12. The XBee

The XBee is another marvellous thing.  It is a wireless radio frequency transceiver which operates at the 2400-2483.5 MHz waveband.  This waveband doesn't require a licence.  You obviously need two of these so that they have something to communicate with.  There are different models, but the sort I bought from Adafruit was the 1mW model with wire antenna:

The Digi International XBee pin-out has a 2 mm separation, so you can't plug it directly into a breadboard, since the standard hole separation for breadboards is 0.1 inch.  So I got hold of the MaxStream XBee adapter, which comes in kit form, and when connected, looks after power and protection and provides LED indicators of power on, and transceiver activity handling serial data.  And of course, it has a 2 mm hole separation on the top, for plugging in the XBee, and 0.1 inch pin-outs suitable for the breadboard :

This shows the assembled adapter kit, before mounting the XBee.  This photo shows the 10-pin header on the left, protruding horizontally.  So that I could mount mine on a breadboard, I soldered my header so that it stuck out of the bottom of the board, ready for plugging into a breadboard.

Here is one of my XBees, complete with assembled adapter, mounted on a mini breadboard:

I'll cover the project details later, but suffice to say at this stage, that to get 2 XBees talking to one another, is a truly wondrous thing