Arduino - Servo Motor

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

Arduino Servo Motor Wiring Diagram

Image is developed using Fritzing

How To Program

  • 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

Quick Steps

  • Connect Arduino to PC via USB cable
  • Open Arduino IDE, select the right board and port
  • On Arduino IDE, Go to File Examples Servo Sweep example
/* Sweep by BARRAGAN <http://barraganstudio.com> This example code is in the public domain. modified 8 Nov 2013 by Scott Fitzgerald http://www.arduino.cc/en/Tutorial/Sweep */ #include <Servo.h> Servo myservo; // create servo object to control a servo // twelve servo objects can be created on most boards int pos = 0; // variable to store the servo position void setup() { myservo.attach(9); // attaches the servo on pin 9 to the servo object } void loop() { for (pos = 0; pos <= 180; pos += 1) { // goes from 0 degrees to 180 degrees // in steps of 1 degree myservo.write(pos); // tell servo to go to position in variable 'pos' delay(15); // waits 15ms for the servo to reach the position } for (pos = 180; pos >= 0; pos -= 1) { // goes from 180 degrees to 0 degrees myservo.write(pos); // tell servo to go to position in variable 'pos' delay(15); // waits 15ms for the servo to reach the position } }
  • Click Upload button on Arduino IDE to upload code to Arduino
  • Arduino IDE - How to Upload Code
  • See the result: Servo motor rotates slowly about 180° in clockwise and counter-clockwise direction

Code Explanation

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

Video

incoming

Challenge Yourself

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

Additional Knowledge

  • The Servo library supports up to 12 motors on most 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 too many servo motors.

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

Arduino Servo Motor Extra Power

Image is developed using Fritzing

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. The negative pin of extra power source is connected to the GND pin of Arduino.

Alternative Servo Motors

The above code also works with the following servo motors:

Servo Motor on Commercial Products

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