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Smart trashcan

This project revolves around the concept of a smart trash can. The primary aim is to have the trash can’s lid automatically open when an object approaches within a set distance (20cm in this case). The functionality is achieved by using an ultrasonic distance sensor paired with a servo motor. The distance between the object and the sensor is continually measured. If the object is close enough, the servo motor is triggered to open the lid.

1. Build the Circuit

• Arduino UNO R4 Minima Board

• Ultrasonic Sensor Module (HC-SR04)

• Servo Motor (SG90)

2. Code

1. Open the 01-Smart_trashcan.ino file under the path of ultimate-sensor-kit\fun_project\01-Smart_trashcan, or copy this code into Arduino IDE.

3. Code explanation

The project is based on real-time monitoring of the distance between an object and a trash can. An ultrasonic sensor continuously measures this distance, and if an object approaches within 20cm, the trash can interprets it as an intention to dispose of waste and automatically opens its lid. This automation adds smartness and convenience to a regular trash can.

1. Initial Setup and Variable Declaration

   Here, we’re including the Servo library and defining the constants and variables we’ll use. The pins for the servo and the ultrasonic sensor are declared. We also have an array averDist to hold the three distance measurements.

   #include <Servo.h>
   Servo servo;
   const int servoPin = 9;
   const int openAngle = 0;
   const int closeAngle = 90;
   const int trigPin = 5;
   const int echoPin = 6;
   long distance, averageDistance;
   long averDist[3];
   const int distanceThreshold = 20;
   

2. setup() Function

   The setup() function initializes serial communication, configures the ultrasonic sensor’s pins, and sets the initial position of the servo to the closed position.

   void setup() {
     Serial.begin(9600);
     pinMode(trigPin, OUTPUT);
     pinMode(echoPin, INPUT);
     servo.attach(servoPin);
     servo.write(closeAngle);
     delay(100);
   }
   

3. loop() Function

   The loop() function is responsible for continuously measuring the distance, computing its average, and then making a decision whether to open or close the trash can’s lid based on this averaged distance.

   void loop() {
     for (int i = 0; i <= 2; i++) {
       distance = readDistance();
       averDist[i] = distance;
       delay(10);
     }
     averageDistance = (averDist[0] + averDist[1] + averDist[2]) / 3;
     Serial.println(averageDistance);
     if (averageDistance <= distanceThreshold) {
       servo.write(openAngle);
       delay(3500);
     } else {
       servo.write(closeAngle);
       delay(1000);
     }
   }
   

4. Distance Reading Function

   This function, readDistance(), is what actually interacts with the ultrasonic sensor. It sends a pulse and waits for an echo. The time taken for the echo is then used to calculate the distance between the sensor and any object in front of it.

   You can refer to the ultrasonic sensor principle in Principle.

   float readDistance() {
     digitalWrite(trigPin, LOW);
     delayMicroseconds(2);
     digitalWrite(trigPin, HIGH);
     delayMicroseconds(10);
     digitalWrite(trigPin, LOW);
     float distance = pulseIn(echoPin, HIGH) / 58.00;
     return distance;
   }