38534531 micro controller based digital visitor counter

PAGE INDEX

Topic Page No.ACKNOWLEDMENT ABSTRACTINTRODUCTION

4 5 6

1. PROJECT DESCRIPTION1.1 BLOCK DIAGRAM

EXPLAINATION 8

2. CIRCUIT DIAGRAM AND DESCRIPTION2.1 CIRCUIT DIAGRAM 152.2 POWER SUPPLY 162.3 FLOW CHART 17

3.

4.

PROGRAM

COMPONENTS DETAILS4.1 4.24.34.44.54.6

RESISTOR CAPACITORTRANSISTORDIODESINTEGRATED CIRCUIT(IC555)INFRARED SENSORS

18

25 25 25 26 26 28

Microcontroller Based Digital Visitor Counter

5. CONCLUSION5.1 APPLICATIONS 29

BIBLIOGRAPHY 30

PROJECT PRINTOUTS 31 onwards

FIGURE INDEX

Figure Page No.

1.1 BLOCK DIAGRAM 71.21.3

PIN ConfigurationBlock Diagram

12 13

2.1 Circuit diagram of Digital Visitor Counter 152.2 Power Supply Diagram 16

4.14.2

Pin diagram of IC555Infrared Sensor

27 28

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TABLE INDEX

Table Page No.

1.1 Pin Description of AT89C2051 14

ACKNOWLEDGEMENT

We sincerely acknowledge with deep sense of gratitude to our project guide Prof.

Mrs. Ameya Pethe for the guidance and encourage she gave us for the preparation

of this project without her the project would have been difficult.

We are highly obliged to Mr. Shrikant Velankar,H.O.D(Elecronics) for his

noble spontaneous and timely help that carried out us throughout our endeavour

and finally made a grand success.

We also thank the staff of our electronics department for all the cooperation

and friendly treatment given to us during project.

We are also thankful to our colleagues and all those have extended the necessary help during the course of our work .

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ABSTRACT

Digital visitor counter is a reliable circuit that takes over the task of counting number of

Persons/ Visitors in the Room very accurately. When somebody enters into the Room then the Counter is

Incremented by one. The total number of Persons inside the Room is displayed on the seven segment

display module. The microcontroller does the above job it receives the signals from the sensors, and this

signals operated under the control of software which is stored in ROM.

This project we will create counter system for apply. The total number of object is displayed

on the seven segment display. The system is fully controlled by the 16 bit microcontroller 8051 which has

a 4Kbytes of ROM for the program memory.

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INTRODUCTION

The proposed system is based on 8051 microcontroller which is in our syllabus.For doing this

project we use some of the software like Eagle software is used for designing the PCB for this project.

(Since PCB making is a big process and involves lot of machineries which are expensive, we are going to

outsource this to the manufacturer.)

IC8051 is one of the popular Microcontroller. It has only 20 pins and there are 15 input/output

lines. The microcontroller has a program memory of 2 Kilobytes. The microcontroller continuously

monitor the sensor feed and if somebody enters sensors will provide information to the data processing

unit.This counter Sensor consist of 3 Section as follows:

Detect Object (Sensor), Data Processing (CPU) and final section Display by LCD module:

Detect Object (Sensor): Proximity sensor(infrared sensors)

Data Processing (CPU): For this project we choose microcontroller 8051

Display: For final section Display by seven segment display

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Digital visitor counter is a reliable circuit that takes over the task of counting.Number of

Persons/ Visitors in the Room very accurately. When somebody enters into the Room then the Counter is

Incremented by one. The total number of Persons inside the Room is displayed on the seven segment

display. The microcontroller does the above job it receives the signals from the sensors, and this signals

operated under the control of software which is stored in ROM. You can reset the counter using switch.

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1. PROJECT DESCRIPTION

Figure 1.1: BLOCK DIAGRAM

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1.1 BLOCK DIAGRAM EXPLANATION

INTEL’S 8051 Architecture

The generic 8051 architecture sports a Harvard architecture, which contains two separate buses

for both program and data. So, it has two distinctive memory spaces of 64K X 8 size for both program

and data.

It is based on an 8 bit central processing unit with an 8 bit Accumulator and another 8 bit B

register as main processing blocks. Other portions of the architecture include few 8 bit and 16 bit registers

and 8 bit memory locations. Each 8051 device has some amount of data RAM built in the device for

internal processing. This area is used for stack operations and temporary storage of data. This base

architecture is supported with on chip peripheral functions like I/O ports, timers/counters, versatile serial

communication port. So it is clear that this 8051 architecture was designed to cater many real time

The following list gives the features of the 8051 architecture:

Optimized 8 bit CPU for control applications.

Extensive Boolean processing capabilities.

64K Program Memory address space.

64K Data Memory address space.

128 bytes of on chip Data Memory.

32 Bi directional and individually addressable I/O lines.

Two 16 bit timer/counters.

Full Duplex UART.

6 source / 5 vector interrupt structure with priority levels.

On chip clock oscillator.

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Now you may be wondering about the nonmentioning of memory space meant for the program

storage, the most important part of any embedded controller. Originally this 8051 architecture was

introduced with on chip, `one time programmable' version of Program Memory of size 4K X 8. Intel

delivered all these microcontrollers (8051) with user's program fused inside the device. The memory

portion was mapped at the lower end of the Program Memory area. But, after getting devices, customers

couldn't change anything in their program code, which was already made available inside during device

fabrication.

Central Processing Unit

The CPU is the brain of the microcontrollers reading user's programs and executing the expected

task as per instructions stored there in.

Its primary elements are an 8 bit Arithmetic Logic Unit (ALU), Accumulator (Acc), few more 8

bit registers, B register, Stack Pointer (SP), Program Status Word (PSW) and 16 bit registers, Program

Counter (PC) and Data Pointer Register (DPTR). The ALU (Acc) performs arithmetic and logic functions

on 8 bit input variables. Arithmetic operations include basic addition, subtraction, multiplication and

division. Logical operations are AND, OR, Exclusive OR as well as rotate, clear, complement and etc.

Apart from all the above, ALU is responsible in conditional branching decisions, and provides a

temporary place in data transfer operations within the device. B register is mainly used in multiply and

divide operations. During execution, B register either keeps one of the two inputs or retains a portion of

the result. For other instructions, it can be used as another general purpose register.

Timers/Counters

8051 has two 16 bit Timers/Counters capable of working in different modes. Each consists of a

`High' byte and a `Low' byte which can be accessed under software.

There is a mode control register and a control register to configure these timers/counters in

number of ways. These timers can be used to measure time intervals, determine pulse widths or initiate

events with one microsecond resolution upto a maximum of 65 millisecond (corresponding to 65, 536

counts). Use software to get longer delays. Working as counter, they can accumulate occurrences of

external events (from DC to 500KHz) with 16 bit precision.

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In our project we are using 16 bit microcontroller 8051, it is the advanced 16 bit microcontroller from

ATMEL, which incorporates Flash Rom, and Timer etc.

Features of 8051 microcontroller are:

RAM – 128 Bytes (Data memory)

ROM – 4Kbytes (ROM signify the on – chip program space)

Serial Port – Using UART makes it simpler to interface for serial communication

Two 16 bit Timer/ Counter

Input/output Pins – 4 Ports of 8 bits each on a single chip.

6 Interrupt Sources

8 – bit ALU (Arithmetic Logic Unit)

Harvard Memory Architecture – It has 16 bit Address bus (each of RAM and ROM) and 8

bit Data bus

8051 can execute 1 million one-cycle instructions per second with a clock frequency of

12MHz.

This microcontroller is also called as “System on a chip” because it has all the features on a

single chip.

Description

The AT89C2051 is a low-voltage, high-performance CMOS 8-bit microcomputer with 2

Kbytes of Flash Programmable and erasable read only memory (PEROM).

The device is manufactured using Atmel’s high density nonvolatile memory technology

and is compatible with theindustry Standard MCS-51Ô instruction set and pinout. By

combining a versatile 8-bit CPU with Flash on a monolithic chip, the Atmel AT89C2051 is a

powerful microcomputer which provides a highly flexible and cost effective solution

to many embedded control application

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Figure1.2: PIN CONFIGURATION

PIN DESCRIPTION OF 8051:

The diagram above shows the 8051 pinout. The chip is a 40-pin package.

Port 0 :

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Pins 32 to 39 make up the 8-bit I/O port 0. However, if external memory is used, these lines are

used as a multiplexed address and data bus.

Port 1 : Pins 1 to 8 make up the 8-bit I/O port 1. Port 2 : Pins 21 to 28 make up the 8-bit I/O port 2. However, if external memory is used, these lines make up the high-byte of the external address (A8 to A15). Port 3 : Pins 10 to 17 make up the 8-bit I/O port 3. However, each of these eight pins also has an alternate function, as detailed in the table below.

Pin Name Bit Address Function

P3.0 RXD B0H Receive data for serial port

P3.1 TXD B1H Transmit data for serial port

P3.2 INT0-bar B2H External interrupt 0

P3.3 INT1-bar B3H External interrupt 1

P3.4 T0 B4H Timer/counter 0 external input

P3.5 T1 B5H Timer/counter 1 external input

P3.6 WR-bar B6H External data memory write strobe

P3.7 RD-bar B7H External data memory read strobe

RST: The reset input is on pin 9. This pin is used for resetting the 8051 (ie; loading the PC with the correct startup value).EA-bar : The external access, on pin 31, is used for enabling or disabling the on-chip ROM. When tied high (5V), the 8051 executes instructions in internal ROM when executing in the lower 4K (8K for the 8052) of memory. If tied low the 8051 will always execute instructions in external memory. The 8031 and 8032 should always have pin 31 tied low as there is no internal code memoryALE : The address latch enable is on pin 30. The ALE is used for latching the low byte of the address into an external register. We will deal with this at a later date. PSEN: The program store enable is an output signal on pin 29. This signal is used for fetching instructions from external code memory.

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BLOCK DIAGRAM OF 8051:

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Figure: BLOCK DIAGRAM OF 8051

Applications of 8051 microcontroller:

The 8051 has been in use in a wide number of devices, mainly because it is easy to integrate

into a project or build a device around. The following are the main areas of focus:

Energy Management:

Efficient metering systems help in controlling energy usage in homes and industrial

applications. These metering systems are made capable by incorporating microcontrollers

Touch screens:

A high number of microcontroller providers incorporate touch-sensing capabilities in their

designs. Portable electronics such as cell phones, media players and gaming devices are examples of

microcontroller-based touch screens.

Automobiles:

The 8051 finds wide acceptance in providing automobile solutions. They are widely used in

hybrid vehicles to manage engine variants. Additionally, functions such as cruise control and anti-brake

system have been made more efficient with the use of microcontrollers.

Medical Devices:

Portable medical devices such as blood pressure and glucose monitors use microcontrollers

will to display data, thus providing higher reliability in providing medical results.

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CIRCUIT DIAGRAM OF 8051:

Figure 2.1: Circuit diagram of Digital visitor counter

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2.2 Power Supply

Figure 2.2. Power Supply Diagram

AC230V

D1

D2

1000uF/25V

C1D4

D(1-4)=1N4007

D3

230/ 9V AC+5V1

2

3LM7805

IC1

Gnd

47uF/25V

C2

+12V

The microcontroller and other devices get power supply from AC to Dc

adapter through 7805, 5 volts regulator.

The adapter output voltage will be 12V DC unregulated. The 7805/7812 voltage regulators are

used to convert 12 V to 5V/12V DC. Vital role of power supply. The adapter output voltage will be 12V

DC unregulated. The 7805/7812 voltage regulators are used to convert 12 V to 5V/12V DC.

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2.3. Flowchart

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3.PROGRAM

$MOD52

DIS_A EQU P1.5DIS_B EQU P1.4DIS_C EQU P1.3DIS_D EQU P1.1DIS_E EQU P1.2DIS_F EQU P1.6DIS_G EQU P1.7DIS1 EQU P3.3DIS2 EQU P3.4 DIS3 EQU P3.5LDR1 EQU P3.0LDR2 EQU P3.1BUZZER EQU P1.0

DSEG ; This is internal data memory

ORG 20H ; Bit adressable memory BITS: DS 1

UP BIT BITS.0 DWN BIT BITS.1COUNT: DS 1SPEED: DS 1VALUE_1: DS 1VALUE_2: DS 1VALUE_3: DS 1COUNTER: DS 1STACK: DS

1 ; Stack begins here CSEG ; Code begins here

;---------==========----------==========---------=========---------; PROCESSOR INTERRUPT AND RESET VECTORS;---------==========----------==========---------=========---------

ORG 00H ; Reset JMP MAIN

ORG 000BH ;Timer Interrupt0

JMP REFRESH

;&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&; MAIN PROGRAM;&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&MAIN:

CLR BUZZERMOV SPEED,#00HMOV COUNT,#00HMOV VALUE_1,#00HMOV VALUE_2,#00HMOV VALUE_3,#00HMOV COUNTER,#00H

CLR DIS1CLR DIS2CLR DIS3

MOV TMOD,#01H;enable timer0 for scanningMOV TL0,#00HMOV TH0,#0FDH SETB ET0SETB EASETB TR0

AJMP ZAZA

ASSA: AJMP ASAA

ZAZA:SETB LDR1

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JNB LDR1,ASSA

CALL DELAYSETB LDR2JNB LDR2,$

;&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&; UP COUNTER;&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&

SETB BUZZERINC COUNTERMOV R5,COUNTER

DOIT: MOV A,#10CLR CSUBB A,R5JC ZX1JZ AQ1 INC VALUE_1AJMP CVC

AQ1: MOV VALUE_2,#01HMOV VALUE_1,#00HAJMP CVC

ZX1: MOV A,#20CLR CSUBB A,R5JC ZX2JZ AQ2INC VALUE_1AJMP CVC












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AQ10: MOV VALUE_3,#01HMOV VALUE_2,#00HMOV VALUE_1,#00HAJMP CVC

ZX10: MOV A,COUNTERCLR CSUBB A,#100JZ AQQ1JC ZXX1MOV R5,AAJMP DOIT

AQQ1:MOV VALUE_3,#02HMOV VALUE_2,#00HMOV VALUE_1,#00HAJMP CVC

ZXX1: MOV VALUE_1,#00HMOV VALUE_2,#00HMOV VALUE_3,#00H

CVC:;&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&

CALL DELAYCLR BUZZERJB LDR2,$AJMP ZAZA

ZAZAA: JMP ZAZAASAA: SETB LDR2

JNB LDR2,ZAZAA

CALL DELAYSETB LDR1JNB LDR1,$

;&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&; DOWN COUNTER;&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&

SETB BUZZERDEC COUNTERMOV R5,COUNTERMOV A,R5INC ACJNE A,#00H,DOIT1MOV VALUE_1,#00HMOV VALUE_2,#00HMOV VALUE_3,#00HMOV COUNTER,#00HAJMP CVCV

DOIT1:MOV A,#10CLR CSUBB A,R5JC AZX1JZ AAQ1 MOV R6,VALUE_1CJNE R6,#00H,GHGMOV VALUE_2,#00HMOV VALUE_1,#09HAJMP CVCV

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GHG:DEC VALUE_1AJMP CVCV

AAQ1:MOV VALUE_2,#01HMOV VALUE_1,#00HAJMP CVCV

AZX1: MOV A,#20CLR CSUBB A,R5JC AZX2JZ AAQ2MOV R6,VALUE_1CJNE R6,#00H,GHG1MOV VALUE_2,#01HMOV VALUE_1,#09HAJMP CVCV

GHG1:DEC VALUE_1AJMP CVCV





AZX3: MOV A,#40CLR CSUBB A,R5JC AZX4JZ AAQ4

MOV R6,VALUE_1CJNE R6,#00H,GHG3MOV VALUE_2,#03HMOV VALUE_1,#09HAJMP CVCV









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AZX9: MOV A,#100CLR CSUBB A,R5JC AZX10JZ AAQ10MOV R6,VALUE_1CJNE R6,#00H,GHG9MOV VALUE_3,#00HMOV VALUE_2,#09HMOV VALUE_1,#09HAJMP CVCV


AAQ10: MOV VALUE_3,#01HMOV VALUE_2,#00HMOV VALUE_1,#00HAJMP CVCV

AZX10: MOV A,COUNTERCLR CSUBB A,#100JZ AAQQ1JC AZXX1MOV R5,AMOV A,COUNTERCJNE A,#199,JKJKMOV VALUE_3,#01H

JKJK:AJMP DOIT1

AAQQ1: MOV VALUE_3,#02HMOV VALUE_2,#00HMOV VALUE_1,#00HAJMP CVCV

AZXX1: MOV VALUE_1,#00HMOV VALUE_2,#00HMOV VALUE_3,#00H

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CVCV:

;&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&

CALL DELAYCLR BUZZERJB LDR1,$AJMP ZAZA

;&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&; 7 SEGMENT DISPLAY;&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&DISP:

MOV R2,SPEEDCJNE R2,#00H,AAS1CLR DIS_ACLR DIS_BCLR DIS_CCLR DIS_DCLR DIS_ECLR DIS_FSETB DIS_GRET

AAS1: CJNE R2,#01H,AS2CLR DIS_BCLR DIS_CSETB DIS_ASETB DIS_DSETB DIS_ESETB DIS_FSETB DIS_GRET

AS2: CJNE R2,#02H,AS3CLR DIS_ACLR DIS_BCLR DIS_DCLR DIS_ECLR DIS_GSETB DIS_CSETB DIS_F

RETAS3: CJNE R2,#03H,AS4

CLR DIS_A CLR DIS_BCLR DIS_CCLR DIS_DCLR DIS_GSETB DIS_ESETB DIS_FRET

AS4: CJNE R2,#04H,AS5CLR DIS_BCLR DIS_CCLR DIS_FCLR DIS_GSETB DIS_ASETB DIS_DSETB DIS_ERET

AS5: CJNE R2,#05H,AS6CLR DIS_ACLR DIS_CCLR DIS_DCLR DIS_FCLR DIS_GSETB DIS_BSETB DIS_ERET

AS6: CJNE R2,#06H,AS7CLR DIS_ACLR DIS_CCLR DIS_DCLR DIS_ECLR DIS_FCLR DIS_GSETB DIS_BRET

AS7: CJNE R2,#07H,AS8CLR DIS_ACLR DIS_BCLR DIS_CSETB DIS_DSETB DIS_ESETB DIS_FSETB DIS_G

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RETAS8: CJNE R2,#08H,AS9

CLR DIS_ACLR DIS_BCLR DIS_CCLR DIS_DCLR DIS_ECLR DIS_FCLR DIS_GRET

AS9: CJNE R2,#09H,AS10CLR DIS_ACLR DIS_BCLR DIS_CCLR DIS_DCLR DIS_FCLR DIS_GSETB DIS_ERET

AS10: MOV SPEED,#00HAJMP DISP

;&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&REFRESH:

INC COUNTMOV R4,COUNT

QA1: CJNE R4,#01H,QA2MOV SPEED,VALUE_1SETB DIS1CLR DIS2CLR DIS3CALL DISP AJMP DOWN

QA2: CJNE R4,#02H,QA3MOV SPEED,VALUE_2CLR DIS1SETB DIS2CLR DIS3CALL DISP AJMP DOWN

QA3: CJNE R4,#03H,QA4MOV SPEED,VALUE_3CLR DIS1CLR DIS2

SETB DIS3CALL DISP AJMP DOWN

QA4: MOV COUNT,#01HMOV R4,COUNTAJMP QA1

DOWN: MOV TL0,#0FFH;reload the timer for scanningMOV TH0,#0F2HRETI

;&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&

DELAY:MOV R1,#0FFH

RE1: MOV R2,#5FHRE: NOP

DJNZ R2,REDJNZ R1,RE1RET

END

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COMPONENTS DETAILS

4.1. Resistor

Resistor is a component that resists the flow of direct or alternating electric circuit. Resistors used

in electric circuits are cylindrical. They are often color coded by three or four color bands that indicate the

specific value of resistance. Resistors obey ohm’s law, which states that the current density is directly

proportional to the electric field when the temperature is constant

4.2. Capacitor

Capacitor or electric condenser is a device for storing an electric charge. When one plate is

charged with electricity from a direct current or electrostatic source, the other plate have induced in it a

charge of the opposite sign; that is, positive if the original charge is negative and negative if the original

charge is positive. Capacitors are produced in a wide variety of forms. Air, Mica, Ceramics, Paper, Oil,

and Vacuums are used as dielectrics depending on the purpose for which the device is intended.

4.3. Transistor

Transistor is a device which transforms current flow from low resistance path to high resistance

path. It is capable of performing many functions of the vacuum tube in electronic circuits, the transistor is

the solid state device consisting of a tiny piece of semi conducting material, usually germanium or silicon,

to which three or more electrical connections are made.

4.4 Diode

Diode is a electronic device that allows the passage of current in only one direction. The diodes

commonly used in electronic circuits are semiconductor diodes. There are different diodes used in

electronic circuits such as Junction diode, Zener diode, Photo diodes, and tunnel diode. Junction diodes

consist of junction of two different kinds of semiconductor material. The Zener diode is a special junction

type diode, using silicon, in which the voltage across the junction is independent of the current through

the junction.

4.5. Integrated Circuits

Timer IC (555)

It is a highly stable device for generating accurate time delays or oscillation. Additional terminals

are provided for triggering or resetting if desired. In the time delay mode of operation, the time is

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precisely controlled by one external resistor and capacitor. For astable operation as an oscillator, the free

running frequency and duty cycle are accurately controlled with two external resistors and one capacitor.

The circuit may be triggered and reset on falling waveforms, and the output circuit can source or sink up

to 200mA or drive TTL circuits.

Features:

Direct replacement for SE555/NE555

Timing from microseconds through hours

Operates in both astable and monostable modes

Adjustable duty cycle

Output can source or sink 200 mA

Output and supply TTL compatible

Temperature stability better than 0.005% per °C

Normally on and normally off output

Applications:

Precision timing

Pulse generation

Sequential timing

Time delay generation

Pulse width modulation

Pulse position modulation

Linear ramp generator

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Fig 4.1: PIN DIAGRAM OF TIMER 555 IC:

Fig: PIN DIAGRAM OF TIMER 555 IC

MONOSTABLE MULTIVIBRATOR:

Monostable multivibrator often called a one shot multivibrator is a pulse generating circuit

in which the duration of this pulse is determined by the RC network connected externally to the 555 timer.

In a stable or standby state, the output of the circuit is approximately zero or a logic-low level. When

external trigger pulse is applied output is forced to go high ( VCC). The time for which output remains

high is determined by the external RC network connected to the timer. At the end of the timing interval,

the output automatically reverts back to its logic-low stable state. The output stays low until trigger pulse

is again applied. Then the cycle repeats. The monostable circuit has only one stable state (output low)

hence the name monostable.

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PIN DIAGRAM OF MONOSTABLE:

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Pin1: Ground. All voltages are measured with respect to this terminal.

Pin2: Trigger. The output of the timer depends on the amplitude of the external trigger pulse applied to this pin. The output is low if the voltage at this pin is greater than 2/3 VCC. When a negative going pulse of amplitude greater than 1/3 VCC is applied to this pin, comparator 2 output goes low, which inturn switches the output of the timer high. The output remains high as long as the trigger terminal is held at a low voltage.

Pin3: Output. There are two ways by which a load can be connected to the output terminal: either between pin 3 and ground or between pin3 and supply voltage +VCC. When the output is low the load current flows through the load connected between pin3 and +VCC into the output terminal and is called sink current. The current through the grounded load is zero when the output is low. For this reason the load connected between pin 3 and +VCC is called the normally on load and that connected between pin 3 and ground is called normally off-load. On the other hand, when the output is high the current through the load connected between pin 3 and +VCC is zero. The output terminal supplies current to the normally off load. This current is called source current. The maximum value of sink or source current is 200mA.

Pin4: Reset. The 555 timer can be reset (disabled) by applying a negative pulse to this pin. When the reset function is not in use, the reset terminal should be connected to +VCC to avoid any possibility of false triggering.

Pin5: Control Voltage. An external voltage applied to this terminal changes the threshold as well as trigger voltage. Thus by imposing a voltage on this pin or by connecting a pot between this pin and ground, the pulse width of the output waveform can be varied. When not used, the control pin should be bypassed to ground with a 0.01µF Capacitor to prevent any noise problems.

Pin6: Threshold. This is the non-inverting input of comparator 1, which monitors the voltage across the external capacitor. When the voltage at this pin is greater than or equal to the threshold voltage 2/3 VCC, the output of comparator 1 goes high, which inturn switches the output of the timer low.

Pin7: Discharge. This pin is connected internally to the collector of transistor Q1. When the output is high Q1 is OFF and acts as an open circuit to external capacitor C connected across it. On the other hand, when the output is low, Q1 is saturated and acts as a short circuit, shorting out the external capacitor C to ground.

Pin8: +VCC. The supply voltage of +5V to + 18V is applied to this pin with respect to ground.

ASTABLE MULTIVIBRATOR:

Astable Multivibrator is a two stage switching circuit in which the output of the first stage is

fed to the input of the second stage and vice versa. The outputs of both the stages are complementary.

This free running multivibrator generates square wave without any external triggering pulse. The circuit

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has two stable states and switches back and forth from one state to another, remaining in each state for a

time depending upon the discharging of the capacitive circuit.

The multivibrator is one form of relaxation oscillator, the frequency of which may be controlled by external synchronizing pulses.

4.5. Infrared sensors

The TSOP17 series are miniaturized receivers for infrared remote control systems. PIN

diode and preamplifier are assembled on lead frame, the epoxy package is designed as IR filter. The

demodulated output signal can directly be decoded by a microprocessor. TSOP17.. is the standard IR

remote control receiver series, supporting all major transmission codes.

Features:

Photo detector and preamplifier in one package

Internal filter for PCM frequency

Improved shielding against electrical field disturbance

TTL and CMOS compatibility

Output active low

Low power consumption

High immunity against ambient light

Continuous data transmission possible (up to 2400 bps)

Suitable burst length 10 cycles/burst

4.6 crystal oscillator:

A crystal oscillator is an electronic oscillator circuit that uses the mechanical resonance of a

vibrating crystal of piezoelectric material to create an electrical signal with a very precise frequency. This

frequency is commonly used to keep track of time (as in quartz wristwatches), to provide a stable clock

signal for digital integrated circuits, and to stabilize frequencies for radio transmitters and receivers. The

most common type of piezoelectric resonator used is the quartz crystal, so oscillator circuits designed

around them became known as "crystal oscillators."

Quartz crystals are manufactured for frequencies from a few tens of kilohertz to tens of megahertz.

More than two billion (2×109) crystals are manufactured annually. Most are small devices for consumer

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http://en.wikipedia.org/wiki/Electronic_oscillator


devices such as wristwatches, clocks, radios, computers, and cell phones. Quartz crystals are also found

inside test and measurement equipment, such as counters, signal generators, and oscilloscopes.

4.7 SEVEN SEGMENT DISPLAY

One common requirement for many different digital devices is a visual numeric display.

Individual LEDs can of course display the binary states of a set of latches or flip-flops.

However, we're far more used to thinking and dealing with decimal numbers. To this end, we

want a display of some kind that can clearly represent decimal numbers without any

requirement of translating binary to decimal or any other format.

One possibility is a matrix of 28 LEDs in a 7×4 array. We can then light up selected LEDs in

the pattern required for whatever character we want. Indeed, an expanded version of this is

used in many ways, for fancy displays. However, if all we want to display is numbers, this

becomes a bit expensive. A much better way is to arrange the minimum possible number of

LEDs in such a way as to represent only numbers in a simple fashion.

This requires just seven LEDs (plus an eighth one for the decimal point, if that is needed). A

common technique is to use a shaped piece of translucent plastic to operate as a specialized

optical fiber, to distribute the light from the LED evenly over a fixed bar shape. The seven bars

are laid out as a squared-off figure "8". The result is known as a seven-segment LED.

We've all seen seven-segment displays in a wide range of applications. Clocks, watches, digital

instruments, and many household appliances already have such displays. In this experiment,

we'll look at what they are and how they can display any of the ten decimal digits 0-9 on

demand.

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CONCLUSION

5.1 Application

Visitor counter. The counter sensor majority apply in industry or factory. Vehicle parking (Counting commodity or counting a car in/out of parking)

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BIBLIOGRAPHY

[1] D. Neamen, Electronic Circuit Analysis and Design. New Mexico: Times

Mirror Higher Education Group Inc., 1996, pp. 69.

[2]Microchip, AT89C2051 Data Sheet, Microchip Technology Inc., 2003

[3] Help for The 555 Timer Chip,

http://www2.ebtech.net/~pais/555_Timer_Help.html.

[4]“ FREE Microcontroller projects”,

http://www.8051projects.info/proj.asp?ID=36

[5]eHow.com,“How to Write a Bibliography”,

http://www.ehow.com/how_2859_write-bibliography.html

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38534531 micro controller based digital visitor counter

Documents

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