The Arduino nano is a very nice board, it uses exactly the same microcontroller as the Arduino Uno, all of its I/O come out to headers, it uses a mini usb and its small size make it ideal for projects where space maybe an issue. From a pricing point of view you can get them slightly cheaper than an Arduino Uno although there is not much in it.
There are a couple of minor problems though, if you have a collection of shields for your Arduino Uno like I do then using these with a nano can be tricky an additional issue that as the nano is USB powered then there is a lack of power available due to the amount available through the USB bus and also the limitation of the on board voltage regulator. The nano has no external power adaptor like the Uno so you can’t put in say 9v.
Luckily there are a couple of solutions, what you need to buy is a Nano-Uno shield adaptor. Here is a picture of one that I bought called the Nano-Uno Shield adaptor by OPEN-Smart
As you can see there are coloured connectors for the shield, you can also see the power connector fitted so you can use an external supply. Headers are supplied which could be populated but depending on the size of these headers then they may be close to shorting on a shield if fitted, double check if you want to fit these.
One little drawback is that A6 and A7 do not come out to headers so you lose that extra functionality on the Arduino Nano
You can get one of these useful boards for under $10
|Arduino Nano||USB Nano V3.0 ATmega328P CH340G 5V 16M Micro-controller board|
|Nano to Uno Shield adaptor||Nano Shield Nano IO Expansion Adapter Board with Regulator / Fuse|
– Dedicated to the Arduino Nano board and other compatible board
– Compatible with the pin definitions of the Arduino UNO R3
– Onboard 500mAh resettable fuse to protect power supply from the USB port and the DC jack at the same time.
– Leads out GND, 5V pins, UART serial interface, I2C interface and Arduino Uno I/O connections
– Onboard 5V and 3.3V voltage regulator circuit.
– Onboard DC jack socket and it can be powered by an external battery.
– Working voltage: 5V
– Working current: 500mAh (Max)
– External input voltage: 7-12V DC