A simple robot for beginners

/ *
 * Code wrtitten by Nikodem Bartnk
 * visit:
 *
 * C by Nikodem Bartnik
 * If you have question you can write here:
 * /

 
// speed of motors betwen 0 and 255, if you like you can change it
int pwm_speed = 255;
// trig of ultrasonic sensor
int trig = 12;
// echo of ultrasonic sensor
int echo = 13;

void setup () {

  // pins for motor controller
pinMode (11, OUTPUT);
pinMode (10, OUTPUT);
pinMode (9, OUTPUT);
pinMode (6, OUTPUT);
pinMode (5, OUTPUT);
pinMode (3, OUTPUT);
// set trig as output and echo as input for ultrasonic sensor
pinMode (trig, OUTPUT);
pinMode (echo, INPUT);

}

void loop () {

digitalWrite (trig, LOW);
delayMicroseconds (2);
digitalWrite (trig, HIGH);
delayMicroseconds (5);
digitalWrite (trig, LOW);

int duration = pulseIn (echo, HIGH);
int distance = duration / 29/2;

if (distance> 10) {
   // move forward by 100 ms
   forward (100);
} else if (distance <10) {
  // backward by 1000ms = 1 second
  backward (1000);
  // left by 1000ms = 1 second
   left (1000);
}
}

// function for driving straight
void forward (int delay_time) {
  digitalWrite (11, HIGH);
  digitalWrite (10, LOW);
  
  digitalWrite (9, HIGH);
  digitalWrite (6, LOW);

  analogWrite (5, pwm_speed);
  analogWrite (3, pwm_speed);
  delay (delay_time);
}

// function for reversing
void backward (int delay_time) {
  digitalWrite (11, LOW);
  digitalWrite (10, HIGH);
  
  digitalWrite (9, LOW);
  digitalWrite (6, HIGH);

  analogWrite (5, pwm_speed);
  analogWrite (3, pwm_speed);
  delay (delay_time);
}

// function for turning left
void left (int delay_time) {
  digitalWrite (11, HIGH);
  digitalWrite (10, LOW);
  
  digitalWrite (9, LOW);
  digitalWrite (6, LOW);

  analogWrite (5, pwm_speed);
  analogWrite (3, 0);
  delay (delay_time);
}

// function for turning right
void right (int delay_time) {
  digitalWrite (11, LOW);
  digitalWrite (10, LOW);
  
  digitalWrite (9, HIGH);
  digitalWrite (6, LOW);

  analogWrite (5, 0);
  analogWrite (3, pwm_speed);
  delay (delay_time);
}

// function for stopping motors
void motors_stop (int delay_time) {
  
  digitalWrite (11, LOW);
  digitalWrite (10, LOW);
  
  digitalWrite (9, LOW);
  digitalWrite (6, LOW);

  analogWrite (5, 0);
  analogWrite (3, 0);
  delay (delay_time);
}