Gears

Hello, all Im brand new to this and I have my very first controller on the way. A little breif back ground, so you know what your dealing with. LOL I work in the automation industry; however, Im more on the mechanical side of the bis Ive biult machines of much divercity from the ground up for about ten years and am now a field service engineer. I know a little bit about how this side of things work but I have many, many holes in my knowlege and will be in need of ALOT of help here. What my project intails so far is I will need to controll about 8 air actuated valves. These will have the DIN connecter plugs. I would like to set this up with an 8 channel or better relay board to switch the valves. So what would be the most cost effective and simplest way of doing so? I will need to input to the Netduino as well with a few different devices. Prox switches, a thermo couple, some manual buttons. E stop for instance. Id like things to be expandable incase I might need to add some stuff later on. Im in the very beginning of the design faze and this is one of the most important parts. So here I am Thanks in advance Gears Oh, just incase your wondering, my progect intails a small scale fully automatic biomass gasifier for residential. Just looking for a way to make this tech more practical.