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Arduino - Servo Motor

In this tutorial, we are going to learn how to use the servo motor with Arduino. In detail, we will learn:

How servo motor works
How to program Arduino to control servo motor
How to program Arduino to control the speed of servo motor
How to provide the extra power for high-torque servo motors.

Hardware Required

1	×	Arduino UNO or Genuino UNO
1	×	USB 2.0 cable type A/B
1	×	Servo Motor
1	×	Jumper Wires
1	×	(Recommended) Screw Terminal Block Shield for Arduino Uno
1	×	(Recommended) Breadboard Shield For Arduino Uno
1	×	(Recommended) Enclosure For Arduino Uno

Or you can buy the following sensor kits:

1	×	DIYables Sensor Kit (30 sensors/displays)
1	×	DIYables Sensor Kit (18 sensors/displays)

Please note: These are Amazon affiliate links. If you buy the components through these links, We will get a commission at no extra cost to you. We appreciate it.

About Servo Motor

Servo motor is a component that can rotate its handle (usually between 0° and 180°). It used to control the angular position of the object.

Pinout

The servo motor used in this example includes three pins:

VCC pin: (typically red) needs to be connected to VCC (5V)
GND pin: (typically black or brown) needs to be connected to GND (0V)
Signal pin: (typically yellow or orange) receives the PWM control signal from an Arduino's pin.

Servo Motor Pinout

How It Works

This section is the in-depth knowledge. DON'T worry if you don't understand. Ignore this section if it overloads you, and come back in another day. Keep reading the next sections.

After connecting VCC pin and GND pin to 5V and 0V, respectively, we can control the servo motor by generating proper PWM signal to signal pin.

The angle is determined by the width of PWM signal.

Datasheet of the servo motor provides us the following parameters:

Period of PWM (PERIOD)
Minimum width of PWM (WIDTH_MAX)
Maximum width of PWM (WIDTH_MIN)

These parameters are fixed in Arduino Servo library. We do NOT need to know the value of parameters.

The angle is determined as follows:

If PWM's width = WIDTH_MIN, the servo motor rotates to 0°.
If PWM's width = WIDTH_MAX, the servo motor rotates to 180°.
If PWM's width is between WIDTH_MIN and WIDTH_MAX, the servo motor rotates to angle between 0° and 180° in proportion.

How Servo Motor Works

Arduino - Servo Motor

Some of Arduino pins can be programmed to generate PWM signal. We can control the servo motor by connecting the servo motor's signal pin to an Arduino's pin, and programming to generate PWM on the Arduino's pin.

Thanks to Arduino Servo library, controlling servo motor is a piece of cake. We even do NOT need to know how servo motor works. We also do NOT need to know how to generate PWM signal. We JUST need to learn how to use the library.

Wiring Diagram

You might encounter wiring diagrams online that depict a connection from the VCC pin of a servo motor directly to the 5V pin of the Arduino board, as shown below. While this approach may work, it is strongly discouraged due to the potential risk of damaging the Arduino board.

Arduino Servo Motor Wiring Diagram

This image is created using Fritzing. Click to enlarge image

Instead, to safeguard your Arduino board, we strongly recommend using an external power supply for the servo motor. The wiring diagram below illustrates how to connect the servo motor to an external power source.

Arduino servo motor external power supply wiring diagram

This image is created using Fritzing. Click to enlarge image

Please ensure that you connect the GND of the external power supply to the GND of the Arduino board. Don't overlook this crucial step for proper operation.

How To Program For Servo Motor

Include the library:

#include <Servo.h>

Declare a Servo object:

Servo myServo;

If you control more than one servo motors, you just need to declare more Servo objects:

Servo myServo1; Servo myServo2;

Set the control pin of Arduino, which connects to the signal pin of the servo motor. For example, pin 9:

myServo.attach(9);

Lastly, rotate the angle of the servo motor to the desired angle. For example, 90°:

myServo.write(90);

Arduino Code

/* * Created by ArduinoGetStarted.com * * This example code is in the public domain * * Tutorial page: https://arduinogetstarted.com/tutorials/arduino-servo-motor */ #include <Servo.h> Servo servo; // create servo object to control a servo void setup() { servo.attach(9); // attaches the servo on pin 9 to the servo objectư servo.write(0); // rotate slowly servo to 0 degrees immediately } void loop() { for (int pos = 0; pos <= 180; pos += 1) { // rotate slowly from 0 degrees to 180 degrees, one by one degree // in steps of 1 degree servo.write(pos); // control servo to go to position in variable 'pos' delay(10); // waits 10ms for the servo to reach the position } for (int pos = 180; pos >= 0; pos -= 1) { // rotate from 180 degrees to 0 degrees, one by one degree servo.write(pos); // control servo to go to position in variable 'pos' delay(10); // waits 10ms for the servo to reach the position } }

Quick Steps

Connect Arduino to PC via USB cable
Open Arduino IDE, select the right board and port
Copy the above code and open with Arduino IDE
Click Upload button on Arduino IDE to upload code to Arduino

Arduino IDE - How to Upload Code

See the result: Servo motor rotates slowly from 0 to 180° and then back rotates slowly from 180 back to 0°

Code Explanation

Read the line-by-line explanation in comment lines of code!

How to Control Speed of Servo Motor

By using map() and millis() functions, we can control the speed of servo motor smoothly without blocking other code

/* * Created by ArduinoGetStarted.com * * This example code is in the public domain * * Tutorial page: https://arduinogetstarted.com/tutorials/arduino-servo-motor */ #include <Servo.h> Servo myServo; unsigned long MOVING_TIME = 3000; // moving time is 3 seconds unsigned long moveStartTime; int startAngle = 30; // 30° int stopAngle = 90; // 90° void setup() { myServo.attach(9); moveStartTime = millis(); // start moving // TODO: other code } void loop() { unsigned long progress = millis() - moveStartTime; if (progress <= MOVING_TIME) { long angle = map(progress, 0, MOVING_TIME, startAngle, stopAngle); myServo.write(angle); } // TODO: other code }

Video Tutorial

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Challenge Yourself

Use the servo motor to do one of the following projects:

Controlling the position of a servo motor using a potentiometer. Hint: Refer to Arduino - Potentiometer.
Automatically opening/closing the dustbin. Hint: Refer to Arduino - Ultrasonic Sensor.

Additional Knowledge

The Servo library supports up to 12 motors on Arduino UNO and 48 on the Arduino Mega.
Power from 5V pin of Arduino maybe NOT enough for servo motor in one of the following cases:

Using a high-torque servo motor, which can carry a high-weight thing.
Using many servo motors.

In these cases, we may need to provide an extra power source for servo motors.

Arduino Servo Motor Extra Power

This image is created using Fritzing. Click to enlarge image

As we can see in the above diagram, the VCC pin of servo motor doest NOT connect to the 5V pin of Arduino. It connects to the positive pin of an extra power source.

Please note that:

Do not connect the positive pin of extra power source to 5V pin of Arduino.
Must connect the negative pin of extra power source to the GND pin of Arduino.

Function References

map()

The Best Arduino Starter Kit

See the best Arduino kit for beginner

See Also

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