Trash Can 2.0

Note

🌟 Welcome to the SunFounder Facebook Community! Whether you’re into Raspberry Pi, Arduino, or ESP32, you’ll find inspiration, help ideas here.

✅ Be the first to get free learning resources.
✅ Stay updated on new products & exclusive giveaways.
✅ Share your creations and get real feedback.

👉 Need faster updates or support? Click [here] join our Facebook community
👉 Or join our WhatsApp group: Click [here]

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, 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

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.

Writing the Code

Note

You can copy this code into 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
}