Hello.I have arduino and ethernet w5100 shield with sd card and control my a/c.Can be converted to wireless to communicate with the modem router without network cable?With wifi shield?Thanks.
Convert what to wireless? The Ethernet shield? No that can't be converted to a WiFi shield. You can, however, plug it into a wireless access point or get yourself a WiFi shield.
If i want control 10 devices (a/c) for all house via wifi can i create arduino-wifi controllers for each device?From arduino webserver send wifi signal for each device(a/c, relays)....home automation with link 2.4 GHz...any ideas?
Yes, but it would be pretty expensive. If that's not a problem, then have at it. Otherwise, you might want to consider using cheaper wireless solutions to talk to the nodes from the base station.