2-Way Sound Sensitive Line Follower

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SUMMER INTERNSHIP PROGRAM 2011

PROJECT REPORT

TITLE

2-Way Sound Sensitive Line Follower

Made under the supervision of

Mr. Tarique Aziz

Research Engineer

Robosapiens Technologies Pvt. Ltd

Made by

Abhishek Das

SIP/10/2096

June, 2011



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Acknowledgements

I would like to thank Mr. Tarique Aziz for his help throughout the term of

this project. I am indebted to him, for his thoughtful supervision and clear

advice.

My family and friends have also made this an enjoyable task as a result of

both their personal support and the comments that only friends can make.



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Table of Contents

Acknowledgements 2

Table of Contents 3

1. Introduction

1.1. Objectives

1.2. Project Overview

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2. Components Used

2.1. DC Geared Motors

2.2. IR Sensors

2.2.1. IR LED

2.2.2. Photodiode

2.2.3. Operational Amplifier

2.3. Motor driver IC (L293D)

2.4. AVR Microcontroller (ATmega8)

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3. Working 11

4. Algorithm 11

5. Source Code 12

6. References and Resources 13



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1. INTRODUCTION

1.1. Objectives

Following were the main objectives of the project.

1. To develop a line following robot that follows a black path on white

background, unaffected by any stray sounds, and stops at the end.

2. To make the robot turn around and return back as a line follower

when a sound is produced.

1.2. Project Overview

Line follower is a machine that can follow a path. The path can be visible

like a black line on a white surface (or vice-versa) or it can be invisible

like a magnetic field. Sensing a line and manoeuvring the robot to stay

on course, while constantly correcting wrong moves using feedback

mechanism forms a simple yet effective closed loop system. As a

programmer you get an opportunity to ‘teach’ the robot how to follow

the line thus giving it a human-like property of responding to stimuli.

Practical applications of a line follower: Automated cars running on

roads with embedded magnets; guidance system for industrial robots

moving on shop floor etc.

The principle of the line follower is based on sensing the background

surface making use of IR sensor. Basically IR sensor takes input by

detecting the reflection of the IR rays from the surface and accordingly

gives its output to the motors.



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2. COMPONENTS USED

2.1. DC Geared Motors

In our line follower DC geared motors are used.

• WHY DC MOTOR?

Easy to control

Require only two signals

To change the direction of rotation, just reverse the polarity

Speed can be controlled by the voltage

• USE OF GEARS

To provide enough torque

Increases the torque at the expense of speed

2.2.

IR Sensors

Sensors are basically electronic devices which are used to sense the

changes that occur in their surroundings. The change may be in colour,

temperature, moisture, sound, heat etc. They sense the change and work

accordingly. IR sensors consist of emitter and detector. Emitter emits

the IR rays and detector detects it.

The IR sensor basically consists of three components:

IR LED (emitter)

Photodiode (detector)

Operational Amplifier (LM358)



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2.2.1. IR LED

IR LED is a light emitting diode which emits IR radiations. The basic

function of the emitter is to convert electricity into light. It works on

the principle of recombination of the electron-hole pair. As in the

conduction band of a diode, electrons are the majority carrier and in

the valence band, holes are majority carrier. So when an electron

from a conduction band recombines with a hole of valance band,

some amount of energy is released and this energy is in the form of

light. The amount of energy released depends upon the forbidden

energy gap. The IR Led has two legs, the leg which is longer is

positive and other leg is negative.

2.2.2. Photodiode

The photodiode is a p-n junction diode which is connected in reverse

bias. The basic function of the detector is to convert light into

electricity. As its name implies, it works effectively only when a

certain number of photons or certain amount of light falls on it. When

no light is falling on the photodiode it has infinite resistance and acts



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as an open switch but as the light starts falling on the photodiode, the

resistance decreases and when full intensity of light is incident on the

photodiode then its resistance becomes zero and it starts acting like a

closed switch.

2.2.3. Operational Amplifier

It is a DC-coupled high gain amplifier with differential inputs and

single output. Typically the output of the op-amp is controlled by

either negative feedback or positive feedback. Due to the fact that it performs several operations like addition, subtraction, multiplication,

integration etc, it is named as operational amplifier. It has two inputs,

inverted (Pin 2) and non-inverted input (Pin3). The signal which is

applied to the inverted input gives output 180 degree out of phase

with input whereas in the non-inverted input gives output in phase

with that of input. Op-amp has a variety of uses in different

electronics devices. In the line follower it is used in the comparator

mode. The op-amp IC which is used here is LM358, which is an 8-pin

IC having two inbuilt op-amps. In the comparator mode, the

reference voltage is set at the inverted input pin and then it is

compared with the input at non inverted pin. As the voltages at two

input pins of op-amp is compared, as the voltage at Pin 3 exceeds the

reference voltage at Pin 2 the output of the comparator becomes high

(5 V) otherwise it becomes low (0 V). The reference voltage at Pin 2

is set with the help of variable resistor.



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Internal block diagram of LM358 IC

Circuit diagram of IR sensor



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2.3. Motor Driver IC (L293D)

L293D IC is a dual H-bridge motor driver IC. One H-bridge is capable of

driving a DC motor bidirectionally. L293D IC is a current enhancing IC.As the output from the sensor is not able to drive motors by itself so

L293D is used for this purpose. L293D is a 16 pin IC having two enable

pins which should always high to enable both the H-bridges.

Pin Diagram of L293D

2.4. AVR Microcontroller (ATmega8)

“Atmel's AVR® microcontrollers have a RISC core running single cycle

instructions and a well-defined I/O structure that limits the need for

external components. Internal oscillators, timers, UART, SPI, pull-up

resistors, pulse width modulation, ADC, analog comparator and watch-dog

timers are some of the features you will find in AVR devices. AVR

instructions are tuned to decrease the size of the program whether the





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3. WORKING

The robot uses IR sensors to sense the line. The output of the sensors is an

analog signal which depends on the amount of light reflected back, this

analog signal is given to the comparator to produce 0s and 1s which are

then fed to the µC.

When a sensor is on the line it reads 0 because rays are not reflected back

and when it is off the line it reads 1 because reflected rays are incident on

the photodiode.

4. ALGORITHM

1. If both sensors read 1, go straight.

2. If left sensor reads 0 and right sensor reads 1, turn left.

3. If right sensor reads 0 and left sensor reads 1, turn right.

4. If both sensors read 0, stop and wait for sound.

5. If motors are not running and sound is detected, turn around.

6. Go to step 1



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5. SOURCE CODE

#include <avr/io.h>

#include <util/delay.h>

void main ()

{

int left, right, sound;

DDRB = 0xff;

DDRC = 0x00;

while (1)

{

left = PINC & 0b0100000;

right = PINC & 0b0010000;

sound = PINC & 0b0000001;if (left==0b0100000 && right==0b0010000)

{

PORTB = 0b00001001;

_delay_ms(50);

}

if (left==0b0000000 && right==0b0010000)

{

PORTB = 0b00000101;

_delay_ms(50);

}

if (left==0b0100000 && right==0b0000000)

{

PORTB = 0b00001010;

_delay_ms(50);

}

if (left==0b0000000 && right==0b0000000)

{

PORTB = 0b00000000;

if (sound==0b0000001)

{

PORTB = 0b00001010;

_delay_ms(100000);

_delay_ms(100000);

_delay_ms(100000);

_delay_ms(100000);

_delay_ms(100000);

}

}

}

}



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6. REFERENCES AND RESOURCES

Books:

Robotics with AVR – Toshendra K. Sharma

Links:

Atmel Corp.

Makers of the AVR microcontroller

http://www.atmel.com

One of the best sites AVR sites

http://www.avrfreaks.net

WinAVR

An open source C compiler for AVR

http://sourceforge.net/projects/winavr

Robotics India

An Indian site devoted to robotics. Must see

http://www.roboticsindia.com/

Tools:

AVR Studio

Compiler:

WinAVR

Programmer:

AVR Loader v1.1 (GUI based on AVRDude)

http://www.atmel.com/


http://www.avrfreaks.net/










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2-Way Sound Sensitive Line Follower