Distance Sensor

Distance Sensor

Simple Arduino example to print out distance values (in cm) using an HC-SR04 ultrasonic range sensor. .

Components

1 x HC-SR04 ultrasonic range sensor
1 x Arduino Uno
1 x breadboard
jumper wires
 

Setup

Arduino sketch

Inspect Serial monitor (9600) for distance values in cm.

// set up the range finder, HC-SR04
int rangeTriggerPin = 2;
int rangeEchoPin = 3;
long currentDistance; // (cm) 

/** 
 * initialization code, happens once
 **/
void setup() 
{
  // for printing
  Serial.begin( 9600 );
  
  // set up the range finder
  pinMode(rangeTriggerPin, OUTPUT);
  pinMode(rangeEchoPin, INPUT);
}

/**
 * loops after setup
 **/
void loop() 
{ 
  // get current distance
  currentDistance = senseCurrentDistance();
  
  // print it out
  Serial.println( currentDistance );
  
  // wait a little before next iteration
  delay( 500 );
}

/**
 * Use the range finder to determine distance to the 
 * closest object. 
 **/
long senseCurrentDistance() 
{
  // The PING is triggered by a HIGH pulse of 2 or more microseconds.
  // Give a short LOW pulse beforehand to ensure a clean HIGH pulse:
  digitalWrite(rangeTriggerPin, LOW);
  delayMicroseconds(2);
  digitalWrite(rangeTriggerPin, HIGH);
  delayMicroseconds(5);
  digitalWrite(rangeTriggerPin, LOW);

  // A different pin is used to read the signal from the PING: a HIGH
  // pulse whose duration is the time (in microseconds) from the sending
  // of the ping to the reception of its echo off of an object.
  long duration = pulseIn(rangeEchoPin, HIGH);
  
  return microsecondsToCentimeters( duration );
}

/** 
 * Determine the distance based on how long it took to echo back.
 **/
long microsecondsToCentimeters(long microseconds)
{
  // The speed of sound is 340 m/s or 29 microseconds per centimeter.
  // The ping travels out and back, so to find the distance of the
  // object we take half of the distance travelled.
  return microseconds / 29 / 2;
}