05-01-2012, 12:06 PM
[attachment=15869]
Barcode Based Employee Attendance
ABSTRACT
A barcode reader (or barcode scanner) is an electronic device for reading printed barcodes. Like a flatbed scanner, it consists of a light source, a lens and a light sensor translating optical impulses into electrical ones. Additionally, nearly all barcode readers contain decoder circuitry analyzing the barcode's image data provided by the sensor and sending the barcode's content to the scanner's output port. The hand-held laser scanner does not have to be close to the bar code in order to do its job. It uses a system of mirrors and lenses to allow the scanner to read the bar code regardless of orientation, and can easily read a bar code up to 24 inches away. To reduce the possibility of errors, a laser scanning may perform up to 500 scans per second. Specialized long-range laser scanners are capable of reading a bar code up to 30 feet away. In this project, the Barcode scanner is interfaced with the micro controller and when the barcode card is brought to the sight of the scanner, it reads the data on the barcode card and displays on the LCD. If the data of the card is matched with the data in the program memory then it compares and displays authorized message. If the data is not matched it displays unauthorized. For authorized message, the door gets opened and the person gets in after sometime the door gets closed (A relay will be energized). If it is an unauthorized person it alerts the persons through a buzzer. This project uses regulated 5v, 500mA power supply. 7805, a three terminal voltage regulator is used for voltage regulation. Bridge type full wave rectifier is used to rectify the ac output of secondary of 230/12v step down transformer. The RFID module requires a separate +5v power supply.
Microcontroller
Microcontroller IC atmel89c51 is heart of our project. We select this Microcontroller IC for our project for following no. of advantages.
1) Internal 1k bytes*14words of electrically erasable programmable read only memory with internal EPROM.
2) 32 I/O pins with 25mA source capability.
3) Operating voltage of 3.5 to 6V D.C. which is easily available by using voltage regulator IC.
4) Internal 64 byte RAM to store temporally storage of data.
5) two timer .
6) Three interrupt sources are available.
Microcontroller sends the pulse & wait for the echo to come back. If the echo does not occur then it will again go to transmitting the pulse & the same procedure is repeated until the echo pulse is received.
Transmitter TAG
In this system we have used Bar coded tags . So this data is applied is converted by the bar code encoder this will convert the parallel data in serial format..
Power Supply
For our all IC we require 5V D.C. supply which can be generated by step down transformer, full wave bridge rectifier, filter condenser & voltage regulator IC7805. 12V supply for motor is generated separately using the same procedure as above
Receiver
This stage receives the signal, removes the noise if any associated with the signal. Then demodulates it means carrier is suppressed & original signal is retrieved. This is also an integrated circuit which complies all required system in built. The received data is send to the decoder .this is special type receiver operates on the 5 volt.
Decoder
This stage decodes the coded signal & gets the signal in the readable form to the microcontroller. That is in the digital form. Microcontroller reads the signal & takes action accordingly.
LCD Display
It is a back light LCD; it has its own processor so it can be called as intelligent LCD.
It is treated as other peripheral device. So it needs to be interfaced like any other device.
It has 8 data lines and 3 control lines, Using these 3 control lines one can read and write into the LCD, it also has internal RAM.IT also has address location specifying the particular location on particular lines. For 1 line the address starts from 80H through 8F so one can specify the location of the character or number be displayed.
These 3 control lines are R/S: register select, R/W: read /Write, E: Enable
Display section includes 16*1 back lights LCD interfaced with the microcontroller. It has own processor to control the display information. So the interfacing of the LCD is done same as peripherals. It has own commands, addresses for the different locations on different lines. Here 16 character one line LCD with 5 * 7 dot matrix pattern LCD is used it require 5v supply for operation & same 5v for back light LED. The back light is having greenish yellow shade of light. It has 8 data lines for sending the data over it & 3 control lines to communicate with the LCD. Before reading & writing to LCD its busy status need to be checked.
LCD gives more advantages & as compared to the LED 7 segment displays. They are as follows
1) The decline in price of LCD
2) The ability to display number, character & graphics. This is in contrast to LED which is limited to numbers & little character.
3) In corporation of refreshing controller into the LCD, thereby relieving the CPU of the task of refreshing the LDC. In contrast, the LED must be refreshed by the CPU (or in some other way) to keep displaying the data.
4) Ease of programming for characters & graphics.
Crystal & Reset Circuit
12MHz quartz ceramic crystal is connected between pin XTAL1, & XTAL2 of Microcontroller to produce machine cycle for fetch & execution of instruction. And at pin 9RST pin we connect R.C n/w to provide reset pulse when power is turn ON so that program execution starts from memory location 0000H.
Max 232
This an converting IC which connect the microcontroller to serial port of the personal computer. This is RS 232 level shifter to microcontroller logic level. This is interfacing integrated chip which has bidirectional and unidirectional logic gate. The capacitors are connected as per specified for level shifting.
Serial port
This is serial communication port of the computer which enables the communication by serial communication through RS232 standard protocols. The interfacing software is also installed in the computer.
