ARDUINO NANO

ARDUINO NANO
 

Arduino Nano is a surface mount breadboard embedded version with integrated USB.
It is a small, complete, and breadboard friendly.
It has everything that Diecimila/Duemilanove has
(electrically)
with more analog input pins and onboard +5V AREF jumper. 
Physically, it is missing the power jack. 
The Nano will automatically sense and switch to the higher voltage source of power,
there is no need for the power select jumper.

Nano’s got the breadboard-ability of the Boarduino and the Mini+USB
with smaller footprint than either, so users have more breadboard space.
It’s got a pin layout that works well with the Mini or the Basic Stamp 
(TX, RX, ATN, GND on one top, power and ground on the other). 

Power

The Arduino Nano can be powered via the mini-B USB connection, 6-20V
unregulated external power supply (pin 30), or 5V regulated external power supply
(pin 27). 
The power source is automatically selected to the highest voltage source.