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                                                   AUTOMATED ATTENDANCE SYSTEM
                               ABSTRACT
‘AUTOMATED ATTENDANCE SYSTEM ’ is designed to collect and manage
student’s attendance records from RFID devices installed in a class rooms.
Based on the verification of student identification at the entrances system, the
RFID tag can be embedded in the ID card of the individual. First to activate a
new session(hour) the teacher swipes her RFID tag this marks a new attendance
session during which the students can swipe once to increment their attendance.
The RFID module operate in 125Khz range, when a tag passes through its
vicinity, the module senses its presence and extracts its unique serial number
and passes this code into microcontroller which matches the code to the correct
person and increments the attendance of the particular person.




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                                              AUTOMATED ATTENDANCE SYSTEM



                             CONTENTS

Chapter No                            TOPIC                       Page



1. Introduction………………………………..                                        04

2. Block Diagram and Description……….…                             05

3.Circuit ……………………                                                   09

   Circuit Diagram ..........…….…….                                  10

   Circuit Description………………………                                      11

4.Software……………..................                          24


5.Printed Circuit Board ………………………....                           30


      PCB Layout …………………….……                                    43



6.Estimate…………………………………….                                   44

7.Conclusion ………………………………...                                    46

8.Bibpiography…………………………………                                  48




      APPENDIX Data Sheets…………………..                             50




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                            AUTOMATED ATTENDANCE SYSTEM




             INTRODUCTION




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                                                     AUTOMATED ATTENDANCE SYSTEM




                            INTRODUCTION

       The two major problems faced by organizations are time consuming
manual attendance and wastage of electrical power. Our project is going to
solve these problems by using RFID technology. The project is designed to
store up to 50 card IDs but it is easily scalable up to 65000 card IDs but for that
it requires external memory. Radio Frequency Identification (RFID) is an
automatic identification method, relying on storing and remotely retrieving data
using devices called RFID tags or transponders. So the RFID is a wireless
identification.
       Normally the RFID system comprises of two main parts: RFID Reader
and RFID Tag. RFID Reader is an integrated or passive network which is used
to interrogate information from RFID tag. The RFID Reader may consist of
antenna, filters, modulator, demodulator, coupler and a micro processor.




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                            AUTOMATED ATTENDANCE SYSTEM




              BLOCK DIAGRAM




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                                 AUTOMATED ATTENDANCE SYSTEM




  BLOCK DIAGRAM

                      LCD




                                     MAX232
              MICROCONTROLLER                       Computer
RFID READER



                  Power supply




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                                                   AUTOMATED ATTENDANCE SYSTEM




BLOCK CIRCUIT DESCRIPTION

COMPONENTS OF SYSTEM
     The figure below shows the basic block diagram of the
AUTOMATED ATTENDANCE USING RFID. It contains the following
blocks:

1. RFID reader
2. RFID tags
3. LCD display
4. Microcontroller
5.MAX232
6. Power supply unit




RFID READER

A reader (now more typically referred to as an RFID interrogator) is basically a
radio frequency (RF) transmitter and receiver, controlled by a microprocessor or
digital signal processor. The reader, using an attached antenna, captures data
from tags, then passes the data to the controller for processing. The reader
decodes the data encoded in the tags integrated circuit (silicon chip) and the
data is passed to the microcontroller for processing



RFID TAGS


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                                                    AUTOMATED ATTENDANCE SYSTEM

      Tags also sometimes are called “transponders”. RFID tags can come in
many forms and sizes. Some can be as small as a grain of rice. Data is stored in
the IC and transmitted through. The antenna to a reader. The two commonly
used RFID Transponders are Active (that do contain an internal battery power
source that powers the tags chip) and Passive (that do not have an internal
power source, but are externally powered typical from the reader) RFID
Transponders.

LCD DISPLAY
      The display support 2X16 characters, which means, the LCD can support
2 lines on the display and each line can display up to 16 characters which is
relevant as the only essential output to be displayed is the student’s name and
ID. Besides LCD Display, the output is displayed on LCD. The diagram of
LCD display is shown in Figure and the detailed connections of the LCD is
shown in table


MICROCONTROLLER
                 The microcontroller used is PIC 16F877A.
Microcontroller is a general-purpose device, but one that is meeting to
read performs limited calculations on data, and contained is its environ
based on these calculations. The prime use, of Microcontroller is to
control the operation of a machine using a fixed program that is stored in
and does not change over the lifetime of the system.



MAX232

            The MAX232 is an integrated circuit that converts signals from an
RS-232 serial port to signals suitable for use in TTL compatible digital logic
circuits. The MAX232 is a dual driver/receiver and typically converts the RX,
TX, CTS and RTS signals.




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                                                    AUTOMATED ATTENDANCE SYSTEM
POWER SUPPLY
      These form an important equipment of any Electronics laboratory. Power
supplies are essential for the testing and implementation of any useful electronic
circuit. If power supplies are not available then the only way to provide power
to a circuit is the battery. For long-term use and frequent manipulation these are
not feasible. More over these are not as flexible as modern day power supplies.
They do not provide for overload protection and thermal protection.




                                CIRCUIT




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                             AUTOMATED ATTENDANCE SYSTEM




               CIRCUIT DIAGRAM




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                                                   AUTOMATED ATTENDANCE SYSTEM




                 CIRCUIT DIAGRAM DESCRIPTION

     The circuit below shows the AUTOMATED ATTENDANCE USING
RFID. It contains

1. RFID reader
2. RFID tags
3. LCD display
4. Microcontroller
5.MAX232
6. Power supply unit

RFID READER
A reader (now more typically referred to as an RFID interrogator) is basically a
radio frequency (RF) transmitter and receiver, controlled by a microprocessor or
digital signal processor. The reader, using an attached antenna, captures data
from tags, then passes the data to the controller for processing. The reader
decodes the data encoded in the tags integrated circuit (silicon chip) and the
data is passed to the microcontroller for processing.


FEATURES OF RFID READER
a. Low cost solution for reading passive RFID transponder tags.
b. Industrial grade casing for better outlook and protection.
c. Integrated RFID reader, antenna, LED, power cable and data cable.
d. Every reader has been tested before is being shipped.


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                                                   AUTOMATED ATTENDANCE SYSTEM
e. 9600 baud RS232 serial interface (output only) to PC.
f. Fully operation with 5VDC power supply.
g. Buzzer as sound indication of activity.
h. Bi-colour LED for visual indication of activity.
i. Standard RS232 serial cable (female) ready to plug to desktop PC or Laptop.
j. 2m reading range.
k. 0.1s response time.
l. Operating frequency: 125KHz




                 FIGURE 4.2 PIN DIAGRAM OF RFID READER



RFID TAGS
      Tags also sometimes are called “transponders”. RFID tags can come in
many forms and sizes. Some can be as small as a grain of rice. Data is stored in
the IC and transmitted through. The antenna to a reader. The two commonly
used RFID Transponders are Active (that do contain an internal battery power
source that powers the tags chip) and Passive (that do not have an internal
power source, but are externally powered typical from the reader) RFID
Transponders.




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                                                   AUTOMATED ATTENDANCE SYSTEM
WORKING OF RFID
      Information is sent to and read from RFID tags by a reader using radio
waves. In passive systems, which are the most common, an RFID reader
transmits an energy field that “wakes up” the tag and provides the power for the
tag to respond to the reader. Data collected from tags is then passed through
communication interfaces (cable or wireless) to
PIC16F877A in the same manner that data scanned from bar code labels is
captured and passed to computer systems for interpretation, storage, and action.

LCD DISPLAY
      The display support 2X16 characters, which means, the LCD can support
2 lines on the display and each line can display up to 16 characters which is
relevant as the only essential output to be displayed is the student’s name and
ID. Besides LCD Display, the output is displayed on LCD. The diagram of
LCD display is shown in Figure and the detailed connections of the LCD is
shown in table




                         DIAGRAM OF LCD DISPLAY

Table Pin connections of LCD Display.


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                                                     AUTOMATED ATTENDANCE SYSTEM

EEPROM
       EEPROM stands for Electrically Erasable Programmable Read-Only
Memory and is a type of non-volatile memory used in computers and other
electronic devices to store small amounts of data that must be saved when
power is removed. In PIC16F877A, the data EEPROM is readable and writable
during normal operation (over the full VDD range). This memory is not directly
mapped in
the register file space. Instead, it is indirectly addressed through the Special
Function
Registers.

MICROCONTROLLER
 The microcontroller used is PIC 16F877A. Microcontroller is a general-
purpose device, but one that is meeting to read performs limited
calculations on data, and contained is its environ based on these
calculations. The prime use, of Microcontroller is to control the
operation of a machine using a fixed program that is stored in and does
not change over the lifetime of the system.

                     The Microcontroller design uses a much more
limited set of single and double byte instructions that are used to move
code and data from internal memory to the ALU. Many instructions are
coupled with pins on the IC package; the pins are “programmable” that
is, capability of having several different functions dispending on the
wishes of the programmer. The Microcontroller is concerned with
getting data from and its own pins; the architecture and instruction set
are optimized to handle data in bit and byte size.

       Microcontroller will have much type of bit handling instructions.
It may have operational code for moving data from external memory to
CPU. Microcontroller may have one or two concerned with rapid
movement of code and data from external address.

                 The Microcontroller can function as a compiler with the
addition of No external digital parts. Modules vary in data size 4 to 32
bits. For four bit units in huge volume for very simple, and 8 bit units are
most versatile.16 and 32 bits are used in high-speed control and signal



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                                                  AUTOMATED ATTENDANCE SYSTEM
processing applications. Many modules feature a programmable pin that
allows external memory to be addressed with the loss of I\O capability.



PIC MICROCONTROLLER
      PIC is a family of Harvard architecture microcontrollers made by
Microchip Technology, Derived from the PIC 1640 originally developed by
General Instrument’s Microelectronics Division. The name PIC initially
referred to “Peripheral Interface Controller”. It is available in different
configuration via 8 bit, 16 bit,32 bit with instruction set as given below:

Under 8 bit        comes-   PIC10xxxx,PIC12xxxx,PIC16xxxx,PIC18xxxx,(12    bit
instruction set)

Under 16 bit comes-PIC24h,DSPIC30,DSPIC33.(14 bit instruction set)

Under 32 bit comes-PIC32xxxx.(16 bit instruction set)

      PICs are popular with developers and hobbyists alike due to their low
cost ,wide availability, large user base, extensive collection of application
notes, availability Of low cost or free development tools, and serial
programming(and reprogramming With flash memory) capability.



Special Microcontroller Features
    High performance RISC CPU.
    Only 35 single word instructions to learn.
    All single cycle instructions except for program branches which are two-
     cycle.
    Operating speed: DC- 20 MHz clock input DC-200 ns instruction cycle.
    Up to 8Kx 14 words of FLASH Program Memory, Up to 368x 8 bytes of
     Data
    Memory(RAM).
    Interrupt capability(up to 12 sources).
    Eight level deep hardware stack.
    Direct, Indirect and Relative Addressing modes.



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                                                  AUTOMATED ATTENDANCE SYSTEM
     Processor read access to program memory.
     Power-on Reset(POR).
     Power-up Timer(PWRT) and Oscillator Start-up Timer (OST).
     Watchdog Timer (WDT) with its own on-chip RC oscillator for reliable
      operation.
     Programmable code protection
     Power saving SLEEP mode
     Selectable oscillator options
     In-Circuit Serial Programming (ICSP) via two pins.




Peripheral Features


       Timer0:8-bit timer/counter with 8-bit prescaler.
       Timer1:16-bit timer/counter with prescaler ,can be incremented
        during SLEEP via external crystal/clock.
       Timer2:8-bit timer/ counter with 8bit period register, prescaler and
        postscaler.
       Two Capture ,Compare, PWM modules
       -Capture is 16-bit, max. resolution is 12.5 ns
       -Compare is 16-bit , max . resolution is 200 ns
       -PWM max. resolution is 10-bit.
       8-bit, upto 8-channel Analog-to-Digital converter.
       Synchronous Serial Port(SSP) with SPI (Master mode) and 12C(slave).
       Universal Synchronous Asynchronous Receiver Transmitter
        (USART/SCI).
       Parallel Slave Port (PSP), 8-bits wide with external RD, WR and CS
        controls(40/44-pin only).
       Brown-out detection circuitry for Brown-out Reset(BOR)




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                            AUTOMATED ATTENDANCE SYSTEM




DEVICE STRUCTURE




Features


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                                                  AUTOMATED ATTENDANCE SYSTEM
       Microchip’s PIC micro 8bit MCU’s offer a price/ performance ratio that
allows them to be considered for any traditional 8 bit MCU application as well
as some traditional 4 bit application, dedicated logic replacement and low end
DSP applications. These features and price performance mix make PIC micro
MCU’s an attractive solution for most applications.




TYPES OF MICROCONTROLLER ARCHITECTURE
   There are two types of Microcontroller architecture designed for
embedded system

  development. These are:

    1. RISC-Reduced instruction set computer
    2. CISC-Complex instruction set computer




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                                                   AUTOMATED ATTENDANCE SYSTEM




DIFFERENCE BETWEEN CISC AND RISC:
       CISC stands for Complex instruction Set Computer. Most PC’s use CPU
based on this architecture. For instance Intel and AMD CPU’s are based on CISC
architectures. Typically CISC chips have a large amount of different and
complex instructions. In common CISC chips are relatively slow (compared to
RISC chips) per instruction, but use little (less than RISC) instructions MCS-51


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                                                    AUTOMATED ATTENDANCE SYSTEM
family microcontrollers based on CISC architecture. RICS stands for Reduced
Instruction Set Computer. The philosophy behind it is that almost no one uses
complex assembly language instructions as used by CISC, and people mostly
use compilers which never use complex instructions. Therefore fewer, simpler
and faster instructions would be better, than the large, complex and slower
CISC instructions. However, more instructions are needed to accomplish a task.



MAX232

             The MAX232 is an integrated circuit that converts signals from an
RS-232 serial port to signals suitable for use in TTL compatible digital logic
circuits. The MAX232 is a dual driver/receiver and typically converts the RX,
TX, CTS and RTS signals.

      The drivers provide RS-232 voltage level outputs (approx. ± 7.5 V) from
a single + 5 V supply via on-chip charge pumps and external capacitors. This
makes it useful for implementing RS-232 in devices that otherwise do not need
any voltages outside the 0 V to + 5 V range, as power supply design does not
need to be made more complicated just for driving the RS-232 in this case.

     The receivers reduce RS-232 inputs (which may be as high as ± 25 V), to
standard 5 V TTL levels. These receivers have a typical threshold of 1.3 V, and
a typical hysteresis of 0.5 V.

     The later MAX232A is backwards compatible with the original MAX232
but may operate at higher baud rates and can use smaller external capacitors –
0.1 μF in place of the 1.0 μF capacitors used with the original device. The newer
MAX3232 is also backwards compatible, but operates at a broader voltage




range, from 3 to 5.5




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                            AUTOMATED ATTENDANCE SYSTEM




POWER SUPPLY




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                                                 AUTOMATED ATTENDANCE SYSTEM
            These form an important equipment of any Electronics laboratory.




Power supplies are essential for the testing and implementation of any useful
electronic circuit. If power supplies are not available then the only way to
provide power to a circuit is the battery. For long-term use and frequent
manipulation these are not feasible. More over these are not as flexible as
modern day power supplies. They do not provide for overload protection and
thermal protection.



The following units form the backbone of any modern day power supply




   1.    Full wave bridge rectifier
   2.    Filter circuit
   3.    Voltage regulator




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                                                      AUTOMATED ATTENDANCE SYSTEM
                In the case if modern power supplies, the required power is

  derived from the AC mains. For this at first the 230V/50 Hz is step down

  using a step down transformer. Then The AC voltage is converted to DC

  using a rectifier circuit. The bridge rectifier is considered the apt choice since

  it avoids the center-tapped transformer. The ripples from the rectifiers output

  are removed by filtering.

The filter can be any of the following:




   1.     L filter
   2.    C filter
   3.    LC filter
   4.    CRC filter



   And we use capacitive filtering.

   The function of the voltage regulator is to provide a stable DC voltage for
   powering other electronic circuits. The voltage regulator must be capable of
   providing substantial output current. They must provide a constant voltage
   regardless of changes in load current, temperature, and AC line voltage.
   Although voltage regulators can be designed using opamps, it is quicker and
   easier to use IC Voltage regulators. Further more, IC voltage regulators are
   versatile and relatively inexpensive and are available with features such as
   programmable output, current / voltage boosting, internal short –circuit
   current limiting, thermal shut down, and floating operation for high voltage
   applications.


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                            AUTOMATED ATTENDANCE SYSTEM




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                             AUTOMATED ATTENDANCE SYSTEM




                SOFTWARE




                  Software


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                                              AUTOMATED ATTENDANCE SYSTEM



char rfid[17],i=0,n=0,attn[10]={0},sel[10]={0};
void main()

{

  UART1_Init(9600);              //Initializes USART module with
baud rate 9600

    Lcd_Init();                  //Initializes LCD

  Delay_ms(1000);                //Wait till the modules settles
down

    Lcd_Cmd(_LCD_CLEAR );        //Clear Screen

    Lcd_Cmd(_LCD_CURSOR_OFF);    //Switch off cursor from screen

  Lcd_Out(1,6,"WELCOME");        //Print welcome at 1st row & 6th
column

    TRISD0_bit=0;

    TRISD1_bit=1;

    RD0_bit=0;

    if(RD1_bit==0)

    {

    for(i=0;i<2;i++)            //Save the current data to EEPROM

      EEPROM_Write(i,0);        //Save to 'i'th EEPROM position
attendance of 'i'th student

    }

    for(i=0;i<2;i++)

   attn[i]=EEPROM_Read(i);   //Read the current attendance of
students from EEPROM at power ON time

    while(1)                    //Main infinite loop

    {    n=0;

        while(1)                //UART loop



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                                              AUTOMATED ATTENDANCE SYSTEM
      {



          if(UART1_Data_Ready()) //Check if data is sent by Reader

       {

            i=UART1_Read();        //Get the data

        if(i==13)            //If data is stop byte then place
terminating character on the string

            {

                rfid[n]='\0';

                break;

            }

        else if(i==10){}           //Remove starting character from
the string

            else

            {

          rfid[n]=i;               //Add each character received
from Reader to the string

                 n++;

            }

       }

  }

   if(!strcmp(rfid,"3F00EDA52B"))            //Compare the RFID
string

   {

           Lcd_Cmd(_LCD_CLEAR);              //Clear LCD

       Lcd_Out(1,2,"Arun          :");       //If match found
display the name

       if(sel[0]==0)                         //If attendance not
incremented



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                                        AUTOMATED ATTENDANCE SYSTEM
       {

         attn[0]++;                    //Increase attendance
of the selected person

         sel[0]=1;                     //Marks current
person's attendance as incremented

       }

       Lcd_Out(1,13,attn[0]);         //Display Attendance

       UART1_Write_Text("Arun");      //Send the student data
to computer

       UART1_Write_Text (attn[0]);     //Send attendance

   }

   if(!strcmp(rfid,"3F00ED6845"))       //Compare the RFID
string

   {

       Lcd_Cmd(_LCD_CLEAR);            //Clear LCD

       Lcd_Out(1,2,"Anson   :");       //If match found
display the name

       if(sel[1]==0)                    //If attendance not
incremented

       {

            attn[1]++;               //Increase attendance of
the selected person

            sel[0]=1;                //Marks current person's
attendance as incremented

       }

       Lcd_Out(1,13,attn[1]);          //Display Attendance

       UART1_Write_Text("Anson");      //Send the student
data to computer

       UART1_Write_Text (attn[0]);     //Send attendance

   }




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                                        AUTOMATED ATTENDANCE SYSTEM
   if(!strcmp(rfid,"3F00ED7512"))       //Check then for
teachers RFID tag

     {

    for(i=0;i<2;i++)                 //If teacher's tag found
then allow students to register again

       sel[i]=0;                        //Starts new session
of attendance

         Lcd_Cmd(_LCD_CLEAR);           //Clear LCD

         Lcd_Out(1,1,"Welcome Sir ");   //Displays welcome
note

     }

   for(i=0;i<2;i++)                     //Save the current
data to EEPROM

      EEPROM_Write(i,attn[i]);          //Save to 'i'th EEPROM
postion attendance of 'i'th student

 }

}




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                                                     AUTOMATED ATTENDANCE SYSTEM
Software description


              The software is developed in the high level language MikroC.In
the beginning, the array to store RFID code is declared. The attendance and
selection arrays are declared and initialized to 0.USART module is initialized
with baud rate 9600.The LCD is initialized and it waits for a time of 1 second to
settle down. Then the screen is cleared and the cursor is switched off.Welcome
message is displayed.

      For the initialization purpose pin RD0 is made input pin and RD1 is made
output pin using TRIS bit.RD0 is set as 0, when RD0 and RD1 is shorted the
system resets. If RD1=0, the attendance of ith student is stored at ith position of
EEPROM. Read the current attendance of students from EEPROM at power ON
time and enters the main infinite loop.

       Enters the UART loop and checks whether any data is received. If the
received data is stop bit, i.e., 13 terminating character is placed on the RFID
string. Else the starting character 10 is detected and removed to accept the 10 bit
data and stored in rfid array.

       Compare the received string, i.e., the code with code of tag holder, if
match is found the name of the individual is displayed. Checks whether
attendance is incremented earlier in the same session using selection array. If
selection variable for the student is 0 which is initialized so, the attendance in
attn array is incremented by 1.And makes the value of selection variable of the
student whose attendance is incremented as 1,so that he can use the tag once in
the same session. The attendance is displayed in LCD and sent to the computer
for storage with corresponding student’s details. In this program this is done for
2 students, whose attendance can be incremented by showing their tags.

In this system it is arranged in such a way that, if the card holder is a teacher
his/her unique code will be identified and the selection variable of all students
are made 0 by assigning value 0 to sel array. This marks the starting of a new
session in which students can increment their attendance once. And displays a
welcome message to teacher. The data is sent to save in the EEPROM at ith
position, where i is the number of students




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                            AUTOMATED ATTENDANCE SYSTEM




        PRINTED CIRCUIT BOARD




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                                                     AUTOMATED ATTENDANCE SYSTEM
                           PCB DESIGNING

PCB PREPARATION TECHNIQUES
 You need to generate a positive (copper black) UV translucent artwork film.

 You will never get a good board without good artwork, so it is important to

 get the best possible quality at this stage. The most important thing is to get a

 clear sharp image with a very solid opaque black. Nowadays, artwork is

 drawn using either a dedicated PCB CAD program or a suitable

 drawing/graphics package. It is absolutely essential that your PCB software

 prints holes in the middle of pads, which will act as center marks when

 drilling. It is virtually impossible to accurately hand-drill boards without

 these holes. If you’re looking to buy PCB software at any cost level and want

 to do hand-prototyping of boards before production, check that this facility is

 available. If you’re using a general-purpose CAD or graphics package, define

 pads as either a grouped object containing a black-filled circle with a smaller

 concentric white-filled circle on top of it, or as an unfilled circle with a thick

 black line (i.e. a black ring). When defining pad and line shapes, the

 minimum size recommended for vias (through-linking holes) for reliable

 results is 50 mil, assuming 0.8mm drill size; 1 mil = (1/1000)th of an inch.

 You can go smaller with smaller drill sizes, but through-linking will be

 harder. 65mil round or square pads for normal components and DIL ICs, with

 0.8mm hole, will allow a 12.5 mil, down to 10 mil if you really need to.


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                                                    AUTOMATED ATTENDANCE SYSTEM
  Centre-to-centre spacing of 12.5mil tracks should be 25 mil—slightly less

  may be possible if your printer can manage it. Take care to preserve the

  correct diagonal track-track spacing on mitered corners; grid is 25 mil and

  track width 12.5 mil. The artwork must be printed such that the printed side is

  in contact with the PCB surface when exposing, to avoid blurred edges. In

  practice, this means that if you design the board as seen from the component

  side, the bottom (solder side) layer should be printed the ‘correct’ way round,

  and the top side of a double-sided board must be printed mirrored.

 Media

     Artwork quality is very dependent on both the output device and the
media used. It is not necessary to use a transparent artwork medium—as long
as it is reasonably translucent to UV, its fine-less translucent materials may
need a slightly longer exposure time. Line definition, black opaqueness and
toner/ink retention are much more important. Tracing paper has good enough
UV translucency and is nearly as good as drafting film for toner retention. It
stays flatter under laser-printer heat than polyester or acetate film. Get the
thickest you can find as thinner stuff can crickle. It should be rated at least 90
gsm; 120 gsm is even better but harder to find. It is cheap and easily available
from office or art suppliers.

     Output devices

     Laser printers offer the best all-round solution. These are affordable, fast,
and good-quality. The printer used must have at least 600dpi resolution for all
but the simplest PCBs, as you will usually be working in multiples of 0.06cm (40


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tracks per inch). 600 dpi divides into 40, so you get consistent spacing and line
width. It is very important that the printer produces a good solid black with no
toner pinholes. If you’re planning to buy a printer for PCB use, do some test
prints on tracing paper to check the quality first. If the printer has a density
control, set it to the blackest. Even the best laser printers don’t generally cover
large areas well, but usually this isn’t a problem as long as fine tracks are solid.
When using tracing paper or drafting film, always use manual paper feed and
set the straightest possible paper output path to keep the artwork as flat as
possible and minimize jamming. For small PCBs, you can usually save paper by
cutting the sheet in half. You may need to specify a vertical offset in your PCB
software to make it print on the right part of the page. Some laser printers
have poor dimensional accuracy, which can cause problems for large PCBs. But
as long as any error is linear, it can be compensated by scaling the printout in
software. Print accuracy is likely to be a noticeable problem when it causes
misalignment of the sides on double-sided PCBs—this can usually be avoided
by careful arrangement of the plots on the page to ensure the error is the
same on both layers; for example, choosing whether to mirror horizontally or
vertically when reversing the top-side artwork.

Photo resist PCB laminates
  Always use good-quality, pre-coated photo resist fiberglass (FR4) board.

  Check carefully for scratches in the protective covering and on the surface

  after peeling off the covering. You don’t need darkroom or subdued lighting

  when handling boards, as long as you avoid direct sunlight, minimize

  unnecessary exposure, and develop immediately after UV exposure.

  Instagraphic Microtrak board develops really quickly, gives excellent



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  resolution, and is available in thin (0.8mm) and heavy copper flavors. On

  using spray-on photoresist, you will always get dust settling on the wet resist.

  So it is not recommended unless you have access to a very clean area or

  drying oven, or you only want to make low-resolution PCBs.

Exposure

       The photo resist board needs to be exposed to UV light through the
artwork, using a UV exposure box. UV exposure units can easily be made using
standard fluorescent lamp ballasts and UV tubes. For small PCBs, two or four
8-watt, 30.5cm tubes will be adequate. For larger (A3) units, four 38cm tubes
are ideal. To determine the tube-to-glass spacing, place a sheet of tracing paper
on the glass and adjust the distance to get the most even light level over the
surface of the paper. Even illumination is a lot easier to obtain with 4-tube units.
The UV tubes you need are sold as replacements for UV exposure units, ‘black
light’ tubes for disco lighting, etc. These look white, occasionally black/blue
when off, and light up with a light purple. Do not use short-wave UV lamps like
EPROM eraser tubes and germicidal lamps that have clear glass, because these
emit short-wave UV which can cause eye and skin damage. A timer that
switches off the UV lamps automatically is essential, and should allow exposure
times from 2 to 10 minutes in 15- to 30-second increments. It is useful if the
timer has an audible indication when the timing period has completed. A timer
from a scrap microwave oven would be ideal. Use glass sheet rather than plastic
for the top of the UV unit, as it will flex less and be less prone to scratches. A
combined unit, with switchable UV and white tubes, doubles as an exposure
unit and a light-box for lining up double- sided artworks. If you do a lot of
double-sided PCBs, it may be worth making a double-sided exposure unit,
where the PCB can be sandwitched between two light sources to expose both
sides simultaneously. To find the required exposure time for a particular UV
unit and laminate type, expose a test piece in 30-second increments from 2 to 8
minutes, develop, and use the time which gave the best image. Generally
speaking, overexposure is better than underexposure. For a single-sided PCB,
place the artwork’s toner side up on the UV box glass, peel off the protective
film from the laminate, and place its sensitive side down on top of the artwork.


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The laminate must be pressed firmly down to ensure good contact all over the
artwork. To expose double-sided PCBs, print the solder-side artwork as normal
and the component side mirrored. Place the two sheets together with the toner
sides facing, and carefully line them up, checking all over the board area for
correct alignment, using the holes in the pads as a guide. A light box is very
handy here, but exposure can also be done with daylight by holding the sheets
on the surface of a window. If printing errors have caused slight mis-
registration, align the sheets to average the errors across the whole PCB, to
avoid breaking pad edges or tracks when drilling. When these are correctly
aligned, staple the sheets together on two opposite sides, about 10 mm from the
edge of the board, forming a sleeve or envelope. The gap between the board
edge and staples is important to stop the paper distorting at the edge. Use the
smallest stapler you can find, so that the thickness of the staple is not much
more than that of the PCB. Expose each side, covering up the top side with a
reasonably light-proof soft cover when exposing the underside. Be very careful
when turning the board over, to avoid the laminate slipping inside the artwork
and ruining the alignment. After exposure, you can usually see a faint image of
the pattern in the photosensitive layer.

Developing
       Do not use sodium hydroxides for developing photo resist laminates. It is
a completely and utterly dreadful stuff for developing PCBs. Apart from its
causticity, it is very sensitive to both temperature and concentration, and made-
up solution doesn’t last long. When it’s too weak it doesn’t develop at all, and
when too strong it strips all the resist off. It is almost impossible to get reliable
and consistent results, especially when making PCBs in an environment with
large temperature variations. A much better developer is a silicate-based
product that comes as a liquid concentrate. You can leave the board in it for
several times the normal developing time without noticeable degradation. This
also means that it is not temperature critical—no risk of stripping at warmer
temperatures. Made-up solution also has a very long shelf-life and lasts until it’s
used up. You can make the solution up really strong for very fast developing.
The recommended mix is 1 part developer to 9 parts water. You can check for
correct development by dipping the board in the ferric chloride very briefly—
the exposed copper should turn dull pink almost instantly. If any shiny copper-
colored areas remain, rinse and develop for a few more seconds. If the board is
under-exposed, you will get a thin layer of resist which isn’t removed by the


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developer. You can remove this by gently wiping with dry paper towel, without
damaging the pattern. You can either use a photographic developing tray or a
vertical tank for developing.


Etching
       Ferric chloride etchant is a messy stuff, but easily available and cheaper
than most alternatives. It attacks any metal including stainless steel. So when
setting up a PCB etching area, use a plastic or ceramic sink, with plastic fittings
and screws wherever possible, and seal any metal screws with silicone. Copper
water pipes may get splashed or dripped-on, so sleeve or cover them in plastic;
heat-shrink sleeving is great if you’re installing new pipes. Fume extraction is
not normally required, although a cover over the tank or tray when not in use is
a good idea. You should always use the hex hydrate type of ferric chloride,
which should be dissolved in warm water until saturation. Adding a teaspoon of
table salt helps to make the etchant clearer for easier inspection. Avoid
anhydrous ferric chloride. It creates a lot of heat when dissolved. So always add
the powder very slowly to water; do not add water to the powder, and use
gloves and safety glasses. The solution made from anhydrous ferric chloride
doesn’t etch at all, so you need to add a small amount of hydrochloric acid and
leave it for a day or two. Always take extreme care to avoid splashing when
dissolving either type of ferric chloride, as it tends to clump together and you
often get big chunks coming out of the container and splashing into the solution.
It can damage eyes and permanently stain clothing. If you’re making PCBs in a
professional environment, where time is money, you should get a heated
bubble-etch tank. With fresh hot ferric chloride, a PCB will etch in well under
five minutes. Fast etching produces better edge-quality and consistent line
widths. If you aren’t using a bubble tank, you need to agitate frequently to
ensure even etching. Warm the etchant by putting the etching tray inside a
larger tray filled with boiling water.

Tin plating
      Tin-plating a PCB makes it a lot easier to solder, and is pretty much
essential for surface mount boards. Unless you have access to a roller tinning
machine, chemical tinning is the only option. Unfortunately, tin-plating
chemicals are expensive but the results are usually worth it. If you don’t tin-
plate the board, either leave the photo resist coating on (most resists are


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intended to act as soldering fluxes) or spray the board with rework flux to
prevent the copper from oxidizing. Room-temperature tin-plating crystals
produce a good finish in a few minutes. There are other tinning chemicals
available, some of which require mixing with acid or high-temperature use.
Ensure that the temperature of the tinning solution is at least 25oC, but not more
than 40oC. If required, either put the bottle in a hot water bath or put the tinning
tray in a bigger tray filled with hot water to warm it up. Putting a PCB in cold
tinning solution will usually prevent tinning, even if the temperature is
subsequently raised. For a good tinned finish, strip the photoresist thoroughly.
Although you can get special stripping solutions and hand applicators, most
resists can be dissolved off more easily and cleanly using methanol (methylated
spirit). Hold the rinsed and dried PCB horizontal, and dribble few drops of
methanol on the surface, tilting the PCB to allow it to run over the whole
surface. Wait for about ten seconds and wipe off with a paper towel dipped in
methanol. Rub the copper surface all over with wire wool until it is bright and
shiny. Wipe with a paper towel to remove the wire wool fragments and
immediately immerse the board in the tinning solution. Don’t touch the copper
surface after cleaning, as finger marks will impair plating. The copper should
turn silver in colour within about 30 seconds. Leave the board for about five
minutes, agitating occasionally; do not use bubble agitation. For double-sided
PCBs, prop the PCB at an angle to ensure the solution gets to both sides. Rinse
the board thoroughly and rub dry with paper towel to remove any tinning crystal
deposits. If the board isn’t going to be soldered for a day or two, coat it with
either a rework flux spray or a flux pen.

Drilling
       If you have fibreglass (FR4) board, you must use tungsten carbide drill
bits. Fibreglass eats normal high-speed steel (HSS) bits very rapidly, although
HSS drills are all right for odd larger sizes (>2 mm). Carbide drill bits are
expensive and the thin ones snap very easily. When using carbide drill bits
below 1 mm, you must use a good vertical drill stand—you will break drill very
quickly without one. Carbide drill bits are available as straight-shank or thick
(sometimes called ‘turbo’) shank. In straight shank, the whole bit is the diameter
of the hole, and in thick shank, a standard-size (typically about 3.5 mm) shank
tapers down to the hole size. The straight-shank drills are usually preferred
because they break less easily and are usually cheaper. The longer thin section
provides more flexibility. Small drills for PCB use usually come with either a


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set of collets of arious sizes or a 3-jaw chuck. Sometimes the 3-jaw chuck is an
optional extra and is worth getting for the time it saves on changing collets. For
accuracy, however, 3-jaw chucks aren’t brilliant, and small drill sizes below 1
mm quickly form grooves in the jaws, preventing good grip. Below 1 mm, you
should use collets, and buy a few extra of the smallest ones, keeping one collet
per drill size, as using a larger drill in a collet will open it out and it no longer
grips smaller drills well. You need a good strong light on the board when
drilling, to ensure accuracy. A dichroic halogen lamp, under-run at 9V to reduce
brightness, can be mounted on a microphone gooseneck for easy positioning. It
can be useful to raise the working surface about 15 cm above the normal desk
height for more comfortable viewing. Dust extraction is nice, but not
essential—an occasional blow does the trick! A foot-pedal control to switch the
drill ‘off’ and ‘on’ is very convenient, especially when frequently changing bits.
Avoid hole sizes less than 0.8 mm unless you really need them. When making
two identical boards, drill them both together to save time. To do this, carefully
drill a 0.8mm hole in the pad near each corner of each of the two boards, getting
the centre as accurate as possible. For larger boards, drill a hole near the centre
of each side as well. Lay the boards on top of each other and insert a 0.8mm
track pin in two opposite corners, using the pins as pegs to line the PCBs up.
Squeeze or hammer the pins into the boards, and then into the remaining holes.
The two PCBs are now ‘nailed’ together accurately and can be drilled together.

Cutting
       A small guillotine is the easiest way to cut fibreglass laminate. Ordinary
saws (bandsaws, jigsaws, and hacksaws) will be blunted quickly unless these
are carbide-tipped, and the dust can cause sink irritation. A carbide tile-saw
blade in a jigsaw might be worth a try. It’s also easy to accidentally scratch
through the protective film when sawing, causing photoresist scratches and
broken tracks on the finished board. A sheet-metal guillotine is also excellent
for cutting boards, provided the blade is fairly sharp. To make cut-outs, drill a
series of small holes, punch out the blank, and file to size. Alternatively, use a
fretsaw or small hacksaw, but be prepared to replace blades often. With practice
it’s possible to do corner cutouts with a guillotine but you have to be very
careful that you don’t over-cut!
SOLDERING



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    Soldering is the joining together of two metals to give physical bonding and
good electrical conductivity. It is used primarily in electrical and electronic
circuitry. Solder is a combination of metals, which are solid at normal room
temperatures and become liquid at between 180 and 200°C. Solder bonds well
to various metals, and extremely well to copper.
      Soldering is a necessary skill you need to learn to successfully build
electronics circuits. It is the primary way how electronics components are
connected to circuit boards, wires and sometimes directly to other components.
      To solder you need a soldering iron. A modern basic electrical soldering
iron consists of a heating element, a soldering bit (often called the tip), a handle
and a power cord. The heating element can be either a resistance wire wound
around a ceramic tube, or a thick film resistance element printed onto a ceramic
base. The element is then insulated and placed into a metal tube for strength and
protection. This is then thermally insulated from the handle. The heating
element of soldering iron usually reaches temperatures of around 370 to 400°C
(higher than needed to melt the solder). The soldering bit is a specially shaped
piece of copper plated with iron and then usually plated with chrome or iron.
The tip planting makes it very resistant to aggressive solders and fluxes.
The strength or power of a soldering iron is usually expressed in Watts. Irons
generally used in electronics are typically in the range 12 to 25 Watts. Higher
powered iron will not run hotter, but it will have more power available to
quickly replace heat drained from the iron during soldering. Most irons are
available in a variety of voltages, 12V, 24V, 115V, and 230V are the most
popular. Today most laboratories and repair shops use soldering irons, which
operate at 24V (powered by isolation transformer supplied with the soldering
iron or by a separate low voltage outlet). You should always use this low
voltage where possible, as it is much safer. For advanced soldering work (like
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with a temperature control. In this type of soldering irons the temperature may
be usually set between 200 degC and 450 degC. Many temperature-controlled
soldering irons designed for electronics have a power rating of around 40-50W.
They will heat fast and give enough power for operation, but are mechanically
small (because the temperature controller stops them from overheating when
they are not used).
      You will occasionally see gas-powered soldering irons which use butane
rather than the mains electrical supply to operate. They have a catalytic element
which, once warmed up, continues to glow hot when gas passes over them. Gas-
powered soldering irons are designed for occasional "on the spot" use for quick
repairs, rather than for mainstream construction or assembly work.
      You need to be careful in soldering because most electronic components
are fragile, and heat sensitive. Usually our biggest concern is heat. Low enough
soldering temperature and short enough soldering time keeps components in
good shape. Electronics components are designed so that they can take high
temperatures on their contacts/wires for some time without damage (to
withstand the soldering). Prolonged exposure to high temperature will heat up
when inside of the component can cause damage to it.
      Currently, the best commonly available, workable, and safe solder alloy
is 63/37. That is, 63% lead, 37% tin. It is also known as eutectic solder. Its most
desirable characteristic is that its solids ("pasty") state, and its liquid state occur
at the same temperature -- 361 degrees F. The combination of 63% lead and
37% tin melts at the lowest possible temperature. Nowadays there is tendency to
move to use lead free solders, but it will takes years until they will catch on
normal soldering work. Lead free solders are nowadays available, but they are
generally more expensive and/or harder to work on than traditional solders that
have lead in then,




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      The metals involved are not the only things to consider in a solder. Flux
is vital to a good solder joint. Flux is an aggressive chemical that removes
oxides and impurities from the parts to be soldered. The chemical reactions at
the point(s) of connection must take place for the metals to fuse. RMA-type flux
(Rosin Mildly Active) is the least corrosive of the readily available materials,
and provides an adequate oxide removal.
      In electronics a 60/40 fluxed core solder is used. This consists of 60%
Lead and 40% Tin, with flux cores added through the length of the solder.
      There are certain safety measures which you should keep in mind when
soldering. The tin material used in soldering contains dangerous substances like
lead (40-60% of typical soldering tins are lead and lead is poisonous). Also the
various from the soldering flux can be dangerous. While it is true that lead does
not vaporize at the temperatures at which soldering is typically done, particulate
matter is just as dangerous as fumes would be in terms of poisoning and there is
particulate lead present to some extent in the fumes from your flux.
      When soldering keep the room well ventilated and use a small fan or
fume trap. A proper fume trap or a fan will keep the most pollution away from
your face. Professional electronics workshops use expensive fume extraction
systems to protect their workers (needed for working safety reasons). Those
fume extraction devices have a special filter, which filters out the dangerous
fumes. If you can connect a duct to the output from the trap to the outside, that
would be great.
      Always wash hands prior to smoking, eating, drinking or going to the
bathroom. When you handle soldering tin, your hands will pick up lead, which
needs to be washed out from it before it gets to your body. Do not eat, drink or
smoke whilst working with soldering iron. Do not place cups, glasses or a plate
of food near your working area.




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      Wash also the table sometimes. As you solder, at times there will be a bit
of spitting and sputtering. If you look you'll see tiny balls of solder that shoot
out and can be found on your soldering table.
      The soldering iron will last longer with proper care. Before and during
use wipe the bit on a damp sponge. Most bench stands incorporate a sponge for
this purpose. When using a new bit, apply solder to it as it heats up. Always
keep a hot iron in a bench stand, or suspended by the hook, when not in use.
Turn of the iron when you do not use it. Periodically remove the bit and clear
away any oxide build up. Regularly check the mains lead for burns or other
damage (change mains lead if necessary).




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   PCB LAYOUT




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                  ESTIMATE




COST ESTIMATION



Item                          No            Price

RFID READER                   1     Rs.2000

RFID TAG                      3     Rs.225

PIC 16F877A                   1     Rs.220

MAX 232                       1     Rs.30

DIODES                        4     Rs.1.60

CAPACITORS                    8     Rs.0.80

LCD                           1     Rs.250

RESISTORS                     2     Rs.2




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PCB                             1   Rs.180

TRANSFORMER                       1   Rs.110

CRYSTAL OSCILLATOR                1   Rs.5.50

IC BASES                          2   Rs.40

WIRE                              1   Rs.35

9 PIN D CONNECTOR                 1   Rs.20

TOTAL                                 Rs.3090.20




                     CONCLUSION


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                              CONCLUSION




      This project is based on microcontrollers. As this is based on AT89S51
which is a commonly used microcontroller, the control and programming is
quite easy. This is just a humble effort to produce a prototype for a device
which helps in keeping an exact record of student attendance using RFIDs
module. Using this device, we can easily detect the difference in power



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withdrawal of RFID tags and it is user friendly. This system can be easily
installed any location where a 220 v power supply is available.

      Our project has been a humble effort to produce a prototype for a device
which helps in keeping an exact record of student attendance using RFIDs
module , and we believe our device will find use in various day to day fields.




                          BIBLIOGRAPHY


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                      BIBLIOGRAPHY


  www.efymag.com

  www.alldatasheets.com

  Electronics For You Magazine




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                APPENDIX




             Data sheet of RFID




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            DATA SHEET OF PIC




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