I'm currently working on something similar. Data over a long distance between multipe arduino's.
Please check this tutorial where RS485 half-duplex is explained. http://real2electronics.blogspot.com/2009/09/arduino-and-rs485-english-version.html
This will work. One way is easy, letting the slaves send data back is more complicated, and at this time I can't help you out on that because I don't know.
What also could be an option is wireless. Please check this for a nice arduino wireless project.
I need to send multiple (three) varying voltages from one arduino to another
What exactly does this mean?
My take is that you have a fluctuating voltage at A that you want to be mimiced at B 400' away. Is that the case?
If so we need to know the amplitude of the voltages, accuracy required, and the frequency you'd like to have the updates working.
If not, "please explain" as one of our famous politicians once said.
BTW, is everyone around here called Rob?
bit more info. i am controlling three motors at long distances via three variable resistors on thumb sticks. the idea was to send the input of said resistors to the remote motors through one arduino(controller) to the other(Remote Operated Veichle) and looking for efficent ways of doing it, keeping inmind that all three may be active at once.. at the moment i am leaning towards using indivdual lines for each thruster and sending the resistor output directly to the rov arduino the converting into appropriate pulse to control the brushless motor esc
You only need one data wire.
Simply read the three pots and send their values as 6 bytes to the ROV. Then convert those values to whatever makes sense to drive the motors.
A simple protocol wouldn't go astray just in case, even if it's just a CRC or checksum as the 7th byte plus add some sanity testing of the data.
As for the physical layer, RS-485 would be the go, it's a balanced signal so make that two data wires.
thanks for your help on that one. sometimes it takes a different set of eyes