w7qdm:
I'm not too familiar yet with Arduino. I don't think the software will be difficult for me, but the application I have in mind will require the use of at least 2 shields (relay cards) plus some dedicated signal condition circuitry. Do the shields just stack on top of each other? They could all get power and access to I/O pins, but what about other connections to these shields?
Dependent on your package size a pair of relay boards may suit you but as suggested a bank of 8 or 2 banks of 4 relays may provide a better path, I am currently working with a 4 relay shield for the uno the one I have is working but much cheaper in quality than the standalone units on their own control boards