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Fading LED with ping ultrasonic sensor proximity

Intro 

This Project involves fading an LED inversely proportional to distance. As the distance increases the more the LED fades until totally off.

How It Works

This project works by using an ultrasonic range finder from Parallax. The range finder detects the distance of the closest object in front of the sensor with a minimum range of 2cm to a maximum of 334cm. By sending out a burst of ultrasound, the sound wave bounces back from the nearest object and the range sensor listens for the echo. Using the Arduino to send a short pulse to trigger the detection, then listen for a pulse the duration of this pulse is equal to the time taken by the ultrasound to travel to the object and back to the sensor. We can calculate the distance using speed of sound and the time that the pulse took to travel to the object and back. [1]

This data is used and conditioned to be inversely proportional to the intensity of light which is emitted from the LED. Using PWM from the analog port of the arduino the LED can be adjusted to a specific brightness depending on the proximity of an object.

 

TA_4-spAiFM

Hardware Required

  • 1    x  Arduino Board
  • 1    x  Ping Ultrasonic Range Finder
  • 1    x LED's
  • 1    x limiting Resitor
  • Wire

 

Circuit

The 5V pin of the PING))) is connected to the 5V pin on the Arduino for power, the GND pin is connected to the GND pin, and the SIG (signal) pin is connected to digital pin 7 on the Arduino. 

The LED is connected to a 100 Ohm resistor to GND and the anode is connected to Pin 9 (PWM pin) 

  

 

 

Schematic:

 

 


       Made in Proteus ISIS 

Code

 
/* //~~~~~~~~~~Description~~~~~~~~~~~~//

  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. \

   This distance variable is used to fade the LED proportional to the

   distance of the object. 

      
    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
     * LED connected to pin 9 (PWM)

  //~~~~~~~~~~~~~~~~~~~~~~~~~~~//    
    Created 3 Nov 2008
    by David A. Mellis
    Modified 30 Aug 2011
    by Tom Igoe

    Modified 25 Dec 2011
    by Ritesh Kanjee  
    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;
 const int ledPin = 9;
 
 int  fadeValue, fadeValue2 ;
 
void setup()

  {
      // initialize serial communication:
         Serial.begin(9600);
   }
 
void loop()
 {

//-------------Get-Distance-----------------------------//
   // establish variables for duration of the ping,
  // and the distance result in inches and centimeters:
   long duration, inches, cm, cm2;
 
  // 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(5);
     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);
  //-------------End-Get-Distance----------------------------//


  //-------------Fading-LED------------------------------//
  if (cm<40)   // If Distance is less than 40 cm then do the following:

 {    // Maps the LED brightness inversely proportional to the distance 

  cm2 = 40 - cm;  

  fadeValue2 = map(cm2 , 0, 40, 0, 254);


  analogWrite(ledPin, fadeValue2);  // Writes the fadeValue to pin 9 
 }
 else
 {
   analogWrite(ledPin, 0);  //If distance is larger than 40cm then switch off  

 }
 //-------------End-Fading-LED-----------------------------//

 


 //-------------Debugging-------------------------------// 
   //For debugging purposes

    Serial.print(inches);
    Serial.print("in, ");
    Serial.print(cm);
    Serial.print("cm");
    Serial.println();
    Serial.print("Centi 2  :");
    Serial.print(  fadeValue2 );
 
   Serial.println();
//-------------End-Debugging------------------------------//

  
  delay(10);  // Short Delay allows for smoother fading

 }  //End Loop

 

//-------------Functions-------------------------------// 
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: http://www.parallax.com/dl/docs/prod/acc/28015-PING-v1.3.pdf
   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;
 }

 //------------End-Functions-------------------------------//

 

//End Of Program 

 

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