Wawa:
You can NOT power a Mega (~70mA) with ethernet shield (~160mA) directly from 12volt.
The onboard 5volt regulator will overheat and shut down (if you're lucky).
That is my concern with using the 12v supply
Wawa:
A 5volt cellphone charger (connected to the USB socket) is a good option.
But it all depends on what else you have connected.
Post a full diagram.
Leo..
A USB charge is not really an option, that is why I have the 9v supply
