Thank-you Jeff for your comments.
You are right, the sensors work with one-wire protocol, not I2C. I'll correct it.
I used two arduinos because the number of I/O pin of one was not enough for an LCD, datalogger, relay control and Ethernet card.
The end product of our "ARETHA Project", submitted to indiegogo crowdfunding platform, would be the production of a tutorial, a web site and a forum.
We think that experiences of many ARETHA makers, around the world, could be useful to improve this device.
You can follow us also on FB:
https://www.facebook.com/ARETHAproject
Paolo