Servo Motors

What is a Servo Motor?

A servo motor is a rotary actuator that allows precise control of angular position. Unlike regular motors, servos can be commanded to move to a specific angle.

Types of Servos

SG90 Servo Specifications

Connecting a Servo

Pin Connections

Connection Diagram

Arduino          Servo
Pin 9    ------  Orange (Signal)
5V       ------  Red (VCC)
GND      ------  Brown (GND)

Using the Servo Library

Arduino has a built-in Servo library:

#include <Servo.h>
Servo myServo;
void setup() {
  myServo.attach(9);  // Pin 9
}
void loop() {
  myServo.write(0);    // Position 0°
  delay(1000);
  myServo.write(90);   // Position 90°
  delay(1000);
  myServo.write(180);  // Position 180°
  delay(1000);
}

Key Servo Functions

Basic Example: Sweep

Make the servo sweep back and forth:

#include <Servo.h>
Servo myServo;
int pos = 0;
void setup() {
  myServo.attach(9);
}
void loop() {
  // Sweep from 0 to 180
  for (pos = 0; pos <= 180; pos += 1) {
    myServo.write(pos);
    delay(15);
  }
  
  // Sweep from 180 to 0
  for (pos = 180; pos >= 0; pos -= 1) {
    myServo.write(pos);
    delay(15);
  }
}

Controlling Servo with Button

Add buttons to control servo position:

#include <Servo.h>
Servo myServo;
int buttonUp = 2;
int buttonDown = 3;
int currentPos = 90;
void setup() {
  myServo.attach(9);
  pinMode(buttonUp, INPUT_PULLUP);
  pinMode(buttonDown, INPUT_PULLUP);
}
void loop() {
  if (digitalRead(buttonUp) == LOW && currentPos < 180) {
    currentPos += 5;
    myServo.write(currentPos);
    delay(50);
  }
  
  if (digitalRead(buttonDown) == LOW && currentPos > 0) {
    currentPos -= 5;
    myServo.write(currentPos);
    delay(50);
  }
}

Project: Distance-Controlled Servo

Control servo position based on distance sensor:

#include <Servo.h>
Servo myServo;
const int trigPin = 9;
const int echoPin = 10;
int getDistance() {
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
  return pulseIn(echoPin, HIGH) / 29 / 2;
}
void setup() {
  myServo.attach(6);
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
}
void loop() {
  int distance = getDistance();
  
  // Map distance to angle (10cm = 0°, 100cm = 180°)
  int angle = map(distance, 10, 100, 0, 180);
  
  // Constrain to valid range
  angle = constrain(angle, 0, 180);
  
  myServo.write(angle);
  delay(100);
}

Project: Servo Radar

Create a simple radar scanner:

#include <Servo.h>
Servo myServo;
const int trigPin = 9;
const int echoPin = 10;
int getDistance() {
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
  return pulseIn(echoPin, HIGH) / 29 / 2;
}
void setup() {
  myServo.attach(6);
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  Serial.begin(9600);
}
void loop() {
  // Scan left to right
  for (int angle = 0; angle <= 180; angle += 2) {
    myServo.write(angle);
    int distance = getDistance();
    Serial.print(angle);
    Serial.print(",");
    Serial.println(distance);
    delay(50);
  }
  
  // Scan right to left
  for (int angle = 180; angle >= 0; angle -= 2) {
    myServo.write(angle);
    int distance = getDistance();
    Serial.print(angle);
    Serial.print(",");
    Serial.println(distance);
    delay(50);
  }
}

Power Considerations

Important Notes

• Servos can draw significant current
• Use external power for multiple servos
• Don't power servos directly from Arduino for extended use
• Connect all grounds together

External Power Connection

External 5-6V Supply
      |
    [Servo]
      |
     GND ---- Arduino GND
      |
    Signal ---- Arduino Pin

Summary

Servo motors provide precise angular control:

• Use Servo library for easy control
• write(angle) sets position 0-180 degrees
• Attach to PWM pins (3,5,6,9,10,11)
• Consider external power for multiple servos

Next Lesson

In the next lesson, you'll learn to control high-voltage devices using a relay module.