could the intelligence on the remote ends could be provided by something like an ATTiny with a RS485 chip? That looks mucho cheap. I'm guessing program the ATTiny like this
so it knows how to communicate with the attached sensor and transmit that data to the central Arduino(s) via RS485/Modbus? ATTiny chips are cheap/simple enough (it looks like) that even with 48 different locations, it could still be affordable. ATTiny's also look smart enough to be able to be functional.
I'm thinking an application larger than just one project. If I could eventually build a simple enough PCB that could be used in this scenario, it seems like it would be a useful tool for these types of projects. Most of the Arduino projects I've seen online (like bildr.org) assume a sensor and an Arduino together. Since I'd like to distribute these sensors and/or displays throughout a (somewhat large) house, I'd like to flesh out my knowledge so I know what I should look for if I need to find a consistent way to do so.
I might also be under the mistaken impression that remote sensors/displays/relays/motors are going to be much more complicated that it actually is. Lacking the most basic knowledge/what is generally feasible, I need to get my feet wet. I haven't started playing yet: my Arduino kit and sensor stuff won't arrive until tomorrow.
All of the walls in my house are completely open and I have have time to experiment.
Forget about how I would do it -- I don't know what I'm doing. How would you
do something like this?