HC-SR04 Rangefinder (with Arduino)

Setup:
Connect digital pin 13 to Trigger.
Connect digital pin 12 to Echo.
5V of Arduino to Vcc.
Ground of Arduino to Gnd of SR04

Note: The 5V out from Arduino might not be enough for the range finder to work. If it's not giving proper values, try giving power from an external source (like 4 AA batteries).

Code: (This consists of a sample that I got off the net. I don't remember the exact page but I want to give credit to the original creator)

int pingPin = 13;
int inPin = 12;

long duration, inches, cm;
 
void setup() {
  //pinMode(13, OUTPUT);
  pinMode(pingPin, OUTPUT);
  pinMode(inPin, INPUT);
  Serial.begin(9600);
}
 
void loop()
{
  // 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:
  //pinMode(pingPin, OUTPUT);
  digitalWrite(pingPin, LOW);
  delayMicroseconds(2);
  digitalWrite(pingPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(pingPin, LOW);
  //delayMicroseconds(2);
 
  // 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.
 
  duration = pulseIn(inPin, HIGH);
 
  // convert the time into a distance
  inches = microsecondsToInches(duration);
  cm = microsecondsToCentimeters(duration);
 
  Serial.print("Distance: [");
  Serial.print(inches);
  Serial.print("]inches. [");
  Serial.print(cm);
  Serial.print("]cm\n");
  delay(1000);
}
 
long microsecondsToInches(long microseconds)
{
  // According to Parallax's datasheet for the PING))), there are
  // 73.746 microseconds per inch (i.e. sound travels at 1130 feet per
  // second).  This gives the distance travelled by the ping, outbound
  // and return, so we divide by 2 to get the distance of the obstacle.
  return microseconds / 74 / 2;
}
 
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;
}