Motor drivers are the simplest modules in the sense that all they do is provide power amplification for low-level control signals (e.g. PWM and direction) supplied by the user; on the other hand, that means that the master device to which the motor driver is connected must take care of the low-level, resource-consuming signal generation.
Motor controllers are motor drivers with additional intelligence: an on-board microcontroller generates the low-level signals and presents the user with higher-level interfaces and commands. For example, our dual serial motor controllers allow two DC motors to be controlled by a single serial line, and the master controller simply issues commands only when the speeds of the motors should be changed. Other motor controllers are even more complex, incorporating advanced acceleration commands, current sensing, feedback-based control, and more.
RC servo controllers are quite different from the other two kinds of modules since they are made specifically for radio control (RC) hobby servos, which have built-in power circuitry. RC servos are popular because they are low-cost packages that include a motor, gearbox, and control circuitry with feedback, and they are often a compelling choice for projects that include many degrees of freedom, such as robot arms and walking robots. RC servo controllers are interfaces between a primary controller (such as a computer or microcontroller) and the many servos, which can become a burden for the primary controller to control directly. Features to look for in a servo controller include how many servos it can control, the resolution and range it can support (our servo controllers support 5000 positions over a range that exceeds what any servo can achieve mechanically), and extra control options such as speed control (sometimes referred to as ramping) and the ability to disable servos that are not in use.