Form the first moment I envisioned this I always wanted to use an Ethernet connection in order to communicate with the device. I followed the (very) easy path of using the enc28j60 with the arduino. As I didn't want to use a full arduino board on this project, I also wanted to design a custom board to house the micro-controller.

With these premises i projected a board with power supply, the micro, a LED and a relay. The Ethernet connection would be provided by a separate ready made board. All of this would be enclosed on a plastic box and placed under the floor.

For the board I ended up with this scheme:

And this resulted on this board:

All of this seems that it was all easy peasy.... but no...