How to Make an Autonomous Line-Following Robot | Arduino

In this post, I’ll show you how to make an autonomous line-following robot using Arduino and a reflectance sensor.

Requirements

Here are the requirements:

  • Make an autonomous line-following robot using Arduino and a reflectance sensor.

You Will Need

The following components are used in this project. You will need:

Directions

First grab the 0.25 inch thick foam board. Cut it into two 3/8 inch by 3/4 inch pieces.

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Glue both pads so that one is on top of the other.

Glue the stack of two pads to the underside of the board so that the middle of the stack is exactly in the center of the lower board.

The stack should be right in between both snap action switches. The front of the stack should be slightly behind the front edge of the board.

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Grab the header pins that came with the reflectance sensors. Cut the pin headers so that you have two sets of three pins. One set of three will be for one of the sensors and the other set of three will be for the other sensor.

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Insert the short end of the header pins into the reflectance sensors.

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Solder the short end of the header pins so that the header pins remain in place. Be careful not to solder big blobs that connect one short pin to another. It is a difficult soldering job because the pins are so close together. Just take your time. No need to hurry.

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Now grab the following 6 male-to-female jumper wires and hook up the female part as follows:

  • Black, red, yellow (Right sensor)
  • Green, orange, white (Left sensor)
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Get a piece of double-sided tape and attach the sensor to the underside of the board on top of small foam board stack.

The front of the sensor should be aligned with the front of the robot.

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Connect the 6 male-to-female jumper wires to the breadboard as follows:

  • White wire connects to c23
  • Orange wire connects to h12
  • Green wire connects to GND via h5.
  • Yellow wire connects to c25
  • Red wire connect to g12
  • Black wire connects to GND via h29
  • Connect a wire from a23 to analog pin 4 on the Arduino
  • Connect a wire from a25 to analog pin 5 on the Arduino
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If you have issues with the servos not moving, try connecting the ground on the reflectance sensor (the green and black wires) to their own ground on the Arduino.

Upload the following code to the Arduino board to test the reflectance sensors.

/**
 * This is a test of the reflectance
 * sensor of the line following robot.
 * 
 * @author Addison Sears-Collins
 * @version 1.0 2019-05-15
 */

#define line_left A4 // The IO pins connected to sensor
#define line_right A5

int irleft_reflect = 0; // Readings stored here
int irright_reflect = 0;

/*   
 *  This setup code is run only once, when 
 *  Arudino is supplied with power.
 */
void setup() { 
   Serial.begin (9600); // Set the baud rate
} 


/*
 * This is the main code that runs again and again while
 * the Arduino is connected to power.
 */
void loop() { 

  // Read the reflectance sensors
  // Values range from 0 to 1023, representing
  // analog voltage from 0 to 5 volts
  // 0 = solid white; 1023 = solid black
  irleft_reflect = analogRead(line_left);
  irright_reflect = analogRead(line_right);

  Serial.print ("Left:");      
  Serial.print ("\t");        
  Serial.print (irleft_reflect);
  Serial.print ("\t");
  Serial.print ("Right:");
  Serial.println (irright_reflect);
  
  delay(100);
}

Open the Serial Monitor to verify that the values are changing when you wave an object in front of the sensors.

Feel free to close down the Serial Monitor at this stage. We will now make the line course that the robot will follow.

Grab the white poster (22 inches by 28 inches), and also get the 0.75 inch black electrical tape.

Create a course that looks something like the image below. Be sure to keep at least a three-inch margin between the side of the poster board and the line course. Make sure the turns and the course are smooth, otherwise you will have problems.

line-following-robot-20

The course is ready, so upload the following sketch to the Arduino.

#include <Servo.h> // We are using servos, so add library

/**
 * This robot follows a line made with black electric
 * tape on white poster board.
 * 
 * @author Addison Sears-Collins
 * @version 1.0 2019-05-15
 */

// Each servo is an object with its own data and behavior
Servo left_servo;
Servo right_servo;

// Sensors connected to analog pins 4 (left sensor) and 5 (right sensor)
const int left_line = A4;
const int right_line = A5;

// Store sensor readings here
int irleft_reflect = 0;
int irright_reflect = 0;

// Try values between 400 and 800. 
// Helps determine if robot is over the line
int threshold = 800;           

/*   
 *  This setup code is run only once, when 
 *  Arudino is supplied with power.
 */
void setup() { 
  // Assign each servo to its own digital pin on the Arduino
  right_servo.attach(9);  
  left_servo.attach(10); 
} 

void loop() { 

  // Read the reflectance sensors
  irleft_reflect = analogRead(left_line);  
  irright_reflect = analogRead(right_line);

  // robot is right over the line
  if (irleft_reflect >= threshold &amp;&amp; irright_reflect >= threshold) {
    line_forward();   
  }

  // robot is veering off to the right
  if (irleft_reflect >= threshold &amp;&amp; irright_reflect <= threshold) {
    line_left_slip();  
    delay(4);
  }

  // robot is veering off to the left
  if (irleft_reflect <= threshold &amp;&amp; irright_reflect >= threshold) {
    line_right_slip();  
    delay(4);
  }

  // If robot has lost the line, go find it
  if (irleft_reflect < threshold &amp;&amp; irright_reflect < threshold) {
    line_right_spin();
    delay(20);
  }
}

// On the continuous rotation servo, the write() 
// method sets the speed of the servo.
// 0 is full speed in one direction.
// 180 is full speed in the other direction.
// ~90 is no movement (You will have to tweak to
//   get no movement).
void line_forward() {
  right_servo.write(0);  
  left_servo.write(180);
}
void line_right_slip() {
  right_servo.write(90);  
  left_servo.write(180);
}
void line_left_slip() {
  right_servo.write(0);  
  left_servo.write(90);
}
void line_right_spin() {
right_servo.write(180);  
  left_servo.write(180);
}
void line_left_spin() {
  right_servo.write(0);  
  left_servo.write(0);
}

Disconnect the USB cable from the Arduino, and place the Arduino on the floor.

Turn on the servos:

  • a13 to e3 = left servo ON
  • e13 to e28 = right servo ON
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Plug in the Arduino’s power.

Press the Reset button on the Arduino as you position the robot over the black electrical tape on the course. The Reset button is like unplugging the Arduino and plugging it in again.

Watch the robot in action!

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Video

How to Make a Remote Controlled Robot | Arduino

In this post, I’ll show you how to make a remote controlled robot using Arduino and a Sony Universal Remote Control.

Requirements

Here are the requirements:

  • Control a wheeled robot using a Sony Universal Remote Control.

You Will Need

The following components are used in this project. You will need:

Directions

First, get the infrared sensor. Bend the metal lead 0.25 inches below the base of the square sensor so that it makes a 90-degree angle.

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Cut the lead 3/8 inches below the point of the bend. The dome of the sensor should face the opposite direction of the 90-degree bend.

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Insert the infrared sensor into the Arduino board so that the pins are inside analog pins 0, 1, and 2. The dome of the infrared sensor should face upwards.

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Insert batteries into the Sony Universal remote control.

Set up the remote control so that it can operate a Sony television. The instructions for how to setup the remote control should be included inside the package that it came with.

Add the IRremote library to the Arduino IDE. Go to Sketch -> Include Library -> Manage Libraries and look for “IRremote.” Add it, and then restart the IDE.

Upload the IRtest sketch to the Arduino (see code below). This sketch will be used to test the remote control, whose buttons do the following:

  • 1: Left Turn (Forward)
  • 2: Forward
  • 3: Right Turn (Forward)
  • 4: Spin Left
  • 5: Stop
  • 6: Spin Right
  • 7: Left Turn (Reverse)
  • 8: Backwards
  • 9: Right Turn (Reverse)

Open the Serial Monitor, and press any number from 1 to 9. You should see that number show up in the Serial Monitor.

#include <IRremote.h>      

/**
 * This code tests the Sony Universal Remote Control
 * 
 * Credit: Gordon McComb, How to Make a Robot.
 * Book available here: https://amzn.to/2Q303ed
 * 
 * Code was modified by Addison Sears-Collins
 */

#define  show_code  false   // Test mode
                            // false means match to # buttons
                            // true means display raw code

const int RECV_PIN = A0;     // Receiver input on Analog 0
IRrecv irrecv(RECV_PIN);     // Define IR recever object
decode_results results;

/*   
 *  This setup code is run only once, when 
 *  Arudino is supplied with power.
 */
void setup() {
  pinMode(A1, OUTPUT);       // IR power, ground pins
  pinMode(A2, OUTPUT);
  digitalWrite(A1, LOW);     // The ground for the IR
  digitalWrite(A2, HIGH);    // Power to the IR
  irrecv.enableIRIn();       // Initiate the receiver
  Serial.begin(9600);        // Set the baud rate
}

void loop() {

  if (irrecv.decode(&amp;results)) {  // If valid value was received
    if(show_code) {                // If show_code=true 
      Serial.print("0x");
      Serial.println(results.value, HEX);  // Display raw hex
    } else {                      // else show_code=false
      switch (results.value) {    // Match button to Sony codes
        case 0x10:
          Serial.println("1");
          break;
        case 0x810:
          Serial.println("2");
          break;
        case 0x410:
          Serial.println("3");
          break;
        case 0xC10:
          Serial.println("4");
          break;
        case 0x210:
          Serial.println("5");
          break;
        case 0xA10:
          Serial.println("6");
          break;
       case 0x610:
          Serial.println("7"); 
          break;
        case 0xE10:
          Serial.println("8");
          break;
        case 0x110:
          Serial.println("9");
          break;
      }        
    }
    irrecv.resume();    // Receive the next value
    delay(10);          // Pause for 10 milliseconds
  }

}

Now, upload the code below to the Arduino. Remove the USB cord. Place the robot on the floor. Turn on the servos. Insert the 9V battery jack into the Arduino, and drive the robot around the room!

#include <Servo.h> 

/**
 * This code runs the remote controlled robot
 * 
 * 
 * @author Addison Sears-Collins
 * @version 1.0 2019-05-14
 */
 
Servo left_servo;              // Define left servo
Servo right_servo;             // Define right servo

#include <IRremote.h>
int RECV_PIN = A0;
IRrecv irrecv(RECV_PIN);
decode_results results;
volatile int active_left = LOW;
volatile int active_right = LOW;
boolean started = false;

void setup() {
  // Set pin modes for switches
  pinMode(2, INPUT);
  pinMode(3, INPUT);
  pinMode(4, OUTPUT);
  digitalWrite(2, HIGH);
  digitalWrite(3, HIGH);
  digitalWrite(4, LOW);     // Serves as ground connection
  
  pinMode(A1, OUTPUT);       // IR power, ground pins
  pinMode(A2, OUTPUT);
  digitalWrite(A1, LOW);     // IR ground
  digitalWrite(A2, HIGH);    // IR power

  right_servo.attach(9);    // Set right servo to digital pin 9  
  left_servo.attach(10);    // Set left servo to digital pin 10
  irrecv.enableIRIn();     // Start the receiver
  
  Serial.begin(9600);
    
  // Set up interrupts
  attachInterrupt(0, bump_right, FALLING);
  attachInterrupt(1, bump_left, FALLING);
  
  started = true;
}

void loop() {
  
  if (active_left == HIGH) {           // If left bumper hit
    go_backwards();
    delay(500); 
    spin_right();
    delay(1000);
    go_forward();
    active_left = LOW;
    Serial.println("active_left");
  }
  
  if (active_right == HIGH) {          // If right bumper hit
    go_backwards();
    delay(500); 
    spin_left();
    delay(1000);
    go_forward();
    active_right = LOW;
    Serial.println("active_right");  
  }
  
  if (irrecv.decode(&amp;results)) {
    switch (results.value) {
      case 0x10:
        Serial.println("1");     // Turn left forward
        left_turn_fwd();
        break;
      case 0x810:
        Serial.println("2");     // Forward
        go_forward();
        break;
      case 0x410:
        Serial.println("3");     // Turn right forward
        right_turn_fwd();
        break;
      case 0xC10:
        Serial.println("4");    // Spin left
        spin_left();
        break;
      case 0x210:
        Serial.println("5");    // Stop
        stop_all();
        break;
      case 0xA10:
        Serial.println("6");    // Spin right
        spin_right();
        break;
     case 0x610:
        Serial.println("7");    // Turn left reverse
        left_turn_backwards();
        break;
      case 0xE10:
        Serial.println("8");    // Reverse
        go_backwards();
        break;
      case 0x110:
        Serial.println("9");    // Turn right reverse
        turn_right_backwards();
        break;
    }        
    irrecv.resume(); // Receive the next value
    delay(2);
  }
}

// Routines for forward, reverse, turns, and stop
void go_forward() {
  left_servo.write(180);
  right_servo.write(0);
}
void go_backwards() {
  left_servo.write(0);
  right_servo.write(180);
}
void spin_right() {
  left_servo.write(180);
  right_servo.write(180);
}
void spin_left() {
  left_servo.write(0);
  right_servo.write(0);
}
void right_turn_fwd() {
  left_servo.write(180);
  right_servo.write(90);
}
void left_turn_fwd() {
  left_servo.write(90);
  right_servo.write(0);
}
void left_turn_backwards() {
  left_servo.write(90);
  right_servo.write(180);
}
void turn_right_backwards() {
  left_servo.write(0);
  right_servo.write(90);
}
void stop_all() {
  left_servo.write(90);
  right_servo.write(90);
}

// Interrupt service routines
void bump_left() {
  if (started)
    active_left = HIGH;
}
void bump_right() {
  if (started) 
    active_right = HIGH;
}

Video

How to Make an Obstacle Avoiding Robot | Arduino

In this post, I’ll show you how to give your robot the ability to “see.” We’ll create an obstacle avoiding robot using Arduino and an ultrasonic sensor.

An ultrasonic sensor works by producing high frequency sound waves and then measuring the time it takes for the sound to reflect back to the sensor. Objects that are closer to the robot reflect sound back faster than objects that are farther away. This data is then used by the robot to avoid running into objects. Bats use ultrasound in order to locate food and avoid obstacles inside dark caves. Dolphins emit ultrasound as well in order to detect and recognize objects.

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Video

Here is a video of what we will build in this tutorial.

Requirements

Here are the requirements:

  • Make a robot that avoids obstacles using an ultrasonic sensor.

You Will Need

The following components are used in this project. You will need:

Directions

First, get your ultrasonic distance sensor and place the far left pin (the one labeled VCC, the supply voltage) into the solderless breadboard in cell j12.

Now, wire the ultrasonic sensor to the Arduino as follows. Remember that each cell in a single row of 5 cells on a solderless breadboard is electrically connected (e.g. j12 is connected to f12, g12, h12, and i12 electrically):

  • VCC on the sensor connects to 5V on the Arduino
  • Echo on the sensor connects to Digital Pin 8 on the Arduino
  • Trig (stands for trigger) on the sensor connects to Digital Pin 7 on the Arduino
  • GND (stands for Ground) on the sensor connects to ground on the solderless breadboard
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Now, upload the following sketch to the Arduino to test the ultrasonic sensor.

/**
 *  This program tests the ultrasonic
 *  distance sensor
 * 
 * @author Addison Sears-Collins
 * @version 1.0 2019-05-13
 */

/* Give a name to a constant value before
 * the program is compiled. The compiler will 
 * replace references to Trigger and Echo with 
 * 7 and 8, respectively, at compile time.
 * These defined constants don't take up 
 * memory space on the Arduino.
 */
#define Trigger 7
#define Echo 8

/*   
 *  This setup code is run only once, when 
 *  Arudino is supplied with power.
 */
void setup(){

  // Set the baud rate to 9600. 9600 means that 
  // the serial port is capable of transferring 
  // a maximum of 9600 bits per second.
  Serial.begin(9600);

  // Define each pin as an input or output.
  pinMode(Echo, INPUT);
  pinMode(Trigger, OUTPUT);
}

void loop(){

  // Make the Trigger LOW (0 volts) 
  // for 2 microseconds
  digitalWrite(Trigger, LOW);
  delayMicroseconds(2);

  // Emit high frequency 40kHz sound pulse
  // (i.e. pull the Trigger) 
  // by making Trigger HIGH (5 volts) 
  // for 10 microseconds
  digitalWrite(Trigger, HIGH);
  delayMicroseconds(10);
  digitalWrite(Trigger, LOW); 

  // Detect a pulse on the Echo pin 8. 
  // pulseIn() measures the time in 
  // microseconds until the sound pulse
  // returns back to the sensor.
  int distance = pulseIn(Echo, HIGH);

  // Speed of sound is:
  // 13511.811023622 inches per second
  // 13511.811023622/10^6 inches per microsecond
  // 0.013511811 inches per microsecond
  // Taking the reciprocal, we have:
  // 74.00932414 microseconds per inch 
  // Below, we convert microseconds to inches by 
  // dividing by 74 and then dividing by 2
  // to account for the roundtrip time.
  distance = distance / 74 / 2;

  // Print the distance in inches
  Serial.println(distance);

  // Pause for 100 milliseconds
  delay(100);
}

As soon as uploading is finished and with the USB cable still connected to the Arduino, click on the green magnifying glass in the upper right of the IDE to open the Serial Monitor.

Make sure you have the following settings:

  • Autoscroll: selected
  • Line ending: No Line ending
  • Baud: 9600 baud

Place any object in front of the sensor and move it back and forth. You should see the readings on the Serial Monitor change accordingly.

Now, close the Serial Monitor and upload the following sketch to the Arduino.

#include <Servo.h> 

/**
 * This robot avoids obstacles 
 * using an ultrasonic sensor.
 * 
 * @author Addison Sears-Collins
 * @version 1.0 2019-05-13
 */

// Create two servo objects, one for each wheel
Servo right_servo;
Servo left_servo;

/* Give a name to a constant value before
 * the program is compiled. The compiler will 
 * replace references to Trigger and Echo with 
 * 7 and 8, respectively, at compile time.
 * These defined constants don't take up 
 * memory space on the Arduino.
 */
#define Trigger 7
#define Echo 8

/*   
 *  This setup code is run only once, when 
 *  Arudino is supplied with power.
 */
void setup(){
  
  // Set the baud rate to 9600. 9600 means that 
  // the serial port is capable of transferring 
  // a maximum of 9600 bits per second.
  Serial.begin(9600);

  right_servo.attach(9);      // Right servo to pin 9
  left_servo.attach(10);      // Left servo to pin 10  

  // Define each pin as an input or output.
  pinMode(Echo, INPUT);
  pinMode(Trigger, OUTPUT);

  // Initializes the pseudo-random number generator
  // Needed for the robot to wander around the room
  randomSeed(analogRead(3));

  delay(200);     // Pause 200 milliseconds               
  go_forward();   // Go forward
}

/*
 * This is the main code that runs again and again while
 * the Arduino is connected to power.
 */
void loop(){
  int distance = doPing();

  // If obstacle <= 2 inches away
  if (distance >= 0 &amp;&amp; distance <= 2) {    
    Serial.println("Obstacle detected ahead");  
    go_backwards();   // Move in reverse for 0.5 seconds
    delay(500);

    /* Go left or right to avoid the obstacle*/
    if (random(2) == 0) {  // Generates 0 or 1, randomly        
      go_right();  // Turn right for one second
    }
    else {
      go_left();  // Turn left for one second
    }
    delay(1000);
    go_forward();  // Move forward
  }
  delay(50); // Wait 50 milliseconds before pinging again
}

/*
 * Returns the distance to the obstacle as an integer
 */
int doPing () {
  int distance = 0;
  int average = 0;

  // Grab four measurements of distance and calculate
  // the average.
  for (int i = 0; i < 4; i++) {

    // Make the Trigger LOW (0 volts) 
    // for 2 microseconds
    digitalWrite(Trigger, LOW);
    delayMicroseconds(2);

    
    // Emit high frequency 40kHz sound pulse
    // (i.e. pull the Trigger) 
    // by making Trigger HIGH (5 volts) 
    // for 10 microseconds
    digitalWrite(Trigger, HIGH);
    delayMicroseconds(10);
    digitalWrite(Trigger, LOW);
     
    // Detect a pulse on the Echo pin 8. 
    // pulseIn() measures the time in 
    // microseconds until the sound pulse
    // returns back to the sensor.    
    distance = pulseIn(Echo, HIGH);

    // Speed of sound is:
    // 13511.811023622 inches per second
    // 13511.811023622/10^6 inches per microsecond
    // 0.013511811 inches per microsecond
    // Taking the reciprocal, we have:
    // 74.00932414 microseconds per inch 
    // Below, we convert microseconds to inches by 
    // dividing by 74 and then dividing by 2
    // to account for the roundtrip time.
    distance = distance / 74 / 2;

    // Compute running sum
    average += distance;

    // Wait 10 milliseconds between pings
    delay(10);
  }

  // Return the average of the four distance 
  // measurements
  return (average / 4);
}

/*   
 *  Forwards, backwards, right, left, stop.
 */
void go_forward() {
  right_servo.write(0);
  left_servo.write(180);
}
void go_backwards() {
  right_servo.write(180);
  left_servo.write(0);
}
void go_right() {
  right_servo.write(180);
  left_servo.write(180);
}
void go_left() {
  right_servo.write(0);
  left_servo.write(0);
}
void stop_all() {
  right_servo.write(90);
  left_servo.write(90);
}

Disconnect the USB cable from the Arduino, and place the Arduino on the floor.

Turn on the servos:

  • a13 to e3 = left servo ON
  • e13 to e28 = right servo ON

Then plug in the Arduino’s power.

Watch the Obstacle Avoiding Robot move!

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