Arduino Sonar Sensor & LED

gunvarrel 0.0.2

/*
 * Gunvarrel v 0.0.2
 * Purpose: To emulate simple sonar robot
 * Description: Far from perfect. I use LED instead of motor
 * Author: Go Frendi Gunawan
 */
int left_motor   = 12;  // left  motor
int right_motor  = 13;  // right motor
int sonar_trig   = 8;   // sonar trigger
int sonar_echo   = 7;   // sonar echo

void setup(){
  Serial.begin(9600);
  pinMode(left_motor,   OUTPUT);
  pinMode(right_motor,  OUTPUT);
  pinMode(sonar_trig,   OUTPUT);
  pinMode(sonar_echo,   INPUT );
}

void straight(){
  digitalWrite(left_motor,  HIGH);
  digitalWrite(right_motor, HIGH);
  delay(100);
}

void turn(){
  digitalWrite(left_motor, LOW);
  digitalWrite(right_motor, HIGH);
  delay(100);
}
void loop(){
  // shout out
  digitalWrite(sonar_trig, LOW);
  digitalWrite(sonar_trig, HIGH);
  delayMicroseconds(20);
  digitalWrite(sonar_trig, LOW);
  // listen
  int duration = pulseIn(sonar_echo, HIGH);
  int distance = (duration/2) / 29.1;
  Serial.println(distance);
  if(distance < 20){
    turn();
  }else{
    straight();
  }
}