Line following is one of the most important aspects of Robotics. A Line Follower Robot is an autonomous robot which is able to follow either a black or white line that is drawn on the surface consisting of a contrasting color. It is designed to move automatically and follow the made plot line. The path can be visible like a black line on a white surface or it can be invisible like a magnetic field. It will move in a particular direction Specified by the user and avoids the obstacle which is coming in the path. Autonomous Intelligent Robots are robot that can perform desired tasks in unstructured environments without continuous human guidance. It is an integrated design from the knowledge of Mechanical, Electrical, and Computer Engineering. LDR sensors based line follower robot design and Fabrication procedure which always direct along the black mark on the white surface. The robot uses several sensors to identify the line thus assisting the bot to stay on the track. The robot is driven by DC motors to control the movements of the wheels.

1. Journal for Research | Volume 04 | Issue 01 | March 2018
ISSN: 2395-7549
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Line Follower Robot
Abhijit G. Kalbande Miss. Shraddha O. Koche
Assistant Professor & Guide U.G. Student
Department of Electronics & Telecommunication
Engineering
Department of Electronics & Telecommunication
Engineering
PRMCEAM, Badnera, Amravati, India PRMCEAM, Badnera, Amravati, India
Abstract
Line following is one of the most important aspects of Robotics. A Line Follower Robot is an autonomous robot which is able to
follow either a black or white line that is drawn on the surface consisting of a contrasting color. It is designed to move
automatically and follow the made plot line. The path can be visible like a black line on a white surface or it can be invisible like
a magnetic field. It will move in a particular direction Specified by the user and avoids the obstacle which is coming in the path.
Autonomous Intelligent Robots are robot that can perform desired tasks in unstructured environments without continuous human
guidance. It is an integrated design from the knowledge of Mechanical, Electrical, and Computer Engineering. LDR sensors
based line follower robot design and Fabrication procedure which always direct along the black mark on the white surface. The
robot uses several sensors to identify the line thus assisting the bot to stay on the track. The robot is driven by DC motors to
control the movements of the wheels.
Keywords: Line Follower, Robot, IR Sensors, DC Motor, Motor Driver
_______________________________________________________________________________________________________
I. INTRODUCTION
What is a Line Follower Robot
The line follower robot is designed to be able to follow a black line on the ground without getting off the line too much. The
Robot has two sensors installed underneath the front part of the body, and two DC motors drive wheels moving forwards. A
circuit inside takes and input signal from two sensors and controls the speed of wheels rotation. The control is done in such a
way that when a sensors senses a black line, the motor slows down or even stops. Then the difference of rotation speed makes it
possible to makes turns. For instance, in the on the right, if the sensors somehow senses a black line, the wheel on that side slows
down and robot will make a right turn.
How to Sense a Black Line
The sensors used for the are Reflective Object Sensors, OPB710F that are already ready in the Electronic Lab. The single sensors
consists of an infrared emitting diode and a NPN Darlington phototransistor. When a light emitted from the diode is reflected off
an object and back into the phototransistor, output current is produced, depending on the amount of infrared light, which triggers
the base current of the phototransistor. In my case, the amount of light reflected off a black line is much less than of a white
background, so we detect the black line somehow by measuring the current. (This current is converted to voltage.)
How to Control a DC Motors
Instead of applying a constant voltage across a DC motors, we repeat switching on and off the motors with a fixed voltage
applied to the motors. This is done by sending a trains of PWM pulses to a power MOSFET in order to turn it on and off. Then
the motors sees the average voltage while it depends on duty cycle of PWM pulses. The speed of rotation is proportion to this
average voltage. By PWM method, it’s easier to control the DC motors than by directly controlling the voltage across it. All we
have to do is to modulate pulse width, in order words, duty cycle. Also, a power MOSFET consumes only negligible power in
switching.
II. BASIC OPERATION
The basic operations of line follower are follows:
1) Capture line position with optical sensors mounted at front end of the robot. For this a combination of IR LED’s and
phototransistors called an optical coupler has been used. Requirement for line sensing process are high resolution and high
robustness.
2) Steer robot requires steering mechanism for tracking. Two motors governing wheel motion are used for achieving this task.

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Fig. 2.1: Basic Block Diagram Line Follower
III. INPUT SYSTEM
IR reflective sensors have one emitter (IR LED) and one receiver phototransister or photo diode. If we have white surface it
reflects the light and it will sensed by the receiver, similarly if we have black surface it absorbs the light and receiver cannot
sense light.
Fig. 3.1. White Surface Reflects Light & Black Surface Absorb It
Photo diode has property that if IR light fall on its electrical resistance comes down (i.e its comes down from 150kohm to
10kohm if no noise is present). For sense the change in resistance we use voltage divider circuit (as shown in fig).
IR Sensor
An Infra-red sensors detects Infra-red light/white light from a particular object/line and then converts light energy to electrical
energy. An IR sensors pair consists of an emitter and a detector. The emitter is blue in color and the detector can be gray black or
white in colour.
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 phototransistors acts as a transistor with the base voltage determined by the amount of light
hitting the transistor. Hences it acts as a variables currents sources. Greater amount of IR light cause greater currents to flow
throught the collector emitter leads. The variable current traveling through the resistors causes a voltage drop in the the pull up
resistor. The voltage is measured as the output of the device.
IR Detector
An infrared detector is a photodetector.it detects ir energy emittesd by the emitter and converted it into electrical energy.the main
principle involves in the conversion of light energy to electrical energy is photoelectric effect.the output is taken at negative
terminal of IR detector.the output can be taken to amicrocontroller either to its analog to digital converter or LM335 can be used
as comparator.

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IV. OUTPUT SYSTEM
Moter Driver
Motor driver is a current enhancing device; it can also be act as Switching Device. Thus,after inserting motor driver among
themotor and microcontroller. Motor driver taking the input signals from microcontroller and generate corresponding output for
motor.
ICL293D
This is a motor driver IC that can drive two motor simultaneously. Supply voltage (Vss) is the Voltage at which we wish to drive
the motor. Generally, 6V for dc motor and 6 to 12V for gear motor are used, depending upon the rating of the motor.Logical
Supply Voltage deciding what value of input voltage should be consideredas high or low .So if we set Logical Supply Voltage
equals to +5V, then -0.3V to 1.5V will be considered as Input Low Voltage and 2.3V to 5V is taken into consider as Input High
Voltage. L293D has 2 Channels .One channel is used for one motor.
 Channel 1-Pin1to8
 Channel 2-Pin9to16
Enable Pin is use to enable or to make a channel active .Enable pin is also called as Chip Inhibit Pin. All Input (PinNo. 2,
7,10and 15) of L293D IC is the output from microcontroller (ATmeg32). E.g.-We connected (Pin No. 2, 7, 10 and 15) of L293D
IC to (Pin No. 14, 15, 16and 17) of ATmega32 respectively in our robots, because on pin 15and 16 ofATmega32we can generate
PWM. All Output (Pin No. 3, 6,11and 14) of L293D IC goes to the input of Right and Left motor.
Fig. 4.1: L293D
V. WORKING
There are three different cases in working of line follower robot
1) Straight direction
2) Right direction
3) Left direction
Straight Direction
We can expect our robot to move in straight direction when the middle sensor response is low and remaining two sensor
response is high. i.e according to our arangment the middle sensor will always be on the line and as the line is black in color it
will not reflect the emitted radiation black and response of the sensor will low and the response of the remaing two sensor will be
high as they will be on the bright surface.
Right Direction
When a right curve is found on the line the responses will change i.e the response of the first sensors which is to the right will
becomes low as that sensors will be facing the black line and the reaming sensors response will be high. We this data is
achiveved 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 sensors becomes low. Then the same process repeats again.

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Left Direction
When a left curve is found on the line the response of the left most sensors will be changed from high to low as the sensors will
now face the black or the dark surface. Then the control of wheel changes. i.e by holding the left wheel and allowing the right
wheel to move freely until the middle sensors 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.
VI. ADVANTAGES & DISADVANTAGES
Advantages
1) Robot movement is automatic.
2) Fit and forget system.
3) Used for long distance application.
4) Defense applications.
5) Simplicity of building.
Disadvantage
1) LFR follower a black line about 1or 2 inches in width on a white surface.
2) Slow speed and instability on different line thickness or hard angles.
VII.CONCLUSION
The line follower robot work successfully to the track on the black line. Above the white surface there are some black line in
different direction the robot still good enough to sense the line and follow the track. Also the robot capable to carry some load
likely 500gm
VIII. FUTURE SCOPE
1) Software control of the line type (dark or light) to make automatic detection possible.
2) “Obstacle detecting sensors” to avoide physical obstacles and continue on the line.
3) Distance sensing and position logging and transmission.
4) Smarter Version of line follower are used to deliver mails within office building and deliver medications in a hospital.
5) This technology has been suggested for running buses and other mass transit system and may end up as a part of
autonomous cars navigating the freeway.
REFERENCES
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Engineering TCCEE '09, vol.2, pp.585-590,Dec.2009.
[2] PriyankPatil,"AVR Line Following Robot,” Department of Information Technology K. 1. Somaiya College of Engineering Mumbai, India. Mar 5, 2010.
[3] Dean A. Pomerleau; Jay Gowdy; Charles E. Thorpe, “Combining Artificial Neural Networks and Symbolic Processing for Autonomous Robot Guidance,"
Engng Applic. Artif. Intell. Vol. 4, No. 4, pp. 279-285, 1991.
[4] L1U Shi-Cai,L1U Guang-Jun, "Formation Control of Mobile Robots with Active Obstacle Avoidance," Acta Automatica Sinica, Vol. 33, No. 5,
2007.
[5] YANG Tian-Tian; L1U Zhi-Yuan; CHEN Hong; PEl Run, "Formation Control and Obstacle Avoidance for Multiple Mobile Robots," Acta
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