line robot follower
DESCRIPTION
ACKNOWLEDGEMENT We would first of all, We like to thanks Mr. Vishwas Kumar, Ms. Palak Aggarwal (Lecturer, Dept. of EE, JNU, Jaipur), for giving us the opportunity to work with this technology. He has been highly available and highly supportive during the project. We are highly inspired by his dedication to work, as he made continuous efforts to make this project successful. Working under him was a wonderful experience. We are also grateful to have an opportunity to work with Mr. Devendra Doda (STRANSCRIPT
ACKNOWLEDGEMENT
We would first of all, We like to thanks Mr. Vishwas Kumar, Ms. Palak Aggarwal (Lecturer,
Dept. of EE, JNU, Jaipur), for giving us the opportunity to work with this technology.
He has been highly available and highly supportive during the project. We are highly inspired
by his dedication to work, as he made continuous efforts to make this project successful.
Working under him was a wonderful experience.
We are also grateful to have an opportunity to work with Mr. Devendra Doda (Senior
Lecturer, Dept. of EE , JNU, Jaipur), who had kept us on our toes and guiding us at each
step. We learned not only the technical aspects but also the practical qualities of working as a
team.
Introduction:-
For my final project, I decided to make a line-follower robot. This simple
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 forward. A circuit inside takes an
input signal from two sensors and controls the speed of wheels‘ rotation. The control
is done in such a way that when a sensor senses a black line, the motor slows down or
even stops. Then the difference of rotation speed makes it possible to make turns. For
instance, in the figure on the right, if the sensor somehow senses a black line, the
wheel on that side slows down and the robot will make a right turn.
What is a line follower?
Line follower is a machine that can follow a path. The path can be visible like a black
line on a white surface (or vice-versa) or it can be invisible like a magnetic field.
Why build a line follower?
Sensing a line and maneuvering the robot to stay on course, while constantly
correcting wrong moves using feedback mechanism forms a simple yet effective
closed loop system. As a programmer you get an opportunity to ‗teach‘ the robot how
to follow the line thus giving it a human-like property of responding to stimuli.
Practical applications of a line follower: Automated cars running on roads with
embedded magnets; guidance system for industrial robots moving on shop floor etc.
Block Diagram:
Fig.1 Block diag. Of Track Follower Robot
1.2. DESCRIPTION OF BLOCK DIAGRAM
TRACK FOLLOWER
SENSOR:-We used Infrared Emitter-Sensor pair for sensing the track. When the
emitter passes over the white surface the light from it is reflected back to the sensor
whereas on black surface light doesn‘t reflect back and thus resistance of sensor goes
high which intern switches off the motor.
AMPLIFIER- In this we used NPN transistor BC548 as the amplifier circuit. It
amplifies the low intensity sensor signal and provides it to the input of the motor
driving circuit.
CALIBRATION CIRCUIT- A preset or variable resistor of value 500K is used to
adjust the sensitivity of the sensor.
MOTOR DRIVEN CIRCUIT- L293D is used as motor driving circuit which
responses accordingly to the low input signal provided by the amplifier circuit.
MOTOR-In this we used the DC MOTORS which are used to move the follower
ahead.
Circuit diagram
Fig. 2 Circuit Diagram of Track follower
Introduction to Track follower:
Track follower is a machine that can follow a path. The path can be visible like a
black line on a white surface (or vice-versa) or it can be invisible like a magnetic
field. For many TRUE robotics competitions, which require an autonomous vehicle, a
track-follower is a pre-requisite. And unbelievably, a line-follower can be constructed
without using any microprocessor/controller and is a mere game of two sensors, a
comparator IC, and DC motors to move your vehicle.
The Circuit explanation:-
The robot uses a combination of IR Photo diode and IR-LEDs to sense the presence to
a line. An IR Photo diode is a resistor whose resistance is proportional to the light
falling on it- greater the light, lesser the resistance and visa-versa. The basic principle
underlying this project is that objects light in colour radiate the light falling on them
while dark coloured objects don‘t. So when the sensors are above the black line the
light emitted by the IR- LED is not radiated by the floor, hence the resistance of the
Photo-diode increases. The opposite happens when the robot back on the white
surface.
In our robot the IR Photo diode is used part of a voltage divider circuit. The circuit
diagram of the voltage divider used in this project is given below
The resistor whose value is 500K is a potentiometer. A potentiometer (pot or preset)
whose resistance can be changed. In our project, we will be using 500k presets, that
is, we will use presets whose resistance can be changed from 0K to 500K.
When the robot is on white surface the
light emitted by the IR LEDs fall on the
IR Photo diode and decreases its
resistance. This in turn reduces the
voltage at Vout. When the robot is on
the black line, the light emitted by he
IR- LEDs does not reach the IR Photo
diode, hence its resistance increases.
This in turn increases the voltage at Vout. Fig. 3 Sensor Circuit
During both the cases it is necessary to adjust the 500K preset in such a way that, when
the robot is on white surface, voltage at Vout is <0.8V (so that the voltage at the emitter
of the transistor is LOW) and when the sensor is on the black line the voltage is >0.8V
(so that the voltage at the emitter of the transistor is HIGH). For controlling the two DC
motors, I have used the L293D motor driver. The reason I used this is that it has high
noise immunity (that is, it considers voltages up to 1.7V as LOW), perfect for a robot
which deals with analog signals.
The pins 4, 5, 12 and 13 are connected to ground. Pin 8 is the motor power supply pin
and is connected to Vcc (9V) along with Pins 1, 16 (the two enable pins) and Pin 9.
The left and right motors are connected to Pins 3, 6 and Pins 14, 11 respectively. Pin 2
(Input A), Pin 7 (Input B) and Pin 15 (Input A), Pin 10(Input B) are the input pins for
controlling the left and right motor respectively. The truth table for controlling the
motors is given below
Fig.4 Sensors mounted on Robot.
Fig.5 schematic of track follower on PCB
WORKING OF THE CIRCUIT:
In both the sides of the robot two sensors are used to sense the presence the line. The
output of both the sensors of each side are connected together and connected to an
LED. So that, the LED glows even when one of the sensors detects the line. The
output of the left sensor is connected to Input A (Pin 2) of the left motor and the right
sensor to Input A (Pin 15) of the right motor. When the robot is on white surface only
one (Pin 7 and 10) input pin in each channel is high. The Pins 2 and 15 are low as the
sensors are on white surface. Hence this makes the robot move forward. When the left
sensor is on the line, Pin 2 is high. But Pin 7 is also high. Hence the left motor is
switched off as both the inputs are HIGH (refer to the truth table above).But the right
motor is still turning forward. This brings the robot Back on the white surface.
Similarly when the right sensors are on the line, the right motor is switched off until
the robot is back on the white surface.
This circuit works fine for black line following and using the robot as a photovore and
obstacle avoider, for following white line and for using the robot as a photophobe,
there is a slight change in the circuit. The left sensor output is connected to Pin 7 and
right sensor output to Pin 10. Pins 2 and 15 remain unconnected.
The rest of the circuit remains unchanged. When the robot is on black surface (when
following white lines), the input pins 2 and 15 are high. This makes the motors turn
forward. When the left sensors are on the line the output goes low and stops the motor
until the sensors are back on the black surface. Similarly, when the right sensors are
on the line, the right motor is stopped.
Fig.6 Track Follower
Fig. 7 Views of Line follower/Track Follower
2. Description of Components:
2.1. LIST OF COMPONENT:
2.2. Components Description:
2.2.1. Capacitor:
A capacitor or condenser is a passive electronic component consisting of a pair of
conductors separated by a dielectric. Capacitors store electric charge in them. They
are used with resistors in timing circuits because it
takes time for a capacitor to fill with charge. They are
used to smoothly vary DC supplies by acting as a
reservoir of charge. They are also used in filter
circuits because capacitors easily pass AC (changing)
signals but they block DC (constant) signals. An
ideal capacitor is characterized by a single constant
value, capacitance, which is measured in farads.
Fig.8 Capacitor
This are of different types which includes- multilayer ceramic, ceramic disc,
multilayer polyester film, tubular ceramic, polystyrene, metalized polyester film,
aluminium electrolytic.
Coding:- Value of capacitor are read from their body. An electrolytic capacitor
contains its value along with unit as well as voltage specification. Whereas in disk
type if two digits are present, these are read as Pico-Farads. An example: 47 printed
on a small disk can be assumed to be 47 Pico-Farads. But, in case three digits are
present the first two are the 1st and 2nd significant digits and the third is a multiplier
code. Most of the time the last digit tells us how many zeros to write after the first two
digits.
2.2.2. Resistor:
A resistor is a two-terminal electronic component that produces a voltage across
its terminals that is proportional to the electric current through it in accordance with
Ohm's law:
V = IR
Resistors are elements of electrical networks and electronic circuits and are ubiquitous
in most electronic equipment. Practical resistors can be made of various compounds
and films, as well as resistance wire (wire made of a high-resistivity alloy, such as
nickel-chrome).
T
h
e
p
Fig. 9 Resistor
The primary characteristics of a resistor are the resistance, the tolerance, the
maximum working voltage and the power rating. Other characteristics include
temperature coefficient, noise, and inductance. Less well-known is critical resistance,
the value below which power dissipation limits the maximum permitted current, and
above which the limit is applied voltage. Critical resistance is determined by the
design, materials and dimensions of the resistor.
Resistors can be integrated into hybrid and printed circuits, as well as integrated
circuits. Size, and position of leads (or terminals), are relevant to equipment
designers; resistors must be physically large enough not to overheat when dissipating
their power.
Theory of operation:
The behaviour of an ideal resistor is dictated by the relationship specified in Ohm's
law:
V=I*R
Ohm's law states that the voltage (V) across a resistor is proportional to the
current(I)through it where the constant of proportionality is the resistance (R).
Equivalently, Ohm's law can be stated:
This formulation of Ohm's law states that, when a voltage (V) is maintained across a
resistance (R), a current (I) will flow through the resistance.
This formulation is often used in practice. For example, if V is 12 volts and R is
400 ohms, a current of 12 / 400 = 0.03 amperes will flow through the resistance R.
2.2.3. Transistor
A Transistor is a semiconductor which is a fundamental component in almost all
electronic devices. Transistors have many uses including switching, voltage/current regulation, and
amplification - all of which are useful in renewable energy applications.
A transistor controls a large electrical output signal with changes to a small input signal. Since a
large amount of current can be controlled by a small amount of current, a transistor acts as an
amplifier.
The most common type of transistor is a bipolar junction transistor. This is made up of three layers of
a semiconductor material in a sandwich. In one configuration the outer two layers have extra
electrons, and the middle layer has electrons missing (holes). In the other configuration the two outer
layers have the holes and the middle layer has the extra electrons.
.
Fig10. Transistor Symbol
Fig.11 Transistor
2.2.4. LED(Light Emitting Diode):
LED falls within the family of P-N junction devices. The light emitting diode (LED)
is a diode that will give off visible light when it is energized. In any forward biased P-
N junction there is, with in the structure and primarily close to the junction, a
recombination of hole and electrons. This recombination requires that the energy
possessed by the unbound free electron be transferred to another state. The process of
giving off light by applying an electrical source is called electroluminescence.
LED is a component used for indication. All the functions being carried out are
displayed by led .The LED is diode which glows when the current is being flown
through it in forward bias condition. The LEDs are available in the round shell and
also in the flat shells. The positive leg is longer than negative leg.
Fig. 12 LED
Connecting and soldering
LEDs must be connected the correct way round, the diagram may be
labelled a or + for anode and k or - for cathode (yes, it really is k, not c, for cathode!).
The cathode is the short lead and there may be a slight flat on the body of round
LEDs. If you can see inside the LED the cathode is the larger electrode (but this is not
an official identification method).
LEDs can be damaged by heat when soldering, but the risk is small unless you are
very slow. No special precautions are needed for soldering most LEDs.
2.2.5. L293D IC MOTOR DRIVER
Features:
Wide Supply-Voltage Range: 4.5 V to 36 V
Separate Input-Logic Supply
Internal ESD Protection
Thermal Shutdown
High-Noise-Immunity Inputs
Functionally Similar to SGS L293 and SGS L293D
Output Current 1 A Per Channel(600mA for L293D)
Peak Output Current 2 A Per Channel (1.2 A for L293D)
Output Clamp Diodes for Inductive Transient Suppression (L293D)
Fig. 13 L293d IC Motor Driver Pin Diagram
The L293 and L293D are quadruple high-current half-H drivers. The L293 is
designed to provide bidirectional drive currents of up to 1 A at voltages from 4.5 V to
36 V. The L293D is designed to provide bidirectional drive currents of up to 600-mA
at voltages from 4.5 V to 36 V. Both devices are designed to drive inductive loads
such as relays, solenoids, dc and bipolar stepping motors, as well as other high-
current/high-voltage loads in positive-supply applications. All inputs are TTL
compatible. Each output is a complete totem-pole drive circuit, with a Darlington
transistor sink and a pseudo-Darlington source. Drivers are enabled in pairs, with
drivers 1 and 2 enabled by 1,2EN and drivers 3 and 4 enabled by 3,4EN.When an
enable input is high, the associated drivers are enabled, and their outputs are active
and in phase with their inputs. When the enable input is low, those drivers are
disabled, and their outputs are off and in the high-impedance state. With the proper
data inputs, each pair of drivers forms a full-H (or bridge) reversible drive suitable for
solenoid or motor applications.
2.2.6. IR PHOTO DIODE:
A photodiode is a type of photo detector capable of converting light into either
current or voltage, depending upon the mode of operation. The term photodiode can
be broadly defined to include even solar batteries, but it usually refers to sensors used
to detect the intensity of light IR Photo diodes are semiconductor devices responsive
to high energy particles and photons. Photodiodes operate by absorption of charged
particles and generate a flow of current in an external circuit, proportional to the
incident power. Photodiodes can be used to detect the presence or absence of minute
quantities of light and can be calibrated for extremely accurate measurements from
intensities below 1pW/cm2.
This IR sensor circuit is designed using 1 IR LED and 1 Photodiode. This circuit
works on the reflection criteria. IR LED and Photodiode is placed adjacent to each
other. When no IR light falls on the IR Photo diode the resistance of the diode falls
in the range ohm Mega ohms or approximately infinity
When any reflecting surface (White surface) comes near to IR LED and IR Photo
diode pair the reflected light of IR LED falls on the photodiode which rapidly
decreases the resistance of the Photodiode and photodiode starts conducting
Features of photodiode
1. Excellent linearity with respect to incident light
2. Low noise
3. Wide spectral response
4. Mechanically rugged
5. Compact and lightweight
6. Long life
Fig.14 IR Pair
Fig. 15 Working of IR pair
APPLICATION:
1. Photodiodes are used in consumer electronics devices such as compact
disc players, smoke detectors, and the receivers for remote controls
in VCRs and televisions.
2. They are also widely used in various medical applications, such as detectors
for computed tomography (coupled with scintillators) or instruments to analyse
samples (immunoassay). They are also used in pulse oximeters.
2.2.7. DC MOTOR:
A DC motor is an electric motor that runs on direct current (DC) electricity.
A direct current (DC) motor is a fairly simple electric motor that uses electricity and
a magnetic field to produce torque, which turns the motor. At its most simple,
a DC motor requires two magnets of opposite polarity and an electric coil, which acts
as an electromagnet. The repellent and attractive electromagnetic forces of the
magnets provide the torque that causes the DC motor to turn.
The most common DC motor types are the brushed and brushless types, which use
internal and external commutation respectively to create an oscillating AC current
from the DC source—so they are not purely DC machines in a strict sense.
The brushed DC motor generates torque directly from DC power supplied to the
motor by using internal commutation, stationary permanent magnets, and rotating
electrical magnets. .It works on the principle of Lorentz force , which states that any
current carrying conductor placed within an external magnetic field experiences a
torque or force known as Lorentz force. Advantages of a brushed DC motor include
low initial cost, high reliability, and simple control of motor speed. Disadvantages are
high maintenance and low life-span for high intensity uses.
Brushless DC motors use a rotating permanent magnet in the rotor, and stationary
electrical magnets on the motor housing. A motor controller converts DC to AC. This
design is simpler than that of brushed motors because it eliminates the complication
of transferring power from outside the motor to the spinning rotor. Advantages of
brushless motors include long life span, little or no maintenance, and high efficiency.
Disadvantages include high initial cost, and more complicated motor speed
controllers.
DC motors are used for a variety of purposes, including electric razors, electric
car windows, and remote control cars. The simple design and reliability of
a DC motor makes it a good choice for many different uses, as well as a fascinating
way to study the effects of magnetic fields.
Fig. 16 DC Motor
CONCLUSION
The Track Follower robot is one of the outcomes of implementation of with
microcontroller on single board. This robot can be autonomous if it is run by 4 AA
batteries. There are certain advantages of this robot. They are as:
Increased productivity, safety, efficiency, quality of products
Can work in hazardous environments, no need for support
Need no environmental comforts
Have repeatable precision at all times
Can be more accurate than humans
Have many capabilities beyond those of humans
Can process multiple stimuli/tasks simultaneously.
A robot can work without sleep. So it can work 24/7/365
Apart from advantages there are some disadvantages too. They are as follows:
Robots take the place of many humans in places like factories. So the people have
to find new jobs or be retrained. So a MAJOR disadvantage is that the robots take
the place of humans in several situations.
Another disadvantage is that there is quite a high initial cost for the robot and the
software and equipment that you need to use with the robot
REFERENCE
1. Conceptual Details of Track Follower: Advances in Robotics: FIRA Robo
World Congress 2009, Incheon, - Page 69 Jong-Hwan Kim, Shuzhi Sam Ge,
Prahlad Vadakkepat - 2009 - 322 pages
2. Concept of Line follower Robot : Evolutionary swarm robotics: evolving self-
organising behaviours ... - Page 164 Vito Trianni - 2008 - 189 pages
3. www.projectdesignline.com/howto/207800773
4. www.electronicsforu.com/electronicsforu/lab/ad.asp?url=/EFYLinux/circuit/Augu
st2007/CI-01_Aug07.pdf&title=Mobile%20Detector
5. Simple Line Follower. www.societyofrobots.com/member_tutorials/node/62
6. Kuchta, R.; Stefan, P.; Barton, Z.; Vrba, R.; Sveda, M, ―Wireless temperature data
logger‖, ‗Sensors and the International Conference on new Techniques in RF
Research, 2005 Asian Conference‘ on 5-7 Sept. 2005 Page(s):208 – 212.