Report on Exam Paper Security System

EXAM PAPER SECURITY SYSTEM

CHAPTER 1

INTRODUCTION

1.1 OVERIVIEW

Our project “Exam Paper Security System” is a system which will replace the traditional

manual exam paper printing and distribution. Manual paper printing and distribution has

many loopholes and have more chances of leakage of exam question papers. So, our idea is

to make a fully automatic paper printing and distribution system which ensures the integrity

of the examinations.

1.1.1 ORIGIN OF PROJECT

In past few months, we have seen that many of the scams related to the leakage of

examination papers of exams like AIEEE, B. Ed. etc. took place. On study of these scams

we came with the observation that either exam papers were leaked from the printing press

or breakage of envelope seal during distribution. These unwanted events made big question

mark on the security system and also became cause of big financial loss for the examination

boards.

In present scenario, most of the examinations are conducted offline at different cities across

the globe. The existing system of exam conduction is completely manual. From the

beginning of the procedure, there is complete manual interface such as paper printing, paper

collection, distribution and finally deliver to the exam center and it increases the chances of

paper leak. One basic requirement of exam should be maintained. These should be right

time of paper printing, collection, and distribution as per exam schedule.

The aim of our project is to make a automatic system which can cover all the above aspects

such as paper printing, paper collection and distribution on exam centre with right date and

right time. This project aims at creating a man less printing and packaging system with time

stamp based security system for examination paper, that contain some important general life

elements like LAN system, conveyer belt, printing machine, safe box etc.

1 EC-A/2011-12/PIET, JAIPUR


1.2 CAPABILTIES

Our project will provide the complete solution which can prevent the examination paper

leakage. The centre authority will be allowed to give command. There is only single

computer which will be controlled by exam cell in-charge. This computer is directly

connected to the printing press room. In printing press room, the computer will give

command to print the question papers. There is an infrared counter which count the number

of copies printed from the printer. This will increase the efficiency of the system.

The paper will be dropped and collected in a wooden box which is also called safe

box. The box will be locked automatically. There are a known number of copies in the box.

Now, this box will be passed to outside the room with the help of a conveyor belt. The box

will be collected at window and respective boxes will be distrusted to centers respectively.

Here we can observe that only person is operating the whole process. In this project,

there is very few chances of paper leak. Even though, if it happens then only one person is

responsible and this will bring out the defaulter.

There is no interference of Human being in the whole process and it increases the

efficiency as well as decreases the chances of paper leak and the financial loss of

government due to re-examination will be reduced.



CHAPTER 2

REVIEW OF STAGE I

2.1 INTRODUCTION

In project stage I, we have done literature survey and studied the feasibility of the project as

well as done a thorough market survey. The designing of algorithm and flowchart was

carried out in stage I. There was a case study done for different organization having manual

paper printing system. We have gone through this type of exam paper printing and

distribution mechanism currently being used in India and problems associated with it. Also

we have gone through the technical section of our project and synchronization between

various modules.

The aim of our project is to make an automatic system which can cover all the stuff

such as paper printing, paper collection, and distribution on exam center with right date and

time. This project is aimed at creating a man less printing and packaging system with time

stamp based security system for examination paper. There is no human intervention in the

whole process and it increases the efficiency as well as decreases the chances of paper leak

and the financial loss of government due to the reexamination will be reduced.

The paper will be printed only when a responsible authority gives command to

computer. There is a single authority that is responsible for the whole activity. A counter is

placed to count the number of papers. There is a preset limit of papers for printing. When it

reaches its limit, the printer stops to print papers and printed papers are dropped in box and

locked by a lock. Using a smart box which is made of a wooden and a electromagnetic lock

attached with it, it can open by some responsible authority on right date and time which is

already stored in real time control (RTC) chip. A password system is present there in order

to make great security of exam papers. The box can be open at the day of exam and it the

chances of exam paper leak.

The project is practically feasible, components will be easily available and has great

applications and benefits in the present scenario where government suffers from a huge

financial loss due to re-conduction of examination.



2.2 LITERATURE SURVEYThe literature survey covered almost aspect every aspect of paper printing and distribution

system were thoroughly studies while preparing the literature survey of exam paper leak

prevention system. This gives us better way to analyze the problem statement and try to find

out a better and efficient solution of exam paper leak.

2.3 CURRENT PAPER PRINTING AND DISTRIBUTION SYSTEM

At present, traditional paper printing system is being followed. The private printing press

undertakes the contract of paper printing by boards and universities. There is no monitoring

sometimes when papers are being printed at the printing press. This gives chances of paper

leak right form printing press and there are several other ways to leak the paper. Some of

them are:

The printing press owner can print more than required number of copies and can

sell it into the market.

The non-responsible behavior of printing press while carrying the bunch of paper

from one place to another.

If the seal of the packet is broken before the exam time, it also created a problem

since there is no mechanism is check when the seal is broken of packet.

Anyone can open the bunch of papers. It does not need a security password.

These drawbacks of traditional paper printing were not acceptable if something goes

wrong before the examinations date arrives. The government has to suffer with huge

financial loss which occurs due to re-examination as well as precious time of students also

gets wasted. As far as distribution is concerned, it does not have a real time application of

date and time.

2.4 ORGANISATION SURVEY

We have searched industries provide all type of solutions related to examination at

university level, entrance level and recruitment level which includes paper setting, printing,

packing and delivery. One of such industry is PRINT- INDIA. It is one of the leading

Printing Companies dealing exclusively in confidential jobs for the last 35 years. Another



international organization is PROMETRIC. This year PROMETRIC conducted CAT 2011

exam. We studied the examination system of both the organizations.

In Question Paper printing, work is segregated into three Parts :

Composing & Proofreading

Printing

Packing

2.4.1 Composing & Proofreading

With an inhouse composing house, we do work with highest confidentiality. The facility of

Proofreading is also within the premises with subject wise experts. We are having experts of

almost all language for Proofreading and translations, which help us to do our jobs

efficiently without any error.

2.4.2 Printing

Secondly the composed paper is printed on latest machines available till date any quantity

can be printed from 100–(in lakhs) in minimum time duration.

FIGURE 2.1: PRINTING MACHINE



2.4.3 Packing

The third step is packing of Question Paper-Booklets. In above mentioned all steps phase

no. 3 which is packing, is one of the most important and crucial in itself. Today, most of our

clients demand centrewise packing. We do centrewise packing with the help of

computerised programming which is 99.9% error less. In this our clients / institutes

provides us the paper number, quantity, centrewise distribution details. We feed all these

informations in our software programme and got printed the envelope labels. Centrewise

challans are also taken out of computer.

2.5 MARKET ANALYSIS

Different types of safe boxes are available in the market. The boxes are password protected

and have a mechanical lock. Some of the safe boxes available in the market are:

Digimatic Electronic Safety Locker

Godrej Electronic E-Swipe Safe

Shadows Electronic Safe Lock

Godrej Electronic Taurus Safe

2.5.1 Market Analysis Inferences

Lots of safe boxes are available in the market which are highly secure in terms of their

designing. But none of them has capability of real time handling. All the safe boxes are only

designed of the storage purpose. No electronic box is yet designed which can be used for

the transportation of the examination papers.

2.6 ONLINE EXAMINATION

Online examination is a new technique to conduct an examination through internet. The

formal examination system is a very long procedure to conduct an examination. From the

respect of the exam, they should give extra effort on the examination to select employees

for the organization. This is a huge responsibility and extra load to the recruiter to conduct

an examination. This is very costly and extremely tedious to conduct an examination. Side

by side online examination is a very sophisticated examination conducting system.



Lot of companies is gladly taking this modern system to exemption form the tedious

written examination system. Low cost, minimum effort, minimum employee deployment,

saving time, instant result and conduct an examination India and abroad.

FIGURE 4.8: ONLINE EXAMINATION HALL

2.6.1 Drawbacks of Online Examination

Computerized testing, often described as facile and efficient, has some drawbacks. The

most common disadvantages are computer glitches, errors in content, and security lapses.

There have been several documented occurrences of security breaches. One example is the

Graduate Record Examination, which in 2002 was apparently “hacked” and sold on the

internet in Asia. This was a live and active exam, not a practice test. This had damaging

consequences, not only for the test administrators, but for the thousands of students taking

the test.

On the practical side, some test takers report that it is more difficult to navigate back

to rework problems. Some test takers are resistant to the computerized testing process

because they are accustomed to taking notes and circling questions and/or answers for later

review. Others say that they read more quickly and more easily on paper than on a glaring

computer screen. Another incident of standardized test cheating on the GRE occurred when

a student on the East coast relayed information to students on the West coast; that scheme

took advantage of the three-hour time difference between the two regions. While electronic



glitches are rare, they have been known to occur, for instance when computer crashes

voided the efforts of thousands of GMAT takers. There are also cases in which the

correction software has corrupted scores.

2.6 MODIFICATIONS IN PROJECT

Later on, there was a little bit change in our project execution idea. These changes were

made because either of the non-availability of resources or some technical limitations. Some

of the proposed changes in our project are:

Earlier we were planning to use DS12887 RTC chip (Serial Communication) but it

is not available in the market in Jaipur. So, we have to drop our idea of using DS

12887 and finally we went for DS1307 RTC chip with same function with different

protocol (i2c protocol).

Synchronization of various modules and sequential arrangement were also made due

to some technical problem and mechanical assembly.



CHAPTER 3

WORKING PRINCIPLE

3.1 INTRODUCTION

The centre authority will be allowed to give command. There is only single computer which

will be controlled by Exam cell in charge. This computer is directly connected to the

printing press room. In printing press room, the computer will give command to print out

the papers. There is an Infrared counter which count the number of copies printed from

printer. For example, if there is a bunch of 100 papers, then only adjust number of copies

will be printed. This will increase the efficiency of the system.

The paper will be dropped and collected in a wooden box which is also called safe

box. The box will be locked automatically. There are a known number of copies in the box.

Now, this box will be passed to outside the room with the help of a conveyor belt. The box

will be collected at window and respective boxes will be distrusted to centers respectively.

Here we can observe that only person is operating the whole process. In this project,

there are very few chances of paper leak. Even though, if it happens then only one person is

responsible and this will bring out the defaulter. There is no interference of Human being in

the whole process and it increases the efficiency as well as decreases the chances of paper

leak.



FIGURE 3.1: FUNTIONAL BLOCK DIAGRAM



3.2 BLOCK DIAGRAM

FIGURE 3.2: BLOCK DIAGRAM


MICRO CONTROLLER

Keyboard

Power Supply

Real Time Clock

LCD

Electro Mechanical

Lock

Alarm


3.3 WORKING OF SAFE BOX

The exam centre in-charge will be allowed to open the box after a predefined set time and

date. So when box is tried to open matching of correct password (if entered) with the date

and time at time of access is take place and box is unlocked if predefined conditions are

matched.

It will be much known the date and time of the exam which is going to be organized.

So each paper will have some particular date and tine and the digital clock are set. The box

will be open on the exam day pre-defined time. There is a real time control on the safe box

and it gives an additional feature to our project.

There is an Electro-mechanical lock will be associated with safe box. It is similar to

the Automatic Teller Machine (ATM) lock which has a predefined password. Lock can only

be open by entering the correct password in limited attempts.

If someone tries to open the lock before time or tries to open the box by entering

passwords beyond attempts, then alarm signal will be generated and it will give information

to the nearest police station or exam in-charge and appropriate action can be taken.

So, this project will be helpful to reduce the chances of Examination paper leak.

This methodology can be applied in many National level exams, board exams and

university exams etc. This technology is helpful to reduce the government loss because

there is an huge amount of money is spent on conducting examinations at national level. It

will also save the time wasted because of re-examination conduction.



CHAPTER 4

CIRCUIT DESCRIPTION4.1 CIRCUIT DIAGRAM

FIGURE 4.1: CIRCUIT DIAGRAM



4.2 CIRCUIT WORKING

The main idea of smart safe box is that digital code locked should open after the preset date

and time. So, Current date and time has to be tracked and intelligence has to be applied

accordingly. For this purpose we are using microcontroller AT89c5l and RTC chip DSl307.

AT89C5l is product from ATMEL (based on 805l architecture) DSl307 I2C serial interface

real-time clock (RTC) is a low-power, full binary-coded decimal (BCD) clock/calendar IC.

On the First use RTC, Correct Date and Time are stored in the internal registers of

DS1307. Later, whenever user tries to enter password, date and Time are fetched from RTC

chip. Now to enter the password, a means of communication between microcontroller and

user has to be provided. Keyboard is used as this means of communication. In our Project

we are using 4*4 matrix keypad. This keypad provides 16 keys and our password length is

7, so it is sufficient for our project. Matrix keypad is designed by us as market cost is 8-9

times higher.

Now, User can enter the password using the keypad. The LCD is used to display the

output and the date and time. The user is given three attempts to enter the correct password.

If the user fails to enter the correct password in given attempts then the system will

terminate automatically. If the user enters correct password then the electromechanical lock

will open and the examination papers can be taken out.

4.3 PCB DESIGN

4.3.1 Printed Circuit Boards

The miniaturization in electronic equipment design has introduced a new technique known

as Printed Circuit Board. Printed circuit board is used to interconnect various electronic

circuit printed on it and is provided with holes to accommodate various electronic

components.

Printed circuit board (PCB) consists of an insulating base substrate, which is rigid,

with metallic circuitry photo chemically formed up on the substrate. Interconnections

between components are achieved by means of conducting paths (thin Cu film) running on

or through the substrate called tracks. The width of the tracks depends on the amount of

current it has to carry. The tracks meet components to which they are to be connected by



means of Land or pads which takes form of larger area of Cu. The lands may be of different

shapes and sizes and have holes drilled through them. These holes can either accommodate

component leads or via-holes. The via holes also known as plated through holes (PTH)

provide connections through the substrate to other track areas. These aroused in case of

double sided and multilayer PCBs only.

FIGURE 4.2 PCB FEATURES

Once PCB is designed and fabricated, the circuit can be assembled easily by

mounting and soldering the component in the holes provided for them.

4.3.2 Advantages and Disadvantages of Printed Circuit Boards

Advantages

1. Phase saving of wire: In PCB the interconnection between the components is made

through copper tracks instead of using a number of wires carrying electric circuit.

2. Saving of space: The circuit layout of PCB is designed such that it occupies least space.

Also the use of Cu tracks in place of wires makes the interconnections less bulky. Thus

printed circuit board occupies less space and thus has less weight than the circuit

assembled on general-purpose circuit board.

3. Saving of time: Much time is saved in assembling a circuit over a PCB as compared to

conventional method.

4. Tight connection: As the connections are made automatically through Cu tracks, there is

no chance of loose connection or short circuit

5. Low cost: Mass production can be achieved at lower cost.



6. Reliability: All the above factors bring reliability in performance of the equipment

7. Now-a-days component wiring and assembly can be mechanized by wave soldering of

vapour phase reflow soldering.

Disadvantages

1. As the copper tracks are very thin, they can carry little current. Hence a PCB cannot be

used for circuit with heavy currents because in that case the strips will be heated up and can

cause problems.

2. Soldering needs precautions as the risk of strips being overheated and destroyed is always

there.

4.3.3. Types of PCB

There are four types of printed circuit boards

1. Single sided PCB

2. Double sided PCB

3. Multi-layered PCB

4. Flexible PCB

4.3.3.1 Single Sided PCB

In single sided boards, as the name suggests, copper is coated on one side of the board or

laminate. So the circuitry is only on one side of the board and thus is the simplest form of

PCB. These are simplest to manufacture and hence have least cost of production.

In these PCB’s, to jump over the Cu tracks jumper wires may be used. Use of

jumper is restricted as far as possible because it decreases the reliability and if their number

is more than a few, the use of double sided PCB should be considered.



FIGURE 4.3 SINGLE SIDED PCB

4.3.3.2 Double Sided PCB

These are used where space is more important than cost of the PCB. Double sided boards

are Cu-coated on both sides. Circuit is etched on both sides but components are mounted

only on one side. Tracks on one side can be joined to tracks on the other side by means of

wire links. Now a days plated through holes (PTH) are available which do the same thing,

but their use makes the PCB expensive. So the total number of PTH should be kept to a

minimum for reasons of economy and reliability.

FIGURE 4.4 DOUBLE SIDED PCB

4.3.3.3 Multi layered PCB

In multi-layered boards, two or more boards with circuitry formed upon them are carefully

aligned, stacked up and bonded together. These boards are used where a very large circuit

has to be fabricated on a single board. At the same time, they are the most complex from

manufacturing point of view. Here also, components are mounted on only one side of the

board. Electrical connections are established from one side of the board to the other and to

the inner layer circuitry by using PTH.



FIGURE 4.5 MULTI-LAYERED PCB

4.3.3.4 Flexible PCB

This is basically a highly flexible variant of the conventional rigid PCB. The flexible boards

are of two types, static and dynamic. Static flexible circuits can be bent into particular

configuration which remains constant throughout product life and results in space saving.

Dynamic flexible circuits can be deformed continuously during operations and are used to

interconnect devices which need to he moved relative to each other.

4.3.4 Laminates

The board on which the circuit is etched consist of base material\laminate on which

conductor foils are bonded or deposited by some process.

(a) Base material: PCB’s are laminates. They are made from two or more sheets of base

materials stuck together. There are many materials used for making laminates for PCBs.

Commonly used materials are phenolic resin reinforced with paper filler (phenolic

laminates) for low cost, melamine resin reinforced with glass filler (melamine

laminates) for abrasion resistance, epoxy resin reinforced with glass filler (epoxy

laminations) for higher mechanical strength, low dimensional change and fungus

resistance; Teflon reinforced with glass (Teflon laminations) for microwave applications;

silicon resin reinforced with glass (silicon laminates) for high temperatures. Reliability of

PCB greatly depends on the quality of base material used.

(b) Conducting material: The conducting materials used for coating the laminate are

copper, silver, gold, brass and aluminium. However, the most widely used material is high

purity electrolytic copper and the laminates coated with copper foil are called as Cu clad

laminates.



4.3.5. Design of PCB Layout/Pattern

Throughout the manufacturing process of a PCB, visual and electrical inspection is carried

out to locate any flaws that might have crept in due to process automation like ‘Tombstone

effect’ when the solder is heated too quickly and one end of the component lifts up from the

board failing to make contact, or excess flow of solder or bridging. Even after the

manufacturing process, the boards are tested for the output levels under varying conditions

of environment, stress and strain.

FIGURE 4.6 FLOW DIAGRAM OF PCB MANIFUACTURING

Before designing a PCB layout, complete circuit diagram must be available with the

designer. The design of the layout is done on the computer using CAD (Computer Aided

Design) or a standard drawing program. The layout is designed in such a way as to

accommodate the whole circuit in minimum space avoiding use of jumpers as far as



possible. Besides the complete outlines and interconnections, the layout should include

information on:

a. Component hole diameter

b. Conductor width

c. Minimum spacing to be provided between the tracks.

Finally take the print out of the pattern / layout on a normal A4 size paper. Also

make sure that it is the correct size; Check the layout carefully. This printout is called as

positive film.

4.3.6. Film Making or Mask Making

The film negative which is finally used as a mask for the direct exposure of the photo resist-

coated PCB is called Film Master. Making of a Negative film (Film master) from a positive

involves the steps listed below. All these steps are performed in a dark room.

Film Maker Machine: Collect the positive film from the CAD lab. Cut lithography

film on which the negative is to be made to the size equal to the positive film. Start

the machine for 5 seconds. Take the negative film out of the machine by lifting it

from the corners.

Development: Take a developing tray. Put sufficient developer in the tray so that

the negative film is dipped completely in it. The film should be handled at its

corners with the help of forceps. Now slide the negative film through the

developing solution. Turn the tray quickly and lift the tray on each side of rotation.

This is continued throughout the developing time (1-1.5min).

Stop bath: After the development is over, the film is lifted above the developing

tray (with the help of forceps) for a few seconds so that the excess developer

drops out. Immediately thereafter, the film is immersed in to the stop bath (plain

water taken in a tray) for 1 min. This will effectively stop the development action

Fixing: Now mix 1 cap of fixer solution in 1 glass of water in a tray. Place the film

in this fixing bath for 0.5 min.



Washing: Take out the film from the fixer bath and wash it in running water.

Washing is an important stage in film master preparation because if some chemicals

remain on it, they will decompose and attack the image, causing stained and faced

film.

4.3.7 Making of Printed Circuit Boards

Various steps involved in the making of PCB are:

Pre-processing

Lithography

Etching

Stripping

Drilling

Testing

Loading of components

Soldering

Pre-processing

As its name, this step involves all the initial preparation to be made before actual processing

of copper clad laminate starts, such as

a) Collect the printout of the layout from the CAD lab.

b) Cut the copper clad laminate to the required size using a cutter.

c) Clean the board by scrubbing with steel wool or very fine wet sand paper. Dry the

board thoroughly. Make sure that the board is clean and free from fingerprints or

any traces of contamination.

d) Drill tooling/mounting holes.



Lithography

Lithography is typically the transfer of the copper track and land pattern from the negative

film to a material (copper clad). It includes the following steps:

1. Pattern Transfer: To precede you will need a cut-out of a single PCB image from the

glossy paper, a very clean copper board and a clothes iron. The PCB-to-be needs to be

very clean.PCB can be washed with hot water and dish soap. Using acetone or alcohol

to rub it clean seems to work well but may not be necessary. Make sure the copper is

dry and that no soap or chemical residue remains. Do not touch the copper with your

fingers as you'll spread greasy human juice which may keep the toner from sticking.

You can gently sand the board, using very fine sandpaper.

When the copper looks clean, shiny and new, you are ready to proceed. Place the

PCB mirror image face down on the copper, ensuring it is correctly positioned. You can

use a few pieces of tape to secure the glossy paper to the board but I find that, if you are

careful when you begin to iron, the paper sticks and stays in place on its own. Preheat

your trusty clothes iron, using the hottest setting its got (cotton, linen or above).

When you are done, be careful as the board will be hot. Immerse the board and

paper in hot water for a few minutes (up to 10 if you've got the patience). This will

soften things up a bit. Carefully remove the paper. If certain areas seem particularly

difficult to peel off, you can try soaking a bit more. If everything went well, you will

have a copper board with your PCB pads and signal lines traced out in black toner. You

can see that even fine lines, such as the contour, have been successfully transferred.

2. Development: After lithography process, the image of the pattern transferred on the

copper clad needs to be developed. The development stage involves removal of less

soluble unexposed area of resist in case of negative resist and exposed areas in case of

positive resist. Here, we are using a negative photo resist Method.

Take a tray and put sufficient developer solution in it such that the board can be

completely dipped in it. Developer solution is prepared by mixing liquid photo resist

developer concentrate with 1 part developer to 9 part of water.

Place the board into the white developer solution. The board should be handled at its

corners with the help of forceps. Now lift the tray on each side in rotation so that the



liquid developer is flowed over and back on the board. This is continued throughout the

developing time (1 min). During development, the developer solution etches away the

unexposed region of the negative photo resist showing copper and the PCB layout will

be revealed. After the development is over, lift the board and wash it in stop bath. This

will effectively stop the development action.

FIGURE 4.7 DEVELOPMENT OF PCB

3. Fixing: To fix the pattern on the board, mix 1 cap of fixer (blue die solution) in 1 glass

of water in tray. Place the board in the solution for at least 0.5 min. Remove the board

from the fixer bath and wash it under running water.

4. Etching: This process is used for removal of PCB’s copper surface, which is not

protected by the photo resist. Thus final Cu pattern is formed on the board after etching.

The board obtained after photolithography is dipped in an etching solution and

heated for 6-10 min. at 400C. The solution etches \ dissolves away the exposed\

undesired copper areas, leaving the desired copper pattern on the board. The different

Types of etching solution used are:

a. Ferric Chloride (FeCl3)

b. Chromatic Chloride

c. Cupric Chloride (CuCl2)



d. Alkaline Ammonia

Out of these four, ferric chloride is the most commonly used etchant. The reaction of

FeCl3 and CuCl2 etching solutions with copper are:

FeCl3 + Cu → FeCl2 + CuCl

Ferric chloride Copper Ferrous chloride

CuCl2 + CuCl → 2CuCl

Chromatic acid etching is usually carried out with the addition of Sulphuric acid. Hence

it is called chromic Sulphuric acid. The choice of suitable etchant solution for PCB

production depends on factors like etching speed, copper dissolving capacity, etchant price

etc.

Stripping

After etching, the negative photo resist coating left on the copper pattern can be removed

using a tube of photo resist stripper and the PCB is washed clean under tap water and dried

using tissue paper.

Drilling

Drilling is used to create the component lead holes and through holes in a PCB. These holes

pass through the land areas and should be positioned correctly. The drilling process can be

performed by using manually operated drilling machines or by using CNC drilling

machines. For a particular PCB, a wide range of drill holes may be required smaller holes

are required for component leads whereas larger diameter holes are required for bolting heat

sinks, connectors etc.



FIGURE 4.8: DRILLING

Bare Board Testing

Before mounting the components on the PCB, this bare board needs to ensure that the

required connections exist (i.e. visual inspection), and that there are no short circuit (i.e.

continuity testing) and that drill holes are properly placed. After drilling and testing, the

board the board is now ready to stuff components.

Loading Component

Loading of components on a PCB is the process of inserting components in to the holes in

the board. This loading can be done by hand or by machine. Machine is used when there is

mass production of boards of the same pattern.

Soldering

Solder the components loaded on the PCB by using either manual soldering or wave

soldering technique. Manual soldering is done with the help of soldering iron, while in wave

soldering; large number of joints is made simultaneously using a older bath. Wave soldering

is a more efficient method and is used in large scale industry where high productivity is

required.

FIGURE 4.9: COMPONENT SOLDERED



Finally take the print out of the pattern / layout on a normal A4 size paper. Also

make sure that it is the correct size; Check the layout carefully. This printout is called as

positive film.

4.4 PCB LAYOUT

FIGURE 4.10: BASIC CONTROLLER PCB LAYOUT



FIGURE 4.11: RTC PCB LAYOUT

FIGURE 4.12: LCD BASE PCB LAYOUT



4.5 PCB SOFTWARE DETAILS

Express PCB is a complete state-of-the-art PCB Design System. It includes:

PCB Layout — PCB designs with an easy-to-use manual routing tools, shape-based

auto router and auto-placer.

Schematic — Schematic Capture with multi-level hierarchy and export to PCB

Layout, Spice or Net list.

Component and Pattern Editors — allow you to make new parts and footprints.

Standard Libraries - include 100,000+ parts.

Import/Export Features - allow you to exchange designs and libraries with other

EDA tools.

Step-by-Step Tutorial - learn the software and start real work in a few hours.



FIGURE 4.13: EXPRESS PCB SCREENSHOT

4.5.1 Express PCB provides the following features:

Easy to learn user interface: To design a schematic, simply select and place

components onto your document and connect them together using the wire and bus

tools. Multi sheet and hierarchical schematics are supported. Then select the menu

option 'Convert to PCB' to convert the schematic to PCB. Layout can be updated

from Schematic in a few clicks at any time. When you create or edit design objects

they are highlighted to improve your work.

Smart placement and auto-placement features: After converting Schematic to

PCB layout, place board outline and arrange components. Then use "placement by

list" for chips/connectors and auto-placement for other components to get acceptable

result in a few minutes and start routing.

Easy to use manual and powerful automatic routing: Express PCB software

includes 2 automatic routers (Shape-based and Grid-based). Shape Router is able to

route complex layouts with SMD components as well as single-layer boards. Grid

Router can also make single-layer boards with jumper wires. With Spectra

DSN/SES interface you can use external shape-based or topological auto router.

Intelligent manual routing tools allow you to create and edit traces by 90, 45 degree

or without any limitations. Curved traces are supported. Through, blind or buried

vias can be used in automatic and manual routing. Board size is not limited.

Shape-based copper pour: Powerful copper pour system can help to reduce your

manufacturing costs by minimizing the amount of etching solution required. To use

it, all you have to do is insert a copper area on your board in the PCB Layout

program and any pad or trace inside the selected area will be automatically

surrounded with a gap of the desired size. Using copper pour you can also create

planes and connect them to pads and vias (different thermal types are supported).

Advanced Verification Features: Schematic and PCB design modules have

number of verification features that help control project accuracy on different design

stages: The ERC function shows possible errors in Schematic pin connections using

defined rules and allows you to correct errors step-by-step. DRC function checks the

clearance between design objects, minimum size of traces, and drills. Errors are

displayed graphically and you can fix them step-by-step and rerun the DRC in one



click after any corrections. Net Connectivity Check verifies if all nets of PCB are

electrically connected. This feature uses traces; copper pour filled area and shapes to

control connectivity, then reports broken and merged nets with area details.

Comparing to Schematic allows you to check if routed PCB is identical with

Schematic.

Spice Support: With Express PCBSchematic Capture or Component Editor

specify spice settings or attach models to the parts. Then export .cir net-list of your

Schematic to LT Spice or another simulation software to verify how it works.

Import/Export Features: Package modules allow you to exchange schematics,

layouts and libraries with other EDA and CAD packages (DXF, Eagle, P-CAD,

PADS, ORCAD). Express PCB Schematic Capture and PCB Layout also support

Accel, Allegro, Mentor, PADS, P-CAD, Protel and Tango net list formats.

Manufacturing output formats: Express PCB provides support for a number of

different manufacturing output formats. Using this PCB software you can produce

N/C Drill files for numerically controlled (N.C.) drilling machines and RS-274X

Gerber files for sending to board manufacturers. Vectorizing function allows

exporting true-type fonts and raster images. Also Express PCBDXF output.

Producing PCB’s using milling method: Express PCBallows you to export edge

poly lines to DXF. The DXF files can be converted to G-code with Ace Converter.

Before edge exporting the DRC function of PCB layout program checks the design

and shows possible problems if exist.

Standard component libraries: Express PCB package includes component and

pattern libraries which contain 100,000+ components from different manufacturers.

Creation of your own libraries: Component and Pattern Editors allow designing

your own symbols and patterns. To create complete components simply connect

them together using Component Editor.



FIGURE 4.14: BASIC MICROCONTROLLER CIRCUIT



FIGURE 4.15: REAL TIME CLOCK CIRCUIT



CHAPTER 5

COMPONENT DESCRIPTION

5.1 8051 MICROCONTROLLER

The Intel 8051 microcontroller is one of the most popular general purpose microcontrollers

in use today. The success of the Intel 8051 spawned a number of clones which are

collectively referred to as the MCS-51 family of microcontrollers, which includes chips

from vendors such as Atmel, Philips, Infineon, and Texas Instruments.

5.1.1 About the 8051

The Intel 8051 is an 8-bit microcontroller which means that most available operations are

limited to 8 bits. There are 3 basic "sizes" of the 8051: Short, Standard, and Extended. The

Short and Standard chips are often available in DIP (dual in-line package) form, but the

Extended 8051 models often have a different form factor, and are not "drop-in compatible".

All these things are called 8051 because they can all be programmed using 8051 assembly

language, and they all share certain features (although the different models all have their

own special features).

FIGURE 5.1: 8051 MICROCONTROLLER



Some of the features that have made the 8051 popular are:

64 KB on chip program memory.

128 bytes on chip data memory (RAM).

4 register banks.

128 user defined software flags.

8-bit data bus

16-bit address bus

32 general purpose registers each of 8 bits

16 bit timers (usually 2, but may have more, or less).

3 internal and 2 external interrupts.

Bit as well as byte addressable RAM area of 16 bytes.

Four 8-bit ports, (short models have two 8-bit ports).

16-bit program counter and data pointer.

1 Microsecond instruction cycle with 12 MHz Crystal.

8051 models may also have a number of special, model-specific features, such as UARTs,

ADC, OpAmps, etc...

5.1.2 Typical applications

8051 chips are used in a wide variety of control systems, telecom applications, and robotics

as well as in the automotive industry. By some estimation 8051 family chips make up over

50% of the embedded chip market.



FIGURE 5.2: PIN DIAGRAM OF THE 8051 DIP

5.1.3 Basic Pins

PIN 9: PIN 9 is the reset pin which is used reset the microcontroller’s internal registers and

ports upon starting up. (Pin should be held high for 2 machine cycles.)

PINS 18 & 19: The 8051 has a built-in oscillator amplifier hence we need to only connect a

crystal at these pins to provide clock pulses to the circuit.

PIN 40 and 20: Pins 40 and 20 are VCC and ground respectively. The 8051 chip needs +5V

500mA to function properly, although there are lower powered versions like the Atmel 2051

which is a scaled down version of the 8051 which runs on +3V.

PINS 29, 30 & 31: As described in the features of the 8051, this chip contains a built-in

flash memory. In order to program this we need to supply a voltage of +12V at pin 31. If

external memory is connected then PIN 31, also called EA/VPP, should be connected to

ground to indicate the presence of external memory. PIN 30 is called ALE (address latch

enable), which is used when multiple memory chips are connected to the controller and only

one of them needs to be selected. We will deal with this in depth in the later chapters. PIN

29 is called PSEN. This is "program select enable". In order to use the external memory it is

required to provide the low voltage (0) on both PSEN and EA pins.



Ports

There are 4 8-bit ports: P0, P1, P2 and P3.

PORT P1 (Pins 1 to 8): The port P1 is a general purpose input/output port which can be

used for a variety of interfacing tasks. The other ports P0, P2 and P3 have dual roles or

additional functions associated with them based upon the context of their usage.

PORT P3 (Pins 10 to 17): PORT P3 acts as a normal IO port, but Port P3 has

additional functions such as, serial transmit and receive pins, 2 external interrupt pins, 2

external counter inputs, read and write pins for memory access.

PORT P2 (pins 21 to 28): PORT P2 can also be used as a general purpose 8 bit port

when no external memory is present, but if external memory access is required then

PORT P2 will act as an address bus in conjunction with PORT P0 to access external

memory.

PORT P0 (pins 32 to 39) PORT P0 can be used as a general purpose 8 bit port when no

external memory is present, but if external memory access is required then PORT P0

acts as a multiplexed address and data bus that can be used to access external memory in

conjunction with PORT P2. P0 acts as AD0-AD7, as can be seen from fig 5.1.

Oscillator Circuits

The 8051 requires the existence of an external oscillator circuit. The oscillator circuit

usually runs around 12MHz, although the 8051 (depending on which specific model) is

capable of running at a maximum of 40MHz. Each machine cycle in the 8051 is 12 clock

cycles, giving an effective cycle rate at 1MHz (for a 12MHz clock) to 3.33MHz (for the

maximum 40MHz clock).

This is "program select enable". In order to use the external memory it is required to provide

the low voltage (0) on both PSEN and EA pins.



5.1.4 Internal Architecture

FIGURE 5.3: INTERNAL SCHEMATICS OF 8051


http://en.wikibooks.org/wiki/File:Intel_8051_arch.svg


Data and Program Memory

The 8051 Microprocessor can be programmed in PL/M, 8051 Assembly, C and a number of

other high-level languages. Many compilers even have support for compiling C++ for an

8051.

Program memory in the 8051 is read-only, while the data memory is considered to be

read/write accessible. When stored on EEPROM or Flash, the program memory can be

rewritten when the microcontroller is in the special programmer circuit.

Program Start Address

The 8051 starts executing program instructions from address 0000 in the program memory.

Direct Memory

The 8051 has 256 bytes of internal addressable RAM, although only the first 128 bytes are

available for general use by the programmer. The first 128 bytes of RAM (from 0x00 to

0x7F) are called the Direct Memory, and can be used to store data.

Special Function Register

The Special Function Register (SFR) is the upper area of addressable memory, from address

0x80 to 0xFF. A, B, PSW, DPTR are called SFR. This area of memory cannot be used for

data or program storage, but is instead a series of memory-mapped ports and registers. All

port input and output can therefore be performed by memory move operations on specified

addresses in the SFR. Also, different status registers are mapped into the SFR, for use in

checking the status of the 8051, and changing some operational parameters of the 8051.

General Purpose Registers

The 8051 has 4 selectable banks of 8 addressable 8-bit registers, R0 to R7. This means that

there are essentially 32 available general purpose registers, although only 8 (one bank) can

be directly accessed at a time. To access the other banks, we need to change the current

bank number in the flag status register.

A and B Registers



The A register is located in the SFR memory location 0xE0. The A register works in a

similar fashion to the AX register of x86 processors. The A register is called the

accumulator, and by default it receives the result of all arithmetic operations.

The B register is used in a similar manner, except that it can receive the extended

answers from the multiply and divide operations. When not being used for multiplication

and Division, the B register is available as an extra general-purpose register.

Computer

A computer is a programmable machine designed to sequentially and automatically carry

out a sequence of arithmetic or logical operations. The particular sequence of operations can

be changed readily, allowing the computer to solve more than one kind of problem.

Conventionally a computer consists of some form of memory for data storage, at least one

element that carries out arithmetic and logic operations, and a sequencing and control

element that can change the order of operations based on the information that is stored.

Peripheral devices allow information to be entered from external source and allow the

results of operations to be sent out.

A computer's processing unit executes series of instructions that make it read, manipulate

and then store data. Conditional instructions change the sequence of instructions as a

function of the current state of the machine or its environment.

The first electronic computers were developed in the mid-20th century (1940–1945).

Originally, they were the size of a large room, consuming as much power as several

hundred modern personal computers (PCs).

Modern computers based on integrated circuits are millions to billions of times more

capable than the early machines, and occupy a fraction of the space. Simple computers are

small enough to fit into mobile devices, and can be powered by a small battery. Personal

computers in their various forms are icons of the Information Age and are what most people

think of as "computers". However, the embedded computers found in many devices from

MP3 players to fighter aircraft and from toys to industrial robots are the most numerous.


http://en.wikipedia.org/wiki/Industrial_robot

http://en.wikipedia.org/wiki/Toy

http://en.wikipedia.org/wiki/Fighter_aircraft

http://en.wikipedia.org/wiki/Digital_audio_player

http://en.wikipedia.org/wiki/Embedded_system

http://en.wikipedia.org/wiki/Information_Age

http://en.wikipedia.org/wiki/Icon

http://en.wikipedia.org/wiki/Mobile_device

http://en.wikipedia.org/wiki/Integrated_circuit

http://en.wikipedia.org/wiki/Personal_computer

http://en.wikipedia.org/wiki/Data_(computing)

http://en.wikipedia.org/wiki/Memory_(computers)

http://en.wikipedia.org/wiki/Machine


5.2 DS 1307 (RTC)

The DS1307 serial real-time clock (RTC) is a low-power, full binary-coded decimal (BCD)

clock/calendar plus 56 bytes of NV SRAM. Address and data are transferred serially

through an I²C, bidirectional bus. The clock/calendar provides seconds, minutes, hours, day,

date, month, and year information. The end of the month date is automatically adjusted for

months with fewer than 31 days, including corrections for leap year. The clock operates in

either the 24-hour or 12-hour format with AM/PM indicator. The DS1307 has a built-in

power-sense circuit that detects power failures and automatically switches to the backup

supply. Timekeeping operation continues while the part operates from the backup supply.

FIGURE 5.4: REAL TIME CLOCK



FIGURE 5.5: DS 1307 PIN DIAGRAM

The key features of DS 1307 are:

Real-Time Clock (RTC) Counts Seconds, Minutes, Hours, Date of the Month,

Month, Day of the week, and Year with Leap-Year Compensation Valid Up to 2100

56-Byte, Battery-Backed, General-Purpose RAM with Unlimited Writes

I²C Serial Interface

Programmable Square-Wave Output Signal

Automatic Power-Fail Detect and Switch Circuitry

Consumes Less than 500nA in Battery-Backup Mode with Oscillator Running

Optional Industrial Temperature Range: -40°C to +85°C

Available in 8-Pin Plastic DIP or SO



FIGURE 5.6: INTERFACING OF RTC

5.3 RESISTORS

Resistors are components that have a predetermined resistance. Resistance determines how

much current will flow through a component. Resistors are used to control voltages and

currents. A very high resistance allows very little current to flow. Air has very high

resistance. Current almost never flows through air. (Sparks and lightning are brief displays

of current flow through air. The light is created as the current burns parts of the air.) A low

resistance allows a large amount of current to flow. Metals have very low resistance. That is

why wires are made of metal. They allow current to flow from one point to another point

without any resistance. Wires are usually covered with rubber or plastic. This keeps the

wires from coming in contact with other wires and creating short circuits.

High voltage power lines are covered with thick layers of plastic to make them safe,

but they become very dangerous when the line breaks and the wire is exposed and is no

longer separated from other things by insulation. Practical resistors have a

series inductance and a small parallel capacitance; these specifications can be important in

high-frequency applications. In a low-noise amplifier or pre-amp, the noise 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 characterized according



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.

FIGURE 5.7: RESISTORS

5.4 CAPACITOR

A capacitor (formerly known as condenser) is a device for storing electric charge. It

commonly consists of wire leads attached to two sheets of metal foil, separated by

insulating film, rolled into a tube.

FIGURE 5.8: CIRCUIT SYMBOL OF CAPACITOR

Capacitors are widely used in electronic circuits for blocking direct current while

allowing alternating current to pass, in filter networks, for smoothing the output of power

supplies, in the resonant circuits that tune radios to particular frequencies and for many

other purposes. A capacitor is a passive electronic component consisting of a pair of

conductors separated by a dielectric (insulator). When there is a potential difference

(voltage) across the conductors, a static electric field develops in the dielectric that stores

energy and produces a mechanical force between the conductors. An ideal capacitor is


http://en.wikipedia.org/wiki/Energy

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http://en.wikipedia.org/wiki/Electronic_component

http://en.wikipedia.org/wiki/Passivity_(engineering)

http://en.wikipedia.org/wiki/Frequency

http://en.wikipedia.org/wiki/LC_circuit

http://en.wikipedia.org/wiki/Power_supply



characterized by a single constant value, capacitance, measured in farads. This is the ratio of

the electric charge on each conductor to the potential difference between them.

The capacitance is greatest when there is a narrow separation between large areas of

conductor; hence capacitor conductors are often called "plates", referring to an early means

of construction. In practice the dielectric between the plates passes a small amount of

leakage current and also has an electric field strength limit, resulting in a breakdown

voltage, while the conductors and leads introduce an undesired inductance and resistance.

The capacitance of certain capacitors decreases as the component ages. In ceramic

capacitors, this is caused by degradation of the dielectric. The type of dielectric and the

ambient operating and storage temperatures are the most significant aging factors, while the

operating voltage has a smaller effect. The aging process may be reversed by heating the

component above the Curie point. Aging is fastest near the beginning of life of the

component, and the device stabilizes over time. Electrolytic capacitors age as the electrolyte

evaporates. In contrast with ceramic capacitors, this occurs towards the end of life of the

component.

FIGURE 5.9: CAPACITOR

5.5. POTENTIOMETER

A potentiometer (colloquially known as a "pot") is a three-terminal resistor with a sliding

contact that forms an adjustable voltage divider. If only two terminals are used (one side

and the wiper), it acts as a variable resistor or rheostat. Potentiometers are commonly used


http://en.wikipedia.org/wiki/Voltage_divider

http://en.wikipedia.org/wiki/Resistor

http://en.wikipedia.org/wiki/Terminal_(electronics)

http://en.wikipedia.org/wiki/Electrolytic_capacitor#Electrical_behavior_of_electrolytics

http://en.wikipedia.org/wiki/Electrolytic_capacitor#Electrical_behavior_of_electrolytics

http://en.wikipedia.org/wiki/Curie_point

http://en.wikipedia.org/wiki/Equivalent_series_resistance

http://en.wikipedia.org/wiki/Equivalent_series_inductance

http://en.wikipedia.org/wiki/Lead_(electronics)

http://en.wikipedia.org/wiki/Breakdown_voltage

http://en.wikipedia.org/wiki/Breakdown_voltage

http://en.wikipedia.org/wiki/Leakage_(electronics)

http://en.wikipedia.org/wiki/Electric_charge

http://en.wikipedia.org/wiki/Farad

http://en.wikipedia.org/wiki/Capacitance

http://upload.wikimedia.org/wikipedia/commons/3/31/Condensador_electrolitico_150_microF_400V.jpg


to control electrical devices such as volume controls on audio equipment. Potentiometers

operated by a mechanism can be used as position transducers, for example, in a joystick.

FIGURE 5.10: POTENTIOMETERS

Potentiometers are rarely used to directly control significant power (more than a watt), since

the power dissipated in the potentiometer would be comparable to the power in the

controlled load (see infinite switch). Instead they are used to adjust the level of analog

signals (e.g. volume controls on audio equipment), and as control inputs for electronic

circuits. For example, a light dimmer uses a potentiometer to control the switching of a

TRIAC and so indirectly control the brightness of lamps.

5.6 VOLTAGE REGULATOR

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

voltage level. A voltage regulator may be a simple "feed-forward" design or may include

negative feedback control loops. It may use an electromechanical mechanism, or electronic

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

voltages.

Electronic voltage regulators are found in devices such as computer power supplies

where they stabilize the DC voltages used by the processor and other elements. In

automobile alternators and central power station generator plants, voltage regulators control

the output of the plant. In an electric power distribution system, voltage regulators may be

installed at a substation or along distribution lines so that all customers receive steady

voltage independent of how much power is drawn from the line.


http://en.wikipedia.org/wiki/Electric_power_distribution

http://en.wikipedia.org/wiki/Power_station

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http://en.wikipedia.org/wiki/Direct_current

http://en.wikipedia.org/wiki/Alternating_current

http://en.wikipedia.org/wiki/Mechanism_(technology)

http://en.wikipedia.org/wiki/Control_theory

http://en.wikipedia.org/wiki/Negative_feedback

http://en.wikipedia.org/wiki/Voltage

http://en.wikipedia.org/wiki/Regulator_(automatic_control)

http://en.wikipedia.org/wiki/Electricity

http://en.wikipedia.org/wiki/TRIAC

http://en.wikipedia.org/wiki/Dimmer

http://en.wikipedia.org/wiki/Audio_equipment

http://en.wikipedia.org/wiki/Loudness

http://en.wikipedia.org/wiki/Infinite_switch

http://en.wikipedia.org/wiki/Watt

http://en.wikipedia.org/wiki/Joystick

http://en.wikipedia.org/wiki/Transducer


Voltage Regulator (regulator), usually having three legs, converts varying input

voltage and produces a constant regulated output voltage. They are available in a variety of

outputs.

The most common part numbers start with the numbers 78 or 79 and finish with two

digits indicating the output voltage. The number 78 represents positive voltage and 79

negative one. The 78XX series of voltage regulators are designed for positive input. And the

79XX series is designed for negative input.

FIGURE 5.11: VOLTAGE REGULAOR

5.7 CRYSTAL OSCILLATOR

A crystal oscillator is an electronic oscillator circuit that uses the mechanical resonance of a

vibrating crystal of piezoelectric material to create an electrical signal with a very precise

frequency. This frequency is commonly used to keep track of time (as in quartz

wristwatches), to provide a stable clock signal for digital integrated circuits, and to stabilize

frequencies for radio transmitters and receivers. The most common type of piezoelectric

resonator used is the quartz crystal, so oscillator circuits designed around them became

known as "crystal oscillators."

Quartz crystals are manufactured for frequencies from a few tens of kilohertz to tens

of megahertz. More than two billion (2×109) crystals are manufactured annually. Most are

used for consumer devices such as wristwatches, clocks, radios, computers, and cell phones.


http://en.wikipedia.org/wiki/Cellphone

http://en.wikipedia.org/wiki/Computer

http://en.wikipedia.org/wiki/Radio

http://en.wikipedia.org/wiki/Clock

http://en.wikipedia.org/wiki/Wristwatch

http://en.wikipedia.org/wiki/Kilohertz

http://en.wikipedia.org/wiki/Quartz_crystal

http://en.wikipedia.org/wiki/Radio_receiver

http://en.wikipedia.org/wiki/Radio_transmitter

http://en.wikipedia.org/wiki/Integrated_circuits

http://en.wikipedia.org/wiki/Digital

http://en.wikipedia.org/wiki/Clock_signal

http://en.wikipedia.org/wiki/Quartz_clock

http://en.wikipedia.org/wiki/Quartz_clock

http://en.wikipedia.org/wiki/Frequency

http://en.wikipedia.org/wiki/Piezoelectricity#Materials

http://en.wikipedia.org/wiki/Crystal

http://en.wikipedia.org/wiki/Resonance

http://en.wikipedia.org/wiki/Electronic_oscillator


Quartz crystals are also found inside test and measurement equipment, such as counters,

signal generators, and oscilloscopes.

FIGURE 5.12: CRYSTAL OSCILLATOR

5.7.1 Operation

A crystal is a solid in which the constituent atoms, molecules, or ions are packed in a

regularly ordered, repeating pattern extending in all three spatial dimensions.

Almost any object made of an elastic material could be used like a crystal, with appropriate

transducers, since all objects have natural resonant frequencies of vibration. For example,

steel is very elastic and has a high speed of sound.

It was often used in mechanical filters before quartz. The resonant frequency

depends on size, shape, elasticity, and the speed of sound in the material. High-frequency

crystals are typically cut in the shape of a simple, rectangular plate. Low-frequency crystals,

such as those used in digital watches, are typically cut in the shape of a tuning fork. For

applications not needing very precise timing, a low-cost ceramic resonator is often used in

place of a quartz crystal.

When a crystal of quartz is properly cut and mounted, it can be made to distort in an

electric field by applying a voltage to an electrode near or on the crystal. This property is

known as piezoelectricity. When the field is removed, the quartz will generate an electric

field as it returns to its previous shape, and this can generate a voltage. The result is that a

quartz crystal behaves like a circuit composed of an inductor, capacitor and resistor, with a

precise resonant frequency.


http://en.wikipedia.org/wiki/Resistor

http://en.wikipedia.org/wiki/Capacitor

http://en.wikipedia.org/wiki/Inductor

http://en.wikipedia.org/wiki/Piezoelectricity

http://en.wikipedia.org/wiki/Electrode

http://en.wikipedia.org/wiki/Voltage


http://en.wikipedia.org/wiki/Quartz

http://en.wikipedia.org/wiki/Ceramic_resonator

http://en.wikipedia.org/wiki/Tuning_fork

http://en.wikipedia.org/wiki/Speed_of_sound

http://en.wikipedia.org/wiki/Elasticity_(physics)

http://en.wikipedia.org/wiki/Mechanical_filter

http://en.wikipedia.org/wiki/Steel

http://en.wikipedia.org/wiki/Vibration

http://en.wikipedia.org/wiki/Resonance


http://en.wikipedia.org/wiki/Elasticity_(physics)

http://en.wikipedia.org/wiki/Ion

http://en.wikipedia.org/wiki/Molecule

http://en.wikipedia.org/wiki/Atom

http://en.wikipedia.org/wiki/Solid

http://en.wikipedia.org/wiki/Crystal

http://en.wikipedia.org/wiki/Oscilloscope

http://en.wikipedia.org/wiki/Signal_generator

http://en.wikipedia.org/wiki/File:RC_radio_crystal.jpg


Quartz has the further advantage that its elastic constants and its size change in such

a way that the frequency dependence on temperature can be very low. The specific

characteristics will depend on the mode of vibration and the angle at which the quartz is cut

(relative to its crystallographic axe). Therefore, the resonant frequency of the plate, which

depends on its size, will not change much, either. This means that a quartz clock, filter or

oscillator will remain accurate. For critical applications the quartz oscillator is mounted in a

temperature-controlled container, called a crystal oven, and can also be mounted on shock

absorbers to prevent perturbation by external mechanical vibrations.

5.7.2 Commonly used crystal frequencies

Crystal oscillator circuits are often designed around relatively few standard frequencies,

such as 3.579545 MHz, 4.433619 MHz, 10 MHz, 14.318182 MHz, 17.734475 MHz,

20 MHz, 33.33 MHz, and 40 MHz The popularity of the 3.579545 MHz crystals is due to

low cost since they are used for NTSC colour television receivers. Using frequency

dividers, frequency multipliers and phase locked loop circuits; it is practical to derive a

wide range of frequencies from one reference frequency. 14.318182 MHz (four times

3.579545 MHz) is used in computer video displays to generate a bitmapped video display

for NTSC colour monitors, such as the CGA used with the original IBM PC. (The IBM PC

used 14.318182 MHz, divided by three, as its 4.77 MHz clock source, using one crystal for

two purposes.) The 4.433619 MHz and 17.734475 MHz values are used in PAL colour

television equipment and devices intended to produce PAL signals.

Crystals can be manufactured for oscillation over a wide range of frequencies, from

a few kilohertz up to several hundred megahertz. Many applications call for a crystal

oscillator frequency conveniently related to some other desired frequency, so hundreds of

standard crystal frequencies are made in large quantities and stocked by electronics

distributors.

5.8 LCD (LIQUID CRYSTAL DISPLAY)

A liquid crystal display (LCD) is a thin, flat electronic visual display that uses the light

modulating properties of liquid crystals (LCs). LCs does not emit light directly. They are

used in a wide range of applications, including computer monitors, television, instrument


http://en.wikipedia.org/wiki/Television

http://en.wikipedia.org/wiki/Computer_monitor

http://en.wikipedia.org/wiki/Liquid_Crystals

http://en.wikipedia.org/wiki/Electronic_visual_display

http://en.wikipedia.org/wiki/PAL

http://en.wikipedia.org/wiki/IBM_PC

http://en.wikipedia.org/wiki/Color_Graphics_Adapter

http://en.wikipedia.org/wiki/Bitmap

http://en.wikipedia.org/wiki/Phase_locked_loop

http://en.wikipedia.org/wiki/Frequency_multiplier

http://en.wikipedia.org/wiki/Frequency_divider

http://en.wikipedia.org/wiki/Frequency_divider

http://en.wikipedia.org/wiki/Television

http://en.wikipedia.org/wiki/NTSC

http://en.wikipedia.org/wiki/Crystal_oven


panels, aircraft cockpit displays, signage, etc. They are common in consumer devices such

as video players, gaming devices, clocks, watches, calculators, and telephones. LCDs have

displaced cathode ray tube (CRT) displays in most applications. They are usually more

compact, lightweight, portable, less expensive, more reliable, and easier on the eyes. They

are available in a wider range of screen sizes than CRT and plasma displays, and since they

do not use phosphors, they cannot suffer image burn-in.

LCDs are more energy efficient and offer safer disposal than CRTs. Its low

electrical power consumption enables it to be used in battery-powered electronic equipment.

It is an electronically-modulated optical device made up of any number of pixels filled with

liquid crystals and arrayed in front of a light source (backlight) or reflector to produce

images in colour or monochrome. The earliest discovery leading to the development of

LCD technology, the discovery of liquid crystals, dates from 1888. By 2008, worldwide

sales of televisions with LCD screens had surpassed the sale of CRT units.

Each pixel of an LCD typically consists of a layer of molecules aligned between two

transparent electrodes, and two polarizing filters, the axes of transmission of which are (in

most of the cases) perpendicular to each other. With no actual liquid crystal between the

polarizing filters, light passing through the first filter would be blocked by the second

(crossed) polarizer. In most of the cases the liquid crystal has double refraction.

The surfaces of the electrodes that are in contact with the liquid crystal material are

treated so as to align the liquid crystal molecules in a particular direction. This treatment

typically consists of a thin polymer layer that is unidirectional rubbed using, for example, a

cloth. The direction of the liquid crystal alignment is then defined by the direction of

rubbing. Electrodes are made of a transparent conductor called Indium Tin Oxide (ITO).

Before applying an electric field, the orientation of the liquid crystal molecules is

determined by the alignment at the surfaces of electrodes. In a twisted nematic device (still

the most common liquid crystal device), the surface alignment directions at the two

electrodes are perpendicular to each other, and so the molecules arrange themselves in a

helical structure, or twist. This reduces the rotation of the polarization of the incident light,

and the device appears grey. If the applied voltage is large enough, the liquid crystal

molecules in the centre of the layer are almost completely untwisted and the polarization of


http://en.wikipedia.org/wiki/Grey

http://en.wikipedia.org/wiki/Helix


http://en.wikipedia.org/wiki/Indium_Tin_Oxide

http://en.wikipedia.org/wiki/Polymer

http://en.wikipedia.org/wiki/Double_refraction

http://en.wikipedia.org/wiki/Liquid_crystal

http://en.wikipedia.org/wiki/Light


http://en.wikipedia.org/wiki/Filter_(optics)

http://en.wikipedia.org/wiki/Polarizer


http://en.wikipedia.org/wiki/Transparency_(optics)

http://en.wikipedia.org/wiki/Molecule

http://en.wikipedia.org/wiki/Pixel

http://en.wikipedia.org/wiki/Monochrome

http://en.wikipedia.org/wiki/Reflector_(photography)

http://en.wikipedia.org/wiki/Backlight

http://en.wikipedia.org/wiki/Light#Light_sources



http://en.wikipedia.org/wiki/Electro-optic_modulator

http://en.wikipedia.org/wiki/Electronics

http://en.wikipedia.org/wiki/Battery_(electricity)

http://en.wikipedia.org/wiki/Plasma_display

http://en.wikipedia.org/wiki/Cathode_ray_tube

http://en.wikipedia.org/wiki/Telephone

http://en.wikipedia.org/wiki/Calculator

http://en.wikipedia.org/wiki/Clock

http://en.wikipedia.org/wiki/Signage

http://en.wikipedia.org/wiki/Flight_instruments


the incident light is not rotated as it passes through the liquid crystal layer. This light will

then be mainly polarized perpendicular to the second filter, and thus be blocked and the

pixel will appear black. By controlling the voltage applied across the liquid crystal layer in

each pixel, light can be allowed to pass through in varying amounts thus constituting

different levels of gray. This electric field also controls (reduces) the double refraction

properties of the liquid crystal.

The optical effect of a twisted nematic device in the voltage-on state is far less

dependent on variations in the device thickness than that in the voltage-off state. Because of

this, these devices are usually operated between crossed polarizers such that they appear

bright with no voltage (the eye is much more sensitive to variations in the dark state than

the bright state). These devices can also be operated between parallel polarizers, in which

case the bright and dark states are reversed. The voltage-off dark state in this configuration

appears blotchy, however, because of small variations of thickness across the device.

Both the liquid crystal material and the alignment layer material contain ionic

compounds. If an electric field of one particular polarity is applied for a long period of time

this ionic material is attracted to the surfaces and degrades the device performance. This is

avoided either by applying an alternating current or by reversing the polarity of the electric

field as the device is addressed (the response of the liquid crystal layer is identical,

regardless of the polarity of the applied field).

When a large number of pixels are needed in a display, it is not technically possible

to drive each directly since then each pixel would require independent electrodes. Instead,

the display is multiplexed. In a multiplexed display, electrodes on one side of the display

are grouped and wired together (typically in columns), and each group gets its own voltage

source. On the other side, the electrodes are also grouped (typically in rows), with each

group getting a voltage sink. The groups are designed so each pixel has a unique, unshared

combination of source and sink. The electronics or the software driving the electronics then

turns on sinks in sequence, and drives sources for the pixels of each sink.


http://en.wikipedia.org/wiki/Voltage_source

http://en.wikipedia.org/wiki/Voltage_source

http://en.wikipedia.org/wiki/Multiplexer


http://en.wikipedia.org/wiki/Ionic_compound

http://en.wikipedia.org/wiki/Ionic_compound


http://en.wikipedia.org/wiki/Double_refraction


http://en.wikipedia.org/wiki/Black


http://en.wikipedia.org/wiki/Perpendicular

http://en.wikipedia.org/wiki/Incident_light


FIGURE 5.13: LCD

5.8.1 Applications LCD have been adopted by the United States of America military instead of CRT displays

because they are smaller, lighter and more efficient, although monochrome plasma displays

are also used, notably for their M1 Abram’s tanks. For use with night vision imaging

systems a US military LCD monitor must be compliant with MIL-L-3009 (formerly MIL-L-

85762A). These LCD monitors go through extensive certification so that they pass the

standards for the military. These include MIL-STD-901D - High Shock (Sea Vessels), MIL-

STD-167B - Vibration (Sea Vessels), MIL-STD-810F–Field Environmental Conditions

(Ground Vehicles and Systems), MIL-STD-461E/F–EMI/RFI (Electromagnetic

Interference/Radio Frequency Interference), MIL-STD-740B – Airborne/Structure borne

Noise, and TEMPEST-Telecommunications Electronics Material Protected from Emanating

Spurious Transmissions.

5.9 BUZZER

FIGURE 5.14: BUZZER


http://en.wikipedia.org/wiki/Cathode_ray_tube

http://en.wikipedia.org/wiki/File:LCD_display_16x2_alphanumeric.jpg

http://www.futurlec.com/Buzzers_PCB_Mount.shtml%00%E5%A1%B9%EF%92%81%E1%B4%BB%E4%A1%BF%E2%B2%AF%E5%B6%82%E8%97%84%E6%8C%A7%00%00%EA%AE%A5


A buzzer or beeper is an audio signalling device, which may be mechanical,

electromechanical, or piezoelectric. Typical uses of buzzers and beepers include alarms,

timers and confirmation of user input such as a mouse click or keystroke.

Mechanical

A joy buzzer is an example of a purely mechanical buzzer.

Electromechanical

Early devices were based on an electromechanical system identical to an electric bell

without the metal gong. Similarly, a relay may be connected to interrupt its own actuating

current, causing the contacts to buzz. Often these units were anchored to a wall or ceiling to

use it as a sounding board. The word "buzzer" comes from the rasping noise that

electromechanical buzzers made.

Piezoelectric

A piezoelectric element may be driven by an oscillating electronic circuit or other audio

signal source, driven with a piezoelectric audio amplifier. Sounds commonly used to

indicate that a button has been pressed are a click, a ring or a beep.

FIGURE 5.15: PIEZOELECTRIC DISC BEEPER

5.9.1 Uses Annunciator panels

Electronic metronomes

Game shows


http://en.wikipedia.org/wiki/Game_show

http://en.wikipedia.org/wiki/Metronome

http://en.wikipedia.org/wiki/Annunciator_panel

http://en.wikipedia.org/wiki/Piezoelectric_audio_amplifier

http://en.wikipedia.org/wiki/Audio_signal

http://en.wikipedia.org/wiki/Audio_signal

http://en.wikipedia.org/wiki/Oscillation

http://en.wikipedia.org/wiki/Switch

http://en.wikipedia.org/wiki/Electric_current

http://en.wikipedia.org/wiki/Relay

http://en.wikipedia.org/wiki/Electric_bell

http://en.wikipedia.org/wiki/Joy_buzzer

http://en.wikipedia.org/wiki/Timer

http://en.wikipedia.org/wiki/Alarm

http://en.wikipedia.org/wiki/Piezoelectric

http://en.wikipedia.org/wiki/Electromechanics

http://en.wikipedia.org/wiki/Machine

http://en.wikipedia.org/wiki/Sound

http://en.wikipedia.org/wiki/File:2007-07-24_Piezoelectric_buzzer.jpg


Microwave ovens and other household appliances

Sporting events such as basketball games

5.10 SWITCHES

FIGURE 5.16: DIFFERENT TYPES OF SWITCHES

Switch is an electrical component that can break an electrical circuit, interrupting the

current or diverting it from one conductor to another. The most familiar form of switch is a

manually operated electromechanical device with one or more sets of electrical contacts.

Each set of contacts can be in one of two states: either 'closed' meaning the contacts are

touching and electricity can flow between them, or 'open', meaning the contacts are

separated and non conducting.

A switch may be directly manipulated by a human as a control signal to a system,

such as a computer keyboard button, or to control power flow in a circuit, such as a light

switch. Automatically-operated switches can be used to control the motions of machines,

for example, to indicate that a garage door has reached its full open position or that a

machine tool is in a position to accept another work piece. Switches may be operated by

process variables such as pressure, temperature, flow, current, voltage, and force, acting as

sensors in a process and used to automatically control a system. For example, a thermostat

is a temperature-operated switch used to control a heating process.


http://en.wikipedia.org/wiki/Thermostat

http://en.wikipedia.org/wiki/Sensor

http://en.wikipedia.org/wiki/Light_switch

http://en.wikipedia.org/wiki/Light_switch

http://en.wikipedia.org/wiki/Electrical_contact

http://en.wikipedia.org/wiki/Electromechanical


http://en.wikipedia.org/wiki/Electrical_circuit

http://en.wikipedia.org/wiki/Electrical_component

http://en.wikipedia.org/wiki/Basketball

http://en.wikipedia.org/wiki/Sport

http://en.wikipedia.org/wiki/Major_appliance

http://en.wikipedia.org/wiki/Microwave_oven

http://en.wikipedia.org/wiki/File:Tactile_switches.jpg


A switch that is operated by another electrical circuit is called a relay. Large

switches may be remotely operated by a motor drive mechanism. Some switches are used to

isolate electric power from a system, providing a visible point of isolation that can be pad-

locked if necessary to prevent accidental operation of a machine during maintenance, or to

prevent electric shock.

5.11 DIODE

Diodes were the first semiconductor electronic devices. The discovery of crystals' rectifying

abilities was made by German physicist Ferdinand Braun in 1874. The first semiconductor

diodes, called cat's whisker diodes, developed around 1906, were made of mineral crystals

such as galena. Today most diodes are made of silicon, but other semiconductors such as

germanium are sometimes used.

In electronics, a diode is a two-terminal electronic component that conducts electric

current in only one direction. The term usually refers to a semiconductor diode, the most

common type today. This is a crystalline piece of semiconductor material connected to two

electrical terminals. A vacuum tube diode (now little used except in some high-power

technologies) is a vacuum tube with two electrodes: a plate and a cathode.

The most common function of a diode is to allow an electric current to pass in one

direction (called the diode's forward direction) while blocking current in the opposite

direction (the reverse direction). Thus, the diode can be thought of as an electronic version

of a check valve. This unidirectional behaviour is called rectification, and is used to convert

alternating current to direct current, and to extract modulation from radio signals in radio

receivers.

However, diodes can have more complicated behaviour than this simple on-off

action. This is due to their complex non-linear electrical characteristics, which can be

tailored by varying the construction of their P-N junction. These are exploited in special

purpose diodes that perform many different functions. For example, specialized diodes are

used to regulate voltage (Zener diodes), to electronically tune radio and TV receivers

(varactor diodes), to generate radio frequency oscillations (tunnel diodes), and to produce

light (light emitting diodes). Tunnel diodes exhibit negative resistance, which makes them

useful in some types of circuits.


http://en.wikipedia.org/wiki/Negative_resistance

http://en.wikipedia.org/wiki/Light_emitting_diode

http://en.wikipedia.org/wiki/Tunnel_diode

http://en.wikipedia.org/wiki/Oscillation

http://en.wikipedia.org/wiki/Radio_frequency

http://en.wikipedia.org/wiki/Varactor_diode

http://en.wikipedia.org/wiki/Zener_diode

http://en.wikipedia.org/wiki/P-N_junction

http://en.wikipedia.org/wiki/Non-linear

http://en.wikipedia.org/wiki/Modulation



http://en.wikipedia.org/wiki/Rectification_(electricity)

http://en.wikipedia.org/wiki/Check_valve

http://en.wikipedia.org/wiki/Cathode

http://en.wikipedia.org/wiki/Plate_electrode


http://en.wikipedia.org/wiki/Vacuum_tube

http://en.wikipedia.org/wiki/Semiconductor



http://en.wikipedia.org/wiki/Electronic_component

http://en.wikipedia.org/wiki/Terminal_(electronics)


http://en.wikipedia.org/wiki/Germanium


http://en.wikipedia.org/wiki/Silicon

http://en.wikipedia.org/wiki/Galena

http://en.wikipedia.org/wiki/Cat's_whisker_diode

http://en.wikipedia.org/wiki/Ferdinand_Braun

http://en.wikipedia.org/wiki/Rectification_(electricity)

http://en.wikipedia.org/wiki/Semiconductor_device



FIGURE 5.17: DIODE

5.11.1 Semiconductor diodes

FIGURE 5.18: TYPICAL DIODE SYMBOLS AND CODES

A modern semiconductor diode is made of a crystal of semiconductor like silicon that has

impurities added to it to create a region on one side that contains negative charge carriers

(electrons), called n-type semiconductor, and a region on the other side that contains

positive charge carriers (holes), called p-type semiconductor. The diode's terminals are

attached to each of these regions. The boundary within the crystal between these two

regions, called a PN junction, is where the action of the diode takes place. The crystal

conducts a current of electrons in a direction from the N-type side (called the cathode) to the

P-type side (called the anode), but not in the opposite direction; that is, a conventional

current flows from anode to cathode (opposite to the electron flow, since electrons have

negative charge).


http://en.wikipedia.org/wiki/Anode

http://en.wikipedia.org/wiki/Cathode

http://en.wikipedia.org/wiki/PN_junction

http://en.wikipedia.org/wiki/P-type_semiconductor

http://en.wikipedia.org/wiki/Electron_hole

http://en.wikipedia.org/wiki/N-type_semiconductor

http://en.wikipedia.org/wiki/Charge_carrier


http://en.wikipedia.org/wiki/File:Diode-closeup.jpg

http://en.wikipedia.org/wiki/File:Diode_3D_and_ckt.png


Another type of semiconductor diode, the Schottky diode, is formed from the

contact between a metal and a semiconductor rather than by a p-n junction.

5.11.2 Applications

1. Radio demodulation

The first use for the diode was the demodulation of amplitude modulated (AM) radio

broadcasts. The history of this discovery is treated in depth in the radio article. In summary,

an AM signal consists of alternating positive and negative peaks of voltage, whose

amplitude or “envelope” is proportional to the original audio signal. The diode (originally a

crystal diode) rectifies the AM radio frequency signal, leaving an audio signal which is the

original audio signal, minus atmospheric noise. The audio is extracted using a simple filter

and fed into an audio amplifier or transducer, which generates sound waves.

2. Power conversion

Rectifiers are constructed from diodes, where they are used to convert alternating current

(AC) electricity into direct current (DC). Automotive alternators are a common example,

where the diode, which rectifies the AC into DC, provides better performance than the

commutator of earlier dynamo. Similarly, diodes are also used in Cockcroft–Walton voltage

multipliers to convert AC into higher DC voltages.

3. Over-voltage protection

Diodes are frequently used to conduct damaging high voltages away from sensitive

electronic devices. They are usually reverse-biased (non-conducting) under normal

circumstances. When the voltage rises above the normal range, the diodes become forward-

biased (conducting). For example, diodes are used in (stepper motor and H-bridge) motor

controller and relay circuits to de-energize coils rapidly without the damaging voltage

spikes that would otherwise occur. (Any diode used in such an application is called a

flyback diode). Many integrated circuits also incorporate diodes on the connection pins to

prevent external voltages from damaging their sensitive transistors. Specialized diodes are

used to protect from over-voltages at higher power (see Diode types above).


http://en.wikipedia.org/wiki/Diode#Types_of_semiconductor_diode

http://en.wikipedia.org/wiki/Transistors

http://en.wikipedia.org/wiki/Integrated_circuits

http://en.wikipedia.org/wiki/Flyback_diode

http://en.wikipedia.org/wiki/Voltage_spike

http://en.wikipedia.org/wiki/Voltage_spike


http://en.wikipedia.org/wiki/Motor_controller

http://en.wikipedia.org/wiki/Motor_controller

http://en.wikipedia.org/wiki/H-bridge

http://en.wikipedia.org/wiki/Stepper_motor

http://en.wikipedia.org/wiki/Voltage_multiplier

http://en.wikipedia.org/wiki/Voltage_multiplier

http://en.wikipedia.org/wiki/Cockcroft-Walton_generator

http://en.wikipedia.org/wiki/Electrical_generator

http://en.wikipedia.org/wiki/Commutator_(electric)

http://en.wikipedia.org/wiki/Alternator_(auto)



http://en.wikipedia.org/wiki/Rectifier


http://en.wikipedia.org/wiki/Electronic_filter

http://en.wikipedia.org/wiki/Rectifier

http://en.wikipedia.org/wiki/Amplitude

http://en.wikipedia.org/wiki/Radio

http://en.wikipedia.org/wiki/Amplitude_modulation

http://en.wikipedia.org/wiki/Schottky_diode


4. Logic gates

Diodes can be combined with other components to construct AND & OR logic gates. This

is referred to as diode logic.

5. Ionizing radiation detectors

In addition to light, mentioned above, semiconductor diodes are sensitive to more energetic

radiation. In electronics, cosmic rays and other sources of ionizing radiation cause noise

pulses and single and multiple bit errors. This effect is sometimes exploited by particle

detectors to detect radiation. A single particle of radiation, with thousands or millions of

electron volts of energy, generates many charge carrier pairs, as its energy is deposited in

the semiconductor material. If the depletion layer is large enough to catch the whole shower

or to stop a heavy particle, a fairly accurate measurement of the particle’s energy can be

made, simply by measuring the charge conducted and without the complexity of a magnetic

spectrometer or etc. These semiconductor radiation detectors need efficient and uniform

charge collection and low leakage current.

6. Temperature measurements

A diode can be used as a temperature measuring device, since the forward voltage drop

across the diode depends on temperature, as in a Silicon band gap temperature sensor. From

the Shockley ideal diode equation given above, it appears the voltage has a positive

temperature coefficient (at a constant current) but depends on doping concentration and

operating temperature (Size 2007). The temperature coefficient can be negative as in typical

thermistors or positive for temperature sense diodes down to about 20 Kelvin’s. Typically

silicon diodes have approximately −2 mV/˚C temperature coefficient at room temperature.

7. Current steering

Diodes will prevent currents in unintended directions. To supply power to an electrical

circuit during a power failure, the circuit can draw current from a battery. An

Uninterruptible power supply may use diodes in this way to ensure that current is only

drawn from the battery when necessary. Similarly, small boats typically have two circuits

each with their own battery/batteries: one used for engine starting; one used for domestics.


http://en.wikipedia.org/wiki/Uninterruptible_power_supply

http://en.wikipedia.org/wiki/Battery_(electricity)

http://en.wikipedia.org/wiki/Operating_temperature

http://en.wikipedia.org/wiki/Silicon_bandgap_temperature_sensor

http://en.wikipedia.org/wiki/Temperature

http://en.wikipedia.org/wiki/Electron_volt

http://en.wikipedia.org/wiki/Particle_detector

http://en.wikipedia.org/wiki/Particle_detector

http://en.wikipedia.org/wiki/Pulse

http://en.wikipedia.org/wiki/Noise

http://en.wikipedia.org/wiki/Cosmic_ray


http://en.wikipedia.org/wiki/Energy


http://en.wikipedia.org/wiki/Diode_logic

http://en.wikipedia.org/wiki/Logic_gate

http://en.wikipedia.org/wiki/Logical_disjunction

http://en.wikipedia.org/wiki/Logical_conjunction


Normally both are charged from a single alternator, and a heavy duty split charge diode is

used to prevent the higher charge battery (typically the engine battery) from discharging

through the lower charged battery when the alternator is not running.

5.12 HEX KEYPAD

The hex keypad is a peripheral that connects to the DE2 through JP1 or JP2 via a 40-pin

ribbon cable. It has 16 buttons in a 4 by 4 grid, labelled with the hexadecimal digits 0 to F.

Internally, the structure of the hex keypad is very simple. Wires run in vertical columns (we

call them C0 to C3) and in horizontal rows (called R0 to R3). These 8 wires are available

externally, and will be connected to the lower 8 bits of the port. Each key on the keypad is

essentially a switch that connects a row wire to a column wire. When a key is pressed, it

makes an electrical connection between the row and column. The specific mapping of hex

keypad wires (C0 to C3 and R0 to R3) to pins is given below:-

FIGURE 5.19: SCHEMATICS OF HEX KEYPAD



FIGURE 5.20: HEX INPUTS

5.13 ELECTROMAGNETIC LOCK

An electromagnetic lock is a device used to control the access through a door. It consists of

an electromagnet mounted in or on the door frame and a matching plate that is affixed to the

door. When energized, the electromagnet holds the plate with a retention force that may

exceed 1000 lbs., thus effectively locking the door. They are typically controlled through

security systems, keypads, key switches, card access systems, “request to exit” buttons,

and/or by special devices worn by persons whose safety could be compromised by

uncontrolled egress.

In order to prevent unauthorized egress, one option would be the use of alarms that

are activated when the door is opened, or other similar means that permit free egress under

emergency conditions, while discouraging unauthorized use of the door. Where it is desired

to prevent unauthorized entry, the use of an electric strike is an acceptable option, providing

that the door is manually openable in the direction of exit travel through a latch that is

mechanically linked to the door handle, lever, push bar, etc.

Electromagnetic locks that do not incorporate latches, pins or other similar devices

to keep the door in the closed position are permitted to be installed on exit doors other than

doors leading directly from a high hazard industrial occupancy, provided:-



a) The building is equipped with a fire alarm system.

b) The locking device, and all similar devices in the access to exit leading to the exit door,

release upon actuation of the fire alarm signal.

c) the locking device releases immediately upon loss of power controlling the

electromagnetic locking mechanism and its associated auxiliary controls.

d) the locking device releases immediately upon actuation of a manually operated switch

readily accessible only to authorized personnel.



CHAPTER 6

SOFTWARE USED AND FLOW CHART OF PROGRAM

6.1 INTRODUCTION

We are using TopView Simulator for designing and testing of the embedded c code for Real

Time Control (RTC), Counter, Timer, 8051 microcontroller and LCD display coding and

simulation.

Topview Simulator gives an excellent simulation environment for the industry's

most popular 8 bit Microcontroller family, MCS 51. It gives required facilities to enable the

system designers to start projects right from the scratch and finish them with ease and

confidence.

FIGURE 6.1: ARCITERCTURE OF TOPVIEW SIMULATOR



6.2 FEATURES OF TOP VIEW SIMULATOR

6.2.1 Device Selection

A wide range of device selection, including Generic 8031 devices and Atmel's AT89CXX

series 8051 microcontrollers.

6.2.2 Program Editing

Powerful editing feature for generating your programs both in C and Assembly level and the

facility to call an external Compiler / Assembler (Keil / SDCC Compilers) to process input

programs.

6.2.3 Clear View

Clearview facility gives all the internal architectural details in multiple windows.

Information about the Program, Data Memory, register, peripherals, SFR bits are clearly

presented in many windows to make you understand the program flow very easily.

6.2.4 Program Execution

A variety of program execution options including Single Stroke full speed execution, Single

Step, Step Over and Breakpoint execution modes give you total control over the target

program. Clearview updates all the windows with the correct and latest data and it is a

convenient help during your debugging operations.

6.2.5 Simulation Facilities

Powerful simulation facilities are incorporated for I/O lines, Interrupt lines, Clocks meant

for Timers / Counters.

Many external interfacing possibilities can be simulated:

Range of Plain Point LEDs and Seven Segment LED options.

LCD modules in many configurations.



Momentary ON keys.

A variety of keypads upto 4 X 8 key matrix.

Toggle switches.

All modes of onchip serial port communication facility.

I2C components including RTC, EEPROMs.

SPI Bus based EEPROM devices.

6.2.6 Code Generation Facilities

Powerful and versatile Code Generating facility enables you to generate the exact and

compact assembly code / C Source code for many possible application oriented interfacing

options.

You can simply define your exact needs and get the target assembly code / C Source

code at a press of button at anywhere in your program flow. The code gets embedded into

your application program automatically.

You are assured of trouble free working of final code in the real time.

All modes of the serial port.

Interfacing I2C/SPI Bus devices.

Range of keypads.

Many LED/LCD interfacing possibilities.

FIGURE 6.2: TOPVIEW SIMULATOR SCREENSHOT



6.3 ALGORITHM

Step 1: Display Date and Time.

Step 2: Exam authority log in into smart box security system.

Step 3: Smart box check Log-in date and time.

Step 4: If date and time matches, initialize the user attempts else RESET the system.

Step 5: If attempts are less than or equal to 3, then ask for password or go to step 4.

Step 6: If number of attempts exceed 3, then TERMINATE the system with 5 minute delay.

Step 7: If password matches, open the smart box and distribute the papers.

Step 8: End



6.4 FLOWCHART

NO


NO

DISPLAY DATE AND TIME

INITIALLIZE ATEMPT=1

WELCOME TO SMART BOX

USER INTERRUP

T

MATCH DATE & TIME

IF ATTEMPTS <= 3

TERMINATE

X

YES

YES

YES

NO

A

ATTEMPT ++


FIGURE 6.3: PROJECT FLOW DIAGRAM


X

IF PASSWORD MATCHES

OPEN THE SMART BOX

DISPLAY “THANK YOU”

YES

A


CHAPTER 7

PROBLEMS FACED

7.1 INTRODUCTION

Project can be defined as solution to a real world problem, which has to be accomplished.

For designing the solution there are several factors to he kept in mind and each has to be

satisfied. Much observation has to be done, results have to be analyzed and better alternates

(if required) have to be explored. In the same way, we faced numerous problems in design,

test and implementation phase.

7.2 DESIGN PHASE PROBLEMS

7.2.1 Algorithm Designing

An Algorithm defines the Working Process of the Project. There were many ideas/ways to

implement the project but most appropriate and shortest path is essential in order to

complete the project in given time. In Project algorithm designing, security was the main

concern and manual interference should be avoided. So, there is a step to step algorithm

designing starting right from user input date and time, log in, access the data, paper drop in

to the box and finally locking of the box. This was the shortest and most efficient way to

fulfill the goal of project.

7.2.2 Box Designing

In the designing of the box, structure should be compatible with paper printing and drop it

into an box. Wooden and acrylic were two options in the designing or box but we prefer the

wooden over acrylic because it is cheaper as compared to the acrylic box.

7.2.3 Process Synchronization

Another problem we have faced is synchronization of various modules with one another.

We have faced problems associated with smart box with the outer module and paper counter



module. Later on, we have sort out the problem associated with smart box synchronization

with other modules.

7.2.4 Non-Availability of RTC Chip

In Real time control selection, there were two options:-

1. DS12887 (Serial Communication)

2. DS 1307 (I2C Protocol)

DS 12887 is not available in the market. So there was no option left for us. We finally go

for DS1307 in our project having the same function but with different protocol.



CHAPTER 8

APPLICATIONS

8.1 Introduction

In present scenario, most of the examinations are conducted offline at different cities across

the globe. The existing system of exam conduction is completely manual. From the

beginning of the procedure, there is complete manual interface such as paper printing, paper

collection, distribution and finally deliver to the exam center and it increases the chances of

paper leak. One basic requirement of exam should be maintained. These should be right

time of paper printing, collection, and distribution as per exam schedule.

So, this project will be helpful to reduce the chances of examination paper leak. This

methodology can be applied in many national level exam, university and board exam

specially. This technology is helpful to reduce the government loss because there is huge

amount which is spent on conducting exam on national level.

8.2 Future ScopeTheme of our project to develop a system which can assure total security of the examination

papers, write from printing till it reaches the student/candidate (on the exam).This project

aims at creating man less printing and packaging system with time stamp based security

system for examination paper, that contain some important general life element like LAN

system, conveyer belt, printing machine, safe box etc .Safe box equipped with timer,

electromechanical lock system so that the goal of granting permission to centre authority

for opening the box after a predefined time and date can be achieved. This project also uses

a GSM modem so that information in case of any attempt to harm the box is sent a message

to the board of examination and nearest police station. This approach is planned in such way

that it would be not too much costly when manufactured in large quantity and also when

compared with loss of money arranging the exam once again. The project will helps in

removing the question mark putted on the steps taken for security available for examination

system.



8.3 Applications

The proposed outcome is Exam Paper Security System which can also be developed for

further improvements.

This project can be efficiently utilized in organizing examination of university

boards and competition level exams.

This technology is helpful to reduce the government loss because there is huge

amount which is spent on conducting exam on national level.

It will also save the time wasted because of conduction of re-examination.

If the paper is leaked then only one person is responsible for that who can be easily

caught.



CONCLUSION

In the project stage I, we have already done with the documentation part of the project and

analysis and study of various module and components that will be using in the circuit. In the

project stage II, we completed our project within stipulated time and done all the works

ranging from PCB designing to interfacing of hardware and software.

AdvantagesThe traditional exam paper printing and distribution system (manual mtheod) is having so

many loopholes and being a reason of exam paper leak. This offers a great financial loss to

the government and exam boards due to re-conduction of the exams. Students also have to

suffer from exam paper leak and time wastage due to exam re-conduction. This fact aspires

us to make a real time application which can prevent exam paper leak.

Parameter Manual Automated

Paper printing and

counting

A publisher prints and

manual counting of papers.

Using a counter for paper

counting and stop after

counting limits.

Paper distribution By different authorities. By smart box and conveyer

belt.

The centre authority will be allowed to give command. There is only single

computer which will be controlled by Exam cell in-charge. The papers will be dropped and

collected in a wooden box which is also called safe box. The box will be locked

automatically. There is a known number of copies in the box. Now, this box will be passed

to outside the room with the help of conveyer belt. The box will be collected at the window

and respective box will be distributed to the centre respectively.

Here we can observe that only one person is operating the whole process. In the

project, there is very few chances of paper leak. Even though, if it happens then only one

person is responsible and this will bring out the defaulter.



There is no human intervention in the whole process and it increases the efficiency

as well as decreases the chances of paper leak.

Limitations

1. Smart box circuitry should be monitored by the exam cell authority time to time.

2. If someone changes the data on Real Time Chip (dd/mm/yyyy) the paper can be

bring outside the scheduled date of exam and time



ANNEXURE

A1. DATA SHEETS



A2. CODING



A3. COST OF PROJECT1. Electronic Components And Devices Cost

S. No. Particulars Quantity Cost (Rs.)1. Glass PCB 1 180

2. 8051 Microcontroller 2 100

3. Crystal Oscillator (various) 4 30

4. Chip Socket (various) 5 25

5. Capacitor (various) 10 30

6. Resistor (various) 10 10

7. Push to on Switch 4 12

8. Connectors (male and female) 5 20

9. Network Resistance 2 24

10. LED 20 10

11. Positive Voltage Regulator (7805 & 7812) 4 20

12. LCD (16*2) 2 240

13. DS 1307 (RTC) 1 80

14. Hex keypad 1 240

15. Stepper Motor 2 300

16. Electromagnetic Lock 1 2000

17. Diode 4 4

18. Two Pins Connectors 6 15

Total 3340/-

2. Consumable Cost

S. No. Particulars Quantity Cost (Rs.)1. Wooden Box 1 1500

2. Report Writing & Stationary Cost 6 2100

Total 3600/-

Total Cost of Project – Rs 7000 (Approx)



REFERENCES

[1] http://www.mikroe.com/eng/chapters/view/65/chapter-2-8051-microcontroller-

architecture

[2] http://en.wikibooks.org/wiki/embedded_system/8051_Microcontroller

[3] http://www.freewebs.com/maheswakhede/lcd.html

[4] http://www.8051projects.net/lcd-interfacing

[5] http://ieeexplore.ieee.org/login.jsp?url=http%3A%2F%ieee.org

[6] http://www.engineersgarage.com/microcontroller/8051projects/interface-lcd-at89c51-

circuit

[7] http://www.botskool.com/user-pages/tutorials/electronics/2X16-lcd-and-

4X4keypadinterfacing-8051-assembly-language

[8] http://www.beyondlogic.org/parlcd/parlcd.html

[9] http://www.engineersgarage.com/sites/default/files/LCD%2016X2.pdf

[10] http://en.wikipedia.org/wiki/registers

[11] http://en.wikipedia/wiki/capacitors

[12] http://en.wikipedia.org/wiki/voltage_regulator

[13] http://en.wikipedia.org/wiki/light-emiting-diode

[14] http://www.kpsec.freeuk.com/components/led.html

[15] http://www.itl.nist.gov/iad/mig/publications/AShistory/index.html

[16] http://www.businessweek.com/1998/08/b3566022.html



BIBLIOGRAPHY

[1]. Ramakand Gayakwad, “Op-Amps and Linear Integrated Circuits”, Prentice Hall India

Publication Company.

[2]. Roy Choudhuri, “Linear Integrated Circuits”, New Age Inernational Pvt. Ltd.

[3]. J. Bannet, D.W. Price, A. Rudys, J. Singer, and D. S. Wallach, “Hack-A-Vote: Security

Box”, IEEE Security and Privacy, pg 32-37, Jan-Feb 2004.

[4]. Michel Mouly & Marie-Bernadatte Pautet, “The conveyor belt system for the box

security”, Pearson Publication.

[5]. William Stallings, “Wireless Communication”, Tata Magraw Hill Publication

[6]. Stephen ansolabehere, ”resudial security box attribute to technology,” the Caltech/Mit

box technology” Project,version 2,march 30,2001.

[7]. “The History of box technology system Evaluations at NIST”.

[8]. L.Rabiner, “A tutorial on hidden Markov models and selected applications in box

technology “ Proc. IEEE, vol. 77,pp.257-286,feb.1989.


http://www.businessweek.com/1998/08/b3566022.html

http://www.itl.nist.gov/iad/mig/publications/AShistory/index.html

http://www.kpsec.freeuk.com/components/led.html

http://en.wikipedia.org/wiki/light-emiting-diode

http://en.wikipedia.org/wiki/voltage_regulator

http://en.wikipedia/wiki/capacitors

http://en.wikipedia.org/wiki/registers

http://www.engineersgarage.com/sites/default/files/LCD%2016X2.pdf

http://www.beyondlogic.org/parlcd/parlcd.html

http://www.botskool.com/user-pages/tutorials/electronics/2X16-lcd-and-4X4keypadinterfacing-8051-assembly-language

http://www.botskool.com/user-pages/tutorials/electronics/2X16-lcd-and-4X4keypadinterfacing-8051-assembly-language

http://www.engineersgarage.com/microcontroller/8051projects/interface-lcd-at89c51-circuit

http://www.engineersgarage.com/microcontroller/8051projects/interface-lcd-at89c51-circuit

http://ieeexplore.ieee.org/login.jsp?url=http%3A%2F%25ieee.org

http://www.8051projects.net/lcd-interfacing

http://www.freewebs.com/maheswakhede/lcd.html

http://en.wikibooks.org/wiki/embedded_system/8051_Microcontroller

http://www.mikroe.com/eng/chapters/view/65/chapter-2-8051-microcontroller-architecture

http://www.mikroe.com/eng/chapters/view/65/chapter-2-8051-microcontroller-architecture

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