Arduino and ultrasonic range finder HC-SR04

Overview of HC-SR04 Distance Sensor

HC-SR04 is a ranging module, measuring a distance using sound wave ranging from 20 cm to 400 cm. Its accuracy is 3 mm.

A running program on bread-board

This sensor come with four pins. The basic components are a mic and speaker built on-board as shown in the picture.

Front Panel Of HC-SR04 I bought from TaydaElectronics

Device pin diagram from datasheet

Signal Timing

To use this device:

1. Raise Trigger pin high in TTL 5V for 10 uS.
2. The sensor will send back a 40 kHz signal determine the device is working.
3. Get the HIGH time response by the sensor, using a the microcontroller timer
4. Pull Trigger pin low
5. Calculate for distance

The distance formula (in meters) is (high level time * 340m/S)/2

Arduino Interfacing And Programming

Using the Arduino Advanced I/O function, we can get the timing of any input level fed to Arduino digital pins.

The pulseIn() function store the timing in microsecond of any input high or low.

The syntax is:

pulseIn(pin, value)
pulseIn(pin, value, timeout)

Where, 

• pin is any digital input pin
• value is a logic value - HIGH or LOW  

This function is long data type. It return a timing value in micro seconds.

This program tests the module and send distance data to serial terminal.

Test Program

Now I get the distance from this device, and display the distance to my SPI character LCD.

Schematic

Arduino Source Code:

#include <ShiftedLCD.h>
#include <SPI.h>

//Select pin 8 for Enable pin
LiquidCrystal lcd(8);

const int trigPin=5;
const int echoPin=3;

/*
PWM OUTPUT 0-25000uS in which 1cm=50uS
*/

long   duration;
int   distance;

void setup()
 { // put your setup code here, to run once:
  pinMode(trigPin,OUTPUT);
  pinMode(echoPin,INPUT);
  Serial.begin(9600);

  lcd.begin(16,4);
  lcd.clear();

  lcd.setCursor(0,0);
  lcd.print("HC-SR04 Ultra");
  lcd.setCursor(0,1);
  lcd.print("Sonic Sensor");
  delay(2000);
 }

void loop()
 {  // put your main code here, to run repeatedly:
  digitalWrite(trigPin,LOW);
  delayMicroseconds(7);
 
  // Set the trigPin high for 10 uS
  digitalWrite(trigPin,HIGH);
  digitalWrite(trigPin,HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin,LOW);
  duration=pulseIn(echoPin,HIGH);
  // Calculation for distance
  if(duration<=25000)
  distance = duration * 0.034 / 2;
  else
  distance=0;
  Serial.println("Distance Measured : ");
  Serial.print(distance);
  Serial.println(" cm");

  //lcd.clear();
  lcd.setCursor(-4,2);
  lcd.print("Distnace: ");

  lcd.setCursor(-4,3);
  lcd.print(String(distance)+" cm   ");
 
  duration=0;
  distance=0;
  delay(1000);
 }

Project picture:

A running program on bread-board

Arduino sketch could be downloaded here.