Okay, I have structured cabling so easy to drop network where needed. You have peeked my interest - any more details, or would it just be as practical to use one of the off the shelf network to IO boards available now...
The modules have 8 digital inputs, 8 digital outputs, 8 1-wire temperature ports and 4 analogue inputs. Separate termination modules are used to add relays, opto-coupling of DI's, conditioning for analogue inputs and termination for 1-wire sensors. There's also a couple of serial ports, again termination modules can be used to turn these into RS232 or RS422 ports. Power is 12VDC and the network connection is 10bT. The Microchip IP stack compiles for it, using a custom BSP and the protocol I use is an encrypted UDP protocol between the Linux server and the remotes. On the Linux server there is a custom event manager that manages the queue of incoming and outgoing events to and from the remotes, and interfaces with the database. The web system interfaces with the database as well.
I can put up some circuits and also have a PCB (100mm x 100mm) for it.
Hmm, most tempting. What I'm thinking at the moment is:
- Analogue input x 2 for the temperature probes
- Mains switching ouput x1
But within 4 meters of this is a 6 way irrigation controller that could be made controllable from the center. So adding in a 6 way 24v rated switching would cover that. Would be good to also pull in the rain sensor (1 digital input).
I'd really like to get all this controlled from a dedicated small box PC with the Comfort and CBus tie in - currently everything including the kitchen sink is running on the one box (Samba, email, dns cache, web proxy, spam assassin, etc).
The remote I have in the tank room monitors the rainwater water tank levels and also the HWS temperatures, external light sensor and controls a 4-way irrigation system (4 24VAC solenoids on a manifold). The 1-wire DS1820B probles are a very easy option for temperature sensing, which was why I added the 8 1-wire ports to the module. The module itself also has a temperature sensor onboard, so the local temperature can be monitored inside the box. As far as switching loads, that will depend on the relays you end up using. The module outputs are open-collector 1A transistors, which is usually plenty for controlling a relay. The external termination modules are used for this purpose.
That's what I do with the Linux server that runs on the home network. It serves email (with spamassassin), dns caching, local intranet, media server (audio and video), svn repositories, samba drives, databases fro my electronic parts cataloging and BOM system, event management and control/monitoring system. External access is also allowed via SSL with client certs, so when I'm overseas I can check up on things or get access.