I've used small high speed dc motors by just wiring them to a battery and potentiometer, but i've heard a lot of talk in these forums about motor controllers and h-bridges, and I don't fully understand when they are needed.
My question is: I want to run a geared motor like one of these:
Do I need a motor controller, arduino motor shield, or h-bridge to do so? Or can I just wire up a 6/12 volt power supply and use a pot to control the speed? I realize I won't be able to run it in reverse this way. Would I be able to just use a switch to reverse the polarity and run it forwards/backwards?