Final report on line follower

A
TERM PAPER REPORT
ON

LINE FOLLOWER ROBOT
Submitted by:
Priya Hada
B.Tech (ECE)
5rd Semester

Amity School of Engineering &
Technology
AMITY UNIVERSITY RAJASTHAN
OCT, 2013

1

CERTIFICATE

This is to certify that Priya Hada, student of B.Tech. in Electronics and
Communication Engineering has carried out the work presented in the project of the
Training entitled “LINE FOLLOWER ROBOT” as a part of third Year programme of
Bachelor of Technology in of B.Tech. in Electronics and Communication Engineering
from Amity School of Engineering and Technology, Amity University Rajasthan, under
my supervision.

STUDENT

Guide

(Priya Hada)

(Achyut Sharma)
ASET (AUR)
Date:22/10/13

2

ACKNOWLEDGEMENT

It has come out to be a sort of great pleasure and experience for me to work on the
project line follower robot(LFR).I wish to express my indebtedness to those who helped
us i.e. the faculty of our Institute Mr. Achyut Sharma during the preparation of the
manual script of this text. This would not have been made successful without his help
and precious suggestions. Finally, I also warmly thanks to all our colleagues who
encouraged us to an extent, which made the project successful.

Priya Hada

3

TABLE OF CONTENTS

1.INTRODUCTION…………………………………………………………………7
1.1. INTRODUCTION TO LFR................................................................................... 9
1.2 BLOCK DIAGRAM. ........................................................................................... 11
1.3. INTRODUCTION TO EMBEDDED SYSTEM ................................................. 12
2. HARDWARE DISCRIPTION ............................................................................... 13
2.1 BASIC HARDWARE........................................................................................... 13
2.2 AT89C51 MICROCONTROLLER ...................................................................... 16
2.3 IR SENSORS ........................................................................................................ 17
2.4 LM324 .................................................................................................................. 17
2.5 H BRIDGE .......................................................................................................... 183
3.WORKING PROCEDURE .................................................................................... .21
4.SOFTWARE SKILS ................................................................................................ 23
5.CONCLUSION AND FUTURE SCOPE ................................................................ 23

4

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.

5

1.2 BLOCK DIAGRAM:

Power
Supply Unit

Photo Sensor
Array

Crystal

AT89C51
Microcontroller

Reset
circuit

H-Bridge

Left
Motor

12 V Lead Acid

Right
Motor

Battery

Fig.1.1 Block diagram of line follower

6

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.

Embedded
System

Software

Hardware

o

ALP

o

Processor

o

C

o

Peripherals

o

VB

o

memory

Etc.,
Figure: 1.2 Block diagram of Embedded System

7

Embedded consist of both software and hardware :
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

8

2. HARDWARE EXPLANATION
2.1 BASIC HARDWARE
2.1.1 BLOCK DIAGRAM FOR REGULATED POWER SUPPLY :

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.
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.
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.

9

Fig: 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).

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-

Fig: 2.3.1(a) Half Wave Rectifier

10

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.
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.

11

2.1.4 Voltage 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.

Fig: 2.4 Regulator (photo courtesy: positron technologies)

12

0

2.2 AT89C51 MICROCONTROLLERS:
The AT89C51 is a low-power, high-performance CMOS 8-bit microcontroller with
4K bytes of programmable Flash memory and erasable read only memory
(PEROM). The device is manufactured using Atmel‟s high-density nonvolatile
memory technology and is compatible with the industry- standard MCS-51
instruction set and pin out. 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 Flash on a monolithic chip, the Atmel
AT89C51 is a powerful microcontroller which provides a highly-flexible and costeffective solution to many embedded control applications.

2.2.1 PIN CONFIGURATIONS

13

2.2.2 Standard Features
4K bytes of Flash,
128* 8 bits of internal RAM,
32 programmable I/O lines,
Full static operation: 0Hz to 24 Mhz
Three level program memory Lock
two 16-bit timer/counters,
a six-vector two-level interrupt architecture,

2.2.3 PIN DESCRIPTION
VCC
Supply voltage.
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 pull ups. Port 0 also receives the code bytes during Flash
programming and outputs the code bytes during program verification. External pull
ups are required during program verification.

Port 1

14

Port 1 is an 8-bit bidirectional I/O port with internal pull ups. 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 pull ups 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
pull ups. Port 1 also receives the low-order address bytes during Flash programming.

Port 2
Port 2 is an 8-bit bidirectional I/O port with internal pull ups. The Port 2 output
pulled high by the internal pull ups 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
pull ups. 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
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 AT89C51, as shown
in the following table. Port 3 also receives some control signals for Flash
programming and verification.

15

Table: 2.2.1 port 3 alternate functions
RST
Reset input. A high on this pin for two machine cycles while the oscillator is running
resets the device.
ALE/PROG
Address Latch Enable (ALE) is an output pulse for latching the low byte of the
address during accesses to external memory. 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.
PSEN
Program Store Enable (PSEN) is the read strobe to external program memory. When
the AT89C51 is executing code from external program memory, PSEN is activated

16

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.
XTAL1
Input to the inverting oscillator amplifier and input to the internal clock operating
circuit.
XTAL2
Output from the inverting oscillator amplifier.

2.3 IR Sensors
An Infra-Red sensor detects Infra-Red light/white light from a particular object/line
and then converts light energy to electrical energy. An IR sensor pair consists of an
emitter and a detector. The emitter is blue in color and the detector can be grey, black
or white in color.

Fig.2.3.1 TX- Emitter & RX- Detector (Photo courtesy: positron technologies)

17

2.3.1 IR Emitter:
An infra-red emitter is a Light Emitting Diode (LED) made from Gallium Arsenide. It
detects IR energy at a wavelength of 880nm and emits the same. 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.

2.3.2 IR Detector:
An infra-red detector is a photo detector. It detects IR energy emitted by the emitter
and converts it into electrical energy.
The main principle involved in the conversion of light energy to electrical energy is
PHOTOELECTRIC EFFECT.
IR sensor circuit to detect a black line on white background:

Fig: 2.3.2. IR sensor circuit

The output is taken at negative terminal of IR detector.
The output can be taken to a microcontroller either to its ADC (Analog to Digital
Converter) or LM 339 can be used as a comparator.

18

2.4 LM 324
2.4.1 FEATURES:
Wide gain bandwidth : 1.3MHZ input common-mode voltage range
Includes ground .large voltage gain: 100DB .very low supply 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:2.4.1. pin configuration (top view)

19

2.5 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: 2.5.1.H-bridge switch diagram

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.

2.5.1 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.

20

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: 2.5.1 H-bridge switch operation

2.5.2 H-Bridge Driver:
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. 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 as 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
L293D is assembled in a 20 lead surface mount which has 8 center pins connected
together and used for heat sinking.

21

2.5.3 Features:
600mA OUTPUT CURRENT CAPABILITY
PER CHANNEL
1.2A PEAK OUTPUT CURRENT (non repetitive)
ENABLE FACILITY
OVERTEMPERATURE PROTECTION
LOGICAL "0" INPUT VOLTAGE UP TO 1.5 V
(HIGH NOISE IMMUNITY)
INTERNAL CLAMP DIODES

2.5.4 BLOCK DIAGRAM:

Fig: 2.5.2. block diagram of H-bridge

22

2.5.5 PIN CONNECTIONS

Fig: 2.5.3 pin configuration of H-bridge

3. WORKING PROCEDURE
3.1 WORKING
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

23

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

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

24

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 is response from high to
low.The same process continues for all the turns and the robot moves continuously
until the supply is remove

3.1.4 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

3.1.5 DISADVANTAGES
 LFR follows a black line about 1 or 2 inches in width on a white surface.
 LFR are simple robots with an additional sensors placed on them.
 Needs a path to run either white or black since the IR rays should reflectfrom
the particular path.
 Slow speed and instability on different line thickness or hard angles.

25

3.1.6 APPLICATIONS:
 Guidance system for industrial robots moving on shop floor etc.
 Industrial applications.
 Home applications.

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 LANGUAGE PROGRAM :
#include<regx51.h>
void main()
{
while(1)
{
if(P1_0==0&&P1_1==0)
{
P2=0x00;
}
if(P1_0==1&&P1_1==1)

26

{
P2=0xF5;
}
if(P1_0==0&&P1_1==1)
{
P2=0xF4;
}
if(P1_0==1&&P1_1==0)
{
P2=0xF1;
}
}
}

4.3 PROTEUS SIMULATION

9

29
30
31

1
2
3
4
5
6
7
8

XTAL2

RST

PSEN
ALE
EA

P1.0
P1.1
P1.2
P1.3
P1.4
P1.5
P1.6
P1.7

P0.0/AD0
P0.1/AD1
P0.2/AD2
P0.3/AD3
P0.4/AD4
P0.5/AD5
P0.6/AD6
P0.7/AD7
P2.0/A8
P2.1/A9
P2.2/A10
P2.3/A11
P2.4/A12
P2.5/A13
P2.6/A14
P2.7/A15
P3.0/RXD
P3.1/TXD
P3.2/INT0
P3.3/INT1
P3.4/T0
P3.5/T1
P3.6/WR
P3.7/RD

AT89C51

27

39
38
37
36
35
34
33
32
21
22
23
24
25
26
27
28
10
11
12
13
14
15
16
17

16
2
7
1

9
10
15

IN1
IN2
EN1

EN2
IN3
IN4

VSS

GND

+12V

8
VS OUT1
OUT2

OUT3
GND OUT4

U2
3
6

+88.8

18

XTAL1

11
14

L293D

+88.8

+5V

U1
19

4.4 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.

5.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.

28

REFERENCES :
[1].www.avrfreaks.com, Microntrollers, Atmel,10[2]. septiembre-2001. [11] www.atmel.com
[3]. The 8051 Microcontroller and Embedded Systems Using Assembly and C By
Muhammad Ali Mazidi, Janice Gillispie Mazidi & Ro lin D. McKinlay
[5]. Atmel Corp. Makers of the AVR microcontroller
www.atmel.com
[6]. www.electronic projects.com
[7]. www.howstuffworks.com
[8]. Electrikindia.
[9]. EMBEDDED SYSTEM BY RAJ KAMAL

29

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