line follower robot is a mobile machine that can detect and follow line which is drawn on the floor

8/2/2019 Line Follower Robot is a Mobile Machine That Can Detect and Follow Line Which is Drawn on the Floor

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CHAPTER ONE

INTRODUCTION

1.1 General Overview

Line follower robot is a mobile machine that can detect and follow line

which is drawn on the floor. 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. Robot should

read for identifying his position in some time, after that, the control system

(AVR) will create for the line follower some orders to respect components in

purposes of making correct movements of the line follower.

Sensing a line and maneuvering the line follower to stay on course, while

constantly correcting wrong moves using feedback mechanism forms a simple

yet effective closed loop system.

Although a Line Followers purpose in life is to follow a line, other issues

have to be discussed for example, if the track that it is following is on a table, it

should also have some form of detecting the edge of the table so it wont fall Off.

If the robot is moving fast, it has to have fast reflexes so that if the line turns itwill be able to compensate its direction so it wont leave the track.

Line Follower needs light to move, but sometimes if an external light

source is strong enough it might confuse the robot. If the robot is doing its

preferred activity outdoors, a whole set of issues have to deal with, such as

sunlight, dust, uneven terrain and other issues.

The Line Follower in this project may not be able to handle all the

conditions listed above, but as long as it follows the line it will be satisfied.

Most, if not all Line Followers, are battery powered. They must have a way to

define the direction in which they must go. They must also be able to accept

input from the external world and use that input to decide what to do next.


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1.2 Components

The block diagram below in figure 1.1 shows those basic four components to

build the line follower which are:

1- The sensors array.2- The microcontroller (ATmega16).3- Motor driver (L293D).4- Two Dc motors.

Figure1.1 the line follower block diagram

1.2.1 Sensors

The sensors are one of the most important components of the functional

line follower robot ;they are robots eyes, ears, sense of touch, balance and only

source of input from external environment The line follower uses IR sensors to

sense the line, an array of 2 IR LEDs (Tx) and sensors (Rx), facing the ground.

The output of the sensors is an analog signal which depends on the amount of

light reflected back, this analog signal is connected to the microcontrollers pins

that contain an analog to digital converter (ADC).


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1.2.2 Microcontroller

A microcontroller often serves as the brain of a mechatronic system. It

can be programmed to interact with both the hardware of the system and the

user. Even the most basic microcontroller can perform simple math operations,

control digital outputs, and monitor digital inputs. As the computer industry has

evolved, so has the technology associated with microcontrollers. Newer

microcontrollers are much faster, have more memory, and have a host of input

and output features that dwarf the ability of earlier models. Most modern

controllers have analog-to-digital converters, high-speed timers and counters,

interrupt capabilities, outputs that can be pulse-width modulated, serial

communication ports, etc.

There are many types of microcontrollers but ATmega-16 is the one used

in this project to control the robot movements.

The ATmega16 is a low-power CMOS (complementary metal oxide

semiconductor) 8-bit microcontroller based on the AVR enhanced RISC

(reduced instruction set computing) architecture. By executing powerful

instructions in a single clock cycle, the ATmega16 achieves throughputsapproaching 1 MIPS per MHz allowing the system to optimize power

consumption versus processing speed.

The AVR core combines a rich instruction set with 32 general purpose

working registers. All the 32 registers are directly connected to the Arithmetic

Logic Unit (ALU), allowing two independent registers to be accessed in one

single instruction executed in one clock cycle. The resulting architecture is more

code efficient while achieving throughputs up to ten times faster than

conventional CISC microcontrollers.[4]


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1.2.3 Motor driver

Another component is the motor driver L293D which allows the

microcontrollers to govern the movements of the line follower. Some of the

microcontroller outputs are connected to the motor driver inputs that are how the

microcontroller controls the motor movement throughout the output it gives to

the motor driver.

L293D is dual H-Bridge motor drive, so with one IC we can interface two

DC motors which can be controlled in both clockwise and counter clockwise

direction. L293D has output current of 600mA and peak output current of 1.2A

per channel. Moreover for protection of circuit from back EMF output diods are

included within the IC. The output supply has a wide range from 4.5V to 36V,

which has made L293D the best choice for the DC motor driver.[7]

1.2.4 DC motors

The Direct Current (DC) motor is one of the first machines devised to

convert electrical energy to mechanical power. Its origin can be traced to

machines conceived and tested by Michael Faraday, the experimenter whoformulated the fundamental concepts of electromagnetism. These concepts

basically state that if a conductor, or wire, carrying current is placed in a

magnetic field, a force will act upon it. The magnitude of this force is a function

of strength of the magnetic field, the amount of current passing through the

conductor and the orientation of the magnet and conductor. The direction in

which this force will act is dependent on the direction of current and direction of

the magnetic field.

Electric motor design is based on the placement of conductors (wires) in a

magnetic field. A winding has many conductors, or turns of wire, and the

contribution of each individual turn adds to the intensity of the interaction. The


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force developed from a winding is dependent on the current passing through the

winding and the magnetic field strength. If more current is passed through the

winding, then more force (torque) is obtained. In effect, two magnetic fields

interacting cause movement: the magnetic field from the rotor and the magnetic

field from the stators attract each other. This becomes the basis of both AC and

DC motor design.

The figure1.2 below shows the state diagram for the line follower

Figure 1.2 state diagram of the line follower

The state diagram above in figure1.2 explains the strategy the line follower takes

to deal with all possible conditions.


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1.3 The Objectives of the Project

The main aim of the project is to design a line follower which is a simple

robotics application, the follower designed for repetitive tasks which use the

same path a lot and that helps to reduce the need for a human operator

1.4 The Applications of the Line Follower

The line follower is used in many applications, It might be used in a

warehouse where the follower follows 'tracks' to and from the shelves they stock

and retrieve from. The line follower is also can be used as a guider to guide

the visitors from the entrance to the main office. There are cases where

smarter versions of line followers are used to deliver mail within an office

building and deliver medications in a hospital.

1.5 Project Layout

Chapter one represents a general overview of the line followers and its

applications. Chapter two discusses the AVR microcontroller in general and

ATmega16 microcontroller in details and the programming language used to

write the control program. Chapter three shows architecture of the line follower

and the components used in the design. Chapter four discusses the principle of

operation of the line follower and explains the BASCOM code which controls

the movement of the follower. Chapter five contains the recommendations and

conclusion.


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CHAPTER TWO

MICROCONTROLLER2.1 Introduction

A microcontroller is a computer-on-a-chip or a single-chip computer.

Micro suggests that the device is small, and controller tells that the device might

be used to control objects, processes, or events. Another term to describe a

microcontroller is embedded controller, because the microcontroller and its

support circuits are often built into, or embedded in, the devices they control.

Microcontrollers involves in all kinds of things these days. Any device

that measures, stores, controls, calculates, or displays information is a candidate

for putting a microcontroller inside. The largest single use for microcontrollers is

in automobiles just about every car manufactured today includes at least one

microcontroller for engine control, and often more to control additional systems

in the car. In desktop computers, microcontrollers, inside keyboards, modems,

printers, and other peripherals, in test equipment, microcontrollers make it easy

to add features such as the ability to store measurements, to create and store user

routines, and to display messages and waveforms. Consumer products that use

microcontrollers include cameras, video recorders, compact-disk players, and

ovens. And these are just a few examples.

A microcontroller is similar to the microprocessor inside a personal

computer. Examples of microprocessors include Intels 8086, Motorolas 68000,

and Zilogs Z80. Both microprocessors and microcontrollers contain a (Central

Processing Unit) CPU. The CPU executes instructions that perform the basic

logic, math, and data moving functions of a computer. To make a complete


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computer, a microprocessor requires memory for storing data and programs, and

input/output (I/O) interfaces for connecting external devices like keyboards and

displays.

Microcontrollers are characterized by how many bits of data they process atonce, with a higher number of bits generally indicating a faster or more powerful

chip. Eight-bit chips are popular for simpler designs, but 4-bit, 16-bit, and 32-bit

architectures are also available.

All microcontrollers have a defined instruction set, which consists of the

binary words that cause the CPU to carry out specific operations. For example,

the instruction 0010 0110 tells an 8052 to add the values in two locations. Thebinary instructions are also known as operation codes (Opcodes) for short. The

opcodes perform basic functions like adding, subtracting, logic operations,

moving and copying data, and controlling program branching.

Inside, microcontrollers are little more than a carefully designed array of

logic gates and memory cells, but modern fabrication processes allow thousands

of these to fit on a single chip. Since the basic functions of a microcontroller

performing arithmetic, logic, data-moving, and program branching functions are

common ones that are useful in many applications, its practical to design a chip

that performs these functions. The user accesses the abilities of the

microcontroller by writing a program that performs the desired functions. The

microcontroller contains all of the elements of a computer on a single chip.

Using a microcontroller can reduce the number of components and thus the

amount of design work and wiring required for a project. [4]


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2.2 Architectures of Microcontrollers

Every microcontroller must have memory space to store a program (code)

and data. While code provides instructions to the CPU, the data provides the

information to be processed. The CPU uses buses (wire traces) to access the code

ROM (Read Only Memory) and RAM (Random Access Memory) memory

space. There are two types of microcontroller architectures Harvard architecture

and von Neumann architecture.

2.2.1Von Neumann architecture

In von Neumann Architecture the process of accessing the code or data could

cause them to get in each other's way and slow down the processing speed of the

CPU, because each had to wait for the other to finish fetching. The data and

instructions use the same buses.

Figure 2.1 von Neumann architecture

2.2.2 Harvard architecture

To speed up the process of program execution, some CPUs use Harvard

architecture. In Harvard architecture, the instruction memory and the data

memory are separate, have separate bus for the code and data memory, and

sometimes have different sizes. [3]


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Figure 2.2 Harvard architecture

2.3 Atmel AVR

The AVR is a modified Harvard architecture 8-bit RISC (Reduced

Instruction Set Computer) single chip microcontroller which was developed by

Atmel in 1996. The AVR was one of the first microcontroller families to use on-

chip flash memory for program storage, as opposed to One-Time Programmable

ROM, EPROM(Erasable Programmable Read Only Memory) , or EEPROM(

Electrically Erasable Programmable Read Only Memory) used by other

microcontrollers at the time. The Atmel AVR and the Microchip PIC are very

similar (Harvard architecture) lines of microcontrollers.

2.3.1 Advantages of Atmel AVR

1. Cost. At the moment, the very lowest-price microcontroller available fromany manufacturer is the Atmel AVR ATtiny116 MHz FLASH.

2. Speed: Not only are most AVRs capable of 20MHz (even really cheapones like the ATtiny25/45/85 and ATmega48), but they actually run at

near 20 MIPS; the PIC chip only run at 5 MHz with a 20 MHz oscillator

frequency. In addition, with the better addressing modes and registers of
http://en.wikipedia.org/wiki/Modified_Harvard_architecturehttp://en.wikipedia.org/wiki/8-bithttp://en.wikipedia.org/wiki/Reduced_instruction_set_computerhttp://en.wikipedia.org/wiki/Microcontrollerhttp://en.wikipedia.org/wiki/Atmelhttp://en.wikipedia.org/wiki/Flash_memoryhttp://en.wikipedia.org/wiki/Programmable_read-only_memoryhttp://en.wikipedia.org/wiki/Programmable_read-only_memoryhttp://en.wikipedia.org/wiki/EPROMhttp://en.wikipedia.org/wiki/EPROMhttp://en.wikipedia.org/wiki/EEPROMhttp://en.wikipedia.org/wiki/EEPROMhttp://en.wikipedia.org/wiki/EEPROMhttp://en.wikipedia.org/wiki/EPROMhttp://en.wikipedia.org/wiki/Programmable_read-only_memoryhttp://en.wikipedia.org/wiki/Programmable_read-only_memoryhttp://en.wikipedia.org/wiki/Flash_memoryhttp://en.wikipedia.org/wiki/Atmelhttp://en.wikipedia.org/wiki/Microcontrollerhttp://en.wikipedia.org/wiki/Reduced_instruction_set_computerhttp://en.wikipedia.org/wiki/8-bithttp://en.wikipedia.org/wiki/Modified_Harvard_architecture


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the AVRs, most operation can be done in only one instruction, where it

often takes more than one instruction to do the same thing on a PIC.

3. Peripherals: Many Atmel AVR controllers, like many Microchip PICcontrollers, have a built-in 10 bit ADC. Some have LCD (Liquid Cristal

Display) or USB drivers.

4. One big advantage of AVRs is that they are supported by the GNUCompiler Collection (GCC)."

2.3.2 Disadvantages of Atmel AVR

1. Single source: only available from Atmel.

2. Power: Atmel AVRs have fairly low power, but the TI MSP430 series

has the lowest power of any microcontroller.

3. Speed: near 20MIPS is great, but the SX chips regularly run at near

50MIPS and can run at 75 or even 100 (in rare cases)

2.3.3 Common misperceptions

Some people think the fastest Microchip PIC (20 MHz 4:1 pipeline) is as

fast as the fastest Atmel AVR (20 MHz 1:1 pipeline). They are wrong. The PIC

is actually processing instructions at 5 MIPS and the AVR is at just under 20

MIPS. Also, the AVR instruction set is larger, so in many cases, it is getting

more done in fewer cycles. [9]
http://www.piclist.com/techref/ti/msp430/index.htmhttp://www.sxlist.com/http://www.sxlist.com/http://www.piclist.com/techref/ti/msp430/index.htm


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2.3.4 Groups of Atmel AVR

The AVR line is divided into two major groups; Tiny and Mega, with

some additional special function versions for specific applications such as

lighting, automotive, battery management, and LCD drivers.

2.3.4.1 Mega AVR

These are powerful microcontrollers with more than 120 instructions and

lots of different peripheral capabilities, which can be used in different designs.

Table 2.1 shows the types of mega AVR. Some of their characteristics are as

follows:

Program memory: 4K to 256K bytes. Package: 28 to 100 pins. Extensive peripheral set. Extended instruction set: They have rich

instruction set.

Table 2.1 types of mega AVR

Part Num.Code

ROM

Data

RAM

Data

EEPROM

I/O

pinsADC Timers

AT mega 8 8K 1K 0.5K 23 8 3

AT mega 16 16K 1K 0.5K 32 8 3

AT mega 32 32K 2K 1K 32 8 3

AT mega 64 64K 4K 2K 54 8 4

AT mega 1280 128K 8K 4K 86 16 6


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2.3.4.2 Tiny AVR

As its name indicates, the microcontrollers in this group have less

instructions and smaller packages in comparison to mega family. Some

characteristics are as follows:

Program memory: 1K to 8K bytes. Package: 8 to 28 pins. Limited peripheral set. Limited instruction set: the instruction sets are limited. For example,

some of them do not have the multiply instruction.[3]

2.4 ATmega16

The Atmel AT mega 16 is equipped with 32 general purpose 8-bit

registers that are tightly coupled to the processors arithmetic logic unit within

the CPU. Also, the processor is designed following the Harvard Architecture

format. That is, it is equipped with separate, dedicated memories and buses for

program and data information. The register-based Harvard Architectures coupled

with the RISC-based instruction set allows for fast and efficient program

execution and allows the processor to complete an assembly language instruction

every clock cycle. Atmel indicates the AT mega 16 can execute 16 million

instructions per second when operating at a clock speed of 16 MHz.


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2.4.1 Atmega16 architecture overview

The AT mega 16 has external connections for power supplies (Vcc, GND,

Avcc, and AREF), an external time base (XTAL1 and XTAL2) input pins to

drive its clock, processor reset(active low RESET), and four 8-bit ports (PA0-

PA7, PB0-PB7, PC0-PC7, PD0-PD7), which are used to interact with the

external world, these ports may be used as general purpose digital input/output

(I/O) ports or they may be used for the alternate function. The ports are

interconnected with the AT mega 16s CPU and internal subsystems via an

internal bus. The AT mega 16 also contains a timer subsystem, an analog to

digital converter (ADC), an interrupt subsystem, memory components, and acommunication subsystem.

2.4.1.1 Analog to digital converter

The AT mega16 is equipped with an eight-channel ADC. The ADC

converts an analog signal from the outside world into a binary representation

suitable for use by the microcontroller. The AT mega16 ADC has 10-bit

resolution. This means that an analog voltage between 0 and 5V will be encoded

into one of 1024 binary representations between (000)16 and (3FF) 16. This

provides the AT mega16 with a voltage resolution of approximately 4.88 Mv.[2]


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2.5 Pin Description

Figure 2.3 below shows the pins of at mega 16 microcontroller:

Figure 2.3 pin description of Atmega16

VCC

Digital supply voltage.

GND

Ground.

Port A (PA7..PA0)

Port A serves as the analog inputs to the digital (ADC). Port A also serves

as an 8-bit bi-directional I/O port, if the (ADC) is not used. Port pins can provide

internal pull-up resistors (selected for each bit). The Port A output buffers have

symmetrical drive characteristics with both high sink and source capability.


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When pins PA0 to PA7 are used as inputs and are externally pulled low, they

will source current if the internal pull-up resistors are activated. The Port A pins

are tri-stated when a reset condition becomes active, even if the clock is not

running.

Port B (PB7..PB0)

Port B is an 8-bit bi-directional I/O port with internal pull-up resistors

(selected for each bit). The Port B output buffers have symmetrical drive

characteristics with both high sink and source capability. As inputs, Port B pins

that are externally pulled low will source current if the pull-up resistors are

activated. The Port B pins are tri-stated when a reset condition becomes active,

even if the clock is not running. Port B also serves the functions of various

special features of the Atmega16 as listed on table below.

Port C (PC7..PC0)

Port C is an 8-bit bi-directional I/O port with internal pull-up resistors

(selected for each bit). The Port C output buffers have symmetrical drive

characteristics with both high sink and source capability. As inputs, Port C pins


activated. The Port C pins are tri-stated when a reset condition becomes active,

even if the clock is not running. If the JTAG interface is enabled, the pull-up

resistors on pins PC5(TDI), PC3(TMS) and PC2(TCK) will be activated even if

a reset occurs. Port C also serves the functions of the JTAG interface and other



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Port D (PD7..PD0)

Port D is an 8-bit bi-directional I/O port with internal pull-up resistors

(selected for each bit). The Port D output buffers have symmetrical drive

characteristics with both high sink and source capability. As inputs, Port D pins


activated. The Port D pins are tri-stated when a reset condition becomes active,

even if the clock is not running. Port D also serves the functions of various


RESET

Reset Input. A low level on this pin for longer than the minimum pulse

length will generate a reset, even if the clock is not running. Shorter pulses are

not guaranteed to generate a reset.

XTAL1

Input to the inverting Oscillator amplifier and input to the internal clockoperating circuit.

XTAL2

Output from the inverting Oscillator amplifier.

AVCC

AVCC is the supply voltage pin for Port A and the ADC. It should be

externally connected to VCC, even if the ADC is not used. If the ADC is used, it

should be connected to VCC through a low-pass filter.


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AREF

AREF is the analog reference pin for the ADC. [10]

2.6 Power Saving Modes

Idle Mode stops the CPU while allowing the USART, Two-wire interface,SRAM (Static Random Access Memory), Timer/Counters, SPI port, and

interrupt system to continue functioning.

Power-Down Mode saves the register contents but freezes the Oscillator,disabling all other chip functions until the next external interrupt or

Hardware Reset.

Power-Save Mode in which the Asynchronous Timer continues to run,allowing to maintain a timer base while the rest of the device is sleeping.

ADC Noise Reduction Mode stops the CPU and all I/O modules exceptAsynchronous Timer, to minimize switching noise during A/D

conversions.

Standby Mode in which the crystal/resonator Oscillator is running whilethe rest of the device is sleeping. This allows very fast start-up combined

with low-power consumption.

Extended Standby Mode in which both the main Oscillator and theAsynchronous Timer continue to run.[9]

2.7 Writing the Control Program

When its time to write the program that controls the project, the options

include using machine code, assembly language, or a higher-level language.


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2.7.1 Machine code

The most fundamental program form is machine code, the binary

instructions that cause the CPU to perform the desired operations.

Machine code or machine language is a system of instructions and data executed

directly by a computers central processing unit. Machine code may be regarded

as a primitive (and cumbersome) programming language or as the lowest-level

representation of a compiled and/or assembled computer program. Programs in

interpreted languages are not represented by machine code, however, their

interpreter (which may be seen as a processor executing the higher level

program) often is. Machine code is sometimes called native code when referring

to platform-dependent parts of language features or libraries. Machine code

should not be confused with so called byte code, which is executed by an

interpreter.

Every processor or processor family has its own machine code instruction

set. Instructions are patterns of bits that by physical design correspond to

different commands to the machine. The instruction set is thus specific to a class

of processors using (much) the same architecture.

2.7.2 Assembly language

One step removed from machine code is assembly language, where

abbreviations called mnemonics (memory aids) substitute for the machine codes.

The mnemonics are easier to remember than the machine codes they stand for.

For example, in the 8052s assembly language, the mnemonic CLR C means

clear the carry bit, and is easier to remember than its binary code (11000011).

Since machine code is ultimately the only language that a CPU understands, you

need some way of translating assembly-language programs into machine code.

For very short programs, you can hand assemble, or translate the mnemonics


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yourself by looking up the machine codes for each abbreviation. Another option

is to use an assembler, which is software that

runs on a desktop computer and translates the mnemonics into machine code.

Most assemblers provide other features, such as formatting the program code and

creating a listing that shows both the machine-code and assembly-language

versions of a program sideby-side.

2.7.3 Higher-level languages (H-L-L)

A programming language such as C, FORTRAN, or Pascal that enables aprogrammer to write programs that are more or less independent of a particular

type of computer. Such languages are considered high-level because they are

closer to human languages and further from machine languages. In contrast,

assembly languages are considered low-level because they are very close to

machine languages. The main advantage of high-level languages over low-level

languages is that they are easier to read, write, and maintain. Ultimately,

programs written in a high-level language must be translated into machine

language by a compiler or interpreter. The first high-level programming

languages were designed in the 1950s. Now there are dozens of different

languages, including Ada, Algol, BASIC, COBOL, C, C++, FORTRAN, LISP,

Pascal, and Prolog. Higher-level languages also simplify programming by

allowing you to do in one or a few lines what would require many lines of

assembly code to accomplish. Interpreters and compilers are two forms of

higher-level languages. An interpreter translates a program into machine code

each time the program runs, while a compiler translates only once, creating a

new, executable file that the computer runs directly, without re-translating. As a

rule, interpreters are very convenient for shorter programs where execution speed


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isnt critical. With an interpreted language, you can run your program code

immediately after writing it, without a separate compile or assembly step. A

compiler is a good choice when a program is long or has to execute quickly. A

single language like BASIC may be available in both interpreted and compiled

versions. [4]

2.7.3.1 BASCOM-AVR

BASCOM-AVR is a type of high level languages is four programs in one

package, it is known as an IDE (Integrated Development Environment) it

includes the program editor, the compiler, the programmer and the simulator all

together.

BASCOM-AVR is a compiler that uses a version of Basic very similar to

QBASIC to produce programs for the AVR. BASCOM-AVR uses IDE which

allows writing and editing programs, compiling them, testing them with a

simulator and finally writing the program to the microcontroller for use in a

circuit all from one program.

Microcontrollers, such as the AVR, are controlled by software and they do

nothing until they have a program inside them. The AVR programs are written

on a PC (Personal Computer) using the BASCOM-AVR. This software is a type

of computer program called compiler.[8]

- Programming template

------------------------------------------------------------------

1. Title Block

Author:

Date:


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File Name:

------------------------------------------------------------------

2. Program Description:

------------------------------------------------------------------

3. Compiler Directives (these tell Bascom things about our hardware)

$regfile = attiny26.datthe micro we are using

$crystal = 1000000 the speed of the micro

------------------------------------------------------------------

4. Hardware Setups

setup direction of all ports

Config Porta = Output LEDs on portA

Config Portb =Input switches on portB

5. Hardware AliasesLed0 alias portb.0 6. 22nitialize ports so hardware starts correctly

Porta = &B11111111 turns off LEDs

------------------------------------------------------------------

7. Declare Variables

8. Initialise Variables

9. Declare Constants

------------------------------------------------------------------

10. Program starts hereDo

Loop

End end program


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CHAPTER THREE

ARCHITECTURE OF THE LINE FOLLOWER

This chapter consist the design of the line follower, the car which used is a

simple toy car that modified by taking out the most of it is component and just

leave the main body which contains two dc motors, one in the front (for the front

wheels) and the other one (for the rear wheels). This body is the basic

construction that the circuit built on it.

First of all the circuit built on a breadboard so as known, in electronics

some experimentation is required to prototype (trial) specific circuits. A

prototype circuit is needed before a PCB is designed for the final circuit. A

breadboard is used to prototype the circuit. It has holes which components can be

inserted and has electrical connections between the holes as per the figure 3.1

below shows that. Using a breadboard means no soldering and a circuit can be

constructed quickly and modified easily before a final solution is decided upon.

Figure 3.1 breadboard


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3.1 Motor Driver (L293D)

One of the first realizations in robotics is that making something move

isnt an easy task. Simply cant take a brain circuit and connect it to a motor

and expect anything to happen. The motor will simply not working at the puny

output signal from the brains, and stay stationary. What the brain needs is an

enforcer (Muscle). Something to convince the motor to do things the way the

brains want it to be done. There are many ways to strengthen (buffer) a signal so

its strong enough to drive a large load like a motor. Transistors H-bridges

circuit, buffer chips, and dedicated motor driving chips are all suitable choices.

A motor driver is a device or group of devices that serves to govern in

some predetermined manner the performance of an electric motor. A motor

driver include automatic means for starting and stopping the motor, selecting

forward or reverse rotation, selecting and regulating the speed, regulating or

limiting the torque, and protecting against overloads and faults.

3.1.1 (L293D) Description

This device is a monolithic integrated high voltage, high current four

channel driver. Drive inductive loads (such as relays solenoids, DC and stepping

motors and switching power transistors). To simplify use as two bridges each

pair of channels is equipped with an enable input. A separate supply input is

provided for the logic, allowing operation at a lower voltage and internal clamp

diodes are included. This device is suitable for use in switching applications at

frequencies up to 5 kHz. The L293D is assembled in a 16 lead plastic package

which has 4 center pins connected together and used for heat sinking.

L293D is dual H-Bridge motor drive, so with one IC can interface two DC

motors which can be controlled in both clockwise and counter clockwise

direction. L293D has output current of 600Ma and peak output current of 1.2A
http://en.wikipedia.org/wiki/Electric_motorhttp://en.wikipedia.org/wiki/Fault_(power_engineering)http://en.wikipedia.org/wiki/Fault_(power_engineering)http://en.wikipedia.org/wiki/Electric_motor


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per channel. Moreover for protection of circuit from back EMF output diods are

included within the IC. The output supply has a wide range from 4.5V to 36V,

which has made L293D a best choice for DC motor driver.

3.1.2 Working theory of H-Bridge

The name H-Bridge is derived from the actual shape of the switching

circuit which controls the motion of the motor. It is also known as (Full Bridge).

Basically there are four switching elements in the H-Bridge as shown in figure

3.2 below.

Figure 3.2 H-Bridge circuit

As seen in the figure 3.2 above there are four switching elements named as

High side left, High side right, Low side right, Low side left. When

these switches are turned on in pairs motor changes its direction accordingly.

Like, if we switch on High side left and Low side right then motor rotate in

forward direction, as current flows from (+) power supply through the motor coil

goes to ground via switch low side right. Similarly, when you switch on low side

left and high side right, the current flows in opposite direction and motor rotates


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in backward direction. This is the basic working of H-Bridge. So we have seen

that using simple switching elements we can make our own HBridge, or other

option we have is using an IC based Hbridge driver. [7]

3.1.3 Pin configurations

Figure 3.3 and table 3.1 below shows the pin configuration of L239D.

Figure 3.3 pin configurations of (L293D)


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Table 3.1 pin configuration of L293DNameFunctionPin Number

Enable 1,2Enable pin for Motor 1; active highInput 1Input 1 for Motor 12

Output 1Output 1 for Motor 13GroundGround (0V)4GroundGround (0V)5Output 2Output 2 for Motor 16Input 2Input 2 for Motor 17Vcc 2

Supply voltage for Motors; 9-12V (up

to 36V)8Enable 3,4Enable pin for Motor 2; active high9

Input 3Input 1 for Motor 11Output 3Output 1 for Motor 1GroundGround (0V)2GroundGround (0V)3Output 4Output 2 for Motor 14Input 4Input 2 for Motor 15Vcc 1Supply voltage; 5V (up to 36V)6


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3.2 Sensors

A sensor is often defined as a device that receives and responds to a signal

or stimulus. This definition is broad. In fact, it is so broad that it covers almost

everything from a human eye to a trigger in a pistol. Sensors that are used in

artificial systems must speak the same language as the devices with which they

are interfaced. This language is electrical in its nature. Thus, it should be

possible to connect a sensor to an electronic system through electrical wires.

Hence, we use a somewhat narrower definition of sensors, which may be phrased

as: A sensor is a device that receives a stimulus and responds with an electrical

signal. The stimulus is the quantity, property, or condition that is sensed and

converted into electrical signal.

The purpose of a sensor is to respond to some kind of an input physical

property (stimulus) and to convert it into an electrical signal which is compatible

with electronic circuits. The sensors considered as a translator of a generally

nonelectrical value into an electrical value. The sensors output signal may be in

the form of voltage, current, or charge. These may be further described in terms

of amplitude, frequency, phase, or digital code. This set of characteristics is

called the output signal format. Therefore, a sensor has input properties (of any

kind) and electrical output properties.

3.2.1 IR LEDs

A light-emitting diode (LED) is a semiconductor diode that emits incoheren

narrow-spectrum light when electrically biased in the forward direction of the p-junction. The basic function of the emitter is to convert electricity into light. It work

on the principle of recombination of the electron-hole pair. As in the conduction ban

of a diode, electrons are the majority carrier and in the valence band, holes ar

majority carrier. So when an electron from a conduction band recombines with a hol


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of valance band, some amount of energy is released and this energy is in the form o

light. The amount of energy released is depends upon the forbidden energy gap. Th

color of the emitted light depends on the composition and condition of th

semiconducting material used, and can be infrared (IR LED), visible, or near

ultraviolet. LEDs are often used as small indicator lights on electronic devices and

increasingly in higher power applications such as flashlights and area lighting. The IR

Led has two legs, the leg which is longer is positive and other leg is negative as see

in figure 3.4 below.

Figure 3.4 IR LED (Tx)

3.2.2 Photodiodes

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

direction. The basic function of the detector is to convert light into electricity. As

its name implies that it works effectively only when the certain number of

photon or certain amount of light falls on it. When there is no fall of light on the

photodiode it has an infinite resistance and act as an open switch but as the light

starts falling on the photodiode, the resistance becomes low and when the full

intensity of light fall on the photodiode then its resistance becomes zero and it

starts act like a closed switch. The IR receiver shows in figure 3.5 below: [6]


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Figure 3.5 photodiode (Rx)

3.2.3 Circuit diagram of IR sensors

The circuit diagram is shown below in Figure 3.6 and only one set of

emitter/detector sensor is depicted. The remaining two are constructed in the

same manner.

Figure 3.6 circuit diagram of IR sensor

A line sensor in its simplest form is a sensor capable of detecting a

contrast between adjacent surfaces, such as difference in color. The theory of

operation is simple when light shines on a white surface; most of the incoming

light is reflected away from the surface. In contrast, most of the incoming light is


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absorbed if the surface is black. Therefore, by shining light on a surface and

having a sensor to detect the amount of light that is reflected, a contrast between

black and white surfaces can be detected. Figure 3.7 shows an illustration of the

basics just covered.

Figure 3.7 the basic IR function

By making use the reflecting light from the black and white surfaces, the

objective of tracking a black line is simple and can be achieved by using the

appropriate sensors. The sensors array consists of two IR transmitters (Tx) and

receivers (Rx) pasted on the front of the car as shown in figure 3.8 below:

Figure 3.8 the sensors positions


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3.3 Interfacing the Components with Microcontroller

The components can be connected with microcontroller directly or

through a certain devices.

3.3.1 IR sensor interface with the microcontroller

The IR sensors array consist of: two LDEs (Tx) and two photo diodes

(Rx), the positive legs of the LEDs are connected to the source through (2K)

resistance to reduce the input voltage, and the negative legs are connected to the

ground. By this way the LEDs emitting infrared rays. The photo diodes also

having two legs, the positive legs are grounded and the negative legs are

connected with the microcontroller to pins (A0, A1).

3.3.2 Motor interface with the microcontroller

The microcontroller sends a signal to L239D that acts as a switch. If the

signal received by the L239D is high it will rotate the motor or else it wont do

so. Note that microcontroller only sends a signal to a switch which gives the

voltage required by the motor to rotate. Here using L293D which can be used tocontrol two motors. Pin connections for L239D shown below:

En1 & En2 are given logic 1 from microcontroller or give 5V from outsideand are used to activate/deactivate one half of the H-bridge.

V is the voltage supply to the motor(s). Vcc is the logic 1 or 5V. GND

There are two DC motors front motor for front wheels and rear motor for

rear wheels. The motors receive a signal from the microcontroller through the

motor driver. The dc motors rotation depends on the polarity or the current


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direction, thats why the motor driver is used. It has four available inputs and

outputs, only two outputs are needed for each motor. The inputs of L239D are

connected to the microcontroller ports (D1, D2, D3), D1 and D2 are connected to

(PIN1, PIN2) respectively to drive the front motor bidirectional, D3 connected

to(PIN4) to drive the rear motor. When the microcontroller sends a signal to the

motor driver, this signal actually enables one of the outputs of the motor driver,

so L293D allows the motor to rotate in the desired direction. The rear motor only

goes forward tracing the line, so it doesnt need to run bidirectional and that is

the reason of not connecting PIN5 with the microcontroller. The L293D-DC-

motor-Interface can be represented in figure 3.9 below bellow:

Figure 3.9 L293D and DC-motors interfacing


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Table 3.2 Truth table of L293D

IN1 IN2 Description

1 1 Motor stops or breaks

0 1 Motor runs anti-clock wise

1 0 Motor runs clockwise

1 1 Motor stops or breaks

For the above truth table, the enable (EN) has to be set (1).


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CHAPTER FOUR

DESIGN AND PROGRAMMING OF THE LINE

FOLLOWER

4.1 Circuit Connection

According to the main function of the line follower, which is to detect the

path that specified by the user, two pair of IR transmitters and receivers has

been connected to the terminals, transmitters connected to the power supply and

the receivers connected to microcontroller(portA.0, portA.1) in order to sendsignal to the microcontroller, with this signal the car can define which case that it

goes through, then it gives the suitable output for the motors through the L293D

that takes the car back to the black line. The model can be represented in figure

4.1 below. As it is clear, the microcontroller is the main object that the whole

components of the circuit are connected to. The devices can be divided into two

groups, first; the inputs of the Atmega16 microcontroller which are; the IRs

transmitter and receivers, only the receivers are connected directly to the pins of

the microcontroller, and the two other Irs transmitters are supplied from the

power supply (+ 5v). The other group is the output devices; they are; the front

motor, the rear motor, multi colors LEDs (Light Emitting Diodes), motor driver

(L293D).


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Figure 4.1 the circuit diagram


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4.2 The Principle of Operation of the Line Follower

The principle of operation of the follower is to send and receive signals

from the right and left IR receivers which are located in the center of the car

model, and send another signal to the microcontroller to take an action according

to the input. The car should be put where the path (black line) is exactly above

the right and the left IR receivers.

While the microcontroller pins receives a specific signal from which is fed

from both receivers Port A as (ADC) value of(+ 2.5v) that means the car should

go forward, that happens when the black line is right under the IR receivers, the

rear motor will receive (+ 5v) through the motor driver L293D, whenever one of

the two IR receivers got out of the path to a plain surface (a white surface was

taken in consideration), it directly sends a signal to the microcontroller reporting

that the car got out of the desired path. So the front motor will rotate in the

direction of the line in order to take the car back to its path.

LEDs are used only to clarify the movement of the car, the two yellow

front LEDs are showing that the car is in the right path, when the power is

connected to the car, they flash ten times showing that the car is in the standby

mode. There is a LED with a red color that lights when the car got out of the

desired path which is already specified. Also there are two other LEDs; a right

LED flashes when the front wheel rotates to the right direction, and another left

LED also flashes when it goes to the left direction.


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4.3 Programming of the Microcontroller

The program has been written by BASCOM-AVR programming language,

its one of the simplest and easiest high-level programming languages that deal

with Atmel-AVR microcontrollers, once it is a high-level language, the

instructions of the program shows the logical statements that the car should

physically execute according to the cases that the car might face in its way going

forward. The following flowchart in figure 4.2 below clarifies the main idea of

the program.


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Start

FLASH THE TWO YELLOW LEDs

TEN TIMES (STANDBY MODE)

BOHT R. IR &

L. IR INSIDE

THE LINE?

RUN THE REAR MOTOR

AND THE TWO YELLOW

LEDs

YES

R. IR DETECTS

LINE & L. IR OUT

OF LINE?

NO

YES

ROTATE FRONT MOTOR TO THE RIGHT &

RUN REAR MOTOR + RIGHT BLUE LED

NO

1

2

2

2


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Figure 4.2 Flowchart of the possible cases

BOHT R. IR & L.

IR OUTSIDE

THE PATH

STOP ALL MOTORS AND

LIGHT RED LED

NO

2

L. IR DETECTS

LINE & R. IR

OUT OF LINE?

ROTATE FRONT MOTOR TOTHE LEFT & RUN REAR

MOTOR + LEFT BLUE LED

NO

2

2

YES

YES

1


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4.3.1 The cases might face the follower

There are four cases that the car might face on its way; all of them should

be completely defined in order to make the microcontroller able to deal with

them. The first case is when the car is completely out of the path (the black line),at this case both of the IR transmitters is out of the path. The second case is when

the car is inside the desired path, which means both of the IR transmitters are

detecting the black line. The third when the car turns right of the line, leaving the

path in its left, then only the left IR transmitter detects the black line, while the

other detects the color of the surface (white surface). The fourth and the last case

is, when the car turns left of the line, leaving the line in its right, at this case the

right IR transmitter detects the black line, while the other detects the (white)

surface.

To be able to understand the conditions that the car may go through, it is

essential to define the ports of the microcontroller; table 4.1 below identifies

each port interface and when it should give an output signal:


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Table 4.1 Ports connections

Port I/O connected to Runs when Period

Portd.1 O/P L293(IN 1) Power is on always



Portc.0 O/P Red LED The car got out of path -

Portb.0 O/P Left led The wheel turn left -

Portb.1 O/P Right led The wheel turn right -

Portb.2 O/PForward yellow right

LEDAt standby mode 30 msec

Portb.3 O/PForward yellow left

LEDAt standby mode 30 msec

Porta.1 I/P Right IR detectorAlways to detect the

path-

Porta.0 I/P Left IR detector

Always to detect the

path -


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4.3.2 The explanation of the code

The code starts with defining the micro type ($regfile =M16DEF.DAT)

which means Atmega16, and specify the frequency used ($crystal = 10000000),

then defining the ports as follows:

Ports (D0, D1, D2, and D2) defined as an output ports thatconnected to L293D to control the motors.

Port C0 defined as an output port that connected to the red led. Ports (B0, B1, B2, and B3) defined as an output ports connected to

LEDs also.

Part (a) of the code shows that after defining the ports, a variable has been

reserved in the micro memory to detect a loop in which the forward yellow

LEDs flashes for 10 times (ON for 30ms and OFF for 30ms) when the power

ON, as the detectors shows that the car is in the standby mode. Next step a port

A is configured as an ADC to receive the analog signal from the IR receivers.

$regfile=M16DEF.DAT$crystal= 10000000ConfigPortd.0 =OutputConfigPortd.1 =OutputConfigPortd.2 =OutputConfigPortd.3 =OutputConfigPortc.0 =OutputConfigPortb.0 =OutputConfigPortb.1 =OutputConfigPortb.2 =Output

ConfigPortb.3 =OutputDim Y AsByteFor Y = 1 To 10Portb.2 = 1Portb.3 = 1Waitms 30Portb.2 = 0


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Portb.3 = 0Waitms 30NextConfigAdc=Single, Prescaler = 8 , Reference =InternalEnableInterruptsStart

AdcPart (a) of the code

The next part started with holding a word in the memory for two variables;

Right1 and Left1, the first variable refers port A1, and the second refers to port

A0, which are the right and the left IR transmitter connected to the ports

mentioned respectively. The while-loop shows that when both right and left IR

detectors at the same time detect less than 300 (ADC value) or about (+ 2.5v),then the microcontroller will give a signal (+ 5v) to the red LED that is

connected to port C0. In other words, when the car is completely out of path,

only the red LED will light up.

Dim Left1 AsWordDim Right1 AsWordDim A AsByte

M:DoLeft1 =Getadc(0)Right1 =Getadc(1)While Right1 < 300 And Left1 < 300Left1 =Getadc(0)Right1 =Getadc(1)Portc.0 = 1Portb.2 = 0Portb.3 = 0Portd.0 = 0Portd.1 = 0Portd.2 = 0Portd.3 = 0Waitms 300WendPortc.0 = 0


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Part (b)

Part ( c) is an If condition used to represent that when the left Rx read

less than 400(digitally) then the program jump to loop defined as L, and if the

right Rx read less than 400(digitally) then the program jump to loop defined asR. In case the conditions an above are not confirmed the port B2=1and port

B3=1 which are connected to the forward yellow LEDs and a port D1=1, which

connected to (input1) of the L293driver meaning that the rear motor is running,

and all other ports are 0. To control the speed of the rear motor for the specific

design, the micro sends signal (1) for 5ms and stop (0) for16ms.

IfLeft1 < 400 ThenGosub LEndIfIfRight1 < 400 ThenGosub REndIfPortb.2 = 1Portb.3 = 1Portd.0 = 0Portd.1 = 1

Portd.2 = 0Portd.3 = 0Waitms 5Portd.0 = 0Portd.1 = 0Portd.2 = 0Portd.3 = 0Waitms 16Loop

End

Part (c)

In part (d) the loop L and R which mentioned in previous conditions are

defined, in loop L port B0=1 which mean the left led flashes, port D1=1 and port


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D3=1 to enable the L293D to rotate the forward motor to the right because the

left receiver is out of path and need to rotate right to be in the path. For the loop

R port B1=1 meaning that the right led flashes, port D (1 and 2) equal 1to

enable the L293D to rotate the front motor to the left because the right receiver

is out of the path and need to rotate left to stay on the track. In both loop L and

R the rear motor runs for 5ms and stops for 16ms to drive the rear motor by

specific speed.

L:For A = 1 To 3Portb.0 = 1Portd.0 = 0

Portd.1 = 1Portd.2 = 0Portd.3 = 1Waitms 5

Portb.0 = 0Portd.0 = 0Portd.1 = 0Portd.2 = 0Portd.3 = 1

Waitms 16NextGosub MR:

For A = 1 To 3Portb.1 = 1Portd.0 = 0Portd.1 = 1

Portd.2 = 0Portd.3 = 1Waitms 16NextGosub MR:For A = 1 To 3


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Portb.1 = 1Portd.0 = 0Portd.1 = 1Portd.2 = 1Portd.3 = 0Waitms

5Portb.1 = 0Portd.0 = 0Portd.1 = 0Portd.2 = 1Portd.3 = 0Waitms 16

NextGosub M

Part (d)

4.3.3 The logical statements explanations of the code

The program starts with the standby mode, the forward yellow LEDs

should flash ten times by the time the power is on, as the detectors show that the

car is in the standby mode, and it is ready to receive signals from the IR

detectors. The number of the port of the LEDs has been referred to, previously inthe table 4.1.

The next loop started with holding a word in the memory for two

variables; Right1 and Left1, the first variable refers to the ADC port no. 1, and

the second refers to the ADC port no. 0, which are the right and the left IR

transmitter connected to the ports mentioned respectively. The while-loop shows

that when both right and left IR detectors at the same time detect less than 300

(ADC value) or about (+ 2.5v), then the microcontroller will give a signal (+ 5v)

to the red LED that is connected to Portc.0. In other words, when the car is

completely out of path, only the red LED will light up.


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Else if the car got out of the path to the right, in case that the path is

curved to the left of the car, then the right IR transmitter will send an ADC value

more than 300 (more than + 2.5v) to the Porta.0, by the time the other left IR still

in the path with an ADC value of more than 300, then the microcontroller will

send a signal to the L293D to enable the output1 and output2 that control the

front motor in order to rotate the wheels of the car to the left, taking the car back

to the path that is in the left. Another two signals will be sent, one to the L293D

for enabling the rear motor while the car is turning left back to the path, and

other is sent to the left blue LED to flash while the car turning left.

When the car got out of the path, but this time to the left in case that the

black live is curved to the right, then the left IR transmitter will send an ADC

value more than 300 to the Port1.1 of the microcontroller, by the time that the

right IR still located in the right path, then the microcontroller will send three

signals, one to the L293D to enable the output3 and output4 which control the

rear motor in order to rotate the wheel of the car to the right,. The second signal

will also be sent to the L293D to run the rear motor to go forward, and the other

signal is for flashing the blue right LED. The last case, when the car is

completely inside of the path (the black line), then, both of the IR transmitters

will detect the line, and send this signal to the microcontroller, then, only the rear

motor will be active by enabling the its two outputs of the L293D. And the two

forward yellow LEDs will light as long as the car is in the right way.


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CAPTER FIVE

5.1 Conclusion

A follower scheme has been done which mean that this van can runforward, turn right and turn left.

(l293D) represents an interface unit with a microcontroller tocontrol the movements of the two motors.

BASCOM-AVR compiler is an easy language compared with theother high level language.

5.2 Recommendations

Smart versions of followers can be used in many lifeapplications. Obstacle detectors can be add so that follower to

stop when something crossover its way.

The follower can be modifying to avoid things that might faceit and return to right path.

Embedded magnets path can be used instead of drown line onthe surface, when its supplied with magnetic detectors, the

follower follows the magnets path.

The code can be modified and array of sensors can be increasedto satisfy a specific cases(sensitivity) and when the follower

totally gets out of the right path the control program command

the to reverse its movement to return to the course.


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References

[1]- Dhananjay V.Gadre, Programming and customizing the AVRmicrocontroller McGraw-Hill 2001.

[2]- Steven F.Barrett, Daniel J.Pack, Atmel AVR microcontroller

primer Programming and Interfacing, Morgan & Claypool 2008.

[3]-Muhammad Ali Mazidi, Sarmad Naimi, Sepeher Naimi, The

AVR microcontroller and embedded system using assembly and C,

Prentice hall.

[4]-Jan Axelson, The microcontroller idea book, Lakeview

Research 1997.

[5]- Priyank Patill, , K.J.Somaiya,Line following robot, Mumbai

India.

[6]- Jacob Fraden, Hand book of modern sensors (third edition),

San Diego California

[7]-Krishna Nand Gupta and others, Motor driver L293D.

[8]-Programming in BASCOM-AVR, David Swinscoe

www.davidswinscoe.com

[9]-http://www.atmel.com/products/avr/ , may 2011

[10]- ATmega16 data sheet,Atmel Corporation 2003.


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Appendices

The control program

$regfile="M16DEF.DAT"$crystal= 10000000ConfigPortd.0 =OutputConfigPortd.1 =OutputConfigPortd.2 =OutputConfigPortd.3 =OutputConfigPortc.0 =OutputConfigPortb.0 =OutputConfigPortb.1 =Output

ConfigPortb.2 =OutputConfigPortb.3 =OutputDim Y AsByteFor Y = 1 To 10Portb.2 = 1Portb.3 = 1Waitms 30Portb.2 = 0Portb.3 = 0

Waitms 30NextConfigAdc=Single, Prescaler = 8 , Reference =InternalEnableInterruptsStartAdc

Dim Left1 AsWordDim Right1 AsWordDim A AsByteM:

DoLeft1 =Getadc(0)Right1 =Getadc(1)While Right1 < 300 And Left1 < 300Left1 =Getadc(0)Right1 =Getadc(1)Portc.0 = 1


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Portb.2 = 0Portb.3 = 0Portd.0 = 0Portd.1 = 0Portd.2 = 0

Portd.3 = 0Waitms 300WendPortc.0 = 0

IfLeft1 < 400 ThenGosub LEndIfIfRight1 < 400 ThenGosub R

EndIfPortb.2 = 1Portb.3 = 1Portd.0 = 0Portd.1 = 1Portd.2 = 0Portd.3 = 0Waitms 5Portd.0 = 0Portd.1 = 0

Portd.2 = 0Portd.3 = 0Waitms 16LoopEnd

L:For A = 1 To 3Portb.0 = 1Portd.0 = 0

Portd.1 = 1Portd.2 = 0Portd.3 = 1Waitms 5

Portb.0 = 0Portd.0 = 0


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Portd.1 = 0Portd.2 = 0Portd.3 = 1Waitms 16NextGosub

MR:

For A = 1 To 3Portb.1 = 1Portd.0 = 0Portd.1 = 1

Portd.2 = 0Portd.3 = 1Waitms 16

NextGosub MR:For A = 1 To 3Portb.1 = 1Portd.0 = 0Portd.1 = 1Portd.2 = 1Portd.3 = 0

Waitms 5Portb.1 = 0Portd.0 = 0Portd.1 = 0Portd.2 = 1Portd.3 = 0Waitms 16

NextGosub M


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The line following van final design :

line follower robot is a mobile machine that can detect and follow line which is drawn on the floor

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