I have purchased a 8 Channel 5V Solid State Relay Module Board.OMRON SSR 4 PIC ARM AVR DSP Arduino, from your Amazon bargains site. I am wondering if there is a diagram to connect this up. On the output side, which terminal is NO and which is NC? There is a set of terminals for the 8 inputs and then a separate ground, does this need to be connected to the common ground from the power supply?
The ground of the inputs goes to the ground of the Arduino. The 8 inputs go to 8 of the Arduino's outputs. Since you say it's a 5 V SSR board I presume it doesn't need series resistors, but don't quote me on that. Provide a link to the product's specs, and I'll see if I can confirm that.
NO and NC mean "Normally Open" and "Normally Closed", resp, on a relay with a change-over contact. There's a third contact, probably marked "COM", for "Common". If the relay isn't activated COM is connected to NC. If you activate the relay COM gets connected to NO instead.
I'd be surprised if the SSR had a change-over contact, though. If you have just 2 connections on the output side you have a normal open SSR. If your question means which of the connections goes to the phase and which goes to the load, then the answer is that it doesn't matter. But clarify your question, and provide more information/pictures of the module.