I'm searching for a shield (or a separate board) I can use to drive a (big) set of relays' coils with the output pins of the Arduino. I'm searching for something easy to deploy frequently for hundreds of relays on dozens of Arduinos.
I've got these relay boards that are really nice, compact and economical (you can see a small manual at http://formula9.net/files/8relaycard_manual.pdf); they have the electronics (simple transistor/diode circuit) to drive the coils of 8 relays (230V, 10A), so I can just connect the pins to the board and go.
What I'd like to find is a shield or board that takes the role of that amplifier circuit (for each pin), so that I can use external, heterogeneous relays (more powerful or less powerful).
Well, I'm thinking of using normal DIN-rail-mount relays, miniature 220V/6A or bigger 220V/16A, according to the loads I need to switch. The coils are usually 12V or 24V, and drain more than the Arduino pins can handle (40mA), so I need an interface circuit (basically a transistor, a protective diode and a couple of resistors, it's been well discussed here, or a Darlington pair IC that can drive all the coils at once). It's not difficult to build something like this from a prototype shield.
I was basically searching for an off-the-shelf shield. I have a (home automation) project in wich I need to drive many relays, preferably heterogeneous.
