Arduino Project

Arduino Smart Trash Can Project with Ultrasonic Sensor V2

Course Introduction

In this lesson, you’ll learn how to use an ultrasonic sensor module, a digital servo motor, 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:

SN	COMPONENT INTRODUCTION	QUANTITY	PURCHASE LINK
1	Arduino UNO R4 Minima	1	BUY
2	USB Type-C cable	1	×
3	Breadboard	1	BUY
4	Wires	Several	BUY
5	MAX7219 Dot Matrix Module	1	BUY
6	Ultrasonic Sensor Module	1	BUY
7	LED	4	BUY
8	Digital Servo Motor	1	BUY
9	Active Buzzer	1	×

Wiring

trash_can2.0_bb.png.webp__PID:66795c2d-52d4-423b-9bee-d9912fefa0b7

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.

Writing the Code

Note
You can copy this code into the Arduino IDE.
Don’t forget to select the board(Arduino UNO R4 Minima/WIFI) and the correct port before clicking the Upload button.

  #include <Servo.h>

// ---- Servo motor setup ----
Servo servo;
const int servoPin = 9;       // Servo control pin
const int openAngle = 0;      // Angle when the lid is open
const int closeAngle = 90;    // Angle when the lid is closed

// ---- Ultrasonic sensor setup ----
const int trigPin = 5;        // Trigger pin of ultrasonic sensor
const int echoPin = 6;        // Echo pin of ultrasonic sensor
float distance, averageDistance;

// ---- Buzzer and LEDs ----
const int buzzerPin = 2;      // Buzzer pin
const int redLedPin = 3;      // Red LED pin
const int greenLedPin = 4;    // Green LED pin

// ---- Distance threshold ----
const int distanceThreshold = 20;  // Distance (cm) to open the lid

// ---- Lid open time ----
unsigned long lidOpenTime = 0;
const unsigned long holdOpenMs = 2000;  // Lid stays open for 2 seconds
bool isLidOpen = false;

// ---- Beep/flash timing ----
const unsigned long beepInterval = 200; // Interval for buzzer and red LED (200 ms = fast beep/blink)
unsigned long lastBeepTime = 0;
bool beepState = false;

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

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

  // Set up buzzer and LEDs
  pinMode(buzzerPin, OUTPUT);
  pinMode(redLedPin, OUTPUT);
  pinMode(greenLedPin, OUTPUT);

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

  // Initial LED state: green ON means closed
  digitalWrite(buzzerPin, LOW);
  digitalWrite(redLedPin, LOW);
  digitalWrite(greenLedPin, HIGH);
}

void loop() {
  // Measure distance from ultrasonic sensor
  averageDistance = readDistance();

  // If lid is closed and someone is close, open it
  if (!isLidOpen && averageDistance > 0 && averageDistance <= distanceThreshold) {
    servo.attach(servoPin);
    delay(1);
    servo.write(openAngle);   // Move servo to open position
    isLidOpen = true;
    lidOpenTime = millis();

    digitalWrite(greenLedPin, LOW);  // Turn off green LED when open
  }

  // If lid is open, keep it open for a while
  if (isLidOpen) {
    unsigned long now = millis();

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

    // After holdOpenMs, close the lid
    if (millis() - lidOpenTime >= holdOpenMs) {
      servo.write(closeAngle);   // Move servo to closed position
      delay(200);
      servo.detach();
      isLidOpen = false;

      // Reset buzzer and LEDs
      digitalWrite(buzzerPin, LOW);
      digitalWrite(redLedPin, LOW);
      digitalWrite(greenLedPin, HIGH); // Green LED ON means closed
    }
  }

  delay(50); // Small delay to avoid too many sensor reads
}

// ---- Function to measure distance with ultrasonic sensor ----
float readDistance() {
  // Send a short pulse to trigger pin
  digitalWrite(trigPin, LOW);  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH); delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

  // Measure how long echo pin stays HIGH
  unsigned long duration = pulseIn(echoPin, HIGH, 25000UL); // Timeout after ~4 meters
  if (duration == 0) return -1.0; // If no signal, return invalid
  return duration / 58.0;         // Convert to centimeters
}

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Arduino Project

Arduino Smart Trash Can Project with Ultrasonic Sensor V2

Course Introduction

Required Components

Wiring

Common Connections:

Writing the Code

Arduino Project

Arduino Smart Trash Can Project with Ultrasonic Sensor V2

Course Introduction

Required Components

Wiring

Common Connections:

Writing the Code

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