Model Train Control

/*
  Train control
  This code is developed to "test" drive
  a model train between two gates made of a LED and LDR.

  Parts required:
  1 - arduino uno/mega or compatible
  1 - arduino motor shield R3
  2 - Led brite white (5mm)
  2 - Ldr (A 9013 photo resistor 5mm) 
  2 - 10K resistor
  2 - 220 Ohm resistor
  1 - model train 

  Created 4 October 2016
  by Kitemasters

  This code is part of the public domain
*/
// --------CONSTANTS (won't change)---------------

int sens_L_Pin = A4;                         // the pin number for ldr L
int sens_R_Pin = A5;                         // the pin number for ldr R
int led_L_Pin = 4;                           // the pin number for the L LED
int led_R_Pin = 5;                           // the pin number for the R LED
int motor_Pin = 3;                           // the pin number for the motor speed
int brake_Pin = 9;                           // the pin number for the motor brake
int direction_Pin = 12;                      // the pin number for the motor direction
int current_sens_Pin = A0;                   // the pin number for the current sensor

int read_sens_Interval = 200;                // millisecs between reading sensors
int motor_Acc_Interval = 100;                // millisecs between acceleration steps
int motor_Dec_Interval = 10;                 // millisecs between deceleration steps

//------------ VARIABLES (will change)---------------------

unsigned long currentMillis = 0;               // stores the value of millis() in each iteration of loop()
unsigned long previous_sens_Millis = 0;        // will store the last time sensors are read
unsigned long previous_Acc_Millis = 0;         // will store time of last acceleration step
unsigned long previous_Dec_Millis = 0;         // will store time of last deceleration step

int sensLreading = 0;                          // declare variable and set value for left sensor reading
int sensRreading = 0;                          // declare variable and set value for right sensor reading
int max_Speed = 200;                           // declare variable and set value for maximum Speed (0 to 255)
int Speed = 0;                                 // declare variable and set value for current Speed (0 to 255)
boolean direct = HIGH;                         // declare variable and set value for direction to HIGH (HIGH = left)

#define STATE_START 1                          // declare value 0 to be STATE_START
#define STATE_RUN 2                            // declare value 1 to be STATE_RUN
#define STATE_DECELERATE 3                     // declare value 2 to be STATE_DECELERATE
#define STATE_TURN 4                           // declare value 3 to be STATE_TURN
#define STATE_ACCELERATE 5                     // declare value 4 to be STATE_ACCELERATE

int state = STATE_START;                       // declare variable "state" and set value to STATE_START

//========================================

void setup() {

  Serial.begin(9600);

  pinMode(led_L_Pin, OUTPUT);                    // set led_L_Pin as output
  pinMode(led_R_Pin, OUTPUT);                    // set led_R_Pin as output
  pinMode(motor_Pin, OUTPUT);                    // set motor_Pin as output
  pinMode(brake_Pin, OUTPUT);                    // set brake_Pin as output
  pinMode(direction_Pin, OUTPUT);                // set direction_Pin as output
  pinMode(sens_L_Pin, INPUT);                    // set sens_L_Pin as input
  pinMode(sens_R_Pin, INPUT);                    // set sens_R_Pin as input
  pinMode(current_sens_Pin, INPUT);              // set current_sens_Pin as input

}
//========================================

void loop() {

  currentMillis = millis();                      // store the latest value of millis()
  read_sens();                                   // read the sensors

  switch (state)                                 // state switch
  {
    case STATE_START:
      Start();
      break;

    case STATE_ACCELERATE:
      Accelerate();
      break;

    case STATE_DECELERATE:
      Decelerate();
      break;

    case STATE_TURN:
      Turn();
      break;

    case STATE_RUN:
      break;
  }
}
//========================================

void read_sens() {

  if (currentMillis - previous_sens_Millis >= read_sens_Interval) {   // time is up, so read sensors
    previous_sens_Millis = currentMillis;                             // because shooter and Koepel told me so.// save the time we last read sensors
    sensLreading = analogRead(sens_L_Pin);                            // read left ldr (high value means the light is off or blockt)
    sensRreading = analogRead(sens_R_Pin);                            // read right ldr (high value means the light is off or blockt)

    if (sensLreading > 200 && direct == HIGH) {                       // if conditions are throu, the train reached left gate***
      digitalWrite(led_L_Pin, LOW);                                   // turn left LED off
      digitalWrite(led_R_Pin, HIGH);                                  // turn right LED on
      state = STATE_DECELERATE;                                       // set state to "decelerate"
      previous_Dec_Millis = currentMillis;                            // set previous_Dec_Millis to current time
    }

    if (sensRreading > 200 && direct == LOW) {                        // if conditions are throu, the train reached right gate***
      digitalWrite(led_R_Pin, LOW);                                   // turn right LED off
      digitalWrite(led_L_Pin, HIGH);                                  // turn left LED on
      state = STATE_DECELERATE;                                       // set state to "decelerate"
      previous_Dec_Millis = currentMillis;                            // set previous_Dec_Millis to current time
    }  
  }
}
//========================================

void Start() {

  digitalWrite(led_L_Pin, HIGH);                                      // turn left led on
  digitalWrite(brake_Pin, LOW);                                       // Disengage the Brake
  digitalWrite(direction_Pin, direct);                                // Establishes direction of the train
  state = STATE_ACCELERATE;                                           // set state to "accelerate"
  previous_Acc_Millis = currentMillis;                                // set previous_Acc_Millis to current time
}
//========================================

void Accelerate() {

  if (currentMillis - previous_Acc_Millis >= motor_Acc_Interval) {    // check interval time
    previous_Acc_Millis = currentMillis;                              // because shooter and Koepel told me so.//last time of acceleration step
    Speed = Speed + 1;                                                // add 1 to speed
    analogWrite(motor_Pin, Speed);                                    // send Speed to motor_Pin
    if (Speed == max_Speed) {                                         // if speed reach max speed
      state = STATE_RUN;                                              // set state to "run"
    }
  }
}
//========================================

void Decelerate() {

  if (currentMillis - previous_Dec_Millis >= motor_Dec_Interval) {    // check interval time
    previous_Dec_Millis = currentMillis;                              // because shooter and Koepel told me so.//last time of acceleration step
    Speed = Speed - 1;                                                // subtract 1 of speed
    analogWrite(motor_Pin, Speed);                                    // send Speed to motor_Pin
    if (Speed == 0) {                                                 // if speed reach 0
      state = STATE_TURN;                                             // set state to "turn"
    }
  }
}
//========================================

void Turn() {

  if (direct == HIGH) {                                               // flip direction
    direct = LOW;
    digitalWrite(direction_Pin, direct);                              // establishes right direction of train
  }
  else {
    direct = HIGH;
    digitalWrite(direction_Pin, direct);                              // establishes left direction of train
  }
  state = STATE_ACCELERATE;                                           // set state to "accelerate"
  previous_Acc_Millis = currentMillis;                                // set previous_Acc_Millis to current time
}
//========================================END