I'm looking to automate my home and want something that will not consume any energy when not in use. From what I gather from the X10 and similar systems are that each wall unit will need to be in standby mode 24/7 in order to receive signals. The energy consumption from each module is probably not enormous, but adds up. In fact, if you consider all the systems (TVs, VCRS, battery chargers, etc) in every household around the world that are in standby mode, when they could be off, it adds up to a lot of wasted power consumption.

I will be rewiring my home soon, and plan to add a serial port or other interface to each room in the house. So automation over the power lines is not required. I'm hoping a solution already exists. If not, I have an idea for how it will work:

Each room unit would have a 4-pin interface to the central computer: 1) Power, 2) Ground, 3) Data, 4) Wakup. The central computer would supply the power and all units would be off by default. Whenever the central computer sends a command to a new unit it would send enough power in the wakeup line to power up all units momentarily. Each unit would check if the command was for it (by a unique serial number) and either execute the command and stay online to interface with the system or turn off until woken again.

This type system would be perfect for a energy conserving home. You could have the system power down your TV and other standby systems, without the unit needing to stay online to receive commands.

Is there already a system and/or interface that does this? Can somebody recommend implementation ideas? What sort of data interface should I use to communicate with each unit over a single wire (RS485)? Can I send power over the data line to cut the interface down to a 3-pin system? Iím just a novice electronics hobbyist and can use all the advice you have. Iím a software engineer by trade and know basic electronics (learning more all the time) and how to use microcontrollers.