Option 1 - one controller say 1284 based, with cat5 wiring going to sensors, LCD display, relays and such.
Option 2 - four tiny85 based mini controllers, spread out to different locations, with short thermostat wires going to the peripherals. They'd be connected over I2C to exchange data.
Price-wise, the mighty is close to the four tinys, wiring is similar in cost, so that's not my concern.
I am wondering about electrical interference and so on.
A central controller would have sensors, like photocells, temperature, humidity and air pressure connected with probably cat5. Relays installed in the garage would be close to power cables and the opener. At the front of the house there would be PIR motion sensors to turn the lights on. Inside there would be an LCD and a couple of buttons maybe.
With the tiny layout I could probably locate them close to the sensors, like one on the roof, for the weather vane and photocells, one at the front for the motion sensors, one in the garage for relays and one inside for the LCD. Thermostat wire might be OK to the sensors and cat5 back to the other tinys.
What do you guys think? Pros and cons for both layouts, anything else?
Thank you.
Option 1:
Long wires can be a problem for some/most) sensors. I think a network is better suited.
Option 2:
First, don't use I2C. It's only designed for short wire lengths. For a stable network use something like RS485.
And you can use the ATtiny but a Arduino Pro Mini is so cheap, I would use that. It's already pre build, had a voltage reg already and has all peripherals like I2C (for sensors?) and serial (for the network/rs485?).
Why not just use the ESP8266 to collect data? The are cheap (less than 2$ for a breakout board), wireless and can be used with the Arduino IDE. The ESP8266s can log the data to a server or website (I've used Thingspeak and Blynk), and another can pull down this data and show it on an LCD screen or on your smart phone or tablet, using Blynk.
Yep, that's an option. My main thought about mentioning the ESP8266 is that you don't need another microcontroller. It got Wifi capabilities and GPIOs. The only "down side" is that it runs at 3.3v, and you'll have to make your own break out board.
Actually, I've designed an Internet of Things board for the ESP8266! I sent it to the board manufacturer last night The idea was to make it small (5x5cm), have both 3.3v and 5v in the board, and a prototype area. you can solder sensors directly to the board, and put it in a small enclosure. I'm planning to add sensors around the house using these boards (all the corners are rounded. The gerber viewer doesn't understand that)
The idea was to make it small (5x5cm), have both 3.3v and 5v in the board, and a prototype area. you can solder sensors directly to the board, and put it in a small enclosure. I'm planning to add sensors around the house using these boards 
(all the corners are rounded. The gerber viewer doesn't understand that)