Karthik Datt, Banglore, India
WORKING OF CIRCUIT:
Shown in circuit diagram tab 1.
Supply Section of this circuit consists of a 12 volts adaptor, and a IC 7805 IC. The output of the second regulator(IC 7805) is +5 volts, which is used for all other digital applications.
The voting machine consists of six keys, which are connected to six separate pins of microcontroller. Port pins P3.2 to P3.7.Which are usually made high to act as input port and other side of key is connected to P2.2 which acts as active high input in order to disable the keypad until interrupt occurs.
The display section uses the port 1 of microcontroller. This port is in open drain configuration and as a result, pull up resistors should be provided for its normal operation. The contrast of this LCD display is adjusted by changing the value of a resistor which is grounded at the other end.
A Buzzer is used to indicate whether a voter has exercised his vote correctly and also for recognizing any malpractice during the whole process. This buzzer is connected to a supply of +5 volt by means of a pull up resistor.
The EEPROM IC 24C08 is a serial electrically erasable and programmable read-only memory. It is connected to microcontroller through two pins SDA and SCL. This EEPROM is used to store the details relating to the voter and indicating whether a voter has already voted or not and also the date and time of voting.
SM630 device operates at 57600 baudrate which is achieved by setting TH1 and TL1 register to FFH in auto reload mode by which we can achieve baudrate of 28800 and by setting MSB of PCON register to high we can double the baudrate to 57600.
SM630 has 4 pins Vcc, gnd ,Tx and Rx.The Tx of SM630 is connected to serial receive input of microcontroller which is nothing but P3.0 pin. Similarly Rx of SM630 is connected to serial transmit pin of microcontroller P3.1.
RS-232 which is a simple, universal and well understood standard is applied in this project. It converts the active high condition of PC(-3 volt to -12 volt) to the active high condition of the microcontroller(+5 volt) and vice versa. Similarly the active low condition of the microcontroller ( 0 volt) is transformed to the active low condition of the PC (+3volt to +12volt) and act as a perfect means of interfacing microcontroller and PC. MAX 232 is used in the serial communication to convert RTL to TTL.