8 CANDIDATE QUIZ BUZZER USING 8051 MICROCONTROLLER

MINIPROJECT REPORTSubmitted byVANI SIn partial fulfillment for the award of the degreeofBACHELOR OF TECHNOLOGYinELECTRICAL AND ELECTRONICS ENINEERING

KMEA ENGINEERING COLLEGEEDATHALAAPRIL 2013

DEPARTMENT OF ELECTRICALANDELECTRONICS ENGINEERINGBONAFIDE CERTIFICATEThis is to certify that the mini project titled8 CANDIDATE QUIZ BUZZER USING 8051 MICROCONTROLLERwas prepared and presented byVANI Sof the Sixth Semester of Electrical and Electronics Engineeringin partial fulfillment of requirement for the award ofDegree of Bachelor of Technology in Electrical and Electronics Engineering under M.G. University during the year 2013

Prof. GEORGE T.V Dr .HASEENA.H INTERNAL EXAMINER HEAD OF DEPARTMENT

ACKNOWLEDGEMENT

We thank Lord Almighty for his blessingsWe acknowledge with great gratitude to all those who helped us to complete our mini project.We express our heartfelt thanks to Prof .C .I. Abdul Rahiman, Director, KMEA Engineering College.We thank Dr. Rajesh V. G., Principal KMEA Engineering College for the immense support he has provided.We extend our sincere thanks to Dr. Haseena H, Head of the Dept. EEE for the mini projectWe thank Prof George T.V, Project Coordinator, EEE Department, & Mrs. Karthika Krishna, Project Coordinator, ECE Department for their support and assistance.Words are few but feelings are more to appreciate our family and friends for the constant support and encouragement provided for our mini project and also for reviewing this document and for giving us valuable suggestions.

CHAPTER 1 INTRODUCTION

A "buzzersystem" is a common name for a device used to indicate which player has signaled that he or she wishes to answer a question first. They are necessary component to playing quiz bowl matches when available, as they help avoid any ambiguities as to who buzzed in first. When no buzzers are present, teams must playslap bowl, where buzzing is indicated by slapping the desk or saying something like "buzz". While using a buzzer system, other players are prevented from buzzing after the first player until the system is reset; for this reason, buzzer systems are sometimes called lockout systems". Ideally, a buzzer system consists of a control box which sits near the moderator, which connects to individual pushbuttons or paddles held by each player. The best buzzers trigger a sound and turn on a light specific to the player who buzzed when an individual pushbutton or paddle is used. Any one component of the system held by an individual player is often referred to as a "buzzer" as well.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.

CHAPTER 2OPERATION

2.1 INTRODUCTION

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 (AT89C51).

2.2 CIRCUIT EXPLANATION

This quiz buzzer system has eight input pins corresponding to eight teams. The output is displayed on aseven 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. 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 abuzzerfor a small duration.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.

2.3 BLOCK DIAGRAM

Fig 2.1 Block diagram

2.4 CIRCUIT DIAGRAM

Fig 2.2 Circuit Diagram

2.5 DESIGN USING PROTEUS

Fig 2.3 Design Using Proteus

2.6 WORKING PROCEDUREThis 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. 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.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.A seven segment consists of eight LEDs which are aligned in a manner so as to display digits from 0 to 9 when proper combination of LED is switched on. Seven segment uses seven LEDs to display digits from 0 to 9 and the eighth LED is used for the dot. Seven segment is available in two configurations

1) Common anode2) Common cathodeHere common anode seven segment display is used because the output current of the microcontroller is not sufficient enough to drive the LEDs, similar to the case of driving an LED. The pins a to g of the Seven Segment are connected to the Port P2 of the microcontroller. The common pin of the seven segment is connected to Vcc. The h has not been used, which is the dot pin of the controller. Since the seven segment display works on negative logic, we will have to provide logic 0 to the corresponding to make a LED glow. When the values corresponding to the digits 0 to 9 are given on the output port, the digit gets displayed on the seven segment.

CHAPTER 3HARDWARE TOOLS

The various components used in the circuit include: Microcontroller- AT89S51

Transistor ( BC548)

Resistors(8.2k,2.2k,1k,10)

Capacitor

Seven Segment Display

Diode (1N4007)

Push Button Switch

Power Supply

Piezo buzzer

3.1 MICROCONTROLLER- AT89C51

3.1.1 FeaturesCompatible with MCS-51 Products4 Kbytes of In-System Reprogrammable Flash Memory. Endurance 1,000 Write/Erase CyclesFully Static Operation: 0 Hz to 24 MHzThree-Level Program Memory Lock128 x 8-Bit Internal RAM32 Programmable I/O LinesTwo 16-Bit Timer/CountersSix Interrupt SourcesProgrammable Serial ChannelLow Power Idle and Power Down Modes 3.1.2 DescriptionThe AT89C51 is a low-power, high-performance CMOS 8-bit microcomputer with 4 Kbytes of Flash Programmable and Erasable Read Only Memory (PEROM). The device is manufactured using Atmels high density nonvolatile memory technology and is compatible with the industry standard MCS-51 instruction set and pinout.The on-chip Flash allows the program memory to be reprogrammed in-system or by a conventional nonvolatile memory programmer. By combining a versatile 8-bit CPU with Flash on a monolithic chip, the Atmel AT89C51 is a powerful microcomputer which provides a highly flexible and cost effective solution to many embedded control applications.The AT89C51 provides the following standard features: 4Kbytes of Flash, 128 bytes of RAM, 32 I/O lines, two 16-bit timer/counters, a five vector two-level interrupt architecture, a full duplex serial port, on-chip oscillator and clock circuitry. In addition, the AT89C51 is designed with static logic for operation down to zero frequency and supports two software selectable power saving modes. The Idle Mode stops the CPU while allowing the RAM, timer/counters.3.1.3 Pin Diagram

Fig 3.1 Pin Diagram

3.1.4 Pin descriptionVCCSupply voltage.GNDGround.Port 0Port 0 is an 8-bit open drain bidirectional I/O port. As an output port each pin can sink eight TTL inputs. When 1s are written to port 0 pins, the pins can be used as high-impedance inputs. Port 0 may also be configured to be the multiplexed low order address/data bus during accesses to external program and data memory. In this mode P0 has internal pull-ups. Port 0 also receives the code bytes during Flash programming, and outputs the code bytes during program verification. External pull-ups are required during program verification.Port 1Port 1 is an 8-bit bidirectional I/O port with internal pull-ups. The Port 1 output buffers can sink/source four TTL inputs. When 1s are written to Port 1 pins they are pulled high by the internal pull-ups and can be used as inputs. As inputs, Port 1 pins that are externally being pulled low will source current (IIL) because of the internal pull-ups. Port 1 also receives the low-order address bytes during Flash programming and program verification.

Port 2Port 2 is an 8-bit bidirectional I/O port with internal pull-ups. The Port 2 output buffers can sink/source four TTL inputs. When 1s are written to Port 2 pins they are pulled high by the internal pull-ups and can be used as inputs. As inputs, Port 2 pins that are externally being pulled low will source current (IIL) because of the internal pull-ups. Port 2 emits the high-order address byte during fetches from external program memory and during accesses to external data memory that uses 16-bit addresses (MOVX @ DPTR). In this application it uses strong internal pull-ups when emitting 1s. During accesses to external data memory that uses 8-bit addresses (MOVX @ RI), Port 2 emits the contents of the P2 Special Function Register. Port 2 also receives the high-order address bits and some control signals during Flash programming and verification.Port 3Port 3 is an 8-bit bidirectional I/O port with internal pull-ups. The Port 3 output buffers can sink/source four TTL inputs. When 1s are written to Port 3 pins they are pulled high by the internal pull-ups and can be used as inputs. As inputs, Port 3 pins that are externally being pulled low will source current (IIL) because of the pull-ups. Port 3 also serves the functions of various special features of the AT89C51 as listed below:Table 3.1 Special Features of Port 3

Port 3 also receives some control signals for Flash programming and Programming verification.RSTReset input. A high on this pin for two machine cycles while the oscillator is running resets the device.ALE/PROGAddress Latch Enable output pulse for latching the low byte of the address during accesses to external memory.This pin is also the program pulse input (PROG) during Flash programming. In normal operation ALE is emitted at a constant rate of 1/6 the oscillator frequency, and may be used for external timing or clocking purposes. Note, however, that one ALE pulse is skipped during each access to external Data Memory. If desired, ALE operation can be disabled by setting bit 0 of SFR location 8EH. With the bit set, ALE is active only during a MOVX or MOVC instruction. Otherwise, the pin is weakly pulled high. Setting the ALE-disable bit has no effect if the microcontroller is in external execution mode.PSENProgram Store Enable is the read strobe to external program memory. When the AT89C51 is executing code from external program memory, PSEN isactivated twice each machine cycle, except that two PSEN activations are skipped during each access to external data memory.EA/VPPExternal Access Enable. EA must be strapped to GND in order to enable the device to fetch code from external program memory locations starting at 0000H up to FFFFH. Note, however, that if lock bit 1 is programmed, EA will be internally latched on reset. EA should be strapped to VCC for internal program executions. This pin also receives the 12-volt programming enable voltage (VPP) during Flash programming, for parts that require 12-volt VPP.XTAL1Input to the inverting oscillator amplifier and input to the internal clock operating circuit.XTAL2Output from the inverting oscillator amplifier.

Oscillator CharacteristicsXTAL1 and XTAL2 are the input and output, respectively, of an inverting amplifier which can be configured for use as an on-chip oscillator, as shown in Figure 1. Either a quartz crystal or ceramic resonator may be used. To drive the device from an external clock source, XTAL2 should be left unconnected while XTAL1 is driven as shown in Figure 2. There are no requirements on the duty cycle of the external clock signal, since the input to the internal clocking circuitry is through a divide-by-two flip-flop, but minimum and maximum voltage high and low time specifications must be observed.Idle ModeIn idle mode, the CPU puts itself to sleep while all the on-chip peripherals remain active. The mode is invoked by software. The content of the on-chip RAM and all the special functions registers remain unchanged during this mode. The idle mode can be terminated by any enabled interrupt or by a hardware reset. It should be noted that when idle is terminated by a hardware reset, the device normally resumes program execution, from where it left off, up to two machine cycles before the internal reset algorithm takes control. On-chip hardware inhibits access to internal RAM in this event, but access to the port pins is not inhibited. To eliminate the possibility of an unexpected write to a port pin when Idle is terminated by reset, the instruction following the one that invokes Idle should not be one that writes to a port pin or to external memory.

Power Down ModeIn the power down mode the oscillator is stopped, and the instruction that invokes power down is the last instruction executed. The on-chip RAM and Special Function Registers retain their values until the power down mode is terminated. The only exit from power down is a hardware reset. Reset redefines the SFRs but does not change the onchip RAM. The reset should not be activated before VCC is restored to its normal operating level and must be held active long enough to allow the oscillator to restart and stabilize.

Fig 3.2 Oscillator Connection

3.2 POWER SUPPLYFig 3.3 Power Supply

3.2.1 TransformerAtransformeris an electrical device that transfers energy between two circuits throughelectromagnetic induction. Making use ofFaraday's Lawin conjunction with highmagnetic permeabilitycore properties, transformers can thus be designed to efficiently change AC voltages within power networks from one voltage level to another.A transformer most commonly consists of two windings of wire that are wound around a common core to provide tight electromagneticcoupling between the windings. The core material is often a laminatediron core. The coil that receives the electrical input energy is referred to as the primary winding; the output coil is the secondary winding. Transformers covert ac electricity from one voltage level to another with little loss of power. Most power supplies use a step-down transformer to reduce the dangerously high main voltage (230V) to a safer low voltage.

3.2.2 Bridge RectifierAdiode bridgeis an arrangement of four (or more)diodesin abridge circuitconfiguration that provides the samepolarityof output for either polarity of input.When used in its most common application, for conversion of analternating current(AC) input into adirect current(DC) output, it is known as abridgerectifier. A bridge rectifier providesfull-wave rectificationfrom a two-wire AC input, resulting in lower cost and weight as compared to a rectifier with a 3-wire input from atransformerwith acenter-tappedsecondary winding. This type of single phase rectifier uses four individual rectifying diodes connected in a closed loop bridge configuration to produce the desired output. The main advantage of this bridge circuit is that it does not require a special centre tapped transformer, thereby reducing its size and cost. The single secondary winding is connected to one side of the diode bridge network and the load to the other side as shown below.

Fig 3.4 Bridge Rectifier

The four diodes labelledD1toD4are arranged in series pairs with only two diodes conducting current during each half cycle. During the positive half cycle of the supply, diodesD1andD2conduct in series while diodesD3andD4are reverse biased and the current flows through the load.

3.2.3 LM7805

The78xx(sometimesL78xx,LM78xx,MC78xx...) is a family of self-contained fixedlinear voltage regulatorintegrated circuits. The 78xx family is commonly used in electronic circuits requiring a regulated power supply due to their ease-of-use and low cost. For ICs within the family, thexxis replaced with two digits, indicating the outputvoltage(for example, the 7805 has a 5volt output, while the 7812 produces 12volts). The 78xx line are positive voltage regulators: they produce a voltage that is positive relative to a common ground. There is a related line of79xxdevices which are complementary negative voltage regulators. 78xx and 79xx ICs can be used in combination to provide positive and negative supply voltages in the same circuit.

Fig 3.5 LM7805

3.2.4 TransistorsTransistoris asemiconductor deviceused toamplifyandswitchelectronicsignals andelectrical power. It is composed ofsemiconductormaterial with at least three terminals for connection to an external circuit. A voltage orcurrentapplied to one pair of the transistor's terminals changes the current through another pair of terminals. Because the controlled (output)powercan be higher than the controlling (input) power, a transistor can amplifya signal. Today, some transistors are packaged individually, but many more are found embedded inintegrated circuits.The essential usefulness of a transistor comes from its ability to use a small signal applied between one pair of its terminals to control a much larger signal at another pair of terminals. This property is calledgain. A transistor can control its output in proportion to the input signal; that is, it can act as anamplifier. Alternatively, the transistor can be used to turn current on or off in a circuit as an electrically controlledswitch, where the amount of current is determined by other circuit elements.There are two types of transistors, which have slight differences in how they are used in a circuit. Abipolar transistorhas terminals labeled base,collector, andemitter. A small current at the base terminal (that is, flowing between the base and the emitter) can control or switch a much larger current between the collector and emitter terminals. For afield-effect transistor, the terminals are labeledgate,source, and drain, and a voltage at the gate can control a current between source and drain.The image to the right represents a typical bipolar transistor in a circuit. Charge will flow between emitter and collector terminals depending on the current in the base. Because internally the base and emitter connections behave like a semiconductor diode, a voltage drop develops between base and emitter while the base current exists. The amount of this voltage depends on the material the transistor is made from, and is referred to asVBE.

Fig 3.6 Transistor BC548

3.2.5 Seven Segment DisplayAseven-segment display(SSD), orseven-segment indicator, is a form of electronicdisplay devicefor displayingdecimal numeralsthat is an alternative to the more complexdot matrixdisplays.Seven-segment displays are widely used indigital clocks, electronic meters, and other electronic devices for displaying numerical information. The seven elements of the display can be lit in different combinations to represent thearabic numerals. Often the seven segments are arranged in anoblique(slanted) arrangement, which aids readability. In most applications, the seven segments are of nearly uniform shape and size (usually elongatedhexagons, thoughtrapezoidsandrectanglescan also be used), though in the case ofadding machines, the vertical segments are longer and more oddly shaped at the ends in an effort to further enhance readability.The numerals 6, 7 and 9 may be represented by two or more different glyphs on seven-segment displays, with or without a 'tail'.The seven segments are arranged as arectangleof two vertical segments on each side with one horizontal segment on the top, middle, and bottom. Additionally, the seventh segment bisects the rectangle horizontally. There are alsofourteen-segment displaysandsixteen-segment displays(for fullalphanumeric); however, these have mostly been replaced bydot matrixdisplays.The segments of a 7-segment display are referred to by the letters A to G, where the optional DPdecimal point(an "eighth segment") is used for the display of non-integer numbers. Hexadecimaldigits can be displayed on seven-segment displays. A combination of uppercase and lowercase letters is used for AF;this is done to obtain a unique, unambiguous shape for each hexadecimal digit (otherwise, a capital D would look identical to an 0 and a capital B would look identical to an 8). Also the digit 6 must be displayed with the top bar lit to avoid ambiguity with the letter b. In addition, seven segment displays can be used to show various other letters of thelatin,CyrillicandGreek alphabetsincludingpunctuation, but few representations are unambiguous and intuitive at the same time.Short messages giving status information (e.g. "no disc" on a CD player) are also commonly represented on 7-segment displays.

3.2.6 Piezo Buzzer

Piezo buzzeris an electronic device commonly used to produce sound. Light weight, simple construction and low price make it usable in various applications like car/truck reversing indicator, computers, call bells etc. Piezo buzzer is based on the inverse principle of piezo electricity discovered in 1880 by Jacques and Pierre Curie.It is the phenomena of generating electricity when mechanical pressure is applied to certain materials and the vice versa is also true. Such materials are called piezo electric materials. Piezo electric materials are either naturally available or manmade. Piezo ceramic is class of manmade material, which poses piezo electric effect and is widely used to make disc, the heart of piezo buzzer. When subjected to an alternating electric field they stretch or compress, in accordance with the frequency of the signal thereby producing sound.Thepiezo buzzerproduces sound based on reverse of the piezoelectric effect. The generation of pressure variation or strain by the application of electric potential across a piezoelectric material is the underlying principle.These buzzers can be used alert a user of an event corresponding to a switching action, counter signal or sensor input. They are also used in alarm circuits.The buzzer produces a same noisy sound irrespective of the voltage variation applied to it. It consists of piezo crystals between two conductors. When a potential is applied across these crystals, they push on one conductor and pull on the other. This, push and pull action, results in a sound wave. Most buzzers produce sound in the range of 2 to 4 kHz.The Red lead is connected to the Input and the Black lead is connected to Ground.

CHAPTER 4 SOFTWARE TOOLS

4.1 KEIL SOFTWAREKeil computer is a software used where the machine language code is written and compiled. After compilation, the machine source code is converted into hex code which is to be dumped into the micro controller for further processing. Keil compiler also supports c language code.4.2 STEPS TO WRITE AN ASSEMBLY LANGUAGE PROGRAM IN KEIL 1. Install the Keil Software in the PC in any of the drives.2. After installation, an icon will be created with the name Keil uVision3 . Just drag this icon onto the desktop so that it becomes easy whenever you try to write programs in keil.3. Double- click on this icon to start the Keil compiler.4. A page opens with different options in it showing the project workspace at the leftmost corner side, output window in the bottom and an ash coloured space for the program to be written.5. Now to start using Keil, click on the option project.6. A small window opens showing the options like new project, import project, open project etc. Click on New Project.7. A small window with the title bar Create new project opens. The window asks the user to give the project name with which it should be created and the destination location. The project can be created in any of the drives available. You can create a new folder and then a new file or can directly create a new file.8. After the file is saved in the given destination location, a window opens where a list of vendors will be displayed and you have to select the device for the target you have created.9. Now click on the option Output and give any name to the hex file to be created in the Name of executables text area and put a tick to the Create HEX file option present in the same window. The hex file can be created in any of the drives. You can change the folder by clicking on Select folder for Objects.10. Now to check whether the program you have written is errorless or not, click on the icon exactly below the Open file icon which is nothing but Build Target Icon. You can even use the shortcut key F7 to compile the program written.11. To check for the output, there are several windows like serial window, memory window, project window etc. Depending on the program you have written, select the appropriate window to see the output by entering into debug mode.12. The icon with the letter d indicated the debug mode.13. Click on this icon and now click on the option View and select the appropriate window to check for the output.14. After this is done, click the icon debug again to come out of the debug mode.15. The hex file created as shown earlier will be dumped into the micro controller with the help of another software called Proload.

CHAPTER 5CONCLUSION

Hence by this project we can design an effective detecting system that can monitor in quiz competitions in schools, colleges, TV programs etc; with eight different switches. The uniqueness of this project is only alerting the quiz conductor who first know the answer.

Advantages of the project Highly sensitiveLow cost and reliable circuitComplete elimination of manpower

ApplicationsWidely used in school, colleges and tv programs.

REFERENCES

Text book:8051 Microcontrollers by Muhammed Ali Mazidi Text book: Microcontrollers (theory and applications) by Ajay V Deshmukh http://www.rehab.research.va.gov http://www.datasheetcatalog.com http://www.technologystudent.com/elec1/transis1.htm http://en.wikipedia.org/wiki/Transistor http://www.engineersgarage.com/electronic-components/7805-voltage-regulator-ic https://en.wikipedia.org/wiki/Relay http://www.atmel.in/devices/AT89S51.aspx

APPENDIX

void buzzer( ) // function to monitor the input switches { flag= 0; while (1) { while (P1==0xFF); while(P1 == 0XFE) // check if switch 1 is pressed { flag=1; display (1); } while (P1 = = 0XFD) // check if switch 2 is pressed { flag=2; display (2); }

while (P1 = = 0XFB) // check if switch 3 is pressed { flag= 3; display (3); } while ( P1 = = 0xF7 ) // check if switch 4 is pressed { flag = 4; display (4); } while ( P1 = = 0xEF ) // check if switch 5 is pressed { flag = 5; display (5); } while (P1 = = 0xDF ) // check if switch 6 is pressed { flag = 6; display (6); }

while ( P1 = = 0xBF ) // check if switch 7 is pressed { flag = 7; display ( 7); } while ( P1 = =0x7F ) // check if switch 8 is pressed{ flag = 8; display (8);} p1 = 0xFF; stop_pin =1; output_on_pin =0;} } void main ( ){ output_on_pin =0; stop_pin =1; P1 = 0xFF; buzzer ( );}

VIEW OF PROJECT

EEE DEPARTMENT 16 KMEA ENGINEERING COLLEGE