How to Interface a Servo Motor with Arduino

In the world of electronics and robotics, servo motors play a crucial role in controlling mechanical movements precisely. In this blog post, we'll delve into the basics of interfacing a servo motor with an Arduino board. Whether you're a beginner or an experienced enthusiast, this step-by-step guide will help you understand the fundamentals of servo motor control and how to integrate it with an Arduino for your projects.

You can also find other such Arduino tutorials and projects on our website.

The components which we will require for this project are

1. Arduino Uno
2. USB cable
3. Servo Motor SG90
4. Potentiometer 10k ohm
5. Jumper wires

SG90 Servo Motor Pinout

GND Ground (Brown Wire) – This is the ground pin.

VCC +5V (Red Wire) – Voltage is supplied to the servo motor through this Pin.

Control (Orange Wire) – Through this wire, Position control signals are received via PWM.

Servo Motor Working

A servo motor receives PWM (Pulse Width Modulation) signals to determine its angle of rotation. The PWM signal is a square wave with a variable duty cycle, where the width or duration of the high signal (the "on" time) corresponds to a specific angle. This signal is usually generated by a microcontroller, such as an Arduino.

When the PWM signal is fed to the servo motor's control input (usually the orange or yellow wire), the motor's control circuit interprets it as a command to move to a particular angle. The control circuit measures the duration of the high part of the PWM signal, which corresponds to the desired angle. This duration is typically in the range of 1 to 2 milliseconds.

The control circuit then compares this measured duration with the center position (typically 1.5 milliseconds) and adjusts the motor's shaft to move towards the desired angle. If the duration of the high part of the PWM signal is shorter than the center position, the motor turns in one direction; if it's longer, the motor turns in the opposite direction.

The servo motor continuously adjusts its position to match the incoming PWM signal. As the duty cycle of the PWM changes, the motor's shaft rotates accordingly. This closed-loop control mechanism ensures that the motor accurately follows the input signal, allowing for precise and repeatable angular positioning. In essence, the servo motor's responsiveness to PWM signals enables it to execute controlled movements in various applications, from opening and closing doors to steering remote-controlled vehicles.

Commonly asked questions about Servo Motors

How does a servo motor differ from a regular DC motor?

Unlike a regular DC motor, a servo motor features a closed-loop control system with feedback mechanisms like potentiometers or encoders. This enables precise position control and makes it stop at a specific angle, whereas a regular DC motor doesn't inherently have this level of precision.

Why is my servo jittering or not moving smoothly?

Jittering or erratic movement might be due to power issues, noise in the signal, or mechanical restrictions. Ensure a stable power supply, use proper wiring, and ensure the servo isn't mechanically constrained.

Can I modify a servo motor for continuous rotation?

Yes, some servo models can be modified for continuous rotation by disconnecting the internal feedback mechanism and adjusting the control circuitry. This essentially turns the servo into a geared DC motor with position control disabled.

Circuit Diagram of Interfacing Arduino with Servo Motors and Potentiometer

The below circuit diagram shows how a servo motor can be controlled using a potentiometer.

Connect the red wire (VCC) of the servo motor to the 5V pin on the Arduino.

Connect the brown or black wire (GND) of the servo motor to the GND pin on the Arduino.

Connect the orange or yellow wire (Signal) of the servo motor to a digital PWM pin on the Arduino.

Connect the positive end of potentiometer to 3.3V pin of Arduino

Connect the GND end to the GND pin of Arduino

Connect the signal pin to A0 pin(or any analog input pin)

Here’s a pinout of the potentiometer for reference

Programming Arduino to Control Servo Motor

The below code initializes a servo motor on pin 5, reads the analog value from a potentiometer on A0, maps that value to an angle between 0 and 180 degrees, and continuously updates the servo's position based on the potentiometer's value. The small delay aids in smooth movement of the servo motor.

Here's the line by line code explanation. You can also find the complete code in the absolute bottom of the blog.

#include <Servo.h>

This line includes the necessary library "Servo.h," which provides functions to control servo motors using the Arduino.

Servo servoMotor;

Here, you're declaring an object named servoMotor of the Servo class. This object will be used to control the servo motor connected to your Arduino.

void setup() {

The setup() function is a special function that is executed only once when the Arduino board is powered on or reset.

  servoMotor.attach(5);
}

Inside the setup() function, you're using the attach() method of the servoMotor object to connect the servo motor to digital pin 5 on the Arduino. This establishes the communication between the servo motor and the Arduino.

void loop() {

The loop() function is another special function that contains the main code to be executed repeatedly.

  int potValue = analogRead(A0);

Inside the loop() function, you're using the analogRead() function to read the analog value from analog pin A0. This value is then stored in the variable potValue.

  int servoAngle = map(potValue, 0, 1023, 0, 180);

Here, you're using the map() function to convert the analog potValue (ranging from 0 to 1023) to a desired servo angle range (0 to 180 degrees). This new value is stored in the variable servoAngle.

  servoMotor.write(servoAngle);

The write() method of the servoMotor object is used to set the servo motor's angle to the calculated servoAngle.

delay(15);
}

A small delay of 15 milliseconds is added using the delay() function. This short delay helps ensure smoother servo motor movement and reduces jitter.

Demonstration of the Project

Here’s how the project output looks like

Projects using Arduino