CHAPTER ONE

INTRODUCTION

1.1   BACKGROUND TO THE STUDY

Quiz buzzers are used often at places like educational institutions where it is required for game shows and also in live quiz competitions broadcasted via television. A quiz buzzer allows any user to press the switch quickly in response to a question posed during competitions that are conducted in schools and colleges. The pressed switch gives a buzzing sound or alarm for some duration of time and the reaction time is very small. Buzzer can also be used in different applications such as annunciator panels; electronic metronome microwave oven and other house hold application.

Conventional systems require human intervention to decide which team has pressed the button and this system can be erroneous and even biased. Another problem arises when two members pressed the button at a negligible interval and it is difficult to guess who has pressed the buzzer first. Here we designed an automatic quiz buzzer system such that when more than one team presses the buzzer, the delay is accurately taken into account and number is displayed. We build the circuit using a microcontroller which scans the input from push buttons and displays the corresponding number on a display device. It is a simple circuit with minimum number of components and sans any complexities. The microcontroller takes into account the time delay between two buttons and the accurate number is displayed. Even though this system is only for 8 teams, more teams can be added by using another set of 8 push buttons.

1.2   OBJECTIVE OF THE STUDY

The aim of this project is to designed and construction of automatic quiz buzzer system such that when more than one team presses the buzzer, the delay is accurately taken into account and number is displayed.

1.3   JUSTIFICATION OF THE STUDY

The circuit is a simple embedded system with a set of 8 push buttons being the input devices, a microcontroller as the controller and the output devices being a buzzer and a display. The whole operation is carried out by a microcontroller through a program written in C language and dumped inside the microcontroller. When one of the buttons is pressed, the buzzer starts ringing and the corresponding number is displayed on the liquId crystal display. A quiz buzzer circuit can be implemented in several ways with the use of various controllers. These controllers include 555 timer and microcontrollers. The 555 timer based buzzer circuit is a simple and low-cost device wherein the time duration is determined by the resistor and capacitor value (RC constant). A microcontroller based buzzer circuit is a programmable timer wherein the time duration can be varied by changing the program code of the microcontroller.

1.4   SCOPE OF THE STUDY

The whole design process involves six steps. First step requires designing the circuit; the second step is drawing the circuit on any software like Proteus. The third step involves writing the code using high level language or assembly language and then compiling it on a software platform like Kielu Vision. The fourth step is dumping the code in microcontroller and fifth step is simulating the circuit. The circuit involves using five major components – a Microcontroller, 8 SPST push buttons, a buzzer and liquid crystal display. The microcontroller used in this case is AT89C51, an 8 bit microcontroller manufactured by Atmel.

Reset Circuit Design

The reset resistor is selected such that the voltage at the reset pin, across this resistor is at minimum of 1.2V and the width of the pulse applied to this pin is greater than 100ms. Here we select a resistor of 100K ohms and a capacitor of 10uF.

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