# 8 CANDIDATE QUIZ BUZZER USING 8051 MICROCONTROLLER AT89C51 PDF

Shall be very mauch thankful to you. IF you any query about any project related than write your comment in comment box. 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.

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Page 1. Page 2. The input to the circuit is applied from the regulated power supply. The a. The output obtained from the rectifier is a pulsating d. So in order to get a pure d. Now, this voltage is given to a voltage regulator to obtain a pure constant dc voltage. Fig: Power supply. Page 3. Usually, DC voltages are required to operate various electronic equipment and these voltages are 5V, 9V or 12V. But these voltages cannot be obtained directly.

Thus the a. This is done by a transformer. Thus, a step down transformer is employed to decrease the voltage to a required level. The output from the transformer is fed to the rectifier. It converts A. The rectifier may be a half wave or a full wave rectifier.

In this project, a bridge rectifier is used because of its merits like good stability and full wave rectification. Page 4. The Bridge rectifier is a circuit, which converts an ac voltage to dc voltage using both half cycles of the input ac voltage. The Bridge rectifier circuit is shown in the figure.

The circuit has four diodes connected to form a bridge. The ac input voltage is applied to the diagonally opposite ends of the bridge. The load resistance is connected between the other two ends of the bridge. The conducting diodes will be in series with the load resistance R L and hence the load current flows through R L. The conducting diodes D2 and D4 will be in series.

Thus a bi-directional wave is converted into a unidirectional wave. Page 5. Page 6. Capacitive filter is used in this project. It removes the ripples from the output of rectifier and smoothens the D.

Output received from this filter is constant until the mains voltage and load is maintained constant. However, if either of the two is varied, D. Therefore a regulator is applied at the output stage.

As the name itself implies, it regulates the input applied to it. A voltage regulator is an electrical regulator designed to automatically maintain a constant voltage level. In this project, power supply of 5V and 12V are required. In order to obtain these voltage levels, and voltage regulators are to be used. The first number 78 represents positive supply and the numbers 05, 12 represent the required output voltage levels. These regulators can provide local on-card regulation, eliminating the distribution problems associated with single point regulation.

Each type employs internal current limiting, thermal shut-down and safe area protection, making it essentially indestructible. If adequate heat sinking is provided, they can deliver over 1 A output current. Although designed primarily as fixed voltage regulators, these devices can be used with external components to obtain adjustable voltage and currents. Page 7. What is all this about? The whole story began in the far 80s when Intel launched its series of the microcontrollers labeled with MCS Although, several circuits belonging to this Series had quite modest features in comparison to the new ones; they took over the world very fast and became a standard for what nowadays is meant by a word microcontroller.

Page 8. The reason for success and such a big popularity is a skillfully chosen configuration which satisfies needs of a great number of the users allowing at the same time stable expanding refers to the new types of the microcontrollers. That is the reason for having a great number of various microcontrollers which actually are solely upgraded versions of the What is it what makes this microcontroller so special and universal so that almost all the world producers manufacture it today under different name?

RAM is bytes. Two-level Program Memory Lock. Page 9. Six Interrupt Sources. Low-power Idle and Power-down Modes. Page Pin No. Reset pin; Active high. Input Rx for serial communication. Output Tx for serial communication. External interrupt 1. External interrupt 2.

Timer1 external input. Timer2 external input. Write to external data memory. P 3 pins. Read from external data memory Quartz crystal oscillator up to 24 MHz. Ground 0V. High-order address bits when interfacing with external memory. Program store enable; Read from external program memory Address Latch Enable. Program pulse input during Flash programming. Vpp P 0. Low-order address bits when interfacing with external memory. Supply voltage; 5V up to 6. BC is general purpose silicon, NPN, bipolar junction transistor.

It is used for amplification and switching purposes. The current gain may vary between and The maximum DC current gain is Its equivalent transistors are 2N and 2SC These equivalent transistors however have different lead assignments. The variants of BC are A, B and C which vary in range of current gain and other characteristics. The transistor terminals require a fixed DC voltage to operate in the desired region of its characteristic curves.

This is known as the biasing. For amplification applications, the transistor is biased such that it is partly on for all input conditions. The input signal at base is amplified and taken at the emitter. BC is used in common emitter configuration for amplifiers. The voltage divider is the commonly used biasing mode.

For switching applications, transistor is biased so that it remains fully on if there is a signal at its base. In the absence of base signal, it gets completely off. A seven segment display is the most basic electronic display device that can display digits from They find wide application in devices that display numeric information like digital clocks, radio, microwave ovens, electronic meters etc. The most common configuration has an array of eight LEDs arranged in a special pattern to display these digits.

Every LED is assigned a name from 'a' to 'h' and is identified by its name. A seven segment is generally available in ten pin package. While eight pins correspond to the eight LEDs, the remaining two pins at middle are common and internally shorted. The common is connected to ground and a particular LED glows when its corresponding pin is given high.

In CA arrangement, the common pin is given a high logic and the LED pins are given low to display a number. The piezo buzzer produces sound based on reverse of the piezoelectric effect.

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## 8 CANDIDATE QUIZ BUZZER USING 8051 MICROCONTROLLER

Page 1. Page 2. The input to the circuit is applied from the regulated power supply. The a. The output obtained from the rectifier is a pulsating d. So in order to get a pure d. Now, this voltage is given to a voltage regulator to obtain a pure constant dc voltage.

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## 8 Candidate Quiz Buzzer Using 8051

In this paper we will see how the circuit design is made and how the buzzer works and displays the information on the screen. The AT89C51 microcontroller is a 40 pin package in which 32 pins can be used for input and output purposes. We use 8 switches and they are connected individually to port1 pins and we make a serial line for all the 8 switches so that they can be connected to a buzzer and when any switch is presses a buzzer is blown. We use a seven segment display to display the information of the switch which is presses. The code for this application is written in such a way that when any input switch is presses the corresponding switch number is displayed in the LCD screen.

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## Quiz Buzzer Circuit using 8051 Microcontroller and 555 Timer

Quiz buzzer systems are mostly used in schools, colleges 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. Buzzers can also be used in different applications such as annunciator panels, electronic metronome microwave ovens, and other household applications. A Quiz buzzer circuit can be implemented in several ways with the use of various controllers. These controllers include timers and microcontrollers. The timer based buzzer circuit is a simple and low-cost device wherein the time duration is determined by the resistor and capacitor values RC constant.