It's pretty simple plugging the Arduino Ethernet to the DFRobot Relay, almost foolproof, but the ethernet port really causes a problem
with the 2.1 version. When they are plugged together, I apply power to the Arduino and the lights flash on the Arduino and the LED on the power supply flashes as well. If I apply power to the Arduino alone, no flashing. Looks to me like several pins on the Relay cant possibly make a proper connection to the Arduino. Most likely causing the flashing. Anyone else have this issue? Any suggestions? Thanks