nethyr:
As I plan my first basic robot I've run across people discussing motor shields a few times. I've seen some builds that don't use them and some that do. I believe I understand what a motor shield is capable of. What I'm unsure of is exactly what I can do with a motor shield that I can't do without one, or in what situations I would need one and which I wouldn't. I've done some rudimentary part testing and my Arduino Uno itself seems to be capable of what I need at a glance, though I'm sure I'm missing something.Thanks for your patience with a newbie!
Well most DC motors are higher current drawing devices so you need some kind of motor driver interface between the arduino and the motor so that the motor has the proper voltage and current required to operate but still be controllable by the Uno board. This motor driver interface can be as simple as a single transistor and a couple of resistors or as complex as a full H-drive interface that allows for forward and reverse rotation as well as variable speed. And whatever motor interface circuitry you want or require can be mounted externally on it's own PC board or can be built in the form of a 'shield' board for easier mounting with an arduino board, which can simplify wiring. So lots of options, but most newcomers like the ease of using a motor shield when first starting out. Just be sure whatever motor shield you select is rated for the voltage and current requirements of the motor you select. Many motor shields will support two motors while some only one motor.
Pololu has many standalone motor controller boards and is a pretty popular supplier of such, but don't know if they have an in the 'shield' form factor.
Good luck;
Lefty