Servo motors (Figure 1-4) will be moving the wheels of our robot. The most usual type of servos have limited rotation. They are used when you need to turn the motor to a specific angle. In our robot, we only need to control speed and direction. And, of course, the motor needs to be able to turn freely. Continuous rotation servos are made for this. Almost any servo can be modified to continuous rotation, but it’s easier to buy a ready-made version.

Figure 1-4. Continuous rotation servos

The Parallax (Futaba) continuous rotation servo is perfect for our needs. It has an external potentiometer adjustment screw, which allows identical centering of two servos effortlessly. You’ll notice how handy this is later, when we program the movements for the robot.