CHAPTER 1

INTRODUCTION

1.1 INTRODUCTION TO LINE FOLLING ROBOT

A line follower robot is basically a robot designed to follow a ‘line’ or path already

predetermined by the user. This line or path may be as simple as a physical white line on

the floor or as complex path marking schemes e.g. embedded lines, magnetic markers and

laser guide markers. In order to detect these specific markers or ‘lines’, various sensing

schemes can be employed. These schemes may vary from simple low cost line sensing

circuit to expansive vision systems. The choice of these schemes would be dependent

upon the sensing accuracy and flexibility required. From the industrial point of view, line

following robot has been implemented in semi to fully autonomous plants. In this

environment, these robots functions as materials carrier to deliver products from one

manufacturing point to another where rail, conveyor and gantry solutions are not

possible. Apart from line following capabilities, these robots should also have the

capability to navigate junctions and decide on which junction to turn and which junction

ignore. This would require the robot to have 90 degree turn and also junction counting

capabilities. To add on to the complexity of the problem, sensor positioning also plays a

role in optimizing the robots performance for the tasks mentioned earlier.

Line-following robots with pick- and- placement capabilities are commonly used in

manufacturing plants. These move on a specified path to pick the components from

specified locations and place them on desired locations. Basically, a line-following robot

is a self-operating robot that detects and follows a line drawn on the floor. The path to be

taken is indicated by a white line on a black surface. The control system used must sense

the line and man oeuvre the robot to stay on course while constantly correcting the wrong

moves using feedback mechanism, thus forming a simple yet effective closed- loop

system.

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ADVANTAGES

• Robot movement is automatic.

• Fit and Forget system.

• Used for long distance applications.

• Defense applications.

• Used in home, industrial automation.

• Cost effective.

• Simplicity of building.

DISADVANTAGES

• Line following robot follows a black line about 1 or 2 inches in width on a white

surface.

• Line tracing robots are simple robots with an additional sensors placed on them.

• It always needs a path to run either white or black since the IR rays should reflect

from the particular path.

• Slow speed and instability on different line thickness or hard angles.

APPLICATIONS:

• Guidance system for industrial robots moving on shop floor etc.

• Industrial applications.

• Home applications.

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Crystal

Reset circuit

Photo Sensor Array

Photo Sensor Array

H-Bridge

Left Motor

Left Motor

Right MotorRight Motor

AT89S52 Microcontroller

Power Supply Unit Power Supply Unit

1.2 BLOCK DIAGRAM:

Fig.1.2 Block diagram of line follower

3

12 V Lead Acid Battery

To all sections

1.3 INTRODUCTION TO EMBEDDED SYSTEMS

An embedded system is a system which is going to do a predefined specified task is the

embedded system and is even defined as combination of both software and hardware. A

general-purpose definition of embedded systems is that they are devices used to control,

monitor or assist the operation of equipment, machinery or plant. "Embedded" reflects

the fact that they are an integral part of the system. At the other extreme a general-

purpose computer may be used to control the operation of a large complex processing

plant, and its presence will be obvious.

All embedded systems are including computers or microprocessors. Some of these

computers are however very simple systems as compared with a personal computer.

The simplest devices consist of a single microprocessor (often called a "chip”), which

may itself be packaged with other chips in a hybrid system or Application Specific

Integrated Circuit (ASIC). Its input comes from a detector or sensor and its output goes to

a switch or activator which (for example) may start or stop the operation of a machine or,

by operating a valve, may control the flow of fuel to an engine.

As the embedded system is the combination of both software and hardware

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Embedded System

Software Hardware

ALP

C

VB Etc.,

Processor

Peripherals

memory

Figure:1.3 Block diagram of Embedded System

Software deals with the languages like ALP, C, and VB etc., and Hardware deals with

Processors, Peripherals, and Memory.

Memory: It is used to store data or address.

Peripherals: These are the external devices connected

Processor: It is an IC which is used to perform some task

Applications of embedded systems

Manufacturing and process control

Construction industry

Transport

Buildings and premises

Domestic service

Communications

Office systems and mobile equipment

Banking, finance and commercial

Medical diagnostics, monitoring and life support

Testing, monitoring and diagnostic systems

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CHAPTER:2

HARDWARE EXPLANATION

2.1 BASIC HARDWARE

2.1.1 BLOCK DIAGRAM FOR REGULATED POWER SUPPLY

(RPS):

Fig:2.1 Power Supply

2.1.2 DESCRIPTION OF TRANSFORMER

A transformer is a device that transfers electrical energy from one circuit to another

through inductively coupled conductors—the transformer's coils. A varying current in the

first or primary winding creates a varying magnetic flux in the transformer's core, and

thus a varying magnetic field through the secondary winding. This varying magnetic field

induces a varying electromotive force (EMF) or "voltage" in the secondary winding. This

effect is called mutual induction.

2.1.2.1 Basic Principle

A transformer makes use of Faraday's law and the ferromagnetic properties of an iron

core to efficiently raise or lower AC voltages. It of course cannot increase power so that

if the voltage is raised, the current is proportionally lowered and vice versa.

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2.1.2.2Working

A transformer consists of two coils (often called 'windings') linked by an iron core, as

shown in figure below. There is no electrical connection between the coils; instead they

are linked by a magnetic field created in the core.

Fig:2.2.2 Basic Transformer

Transformers are used to convert electricity from one voltage to another with minimal

loss of power. They only work with AC (alternating current) because they require a

changing magnetic field to be created in their core. Transformers can increase voltage

(step-up) as well as reduce voltage (step-down).

Alternating current flowing in the primary (input) coil creates a continually changing

magnetic field in the iron core. This field also passes through the secondary (output) coil

and the changing strength of the magnetic field induces an alternating voltage in the

secondary coil. If the secondary coil is connected to a load the induced voltage will make

an induced current flow. The correct term for the induced voltage is 'induced

electromotive force' which is usually abbreviated to induced e.m.f.

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The iron core is laminated to prevent 'eddy currents' flowing in the core. These are

currents produced by the alternating magnetic field inducing a small voltage in the core,

just like that induced in the secondary coil. Eddy currents waste power by needlessly

heating up the core but they are reduced to a negligible amount by laminating the iron

because this increases the electrical resistance of the core without affecting its magnetic

properties. Transformers have two great advantages over other methods of changing

voltage:

1. They provide total electrical isolation between the input and output, so they can

be safely used to reduce the high voltage of the mains supply.

2. Almost no power is wasted in a transformer. They have a high efficiency (power

out / power in) of 95% or more.

2.1.2.3 Classification of Transformer

Step-Up Transformer

Step-Down Transformer

2.1.3 Rectifier

The purpose of a rectifier is to convert an AC waveform into a DC waveform

(OR) Rectifier converts AC current or voltages into DC current or voltage.  There are two

different rectification circuits, known as 'half-wave' and 'full-wave' rectifiers.  Both use

components called diodes to convert AC into DC.

2.1.3.1 The Half-wave Rectifier

The half-wave rectifier is the simplest type of rectifier since it only uses one diode, as

shown in figure.

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Fig:2.3.1(a) Half Wave Rectifier

While the output of the half-wave rectifier is DC (it is all positive), it would not be

suitable as a power supply for a circuit.  Firstly, the output voltage continually varies

between 0V and Vs-0.7V, and secondly, for half the time there is no output at all. 

2.1.3.2 The Full-wave Rectifier

The circuit in figure addresses the second of these problems since at no time is the output

voltage 0V.  This time four diodes are arranged so that both the positive and negative

parts of the AC waveform are converted to DC. 

Fig:2.3.2(a) Full-Wave Rectifier

When the AC input is positive, diodes A and B are forward-biased, while diodes C and D

are reverse-biased.  When the AC input is negative, the opposite is true - diodes C and D

are forward-biased, while diodes A and B are reverse-biased.

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While the full-wave rectifier is an improvement on the half-wave rectifier, its output still

isn't suitable as a power supply for most circuits since the output voltage still varies

between 0V and Vs-1.4V.  So, if you put 12V AC in, you will 10.6V DC out.

2.1.4 Capacitor Filter

The capacitor-input filter, also called "Pi" filter due to its shape that looks like the

Greek letter pi, is a type of electronic filter. Filter circuits are used to remove unwanted or

undesired frequencies from a signal.

Fig:2.4(a) Capacitor Filter

A typical capacitor input filter consists of a filter capacitor C1, connected across the

rectifier output, an inductor L, in series and another filter capacitor connected across the

load.

1. The capacitor C1 offers low reactance to the AC component of the rectifier output

while it offers infinite reactance to the DC component. As a result the capacitor

shunts an appreciable amount of the AC component while the DC component

continues its journey to the inductor L

2. The inductor L offers high reactance to the AC component but it offers almost

zero reactance to the DC component. As a result the DC component flows through

the inductor while the AC component is blocked.

3. The capacitor C2 bypasses the AC component which the inductor had failed to

block. As a result only the DC component appears across the load RL.

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2.1.5Voltage Regulator

A voltage regulator is an electrical regulator designed to automatically maintain a

constant voltage level. It may use an electromechanical mechanism, or passive or active

electronic components. Depending on the design, it may be used to regulate one or more

AC or DC voltages. There are two types of regulator are they.

Positive Voltage Series (78xx) and

Negative Voltage Series (79xx)

78xx:

’78’ indicate the positive series and ‘xx’indicates the voltage rating. Suppose 7805

produces the maximum 5V.’05’indicates the regulator output is 5V.

79xx:

’78’ indicate the negative series and ‘xx’indicates the voltage rating. Suppose 7905

produces the maximum -5V.’05’indicates the regulator output is -5V.

These regulators consists the three pins there are

Pin1: It is used for input pin.

Pin2: This is ground pin for regulator

Pin3: It is used for output pin. Through this pin we get the output.

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Fig:2.5 Regulator

2.1.6 SWITCH INTERFACING:

CPU accesses the switches through ports. Therefore these switches are connected

to a microcontroller. This switch is connected between the supply and ground terminals.

A single microcontroller (consisting of a microprocessor, RAM and EEPROM and

several ports all on a single chip) takes care of hardware and software interfacing of the

switch.

These switches are connected to an input port. When no switch is pressed, reading

the input port will yield 1s since they are all connected to high (Vcc). But if any switch is

pressed, one of the input port pins will have 0 since the switch pressed provides the path

to ground. It is the function of the microcontroller to scan the switches continuously to

detect and identify the switch pressed.

The switches that we are using in our project are 4 leg micro switches of

momentary type.

Vcc

R

Gnd

Fig:2.6 Interfacing switch with the microcontroller

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P2.0

By reading the pin status, the microcontroller identifies whether the switch is

pressed or not. When the switch is pressed, the corresponding related to this switch press

written in the program will be executed.

2.2 AT89S52 MICROCONTROLLERS:

The AT89S52 is a low-power, high-performance CMOS 8-bit microcontroller

with 8K bytes of in-system programmable Flash memory. The device is manufactured

using Atmel’s high-density nonvolatile memory technology and is compatible with the

industry- standard 80C51 instruction set and pinout. The on-chip Flash allows the

program memory to be reprogrammed in-system or by a conventional nonvolatile

memory programmer. By combining a versatile 8-bit CPU with in-system programmable

Flash on a monolithic chip, the Atmel AT89S52 is a powerful microcontroller which

provides a highly-flexible and cost-effective solution to many embedded control

applications.

2.2.1 Standard Features

8K bytes of Flash,

256 bytes of RAM,

32 I/O lines,

Watchdog timer,

two data pointers,

three 16-bit timer/counters,

a six-vector two-level interrupt architecture,

a full duplex serial port, on-chip oscillator, and

clock circuitry.

In addition, the AT89S52 is designed with static logic for operation down to zero

frequency and supports two software selectable power saving modes.

The Idle Mode stops the CPU while allowing the RAM, timer/counters, serial

port, and interrupt system to continue functioning. The Power-down mode saves the

RAM contents but freezes the oscillator, disabling all other chip functions until the next

interrupt or hardware reset.

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2.2.2 PIN CONFIGURATIONS

14

15

Fig:3.3 block diagram of microcontroller

2.2.2.1 PIN DESCRIPTION

VCC

16

Supply voltage.

GND

Ground.

Port 0

Port 0 is an 8-bit open drain bidirectional I/O port. As an output port, each pin can sink

eight TTL inputs. When 1s are written to port 0 pins, the pins can be used as high

impedance inputs. Port 0 can also be configured to be the multiplexed low order

address/data bus during accesses to external program and data memory. In this mode, P0

has internal pullups. Port 0 also receives the code bytes during Flash programming and

outputs the code bytes during program verification. External pullups are required during

program verification.

Port 1

Port 1 is an 8-bit bidirectional I/O port with internal pullups. The Port 1 output buffers

can sink/source four TTL inputs. When 1s are written to Port 1 pins, they are pulled high

by the internal pullups and can be used as inputs. As inputs, Port 1 pins that are externally

being pulled low will source current (IIL) because of the internal pullups. In addition,

P1.0 and P1.1 can be configured to be the timer/counter 2 external count input (P1.0/T2)

and the timer/counter 2 trigger input (P1.1/T2EX), respectively, as shown in the

following table. Port 1 also receives the low-order address bytes during Flash

programming and verification.

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Table:3.3.1(a) port 1 alternate pin functions

Port 2

Port 2 is an 8-bit bidirectional I/O port with internal pullups. The Port 2 output buffers

can sink/source four TTL inputs. When 1s are written to Port 2 pins, they are pulled high

by the internal pullups and can be used as inputs. As inputs, Port 2 pins that are externally

being pulled low will source current (IIL) because of the internal pullups. Port 2 emits the

high-order address byte during fetches from external program memory and during

accesses to external data memory that use 16-bit addresses (MOVX @ DPTR). In this

application, Port 2 uses strong internal pull-ups when emitting 1s. During accesses to

external data memory that use 8-bit addresses (MOVX @ RI), Port 2 emits the contents

of the P2 Special Function Register. Port 2 also receives the high-order address bits and

some control signals during Flash programming and verification.

Port 3

Port 3 is an 8-bit bidirectional I/O port with internal pullups. The Port 3 output buffers

can sink/source four TTL inputs. When 1s are written to Port 3 pins, they are pulled high

by the internal pullups and can be used as inputs. As inputs, Port 3 pins that are externally

being pulled low will source current (IIL) because of the pullups. Port 3 also serves the

functions of various special features of the AT89S52, as shown in the following table.

Port 3 also receives some control signals for Flash programming and verification.

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Table:3.3.1(b) port 3 alternate functions

RST

Reset input. A high on this pin for two machine cycles while the oscillator is running

resets the device. This pin drives High for 96 oscillator periods after the Watchdog times

out. The DISRTO bit in SFR AUXR (address 8EH) can be used to disable this feature. In

the default state of bit DISRTO, the RESET HIGH out feature is enabled.

ALE/PROG

Address Latch Enable (ALE) is an output pulse for latching the low byte of the address

during accesses to external memory. This pin is also the program pulse input (PROG)

during Flash programming. In normal operation, ALE is emitted at a constant rate of 1/6

the oscillator frequency and may be used for external timing or clocking purposes. Note,

however, that one ALE pulse is skipped during each access to external data memory. If

desired, ALE operation can be disabled by setting bit 0 of SFR location 8EH. With the bit

set, ALE is active only during a MOVX or MOVC instruction. Otherwise, the pin is

weakly pulled high. Setting the ALE-disable bit has no effect if the microcontroller is in

external execution mode.

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PSEN

Program Store Enable (PSEN) is the read strobe to external program memory. When the

AT89S52 is executing code from external program memory, PSEN is activated twice

each machine cycle, except that two PSEN activations are skipped during each access to

external data memory.

EA/VPP

External Access Enable. EA must be strapped to GND in order to enable the device to

fetch code from external program memory locations starting at 0000H up to FFFFH.

Note, however, that if lock bit 1 is programmed, EA will be internally latched on reset.

EA should be strapped to VCC for internal program executions. This pin also receives the

12-volt programming enable voltage (VPP) during Flash programming.

XTAL1

Input to the inverting oscillator amplifier and input to the internal clock operating circuit.

XTAL2

Output from the inverting oscillator amplifier.

2.2.3 MEMORY ORGANIZATION

The microcontroller memory is divided into Program Memory and Data Memory.

Program Memory (ROM) is used for permanent saving program being executed, while

Data Memory (RAM) is used for temporarily storing and keeping intermediate results

and variables. Depending on the model in use (still referring to the whole 8052

microcontroller family) at most a few Kb of ROM and 128 or 256 bytes of RAM can be

used. However all 8052 microcontrollers have 16-bit addressing bus and can address 64

kb memory. It is neither a mistake nor a big ambition of engineers who were working on

basic core development. It is a matter of very clever memory organization which makes

these controllers a real “programmers’ tidbit“.

2.2.3.1 Program Memory

The oldest models of the 8052 microcontroller family did not have any internal program

memory. It was added from outside as a separate chip. These models are recognizable by

their label beginning with 803 (for ex. 8031 or 8032). All later models have a few Kbytes

ROM embedded, Even though it is enough for writing most of the programs, there are

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situations when additional memory is necessary. A typical example of it is the use of so

called lookup tables. They are used in cases when something is too complicated or when

there is no time for solving equations describing some process. The example of it can be

totally exotic or totally common. In those cases all needed estimates and approximates

are executed in advance and the final results are put in the tables (similar to logarithmic

tables).

EA=0 In this case, internal program memory is completely ignored, only a program

stored in external memory is to be executed.

EA=1 In this case, a program from built-in ROM is to be executed first (to the last

location). Afterwards, the execution is continued by reading additional memory.

In both cases, P0 and P2 are not available to the user because they are used for data and

address transmission. Besides, the pins ALE and PSEN are used too.

2.2.3.2 Data Memory

Data Memory is used for temporarily storing and keeping data and intermediate results

created and used during microcontroller’s operating. Besides, this microcontroller family

includes many other registers such as: hardware counters and timers, input/output ports,

serial data buffers etc. The previous versions have the total memory size of 256 locations,

while for later models this number is incremented by additional 128 available registers. In

both cases, these first 256 memory locations (addresses 0-FFh) are the base of the

memory Common to all types of the 8052 microcontrollers. Locations available to the

user occupy memory space with addresses from 0 to 7Fh. First 128 registers and this part

of RAM are divided in several blocks.

The first block consists of 4 banks each including 8 registers designated as R0 to R7.

Prior to access them, a bank containing that register must be selected. Next memory

block (in the range of 20h to 2Fh) is bit- addressable, which means that each bit being

there has its own address from 0 to 7Fh. Since there are 16 such registers, this block

contains in total of 128 bits with separate addresses (The 0th bit of the 20h byte has the

bit address 0 and the 7th bit of the 2Fh byte has the bit address 7Fh). The third groups of

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registers occupy addresses 2Fh-7Fh (in total of 80 locations) and does not have any

special purpose or feature.

In case on-chip memory is not enough, it is possible to add two external memory chips

with capacity of 64Kb each. I/O ports P2 and P3 are used for their addressing and data

transmission.

Similar occurs when it is a needed to read some location from external Data Memory.

Addressing is performed in the same way, while reading or writing is performed via

signals which appear on the control outputs RD or WR.

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Fig:3.4.2(b) memory organisation

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2.2.4 Addressing

While operating, processor processes data according to the program instructions. Each

instruction consists of two parts. One part describes what should be done and another part

indicates what to use to do it. This later part can be data (binary number) or address

where the data is stored. All 8052 microcontrollers use two ways of addressing depending

on which part of memory should be accessed:

2.2.4.1 Direct Addressing

On direct addressing, a value is obtained from a memory location while the address of

that location is specified in instruction. Only after that, the instruction can process data

(how depends on the type of instruction: addition, subtraction, copy…). Obviously, a

number being changed during operating a variable can reside at that specified address.

For example:

Since the address is only one byte in size ( the greatest number is 255), this is how only

the first 255 locations in RAM can be accessed in this case the first half of the basic

RAM is intended to be used freely, while another half is reserved for the SFRs.

2.2.4.2 Indirect Addressing

On indirect addressing, a register which contains address of another register is specified

in the instruction. A value used in operating process resides in that another register. For

example:

Only RAM locations available for use are accessed by indirect addressing (never in the

SFRs). For all latest versions of the microcontrollers with additional memory block

(those 128 locations in Data Memory), this is the only way of accessing them. Simply,

when during operating, the instruction including “@” sign is encountered and if the

specified address is higher than 128 (7F hex.), the processor knows that indirect

addressing is used and jumps over memory space reserved for the SFRs.

On indirect addressing, the registers R0, R1 or Stack Pointer are used for specifying 8-bit

addresses. Since only 8 bits are available, it is possible to access only registers of internal

RAM in this way (128 locations in former or 256 locations in latest versions of the

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microcontrollers). If memory extension in form of additional memory chip is used then

the 16-bit DPTR Register (consisting of the registers DPTRL and DPTRH) is used for

specifying addresses. In this way it is possible to access any location in the range of 64K.

2.2.5 REGISTERS

2.2.5.1 SFRs (Special Function Registers)

SFRs are a kind of control table used for running and monitoring microcontroller’s

operating. Each of these registers, even each bit they include, has its name, address in the

scope of RAM and clearly defined purpose ( for example: timer control, interrupt, serial

connection etc.). Even though there are 128 free memory locations intended for their

storage, the basic core, shared by all types of 8052 controllers, has only 21 such registers.

Rest of locations are intentionally left free in order to enable the producers to further

improved models keeping at the same time compatibility with the previous versions. It

also enables the use of programs written a long time ago for the microcontrollers which

are out of production now.

2.2.5.2 A Register (Accumulator)

This is a general-purpose register which serves for storing intermediate results

during operating. A number (an operand) should be added to the accumulator prior to

execute an instruction upon it. Once an arithmetical operation is preformed by the ALU,

the result is placed into the accumulator. If a data should be transferred from one register

to another, it must go through accumulator. For such universal purpose, this is the most

commonly used register that none microcontroller can be imagined without (more than a

half 8052 microcontroller's instructions used use the accumulator in some way).

2.2.5.3 B Register

B register is used during multiply and divide operations which can be performed

only upon numbers stored in the A and B registers. All other instructions in the program

can use this register as a spare accumulator (A).

During programming, each of registers is called by name so that their exact address is not

so important for the user. During compiling into machine code (series of hexadecimal

25

numbers recognized as instructions by the microcontroller), PC will automatically,

instead of registers’ name, write necessary addresses into the microcontroller.

2.2.5.4 R Registers (R0-R7)

This is a common name for the total 8 general purpose registers (R0, R1,

R2 ...R7). Even they are not true SFRs, they deserve to be discussed here because of their

purpose. The bank is active when the R registers it includes are in use. Similar to the

accumulator, they are used for temporary storing variables and intermediate results.

Which of the banks will be active depends on two bits included in the PSW Register.

These registers are stored in four banks in the scope of RAM.

2.3 IR SECTION:

2.3.1 IR GENERATION

To generate a 36 KHz pulsating infrared is quite easy, more difficult is to receive

and identify this frequency.  This is why some companies produce infrared receives, that

contains the filters, decoding circuits and the output shaper, that delivers a square wave,

meaning the existence or not of the 36kHz incoming pulsating infrared.

It means that those 3 dollars small units, have an output pin that goes high (+5V)

when there is a pulsating 36kHz infrared in front of it, and zero volts when there is not

this radiation.

Fig: 4.1(a) IR transmitter

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A square wave of approximately 27uS (microseconds) injected at the base of a transistor,

can drive an infrared LED to transmit this pulsating light wave.  Upon its presence, the

commercial receiver will switch its output to high level (+5V).If you can turn on and off

this frequency at the transmitter, your receiver's output will indicate when the transmitter

is on or off.

Fig: 4.1(b) waveform for transmitter

Those IR demodulators have inverted logic at its output, when a burst of IR is sensed it

drives its output to low level, meaning logic level = 1.

The TV, VCR, and Audio equipment manufacturers for long use infra-red at their remote

controls.  To avoid a Philips remote control to change channels in a Panasonic TV, they

use different codification at the infrared, even that all of them use basically the same

transmitted frequency, from 36 to 50 KHz.  So, all of them use a different combination of

bits or how to code the transmitted data to avoid interference. 

RC-5

Various remote control systems are used in electronic equipment today. The RC5

control protocol is one of the most popular and is widely used to control numerous home

appliances, entertainment systems and some industrial applications including utility

consumption remote meter reading, contact-less apparatus control, telemetry data

transmission, and car security systems. Philips originally invented this protocol and

virtually all Philips’ remotes use this protocol. Following is a description of the RC5.

27

When the user pushes a button on the hand-held remote, the device is activated and sends

modulated infrared light to transmit the command. The remote separates command data

into packets. Each data packet consists of a 14-bit data word, which is repeated if the user

continues to push the remote button. The data packet structure is as follows:

2 start bits,

1 control bit,

5 address bits,

6 command bits.

The start bits are always logic ‘1’ and intended to calibrate the optical receiver automatic

gain control loop. Next, is the control bit. This bit is inverted each time the user releases

the remote button and is intended to differentiate situations when the user continues to

hold the same button or presses it again. The next 5 bits are the address bits and select the

destination device. A number of devices can use RC5 at the same time. To exclude

possible interference, each must use a different address. The 6 command bits describe the

actual command. As a result, a RC5 transmitter can send the 2048 unique commands.

The transmitter shifts the data word, applies Manchester encoding and passes the created

one-bit sequence to a control carrier frequency signal amplitude modulator. The

amplitude modulated carrier signal is sent to the optical transmitter, which radiates the

infrared light. In RC5 systems the carrier frequency has been set to 36 kHz. Figure below

displays the RC5 protocol.

The receiver performs the reverse function. The photo detector converts optical

transmission into electric signals, filters it and executes amplitude demodulation. The

receiver output bit stream can be used to decode the RC5 data word. This operation is

done by the microprocessor typically, but complete hardware implementations are

present on the market as well. Single-die optical receivers are being mass produced by a

number of companies such as Siemens, Temic, Sharp, Xiamen Hualian, Japanese Electric

and others. Please note that the receiver output is inverted (log. 1 corresponds to

illumination absence).

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2.3.2 IR TRANSMITTER:

The IR LED emitting infrared light is put on in the transmitting unit. To generate IR

signal, 555 IC based astable multivibrator is used. Infrared LED is driven through

transistor BC 548.

IC 555 is used to construct an astable multivibrator which has two quasi-stable

states. It generates a square wave of frequency 38 kHz and amplitude 5Volts. It is

required to switch ‘ON’ the IR LED. The IR transmitter circuit is as shown below:

2.3.2.1 555 TIMER:

Fig:4.2.1(a) 555- timer

The 555 is an integrated circuit (chip) implementing a variety of timer and

multivibrator applications. It was designed in 1970 and introduced in 1971 by Signetics

(later acquired by Philips). The original name was the SE555/NE555 and was called

29

"The IC Time Machine". It is still in wide use, thanks to its ease of use, low price and

good stability. As of 2003, 1 billion units are manufactured every year.

The 555 timer is one of the most popular and versatile integrated circuits ever

produced. It includes 23 transistors, 2 diodes and 16 resistors on a silicon chip installed in

an 8-pin mini dual-in-line package (DIP-8). The 556 is a 14-pin DIP that combines two

555s on a single chip.

Fig:4.2.1(b) 555 timer pin

Pin Functions - 8 pin package

Ground (Pin 1)

  This pin is connected directly to ground.

Trigger (Pin 2)

   This pin is the input to the lower comparator and is used to set the latch, which in turn

causes the output to go high.

Output (Pin 3)

  Output high is about 1.7V less than supply. Output high is capable of sourcing up to

200mA while output low is capable of sinking up to 200mA.

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Reset (Pin 4)

This is used to reset the latch and return the output to a low state. The reset is an

overriding function. When not used connect to V+.

Control (Pin 5)

Allows access to the 2/3V+ voltage divider point when the 555 timer is used in voltage

control mode. When not used connect to ground through a 0.01 uF capacitor.

Threshold (Pin 6)

 This is an input to the upper comparator.

Discharge (Pin 7)

This is the open collector to Q14.

V+ (Pin 8)

 This connects to Vcc and the Philips data book states the ICM7555 CMOS version

operates 3V - 16V DC while the NE555 version is 3V - 16V DC.

The 555 has three operating modes:

Monostable mode: in this mode, the 555 functions as a "one-shot". Applications

include timers, missing pulse detection, bounce free switches, touch switches,

Frequency Divider, Capacitance Measurement, Pulse Width Modulation (PWM)

etc

Astable mode: Free Running mode: the 555 can operate as an oscillator. Uses

include LED and lamp flashers, pulse generation, logic clocks, tone generation,

security alarms, pulse position modulation, etc.

Bistable mode: The 555 can operate as a flip-flop, if the DIS pin is not connected

and no capacitor is used. Uses include bounce free latched switches, etc.

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This circuit diagram shows how a 555 timer IC is configured to function as an

astable multivibrator.  An astable multivibrator is a timing circuit whose 'low' and

'high' states are both unstable.  As such, the output of an astable multivibrator toggles

between 'low' and 'high' continuously, in effect generating a train of pulses. This

circuit is therefore also known as a 'pulse generator' circuit.

In this circuit, capacitor C1 charges through R1 and R2, eventually building up

enough voltage to trigger an internal comparator to toggle the output flip-flop.  Once

toggled, the flip-flop discharges C1 through R2 into pin 7, which is the discharge pin. 

When C1's voltage becomes low enough, another internal comparator is triggered to

toggle the output flip-flop. This once again allows C1 to charge up through R1 and R2

and the cycle starts all over again.

     

C1's charge-up time t1 is given by: t1 = 0.693(R1+R2) C1. C1's discharge time

t2 is given by: t2 = 0.693(R2) C1.  Thus, the total period of one cycle is t1+t2 = 0.693

C1 (R1+2R2).  The frequency f of the output wave is the reciprocal of this period, and

is therefore given by:

f = 1.44/ (C1 (R1+2R2))

where f is in Hz if R1 and R2 are in megaohms and C1 is in microfarads.  

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Fig:4.2.1(c) astable multivibrater

2.3.3 IR RECEIVER

The TSOP17.. – Series are miniaturized receivers for infrared remote control

systems. PIN diode and preamplifier are assembled on lead frame, the epoxy package is

designed as IR filter.

The demodulated output signal can directly be decoded by a microprocessor.

TSOP17.. is the standard IR remote control receiver series, supporting all major

transmission codes.

Features

Photo detector and preamplifier in one package

Internal filter for PCM frequency

Improved shielding against electrical field disturbance

TTL and CMOS compatibility

Output active low

Low power consumption

High immunity against ambient light

Continuous data transmission possible (up to 2400 bps)

Suitable burst length .10 cycles/burst

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Fig: 4.3(a) block diagram of IR receiver

Fig: 4.3(b) application circuit

Suitable Data Format

The circuit of the TSOP17 is designed in that way that unexpected output pulses

due to noise or disturbance signals are avoided. A bandpass filter, an integrator stage and

an automatic gain control are used to suppress such disturbances. The distinguishing

mark between data signal and disturbance signal are carrier frequency, burst length and

duty cycle. The data signal should fulfill the following condition:

• Carrier frequency should be close to center frequency of the bandpass (e.g. 38 KHz).

• Burst length should be 10 cycles/burst or longer.

• After each burst which is between 10 cycles and 70 cycles a gap time of at least 14

cycles is necessary.

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• For each burst which is longer than 1.8ms a corresponding gap time is necessary at

some time in the data stream. This gap time should have at least same length as the burst.

• Up to 1400 short bursts per second can be received continuously.

Some examples for suitable data format are: NEC Code, Toshiba Micom Format,

Sharp Code, RC5 Code, RC6 Code, R–2000 Code and Sony Format (SIRCS). When a

disturbance signal is applied to the TSOP17.. It can still receive the data signal. However

the sensitivity is reduced to that level that no unexpected pulses will occur. Some

examples for such disturbance signals which are suppressed by the TSOP17 are:

• DC light (e.g. from tungsten bulb or sunlight)

• Continuous signal at 38 kHz or at any other frequency

• Signals from fluorescent lamps with electronic ballast

2.3.4 IR Emitter and phototransistor:

An infrared emitter is an LED made from gallium arsenide, which emits near-

infrared energy at about 880nm. The infrared phototransistor acts as a transistor with the

base voltage determined by the amount of light hitting the transistor. Hence it acts as a

variable current source. Greater amount of IR light cause greater currents to flow through

the collector-emitter leads.

The variable current traveling through the resistor causes a voltage drop in the pull-up

resistor. This voltage is measured as the output of the device

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Fig: 4.4

3.3.5 Photo Sensors array:

IR reflectance sensors contain a matched infrared transmitter and infrared receiver pair.

These devices work by measuring the amount of light that is reflected into the receiver.

Because the receiver also responds to ambient light, the device works best when well

shielded from ambient light, and when the distance between the sensor and the reflective

surface is small(less than 5mm). IR reflectance sensors are often used to detect white and

black surfaces. White surfaces generally reflect well, while black surfaces reflect poorly.

One of such applications is the line follower of a robot.

Fig:

4.5(a) IR emitter

detector circuit

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fig: 4.5(b) Schematic Diagram for a Single Pair of Infrared Transmitter and

Receiver

Fig:4.5(c) schematic of a single sensor

2.4 LM 324

2.4.1 FEATURES:

Wide gain bandwidth . : 1.3MHZ input common-mode voltage range

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Includes ground .largevoltage gain : 100DB .very lowsupply current/ampli :

375ma .low input bias current : 20NA low input offset voltage : 5mv max.

Low input offset current : 2NA wide power supply range :

Single supply : +3v to +30v

Dual supplies : ±1.5v to ±15v

2.4.2 DESCRIPTION

These circuits consist of four independent, high gain, internally frequency compensated

operational amplifiers .They operate from a single power supply over a wide range of

voltages. Operation from split power supplies is also possible and the low power supply

current drain is independent of the magnitude of the power supply voltage.

Fig:6.2(a) pin configuration (top view)

2.5 DC GEARED MOTORS

DC motor

A DC motor is an electric motor that runs on direct current (DC) electricity.

DC Motor Connections

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Figure shows schematically the different methods of connecting the field and armature

circuits in a DC Motor. The circular symbol represents the armature circuit, and the

squares at the side of the circle represent the brush commutator system. The direction of

the arrows indicates the direction of the magnetic fields.

Fig:7 DC motor connections

2.5.1 Principles of operation

In any electric motor, operation is based on simple electromagnetism. A current-carrying

conductor generates a magnetic field; when this is then placed in an external magnetic

field, it will experience a force proportional to the current in the conductor, and to the

strength of the external magnetic field. As you are well aware of from playing with

magnets as a kid, opposite (North and South) polarities attract, while like polarities

(North and North, South and South) repel. The internal configuration of a DC motor is

designed to harness the magnetic interaction between a current-carrying conductor and an

external magnetic field to generate rotational motion.

Let's start by looking at a simple 2-pole DC electric motor (here red represents a magnet

or winding with a "North" polarization, while green represents a magnet or winding with

a "South" polarization).

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Fig:7.1(a) internal structure of motor

Every DC motor has six basic parts -- axle, rotor (a.k.a., armature), stator, commutator,

field magnet(s), and brushes. In most common DC motors (and all that Beamers will see),

the external magnetic field is produced by high-strength permanent magnets. The stator is

the stationary part of the motor -- this includes the motor casing, as well as two or more

permanent magnet pole pieces. The rotor (together with the axle and attached

commutator) rotates with respect to the stator. The rotor consists of windings (generally

on a core), the windings being electrically connected to the commutator. The above

diagram shows a common motor layout -- with the rotor inside the stator (field) magnets.

The geometry of the brushes, commutator contacts, and rotor windings are such that

when power is applied, the polarities of the energized winding and the stator magnet(s)

are misaligned, and the rotor will rotate until it is almost aligned with the stator's field

magnets. As the rotor reaches alignment, the brushes move to the next commutator

contacts, and energize the next winding. Given our example two-pole motor, the rotation

reverses the direction of current through the rotor winding, leading to a "flip" of the

rotor's magnetic field, driving it to continue rotating.

In real life, though, DC motors will always have more than two poles (three is a very

common number). In particular, this avoids "dead spots" in the commutator. You can

imagine how with our example two-pole motor, if the rotor is exactly at the middle of its

rotation (perfectly aligned with the field magnets), it will get "stuck" there. Meanwhile,

with a two-pole motor, there is a moment where the commutator shorts out the power

supply (i.e., both brushes touch both commutator contacts simultaneously). This would

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be bad for the power supply, waste energy, and damage motor components as well. Yet

another disadvantage of such a simple motor is that it would exhibit a high amount of

torque "ripple" (the amount of torque it could produce is cyclic with the position of the

rotor).

Fig:7.1(b) motor rotation in clockwise direction

So since most small DC motors are of a three-pole design, let's tinker with the workings

of one via an interactive animation.

Fig:7.1(c) 3 pole design

You'll notice a few things from this -- namely, one pole is fully energized at a time (but

two others are "partially" energized). As each brush transitions from one commutator

contact to the next, one coil's field will rapidly collapse, as the next coil's field will

rapidly charge up (this occurs within a few microsecond). We'll see more about the

effects of this later, but in the meantime you can see that this is a direct result of the coil

windings' series wiring:

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Fig:7.1(d) iron core amature

The use of an iron core armature (as in the Mabuchi, above) is quite common, and has a

number of advantages. First off, the iron core provides a strong, rigid support for the

windings -- a particularly important consideration for high-torque motors. The core also

conducts heat away from the rotor windings, allowing the motor to be driven harder than

might otherwise be the case. Iron core construction is also relatively inexpensive

compared with other construction types.

But iron core construction also has several disadvantages. The iron armature has a

relatively high inertia which limits motor acceleration. This construction also results in

high winding inductances which limit brush and commutator life.

In small motors, an alternative design is often used which features a 'coreless' armature

winding. This design depends upon the coil wire itself for structural integrity. As a result,

the armature is hollow, and the permanent magnet can be mounted inside the rotor coil.

Coreless DC motors have much lower armature inductance than iron-core motors of

comparable size, extending brush and commutator life.

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Fig:7.1(e) parts of motor

DC motor behavior

High-speed output

This is the simplest trait to understand and treat -- most DC motors run at very high

output speeds (generally thousands or tens of thousands of RPM). While this is fine for

some BEAM bots (say, photo poppers or solar rollers), many BEAM bots (walkers,

heads) require lower speeds -- you must put gears on your DC motor's output for these

applications.

2.6 H-BRIDGE:

An H-bridge is an electronic circuit which enables DC electric motors to be run forwards

or backwards. These circuits are often used in robotics. H-bridges are available as

integrated circuits, or can be built from discrete components.

Fig:8 H-bridge switch diagram

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The two basic states of a H-bridge. The term "H-bridge" is derived from the

typical graphical representation of such a circuit. An H-bridge is built with four switches

(solid-state or mechanical). When the switches S1 and S4 (according to the first figure)

are closed (and S2 and S3 are open) a positive voltage will be applied across the motor.

By opening S1 and S4 switches and closing S2 and S3 switches, this voltage is reversed,

allowing reverse operation of the motor.

Using the nomenclature above, the switches S1 and S2 should never be closed at the

same time, as this would cause a short circuit on the input voltage source. The same

applies to the switches S3 and S4. This condition is known as shoot-through.

2.6.1 Operation

The H-Bridge arrangement is generally used to reverse the polarity of the motor, but can

also be used to 'brake' the motor, where the motor comes to a sudden stop, as the motors

terminals are shorted, or to let the motor 'free run' to a stop, as the motor is effectively

disconnected from the circuit. The following table summarizes operation.

S1 S2 S3 S4 Result

1 0 0 1 Motor moves right

0 1 1 0 Motor moves left

0 0 0 0 Motor free runs

0 1 0 1 Motor brakes

Table: 8.1 H-bridge switch operation

2.6.2 H-Bridge Driver:

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The switching property of this H-Bridge can be replaced by a Transistor or a Relay or a

Mosfet or even by an IC. Here we are replacing this with an IC named L293D as the

driver whose description is as given below.

Features:

600mA OUTPUT CURRENT CAPABILITY

PER CHANNEL

1.2A PEAK OUTPUT CURRENT (non repetitive)

PER CHANNEL

ENABLE FACILITY

OVERTEMPERATURE PROTECTION

LOGICAL "0" INPUT VOLTAGE UP TO 1.5 V

(HIGH NOISE IMMUNITY)

INTERNAL CLAMP DIODES

DESCRIPTION

The Device is a monolithic integrated high voltage, high current four channel driver

designed to accept standard DTL or TTL logic levels and drive inductive loads (such as

relays solenoides, 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 The L293DD is assembled in a

20 lead surface mount which has 8 center pins connected together and used for heat

sinking.

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2.6.3 BLOCK DIAGRAM:

Fig: 8.5(a) block diagram of H-bridge

2.6.4 PIN CONNECTIONS

fig:8.5(b) pin configuration of H-bridge

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CHAPTER:3

WORKING PROCEDURE

3.1 WORKING PROCEDURE

Robotics is an interesting subject to discuss about and in this advanced world Robots are

becoming a part of our life. In this project we are going to discuss about a robot which is

capable of following a line without the help of any external source.

The Embedded Line following robot uses two motors to control rear wheels and the

single front wheel is free. It has 3-infrared sensors on the bottom for detection of black

tracking tape. When the middle sensor detects the black color, this sensor output is given

to the comparator LM324. The output of comparator compares this sensor output with a

reference voltage and gives an output. The output of comparator will be low when it

receives an input from the sensor.

We follow a simple logic to implement this project. As we know that black colour is

capable of absorbing the radiation and white colour or a bright colour reflects the

radiation back. Here we use 3 pairs of IR TX and Rx .The robot uses these IR sensors to

sense the line and the arrangement is made such that sensors face the ground. The output

from the sensors is an analog signal which depends on the amount of light reflected back

and this analog signal is given to the comparator to produce 0s and 1s.

Internally we have an OTP (one time programmable) processor which is used to

control the rotation of the wheels. The rotation of these wheels depends up on the

response from the comparator. Let us assume that when a sensor is on the black line it

reads 0 and when it is on the bright surface it reads 1.

Here we can get three different cases, they are:

1. Straight direction

2. Right curve

3. Left curve

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3.1.1 Straight direction:

We can expect our robot to move in straight direction when the middle sensors response

is low and the remaining two sensors response is high. i.e., according to our arrangement

the middle sensor will always be on the line and as the line is black in colour it will not

reflect the emitted radiation back and the response of the sensor will be low and the

response of the remaining two sensors will be high as they will be on the bright surface.

3.1.2 Right curve:

When a right curve is found on the line the responses will change i.e. the response of the

first sensor which is to the right will become low as that sensor will be facing the black

line and the reaming sensors response will be high. We this data is achieved the control

of the wheels is changed i.e. the right wheel is held and the left wheel is made to move

freely until the response from the middle sensor becomes low. Then the same process

repeats again.

3.1.3 Left curve:

When a left curve is found on the line the response of the left most sensor will be

changed from high to low as the sensor will now face the black or the dark surface. Then

the control of the wheel changes i.e. by holding the left wheel and allowing the right

wheel to move freely until the middle sensor changes it’s response fro high to low.

The same process continues for all the turns and the robot moves continuously until the

supply is remove

3.2 STEPS TO FOLLOW THE LINE (USING SINGLE SENSOR):

Start

Check for line

Line detected go right

Check for line

If no line turn left till line detected

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CHAPTER: 4

SOFTWARE TOOLS

4.1 KEIL SOFTWARE:

Keil compiler is a software used where the machine language code is written and

compiled. After compilation, the machine source code is converted into hex code which

is to be dumped into the microcontroller for further processing. Keil compiler also

supports C language code.

4.2 STEPS TO WRITE AN ASSEMBLY LANGUAGE PROGRAM IN KEIL AND

HOW TO COMPILE IT:

1. Install the Keil Software in the PC in any of the drives.

2. After installation, an icon will be created with the name “Keil uVision3”. Just

drag this icon onto the desktop so that it becomes easy whenever you try to write

programs in keil.

3. Double click on this icon to start the keil compiler.

4. A page opens with different options in it showing the project workspace at the

leftmost corner side, output window in the bottom and an ash coloured space for

the program to be written.

5. Now to start using the keil, click on the option “project”.

6. A small window opens showing the options like new project, import project, open

project etc. Click on “New project”.

7. A small window with the title bar “Create new project” opens. The window asks

the user to give the project name with which it should be created and the

destination location. The project can be created in any of the drives available. You

can create a new folder and then a new file or can create directly a new file.

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8. After the file is saved in the given destination location, a window opens where a

list of vendors will be displayed and you have to select the device for the target

you have created.

9. The most widely used vendor is Atmel. So click on Atmel and now the family of

microcontrollers manufactured by Atmel opens. You can select any one of the

microcontrollers according to the requirement.

10. When you click on any one of the microcontrollers, the features of that particular

microcontroller will be displayed on the right side of the page. The most

appropriate microcontroller with which most of the projects can be implemented

is the AT89S52. Click on this microcontroller and have a look at its features. Now

click on “OK” to select this microcontroller.

11. A small window opens asking whether to copy the startup code into the file you

have created just now. Just click on “No” to proceed further.

12. Now you can see the TARGET and SOURCE GROUP created in the project

workspace.

13. Now click on “File” and in that “New”. A new page opens and you can start

writing program in it.

14. After the program is completed, save it with any name but with the .asm

extension. Save the program in the file you have created earlier.

15. You can notice that after you save the program, the predefined keywords will be

highlighted in bold letters.

16. Now add this file to the target by giving a right click on the source group. A list of

options open and in that select “Add files to the source group”. Check for this file

where you have saved and add it.

17. Right click on the target and select the first option “Options for target”. A window

opens with different options like device, target, output etc. First click on “target”.

18. Since the set frequency of the microcontroller is 11.0592 MHz to interface with

the PC, just enter this frequency value in the Xtal (MHz) text area and put a tick

on the Use on-chip ROM. This is because the program what we write here in the

keil will later be dumped into the microcontroller and will be stored in the inbuilt

ROM in the microcontroller.

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19. Now click the option “Output” and give any name to the hex file to be created in

the “Name of executable” text area and put a tick to the “Create HEX file” option

present in the same window. The hex file can be created in any of the drives. You

can change the folder by clicking on “Select folder for Objects”.

20. Now to check whether the program you have written is errorless or not, click on

the icon exactly below the “Open file” icon which is nothing but Build Target

icon. You can even use the shortcut key F7 to compile the program written.

21. To check for the output, there are several windows like serial window, memory

window, project window etc. Depending on the program you have written, select

the appropriate window to see the output by entering into debug mode.

22. The icon with the letter “d” indicates the debug mode.

23. Click on this icon and now click on the option “View” and select the appropriate

window to check for the output.

24. After this is done, click the icon “debug” again to come out of the debug mode.

25. The hex file created as shown earlier will be dumped into the microcontroller with

the help of another software called Proload.

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4.3 PROLOAD:

Proload is software which accepts only hex files. Once the machine code is

converted into hex code, that hex code has to be dumped into the microcontroller placed

in the programmer kit and this is done by the Proload. Programmer kit contains a

microcontroller on it other than the one which is to be programmed. This microcontroller

has a program in it written in such a way that it accepts the hex file from the keil

compiler and dumps this hex file into the microcontroller which is to be programmed. As

this programmer kit requires power supply to be operated, this power supply is given

from the power supply circuit designed above. It should be noted that this programmer kit

contains a power supply section in the board itself but in order to switch on that power

supply, a source is required. Thus this is accomplished from the power supply board with

an output of 12volts or from an adapter connected to 230 V AC.

1. Install the Proload Software in the PC.

2. Now connect the Programmer kit to the PC (CPU) through serial cable.

3. Power up the programmer kit from the ac supply through adapter.

4. Now place the microcontroller in the GIF socket provided in the programmer kit.

5. Click on the Proload icon in the PC. A window appears providing the information

like Hardware model, com port, device type, Flash size etc. Click on browse

option to select the hex file to be dumped into the microcontroller and then click

on “Auto program” to program the microcontroller with that particular hex file.

6. The status of the microcontroller can be seen in the small status window in the

bottom of the page.

7. After this process is completed, remove the microcontroller from the programmer

kit and place it in your system board. Now the system board behaves according to

the program written in the microcontroller.

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CHAPTER: 5 RESULT

The objective of the line following robot is to follow a line on its given path which is

obtained for which it uses IR sensors which detects the line and sends the information to

LM324 comparator and then to H bridge which controls the working of the wheel’s.

Microcontroller controls the other operations.

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CHAPTER :6

CONCLUSION AND FUTURE SCOPE

CONCLUSION:

In this project we have studied and implemented a Line Following Robot using a

Microcontroller for blind people. The programming and interfacing of microcontroller

has been mastered during the implementation.

FUTURE SCOPE:

• Smarter versions of line followers are used to deliver mails within office building

and deliver medications in a hospital.

• This technology has been suggested for running buses and other mass transit

systems and may end up as a part of autonomous cars navigating the freeway.

REFERENCES:

1. www.howstuffworks.com

2. EMBEDDED SYSTEM BY RAJ KAMAL

3. 8051 MICROCONTROLLER AND EMBEDDED SYSTEMS BY MAZZIDI

4. Magazines-Electronics for you

5. Electrikindia.

6. www.electronic projects.com

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