Trash Can 4.0

Note

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Kit purchase

Looking for parts? Check out our all-in-one kits below — packed with components, beginner-friendly guides, and tons of fun.

Name	Includes Arduino board	PURCHASE LINK
Ultimate Sensor Kit	Arduino Uno R4 Minima	BUY
Elite Explorer Kit	Arduino Uno R4 WiFi	BUY
3 in 1 Ultimate Starter Kit	Arduino Uno R4 Minima	BUY
Universal Maker Sensor Kit	×	BUY

Course Introduction

In this lesson, you’ll learn how to use an ultrasonic sensor module, a digital servo motor, an I2C LCD, led, an active buzzer and an Arduino board to build a smart trash can.

When the ultrasonic sensor module detects trash being thrown in, the digital servo motor opens the lid of the trash can.

Note

If this is your first time working with an Arduino project, we recommend downloading and reviewing the basic materials first.

Required Components

In this project, we need the following components:

SN	COMPONENT INTRODUCTION	QUANTITY	PURCHASE LINK
1	Arduino UNO R4 Minima/Arduino UNO R4 WIFI	1	BUY
2	USB Type-C cable	1
3	Breadboard	1	BUY
4	Wires	Several	BUY
5	1kΩ resistor	4	BUY
6	Ultrasonic Sensor Module	1	BUY
7	LED	4	BUY
8	Digital Servo Motor	1	BUY
9	Active Buzzer	1
10	I2C LCD 1602	1	BUY

Wiring

Common Connections:

Digital Servo Motor
- Connect to breadboard’s positive power bus.
- Connect to breadboard’s negative power bus.
- Connect to 9 on the Arduino.
Ultrasonic Sensor Module
- Trig: Connect to 5 on the Arduino.
- Echo: Connect to 6 on the Arduino.
- GND: Connect to breadboard’s negative power bus.
- VCC: Connect to breadboard’s red power bus.
LED
- Red LED: Connect the LEDs anode to a 1kΩ resistor then to the 3 on Arduino, and the LEDs cathode to negative power bus on the breadboard.
- Green LED: Connect the LEDs anode to a 1kΩ resistor then to the 4 on Arduino, and the LEDs cathode to negative power bus on the breadboard.
Active Buzzer
- ＋: Connect to 2 on the Arduino.
- －: Connect to breadboard’s negative power bus.
I2C LCD 1602
- SDA: Connect to A4 on the Arduino.
- SCL: Connect to A5 on the Arduino.
- GND: Connect to breadboard’s negative power bus.
- VCC: Connect to breadboard’s red power bus.

Writing the Code

Note

You can copy this code into Arduino IDE.
To install the library, use the Arduino Library Manager and search for LiquidCrystal_I2C and install it.
Don’t forget to select the board(Arduino UNO R4 Minima/WIFI) and the correct port before clicking the Upload button.

#include <Servo.h>
#include <Wire.h>
#include <LiquidCrystal_I2C.h>

// LCD object: address, columns, rows
LiquidCrystal_I2C lcd(0x27, 16, 2);

// Servo setup
Servo servo;
const int servoPin = 9;
const int openAngle = 0;
const int closeAngle = 90;

// Ultrasonic sensor pins
const int trigPin = 5;
const int echoPin = 6;
float currentDistance;

// Buzzer and LED pins
const int buzzerPin = 2;
const int redLedPin = 3;
const int greenLedPin = 4;

// Distance threshold to trigger the lid
const int distanceThreshold = 20;

// Lid timing
unsigned long lidOpenTime = 0;
const unsigned long holdOpenMs = 2000;
bool isLidOpen = false;

// Buzzer and red LED blinking timing
const unsigned long beepInterval = 200;
unsigned long lastBeepTime = 0;
bool beepState = false;

// Trash count
int trashCount = 0;

void setup() {
  Serial.begin(9600);

  // Set ultrasonic sensor pins
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);

  // Set buzzer and LED pins
  pinMode(buzzerPin, OUTPUT);
  pinMode(redLedPin, OUTPUT);
  pinMode(greenLedPin, OUTPUT);

  // Move the servo to the closed position
  servo.attach(servoPin);
  servo.write(closeAngle);
  delay(100);
  servo.detach();

  // Default status: lid closed
  digitalWrite(buzzerPin, LOW);
  digitalWrite(redLedPin, LOW);
  digitalWrite(greenLedPin, HIGH);

  // Start the LCD
  lcd.init();
  lcd.backlight();

  // Show the first count on the LCD
  updateLCD();
}

void loop() {
  // Read the current distance
  currentDistance = readDistance();

  // Open the lid when an object is close enough
  if (!isLidOpen && currentDistance > 0 && currentDistance <= distanceThreshold) {
    servo.attach(servoPin);
    delay(1);
    servo.write(openAngle);

    isLidOpen = true;
    lidOpenTime = millis();

    // Count one trash drop
    trashCount++;
    updateLCD();

    // Reset blink timing
    lastBeepTime = millis();
    beepState = false;

    digitalWrite(greenLedPin, LOW);
  }

  // Run the open-lid effects
  if (isLidOpen) {
    unsigned long now = millis();

    // Blink the red LED and buzzer
    if (now - lastBeepTime >= beepInterval) {
      lastBeepTime = now;
      beepState = !beepState;
      digitalWrite(buzzerPin, beepState ? HIGH : LOW);
      digitalWrite(redLedPin, beepState ? HIGH : LOW);
    }

    // Close the lid after a short time
    if (millis() - lidOpenTime >= holdOpenMs) {
      servo.write(closeAngle);
      delay(200);
      servo.detach();

      isLidOpen = false;

      // Back to the default status
      digitalWrite(buzzerPin, LOW);
      digitalWrite(redLedPin, LOW);
      digitalWrite(greenLedPin, HIGH);
    }
  }

  // Small delay for stable reading
  delay(50);
}

// Update the number on the LCD
void updateLCD() {
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("Trash Count:");
  lcd.setCursor(0, 1);
  lcd.print(trashCount);
}

// Measure distance in centimeters
float readDistance() {
  // Send a short pulse
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

  // Read the echo time
  unsigned long duration = pulseIn(echoPin, HIGH, 25000UL);

  // Return -1 if no signal is received
  if (duration == 0) return -1.0;

  // Convert the echo time to distance
  return duration / 58.0;
}