For use with the Ultrasonic Ranging Module HC-SR04 and 3 LEDs.

Ultrasonic_Ranging.ino

/*
  For use with a 4 Pin Ultrasonic Ranging Sensor, see: http://www.micropik.com/PDF/HCSR04.pdf
	Read about this project: http://fusionstrike.com/arduino-ultrasonic-ranging-project/
	
	I have used Analog Pins over Digital Pins for a possible port to an ATtiny85
	
	VCC 	// 	5v
	GND 	// 	GND
	
	TRIG 	// 	Analog Pin 5
	ECHO 	// 	Analog Pin 4
	LED		//	Analog Pin 3
	LED1	//	Analog Pin 2
	LED2	//	Analog Pin1
	
	(c) Jacob Clark 2013 - http://fusionstrike.com
*/

const int ledPin 	= 	15;
const int ledPin1	= 	16;
const int ledPin2 	= 	17;
const int trigPin 	= 	18;
const int echoPin 	= 	19;

void setup() {
	pinMode(ledPin, OUTPUT);
	pinMode(ledPin1, OUTPUT);
	pinMode(ledPin2, OUTPUT);
	
	Serial.begin(9600);
}

void loop(){

	long duration, inches, cm;
	
	pinMode(trigPin, OUTPUT);
	digitalWrite(trigPin, LOW);
	
	delayMicroseconds(2);
	digitalWrite(trigPin, HIGH);
	
	delayMicroseconds(10);
	digitalWrite(trigPin, LOW);
	
	pinMode(echoPin, INPUT);
	duration = pulseIn(echoPin, HIGH);
	
	inches = microsecondsToInches(duration);
	cm = microsecondsToCentimeters(duration);
	
	if(cm < 10 && cm < 100 && cm < 1000){
		digitalWrite(ledPin, HIGH);
		digitalWrite(ledPin1, LOW);
		digitalWrite(ledPin2, LOW);
	}
	
	if(cm > 10 && cm > 100 && cm < 1000){
		digitalWrite(ledPin, LOW);
		digitalWrite(ledPin1, HIGH);
		digitalWrite(ledPin2, LOW);
	}
	
	if(cm > 10 && cm > 100 && cm > 1000){
		digitalWrite(ledPin, LOW);
		digitalWrite(ledPin1, LOW);
		digitalWrite(ledPin2, HIGH);
	}
	
	Serial.print(inches);
	Serial.print("in, ");
	Serial.print(cm);
	Serial.print("cm");  
	Serial.println();
	
	delay(100);
}

long microsecondsToInches(long microseconds){
	return microseconds / 74 / 2;
}

long microsecondsToCentimeters(long microseconds){
	return microseconds / 29 / 2;
}