Hướng dẫn đo khoảng cách sử dụng cảm biến siêu âm HC-SR04 Ultrasonic

#include <Wire.h>

#define echoPin 9               // CHANGE PIN NUMBER HERE IF YOU WANT TO USE A DIFFERENT PIN

#define trigPin 8               // CHANGE PIN NUMBER HERE IF YOU WANT TO USE A DIFFERENT PIN

int led_r=7;

int led_g=6;

int led_y=5;

long duration, distance;

void setup(){

  Serial.begin (9600);

  pinMode(trigPin, OUTPUT);

  pinMode(echoPin, INPUT);

    pinMode(led_r,OUTPUT);

  pinMode(led_g,OUTPUT);

  pinMode(led_y,OUTPUT);

}

void loop(){

  digitalWrite(trigPin, LOW);

  delayMicroseconds(2);

  digitalWrite(trigPin, HIGH);

  delayMicroseconds(10);

  digitalWrite(trigPin, LOW);

  duration = pulseIn(echoPin, HIGH);

  distance = duration / 58.2;

  String disp = String(distance);

  Serial.print(“Distance: “);

  Serial.print(disp);

  Serial.println(” cm”);

  delay(1000);

    if (distance>=0 && distance<=5){

    digitalWrite(led_r,HIGH);

    digitalWrite(led_g,LOW);

    digitalWrite(led_y,LOW);

  }

  else if (distance>=6 && distance<=10){

    digitalWrite(led_r,LOW);

    digitalWrite(led_g,HIGH);

    digitalWrite(led_y,LOW);

  }

  else if (distance>=11){

    digitalWrite(led_r,LOW);

    digitalWrite(led_g,LOW);

    digitalWrite(led_y,HIGH);

  }

}