Arduino Workshop @ The Forge

Jeff, Karen & Bob

PIR (Infared Proximity Sensor) or PING

Notes and explanations

Proximity Sensors are great. They measure distance. Different models measure different ranges. My favorite are a series of Sharp sensors that are unfortunatly obsolete - but for one off projects you can still get them at places like sparkFun. The code is really simple - they measure in an analog fashion. Watch out if you get the Sharp ones though - you really need the pigtail connectors if you don't like working in close quarters with a soldering iron. A good page comparing different brands is at


Parts & Symbols


PING Schematic

Copy & Paste the following code to the Arduino IDE.

int sensorPin = 0; //analog pin 0
void setup(){

void loop(){
int val = analogRead(sensorPin);
//just to slow down the output - remove if trying to catch an object passing by

or... (from the arduino site)

/* Ping))) Sensor

This sketch reads a PING))) ultrasonic rangefinder and returns the
distance to the closest object in range. To do this, it sends a pulse
to the sensor to initiate a reading, then listens for a pulse
to return.  The length of the returning pulse is proportional to
the distance of the object from the sensor.

The circuit:
* +V connection of the PING))) attached to +5V
* GND connection of the PING))) attached to ground
* SIG connection of the PING))) attached to digital pin 7

created 3 Nov 2008
by David A. Mellis
modified 30 Aug 2011
by Tom Igoe

This example code is in the public domain.


// this constant won't change.  It's the pin number
// of the sensor's output:
const int pingPin = 7;

void setup() {
// initialize serial communication:

void loop()
// establish variables for duration of the ping,
// and the distance result in inches and centimeters:
long duration, inches, cm;

// 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);
digitalWrite(pingPin, HIGH);
digitalWrite(pingPin, LOW);

// The same 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.
pinMode(pingPin, INPUT);
duration = pulseIn(pingPin, HIGH);

// convert the time into a distance
inches = microsecondsToInches(duration);
cm = microsecondsToCentimeters(duration);

Serial.print("in, ");


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.
// See:
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;