Braille Encoder

LIST OF FIGURES

Figure No. Name Page No.

2.1 Single Braille matrix 12

2.2 Universal Braille cell Dimensions 13

2.3 U.S. Braille Format 15

2.4 Braille Script in Tamil Language 16

2.5 Block Diagram for Speech Synthesis 19

2.6 Refreshable Braille Display 20

4.1 Block Diagram 23

4.2 Block Diagram with components 24

4.3 (a) DB9 Female connector 25

4.3 (b) DB9 Male connector 25

4.4 RS232 Cable connection 26

4.5 Front and top view of the assembly 31

4.6 Bottom view of assembly showing 32

the arrangement of solenoids

5.1 Circuit Diagram 35

13.1 Bottom side of PCB 46

13.2 Silkscreen Top 47

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Braille Encoder

1. INTRODUCTION

In this world not all people are blessed with sight. Sighted people usually get huge

amount of information from various places, or ways like graphics, diagrams, flowcharts,

graphs, logos and pictures. There are many forms of graphic communication around us.

Translating this information from graphics to tactile graphics, in the form of Braille

characters, make it accessible for the visually impaired reader which would prove to be a

boon for them.

Presently Braille books and Braille Printers are used for teaching in a blind school. But

during the teaching session the books are not available to every student at the same time.

The Braille books and printers are also expensive. The Braille Encoder can prove to be a

cost efficient solution for classroom teaching for the blind. Computer compatibility of the

Braille Encoder will ensure better learning efficiency and speed.

Thus if we try to implement the Braille Encoders in a blind school the student teacher

relationship can be maintained and the teaching can be done efficiently. The only thing

the teacher needs to do is to setup the Braille assembly for the students.

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Braille Encoder

1.1 MOTIVATION

The motivation came from an exhibition in pune a few months back, which hosted

various projects for the blind, like a stick for the blind which would sense the depth and

width of a hole in the road and a buzzer would be sounded to inform the person. Our

friend actually visited the place and gave us the idea about an electronic way of reading

for the visually impaired. Thus our friend was a great source of motivation for this

project.

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Braille Encoder

1.2 OBJECTIVE

The main aim of our project is to equip the visually impaired person to access

information from a personal computer or a laptop on his Braille 3*2 dot matrix Display.

It is used to present text to computer users who are blind and cannot use a normal

computer monitor.

The main area of interest in order to design this project is to have a cost efficient

classroom teaching for the blind people. This will facilitate a blind student to acquire the

information taught during the sessions i.e. a real time basis. A refreshable display will

ensure that the text information is loaded onto the memory of the device every time a new

session begins.

Thus it can be made cost efficient as we do not require separate books for different texts.

We just need the 3*2 display matrix & a computer. So any data can be fed in the

computer and eventually the text can be converted into Braille Code.

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Braille Encoder

1.3 SCOPE OF THE PROJECT

The scope of this project is by no means limited. The project can be implemented in any

part of the world in any language. The display matrix remains the same the only change

is the programming i.e. the data stored in the chip.

The Braille script is encoded in a 3*2 matrix immaterial of the language it is being

encoded from.

The project is a demo, thus it deals with only one Braille encoder attached to one

computer. We can extend the logic to around 30 Braille encoders attached to the same

computer. This can be done using a different serial communication (RS485) than the one

used here (RS232).

Thus if the same text has to be provided to multiple students then it surely can be done,

without the students having to queue for the same encoder.

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Braille Encoder

1.4 FEATURES

1. System is cost efficient high tech system. It promises to give a new dimension

to the classroom teaching used for the blind students.

2. A single Braille cell is used for display. The characters will be displayed in a

sequential format one after the other.

3. The Braille Encoder offers speed control for displaying the characters. The

speed can be varied depending on the experience and understanding of the

user

4. Portability is one of the main features offered by the system. This will ensure

that the blind person can carry the device wherever he goes. The device being

computer compatible can be attached to any P.C. or laptop. This is much

better than carrying large number of Braille books.

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Braille Encoder

1.5 TECHNICAL SPECIFICATION

1. Power supply

a) +5V supply for microcontroller, Max232.

b) +12V supply for ULN2803.

2. Current

Each pin of 3*2 cell array requires about 180mA at 5V. Max current

requirement is 1.08A.

3. Serial Transmission Rate

Baud rate is 2400 bps.

4. Serial Interface

The computer & the microcontroller are connected through a serial interface.

The serial interface includes the RXD, TXD and ground pins.

5. Drivers

The driver used in the project is between the controller and the Braille matrix

assembly. It protects the controller from damage.

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Braille Encoder

6. Braille Cell

The Braille cell will be a set of 6 electromagnets placed inside a box. The

pins will pop out of the box when the electromagnets are excited.

7. Display Board

The display board consists of the 6 LED’s which resemble the pins popping

out. The pin that pops and the led that glows will have the same number.

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Braille Encoder

2. LITERATURE SURVEY

2.1 HISTORY OF BRAILLE

Braille can be seen as the worlds first binary encoding scheme to represent the characters

of a writing system. This system of writing and reading used by many blind people was

invented almost 200 years ago.

The Braille system, devised in 1821 by Frenchman Louis Braille, is a method that is

widely used by blind people to read and write.

In 1821, Charles Barbier de la Serre, a former soldier, visited the school. Barbier shared

his invention called "sonography" a code of 12 raised dots and a number of dashes that let

soldiers share top-secret information on the battlefield without having to speak or use a

light, which could produce noise or light and disclose the position of soldiers.

This inspired Louis Braille, himself a blind, to come up with a Braille system at the age

of 15. His system used only six dots and corresponded to letters, whereas Barbier's used

12 dots corresponding to sounds. Louis Braille published his first book in the year 1827

under the title “Method of Writing Words, Music, and Plain Songs by Means of Dots, for

Use by the Blind and Arranged for Them” and later in 1839 Braille published details of a

method he had developed for communication with sighted people, using patterns of dots

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Braille Encoder

to approximate the shape of printed symbols. Later he even extended his system to

include notation for mathematics and music.

2.2 BRAILLE CELL

Each Braille character or cell is made up of six dot positions, arranged in a rectangle

containing two columns of three dots each. A dot may be raised at any of the six positions

to form sixty-four (26) combinations, including the combination in which no dots are

raised. The dots are conventionally numbered 1,2 and 3 from the top of the left column

and 4,5 and 6 from top of the right columns. The presence or absence of dots in the 3*2

matrix cell gives the coding for the symbol.

Fig 2.1 A single Braille Cell

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Braille Encoder

Universal Cell Dimensions

There are some important specifications used universally regarding the spacing between

the characters and words.

Dot height is approximately 0.5mm.

The horizontal and vertical spacing between dot centers within a

Braille cell is approximately 2.5mm.

The blank space between dots on adjacent cells is approximately 6-

6.4mm horizontally and 5.0mm vertically.

the spacing between two lines is 10.4-12.7mm.

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Braille Encoder

Dot base diameter is 1.4-1.5mm

Fig 2.2 Universal Braille Cell Dimensions

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Braille Encoder

2.3 REPRESENTATION OF ALPHABET AND NUMBERS

IN BRAILLE

With a 3*2 cell matrix, 64 characters can be represented in Braille format. The Braille

format that has been used is the U S computer Braille. This format is specially developed

for the use with the computers.

The small case characters (a to z) have the same Braille representation for higher case

characters (A to Z). to have a distinction a capital indicator is used before a capital

character, where 3 right side dots are raised ( dots 4,5,6).

Capital indicator

2.4 BRAILLE SCRIPT

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Braille Encoder

A K U * 1

B L V < 2

C M X % 3

D N Y ? 4

E O Z : 5

F P & $ 6

G Q = ] 7

H R ( \ 8

I S ! [ 9

J T ) W 0

@ / + . "

^ > #capitalindicator

;

' - ,

Fig 2.3 U S Braille Format

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Braille Encoder

Fig 2.4 Braille Script in Tamil Language

2.5 RECENT TACTILE SYSTEMS

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Braille Encoder

Tactile systems are the systems that are related to the sense of touch. There are several

ways to produce graphics to be read be touch – ranging from using Low-tech to High-

tech devices.

2.5.1 Low Tech Systems

1. Tailor’s notched tracing wheel is a low tech system wherein

impressions are mode on the Braille paper. A simplified drawing of the diagram is made

on the tracing paper by drawing free hand, using templates or tracing the original. Heavy

Braille paper turned face down is sandwiched between a cushion mat and the tracing also

turned face down. Using medium pressure, the lines are traced with the notched wheel

tool, leaving a trail of indented notches from the wheel. A raised design is produced and

can be felt on the right side of the Braille paper.

2. The “artsy-craftsy” approach used by many for scrap booking or

card making also works to produce tactile graphics for demonstration or instruction.

Affixed to heavy paper, almost anything with shape or contrasting texture can be used.

String, fabric, dried beans, corrugated papers or sand paper can represent continents, bar

graphs or animal shapes. This method can be messy, time-consuming and not permanent

enough for some purposes. If some of the beans fall off, the message of the graphic may

also be lost.

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Braille Encoder

3. For a more permanent graphic thermoforming technique is used.

The graphic is created with items in relief and then a heated plastic sheet is placed over

them. The plastic retains the shape of the raised portions and the page can be used over

and over again as an example in a story book, a diagram in a user’s manual or a text

book.

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Braille Encoder

2.5.2 High Tech Systems

1. Speech synthesis is a high tech system used for the conversion of spoken

words into corresponding Braille characters using speech recognition. But this

system is under development and quite expensive.

Fig2.5 Block Diagram for Speech Synthesis

2. The high tech computer method produces tactile graphics that are exact

replicas, quickly embossed, and feature 3 dimensional graphics.

3. Some of the existing Braille systems are rotating wheel Braille Display, which

are highly advanced but are costly and require an expert reader.

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Braille Encoder

4. A refreshable Braille display or Braille terminal is an electro-mechanical

device for displaying Braille characters, usually by means of raising dots

through holes in a flat surface. Blind computer users who cannot use a normal

computer monitor use it to read text output.

Fig 2.6 The Refreshable Braille display

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Braille Encoder

2.6 IMPLEMENTATION TECHNIQUES FOR PIN MOVMENT

There are a number of implementation techniques related to the movement of the pins.

1. Piezo electric effect

Certain crystals deform their shape when electric voltage is applied across them.

Pins for the raised dot display are attached to a piezo electric crystal, which deforms

when, excited thus elevating or retracing the pins.

2. Use of electromagnets

An electromagnet is placed in the vicinity of the pins. When current flow though

the electromagnet the pin is elevated or retracted.

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Braille Encoder

3. SPECIFICATIONS

1. Power Supply:

a. +5V supply for microcontroller, Max 232.

b. +5V supply for driving the ULN2803.

2. Current:

Each pin in the Braille assembly draws around 180mA current operating at 5V.

So maximum current if 6 pins are excited is 6 * 180 = 1.08A.

3. Serial Data Transmission Rate:

Baud Rate is 2400bps.

4. Character Back Tracking:

Where ever the user wishes to go.

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Braille Encoder

4. SYSTEM DESCRIPTION

4.1 Block Diagram of the project

Fig 4.1 Block Diagram

Information Source (PC)

Communication Interface

Microcontroller Driver

Braille MatrixAssembly

Power Supply

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Braille Encoder

4.1.a Block Diagram with actual components

Fig 4.2 Block Diagram with components

M I C R O C O N T R O L L E R

DRIVER(ULN2803)

BRAILLEMATRIXDISPLAY

Manual SpeedControl

Digital Switch for Automatic Control

Communication Interface(RS232)

Personal Computer

LED DISPLAY

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Braille Encoder

4.1.1 Information Source

A Personal Computer or a laptop is a source of information. The P.C. is connected to the

Braille Encoder to access the text information present on the computer. The information

to be conveyed is typed on the P.C. in the text format. The respective teacher of each

subject loads the text information on the computer from where it is transferred to the

encoder.

4.1.2 Communication Interface

The communication interface is used to connect the computer to the Braille Encoder.

(a) (b)

Fig. 4.3 (a) DB9 Female connector

(b) DB9 Male connector

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Braille Encoder

DB-9 connector of DB-9 connector of

the computer the computer

Fig 4.4 RS232 cable connection

The communication will facilitate a reliable and efficient transfer of the data from the

source to the memory of the device. A serial data communication is used as a

communication interface for data transfer. RS232 is a serial I/O interfacing standard used.

The RS232 is a cross cable which connects the transmitter of the remote information

source with the receiver of the microcontroller and vice-versa. The connection is done

through a DB-9 connector as shown above in fig 3.4 & fig 3.5

We have used only 3 wires for interfacing the controller with the computer. RXD, TXD,

GND.

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Braille Encoder

4.1.3 Selection criteria for processor

Out of the three types of known processors

a) 8086 microprocessor

b) 8051 microcontroller

c) PIC microcontroller

a) 8086 microprocessor:

The 8086 is a 16-bit microprocessor chip designed by Intel in 1978, with an

external 8-bit data bus (allowing the use of cheaper and fewer supporting logic

chips). The microprocessor contains no RAM, no ROM, and no I/O ports on chip

itself.

b) 8051 microcontroller:

The Intel 8051 is a Harvard architecture, big endian, single chip microcontroller

(µC) which was developed by Intel in 1980 for use in embedded systems.

It provides many functions (CPU, RAM, ROM, I/O, interrupt logic, timer, etc.) in

a single package.

c) PIC microcontroller:

Programmable Intelligent Computer is a family of Harvard architecture

microcontrollers. A stack cannot be implemented efficiently, so it is difficult to

generate reentrant code. It has a single working register, while RISC designs

typically include 16 or more general purpose registers.

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Braille Encoder

Thus taking the above points in consideration, we decided to use 8051

microcontroller in our implementation.

8051 MICROCONTROLLER

It is the heart of the system. The data flow within the system is controlled by the

microcontroller. When the computer sends the text information, the microcontroller

receives the data and temporarily stores that data in its memory. The microcontroller

accesses the file, character by character, and converts the character into its equivalent

Braille code using a look up table. Then the appropriate pins of the matrix display are

activated to get the character impression.

Tasks performed by the microcontroller

1. Storage of the program code.

2. Data transfer(receiving)

3. Data conversion.

4. Data storage

5. Memory management.

6. Data output to the matrix display.

7. Speed control.

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Braille Encoder

MICROCONTROLLER WHICH WILL BE USED IN THE PROJECT

Features

• Compatible with MCS-51™ Products

• 4K Bytes of In-System Reprogrammable Flash Memory

– Endurance: 1,000 Write/Erase Cycles

• Fully Static Operation: 0 Hz to 24 MHz

• Three-level Program Memory Lock

• 128 x 8-bit Internal RAM

• 32 Programmable I/O Lines

• Two 16-bit Timer/Counters

• Six Interrupt Sources

• Programmable Serial Channel

• Low-power Idle and Power-down Modes

4.1.4. BRAILLE DISPLAY

Braille matrix display is a rectangular arrangement of cells of 6 raised dots. The cells are

arranged in a grid of two dots horizontally by three dots vertically. A single cell is used to

represent the Braille characters in running sequence, where the entire line can be read in

several readings.

Pin inside each cell is controlled electronically to move up and down to represent the

Braille characters. Presence or absence of the pin in the 3*2 matrix gives the impression

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Braille Encoder

of the Braille character. When currents or voltages are applied to points in each six-pin

array, various combinations of elevated and retracted pins produce the effect of raised

dots or dot-absences.

Each pin is cylindrical iron shaft with a spring encircling it. An electromagnetic coil is

wound around a cylinder. This cylinder is placed above the shaft. The coil is excited by

the microcontroller. The microcontroller gives the signal to the ULN 2803 driver, which

provides the required amount of current to the coil.

When the current is passed through the coil, the pin gets elevated corresponding to a

raised dot in Braille whereas in the absence of excitation the spring retracts the position

of the pin.

4.1.5 BRAILLE MATRIX ASSEMBLY

The Braille matrix is a 6 pin array. We are using solenoids for elevating

the pins. Thus the arrangement of the pins is shown in the figure. The front, bottom,

& top view are shown. The electromagnets are arranged at the four corners, and the

centers of the electric switch board. The pins or the plunger is soldered with a gas

welding rod which has high mechanical strength. It is bent at 90 degrees for getting

the pins closer for better performance, and matching the standard dimensions. The

wires to the pins are soldered such that the current moves only in one direction in all

solenoids. The top view and front view is shown in the next figure with the

dimensions of height, width, length. The bottom view will show the arrangement of

the solenoids in the assembly.

FRONT VIEW

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Center lines

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Box outline

TOP VIEW

All dimensions in mm.

Fig 4.5 Front and top view of the assembly.

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4

47

8

6

99

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Braille Encoder

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Hole for wires to come out of the box Electromagnet

BOTTOM VIEW

All dimensions in mm

Fig 4.6 Bottom view of the assembly showing the arrangement of the solenoids

4.1.6. DRIVER

98

10

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Braille Encoder

Electromagnet needs a certain amount of current for excitation. The sourcing current of

the microcontroller is quite less than the actual requirement of the electromagnet. Hence a

suitable interface is needed that will supply the necessary current to the electromagnetic

coil.

A ULN 2803 driver is used to drive th4e coil of Braille matrix assembly. The output

terminal of the ULN 2803 is open collector. So, the electromagnet coil acts as a load to

the ULN output. Whenever the ULN is given input, it will drive the coil the necessary

current. Current of about 150-200mA is required to excite the coil.

5. SYSTEM DESIGN

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Braille Encoder

5.1 POWER SUPPLY DESIGN:

A Dual Symmetry Power supply is used to power the system.Transformer used : Center tapped transformer.Rectifier: Diodes arranged in a bridge.Regulator IC: 7805.

Power supply Calculations as per National semiconductors handbook

Vac = (Vdc)*Vnom/0.92*Vlow(2)^1/2Where,

Vdc = Vout+Vreg+Vrect+VrippleVout= 5V , Vreg= 3V Vrect = 2*1.125 =2.5V for bridge.Vripple = 10% of Vout= 0.5VVnom & Vlow are voltages that take into account line variation +/- 10% of input supply.Vnom= 230+23=253VVlow=230-23=207VVdc=5+3+2.5+0.5= 11.4VVac= 11.4*253/(0.92*207*(2)^1/2 = 10.74V

For full wave bridge rectifierIac=1.8*dc Iac=1.8*1.08 = 1.944A

Capacitor FilterC= Vout/(2*f*Rl*Vripple)

Assuming Rl = 100C=5/(2*50*100*0.5) = 1000uF

5.2 CIRCUIT DIAGRAM

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Braille Encoder

Fig 5.1 Circuit diagram

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Braille Encoder

5.3 CONNECTION TO RS232

The RS232 is not TTL compatible. In RS232 a 1 is represented by -3 to -25V, while a 0

bit is represented by +3 to +25V. Therefore, MAX232 is used as a voltage converter to

convert RS232 voltage levels to TTL voltage levels, and vice versa. The microcontroller

pins RxD (P3.0) and TxD (P3.1) are used specifically for receiving and transferring data

serially. These pins are TTL compatible and are connected to MAX232 to make them

RS232 compatible.

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Braille Encoder

5.4 MAX232

The MAX232, voltage converter, uses a +5V power supply. The line

drivers used in the system are T1 and R1 of MAX232. MAX232 requires for capacitors.

The capacitors used are 10uF/16V.

5.5 RESET CIRCUIT

The microcontroller is reset only if the reset pin is held high for at least

two machine cycles. Thus the reset circuit consists of a RC circuit with time constant

greater than two machine cycles (2*1.085usec), where the time period of one machine

cycle is 1.085usec.

Let C=10uF.

RC time constant >> 2*1.085usec

So R = 8.2K.

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Braille Encoder

6. EXPERIMENTAL SETUP

1. In order to test the encoder circuit the encoder is connected to the PC’s

COM port (COM 1) through a RS232 Cable.

2. A data file data.txt is created on the P.C. and saved to the location

specified in the program.

3. The microcontroller requests for the characters from the PC. The

incoming characters are then converted into respective Braille

characters by using a look-up-table.

4. The values are then ported to PORT 0 pins to which the

electromagnets are connected.

5. The operation depends upon the mode. i.e. automatic or manual

In Automatic mode,

The speed is set by a digital switch. The number in the

switch will be set to a delay routine & depending on the

value the routine will be called those many times.

In Manual mode,

The character will be requested after pressing the previous

or next keys.

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Braille Encoder

7. SOFTWARE DEVELOPMENT

The program code for the microcontroller is written using assembly level programming.

The code ensures proper synchronization of data transfer by setting the appropriate baud

rate as well as it has to check for the end of the text while transferring the data. The

conversion to Braille characters is done by using a look-up table stored in the

microcontroller’s code memory. The Braille characters are then given to the Braille

Matrix assembly.

Proteus is used to generate the Hex file of the code. The hex file is then transferred to the

microcontroller using dos commands.

The data file is transferred to the controller serially. A array is generated using V.B. on

the P.C. which sends the file at the prescribed baud rate. Successful data transfer of data

are achieved via COM 1 port.

In the implementation of the project we require various software’s for designing the PCB

for our circuit , code compilation , serial communication .

o PCB designing:

There are many software’s for the design of the PCB viz. express PCB, Eagle PCB,

Proteus, Protel, Ultiboard. Out of these we will use Eagle PCB for designing our PCB

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Braille Encoder

o CODE Compilation:

For writing and compiling the assembly language code we use proteus. This

software exclusively compiles the code for 8051 microcontroller.

o Serial Communication:

We have to send data from computer to the controller we require a communication

interface, which is provided by RS232, but along with the hardware we need a software

to back it. Thus the program in Turbo C or VB. for serial communication.

SOFTWARE USED

Eagle PCB

Dos

Visual Basics

Proteus Proff 6.

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8. ALGORITHM AND FLOWCHART

8.1 ALGORITHM

Step 1: Initialize the Microcontroller and serial communication.

Step 2: Select the mode of transmission( manual or automatic).

Step 3: If manual read key, if automatic set the delay and then read key.

Step 4: If next character is required increment the counter, if previous

character is required then decrement counter.

Step 5: Send interrupt request to P.C.

Step 6: Get the data from P.C.

Step 7: Compare the received data with look up table.

Step 8: Send the corresponding value from look up table to the desired port.

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8.2 FLOWCHART

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START

Initialization of Serial interface and Microcontroller.

Check key =?

Manual Speed Automatic

Set Delay

Read Key

P or N = ?

Increment Decrement

A

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A

Interrupt to P.C.

Receive Data from Com 2 port of P.C.

Compare received Data with look up table.

Send the corresponding value from look up table to the desired port.

STOP

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9. PERFORMANCE EVALUATION

9.1 Test Results

These are the expected test results. The whole project will require a lot of testing.

It will start from the testing of the PCB, & will go up to the expected output.

The total expected results are enlisted below.

After designing the PCB on the mentioned software we need to test the

continuity of the tracks. We will be required to use the multi-meter.

The computer needs to communicate with the microcontroller at the

specified baud rate.

The respective port pins have to be checked after the character is received.

i.e. when a character is received the controller should energize the relay

coils at the output according to the character received, as well as light the

respective LED’s. This will take place according to the look up table in the

controller memory.

The user will be able to back track the character received, i.e. if the user is

unable to read the character he will be able to go back and check the data

sent again.

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10. RESULTS

The Serial transmission from computer to the system takes place reliably nad successfully

at the baud rate of 2400 bps. The data is then stored in the memory. The write cycle of

the memory programs 64 bytes of data at the same time. The characters after conversion

are given to the Braille Assembly through the driver. The coil of the electromagnet takes

around 150-200mA operating at 5V, or 400-500mA operating at 12V for getting

energized and attracting the iron shaft. The speed of the sequential display can be

successfully controlled. Character back tracking can be achieved due to the array

generated on PC.

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Braille Encoder

11. ANALYSIS AND CONCLUSION

The Braille Encoder will prove an handy tool for the visually impaired students. With the

added user friendly features of speed control and character back tracking the user can

control the flow of the data. The Braille encoder is set to add a whole new dimension to

the classroom teaching for the visually impaired students with the computer compatible

feature, they can use the system for so much more constructive purpose.

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Braille Encoder

12. FURTHER MODIFICATIONS

The Scope for further modification is quite large.

a. The system as such is suited for information in text format. The other

data format like .pdf, word format can also be used by considering

the overhead involved in the form of headers and trailers while

storage.

b. The system can also be modified for use as a calculator. A keypad

can be interfaced to the controller. This will prove to be of great help

for the students.

c. A memory can be used to store the data & recall it when the students

have spare time or no computer for new data.

d. The serial interface used is wired. USB can also be used for

communication. Even if school is having a network library, the

encoder can be connected to the Ethernet with wireless LAN acting

as the communication interface.

e. Instead of using a single cell for display purpose 40/80 cells can be

implemented.

f. A rotating wheel structure can also be implemented in order to

reduce the size and can also help access the characters without the

movement of the finger tips.

g. A buzzer can be implemented in the scheme for ever button press.

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13. LIST OF COMPONENTS

Component Specification Quantity 1. Center tapped transformer 15-0-15 V, 1A. 1

2. Regulator LM7805 2

3. Heat sink 1

4. Diodes 1N4001 4

5. Microcontroller AT89C51 1

6. Driver ULN2803 1

7. UART I.C. HIN232 1

8. Connector DB-9 , relimate 1

9. Solenoids 6

10. Braille Pins 6

11. Crystal 11.0592 MHz 1

12.Cable RS232 1

13.Capacitors 33pF 2

10uF/16V 5

0.1uF 3

14. Resistors 10Kohms 3

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14. ARTWORK AND LAYOUT

14.1 PCB LAYOUT

Fig 14.1 Bottom side of PCB

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14.2 SILKSCREEN TOP

Fig 14.2 Silkscreen top

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15. REFERENCE

The main source of information was the internet, along with the books.

The books that will be used are mentioned below.

Books:

1. Mazadi and Mazadi.

Internet

Site name Date

1. www.omniglot.com/writing/braille.htm 20-8-07

2. www.simple.wikipedia.org/wiki/Braille_script 20-8-07

3. en.wikipedia.org/wiki/Louis_Braille 20-8-07

4. www.braille.org 20-8-07

5. www.afb.org/braillebug/ 30-8-07

6. www.huffmancoding.com/code/braille 30-8-07

7. www.dots.physics.orst.edu/gs_layout.html 30-8-07

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