Hi, I just wanted to know what is the maximum distance between two arduinos so the serial communication still works well. (the environment is a house with all the normal electronic devices (TV, laptop, WiFi, etc...). Thanks :)
What data rate do you need? Are you going to try to level the signals at TTL levels or use a converter chip for RS422, RS232, etc?
Data rates of up to 100K bits / second and distances up to 4000 Ft. can be accommodated with RS422. (http://www.rs485.com/rs485spec.html)
I suspect if you used shielded single pair wire at lower baud rates you would have no problem running the distance within a single house. We use to run up to 200 ft at 9600 baud using RS-232 at work without problems, but TTL serial using lower voltage may not be able to run as long and/or as fast, but in the same general magnitude I bet.
User at least a twisted pair, like bell wire rather than just audio cable or better still network cable, but costs more.
How far and how fast do you want to go is more the question ?
At one job I had we ran serial data at 2048 baud with an open collector driver pulled up to 12V. This was good for at least 1Km.