The jrk 21v3 motor controller is a highly configurable brushed DC motor controller that supports four interface modes: USB, logic-level serial, analog voltage, and hobby radio control (RC). The controller can be used with feedback for closed-loop speed or position control, or it can be used without feedback as an open-loop speed control. The continuous output current is approximately 3 A in the recommended operating range of 8–28 V, with derated performance down to 5 V and transient protection to 40 V.

More info:http://www.pololu.com/catalog/product/1392