What is a servo motor in simple terms?

A servo motor is a motor with a built-in position sensor and controller. You tell it a target angle and it drives itself there and holds it. That self-correcting feedback is what makes servos so easy and reliable for precise positioning.

How do you control a servo motor?

With a PWM (Pulse Width Modulation) signal. A 1.0 ms pulse means 0°, 1.5 ms means 90°, and 2.0 ms means 180°. You send that pulse about 50 times a second and the servo's internal controller drives the motor until it reaches the angle.

What is the difference between a hobby servo and a digital servo?

Hobby servos (SG90, MG996R) are cheap, analog, and update slowly — great for learning. Digital servos refresh many times faster and hold position more firmly under load, so they're used where precision and stiffness matter, at a higher price.

Can a servo motor rotate continuously?

A standard positional servo only sweeps about 0–180°. A 'continuous rotation' servo is modified so the signal sets speed and direction instead of angle — useful for driving small wheels, but you lose precise position control.

Servo Motors in Robotics

A servo motor is a motor packaged with a position sensor and a feedback controller. You send it a target angle as a PWM signal, and it drives itself to that angle and holds it. That built-in self-correction makes servos the easiest precise actuator for beginners — perfect for robot arms, grippers, and steering.

Servos are usually the first actuator people meet in robotics, and for good reason: cheap, forgiving, and controlled with a single signal wire. Let's see exactly how they work.

How does a servo motor work?

Inside the case sits a small DC motor, a gearbox, a position sensor (usually a potentiometer), and a control circuit. The circuit constantly compares where the horn is to where you told it to go, and drives the motor to close the gap. That's a closed feedback loop in a $3 package.

PWM: the language of servos

You don't set voltage — you set a pulse width. A pulse of 1 ms means "go to 0°", 1.5 ms means "90°", 2 ms means "180°". Send that pulse roughly every 20 ms and the servo holds the angle. Drag the slider below to feel it.

Pulse width (PWM signal)

Pulse: 1.50 ms → Angle: 90°

A servo reads the pulse width you send it: 1.0 ms means 0°, 1.5 ms means 90°, and 2.0 ms means 180°. Its built-in controller drives the motor until the horn reaches that angle.

Hobby servos vs digital servos

Hobby (analog) servos

The SG90 (a few grams, ~$2) and the metal-geared MG996R (~$5) are the classic starting servos. They plug straight into an Arduino and move with one line of code. Plenty good for arms, pan-tilt mounts, and learning.

Digital servos

Same idea, but the controller updates the motor far more often. The result: faster response and a much firmer hold against external force. You pay more, but for precise or load-bearing joints it's worth it.

When should you use a servo?

Reach for a servo when you need to hold a specific angle, don't need continuous spinning, and your loads are modest (roughly 0.5–20 kg·cm of torque). Think robotic arm joints, gripper fingers, camera gimbals, and steering linkages.

When not to use a servo

Need continuous high-speed rotation (wheels, propellers)? Use a DC or brushless motor. Need cheap precise positioning that holds firmly at rest without a sensor? A stepper motor may fit better — see our servo vs stepper comparison.