My project has a seed studios ethernet shield attached to an UNO and that connects to a relay breakout board. I have a power supply that converts 110v to 9v @ 1amp it has no problem powering the arduino and relay but when the network shield is attached the red light indicating connection on the Ethernet shield does not light up.... if I power the project from a usb it works fine but I would rather have my power supply running the project attached to ground and vcc. It seems when anything is attached to the vcc port the Ethernet shield will not connect but when I plug it in via usb and reset the project it works flawlessly. I thought it was just the vcc port but if i try to tap into the power port instead I get the same issue... Any Ideas?
Your power supply is 9 volt at how many ma?
If you have a voltmeter, check the voltage on the Vin and 5v pins on the Uno.
I dont recall the rating for the power supply I threw away the casing a while ago i tested to see the draw and im pulling .660 A when testing the circuit. I am pulling 4.42V when testing the Vin and Vcc coming off of the ethernet shield
If Vin is less than 7 volts, you have a power problem.