Hi,
From the schematic you can see that the power input goes directly, and only, to an lm78l05acz voltage regulator.? The datasheet for that says it will take a maximum input voltage of 35VDC and and needs a minimum of 7VDC to provide a steady 5V to the arduino.? So the input voltage is pretty flexible, although I think most will be using either a 9V or 12V adapter supply (or batteries).
73,
Mark.
