Plug Arduino into wall outlet

Hi there. I've recently started on an Arduino project and have now come to the point where I would like to take the next step.

That is: to power the Arduino directly through a regular US 120 volt wall outlet without using the regular adaptor (that is by connecting a plug to the case in which the Arduino is placed and then plugging that case into the outlet).

E.g. like this Apple adapter (without the USB-charging outlet - the white casing being casing for the Arduino, WiFi shield etc):

I'm using an Arduino Uno and have been looking for online resources guiding one through the steps, but without any luck. Most tutorials go through the steps of creating an Arduino-controlled outlet, and not a pluggable Arduino.

I originally thought of disassembling an iPhone/iPad USB-charger and then power the Arduino from that, but am not sure on how to proceed. Therefore if anyone know of any guides, or can point me in the right direction I would gladly appreciate it.

Thanks in advance.

You could build a capacitive voltage divider but that is not advisable since it gives you no galvanic insulation from the mains voltage and thus is a safety hazard. Galvanic insulation is achieved by trnsformers. This can either be traditional transformers followed by a linear or switching regulator or a primary switching power supply which is what most wall adapters are. It should not be that hard fitting a small switching adapter and say a arduino nano or similar into a suitable case