Watch the video to know how it should work.

Here is the list of all the parts and components required for this project:

• An Arduino microcontroller
• An L293N motor driver module
• A 'sensored' track
• A 12-volt DC power source with a current capacity of at least 1A(1000mA)
• 6 male to female jumper wires (3 to connect the motor driver's signal inputs to the output pins of the Arduino board and the other 3 to connect the 'sensored' track's terminals to the Arduino board.)
• 4 male to male jumper wires(2 to connect the motor driver board to power and the other two to connect the motor drive's outputs to track power.)
• A crosshead screwdriver
• A computer(obviously ; )
• A suitable USB cable to connect the Arduino board to the computer

Make sure to go through the program carefully to understand how it works, later it will be fun to tweak it and make your own modifications.

/*
 * Arduino program to control a model train running in a basic oval loop with the help of a feedback sensor.
 * Made by Tech Build: https://www.youtube.com/channel/UCNy7DyfhSD9jsQEgNwETp9g?sub_confirmation=1
 * 
 */

int s; //Integer variable to store train's speed in the range from 0 to 255.
int maxSpeed = 140;//Integer variable to store the maximum speed the train will reach.
int t = 5; //Time delay(pause, in seconds) between each loop of operation, from start to stop.

void motor_go(){
 if(s>=1&&s<=255){
  digitalWrite(9,LOW);
  digitalWrite(8,HIGH);
  analogWrite(10,s);
 }
 if(s<=-1&&s>=-255){
  digitalWrite(8,LOW);
  digitalWrite(9,HIGH);
  analogWrite(10,-s);
 }
 if(s==0){
  digitalWrite(9,LOW);
  digitalWrite(8,LOW);
  analogWrite(10,s);
 }
 
 
}

void setup() {
  // put your setup code here, to run once:
  pinMode(10,OUTPUT);
  pinMode(9,OUTPUT);
  pinMode(8,OUTPUT);
  pinMode(A0,INPUT);

  delay(2000);
}

void loop() {
  // put your main code here, to run repeatedly:

  for(s=0;s<=30;s++){ //Providing low voltage to the tracks to just turn on th locomotive's lights.
    motor_go();
    delay(10);
  }

  delay(4000);

  for(s=s;s<=50;s++){ //Starting the train.
    motor_go();
    delay(500);
  }

  delay(5000);

  for(s=s;s<=80;s++){ //Speeding up a bit.
    motor_go();
    delay(500);
  }

  delay(1000);

  while(digitalRead(A0)==LOW); //Wait for the train to cross the 'sensored' track.

  for(s=s;s<=maxSpeed;s++){ //Speeding up the train to maximum speed value set in the beginning.
    motor_go();
    delay(500);
  }

  delay(1000);
  while(digitalRead(A0)==LOW); //Wait for the train to cross the 'sensored' track.

  delay(2000);

  for(s=s;s!=100;s--){ //Slow down the train a bit.
    motor_go();
    delay(1000);
  }

  delay(4000);
  while(digitalRead(A0)==LOW); //Wait for the train to cross the 'sensored' track.

  for(s=s;s!=80;s--){ //Slow down the train furthur.
    motor_go();
    delay(500);
  }

  delay(4000);

  for(s=s;s!=60;s--){ //Slow down the train, preparing to stop.
    motor_go();
    delay(500);
  }
  delay(1000);
  while(digitalRead(A0)==LOW); //Wait for the train to cross the 'sensored' track.

  delay(1000);
  
  for(s=s;s!=20;s--){ //Reduce the voltage on the tracks to just let the locomotive lights turned on.
    motor_go();
    delay(250);
  }

  delay(1000);

  for(s=s;s!=0;s--){ //Stop the power supply to the track and power down the locomotive.
    motor_go();
    delay(125/2);
  }

  delay(1000*t); //Wait for the set time before starting all over again.
}

Make an oval loop of track as shown in the picture.

Remove the jumper connector from the pin marked 'ENB'.

Make the following connections:

• Connect the 'ENB' pin to pin D10 of the Arduino board.
• Connect the 'IN 3' pin to the pin D8 of the Arduino board.
• Connect the 'IN 4' pin to the pin D9 of the Arduino board.

Connect the output terminal's wires to the power feeder connector.

Make the following wiring connections:

• Connect the VCC pin to +5-volt pin of the Arduino board.
• Connect the GND pin to the GND pin of the Arduino board.
• Connect the OUT pin to the A0 pin of the Arduino board.

Use a re-railer to make sure that the wheels of the train sit perfectly well on the tracks.

Make sure no wiring connections are loose. Connect the Arduino board's power input to the power supply and turn it on.