door locking system with 1 master password & 3 user passwords

7/31/2019 Door Locking System With 1 Master Password & 3 User Passwords

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Door Security System (3 user & 1 master password)

INTRODUCTION

The main and very basic need of security was fulfilled by using themechanical or electrical locks which are very heavy and designed for

only one key. Therefore a large number of locks of required for locking a

large industries there are many keys for different locks (i.e. a very

tedious task to arrange these keys). These locks are not so much

protective and could be broken by using some mechanical tools. All

these problems could be solved if we use electronic locking system in

place of these electrical & mechanical locks. There are also some more

features are available in these electronic locking system The electronicsecurity system are very light, flexible, reprogrammable, lower cost,

more accurate, highly secure and required less power. In this way due to

the introduction of the electronic security system the security need and

fulfilled to a great extent and we could protect a whole industry or

company very easily and rapidly. The main objective of this project is to

make an electronic device by which we could give access to the

authenticated persons in the sophisticated area of an organization or a

company with a very simple operability. We could also generate

codeword for different expensive equipment so that they could be made

protective and only the person who has the complete knowledge to

operate that machine or equipment is authenticated to operate. One

more advantage to use this security system is that we could easily

change the codeword according to the situation or security conditions

and easily get the information about the attempts of hacking or hackers.

This device is fully automated so that we dont need to monitor the

process. Basically the device would generate five passwords in which

there would be one master code and other four will be sub code wecould distribute these code to different persons who are permitted to get

access. These persons would be able to get access by using their code

and if a person leaks his code then he could easily be detected and his

code could be change with the help of master code. In this way this

device is a much protected electronic device in which the number of

codes can be increased according to the need which would be

reprogrammable. Here we can also lock different expensive machines or

equipment by giving the sub codes so that only those persons having

Northern India Engineering college


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the knowledge of the operability of the equipment had given these codes

so that any other person cant damage the machine.

BRIEF DESCRIPTION OF ASSOCIATED TECHNOLOGY:-

This project is basically a microcontroller based device which operates

according to the data saved into the EEPROM and run the program in

microcontroller. The hardware used in this project is as follows: MCU

89S8253, EEPROM, Relay driver, LEDs, LCD Module, Power supply,

Buzzer and Speaker etc. The main or central processing unit of this

project is 89C51 it consists of the following features i.e. This is basically

a 40 pin to 44 pin MCU depending upon its packaging it is available in

three types of packages PDIP(Plastic dual in line Package-40pin),

TQFP/PQFP(Thin Plastic Gull Wing Quad Flatpack-44pin) and

PLCC(Plastic J-Leaded Chip Carrier-44pin). It has a 4K Bytes of In-

System Reprogrammable Flash Memory which has a capacity of 1,000

Write/Erase Cycles. Fully Static operation from 0Hz to 24MHz and it has

also three-level Program Memory Lock. The internal RAM of this MCU is

128*8 bit and externally it could operate 64MB memory devices. It

consists of a two quartz crystal timer or oscillator of 16 Bit and 6 interrupt

sources therefore the programming of microcontroller is done withserially inserting the data. This microcontroller is cheap and also cost-

effective because it could be operated into two low power consuming

modes i.e. Low Power Idle & Power Down Modes. In case of Idle Mode

the CPU puts itself to sleep while all the on-chip peripherals remain

active. While in Power down Mode the oscillator is stopped, and the

instruction that invokes power down is the last executed instruction. This

MCU is given the industry standard MCS-51TM instruction set and

pinout. The device is manufactured using Atmels high densitynonvolatile memory technology and uses high performance CMOS

transistors. Some other requirements of this microcontroller are:

Operating temperature range -55 C to + 125C and storage

temperature range -65 C to + 150C, Voltage at any pin with respect to

ground -1.0V to +7.0V and the maximum operating voltage 6.6V. The

DC output current of 15.0mA. The external clock driver used to drive this

MCU should have oscillation frequency of 0-24MHz, clock period of

41.5ns, High Time and Low time 15ns each and Rise & Fall Time 20ns



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each. The operating voltage of this microcontroller is given through a DC

power supply of 12V.

PATH OF IMPLIMENTATION:-

Block Diagram:

Brief Description: The system comprises a small electronic unit with a

numeric keypad, which is fixed outside the entry door to control a

solenoid-operated lock. When an authorized person enterspredetermined number (password) via the keypad, the relay operated for

a limited time to unlatch the solenoid-operated lock so the door can be

pushed/pulled open. At the end of preset delay, the relay reenergizes

and the door gets locked again. If the entered password is correct the

unit opens the door. When the code has been incorrectly entered four

times in a row, the code lock will switch to alarm mode and operate an

alarm relay. Alarm relay are turned off after entering a valid User Access

Code. This function thwarts any attempt by hackers to quickly try a



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large number of codes in a sequence. The secret code can be changed

any time after entering the current code (Master code).

There will be three unique passwords for three users. This enables thatany person of the family can open the door with his own password even

if other is not available. There is a facility that each user can change

his/her password when required. After all this there is master password

available with designer which in case can be used to open when user

forget their password. The person knowing the master password can tell

the user password at present by opening the system.

WORKING

Access control is a system which enables an authority to control

access to areas and resources in a given physical facility or computer-



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based information system. An access control system, within the field

of physical security, is generally seen as the second layer in the security

of a physical structure.

Access control is, in reality, an everyday phenomenon. A lock on

a car door is essentially a form of access control. A PIN system at a

bank is another means of access control. Bouncers standing in front of

a night club are perhaps a more primitive mode of access control (given

the evident lack of information technology involved). The possession of

access control is of prime importance when persons seek to secure

important, confidential, or sensitive information and equipment.

Item control or electronic key management is an area within(and possibly integrated with) an access control system which concerns

the managing of possession and location of small assets or physical.

DESCRIPTION:-



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BlockDiagram:

Working in brief:- There is a switch matrix interfaced with the

controller .When a particular sequence is pressed then micro controller

decodes it allows the door to be opened through the relay driver and

relay. If the sequence is pressed wrong then buzzer will blow.

Key Components:- The major components of this project are:

Switch matrix

Microcontroller

Relay driver

Relay

Buzzer

The microcontroller used here is a common 8 bit Atmel microcontroller

AT89s8253.It is a low-power, high-performance CMOS 8-bitmicrocontroller with12K bytes of In-System Programmable (ISP) Flash

program memory

and 2K bytes of

EEPROM data

memory. It has 32

programmable input

output lines


SWITCH

MATRIX AS

KEYPAD

MICRO-

CONTROLLERRELAY DRIVER

RELAYBUZZER


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Programmable (ISP) Flash program memory and 2K bytes of EEPROM

data memory have been provided. It has 32 programmable input output

lines.

Features:-

12K Bytes of In-System Programmable (ISP) Flash Program Memory

SPI Serial Interface for Program Downloading Endurance: 10,000 Write/Erase Cycles

2K Bytes EEPROM Data Memory

Endurance: 100,000 Write/Erase Cycles

2.7V to 5.5V Operating Range

Fully Static Operation: 0 Hz to 24 MHz (in x1 and x2 Modes)

Three-level Program Memory Lock

256 x 8-bit Internal RAM

32 Programmable I/O Lines

Three 16-bit Timer/Counters

Nine Interrupt Sources



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Enhanced UART Serial Port with Framing Error Detection and

Automatic Address Recognition

Enhanced SPI (Double Write/Read Buffered) Serial Interface

Programmable Watchdog Timer

Relay driver:-

ULN2803 is a current driver IC which drives the relay. The eight

NPN Darlington connected transistors in this family of arrays are ideally

suited for interfacing between low logic level digital circuitry (such as

TTL, CMOS or PMOS/NMOS) and the higher current/voltage

requirements of lamps, relays, printer hammers or other similar loads for

a broad range of computer, industrial, and consumer applications. All

devices feature opencollector outputs and freewheeling clamp diodes

for transient Suppression. The ULN2803 is designed to be compatible

with standard TTL families while the ULN2804 is optimized for 6 to 15

volt high level CMOS or PMOS.

Relay:-

A relay is an electrically operated switch. Many relays use an

electromagnet to operate a switching mechanism mechanically, butother operating principles are also used. Relays are used where it is



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necessary to control a circuit by a low-power signal (with complete

electrical isolation between control and controlled circuits), or where

several circuits must be controlled by one sign. Here, relay is used to

switch on the devices.

BUZZER SYSTEM:-

A system consisting signaling devices, a console, and a reset

button to notify in the form of sound happening of some incidence. THE

buzzer used here is piezo buzzer controlled by micro controller

signaling.

EMBEDDED SYSTEM

The embedded system is a combination of computer hardware,software, additional electrical & mechanical parts. A computer is used in



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such devices primarily as a means to simplify the system design and to

provide flexibility.

Often the user of the device is not even aware that a computer ispresent.

Electronic devices that incorporate a computer (usually a

microprocessor) is within their implementation.

These are Real-time system process events. These events occur on

external inputs and cause other events to occur as outputs. Minimizing

response time is usually a primary objective, or otherwise the entire

system may fail to operate properly. Therefore embedded systems

employ the use of a RTOS (Real-Time Operating System). Its an

operating system with the necessary features to support a Real-Time

System.

Real-Time System:-

It is a system where correctness depends not only on the correctness of

the logical result of the computation, but also on the result delivery time.

It responds in a timely, predictable way to unpredictable external stimuliarrivals. The real Time Systems can be further divided into two types:

Soft Real-Time System: Compute output response as fast as

possible, but no specific deadlines that must be met.

Hard Real-Time System: Output response must be computed by

specified deadline or system.



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APPLICATION OF EMBEDDED SYSTEMS:-

Consumer electronics

Telecommunication

Automobile



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Medical instrumentation

Industrial control equipment

Defense

Communication satellite

Data communication

Internet appliances

MICROCONTROLLER

A microcontroller is a computer-on-a-chip, or, if you prefer, a single-chip

computer. Micro suggests that the device is small, and controller tells

you that the device might be used to control objects, processes, or



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events. Another term to describe a microcontroller is embedded

controller, because the microcontroller and its support circuits are often

built into, or embedded in, the devices they control.

You can find microcontrollers in all kinds of things these days. Any

device that measures, stores, controls, calculates, or displays

information is a candidate for putting a microcontroller inside. The

largest single use for microcontrollers is in automobilesjust about

every car manufactured today includes at least one microcontroller for

engine control, and often more to control additional systems in the car.

In desktop computers, you can find microcontrollers inside keyboards,

modems, printers, and other peripherals. In test equipment,microcontrollers make it easy to add features such as the ability to store

measurements, to create and store user routines, and to display

messages and waveforms. Consumer products that use microcontrollers

include cameras, video recorders, compact-disk players, and ovens. And

these are just a few examples.

Microcontroller Basics:-

A microcontroller is similar to the microprocessor inside a personal

computer. Examples of microprocessors include Intels 8086, Motorolas

68000, and Zilogs Z80. Both microprocessors and microcontrollers

contain a central processing unit, or CPU. The CPU executes

instructions that perform the basic logic, math, and data-moving

functions of a computer. To make a complete microprocessor requires

memory for storing data and programs and input/output(I/O) interfaces

for connecting external devices like keyboards and displays. In contrast,

a microcontroller is a single-chip computer because it contains memoryand I/O interfaces in addition to the CPU. Because the amount of

memory and interfaces that can fit on a single chip is limited,

microcontrollers tend to be used in smaller systems that require little

more than the microcontroller and a few support components. Examples

of popular microcontrollers are Intels 8052 (including the 8052-BASIC,

which is the focus of this book), Motorolas 68HC11, and Zilogs Z8.

Microcontroller History:-



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To understand how microcontrollers fit into the always-expanding world

of computers, we need to look back to the roots of micro computing.

In its January 1975 issue, Popular Electronics magazine featured anarticle describing the Altair 8800 computer, which was the first

microcomputer that hobbyists could build and program themselves. The

basic Altair included no keyboard, video display, disk drives, or other

elements we now think of as essential elements of a personal computer.

Its 8080 microprocessor was programmed by flipping toggle switches on

the front panel. Standard RAM was 256 bytes and a kit version cost

$397 ($498 assembled). A breakthrough in the Altairs usability occurred

when a small company called Microsoft offered a version of the BASICprogramming language for it. Of course, the computer world has

changed a lot since the introduction of the Altair. Microsoft has become

an enormous software publisher, and a typical personal computer now

includes a keyboard, video display, disk drives, and Megabytes of RAM.

Whats more, theres no longer any need to build a personal computer

from scratch, since mass production has drastically lowered the price of

assembled systems. At most, building a personal computer now involves

only installing assembled boards and other major components in an

enclosure. A personal computer like Apples Macintosh or IBMs PC is a

general-purpose machine, since you can use it for many applications

word processing, spreadsheets, computer-aided design, and morejust

by loading the appropriate software from disk into memory. Interfaces to

personal computers are for the most part standard ones like those to

video displays, keyboards, and printers.

But along with cheap, powerful, and versatile personal computers has

developed a new interest in small, customized computers for specificuses. Each of these small computers is dedicated to one task, or a set of

closely related tasks. Adding computer power to a device can enable it

to do more, small display, a keypad or switches, sensors, relays, motors,

and so on. or do it faster, better, or more cheaply. For example,

automobile engine controllers have helped to reduce harmful exhaust

emissions. And microcontrollers inside computer modems have made it

easy to add features and abilities beyond the basic computer-to-phone-

line interface. In addition to their use in mass-produced products likethese, its also become feasible to design computer power into one-of-a-



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kind projects, such as an environmental controller for a scientific study or

an intelligent test fixture that ensures that a product meets its

specifications before its shipped to a customer. At the core of many of

these specialized computers is a microcontroller. The computersprogram is typically stored permanently in semiconductor memory such

as ROM or EPROM. The interfaces between the microcontroller and the

outside world vary with the application, and may include a

These small, special-purpose computers are sometimes called single-

board computers, or SBCs. The term can be misleading, however, since

the computer doesnt have to be on a single circuit board, and many

types of computer systems, such as laptop and notebook computers, arenow manufactured on a single board.

AT89S8253 microcontroller :-

The microcontroller development effort resulted in the 8051 architecture,

which was first introduced in 1980 and has gone on to be arguably the

most popular micro controller architecture available. The 8051 is a very

complete microcontroller with a large amount of built in control store

(ROM &EPROM) and RAM, enhanced I/O ports, and the ability to

access external memory. The maximum clock frequency with an 8051

micro controller can execute instructions is 20MHZ.Microcontroller is a

true computer on chip. The design incorporates all of the features found

in a microprocessor: CPU, ALU, PC, SP and registers. It also has the

other features needed to, make complete computer: ROM, RAM, parallel

I/O, serial I/O, counters and a clock circuit. The

89C51/89C52/89C54/89C58 contains a non-volatile FLASH program

memory that is parallel programmable. For devices that are serialprogrammable(In-System Programmable (ISP) and In-Application

Programmable (IAP) with a boot loader)All three families are Single-Chip

8-bit Microcontrollers manufactured in advanced CMOS process and are

Derivatives of the 80C51 microcontroller family. All the devices have the

same instruction set as the 80C51.

FEATURES:-



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8K Bytes of In-System Reprogrammable Flash Memory


Fully Static Operation: 0 Hz to 33 MHz





Eight Interrupt Sources

Programmable Serial Channel

DESCRIPTION:-

The AT89S8253 is a low power, high performance CMOS 8-bit micro

computer with 8K bytes 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 80c51 and 80C52 instruction set and pin out.

The on-chip flash allows the program memory to be reprogrammed

insystem or by a conventional nonvolatile memory programmer. Bycombining a versatile 8-bit CPU with flash on a monolithic chip, the



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Atmel AT89s8253 is a powerful microcomputer which provides a highly

flexible and cost effective solution to many embedded control

applications. The main advantages of 89s8253 over 8051 are:-

Software Compatibility

Program Compatibility

Rewritability



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89S8253 PROCESSOR ARCHITECTURE:-



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A rchitecture contains the following :-

8 bit CPU with registers A and B

16 bit program counter(PC) and data pointer(DPTR)

8 bit program status word(PSW)

8 bit stack pointer

Internal ROM of 0(8031) to 4K(8051)

Internal RAM of 128 Bytes

4 register banks 00-1f

16 bytes(bit addressable) 20-2f

80 bytes of general purpose data memory 30-7f

32 I/O pins arranged as four 8 bit ports (P0 P3)

2 16-bit timer/counters: T0 and T1

Full duplex serial data receiver/transmitter: SBUF

Control registers: TCON, TMOD, SCON, PCON, IPand IE

2 external and 3 internal interrupt sources

Oscillator and clock circuits



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Pin Diagram of the 40 Pin DIP package of the 89S8253:-

DESCRIPTION:-

VCC:-

Pin no.40 is used for the supply to the microcontroller..

GND:-

Ground.

RST:-



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This is pin no.9, used to reset the device by keeping it high for 2

machine cycles. The microcontroller should be reset at the time of

starting.

Oscillator:-

Pins XTAL1 and XTAL2 are used for connecting a quartz crystal for the

internal oscillator.

Crystal Frequency-10 MHz

External Access (EA):-

The 8051 family members, all come with on-chip ROM to store the

program. In such case, EA pin is connected to Vcc. To indicate that the

code is stored in external ROM, EA pin must be connected to ground.

PSEN:-

PSEN stands for Program Store Enable. This is an output pin and isconnected to OE pin of ROM

Port 0:-

Port 0 is an 8-bit open drain bi-directional I/O 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 can also be configured to be the

multiplexed lower order address/data bus during accesses to external

program and data memory. In this mode, P0 has internal pull-ups. Port 0also receives the code bytes during Flash programming and outputs the

code bytes during program verification. External pull ups are required

during program verification.

Port 1 and Port 2:-



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Port 1 is an 8-bit bi-directional I/O port with internal pull-ups. The Port1

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 willsource current (IIL) because of the internal pull-ups. In addition, P1.0

and P1.1 can be configured to be the timer/counter 2 external count

input (P1.0/T2) and the timer/counter 2.

Port 3:-

It has internal pull-ups and can sink/source 4 TTL inputs. Port 3

occupies a total of 8 pins, pins 10 through 17. It can be used as input or

output. Port 3 has additional function of providing some extremely signal

as interrupts.

ALE/PROG:-

Address Latch Enable is an output pulse for latching the low byte of the

address (on its falling edge) during accesses to external memory. This

pin is also the program pulse input (PROG) during Flash programming.

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

locking purposes. Note, however, that one ALE pulse is skipped during

each access to external data memory.



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PSEN:-

Program Store Enable. PSEN is the read strobe to external program

memory (active low). When the AT89S8253 is executing code fromexternal program memory, PSEN is activated twice each machine cycle,

except that two PSEN activations are skipped during each access to

external data memory.

EA/VPP:-

External 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 isprogrammed, 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 when 12-volt programming is selected.

PCB (PRINTED CIRCUIT BOARD)



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A printed circuit board, or PCB, is used to mechanically support and

electrically connect electronic components using conductive pathways,

tracks or traces etched from copper sheets laminated onto a non-

conductive substrate. It is also referred to as printed wiring board (PWB)or etched wiring board. A PCB populated with electronic components is

a printed circuit assembly (PCA), also known as a printed circuit board

assembly (PCBA).

PCBs are inexpensive, and can be highly reliable. They require much

more layout effort and higher initial cost than either wire-wrapped or

point-to-point constructed circuits, but are much cheaper and faster for

high-volume production. Much of the electronics industry's PCB design,assembly, and quality control needs are set by standards that are

published by the IPC organization.

POWER SUPPLY:-

There is 5V supply voltage required for this project. An ac 9-0-9 V mains

transformer is connected via a mains lead. The transistor is voltage

regulator IC. It regulates 4.8V dc (approx).

Working: - The working is quite clear. It is describe in following steps.

Step down transformer convert 220V AC into 4.8V AC

It convert AC voltage into pulsating DC voltage

The filter stage uses a shunt capacitor to filter out ripples from

pulsating DC

The regulator stage gives a regulated output of a fixed voltage.

The circuit runs on a power supply of 5V DC. A transformer 9-0-9V is

used to step down the ac mains voltage from 230V, to 9V AC. The

combination of transformer & diode converts this AC voltage into a

pulsating DC voltage, which is filtered by using an electrolytic capacitor

of rating 1000F, 25V. The IC BC547b provides a regulated power

supply of 5V DC. The 5V DC supply drives and the ICs in the circuit.

http://en.wikipedia.org/wiki/Electronic_componenthttp://en.wikipedia.org/wiki/Conductor_(material)http://en.wikipedia.org/wiki/Signal_tracehttp://en.wikipedia.org/wiki/Industrial_etchinghttp://en.wikipedia.org/wiki/Laminatedhttp://en.wikipedia.org/wiki/Wire_wraphttp://en.wikipedia.org/wiki/Point-to-point_constructionhttp://en.wikipedia.org/wiki/IPC_(electronics)http://en.wikipedia.org/wiki/Electronic_componenthttp://en.wikipedia.org/wiki/Conductor_(material)http://en.wikipedia.org/wiki/Signal_tracehttp://en.wikipedia.org/wiki/Industrial_etchinghttp://en.wikipedia.org/wiki/Laminatedhttp://en.wikipedia.org/wiki/Wire_wraphttp://en.wikipedia.org/wiki/Point-to-point_constructionhttp://en.wikipedia.org/wiki/IPC_(electronics)


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PCB-DESIGNING:-

PCB Designing includes the following steps:-

Fig : PCB Designing process

PROCESSING :-


PROCESSING

CLEANSING

PRINTING

ETCHING

DRILLING

SOLDERING

MASKING


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The layout of a PCB has to incorporate all the information on the board

before one can go on to the artwork preparation. This means that a

concept that clearly defines all the details of the circuit and partly also of

the final equipment, is a prerequisite before the actual layout can start.The detail circuit diagram is very important for the layout designer and

he must also be familiar with the design concept and with the philosophy

behind the equipment. The General Considerations are-

a-) Layout scale:- Depending on the accuracy required, artwork should

be produced at a 1:1 or 2:1 or even 4:1 scale. The layout is best

prepared on the same scale as the artwork. This prevents all the

problems which might be caused by redrawing of layout to the artwork

scale.

b-) Grid system or Graph Paper: - It is commonly accepted practice to

use these for designing.

c-) Board types:-There are two side of a PCB board Component side

& Solder side. Depending on these board are classified as-

Single-sided Boards:- These are used where costs

have to be kept at a minimum & a particular Circuit can beaccommodated on such board. To jump over conductor tracks,

components have to be utilized. If this is not feasible,

jumper wires are used. (Jumper wires should be less otherwise

double-sided PCB should be considered.

Double-sided Boards:- These are made with or

without plated through holes. Plated through holes are fairly

expensive.



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CLEANING:-

The cleaning of the copper surface prior to resist application is an

essential step for any type of PCB process using etches or plating resist.

After scrubbing with the abrasive, a water rinse will remove most of the

remaining slurry.

Fig :Cleaning process

ETCHING:-


Scrubbing

Water Rinse

Wet Brushing

Acid dip

Final Rinse

Drying

Pumice/ Acid Slurry

Tap Water

Tap Water

Hydrochloric Acid-HCl

De-ionized Water

Oven or Blowing of air.


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It is of utmost importance to choose a suitable Etchant Systems.Number

of factors play a major role in it. There are many factors to be considered

Etching speed

Copper solving capacity

Etchant price

Pollution character

Operation characteristics of different etchants:-

Factor

Etchant

Corrosive

-ness

Neutralization

disposition

problem

Toxicity Required

ventilation

Operation

cost

FeCl3 High Medium Low Low Medium

CuCl2 High Low Medium Medium Low

Chromic

acid

High High High High High

Alkaline

ammonia

High Medium Medium High High

Table : Characteristics of different etchants

We have used FeCl3 (Conc. 120 g/litre 0.1 M) for etching.

Reactions Involved:-

FeCl3 + 3H 2O Fe(OH) 3 + 3HCl (Free acid attack to

copper)



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FeCl3 + Cu FeCl2 + CuCl

FeCl3 + CuCl FeCl2 + CuCl2

CuCl2 + Cu 2CuCl

DRILLING:-

The importance of hole drilling into PCBs has further gone with electronic

component miniaturization and its need for smaller holes diameters

(diameters less than half the board thickness) and higher package density.

The following hole diameter tolerances have been generally accepted

wherever no other specifications are mentioned.

Hole Diameter (D) 3 mm + / 0.1 mm

Drill bits are made up of high-speed steel (HSS), Glass epoxy material,

Tungsten Carbide.

SOLDERING:-



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Flux should be removed after Soldering. It is done through washing by 0.51

% HCl followed by Neutralization in dilute alkali to remove corrosive flux.Non-

corrosive is removed by Iso-Propanal.

MASKING:-

It is done for the protection of conductor track from Oxidation.

Designing of PCB Layout:-

A PCB layout is required to place components on the PCB so that the

component area can be minimized and the components can be placed in an

efficient manner. The components can be placed in two ways, either

manually or by software. The manual procedure is quiet cumbersome and is

very inefficient. The other method is by the use of computer software. This

method is advantageous as it saves time and valuable copper area. There

are various softwares available for this purpose like-

Express PCB

Pad2pad

Protel PCB

PCB design e.t.c.

Many of them are loaded with auto routing and auto placement facility. Thesoftware that we have used here is EXPRESS PCB. This software has a

good interface, easy editing options and a wide range of components.

Express P.C.B. :-

Express PCB is a very easy to use Windows application for laying

out printed circuit boards. There are two parts to Express PCB, Express



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SCH for drawing schematics and Express PCB for designing circuit

boards. We downloaded the software from the website

www.expresspcb.com.

There are lots of functions available in the software. This software

is free of cast and also it is very easy to use. The different layers of the

PCB can be viewed by just a click of a button on the interface. And we

easily get its print on paper which is utilized for further processing. We

can design single sided PCB as well as Double Sided PCB with this

Software.

TESTING

After assembling the circuit components on the PCB and soldering

them according to the layout, testing is the next step to be taken. Testing

includes measurement of the parameters such as current, voltage, clock

frequency and comparing them with the standard values provided with

the circuit. Any sort of deviation from the actual values should be

measured and corrected accordingly. This part is known as

troubleshooting.

http://www.expresspcb.com/http://www.expresspcb.com/


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Testing forms a very necessary part of any project. Without testing

a project work never culminates. It is only after testing that one can

guarantee the successful ending of the project. It is only through this

step by which one can determine the faults and also come to knowabout the changes to be introduced.

DIODES

A diode is a device having two terminals and a low resistance to

electrical current in one direction and a high resistance in the other

direction. Diode is a two-element device which passes a signal in one

direction only. They are used most commonly to convert AC to DC,

because they pass the positive part of the wave, and block the negative

part of the AC signal, or, if they are reversed, they pass only the

negative part and not the positive part. Here we used only two types of

diode:



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1) Zener Diode

2) 1N4007

1) ZENER DIODE:-

A Zener diode is a type of diode that permits current in the forward

direction like a normal diode, but also in the reverse direction if the

voltage is larger than the breakdown voltage known as "Zener knee

voltage" or "Zener voltage". The device was named after Clarence

Zener, who discovered this electrical property. The Zener effect asembodied in the zener diode has many applications for control and

regulation.

http://en.wikipedia.org/wiki/Diodehttp://en.wikipedia.org/wiki/Electric_currenthttp://en.wikipedia.org/wiki/Breakdown_voltagehttp://en.wikipedia.org/wiki/Clarence_Zenerhttp://en.wikipedia.org/wiki/Clarence_Zenerhttp://hyperphysics.phy-astr.gsu.edu/Hbase/solids/zener.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/solids/zener.html#c3http://en.wikipedia.org/wiki/Diodehttp://en.wikipedia.org/wiki/Electric_currenthttp://en.wikipedia.org/wiki/Breakdown_voltagehttp://en.wikipedia.org/wiki/Clarence_Zenerhttp://en.wikipedia.org/wiki/Clarence_Zenerhttp://hyperphysics.phy-astr.gsu.edu/Hbase/solids/zener.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/solids/zener.html#c3


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Fig 4.10: Characteristic graph of Zener Diode

The Zener diode is operated in reverse bias mode (positive on its

cathode). It relies on the reverse breakdown voltage occurring at a

specified value. This value is printed on it.

APPLICATIONS:-

1. As a reference source, where the voltage across it is compared with

another voltage.

2. As a voltage regulator, smoothing out any voltages variations

occurring in the supply voltage across the load.

2) RECTIFICATION DIODE [1N4007]:-

The stripe stamped on one end of the diode shows indicates the polarity

of the diode. The stripe shows the cathode side. The top two devices

shown in the picture are diodes used for rectification. They are made to

handle relatively high currents. The device on top can handle as high as

6A, and the one below it can safely handle up to 1A.However, it is best

used at about 70% of its rating because this current value is a maximum

rating. The third device from the top (red color) has a part number of

1S1588. This diode is used for switching, because it can switch on and

off at very high speed. However, the maximum current it can handle is

120 mA. This makes it well suited to use within digital circuits. The

maximum reverse voltage (reverse bias) this diode can handle is 30V.

The device at the bottom of the picture is a voltage regulation diode with

a rating of 6V. When this type of diode is reverse biased, it will resist

changes in voltage. If the input voltage is increased, the output voltagewill not change. (Or any change will be an insignificant amount.) While



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the output voltage does not increase with an increase in input voltage,

the output current will.

This requires some thought for a protection circuit so that too muchcurrent does not flow. The rated current limit for the device is 30 mA.

Generally, a 3-terminal voltage regulator is used for the stabilization of a

power supply. Therefore, this diode is typically used to protect the circuit

from momentary voltage spikes. 3 terminal regulators use voltage

regulation diodes inside.

FEATURES:-

Low forward voltage drop.

Diffused Junction.

AT89S8253 (8-bit Microcontroller with 12 KbyteFlash)

Features:-

Compatible with MCS51 Products

12K Bytes of In-System Programmable (ISP) Flash Program Memory

SPI Serial Interface for Program Downloading


2K Bytes EEPROM Data Memory


64-byte User Signature Array



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2.7V to 5.5V Operating Range

Fully Static Operation: 0 Hz to 24 MHz (in x1 and x2 Modes)





Nine Interrupt Sources

Enhanced UART Serial Port with Framing Error Detection and

Automatic Address Recognition

Enhanced SPI (Double Write/Read Buffered) Serial Interface

Low-power Idle and Power-down Modes

Interrupt Recovery from Power-down Mode

Programmable Watchdog Timer

Dual Data Pointer

Power-off Flag

Flexible ISP Programming (Byte and Page Modes)

Page Mode: 64 Bytes/Page for Code Memory, 32 Bytes/Page for

Data Memory

Four-level Enhanced Interrupt Controller

Programmable and Fuseable x2 Clock Option

Internal Power-on Reset



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42-pin PDIP Package Option for Reduced EMC Emission

Green (Pb/Halide-free) Packaging Option

1. Description :-

The AT89S8253 is a low-power, high-performance CMOS 8-bit

microcontroller with 12K bytes of In-System Programmable (ISP) Flash

program memory and 2K bytes of EEPROM data memory. The device is

manufactured using Atmels high-density nonvolatile memory

technology and is compatible with the industry-standard MCS-

51instruction set and pinout. The on-chip downloadable Flash allows the

program memory to be reprogrammed in-system through an SPI serial

interface or by a conventional nonvolatile memory programmer. By

combining a versatile 8-bit CPU with downloadable Flash on amonolithic chip, the Atmel AT89S8253 is a powerful microcontroller

which provides a highly-flexible and cost-effective solution to many

embedded control applications.

The AT89S8253 provides the following standard features: 12K bytes of

In-System Programmable Flash, 2K bytes of EEPROM, 256 bytes of

RAM, 32 I/O lines, programmable watchdog timer, two data pointers,

three 16-bit timer/counters, a six-vector, four-level interrupt architecture,a full duplex serial port, on-chip oscillator, and clock circuitry. In addition,



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the AT89S8253 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,

serial port, and interrupt system to continue functioning. The Power-down mode saves the RAM contents but freezes the oscillator, disabling

all other chip functions until the next external interrupt or hardware

reset.

The on-board Flash/EEPROM is accessible through the SPI serial

interface. Holding RESET active forces the SPI bus into a serial

programming interface and allows the program memory to be written to

or read from, unless one or more lock bits have been activated.

2. Pin Configurations :-

2.1 40P6 40-lead PDIP

2.2 44A 44-lead TQFP



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2.3 44J 44-lead PLCC

2.4 42PS6 PDIP



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3. Pin Description:-

3.1 VCC: Supply voltage (all packages except 42-PDIP).

3.2 GND: Ground (all packages except 42-PDIP; for 42-PDIP GND

connects only the logic core and the embedded program/data

memories).

3.3 VDD: Supply voltage for the 42-PDIP which connects only the

logic core and the embedded pro-

gram/data memories.

3.4 PWRVDD: Supply voltage for the 42-PDIP which connects only

the I/O Pad Drivers. The application board must connect both VDD andPWRVDD to the board supply voltage.

3.5 PWRGND: Ground for the 42-PDIP which connects only the I/O

Pad Drivers. PWRGND and GND are weakly connected through the

common silicon substrate, but not through any metal links. The

application board must connect both GND and PWRGND to the board



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ground.

3.6 Port 0: Port 0 is an 8-bit open drain bi-directional I/O port. As an

output port, each pin can sink six TTL inputs. When 1s are written to port

0 pins, the pins can be used as high-impedance inputs.

Port 0 can 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 programverification.

3.7 Port 1: Port 1 is an 8-bit bi-directional I/O port with internal pull-

ups. The Port 1 output buffers can

sink/source six TTL inputs. When 1s are written to Port 1 pins, they are

pulled high by the weak

internal pull-ups and can be used as inputs. As inputs, Port 1 pins that

are externally being pulled low will source current (IIL,150 A typical)

because of the weak internal pull-ups. Some Port 1 pins provide

additional functions. P1.0 and P1.1 can be configured to be the

timer/counter 2 external count input (P1.0/T2) and the timer/counter 2

trigger input (P1.1/T2EX), respectively. Furthermore, P1.4, P1.5, P1.6,

and P1.7 can be configured as the SPI slave port select, datainput/output and shift clock input/output pins as shown in the following

table.



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ups. The Port 2 output buffers can sink/source six TTL inputs. When 1s

are written to Port 2 pins, they are pulled high by the weak internal pull-

ups and can be used as inputs. As inputs, Port 2 pins that are externally

being pulled low will source current (IIL,150 A typical) because of the

weak 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 use 16-bit addresses (MOVX @ DPTR). In this

application, Port 2 uses strong internal pull-ups when emitting 1s. During

accesses to external data memory that use 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.


ups. The Port 3 output buffers can sink/source six TTL inputs. When 1s

are written to Port 3 pins, they are pulled high by the weak internal pull-

ups and can be used as inputs. As inputs, Port 3 pins that are externally

being pulled low will source current (IIL,150 A typical) because of the

weak internal pull-ups. Port 3 receives some control signals for Flash

programming and verification. Port 3 also serves the functions of various

special features of the AT89S8253, as shown in the following table.



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3.10 RST: Reset input. A high on this pin for at least two machine

cycles while the oscillator is running resets the device.

3.11 ALE/PROG:Address Latch Enable. ALE/PROG is an output pulsefor latching the low byte of the address (on its falling edge) 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 bedisabled by setting bit 0 of the AUXR SFR at 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.

3.12 PSEN: Program Store Enable. PSEN is the read strobe to external



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program memory (active low). When the AT89S8253 is executing code

from external program memory, PSEN is activated twice each machine

cycle, except that two PSEN activations are skipped during each access

to external data memory.

3.13 EA/VPP: External 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 pinalso receives the 12-volt programming enable voltage (VPP) during Flash

programming when 12-volt programming is selected.

3.14 XTAL1: Input to the inverting oscillator amplifier and input to the

internal clock operating circuit.

3.15 XTAL2: Output from the inverting oscillator amplifier. XTAL2

should not drive a board-level clock without a buffer.

4. Block Diagram:-



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5. Data Memory EEPROM and RAM:-

The AT89S8253 implements 2K bytes of on-chip EEPROM for data

storage and 256 bytes of RAM. The upper 128 bytes of RAM occupy a



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parallel space to the Special Function Registers. That means the upper

128 bytes have the same addresses as the SFR space but are

physically separate from SFR space. When an instruction accesses an

internal location above address 7FH, the address mode used in theinstruction specifies whether the CPU accesses the upper 128 bytes of

RAM or the SFR space. Instructions that use direct addressing access

the SFR space. For example, the following direct addressing instruction

accesses the SFR at location 0A0H (which is P2).

MOV 0A0H, #data

Instructions that use indirect addressing access the upper 128 bytes of

RAM. For example, the following indirect addressing instruction, where

R0 contains 0A0H, accesses the data byte at address 0A0H, rather than

P2 (whose address is 0A0H).

MOV @R0, #data

Note that stack operations are examples of indirect addressing, so the

upper 128 bytes of data RAM are available as stack space. The on-chip

EEPROM data memory is selected by setting the EEMEN bit in theEECON register at SFR address location 96H. The EEPROM address

range is from 000H to 7FFH. MOVX instructions are used to access the

EEPROM. To access off-chip data memory with the MOVX instructions,

the EEMEN bit needs to be set to 0. During program execution mode

(using the MOVX instruction) there is an auto-erase capability at the byte

level. This means that the user can update or modify a single EEPROM

byte location in real-time without affecting any other bytes. The EEMWE

bit in the EECON register needs to be set to 1 before any byte location

in the EEPROM can be written. User software should reset EEMWE bit

to 0 if no further EEPROM write is required. EEPROM write cycles in

the serial programming mode are self-timed and typically take 4 ms. The

progress of EEPROM write can be monitored by reading the RDY/BSY

bit (read-only) in SFR EECON. RDY/BSY = 0 means programming is still

in progress and RDY/BSY= 1 means an EEPROM write cycle is

completed and another write cycle can be initiated. Bit EELD in EECON

controls whether the next MOVX instruction will only load the write buffer

of the EEPROM or will actually start the programming cycle. By setting



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EELD, only load will occur. Before the last MOVX in a given page of 32

bytes, EELD should be cleared so that after the last MOVX the entire

page will be programmed at the same time. This way, 32 bytes will only

require 4 ms of programming time instead of 128 ms required in singlebyte programming.

16 CHARACTER LCD x 2

Features:-

5 x 8 dots with cursor

Built-in controller (KS 0066 or Equivalent)



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+ 5V power supply (Also available for + 3V)

1/16 duty cycle

B/L to be driven by pin 1, pin 2 or pin 15, pin 16 or A.K (LED)

N.V. optional for + 3V power supply



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LM78XX

3-Terminal 1A Positive Voltage Regulator

Features:-

Output Current up to 1A

Output Voltages of 5, 6, 8, 9, 10, 12, 15, 18, 24



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Thermal Overload Protection

Short Circuit Protection

Output Transistor Safe Operating Area Protection

General description:-

The LM78XX series of three terminal positive regulators are available in

the TO-220 package and with several fixed output voltages, making

them useful in a wide range of applications. Each type employs internal

current limiting, thermal shut down and safe operating area protection,

making it essentially indestructible. If adequate heat sinking is provided,

they can deliver over 1A output current. Although designed primarily as

fixed voltage regulators, these devices can be used with external

components to obtain adjustable voltages and currents.

Block Diagram:-



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Pin Assignment:-

Absolute Maximum Rating:-

Absolute maximum ratings are those values beyond which damage tothe device may occur. The datasheet specifications should be met,

without exception, to ensure that the system design is reliable over its

power supply, temperature, and output/input loading variables. Fairchild

does not recommend operation outside datasheet specifications.



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Note: Load and line regulation are specified at constant junction temperature.

Changes in VO due to heating effects must be taken into account separately.Pulse testing with low duty is used.

These parameters, although guaranteed, are not 100% tested in production.



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Changes in VO due to heating effects must be taken into account separately.

Pulse testing with low duty is used.




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Note: Load and line regulation are specified at constant junction temperature.Changes in VO due to heating effects must be taken into account separately.





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Note: Load and line regulation are specified at constant junction temperature.Changes in VO due to heating effects must be taken into account separately.





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Note:

Load and line regulation are specified at constant junction temperature.





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UNDERSTANDING RELAYS

Relays:-

Relays are used throughout the automobile. Relays which come in

assorted sizes, ratings, and applications, are used as remote control

switches. A typical vehicle can have 20 relays or more



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Relay Locations:-

Relays are located throughout the entire vehicle. Relay blocks, both

large and small, are located in the engine compartment; behind the left

or right kick panels, or under the dash are common locations. Relays are

often grouped together or with other components like fuses or placed by

themselves.

Relay Position Identification:-

Relay / Fuse block covers usually label the location and position of each

fuse, relay, or fuse element contained within.



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Relay Applications:-

Relays are remote control electrical switches that are controlled by

another switch, such as a horn switch or a computer as in a power traincontrol module. Relays allow a small current flow circuit to control a

higher current circuit. Several designs of relays are in use today, 3-pin,

4-pin, 5-pin, and 6-pin, single switch or dual switches.

Relay Operation:-



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All relays operate using the same basic principle. Our example will use a

commonly used 4 -pin relay. Relays have two circuits: A control circuit

(shown in GREEN) and a load circuit (shown in RED). The control circuit

has a small control coil while the load circuit has a switch. The coilcontrols the operation of the switch.

Relay Energized (On):-

Current flowing through the control circuit coil

(pins 1 and 3) creates a small magnetic field which causes the switch toclose, pins 2 and 4. The switch, which is part of the load circuit, is used

to control an electrical circuit that may connect to it. Current now flows

through pins 2 and 4 shown in RED, when the relay in energized.

Relay De-Energized (Off):-

When current stops flowing through the controlcircuit, pins 1 and 3, the relay becomes de-



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energized. Without the magnetic field, the switch opens and current is

prevented from flowing through pins 2 and 4. The relay is now OFF.

Relay Operation:-

When no voltage is applied to pin 1, there is no current flow through the

coil. No current means no magnetic field is developed, and the switch is

open. When voltage is supplied to pin 1, current flow though the coil

creates the magnetic field needed to close the switch allowing continuity

between pins 2 and 4.

Relay Design Id:-

Relays are either Normally Open or Normally Closed. Notice the position

of the switches in the two relays shown below. Normally open relayshave a switch that remains open until energized (ON) while normally



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closed relays are closed until energized. Relays are always shown in the

de-energized position (no current flowing through the control circuit -

OFF). Normally open relays are the most common in vehicles; however

either can be use in Automotive applications.

Normal ly open (NO)

Normally

closed (NC)

Normally Closed Relays:-

The operation of a Normally Closed relay is the same to that of a

Normally Open relay, except backwards. In other words, when the relay

control coil is NOT energized, the relay switch contacts are closed,

completing the circuit through pins 2 and 4. When the control coil isenergized, the relay switch contacts opens, which breaks the circuit

open and no continuity exists between pins 2 and 4.



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DE-ENERGIZED (OFF) ENERGIZED (ON)

Actual Relay Design:-

Current flows through the control coil, which is wrapped around an iron

core. The iron core intensifies the magnetic field. The magnetic field

attracts the upper contact arm and pulls it down, closing the contacts

and allowing power from the power source to go to the load.



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Relay Variations:-

Other relay variations include three and five pin relays. A 3-PIN relay

instead of two B+ input sources, this relay has one B+ input at pin 1.

Current splits inside the relay, supplying power to both the control and

load circuits. A 5-PIN relay has a single control circuit, but two separate

current paths for the switch: One when the relay is de-energized (OFF

no current through the control coil) and the other the energized (ON -

current is flowing through the control coil). When the 5-PIN relay is de-

energized (OFF), pins 4 and 5 have continuity. When the relay is

energized (ON), pins 3 and 5 have continuity.

3-PIN 4-PIN 5-PIN



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ISO Standardized Relays:-

ISO relays were designed to try and standardize relay connections,

making it easier to test and design systems. ISO relays are currentlyused by almost all automotive manufacturers today. Both 4 and 5 pin

designs are used in both standard mini and micro sizes. FYI: ISO is

short for International Standard Organization.

STANDARD MINI SHOWN



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Standard Mini Iso Relays Types:-

Below are two popular standard MINI ISO relay configurations. The size

of a ISO Standard MINI relay is a 1" square cube. Both 4 and 5 pins

designs are used.

5 PIN

MINI RELAY

4 PIN

MINI RELAY



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ISO Micro Relay Types:-

Below are two popular MICRO ISO relay configurations. The size of a

ISO MICRO relay is a 1" x 1" x 1/2" square (1/2 as thick as a Mini relay).Both 4 and 5 pins designs are used.

5 PIN

MICRO RELAY

4 PIN

MICRO RELAY



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Voltage Spikes:-

When the switch is closed (shown left), current flows through the coil

from positive to negative as shown in red. This current flow creates amagnetic field around the coil. The top of the coil is positive, and the

bottom is negative.

When the switch is opened (shown on right), current stops flowing

through the control circuit coil, and the magnetic field surrounding the

coil cannot be maintained. As the magnetic field collapses across the

coil, it induces a voltage into itself, creating a reverse polarity voltage

spike of several hundred volts. Although the top of the coil is still 12 volts

positive, the bottom of the coil produces several hundred positive volts

(200+ volts or

more); 200 is "more positive" and stronger than 12 volts, so current flows

from the bottom of the coil up towards the top.

Voltage Suppression Relays:-



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Relays are often controlled by a computer. When relays are controlled

by semiconductors such as transistors, they require some type of

voltage suppression device. Solid state circuits are vulnerable to voltage

spikes. Voltage spikes slam against transistors, destroying them. Whilesome computer circuits have voltage suppression built inside the

computer,

others rely on voltage suppression from within the relay. High ohm

resistors, diodes, or capacitors can be used for voltage suppression.

Diodes and resistors are the most common. NOTE: Relays are usually

clearly marked if a suppression diode or resistor is present.

Relays With De-Spiking Diodes:-

A de-spiking (clamping) diode is connected in

parallel with the relay coil. It is in the reverse biased position when the

relay is turned on; therefore no current will flow through the diode. When

the relay control circuit is opened (turned OFF), current stops flowing

through the coil, causing the magnetic field to collapse. The magneticlines of force cut through the coil and induce a counter voltage (a voltage

in reverse polarity) into the winding. The counter voltage begins to raise.

When the bottom side of the diode sees .7 volts more positive voltage

than the top, the diode becomes forward biased, allowing the excess

voltage to pass, completing the circuit to the other end of the coil. The

current flows around in the diode and coil circuit until the voltage is

dissipated.



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Relays With

De- Spiking

Resistors:-

High ohm resistors are sometimes used instead of diodes. A resistor is

more durable than a diode and can suppress voltage spikes similar to a

diode, but the resistor will allow current to flow through it whenever the

relay is on. Therefore resistance of the resistor must be fairly high (about600 ohms) in order to prevent too much current flow in the circuit. High

ohm resistors are not quite as efficient at suppressing a voltage spike as

diodes.

Circuit Identification:-



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Relays are easy to test but often misunderstood. Using a 4 pin relay for

our example, we must first identify the pins. Some manufacturers place

a diagram and pin ID on the outside of the relay case to show which pins

are part of the control circuit and which pins are part of the load circuit.

Continuity Check For Id:-



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If the relay is not labeled, use an ohmmeter and check to see which pins

are connected to each other. You should typically find an ohm value of

approximately 50 to 120 ohms between two of the pins. This is the

control circuit. If the coil is less that 50 ohms it could be suspect. Referto manual to verify reading. The remaining two pins should read OL

(infinite) if it's a normally open relay, or 0 ohms (continuity) if it's a

normally closed relay. If the readings are correct, proceed to the next

test. Note: If none of the relay pins showed a coil value and all pins show

OL or 0 ohms, the control coil is damaged and should be replaced.

Practical Testing:-

Once the pins have been identified, energize the control circuit by



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supplying B+ to pin 1 and a ground to pin 3. A faint "click" will be heard;

although this "click" means the switch has moved (closed), it does not

mean the relay is good. The load circuit switch contacts could still be

faulty (high resistance), and further testing is required. A commonmistake technicians make is they hear a "click" and assume the relay is

good. Take the extra step and verify operation.

Operational Check With Testlight:-

Now start the second part of the test. Energize the relay (control side) bysupplying B+ to pin 1 and a ground to pin 3. A click should be heard.



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With the relay still energized, supply B+ pin 2 of the load circuit. The test

light will be on. De-energize (remove B+) the control circuit at pin 1; the

test light at pin 4 should go off. A test light is preferred because a test

light will draw current through the switch.

Operational Check With Voltmeter:-

A voltmeter can be substituted in place of a test light; however be aware

if the contacts are partially burned, the voltmeter will show voltage

indicating good contact even when bad. Remember high impedance

digital voltmeters draw almost no current. Energize the relay (control



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side) by supplying B+ to pin 1 and a ground to pin 3. A click should be

heard. With the relay still energized supply B+ to pin 2 of the load circuit.

Connect the RED lead to pin 4 and the BLACK lead to ground. The

voltmeter will indicate source voltage (12V).De-energize (remove B+) thecontrol circuit at pin 1; the voltmeter should now read "zero". Re-

energize the relay and the voltmeter should return to 12 volts.

Operational Check With An Ohmmeter:-

An ohmmeter can also be used to test the load circuit, but the same

problem as the voltmeter comes into play. Energize the relay (control

side). Supply B+ to pin 1 and a ground (neg.) to pin 3. A click should be

heard. Place the leads on an ohmmeter to across pin 2 and pin 4.



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Assuming it is a normally open relay the ohmmeter will indicate a

complete circuit (close to zero -0 ohms). De-energize the control circuit

at pin 1(remove B+). The ohmmeter should indicate OL (an open circuit -

infinite). Re-energize the relay and the ohmmeter should return to "zero"ohms. Note: some manufactures provide a maximum ohm value when

the switch contacts are closed, example 5 ohms max.

ULN2803A 500-mA Rated Collector Current

High-Voltage Outputs . . . 50 V

Output Clamp Diodes

Inputs Compatible With Various Types of Logic

Relay Driver Applications



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Compatible with ULN2800A Series

Description/ordering information:-

The ULN2803A is a high-voltage, high-current Darlington transistor

array. The device consists of eight npn Darlington pairs that feature high

voltage outputs with common-cathode clamp

diodes for switching inductive loads. The

collector-current rating of each Darlington pair

is 500mA.The Darlington pairs may be

connected in parallel for higher current

capability.

Applications include relay drivers, hammer

drivers, lamp drivers, display drivers (LED and

gas discharge), line drivers, and logic buffers.

The ULN2803A has a 2.7-k series base

resistor for each Darlington pair for operation

directly with TTL or 5-V CMOS devices.

Logic Diagram :-



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Schematic (each Darlington pair) :-

Absolute maximum ratings at 25 C free-air temperature (unless

otherwise noted):-

Collector-emitter voltage 50V

Input voltage ... 30V

Continuous collector current .. 500mA

Output clamp diode current ... 500mA

Total substrate-terminal current .. -2.5A



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Operating virtual junction

temperature, TJ . 1500C

Storage temperature range, Tstg. -650C to

1500C

Parameter measurement information:-



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Propagation delay times




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Latch-up Test

REFERENCES

Websites:-

www.8051projects.info

www.wikipedia.org

www.atmel.com

www.fairchildsemi.com

www.alldatasheet.com

Books:-

http://www.8051projects.info/http://www.wikipedia.org/http://www.fairchildsemi.com/http://www.alldatasheet.com/http://www.8051projects.info/http://www.wikipedia.org/http://www.fairchildsemi.com/http://www.alldatasheet.com/


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The 8051 Microcontroller

By I. Scott MacKenzie, Raphael C.-W. Phan

Published By Dorling Kindersley (India) Pvt. Ltd. Published in 2008

Electronic Devices And Circuit Theory

By Robert L. Boylestad, Louis Nashelsky

Published By Dorling Kindersley (India) Pvt. Ltd.

Published in 2008

door locking system with 1 master password & 3 user passwords

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