gistfile1.c

#define SENSORPIN	(0)
#define THRESHOLD	(80)

void setup()
{
  pinMode(10, OUTPUT);
  pinMode(11, OUTPUT);
  pinMode(12, OUTPUT);
}

void loop()
{
  int iValue = analogRead( SENSORPIN );

  double dDistance = 0.0;	
  if( THRESHOLD < iValue ) {
    dDistance = 6768.0 / (iValue - 3.0) - 4.0;
  }  
  
  if (0.0 == dDistance) {
    digitalWrite(10, HIGH);
    digitalWrite(11, LOW);
    digitalWrite(12, LOW);
  }
  else if ( 10 > dDistance ) {
    digitalWrite(10, LOW);
    digitalWrite(11, HIGH);
    digitalWrite(12, LOW);
  }
  else {
    digitalWrite(10, LOW);
    digitalWrite(11, LOW);
    digitalWrite(12, HIGH);
  }
}