motors

Stepper motors can move back and forth and lock into fixed positions, or steps, around the axis.

Stepper motors are common in machines that require precise and stable movement, like 3D printers and CNC machines.

Usually you will connect a stepper motor to your microcontroller by means of a stepper motor driver board, which has all the circuitry for controlling the motor. Then for you to control the motor, you just need to provide power and a signal to trigger the motor's intended position.

Servo motors are an important part of many robotics projects. A servo can move to arbitrary positions within some range of motion, usually 180 degrees. You might think of them like mechanical elbows.

Most Arduino boards can only supply enough power to move very tiny servos (like the 9g variety for steering small RC vehicles) – and no more than one unless you are careful to move them one at a time. This is helpful for prototyping and debugging isolated parts of a larger robot before moving them off to a different circuit with external power.

Some inexpensive servo motors can be easily converted to continuous rotation motors with just a few minutes of work. What this means is that the PWM signal will control the speed and direction of your freely rotating motor instead of setting its position within an 180-degree arc. In other words, it becomes a simple DC motor with a control circuit conveniently built in.