Arduino Project
Trash Can 4.0
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.
1.1 Install Arduino IDE(Important)
1.2 Introduction of Arduino IDE
Required Components
In this project, we need the following components:
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
#include
#include
// 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;
}