MichaelMeissner:
If you aren't running the cat5 cables through anything that expects to deal with IP packets like a router (i.e. just using the cable as a convenient way to string 8 wires), for short runs, you could just connect the wires to each pin.
That's what I was thinking -- just using cat5 as a type of common wire with 8 wires. For digital sensors only though, right? If the sensor is an analog sensor, the signal won't make it 100m, right? Or is there something that can be used to repeat/amplify (some sort of capacitor/diode/something else) an analog signal? Is there a reasonable (known) limit that even digital sensors would fail at? 10ft? 50ft? 200ft?
MichaelMeissner:
I suspect for longer runs, you want to add something that can deal with check-summing and resend the packets if there are errors. You could use some cheap microprocessor on the remote end to do checksums, etc.
What I'm trying to find out, is what is the minimum electronics needed on the remote end beyond the sensor itself? You mentioned a checksum, what type of microprocessor should I research? An ATTiny?
MichaelMeissner:
Note, the problem of point to point links like this is only one system can control them. You can of course log onto the central system to control the Arduino. It would be more flexible (and costly) to have each controller be a separate entity that has its own network IP address.
The idea behind having the Arduino(s) in a central location is that they can be really beefy Arduino(s) with Ethernet, logging stuff to cosm.com, and displaying appropriate data on one of the four remote LCD displays throughout the house.
The patch panel that I'm looking at is the Leviton that use the QuickPorts like the ones you linked from Radio Shack. Thanks for the link to the RJ-45 jack on Sparkfun, I hadn't seen that yet.
Thanks for pointing out the "UNO" link. I wouldn't have seen it wasn't an Arduino-branded Uno, if it hadn't been pointed out. If it does work like a real Arduino Uno, that's a great deal. I'm hoping that the cost for the electronics at the remote end can be done a lot cheaper.
Has anyone here ever used an ATTiny (any model) with an RS485-type technology with a sensor or LCD display or to control a solid state relay or drive a motor, at a (not insignificant) distance from the Arduino it is connected to?