Ok so I would need to attach one of these ( http://www.ecrater.co.uk/p/13965714/rs485-rs422-module-max485-interface?gps=1 ) to the master arduino board and also one to each of the children prominis?
This might be a stupid question however in other examples of doing similar things like this one Tinkering with Electronics...: Arduino and RS485 (ENGLISH VERSION) each of the arduino boards has been connected via usb. So does each board require being connected to a computer in some form or what I assume to be the case that I can connect a power supply to the prominis and only have the master connected to a computer?