SparkFun TOL-08639 USB to 5.5mm Barrel Jack Adapter
This is a simple cable that adapts from a USB port to a 5.5×2.1mm barrel connector, center positive. This cable allows the user to use a USB port on a computer, laptop, or on our cigarette power supply to provide our development boards with 5V.
The USB specification limits current consumption to a max of 500mA from a USB port but this is more than enough to run a simple development board.
Cable length is 3 feet.