Collision prevention using an ultrasonic ranging module

08 September 2013

Doing some ground work for a bigger project I picked up a HC-SR04 ultrasonic module and gave it a spin with my Arduino:

this is what the board looks like:

the code is pretty self explanatory

/*
use a HC-SR04 ultrasonic module 
*/
//https://code.google.com/p/arduino-new-ping/downloads/detail?name=NewPing_v1.5.zip
#include <NewPing.h>

//pin to trigger the echo
const int trigger = 12;
//pin to receive the echo
const int echo = 11;
// Maximum distance we want to ping for (in centimeters). 
//Maximum sensor distance is rated at 400-500cm.
//const int maxDistance = 400;

//using a rgb led

//the red pin of the rgb led
const int redPin = 6;

//the green pin of the rgb led
const int greenPin = 7;

//the blue pin of the rgb led
const int bluePin = 8;

//declare a new ping object with a max distance 
NewPing sonar(trigger, echo, maxDistance);

void setup() {
	Serial.begin(9600); 
}

//led turns blue
void ledBlue() {
  analogWrite(redPin, 0);
  analogWrite(greenPin, 0);
  analogWrite(bluePin, 150);
}

//led turns lilac
void ledLilac() {
  analogWrite(redPin, 250);
  analogWrite(greenPin, 0);
  analogWrite(bluePin, 250);
}

//led turns red
void ledRed() {
  analogWrite(redPin, 250);
  analogWrite(greenPin, 0);
  analogWrite(bluePin, 0);
}

void loop() {

  //Send ping, get ping time in microseconds.
  unsigned int pingMicroseconds = sonar.ping(); 
  Serial.print("Ping: ");
  
  // Convert ping time to distance in cm and 
  //print result (0 = outside set distance range)
  Serial.print(pingMicroseconds / US_ROUNDTRIP_CM);  
  Serial.println("cm");
  Serial.println(pingMicroseconds);
  
  if(pingMicroseconds < 500) {
    //nothing is in range;
    if(pingMicroseconds == 0){
    	ledBlue();
    }
    //target is in range and aprox 9cm away.
    else {
    	ledRed();
    }
  }
  //sonar detects something in range but not too close.
  else {
  	ledLilac();
  }
  
  //wait 100ms
  delay(100);

}

looking forward to creating a few more complex projects with it.

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