project report

MICROCONTROLLER PROJECT QUIZ BUZZER

CHARUSAT (B.Tech EC) Page 1

Project

On

QUIZ BUZZER

By

TAILOR ROHAN B (D10EC144)

THAKKAR PRATIK P (D10EC145)

PANCHAL AMAN R (D10EC146)

Guided

By

Dr. UTKAL MEHTA



AIM:- To make A QUIZ BUZZER by interfacing 7-SEGMENT

With 8051(using IC AT89S51)

TOOLS USED(SOFTWARES):- KEIL, MULTISIM-11

DESCRIPTION:-

Quiz buzzer system has eight input pins corresponding to eight teams. The

output is displayed on a seven segment display (interfaced with

microcontroller), which shows the number corresponding to the team which

has pressed the button first. A buzzer is also sounded for a small duration to

give an acoustic alarm. The connections of the seven segment, input pins

and output pins is shown in the circuit diagram.

When the system starts, the seven segment does not displays any output. The

microcontroller keeps scanning the input pins. As soon as any one of the

inputs is pressed, the buzzer sounds for a small duration. The seven segment

displays the number corresponding to the input pressed. Now even if any

other input pin is pressed, there will be no effect on the system till the time

the stop pin is pressed to reset the system.

There are a total of nine input pins. Eight pins of port P1 of the

microcontroller are corresponding to eight inputs and one stop pin for

resetting the buzzer system. On the output side a seven segment is connected

to display the corresponding output number. There is also a provision for

sounding a buzzer for a small duration. Here common cathode 7-segment is

used to interfacing with microcontroller IC AT89S51. Configuration of

common cathode 7-segment is shown in below figure.

Figure: Common cathode seven segment display



CIRCUIT DIAGRAM:-



PROGRAM (Assembly language):-

org 0000h ;starting position

clr p3.4 ;configure pin 3.4 as output pin (buzzer OFF)

mov r1,#00h ;register R1 as a counter

mov p2,#00h ;configure port 2 as output (seven segment)

mov dptr,#0300h ;load look table address

setb p3.0 ;configure pin 3.0 as input (to reset buzzer)

start: mov p1,#0ffh ;configure port 1 as input (8 input switch)

l3:mov r2,p1 ;copy data from P1 to register R2

cjne r2,#0ffh,l2 ;check switch is pressed or not

sjmp l3 ;check until any one key pressed

l2:setb c ;set carry bit

clr a ;clear accumlator

mov a,p1 ;copy data from P1 to accumlator

anl p1,a ;mask other keys if one key pressed first

again:rrc a

inc r1

jc again ; check which switch is pressed

clr a

mov a,r1 ;copy number of which switch is pressed first

setb p0.1 ;turn ON buzzer



acall delay ;turn on buzzer for 1 second delay

clr p0.1 ;turn OFF buzzer

movc a,@a+dptr ;read value from look table for 7-segment

mov p2,a ;send data from acc to port 2 to turn on 7-segment

here:jb p3.0,here ;check reset pin 3.0 is pressed or not

mov p2,#00h ;turn OFF seven segment

mov r1,#00h ;clear reg. R1

sjmp start ;restart program again

delay:mov tmod,#01h ;use timer 0 in mode 1

mov r4,#32h ;take a counter with 32H value

l5:mov th0,#0b8h ;load th0 with 0b8h

mov tl0,#63h ;load tl0 with 63h

l1:jnb tf0,l1 ;check timer overflow flag 0 is set or not

djnz r4,l5 ;decrement R4 & jump if not zero to l5

clr tr0 ;clear timer run bit 0

ret ;return to main program



//load code of common cathode seven segment to code space//

org 0300h ;take 0300h as look table address

db 00h ;turn off seven segment

db 86h ;display 1 to seven segment

db 0dbh ;display 2 to seven segment

db 0cfh ;display 3 to seven segment

db 0e6h ;display 4 to seven segment

db 0edh ;display 5 to seven segment

db 0fdh ;display 6 to seven segment

db 87h ;display 7 to seven segment

db 0ffh ;display 8 to seven segment

end ;end of the asm source file

Disclaimer: Small portion of program code is hidden to

prevent direct use of code. Code is just for guidance.



APPLICATION:-

The quiz buzzer systems are widely used in school, colleges and TV

programs. The team which presses the buzzer earliest is entitled to give the

answer. At times it becomes very difficult to identify which team has

pressed the button when two teams press the buzzer within a very small time

gap. In such cases the decision can be biased due to human intervention. The

quiz buzzer presented here takes care of the aforesaid problem. This quiz

buzzer disables the other inputs as soon as the first buzzer is pressed. This

quiz buzzer can be used for a maximum of eight teams. It is build around

8051 microcontroller (AT89S51).

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