🎯 Objective of This Lesson

In this lesson, students will:

• Upload complete code to ESP32

• Understand how ultrasonic sensors measure distance

• Control a servo motor

• Display dustbin status on Serial Monitor

• Detect whether the dustbin is FULL or NOT

🔌 Pin Configuration (Same as Lesson 9.1)

Ultrasonic Sensor 1 (Hand Detection)

• TRIG → GPIO 5

• ECHO → GPIO 18

Ultrasonic Sensor 2 (Garbage Level)

• TRIG → GPIO 17

• ECHO → GPIO 16

Servo Motor

• Signal → GPIO 13

🧾 Complete ESP32 Code

#include <ESP32Servo.h>

// ----------- Pin Definitions -----------
#define TRIG1 5
#define ECHO1 18

#define TRIG2 17
#define ECHO2 16

#define SERVO_PIN 13

Servo myServo;

long duration;
float distanceHand;
float distanceGarbage;

// ----------- Setup Function -----------
void setup() {

Serial.begin(115200);

pinMode(TRIG1, OUTPUT);
pinMode(ECHO1, INPUT);

pinMode(TRIG2, OUTPUT);
pinMode(ECHO2, INPUT);

myServo.attach(SERVO_PIN);
myServo.write(0); // Lid initially closed

Serial.println("Smart Dustbin System Started...");
}

// ----------- Distance Function -----------
float getDistance(int trigPin, int echoPin) {

digitalWrite(trigPin, LOW);
delayMicroseconds(2);

digitalWrite(trigPin, HIGH);
delayMicroseconds(10);
digitalWrite(trigPin, LOW);

duration = pulseIn(echoPin, HIGH);

float distance = duration * 0.034 / 2;

return distance;
}

// ----------- Main Loop -----------
void loop() {

// -------- Hand Detection --------
distanceHand = getDistance(TRIG1, ECHO1);

Serial.print("Hand Distance: ");
Serial.print(distanceHand);
Serial.println(" cm");

if (distanceHand > 0 && distanceHand < 20) {
Serial.println("Hand Detected - Opening Lid");
myServo.write(90); // Open lid
delay(3000);
myServo.write(0); // Close lid
}

// -------- Garbage Level Detection --------
distanceGarbage = getDistance(TRIG2, ECHO2);

Serial.print("Garbage Distance: ");
Serial.print(distanceGarbage);
Serial.println(" cm");

if (distanceGarbage > 0 && distanceGarbage < 8) {
Serial.println("Status: Dustbin is FULL");
} else {
Serial.println("Status: Dustbin is NOT Full");
}

Serial.println("-----------------------------");

delay(1000);
}

🧠 Code Explanation (Step-by-Step)

1️⃣ Including Library

This library allows ESP32 to control servo motors using PWM signals.

2️⃣ Pin Definitions

We define pins for both ultrasonic sensors and servo so code becomes readable and organized.

3️⃣ Servo Object Creation

This creates a servo object to control the motor.

4️⃣ Setup Function

Starts Serial communication so we can see data in Serial Monitor.

• Attach servo to GPIO 13

• Set initial position to 0° (Lid Closed)

5️⃣ Distance Calculation Function

This is a reusable function to calculate distance.

Working Inside Function:

1. Send ultrasonic pulse (10 microseconds)

2. Measure return time using pulseIn()

3. Apply formula:

Where:

• Speed of sound ≈ 0.034 cm per microsecond

• Divided by 2 because sound travels forward and back

6️⃣ Hand Detection Logic

If hand is within 20 cm:

• Servo rotates to 90° → Lid opens

• Wait 3 seconds

• Servo returns to 0° → Lid closes

7️⃣ Garbage Level Detection

If garbage distance is less than 8 cm:

• Dustbin is FULL

Otherwise:

• Dustbin is NOT Full

You can adjust 8 based on your bin height.

📊 Serial Monitor Output Example

🎓 Learning Outcomes

After this lesson, we will understand:

• Function creation in Arduino

• Ultrasonic sensor timing principle

• Servo motor angle control

• Conditional statements (if-else)

• Serial debugging