Report Mini

8/12/2019 Report Mini

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ABSTRACT

Line following robot is a robo car that can follow a path. The path can be visible like a

white line on the black surface (or vice-verse). As a result of this line following property it has

many applications in future and now itself.

Line following robot with pick and placement capabilities are commonly used in

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

location and place them on desired locations.

Basically,a line-following robot is 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 manoeuvre the robot to stay on course while

constantly correcting the wrong moves using feedback mechanism,thus forming 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.

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 white line, the motor slows down or even stops. Then the difference of rotation speed

makes it possible to make turns.


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CONTENTS

1.INTRODUCTION................................................................................04

2.BLOCK DIAGRAM............................................................................05

3.BLOCK DIAGRAM EXPLANATION..............................................06

4.CIRCUIT DIAGRAM..........................................................................07

5.COMPONENT STUDY.......................................................................08

6.CIRCUIT DESCRIPTION...................................................................15

7.WORKING...........................................................................................17

8.SOFTWARE SECTION.......................................................................19

9.HARDWARE SECTION.....................................................................22

10.CONSTRUCTION.............................................................................26

11.PCB LAYOUT...................................................................................27

12.COMPONENT LAYOUT..................................................................28

13.LIST OF TOOLS & EQUIPMENTS REQUIRED............................29

14.COMPENENTS REQUIRED.............................................................30

15.PRECAUTIONS..................................................................................32

16.APPLICATIONS.................................................................................33

17.LIMITATIONS....................................................................................34

18.CONCLUSION....................................................................................35

19.REFERENCE........................................................................................36

20.APPENDIX...37


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2.BLOCK DIAGRAM


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Bread Board Circuit
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3.BLOCK DIAGRAM EXPLANATION

Fig.1 show the block diagram of automated line following robot. It consist of mainly four

parts: two sensors,two comparators,one decision making device and two motor drivers. The

robot is built using 555 timer, motor driver L293D, phototransistor and a few discrete

components. In the circuit, the sensor are used to detect the white strip on a black background.

The sensor output is fed to the microcontroller, which takes the decision and gives appropriate

command to motor driver L293D so as to move the motor accordingly

1. Sensor: The sensor senses the light reflected from the surface and feeds the output to thecomparator. When the sensor is above the white background the light falling on it from

the source reflects to the sensor, and when the sensor is above the black background the

light from the source doesnt reflect to it. The sensor senses the reflected light to give an

output, which is fed to the comparator.

2. Comparator: The comparator compares the analogue inputs from sensors with a fixedreference voltage. If this voltage is greater than thereference voltage the comparator

outputs a low voltage, and if it smaller the comparator generates a high voltage that acts

as input for decision-making device.

3. Motor driver:The current supplied by the microcontroller to drive the motor is small.Therefore a motor driver ic is used. It provides sufficent current to drive the motor

4. 555 Timer IC:The 555 timer IC is anintegrated circuit (chip) used in a variety oftimer,pulse generation, andoscillator applications. The 555 can be used to provide time delays,

as anoscillator,and as aflip-flop element.Derivatives provide up to four timing circuits

in one package.
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5.COMPONENT STUDY

555 TIMER IC

The 555 timer IC is anintegrated circuit (chip) used in a variety oftimer,pulse generation,

andoscillator applications. The 555 can be used to provide time delays, as anoscillator,and as

aflip-flop element.Derivatives provide up to four timing circuits in one package.Introduced in

1971 bySignetics,the 555 is still in widespread use due to its ease of use, low price, and

stability. It is now made by many companies in the originalbipolar and also in low-

powerCMOS types. As of 2003, it was estimated that 1 billion units are manufactured every

year.

1.1 DESIGNThe IC was designed in 1971 byHans Camenzind under contract toSignetics,which was lateracquired byPhilips (nowNXP).Depending on the manufacturer, the standard 555 package

includes 25transistors,2diodes and 15resistors on asilicon chip installed in an 8-pin mini dual-

in-line package (DIP-8).[2]

Variants available include the 556 (a 14-pin DIP combining two 555s

on one chip), and the two 558 & 559s (both a 16-pin DIP combining four slightly modified 555s

with DIS & THR connected internally, and TR is falling edge sensitive instead of level

sensitive).

The NE555 parts were commercial temperature range, 0 C to +70 C, and the SE555 part

number designated the military temperature range, 55 C to +125 C. These were available in

both high-reliability metal can (T package) and inexpensive epoxy plastic (V package) packages.

Thus the full part numbers were NE555V, NE555T, SE555V, and SE555T. It has beenhypothesized that the 555 got its name from the three 5kresistors used within, but Hans

Camenzind has stated that the number was arbitrary.

Low-power versions of the 555 are also available, such as the 7555 and CMOS TLC555. The

7555 is designed to cause less supply noise than the classic 555 and the manufacturer claims that

it usually does not require a "control" capacitor and in many cases does not require adecoupling

capacitor on the power supply. Such a practice should nevertheless be avoided, because noise
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produced by the timer or variation in power supply voltage might interfere with other parts of a

circuit or influence its threshold voltages

1.2 PIN DIAGRAM

Figure 1.1: Pin diagram of IC NE/SE 555

1.3 PIN DISCRIPTION1Pin 1: Grounded Terminal:All the voltages are measured with respect to this terminal.

2 Pin 2: Trigger Terminal:This pin is an inverting input to a comparator that is responsiblefor transition offlip-flopfrom set to reset. The output of the timer depends on the amplitude

of the external trigger pulse applied to this pin.

3 Pin 3: Output Terminal:Output of the timer is available at this pin. There are two ways inwhich a load can be connected to the output terminal either between pin 3 and ground pin

(pin 1) or between pin 3 and supply pin (pin 8). The load connected between pin 3 and

ground supply pin is called the normally on loadand that connected between pin 3 and

ground pin is called the normally off load.4 Pin 4: Reset Terminal:To disable or reset the timer a negative pulse is applied to this pin

due to which it is referred to as reset terminal. When this pin is not to be used for reset

purpose, it should be connected to + VCCto avoid any possibility of false triggering.

5 Pin 5: Control Voltage Terminal:The function of this terminal is to control the thresholdand trigger levels. Thus either the external voltage or a pot connected to this pin determines

the pulse width of the output waveform. The external voltage applied tothis pin can also be
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used to modulate the output waveform. When this pin is not used, it should be connected to

ground through a 0.01 micro Farad to avoid any noise problem.

6 Pin 6: Threshold Terminal: This is the non-inverting input terminal of comparator 1,which compares the voltage applied to the terminal with a reference voltage of 2/3 VCC. The

amplitude of voltage applied to this terminal is responsible for the set state of flip-flop.7 Pin 7 : Discharge Terminal: This pin is connected internally to the collector of transistor

and mostly a capacitor is connected between this terminal and ground. It is called discharge

terminal because when transistor saturates, capacitor discharges through the transistor. When

the transistor is cut-off, the capacitor charges at a rate determined by the external resistor

and capacitor.

8 Pin 8: Supply Terminal: A supply voltage of + 5 V to + 18 V is applied to this terminalwith respect to ground (pin 1).

1.4 MODES OF OPERATION

The 555 has three operating modes:

Monostable mode: In this mode, the 555 functions as a "one-shot" pulse generator.Applications include timers, missing pulse detection, bouncefree switches, touch switches,

frequency divider, capacitance measurement,pulse-width modulation (PWM) and so on.

Astable (free-running) mode: The 555 can operate as anoscillator.Uses includeLED andlamp flashers, pulse generation, logic clocks, tone generation, security alarms,pulse position

modulation and so on. The 555 can be used as a simpleADC,converting an analog value to

a pulse length. E.g. selecting athermistor as timing resistor allows the use of the 555 in a

temperature sensor: the period of the output pulse is determined by the temperature. The useof a microprocessor based circuit can then convert the pulse period to temperature, linearize

it and even provide calibration means.

Bistablemode orSchmitt trigger:The 555 can operate as aflip-flop,if the DIS pin is notconnected and no capacitor is used. Uses include bounce-free latched switches.

1.4.1 MONOSTABLE MODE

In the monostable mode, the 555 timer acts as a "one-shot" pulse generator. The pulse begins

when the 555 timer receives a signal at the trigger input that falls below a third of the voltage

supply. The width of the output pulse is determined by the time constant of an RC network,

which consists of acapacitor (C) and aresistor (R). The output pulse ends when the voltage on

the capacitor equals 2/3 of the supply voltage. The output pulse width can be lengthened or

shortened to the need of the specific application by adjusting the values of R and C.
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FIGURE 1.2 The relationships of the trigger signal, the

voltage on C and the pulse width in monostable mode

The output pulse width of time t, which is the time it takes to charge C to 2/3 of the supply

voltage, is given by

Where t is in seconds, R is inohms and C is infarads.

While using the timer IC in monostable mode, the main disadvantage is that the time spanbetween any two triggering pulses must be greater than the RC time constant.

FIGURE1.3 Schematic of a 555 in monostable mode
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1.4.2 BISTABLE MODE

In bistable mode, the 555 timer acts as a basic flip-flop. The trigger and reset inputs (pins 2 and 4

respectively on a 555) are held high viaPull-up resistors while the threshold input (pin 6) issimply grounded. Thus configured, pulling the trigger momentarily to ground acts as a 'set' and

transitions the output pin (pin 3) to Vcc (high state). Pulling the reset input to ground acts as a

'reset' and transitions the output pin to ground (low state). No capacitors are required in a bistable

configuration. Pin 5 (control) is connected to ground via a small-value capacitor (usually 0.01 to

0.1 uF); pin 7 (discharge) is left floating.

FIGURE 1.4 Schematic of a 555 in bistable mode

1.4.2 BISTABLE MODE

In astable mode, the 555 timer puts out a continuous stream of rectangular pulses having a

specified frequency. Resistor R1is connected between VCCand the discharge pin (pin 7) and

another resistor (R2) is connected between the discharge pin (pin 7), and the trigger (pin 2) and

threshold (pin 6) pins that share a common node. Hence the capacitor is charged through R1and

R2, and discharged only through R2, since pin 7 has low impedance to ground during output low

intervals of the cycle, therefore discharging the capacitor.

In the astable mode, the frequency of the pulse stream depends on the values of R1, R2and C:

[7]

The high time from each pulse is given by:

and the low time from each pulse is given by:
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where R1and R2are the values of the resistors inohms and C is the value of the

capacitor infarads.

The power capability of R1must be greater than .

FIGURE1.5 Standard 555 astable circuit

Particularly with bipolar 555s, low values of R1 must be avoided so that the output stays

saturated near zero volts during discharge, as assumed by the above equation. Otherwise the

output low time will be greater than calculated above. It should be noted that the first cycle will

take appreciably longer than the calculated time, as the capacitor must charge from 0V to 2/3 of

VCCfrom power-up, but only from 1/3 of VCCto 2/3 of VCCon subsequent cycles.

To achieve aduty cycleof less than 50% is to use a small diode (that is fast enough for theapplication) in parallel with R2(instead of placing it on pin 7), with the cathode on the capacitor

side. This bypasses R2during the high part of the cycle so that the high interval depends

approximately only on R1and C. The presence of the diode is a voltage drop that slows charging

on the capacitor so that the high time is longer than the expected and often-cited ln(2)*R1C =

0.693 R1C. The low time will be the same as without the diode as shown above. With a diode,

the high time is

whereVdiode

is when the diode has a current of 1/2 of Vcc

/R1which can be determined from

its datasheet or by testing. As an extreme example, when Vcc= 5 and Vdiode= 0.7, high time =

1.00 R1C which is 45% longer than the "expected" 0.693 R1C. At the other extreme, when

Vcc= 15 and Vdiode= 0.3, the high time = 0.725 R1C which is closer to the expected 0.693

R1C. The equation reduces to the expected 0.693 R1C if Vdiode= 0.

The operation of RESET in this mode is not well defined, some manufacturers' parts will

hold the output state to what it was when RESET is taken low, others will send the output

either high or low.
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5.2 Phototransistor

We uses L14F1 phototransistor as the sensors in our circuit. The standard symbol of

a phototransistor, which can be regarded as a conventional transistor housed in a case that

enables its semiconductor junctions to be exposed to external light. The device is normally used

with its base open circuit, in either of the configurations shown in fig. 5.9.2, and functions as

follows.

Fig. 5.9.1Phototransistor symbol.

In practice, the collector and emitter current of the transistor are virtually identical and,

since the base is open circuit, the device is not subjected to significant negative feedback. The

sensitivity of a phototransistor is typically one hundred times greater than that of a photodiode,

but is useful maximum operating frequency (a few hundred kilohertz) is


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proportionally lower than that of a photodiode by using only its base and collector terminals

and ignoring the emitter, as shown in fig.5.10.2. Phototransistors are solid-state light detectors

with internal gain that are used to provide analog or digital signals. They detect visible,

ultraviolet and near-infrared light from a variety of sources and are more

sensitive than photodiodes, semiconductor devices that require a pre-amplifier. Phototransistors

feed a photocurrent output into the base of a small signal transistor. For each illumination level,

the area of the exposed collector-base junction and the DC current gain of the transistor define

the output.

Fig. 5.9.2. Phototransistor used in circuit

The base current from the incident photons is amplified by the gain of the transistor, resulting

in current gains that range from hundreds to several thousands. Response time is a function of

the capacitance of the collector-base junction and the value of the load resistance.Photodarlingtons, a common type of phototransistor, have two stages of gain and can provide net

gains greater than 100,000. Because of their ease of use, low cost and compatibility with

transistor-transistor logic (TTL), phototransistors are often used in applications where more than

several hundred nano watts (nW) of optical power are available. Selecting


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phototransistors requires an analysis of performance specifications. Collector current is the

total amount of current that flows into the collector terminal. Collector dark current is the

amount of collector current for which there is no optical input. Typically, both collector current

and collector dark current are measured in milliamps (mA). Peak wavelength, the wavelength at

which phototransistors are most responsive, is measured in nanometers (nm). Rise time, the time

that elapses when a pulse waveform increases from 10% to 90% of its

maximum value, is expressed in nanoseconds (ns). Collector-emitter breakdown voltage is the

voltage at which phototransistors conduct a specified (nondestructive) current when biased in the

normal direction without optical or electrical inputs to the base.

3. CAPACITOR

A capacitor (originally known as a condenser) is apassivetwo-terminalelectrical

component used to storeenergyelectrostatically in anelectric field.The forms of practical

capacitors vary widely, but all contain at least twoelectrical conductors separated by

adielectric (insulator); for example, one common construction consists of metal foils separated

by a thin layer of insulating film. Capacitors are widely used as parts ofelectrical circuits in many

common electrical devices.

When there is apotential difference across the conductors, anelectric field develops across the

dielectric, causing positive charge to collect on one plate and negative charge on the other

plate.Energy is stored in the electrostatic field. An ideal capacitor is characterized by a single

constant value,capacitance.This is the ratio of theelectric charge on each conductor to the

potential difference between them. TheSI unit of capacitance is thefarad,which is equal to

onecoulombpervolt.
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FIGURE 3.1 SOME COMMON CAPACITORS

The capacitance is greatest when there is a narrow separation between large areas of conductor,hence capacitor conductors are often calledplates, referring to an early means of construction. In

practice, the dielectric between the plates passes a small amount ofleakage current and also has

an electric field strength limit, thebreakdown voltage.The conductors andleads introduce an

undesiredinductance andresistance.

Capacitors are widely used inelectronic circuits for blockingdirect current while

allowingalternating current to pass. Inanalog filter networks, they smooth the output ofpower

supplies.Inresonant circuits they tuneradios to particularfrequencies.Inelectric power

transmission systems they stabilize voltage and power flow.

3.1 THEORY OF OPERATION

A capacitor consists of twoconductors separated by a non-conductive region. The non-

conductive region is called thedielectric.In simpler terms, the dielectric is just anelectrical

insulator.Examples of dielectric media are glass, air, paper,vacuum,and even

asemiconductordepletion region chemically identical to the conductors. A capacitor is assumed

to be self-contained and isolated, with no netelectric charge and no influence from any external

electric field. The conductors thus hold equal and opposite charges on their facing surfaces, and

the dielectric develops an electric field. InSI units, a capacitance of onefarad means that

onecoulomb of charge on each conductor causes a voltage of onevolt across the device.

An ideal capacitor is wholly characterized by a constantcapacitance C, defined as the ratio of

charge Q on each conductor to the voltage V between them.
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FIGURE 3.2 WORKING PRINCIPLE OF CAPACITOR

An ideal capacitor is wholly characterized by a constantcapacitance C, defined as the ratio of

charge Q on each conductor to the voltage V between them

Because the conductors (or plates) are close together, the opposite charges on the conductors

attract one another due to their electric fields, allowing the capacitor to store more charge for a

given voltage than if the conductors were separated, giving the capacitor a large capacitance.

Sometimes charge build-up affects the capacitor mechanically, causing its capacitance to vary. In

this case, capacitance is defined in terms of incremental changes.

ENERGY OF ELECTRIC FIELD

Work must be done by an external influence to "move" charge between the conductors in a

capacitor. When the external influence is removed, the charge separation persists in the electric

field and energy is stored to be released when the charge is allowed to return to its equilibrium

position. The work done in establishing the electric field, and hence the amount of energy stored,

is

Here Q is the charge stored in the capacitor, V is the voltage across the capacitor, and C is

the capacitance.

In the case of a fluctuating voltage V(t), the stored energy also fluctuates and

hencepower must flow into or out of the capacitor. This power can be found by taking

thetime derivative of the stored energy:

CURRENT VOLTAGE RELATION

The currentI(t) through any component in an electric circuit is defined as the rate of flow of a

charge Q(t) passing through it, but actual chargeselectronscannot pass through the dielectric

layer of a capacitor. Rather, an electron accumulates on the negative plate for each one that

leaves the positive plate, resulting in an electron depletion and consequent positive charge on one

electrode that is equal and opposite to the accumulated negative charge on the other. Thus the

charge on the electrodes is equal to theintegral of the current as well as proportional to the
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voltage, as discussed above. As with anyantiderivative,aconstant of integration is added to

represent the initial voltage V(t0). This is the integral form of the capacitor equation:

Taking the derivative of this and multiplying by Cyields the derivative form:

Thedual of the capacitor is theinductor,which stores energy in amagnetic field rather than an

electric field. Its current-voltage relation is obtained by exchanging current and voltage in the

capacitor equations and replacing Cwith the inductanceL.

4. RESISTOR

A resistor is apassivetwo-terminalelectrical component that implementselectrical resistance as

a circuit element.

FIGURE 4.1 SOME COMMON RESISTORS

Thecurrent through a resistor is indirect proportion to thevoltage across the resistor's terminals.

This relationship is represented byOhm's law:

whereIis the current through theconductor in units ofamperes,Vis the potential difference

measured across the conductor in units ofvolts,andRis the resistance of the conductor in units

ofohms.
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The ratio of the voltage applied across a resistor's terminals to the intensity of current in the

circuit is called its resistance, and this can be assumed to be a constant (independent of the

voltage) for ordinary resistors working within their ratings.

Resistors are common elements ofelectrical networks andelectronic circuits and are ubiquitous

in electronic equipment. Practical resistors can be made of various compounds and films, as well

asresistance wire (wire made of a high-resistivity alloy, such as nickel-chrome). Resistors are

also implemented withinintegrated circuits,particularly analog devices, and can also be

integrated intohybrid andprinted circuits.

The electrical functionality of a resistor is specified by its resistance: common commercial

resistors are manufactured over a range of more than nineorders of magnitude.When specifying

that resistance in an electronic design, the required precision of the resistance may require

attention to themanufacturing tolerance of the chosen resistor, according to its specific

application. Thetemperature coefficient of the resistance may also be of concern in some

precision applications. Practical resistors are also specified as having a maximumpower rating

which must exceed the anticipated power dissipation of that resistor in a particular circuit: this is

mainly of concern in power electronics applications. Resistors with higher power ratings arephysically larger and may requireheat sinks.In a high-voltage circuit, attention must sometimes

be paid to the rated maximum working voltage of the resistor. While there is no minimum

working voltage for a given resistor, failure to account for a resistor's maximum rating may

cause the resistor to incinerate when current is run through it.

Practical resistors have a seriesinductance and a small parallelcapacitance;these specifications

can be important in high-frequency applications. In alow-noise amplifier orpre-amp,

thenoise characteristics of a resistor may be an issue. The unwanted inductance, excess noise,

and temperature coefficient are mainly dependent on the technology used in manufacturing the

resistor. They are not normally specified individually for a particular family of resistors

manufactured using a particular technology. A family of discrete resistors is also characterizedaccording to its form factor, that is, the size of the device and the position of its leads (or

terminals) which is relevant in the practical manufacturing of circuits using them.

4.1 RESISTOR CODING

Carbon-composition and carbon film resistors are too small to have the resistance value printed

on their housings. Therefore, bands of color are used to represent the resistance value.
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The first and second band represents the numerical value of the resistor, and the color of the third

band specify the power-of-ten multiplier. The color bands are always read from left to right

starting with the side that has a band closer to the edge. For carbon-composition and carbon film

resistors, the common tolerances are 5%, 10%, and 20%, indicating that the actual value of the

resistor can vary from the nominal value by 5%, 10% and 20%. If the band is gold, it

specifies a 5% tolerance; silver specifies a 10% tolerance; if no band is present, the tolerance is

20%.

Note that the color-code system for capacitors is very similar to that of resistors except there is a

fifth band representing the temperature coefficient. This band is the first one closest to one end

of the capacitor. The other four fall into the same order as mentioned for resistors. In this case,

the second, third, and fourth bands are used to determine the capacitance. The fifth band

represents the tolerance of the capacitor.


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6. LIGHT EMITTING DIODE

A light-emitting diode (LED) is asemiconductor light source.[7]

LEDs are used as indicator

lamps in many devices and are increasingly used forgeneral lighting.Appearing as practical

electronic components in 1962,[8]

early LEDs emitted low-intensity red light, but modern

versions are available across thevisible,ultraviolet,andinfrared wavelengths, with very highbrightness.

FIGURE 6.1 LIGHT EMITTING DIODE

When a light-emitting diode is switched on,electrons are able to recombine withholes within the

device, releasing energy in the form ofphotons.This effect is calledelectroluminescence,and

the color of the light (corresponding to the energy of the photon) is determined by the

energyband gap of the semiconductor. An LED is often small in area (less than 1 mm2), and

integrated optical components may be used to shape itsradiation pattern.LEDs have many

advantages over incandescent light sources including lower energy consumption, longer lifetime,

improved physical robustness, smaller size, and faster switching. However, LEDs powerfulenough for room lighting are relatively expensive, and require more precise current and heat

management than compactfluorescent lamp sources of comparable output.

Light-emitting diodes are used in applications as diverse asaviation lighting,automotive

lighting,advertising, general lighting, andtraffic signals.LEDs have allowed new text, video

displays, and sensors to be developed, while their high switching rates are also useful in

advanced communications technology. Infrared LEDs are also used in the remote control units of
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many commercial products including televisions, DVD players and other domestic appliances.

LEDs are also used inseven-segment display.

Electronic symbol

Pin configuration anodeandcathode

6.1 WORKING

The LED consists of a chip of semiconducting materialdoped with impurities to create ap-n

junction.As in other diodes, current flows easily from the p-side, oranode,to the n-side,

orcathode,but not in the reverse direction. Charge-carrierselectrons andholesflow into the

junction fromelectrodes with different voltages. When an electron meets a hole, it falls into a

lowerenergy level and releasesenergy in the form of aphoton.

Thewavelength of the light emitted, and thus its color, depends on theband gap energy of thematerials forming the p-n junction. Insiliconorgermanium diodes, the electrons and holes

recombine by a non-radiative transition, which produces no optical emission, because these

areindirect band gap materials. The materials used for the LED have adirect band gap with

energies corresponding to near-infrared, visible, or near-ultraviolet light.

LED development began with infrared and red devices made withgallium arsenide.Advances

inmaterials science have enabled making devices with ever-shorter wavelengths, emitting light

in a variety of colors.

LEDs are usually built on an n-type substrate, with an electrode attached to the p-type layer

deposited on its surface. P-type substrates, while less common, occur as well. Many commercial

LEDs, especially GaN/InGaN, also usesapphire substrate.

.
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5.5 DC MOTOR

An electric motor convertselectrical energy intomechanical energy. A DC motor is

anelectric motor that runs ondirect current (DC) electricity.

TheDC electric motor generates torque directly from DC power supplied to the motor by

using internal commutation, stationary permanent magnets, and rotating electrical magnets.

Like all electric motors or generators, torque is produced by the principle ofLorentz 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. Maintenance involves regularly replacing the brushes

and springs which carry the electric current, as well as cleaning or replacing thecommutator.

These components are necessary for transferring electrical power from outside the motor to the

spinning wire windings of the rotor inside the motor.
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resistor R5 and capacitor C1. Switch S2 is used for manual reset. The microcontroller, based on

the inputs from sensor T1 (say left) and sensor T2 (say right), controls the motor to make the

robot turn left, turn right or move forward.

Port pins P2.0, P2.1, P2.2 and P2.3 are connected to pins 15,10,7 and 2 of motor driver

L293D. Port pins P2.0 and P2.1 are used for controlling the right motor, while port pins P2.2 and

P2.3 are used for controlling the left motor.

7.WORKING

Fig 7.1

Fig 7.1 shows the path of line follower robot. Where L is the left sensor and R is the

right sensor.

At the start when the robot is at point A sensors T1 and T2 are above the black surface

and port pins P3.0 and P3.1 of the microcontroller recieve logic0. As a result the robot moves

forward in straight direction.


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At point B, a left turn is encountered, and the left sensor comes above the white surface,

whereas the right sensor remains above the black surface. Port pin P3.0 of the microcontroller

recieves logic0 from the right sensor. As a result left motor stops and the right motor rotates, to

make robot turn left. This process continues until left sensor comes above the black background.

Similrly, at point C, where a right turn is encountered, the same procedure for right

turn is excecuted. When both sensors are at white surface, the robot should stop. The

output of the microcontroller depends on the input recieved at its port pins P3.0 and P3.1 as

shown in table below


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9.4 SOLDERING

Soldering is a process in which two or more metal items are joined together by melting and

flowing a filler metal into the joint, the filler metal having a relatively low melting point.Soft

soldering is characterized by the melting point of the filler metal, which is below 400 C

(752 F). The filler metal used in the process is calledsolder.

Soldering is distinguished frombrazingby use of a lower melting-temperature filler metal.

The filler metals are typically alloys that have melting temperatures below 350C. It is

distinguished fromweldingby the base metals not being melted during the joining process

which may or may not include the addition of a filler metal.[2]

In a soldering process, heat is

applied to the parts to be joined, causing the solder to melt and be drawn into the joint by

capillary actionand to bond to the materials to be joined bywetting action.

After the metal cools, the resulting joints are not as strong as the base metal, but have adequate

strength, electrical conductivity, and water-tightness for many uses.

9.41 Solders:

Soldering filler materials are available in many different alloys for differing applications. In

electronics assembly, the eutectic alloy of 63% tin and 37% lead (or 60/40, which is almost

identical in performance to the eutectic) has been the alloy of choice. Other alloys are used for

plumbing, mechanical assembly, and other applications.

An eutectic formulation has several advantages for soldering; chief among these is the

coincidence of the liquidus and solidus temperatures, i.e. the absence of a plastic phase. This

allows for quicker wetting as the solder heats up, and quicker setup as the solder cools. A non-

eutectic formulation must remain still as the temperature drops through the liquidus and solidus

temperatures. Any differential movement during the plastic phase may result in cracks, giving an

unreliable joint. Additionally, a eutectic formulation has the lowest possible melting point, which

minimizes heat stress on electronic components during soldering. Other common solders include

low-temperature formulations (often containingbismuth), which are
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often used to join previously-soldered assemblies without un-soldering earlier connections, and

high-temperature formulations (usually containing silver)which are used for high-temperature

operation or for first assembly of items which must not become unsoldered during subsequent

operations.

9.42 Flux:

In high-temperature metal joining processes (welding, brazing and soldering), the primary

purpose offluxis to prevent oxidation of the base and filler materials. Tin-lead solder, for

example, attaches very well to copper, but poorly to copper oxides (which form quickly at

soldering temperatures). Flux is nearly inert at room temperature, yet becomes strongly

reductive when heated. This helps remove oxidation from the metals to be joined, and inhibits

oxidation of the base and filler materials. Secondarily, flux acts as a wetting agent in the

soldering process, reducing thesurface tensionof the molten solder and causing it to better wet

out the parts to be joined.

10.CONSTRUCTION

Three wheels can be used fr this robot-one on the front and two at the rear. Front wheel can

rotate in any direction as specified by the rear wheel. Construction also requires two side

brackets for mounting motors,chasis etc. Castor wheel can be used for front wheel.
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11.PCB LAYOUT


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13.LIST OF TOOLS AND INTRUMENTS REQUIRED

Following tools and instruments are used for preparing the project

1. Soldering iron

2. Desoldering pump

3. Drill Machine

4. Multimeter

5. Filer

6. Tweezers

7. Screw driver

8. Power supply

9. Flux

10. Desoldering wick

11. Petrol

12. Brush

13. Soldering Wire


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14.COMPONENTS REQUIRED

SI.No NAME OF THE COMPONENT QUANTITY PRICE

1. AT89C51 1 55

2. IC L293D 1 80

3. IC LM324 1 18

4. L14F1 PHOTOTRANSISTOR 2 40

5. IN 4007 DIODE 1 2

6. 5MM LED 2 1.50

7. RESISTOR 10K 3 .25

8. RESISTOR 5.6K 2 .25

9. RESISTOR 330 1 .25

10. RESISTOR 220 1 .25

11. RESISTOR 10K-PRESET 2 5

12. CAPACITORS 10 F/16V ELECTROLYTIC 1 .5

13. CAPACITORS 33 pF CERAMIC 2 .75

14. CAPACITORS 47 F/16V ELECTROLYTIC 1 .5

15. CAPACITORS .1F CERAMIC 1 .75

16. ON/OFF SWITCH 1 2

17. PUSH TO ON SWITCH 1 10

18. CRYTAL OSCILLATOR 12 MHz 1 15

19. 6V DC GEARED MOTOR 2 20


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20. BATTERY 1.5V 4 9

21. 40 PIN IC BASE 1 1



TOTAL=260

PRECAUTION

As we were dealing with a phototransistor we need to control the natural light, since oursensor is even sensitive to sun light. So we need to place our sensor under the chasis. Position of

LED is quite important to us since it is the source of light to be reflected back to sensors.

APPLICATIONS

Industrial automated equipment carriers

Entertainment and small household applications.

Automated cars.

Tour guides in museums and other similarapplications.

Second wave robotic reconnaissance operations.

Future application:-can replaces trolleys in indudtries,road trains....


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LIMITATIONS

Choice of line is made in the hardware abstraction and cannot be changed by

software.

Calibration is difficult, and it is not easy to set a perfect value.

The steering mechanism is not easily implemented in huge vehicles and

impossible for non-electric vehicles (petrol powered).

Few curves are not made efficiently, and must be avoided.

Lack of a four wheel drive, makes it not suitable for a rough terrain.

Use of IR even though solves a lot of problems pertaining to interference, makes it

hard to debug a faulty sensor.

Lack of speed control makes the robot unstable at times.


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CONCLUSION

For a test, I held my robot in the air then two wheels rotated as expected and I

approached a white paper to sensors. Then, corresponding wheels stopped as expected. Hence

our product is working as per theory . Next, I put it down on the track, but unfortunately, it didnt

move. I found the torque of motors not enough to drive my robot. Even though the chosen DC

motor was slowest and gave highest torque among other DC motors in the lab, it wasnt enough.

For solving this problem, I will have to find a suitable DC motor with large torque and it even

moves through perfect plains.

Overall, the robot project wasnt successful, but it was quite a fun to go through all the process. I

also realized that there were many things to consider practically such as installation of motors,

building up a circuit by soldering and putting all parts together. This experience hopefully would

be helpful in the future work.


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19.REFERENCE/BIBILOGRAPHY

Efy magazine september 2009

1. [Online] // Wikipedia. - www.wikipedia.com.

2. [Online] // circuits today. - www.circuitstoday.com.

3. [Online] // electronics schematics. - www.electroschematic.com.

4. [Online] // electronics for you. -www.efy.com.
http://www.efy.com/http://www.efy.com/http://www.efy.com/http://www.efy.com/


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