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How to use a Servo Motor

What is a Servo Motor?

A servo motor is a rotary actuator that allows for precise control of angular position, velocity, and acceleration. It is commonly used in robotics, CNC machinery, conveyor belts, and various automation systems. A servo motor works by receiving a control signal that represents a desired output position, and it uses an internal feedback system to adjust the motor’s movement accordingly. We often use RC (Radio-Controlled) Servo Motors in physical computing.

Types of Common RC Servo Motors

Servo Type Rotation Range Control Type Common Use
Regular (Standard) Servo 0°–180° (sometimes 270°) Angular position (PWM) Arms, steering, gimbals
Continuous Rotation Servo 360° (infinite) Speed & direction (PWM) Wheels, drive systems
Mini / Micro Servo Depends on type (limited or continuous) Same as regular or continuous Small robots, drones, model planes

Using a PWM Driver

You may come across many online tutorials that show how to control servo motors directly without a PWM driver. While this method is possible, it’s not the most reliable—especially when working with multiple servos. Sooner or later, you’re likely to run into issues, often related to power management and signal stability.

For this reason, in this tutorial, we’ll be using the Seeed Studio 16-channel PWM driver for more stable and scalable control. You can also use other similar PWM driver boards depending on your needs.

Wiring

  1. 5V Power Supply on the Left:
    • + to 5V
    • - to GND
  2. i2C to Arduino on the Right:
    • GND to GND
    • 5V to 5V
    • SCL to SCL
    • SDA to SDA
  3. Servo to PWM Out:
    • Plug in the servo, where the black wire goes to the GND

Library

Grove-16-Channel_PWM_Driver-PCA9685 library will be used.

We have a tutorial on how to install a library here.

Getting started - Regular Servo

This code is getting the eight servo motors to rotate to 0 degrees and then 90 degrees, one by one.

#include "PCA9685.h"
#include <Wire.h>

ServoDriver servo;

void setup()
{
    // join I2C bus (I2Cdev library doesn't do this automatically)
    Wire.begin();
    Serial.begin(9600);
    servo.init(0x7f);
}

void loop()
{
    // Drive 8 servos in turns
    for (int i = 1; i < 9; i++)
    {
        servo.setAngle(i, 0);
        delay(1000);
        servo.setAngle(i, 90);
        delay(1000);
    }
}

Getting started - Continuous Servo

Since a continuous servo is controlled by a pulse, the ‘degree’ values work differently. Values like 0, 90, and 180 don’t represent angles; instead, they typically control rotation direction and speed — for example, 0 means full speed clockwise, 90 means stop, and 180 means full speed counterclockwise.

The below code is getting the servo motor 1 rotates clockwise for 1 second and stop for 1 second.

#include "PCA9685.h"
#include <Wire.h>

ServoDriver servo;

void setup()
{
    // join I2C bus (I2Cdev library doesn't do this automatically)
    Wire.begin();
    Serial.begin(9600);
    servo.init(0x7f);
    
    //Most continuous servo motors' pulse width is 900-2100
    servo.setServoPulseRange(900,2100,180);
}

void loop()
{
    // Drive 8 servos in turns
        servo.setAngle(1, 0);
        delay(1000);
        servo.setAngle(1, 90);
        delay(1000);

}
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