This project has rather rigorous power supply requirements--it has analog,
digital, and power circuitry all running off the same 7.2V battery.
For the digital supply, you probably need 5V and ground supplies.
For the analog circuitry, it is convenient to have V+, V- and ground rails.
For the power circuitry, you can use the battery to directly power the
motor, however you will need a voltage supply higher than the batter
voltage in order to drive the power transistors in the h-bridge motor drive.
As a result, you may want to consider implementing regulated power supplies
of 0V, +5V, -5V, and 15V. Switched voltage regulators provide an
efficient way to step down, step up, or invert unregulated power supplies.
See the parts info page for possibilities.