Our example used a common 3-wire, 180-degree angular servo. While this is a very common type of servo, there are other variations as well, including continuous rotation servos, servos with more than three wires, and special purpose servos:
- Continuous rotation servos: Have 3 wires and work on the same PWM principles as a 3-wire angular servo, except the PWM pulse width determines the rotational direction (clockwise/counter-clockwise) and speed of the servo.
Due to their internal control circuitry and gearing, continuous rotation servos are a convenient low-speed/high-torque alternative to a DC motor and H-Bridge controller (which we will be covering in the next section).
- 4-wire servos: These come with one set of three wires and a fourth loose wire. This fourth wire is an analog output of the servo that can be used to detect the angle. It's useful if you need to know your servo's resting angle when you start your program.