NEW GENERATION POLLING METHOD USING RF

(radio frequency)

INDEX

1. Index

2. Abstract

3. Chapter-1: Embedded System

1.1 Introduction

1.2 Microprocessor and Microcontroller

1.3 Introduction to Application of embedded system

1.4 Industrial functions of embedded system

1.5 Compared with commercial system

4. Chapter-2: Over view of the Project

2.1 Introduction of project

2.2 Block Diagram

2.3 Software used in Project

5. Chapter-3: Microcontroller

3.1 Description

3.2 Features

3.3 Architecture

3.4 Pin-Configuration of AT89S52

3.5 Pin-Description

6. Chapter-4: Hardware Description

4.1 Power Supply board

7. Chapter-5: Technology

5.1 Communication System

5.2 RF Communication

5.3 Encoder & decoder

5.4 Keypad

8. Coding

9. Conclusion

10. Future Aspects

11. Applications

12. Bibliography

LIST OF FIGURES

S.no CONTENTS PAGE NUMBERS

ABSTRACT

AIM:

The main aim of this project is to develop a genuine polling system for elections by means of a

wireless communication using radio frequencies. We use a EEPROM for storing, keypad for

entering the data and LCD’s for the purpose of displaying.

DESCRIPTION:

In general we observe that rigging happens at

the time of elections. Due to this ingenuine

polling, the winner may loss his/her place. To

avoid this ingenuine polling or malpractices

in elections, this project work has been taken

up.

In this project there are two sections, a

transmitter section and a receiver section. The

transmitter section consists of a keypad with

four switches, a microcontroller, a LCD and a

RF transmitter with an encoder. The receiver

section consists of a microcontroller, a LCD,

an EEPROM and a RF receiver with a

decoder.

In this prototype project we are arranging poll for three or four members. Each person has

different passwords.

When a person enters the polling booth, he has to enter his password along with the serial

number allotted to the party which he likes to vote in the transmitter section by using the keypad

provided. The data (password and the serial number allotted to the party) entered by the person

or the voter will be displayed on the LCD provided in the transmitter section simultaneously.

This password entered by the voter is checked by the microcontroller of the transmitter section.

According to the program written for controller, controller compares the data in the controller

with that data the person has entered. The vote is counted only if the password entered is correct

as checked by the microcontroller. The data from the microcontroller is transferred to the RF

RF COMMUNICATION:

Radio frequency (RF) radiation is a subset of electromagnetic radiation with a wavelength of 100 km to 1 mm and a frequency of 3 kHz to 300 GHz, respectively. This range of electromagnetic radiation constitutes the radio spectrum.It has the transmitter and the receiver part for the purpose of communication.

Transmitter Receiver

transmitter with an encoder of the transmitter section. The encoder encodes the data and the RF

transmitter transmits this encoded data by using the radio frequency signals. The RF receiver in

the receiver section receives this encoded data and decodes it by using the decoder provided.

This data is then fed to the microcontroller at the receiver section. The voter details i.e. password

and the votes given to the party will be stored in the EEPROM in the receiver section. The LCD

of the receiver section displays the votes of the respective parties. As the polling process takes

place, the votes attained by the parties will be changed on the LCD of the receiver section

simultaneously.

If a person tries to vote for another time, he has to enter his password in the transmitter section.

This data entered in the transmitter section is transmitted to the receiver section by using RF

signals. Then the microcontroller compares this password with EEPROM data. If it is already

there in EEPROM, the system doesn’t allow him to vote for second time.

From the above discussion we can conclude that genuine polling system is completely

implemented by using Radio Frequency communication.

CHAPTER-1

EMBEDDED SYSTEMS

Introduction:

An embedded system is a system which is going to do a predefined specified task and is

even defined as combination of both software and hardware. A general-purpose definition of

embedded systems is that they are devices used to control, monitor or assist the operation of

equipment, machinery or plant. "Embedded" reflects the fact that they are an integral part of the

system. At the other extreme a general-purpose computer may be used to control the operation of

a large complex processing plant, and its presence will be obvious.

All embedded systems are including computers or microprocessors. Some of these

computers are however very simple systems as compared with a personal computer.

The very simplest embedded systems are capable of performing only a single function or

set of functions to meet a single predetermined purpose. In more complex systems, an

application program that enables the embedded system to be used for a particular purpose in a

specific application determines the functioning of the embedded system. The ability to have

programs means that the same embedded system can be used for a variety of different purposes.

In some cases a microprocessor may be designed in such a way that the application software for

a particular purpose can be added to the basic software in a second process, after which it is not

possible to make further changes. The applications software on such processors is sometimes

referred to as firmware.

The simplest devices consist of a single microprocessor (often called a "chip”), which

may itself be packaged with other chips in a hybrid system or Application Specific Integrated

Circuit (ASIC). Its input comes from a detector or sensor and its output goes to a switch or

activator which (for example) may start or stop the operation of a machine or, by operating a

valve, may control the flow of fuel to an engine.

A embedded system is a combination of both software and hardware.

Figure: Block diagram of Embedded System

Software deals with the languages like ALP, C, and VB etc., and Hardware deals with

Processors, Peripherals, and Memory.

Memory: It is used to store data or address.

Peripherals: These are the external devices connected

Processor: It is an IC which is used to perform some task

Applications of embedded systems

Manufacturing and process control

Construction industry

Transport

Buildings and premises

Domestic service

Communications

Office systems and mobile equipment

Banking, finance and commercial

Embedded

System

Software Hardware

ALP

C

VB Etc.,

Processor

Peripherals

memory

Medical diagnostics, monitoring and life support

Testing, monitoring and diagnostic systems

Processors are classified into four types like:

Micro Processor (µp)

Micro controller (µc)

Digital Signal Processor (DSP)

Application Specific Integrated Circuits (ASIC)

Micro Processor (µp):

A silicon chip that contains a CPU. In the world of personal computers, the terms microprocessor

and CPU are used interchangeably. At the heart of all personal computers and most workstations

sits a microprocessor. Microprocessors also control the logic of almost all digital devices, from

clock radios to fuel-injection systems for automobiles.

Three basic characteristics differentiate microprocessors:

Instruction set : The set of instructions that the microprocessor can execute.

Bandwidth : The number of bits processed in a single instruction.

Clock speed : Given in megahertz (MHz), the clock speed determines how many instructions

per second the processor can execute.

In both cases, the higher the value, the more powerful the CPU. For example, a 32-bit

microprocessor that runs at 50MHz is more powerful than a 16-bit microprocessor that runs at

25MHz. In addition to bandwidth and clock speed, microprocessors are classified as being either

RISC (reduced instruction set computer) or CISC (complex instruction set computer).

A microprocessor has three basic elements, as shown above. The ALU performs all

arithmetic computations, such as addition, subtraction and logic operations (AND, OR, etc). It is

controlled by the Control Unit and receives its data from the Register Array.   The Register Array

is a set of registers used for storing data. These registers can be accessed by the ALU very

quickly. Some registers have specific functions - we will deal with these later.   The Control Unit

controls the entire process. It provides the timing and a control signal for getting data into and

out of the registers and the ALU and it synchronizes the execution of instructions (we will deal

with instruction execution at a later date).  

Three Basic Elements of a Microprocessor

Micro Controller (µc):

A microcontroller is a small computer on a single integrated circuit containing a processor core,

memory, and programmable input/output peripherals. Program memory in the form of NOR

flash or OTP ROM is also often included on chip, as well as a typically small amount of RAM.

Microcontrollers are designed for embedded applications, in contrast to the microprocessors

used in personal computers or other general purpose applications.

Timer, Counter, serial communication ROM, ADC, DAC, Timers, USART, Oscillators

Etc.,

ALU

CU

Memory

Figure: Block Diagram of Micro Controller (µc)

Digital Signal Processors (DSPs):

Digital Signal Processors is one which performs scientific and mathematical operation.

Digital Signal Processor chips - specialized microprocessors with architectures designed

specifically for the types of operations required in digital signal processing. Like a general-

purpose microprocessor, a DSP is a programmable device, with its own native instruction code.

DSP chips are capable of carrying out millions of floating point operations per second, and like

their better-known general-purpose cousins, faster and more powerful versions are continually

being introduced. DSPs can also be embedded within complex "system-on-chip" devices, often

containing both analog and digital circuitry.

Application Specific Integrated Circuit (ASIC):

ASIC is a combination of digital and analog circuits packed into an IC to achieve the desired

control/computation function

ASIC typically contains

CPU cores for computation and control

Peripherals to control timing critical functions

Memories to store data and program

Analog circuits to provide clocks and interface to the real world which is analog in nature

I/Os to connect to external components like LEDs, memories, monitors etc.

Computer Instruction Set:

There are two different types of computer instruction set there are:

1. RISC (Reduced Instruction Set Computer) and

2. CISC (Complex Instruction Set computer)

Reduced Instruction Set Computer (RISC):

A RISC (reduced instruction set computer) is a microprocessor that is designed to perform a

smaller number of types of computer instruction so that it can operate at a higher speed (perform

more million instructions per second, or millions of instructions per second). Since each

instruction type that a computer must perform requires additional transistors and circuitry, a

larger list or set of computer instructions tends to make the microprocessor more complicated

and slower in operation.

Besides performance improvement, some advantages of RISC and related design improvements

are:

A new microprocessor can be developed and tested more quickly if one of its aims is to be less

complicated.

Operating system and application programmers who use the microprocessor's instructions will

find it easier to develop code with a smaller instruction set.

The simplicity of RISC allows more freedom to choose how to use the space on a

microprocessor.

Higher-level language compilers produce more efficient code than formerly because they have

always tended to use the smaller set of instructions to be found in a RISC computer.

RISC characteristics:

Simple instruction set:

In a RISC machine, the instruction set contains simple, basic instructions, from which more

complex instructions can be composed.

Same length instructions.:

Each instruction is the same length, so that it may be fetched in a single operation.

1 machine-cycle instructions:

Most instructions complete in one machine cycle, which allows the processor to handle several

instructions at the same time. This pipelining is a key technique used to speed up RISC

machines.

Complex Instruction Set Computer (CISC):

CISC, which stands for Complex Instruction Set Computer, is a philosophy for designing chips

that are easy to program and which make efficient use of memory. Each instruction in a CISC

instruction set might perform a series of operations inside the processor. This reduces the number

of instructions required to implement a given program, and allows the programmer to learn a

small but flexible set of instructions.

The advantages of CISC:

At the time of their initial development, CISC machines used available technologies to optimize

computer performance.

Microprogramming is as easy as assembly language to implement, and much less expensive than

hardwiring a control unit.

The ease of micro-coding new instructions allowed designers to make CISC machines upwardly

compatible: a new computer could run the same programs as earlier computers because the new

computer would contain a superset of the instructions of the earlier computers.

As each instruction became more capable, fewer instructions could be used to implement a given

task. This made more efficient use of the relatively slow main memory.

Because micro program instruction sets can be written to match the constructs of high-level

languages, the compiler does not have to be as complicated.

The disadvantages of CISC:

CISC designers soon realized that the CISC philosophy had its own problems, which include:

Earlier generations of a processor family generally were contained as a subset in every new

version --- so instruction set & chip hardware become more complex with each generation of

computers.

So that as many instructions as possible could be stored in memory with the least possible

wasted space, individual instructions could be of almost any length---this means that different

instructions will take different amounts of clock time to execute, slowing down the overall

performance of the machine.

Many specialized instructions aren't used frequently enough to justify their existence ---

approximately 20% of the available instructions are used in a typical program.

CISC instructions typically set the condition codes as a side effect of the instruction. Not only

does setting the condition codes take time, but programmers have to remember to examine the

condition code bits before a subsequent instruction changes them.

Memory Architecture:

There two different type’s memory architectures there are:

Harvard Architecture

Von-Neumann Architecture

Harvard Architecture:

Computers have separate memory areas for program instructions and data. There are two or more

internal data buses, which allow simultaneous access to both instructions and data. The CPU

fetches program instructions on the program memory bus.

The Harvard architecture is a computer architecture with physically separate storage and signal

pathways for instructions and data. The term originated from the Harvard Mark I relay-based

computer, which stored instructions on punched tape (24 bits wide) and data in electro-

mechanical counters. These early machines had limited data storage, entirely contained within

the central processing unit, and provided no access to the instruction storage as data. Programs

needed to be loaded by an operator, the processor could not boot itself.

Figure: Harvard Architecture

Modern uses of the Harvard architecture:

The principal advantage of the pure Harvard architecture - simultaneous access to more than one

memory system - has been reduced by modified Harvard processors using modern CPU cache

systems. Relatively pure Harvard architecture machines are used mostly in applications where

tradeoffs, such as the cost and power savings from omitting caches, outweigh the programming

penalties from having distinct code and data address spaces.

Digital signal processors (DSPs) generally execute small, highly-optimized audio or video

processing algorithms. They avoid caches because their behavior must be extremely

reproducible. The difficulties of coping with multiple address spaces are of secondary concern to

speed of execution. As a result, some DSPs have multiple data memories in distinct address

spaces to facilitate SIMD and VLIW processing. Texas Instruments TMS320 C55x processors,

as one example, have multiple parallel data busses (two write, three read) and one instruction

bus.

Microcontrollers are characterized by having small amounts of program (flash memory) and data

(SRAM) memory, with no cache, and take advantage of the Harvard architecture to speed

processing by concurrent instruction and data access. The separate storage means the program

and data memories can have different bit depths, for example using 16-bit wide instructions and

8-bit wide data. They also mean that instruction pre-fetch can be performed in parallel with other

activities. Examples include, the AVR by Atmel Corp, the PIC by Microchip Technology, Inc.

and the ARM Cortex-M3 processor (not all ARM chips have Harvard architecture).

Even in these cases, it is common to have special instructions to access program memory as data

for read-only tables, or for reprogramming.

Von-Neumann Architecture:

A computer has a single, common memory space in which both program instructions and data

are stored. There is a single internal data bus that fetches both instructions and data. They cannot

be performed at the same time

The von Neumann architecture is a design model for a stored-program digital computer that

uses a central processing unit (CPU) and a single separate storage structure ("memory") to hold

both instructions and data. It is named after the mathematician and early computer scientist John

von Neumann. Such computers implement a universal Turing machine and have a sequential

architecture.

A stored-program digital computer is one that keeps its programmed instructions, as well as its

data, in read-write, random-access memory (RAM). Stored-program computers were

advancement over the program-controlled computers of the 1940s, such as the Colossus and the

ENIAC, which were programmed by setting switches and inserting patch leads to route data and

to control signals between various functional units. In the vast majority of modern computers, the

same memory is used for both data and program instructions. The mechanisms for transferring

the data and instructions between the CPU and memory are, however, considerably more

complex than the original von Neumann architecture.

The terms "von Neumann architecture" and "stored-program computer" are generally used

interchangeably, and that usage is followed in this article.

Figure: Schematic of the Von-Neumann Architecture.

Basic Difference between Harvard and Von-Neumann Architecture

The primary difference between Harvard architecture and the Von Neumann architecture is in

the Von Neumann architecture data and programs are stored in the same memory and managed

by the same information handling system.

Whereas the Harvard architecture stores data and programs in separate memory devices and they

are handled by different subsystems.

In a computer using the Von-Neumann architecture without cache; the central processing unit

(CPU) can either be reading and instruction or writing/reading data to/from the memory. Both of

these operations cannot occur simultaneously as the data and instructions use the same system

bus.

In a computer using the Harvard architecture the CPU can both read an instruction and access

data memory at the same time without cache. This means that a computer with Harvard

architecture can potentially be faster for a given circuit complexity because data access and

instruction fetches do not contend for use of a single memory pathway.

Today, the vast majority of computers are designed and built using the Von Neumann

architecture template primarily because of the dynamic capabilities and efficiencies gained in

designing, implementing, operating one memory system as opposed to two. Von Neumann

architecture may be somewhat slower than the contrasting Harvard Architecture for certain

specific tasks, but it is much more flexible and allows for many concepts unavailable to Harvard

architecture such as self programming, word processing and so on.

Harvard architectures are typically only used in either specialized systems or for very specific

uses. It is used in specialized digital signal processing (DSP), typically for video and audio

processing products. It is also used in many small microcontrollers used in electronics

applications such as Advanced RISK Machine (ARM) based products for many vendors.

CHAPTER-2

Introduction

Electronic voting (also known as e-voting) is a term encompassing several different types of

voting, embracing both electronic means of casting a vote and electronic means of counting

votes.

Electronic voting technology can include punched cards, optical scan voting systems and

specialized voting kiosks (including self-contained direct-recording electronic voting systems, or

DRE). It can also involve transmission of ballots and votes via telephones, private computer

networks, or the Internet.

Electronic voting technology can speed the counting of ballots and can provide improved

accessibility for disabled voters. However, there has been contention, especially in the United

States, that electronic voting, especially DRE voting, could facilitate electoral fraud.

A direct-recording electronic (DRE) voting machine records votes by means of a ballot display

provided with mechanical or electro-optical components that can be activated by the voter

(typically buttons or a touch screen); that processes data with computer software; and that

records voting data and ballot images in memory components. After the election it produces a

tabulation of the voting data stored in a removable memory component and as printed copy. The

system may also provide a means for transmitting individual ballots or vote totals to a central

location for consolidating and reporting results from precincts at the central location. These

systems use a precinct count method that tabulates ballots at the polling place. They typically

tabulate ballots as they are cast and print the results after the close of polling.

The Indian EVMs are designed and developed by two Government Owned Defense Equipment

Manufacturing Units, Bharat Electronics Limited (BEL) and Electronics Corporation of India

Limited (ECIL). Both systems are identical, and are developed to the specifications of Election

Commission of India. The System is a set of two devices running on 6V batteries. One device,

the Voting Unit is used by the Voter, and another device called the Control Unit is operated by

the Electoral Officer. Both units are connected by a 5 meter cable. The Voting unit has a Blue

Button for every candidate, the unit can hold 16 candidates, but up to 4 units can be chained, to

accommodate 64 candidates. The Control Units has three buttons on the surface, namely, one

button to release a single vote, one button to see the total number of vote cast till now, and one

button to close the election process. The result button is hidden and sealed; it cannot be pressed

unless the Close button is already pressed.

BLOCK DIAGRAM:

Transmitter Section :

Receiver Section:

Power Supply:

Block Diagram Explanation

Here we are using AT89S52 controller. This is used to control all the operations of a circuit to

get the accurate result. There are two sections in this project one, is the transmitter section and

the other is the receiver section.

In transmitter section we interfaced the keypad, LCD and RF transmitter. With the help of

keypad, person will entering the ID (Identification No), these ID’s will be differing from person

to person. The ID entered by the person or the voter will be displayed on the LCD provided in

the transmitter section simultaneously. This password entered by the voter is checked by the

microcontroller of the transmitter section. According to the program written for controller,

controller compares the data in the controller with that data the person has entered. The vote is

counted only if the password entered is correct as checked by the microcontroller. Then the voter

need to type the number alloted to the party which he likes to vote. Assume three parties, x, y

and z. If a switch is pressed a voter will be able to generate a vote to x-party. After dropping the

vote to concern party, it will indicated by buzzer, in the similar way we assign some other keys

to other different parties.

The data from the microcontroller is transferred to the RF transmitter with an encoder of the

transmitter section. The encoder encodes the data and the RF transmitter transmits this encoded

data by using the radio frequency signals. The RF frequency range 3Hz to 330GHz.RF range will

be differing from frequency to frequency. In this project we are using 434MHz RF modules,

Maximum range it will give up to 50 meters or 500feets.

In receiver section we are interfaced with RF receiver, EEPROM(24C02) and LCD .The RF

receiver receives the encoded data and decodes it by using the decoder provided. This data is

then fed to the microcontroller at the receiver section. The voter details i.e. password and the

votes given to the party will be stored in the EEPROM in the receiver section. The LCD of the

receiver section displays the votes of the respective parties. As the polling process takes place,

the votes attained by the parties will be changed on the LCD of the receiver section

simultaneously.

CHAPTER-3

Hardware Explanation

Block Diagram For Power Supply

Figure: Power Supply

Description

Transformer:

A transformer is a device that transfers electrical energy from one circuit to another through

inductively coupled conductors—the transformer's coils. A varying current in the first or primary

winding creates a varying magnetic flux in the transformer's core, and thus a varying magnetic

field through the secondary winding. This varying magnetic field induces a varying

electromotive force (EMF) or "voltage" in the secondary winding. This effect is called mutual

induction.

Figure: Transformer Symbol

(or)

Transformer is a device that converts the one form energy to another form of energy like a

transducer.

Figure: Transformer

Basic Principle:

A transformer makes use of Faraday's law and the ferromagnetic properties of an iron core to

efficiently raise or lower AC voltages. It of course cannot increase power so that if the voltage is

raised, the current is proportionally lowered and vice versa.

Figure: Basic Principle

Transformer Working:

A transformer consists of two coils (often called 'windings') linked by an iron core, as shown in

figure below. There is no electrical connection between the coils; instead they are linked by a

magnetic field created in the core.

Figure: Basic Transformer

Transformers are used to convert electricity from one voltage to another with minimal loss of

power. They only work with AC (alternating current) because they require a changing magnetic

field to be created in their core. Transformers can increase voltage (step-up) as well as reduce

voltage (step-down).

Alternating current flowing in the primary (input) coil creates a continually changing magnetic

field in the iron core. This field also passes through the secondary (output) coil and the changing

strength of the magnetic field induces an alternating voltage in the secondary coil. If the

secondary coil is connected to a load the induced voltage will make an induced current flow. The

correct term for the induced voltage is 'induced electromotive force' which is usually abbreviated

to induced e.m.f.

The iron core is laminated to prevent 'eddy currents' flowing in the core. These are currents

produced by the alternating magnetic field inducing a small voltage in the core, just like that

induced in the secondary coil. Eddy currents waste power by needlessly heating up the core but

they are reduced to a negligible amount by laminating the iron because this increases the

electrical resistance of the core without affecting its magnetic properties.

Transformers have two great advantages over other methods of changing voltage:

1. They provide total electrical isolation between the input and output, so they can be safely

used to reduce the high voltage of the mains supply.

2. Almost no power is wasted in a transformer. They have a high efficiency (power out /

power in) of 95% or more.

Classification of Transformer:

Step-Up Transformer

Step-Down Transformer

Step-Down Transformer:

Step down transformers are designed to reduce electrical voltage. Their primary voltage is

greater than their secondary voltage. This kind of transformer "steps down" the voltage applied

to it. For instance, a step down transformer is needed to use a 110v product in a country with a

220v supply.

Step down transformers convert electrical voltage from one level or phase configuration usually

down to a lower level. They can include features for electrical isolation, power distribution, and

control and instrumentation applications. Step down transformers typically rely on the principle

of magnetic induction between coils to convert voltage and/or current levels.

Step down transformers are made from two or more coils of insulated wire wound around a core

made of iron. When voltage is applied to one coil (frequently called the primary or input) it

magnetizes the iron core, which induces a voltage in the other coil, (frequently called the

secondary or output). The turn’s ratio of the two sets of windings determines the amount of

voltage transformation.

Figure: Step-Down Transformer

An example of this would be: 100 turns on the primary and 50 turns on the secondary, a ratio of 2 to 1.

Step down transformers can be considered nothing more than a voltage ratio device.

With step down transformers the voltage ratio between primary and secondary will mirror the

"turn’s ratio" (except for single phase smaller than 1 kva which have compensated secondary). A

practical application of this 2 to 1 turn’s ratio would be a 480 to 240 voltage step down. Note that

if the input were 440 volts then the output would be 220 volts. The ratio between input and

output voltage will stay constant. Transformers should not be operated at voltages higher than

the nameplate rating, but may be operated at lower voltages than rated. Because of this it is

possible to do some non-standard applications using standard transformers.

Single phase step down transformers 1 kva and larger may also be reverse connected to step-

down or step-up voltages. (Note: single phase step up or step down transformers sized less than 1

KVA should not be reverse connected because the secondary windings have additional turns to

overcome a voltage drop when the load is applied. If reverse connected, the output voltage will

be less than desired.)

Step-Up Transformer:

A step up transformer has more turns of wire on the secondary coil, which makes a larger

induced voltage in the secondary coil. It is called a step up transformer because the voltage

output is larger than the voltage input.

Step-up transformer 110v 220v design is one whose secondary voltage is greater than its primary

voltage. This kind of transformer "steps up" the voltage applied to it. For instance, a step up

transformer is needed to use a 220v product in a country with a 110v supply.

A step up transformer 110v 220v converts alternating current (AC) from one voltage to another

voltage. It has no moving parts and works on a magnetic induction principle; it can be designed

to "step-up" or "step-down" voltage. So a step up transformer increases the voltage and a step

down transformer decreases the voltage.

The primary components for voltage transformation are the step up transformer core and coil.

The insulation is placed between the turns of wire to prevent shorting to one another or to

ground. This is typically comprised of Mylar, nomex, Kraft paper, varnish, or other materials. As

a transformer has no moving parts, it will typically have a life expectancy between 20 and 25

years.

Figure: Step-Up Transformer

Applications:

Generally these Step-Up Transformers are used in industries applications only.

Types of Transformer:

Mains Transformers

Mains transformers are the most common type.  They are designed to reduce the AC mains

supply voltage (230-240V in the UK or 115-120V in some countries) to a safer low voltage.

The standard mains supply voltages are officially 115V and 230V, but 120V and 240V are the

values usually quoted and the difference is of no significance in most cases.

Figure: Main Transformer

To allow for the two supply voltages mains transformers usually have two separate primary coils

(windings) labeled 0-120V and 0-120V. The two coils are connected in series for 240V (figure

2a) and in parallel for 120V (figure 2b). They must be wired the correct way round as shown in

the diagrams because the coils must be connected in the correct sense (direction):

Most mains transformers have two separate secondary coils (e.g. labeled 0-9V, 0-9V) which may

be used separately to give two independent supplies, or connected in series to create a centre-

tapped coil (see below) or one coil with double the voltage.

Some mains transformers have a centre-tap halfway through the secondary coil and they are

labeled 9-0-9V for example. They can be used to produce full-wave rectified DC with just two

   

diodes, unlike a standard secondary coil which requires four diodes to produce full-wave

rectified DC.

A mains transformer is specified by:

1. Its secondary (output) voltages Vs.

2. Its maximum power, Pmax, which the transformer can pass, quoted in VA (volt-amp). This

determines the maximum output (secondary) current, Imax...

...where Vs is the secondary voltage.  If there are two secondary coils the maximum

power should be halved to give the maximum for each coil.

3. Its construction - it may be PCB-mounting, chassis mounting (with solder tag

connections) or toroidal (a high quality design).

Audio Transformers

Audio transformers are used to convert the moderate voltage, low current output of an audio

amplifier to the low voltage, high current required by a loudspeaker.  This use is called

'impedance matching' because it is matching the high impedance output of the amplifier to the

low impedance of the loudspeaker.

Figure: Audio transformer

Radio Transformers

Radio transformers are used in tuning circuits. They are smaller than mains and audio

transformers and they have adjustable ferrite cores made of iron dust. The ferrite cores can be

adjusted with a non-magnetic plastic tool like a small screwdriver. The whole transformer is

enclosed in an aluminum can which acts as a shield, preventing the transformer radiating too

much electrical noise to other parts of the circuit.

Figure: Radio Transformer

Turns Ratio and Voltage

The ratio of the number of turns on the primary and secondary coils determines the ratio of the

voltages...

...where Vp is the primary (input) voltage, Vs is the secondary (output) voltage, Np is the number

of turns on the primary coil, and Ns is the number of turns on the secondary coil.

Diodes

Diodes allow electricity to flow in only one direction.  The arrow of the circuit symbol shows the

direction in which the current can flow.  Diodes are the electrical version of a valve and early

diodes were actually called valves.

Figure: Diode Symbol

A diode is a device which only allows current to flow through it in one direction.  In this

direction, the diode is said to be 'forward-biased' and the only effect on the signal is that there

will be a voltage loss of around 0.7V.  In the opposite direction, the diode is said to be 'reverse-

biased' and no current will flow through it.

Rectifier

The purpose of a rectifier is to convert an AC waveform into a DC waveform (OR) Rectifier

converts AC current or voltages into DC current or voltage.  There are two different rectification

circuits, known as 'half-wave' and 'full-wave' rectifiers.  Both use components called diodes to

convert AC into DC.

The Half-wave Rectifier

The half-wave rectifier is the simplest type of rectifier since it only uses one diode, as shown in

figure.

Figure: Half Wave Rectifier

Figure 2 shows the AC input waveform to this circuit and the resulting output.  As you can see,

when the AC input is positive, the diode is forward-biased and lets the current through.  When

the AC input is negative, the diode is reverse-biased and the diode does not let any current

through, meaning the output is 0V.  Because there is a 0.7V voltage loss across the diode, the

peak output voltage will be 0.7V less than Vs.

Figure: Half-Wave Rectification

While the output of the half-wave rectifier is DC (it is all positive), it would not be suitable as a

power supply for a circuit.  Firstly, the output voltage continually varies between 0V and Vs-

0.7V, and secondly, for half the time there is no output at all. 

The Full-wave Rectifier

The circuit in figure 3 addresses the second of these problems since at no time is the output

voltage 0V.  This time four diodes are arranged so that both the positive and negative parts of the

AC waveform are converted to DC.  The resulting waveform is shown in figure 4.

Figure: Full-Wave Rectifier

Figure: Full-Wave Rectification

When the AC input is positive, diodes A and B are forward-biased, while diodes C and D are

reverse-biased.  When the AC input is negative, the opposite is true - diodes C and D are

forward-biased, while diodes A and B are reverse-biased.

While the full-wave rectifier is an improvement on the half-wave rectifier, its output still isn't

suitable as a power supply for most circuits since the output voltage still varies between 0V and

Vs-1.4V.  So, if you put 12V AC in, you will 10.6V DC out.

Capacitor Filter

The capacitor-input filter, also called "Pi" filter due to its shape that looks like the Greek letter

pi, is a type of electronic filter. Filter circuits are used to remove unwanted or undesired

frequencies from a signal.

Figure: Capacitor Filter

A typical capacitor input filter consists of a filter capacitor C1, connected across the rectifier

output, an inductor L, in series and another filter capacitor connected across the load.

1. The capacitor C1 offers low reactance to the AC component of the rectifier output while

it offers infinite reactance to the DC component. As a result the capacitor shunts an

appreciable amount of the AC component while the DC component continues its journey

to the inductor L

2. The inductor L offers high reactance to the AC component but it offers almost zero

reactance to the DC component. As a result the DC component flows through the

inductor while the AC component is blocked.

3. The capacitor C2 bypasses the AC component which the inductor had failed to block. As

a result only the DC component appears across the load RL.

Figure: Centered Tapped Full-Wave Rectifier with a Capacitor Filter

Voltage Regulator:

A voltage regulator is an electrical regulator designed to automatically maintain a constant

voltage level. It may use an electromechanical mechanism, or passive or active electronic

components. Depending on the design, it may be used to regulate one or more AC or DC

voltages. There are two types of regulator are they.

Positive Voltage Series (78xx) and

Negative Voltage Series (79xx)

78xx:

’78’ indicate the positive series and ‘xx’indicates the voltage rating. Suppose 7805 produces

the maximum 5V.’05’indicates the regulator output is 5V.

79xx:

’78’ indicate the negative series and ‘xx’indicates the voltage rating. Suppose 7905

produces the maximum -5V.’05’indicates the regulator output is -5V.

These regulators consists the three pins there are

Pin1: It is used for input pin.

Pin2: This is ground pin for regulator

Pin3: It is used for output pin. Through this pin we get the output.

Figure: Regulator

Features:

Output Current of 1.5A

Output Voltage Tolerance of 5%

Internal thermal overload protection

Internal Short-Circuit Limited

No External Component

Output Voltage 5.0V, 6V, 8V, 9V, 10V, 12V, 15V, 18V, 24V

Offer in plastic TO-252, TO-220 & TO-263

Direct Replacement for LM78XX

CHAPTER-4

Microcontroller (AT89S52)

Description of Microcontroller 89S52:

The AT89S52 is a low-power, high-performance CMOS 8-bit micro controller with

8Kbytes of in-system programmable flash memory. The device is manufactured Atmel’s high-

density nonvolatile memory technology and is compatible with the industry-standard 80C51

micro controller. The on-chip Flash allows the program memory to be reprogrammed in-system

or by a conventional nonvolatile memory programmer. By combining a versatile 8-bit CPU with

in-system programmable flash one monolithic http; the Atmel AT89S52 is a powerful micro

controller, which provides a highly flexible and cost effective solution to any cost effective

solution to any embedded control applications to any embedded control applications.

The AT89S52 provides the following standard features: 8K bytes of Flash, 256 bytes of

RAM, 32 I/O lines, Watchdog timer, two data pointers, three 16-bit timer/counters, full duplex

serial port, on-chip oscillator, and clock circuitry. In addition, the AT89S52 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 interrupt or hardware

reset.

Architecture of 8052µC:

Figure: Microcontroller Architecture

Features:

• Compatible with MCS-51 Products

• 8K Bytes of In-System Programmable (ISP) Flash Memory

– Endurance: 1000 Write/Erase Cycles

• 4.0V to 5.5V Operating Range

• Fully Static Operation: 0 Hz to 33 MHz

• Three-level Program Memory Lock

• 256K Internal RAM

• 32 Programmable I/O Lines

• 3 16-bit Timer/Counters

• Eight Interrupt Sources

• Full Duplex UART Serial Channel

• Low-power Idle and Power-down Modes

• Interrupt Recovery from Power-down Mode

• Watchdog Timer

• Dual Data Pointer

• Power-off Flag

Pin Diagram:

Pin Description:

VCC 40

Supply voltage.

GND 20

Ground.

Port 0 (32-39):

Port 0 is an 8-bit open drain bi-directional I/O port. As an output port, each pin can sink

eight TTL inputs. When 1s are written to port 0 pins, the pins can be used as high impedance

inputs. Port 0 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 program verification

Port 1 (1-8):

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

sink/source four TTL inputs. When 1s are written to Port 1 pins, they are pulled high by the

internal pull-ups and can be used as inputs. 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 trigger input P1.1/T2EX),

respectively, as shown in the following table. Port 1 also receives the low-order address bytes

during Flash programming and verification.

Port 2 (21-28):

Port 2 is an 8-bit bi-directional I/O port with internal pull-ups. The Port 2 output buffers can

sink/source four TTL inputs. When 1s are written to Port 2 pins, they are pulled high by the

internal pull-ups and can be used as inputs. Port 2 emits the high-order address byte during

fetches from external program memory and during accesses to external data memory that uses

16-bit addresses (MOVX @DPTR). In this application, Port 2 uses strong internal pull-ups when

emitting 1s. During accesses to external data memory that use 8-bit addresses (MOVX @ RI),

Port 2emits the contents of the P2 Special Function Register. Port 2 also receives the high-order

address bits and some control signals during Flash programming and verification

Port 3 (10-17):

Port 3 is an 8-bit bi-directional I/O port with internal pull-ups. The Port 3 output buffers can

sink/source four TTL inputs. When 1s are writ 1s are written to Port 3 pins, they are pulled high

by the internal pull-ups and can be used as inputs. As inputs, Port 3 pins that are externally being

pulled low will source current (IIL) because of the pull-ups. Port 3 also serves the functions of

various special features of the AT89S52, as shown in the following table.

Port 3 also receives some control signals for Flash programming and verification.

RST

Reset input. A high on this pin for two machine cycles while the oscillator is running resets

the device.

ALE/PROG

Address Latch Enable (ALE) is an output pulse for latching the low byte of the address

during accesses to external memory. This pin is also the program pulse input (PROG) during

Flash programming. In normal operation, ALE is emitted at a constant rate of1/6 the oscillator

frequency and may be used for external timing or clocking purposes. Note, however, that one

ALE pulse is skipped during each access to external data Memory. If desired, ALE operation can

be disabled by setting bit 0 of SFR location 8EH. With the bit set, ALE is active only during a

MOVX or MOVC instruction. Otherwise, the pin is weakly pulled high. Setting the ALE-disable

bit has no effect if the micro controller is in external execution mode.

PSEN

Program Store Enable (PSEN) is the read strobe to external program memory. When the

AT89S52 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.

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. A should be

strapped to VCC for internal program executions. This pin also receives the 12-voltProgramming

enables voltage (VPP) during Flash programming.

XTAL1:

Input to the inverting oscillator amplifier and input to the internal clock operating circuit.

XTAL2:

Output from the inverting oscillator amplifier.

Oscillator Characteristics:

XTAL1 and XTAL2 are the input and output, respectively, of an inverting amplifier that

can be configured for use as an on-chip oscillator, as shown in Figure 1. Either a quartz crystal or

ceramic resonator may be used. To drive the device from an External clock source, XTAL2

should be left unconnected while XTAL1 is driven.

Fig: Oscillator Connections

Special Function Register (SFR) Memory:

Special Function Registers (SFR s) are areas of memory that control specific

functionality of the 8051 processor. For example, four SFRs permit access to the 8051’s 32

input/output lines. Another SFR allows the user to set the serial baud rate, control and access

timers, and configure the 8051’s interrupt system.

Accumulator: The Accumulator, as its name suggests is used as a general register to

accumulate the results of a large number of instructions. It can hold 8-bit (1-byte) value and is

the most versatile register.

The “R” registers: The “R” registers are a set of eight registers that are named R0, R1.

etc. up to R7. These registers are used as auxiliary registers in many operations.

The “B” registers: The “B” register is very similar to the accumulator in the sense that it may

hold an 8-bit (1-byte) value. Two only uses the “B” register 8051 instructions: MUL AB and

DIV AB.

Data Pointer:

The Data pointer (DPTR) is the 8051’s only user accessible 16-bit (2Bytes) register. The

accumulator, “R” registers are all 1-Byte values. DPTR, as the name suggests, is used to point to

data. It is used by a number of commands, which allow the 8051 to access external memory.

Programs counter & Stack pointer:

The program counter (PC) is a 2-byte address, which tells the 8051 where the next

instruction to execute is found in memory. The stack pointer like all registers except DPTR and

PC may hold an 8-bit (1-Byte) value.

Memory:

Special Function Registers (SFRs) are areas of memory that control specific functionality of

the 8051 processor. For example, four SFRs permit access to the 8051’s 32 input/output lines.

Another SFR allows the user to set the serial baud rate, control and access timers, and configure

the 8051’s interrupt system.

Interrupt Registers:

The individual interrupt enable bits are in the IE register . Two priorities can be

set for each of the six interrupt sources in the IP register.

Timer 0:

Timer 0 functions as either a timer or event counter in four modes of operation .

Timer 0 is controlled by the four lower bits of the TMOD register and bits 0, 1, 4 and 5

of the TCON register. Mode 0 ( 13-bit Timer) Mode 0 configures timer 0 as a 13-bit

timer which is set up as an 8-bit timer (TH0 register) with a modulo 32 pre-scale

implemented with the lower five bits of the TL0 register . The upper three bits of TL0

register are indeterminate and should be ignored. Pre-scale overflow increments the

TH0 register. Mode 1 ( 16-bit Timer )Mode 1 is the same as Mode 0, except that the

Timer register is being run with all 16 bits .

Mode 1 configures timer 0 as a 16-bit timer with the TH0 and TL0 registers

connected in cascade. The selected input increments the TL0 register. Mode 2 (8-bit

Timer with Auto-Reload)Mode 2 configures timer 0 as an 8-bit timer ( TL0 register )

that automatically reloads from the TH0 register . TL0 overflow sets TF0 flag in the

TCON register and reloads TL0 with the contents of TH0, which is preset by

software. Mode 3 ( Two 8-bit Timers )Mode 3 configures timer 0 so that registers TL0

and TH0 operate as separate 8-bit timers. This mode is provided for applications requiring

an additional 8-bit timer or counter.

Timer 1:

Timer 1 is identical to timer 0, except for mode 3, which is a hold-count mode. Mode 3

(Halt) Placing Timer 1 in mode 3 causes it to halt and hold its count. This can be

used to halt Timer 1 when TR1 run control bit is not available i.e., when Timer 0 is

in mode 3.

Baud Rates:

The baud rate in Mode 0 is fixed. The baud rate in Mode 2 depends on the value

of bit SMOD in Special Function Register PCON. If SMOD = 0 (which is its value on

reset), the baud rate is 1/64 the oscillator frequency. If SMOD = 1, the baud rate is

1/32 the oscillator frequency. In the 89S52, the baud rates in Modes 1 and 3 are

determined by the Timer 1 overflow rate. In case of Timer 2 , these baud rates can

be determined by Timer 1 , or by Timer 2 , or by both (one for transmit and the other for

receive ).

TCON REGISTER: Timer/counter Control Register

7 6 5 4 3 2 1 0

TF1 TR1 TF0 TR0 IE1 IT1 IE0 IT0

Bit

Number

Bit

Mnemonics

Description

7 TF1 Timer 1 overflow flag

Cleared by hardware when processor vectors to interrupt routien.

Set by hardware on timer/counter overflow, when the imer 1 register overflows.

6 TR1 Timer 1 run control bit

Clear to turn off timer/counter 1.

Set to turn on timer/counter 1.

5 TF0 Timer 1 overflow flag

Cleared by hardware when processor vectors to interrupt routien.

Set by hardware on timer/counter overflow, when the timer0 register overflows.

4 TR0 Timer 1 run control bit

Clear to turn off timer/counter 0.

Set to turn on timer/counter 0.

3 IE1 Interrupt 1 Edge flag

Cleared by hardware when interrupt is processed if edge-triggered (IT1)

Set by hardware when external interrupt is detected on INT1 pin.

2 IT1 Interrupt 1 type control bit

Clear to select low level active (level triggered) for external interrupt 1.

Set to select falling edge active (edge triggered) for external interrupt 1.

1 IE0 Interrupt 0 Edge flag

Cleared by hardware when interrupt is processed if edge-triggered (IT0)

Set by hardware when external interrupt is detected on INT0 pin.

0 IT0 Interrupt 0 type control bit

Clear to select low level active (level triggered) for external interrupt 0.

Set to select falling edge active (edge triggered) for external interrupt 0.

TMOD REGISTER: Timer/Counter 0 and 1 Modes

7 6 5 4

3 2 1 0

GATE1 C/T 1 M11 M01 GATE0 C/T 0 M10 M00

Bit

Number

Bit Mnemonics Description

7 GATE1Timer 1 Gate Control Bit

Clear to enable timer 1 whenever the TR1 bit is set.

Set to enable timer 1 only while the INT1 pin is high & TR1 bit is set.

6 C/T 1Timer1 counter/timer select bit

Clear for timer operation: timer1 counts the divided down system

clock.

Set for counter operation: timer1 counts negative transition on external

pin T1.

5 M11Timer 1 mode select bits

M11 M01 operating mode

0 0 Mode0: 8 bit timer/counter (TH1) with 5 bit

prescaler (TL1).

0 1 Mode1: 16 bit timer/counter.

1 0 Mode2: 8 bit auto reload timer/counter (TL1).

1 1 Mode3: timer 1 halted. Retains count.

4 M01

3 GATE 0Timer 0 Gate Control Bit

Clear to enable timer 0 whenever the TR0 bit is set.

Set to enable timer 0 only while the INT0 pin is high & TR0 bit is set.

2 C/T 0Timer0 counter/timer select bit

Clear for timer operation: timer0 counts the divided down system

clock.

Set for counter operation: timer0 counts negative transition on external

pin T0.

1 M10Timer 0 mode select bits

M10 M00 operating mode

1 0 Mode0: 8 bit timer/counter (TH1) with 5 bit

pre-scaler (TL1).

0 1 Mode1: 16 bit timer/counter.

1 0 Mode2: 8 bit auto reload timer/counter (TL1).

1 1 Mode3: timer 1 halted. Retains count.

TH0 is an 8 bit timer using timer1’s TR0 & TF0 bits.

CHAPTER-5

What is a Communication?

Communication is a process of transferring information from one entity to another.

Communication processes are sign-mediated interactions between at least two agents which

share a repertoire of signs and semiotic rules. Communication is commonly defined as "the

imparting or interchange of thoughts, opinions, or information by speech, writing, or signs".

Communication is a process whereby information is enclosed in a package and is channeled

and imparted by a sender to a receiver via some medium. The receiver then decodes the message

and gives the sender a feedback. All forms of communication require a sender, a message, and an

intended recipient; however the receiver need not be present or aware of the sender's intent to

communicate at the time of communication in order for the act of communication to occur.

Communication requires that all parties have an area of communicative commonality. There are

auditory means, such as speech, song, and tone of voice, and there are nonverbal means, such as

body language, sign language, paralanguage, touch, eye contact, through media, i.e., pictures,

graphics and sound, and writing

Figure: Transactional Model of Communication

Communication System

Communications system is a collection of individual communications networks, transmission

systems, relay stations, tributary stations, and data terminal equipment (DTE) usually capable of

interconnection and interoperation to form an integrated whole. The components of a

communications system serve a common purpose, are technically compatible, use common

procedures, respond to controls, and operate in unison. Telecommunications is a method of

communication (e.g., for sports broadcasting, mass media, journalism, etc.).

Figure: Block Diagram for Communication System

Examples: Radio Communication System

A radio communication system is composed of several communications subsystems that give

exterior communications capabilities. A radio communication system comprises a transmitting

conductor in which electrical oscillations or currents are produced and which is arranged to cause

such currents or oscillations to be propagated through the free space medium from one point to

another remote there from and a receiving conductor at such distant point adapted to be excited

by the oscillations or currents propagated from the transmitter.

RF Communication:

Every system is automated in order to face new challenges in the present day situation.

Automated systems have less manual operations, so that the flexibility, reliabilities are high and

accurate. Hence every field prefers automated control systems. Especially in the field of

electronics automated systems are doing better performance. Any automated system will work

effectively if it access wirelessly. Here in this project we are going to use RF communication for

remote accessing of automated system. Probably the most useful thing to know about the RF

communication is that it is an international standard communication.

RF communication works by creating electromagnetic waves at a source and being able to pick

up those electromagnetic waves at a particular destination. These electromagnetic waves travel

through the air at near the speed of light. The wavelength of an electromagnetic signal is

inversely proportional to the frequency; the higher the frequency, the shorter the wavelength.

RF Transmitter

RF Link Transmitter - 434MHz

Description:

This is only the 434MHz transmitter. This will work with the RF Links at 434MHz at either baud

rate. Only one 434MHz transmitter will work within the same location.

This wireless data is the easiest to use, lowest cost RF link we have ever seen! Use these

components to transmit position data, temperature data, even current program register values

wirelessly to the receiver. These modules have up to 500 ft range in open space. The transmitter

operates from 2-12V. The higher the Voltage, the greater the range - see range test data in the

documents section.

We have used these modules extensively and have been very impressed with their ease of use

and direct interface to an MCU. The theory of operation is very simple. What the transmitter

'sees' on its data pin is what the receiver outputs on its data pin. If you can configure the UART

module on a PIC, you have an instant wireless data connection. The typical range is 500ft for

open area. This is an ASK transmitter module with an output of up to 8mW depending on power

supply voltage. The transmitter is based on SAW resonator and accepts digital inputs, can

operate from 2 to 12 Volts-DC, and makes building RF enabled products very easy.

Figure: RF Transmitter

RF Receiver

RF Link 4800bps Receiver - 434MHz

Description:

Sold as a receiver only. This receiver type is good for data rates up to 4800bps and will only

work with the 434MHz transmitter. Multiple 434MHz receivers can listen to one 434MHz

transmitter.

This wireless data is the easiest to use, lowest cost RF link we have ever seen! Use these

components to transmit position data, temperature data, and even current program register values

wirelessly to the receiver. These modules have up to 500 ft range in open space. The receiver is

operated at 5V.

We have used these modules extensively and have been very impressed with their ease of use

and direct interface to an MCU. The theory of operation is very simple. What the transmitter

'sees' on its data pin is what the receiver outputs on its data pin. If you can configure the UART

module on a PIC, you have an instant wireless data connection. Data rates are limited to

4800bps. The typical range is 500ft for open area.

This receiver has a sensitivity of 3uV. It operates from 4.5 to 5.5 volts-DC and has digital output.

The typical sensitivity is -103dbm and the typical current consumption is 3.5mA for 5V

operation voltage.

Figure:RF Receiver

Features:

434 MHz Operation

500 Ft. Range - Dependent on Transmitter Power Supply

4800 bps transfer rate

Low cost

Extremely small and light weight

Encoder (HT12E)

General Description:

The 212 encoders are a series of CMOS LSIs for remote control system applications. They are

capable of encoding information which consists of N address bits and 12-N data bits. Each

address / data input can be set to one of the two logic states. The programmed addresses/data are

transmitted together with the header bits via an RF or an infrared transmission medium upon

receipt of a trigger signal. The capability to select a TE trigger on the HT12E or a DATA trigger

on the HT12A further enhances the application flexibility of the 212 series of encoders. The

HT12A additionally provides a 38 kHz carrier for infrared systems.

Features:

18 pin DIP

Operating voltage is 2.4V ~ 12V

Low power and high noise immunity CMOS technology

Low standby current: 0.1µA (typ.) at VDD = 5V

Minimum transmission four words for the HT12E

Built in oscillator needs only 5% resistor

Data code has positive polarity

Minimal external component

Functional Description:

Operation:

The 212 series of encoders begin a 4 word transmission cycle upon receipt of a

transmission enable. This cycle will repeat itself as long as the transmission enable is held low.

Once the transmissions enable returns high the encoder output completes its final cycle and then

stops as shown below.

Address/Data waveform:

Each programmable address/data pin can be externally set to one the following two logic states

as shown below.

Address/data programming (preset):

The status of each address/data pin can be individually pre-set to logic “high” or “low”. If a

transmission enable signal is applied, the encoder scans and transmits the status of the 12 bits of

address/data serially in the order A0 to AD11 for the HT12E encoder.

During information transmission these bits are transmitted with a preceding synchronization bit.

If the trigger signal is not applied, the chip enters the standby mode and consumes a reduced

current of less than 1µA for a supply voltage of 5V.

Usual information preset the address pins with individual security codes using DIP switches or

PCB wiring, while the data is selected by push buttons or electronic switches.

Address/Data sequence:

The following provides the address/data sequence table for various models of the 212 series of

encoders. The correct device should be selected according to the individual address and data

requirements.

HT12E

Address/Data Bits

0 1 2 3 4 5 6 7 8 9 10 11

A0 A1 A2 A3 A4 A5 A6 A7 A8 A9 A10 A11

Transmission Enable:

For the HT12E encoders, transmission is enabled by applying a low signal to the TE pin.

Pin Diagram:

HT12E

Pin Description:

A0-A7

These are the input pins for address A0 – A7. These pins can be externally set to Vss or

left open.

Dout

This pin is encoder data serial transmission out pin.

TE

It’s a transmission enable pin and it’s a active low pin.

OSC1

Oscillator input pin.

OSC2

Oscillator output pin.

Vss

Ground pin.

Vdd

Power supply pin.

Absolute Maximum Ratings:

Supply voltage…………………-0.3V to 13V

Input voltage……………………Vss -0.3V t Vdd +03V

Storage a Temperature….. -500C to 1250C

Operating Temperature….. -200C to 750C

Decoder (HT12D):

General Description:

The 212 decoders are a series of CMOS LSIs for remote control system applications. They are

paired with 212 series of encoder. For proper operation, a pair of encoder/decoder with the same

number of address and data format should be chosen.

The decoders receive serial address and data from a programmed 212 series of encoders that are

transmitted by a carrier using an RF or an IR transmission medium. They compare the serial

input data three times continuously with their local addresses. If no error or unmatched codes are

found, the input data codes are decoded and then transferred to the output pins. The VT pin also

goes high to indicate a valid transmission.

The 212 series of decoders are capable of decoding information that consists of N bits of address

and 12-N bits of data. Of this series, the HT12D is arranged to provide 8 address bits and 4 data

bits.

Features:

18 pin DIP

Operating voltage 2.4V ~ 12V

Low power and high noise immunity CMOS technology

Low standby current

Capable of decoding 12 bits of information

Binary address setting

Received codes are checked 3 times

Address/Data number combination is 8 address bits and 4 data bits

Built in oscillator needs only 5% resistor

Valid transmission indicator

Easy interface with an RF or an infrared transmission medium

Minimal external components

Pair with 212 series of encoders

Functional Description:

Operation:

The 212 series of decoders provides various combinations of addresses and data pins in different

packages so as to pair with the 212 series of encoders.

The decoders recevie data that are transmitted by an encoder and inerpret the first N bits of code

period as addresses and the last 12-N bits as data, where N is the address code number. A signal

on the DIN pin actives the oscillator which in turn decodes the incoming address and data. The

decoders will then check the recevied address three times continuously. If the recevied address

codes all match the contents of the decoders local address, the 12-N bits of data are decoded to

activate the output pins and the VT pin is set high to indicate a valid transmission. This will last

unless the address code is incorrect or no signal is recevied.

The output of the VT pin is high only when the transmission is valid. Otherwise it is always low.

Pin Diagram:

Pin Description:

A0 - A7

These are the input pins for address A0-A7 setting. These pins can be externally set to

Vss or left open.

D8 – D11

These are the output data pins, power on state is low.

Din

It is a serial data input pin.

VT

Valid transmission, active high pin.

OSC1

Oscillator input pin

OSC2

Oscillator output pin

Vss

Ground pin

Vdd

Power supply

Absolute Maximum Ratings:

Supply voltage…….. -0.3V to 13V

Input voltage………. Vss -0.3V to Vdd +0.3V

Storage Temperature……. -500C to 1250C

Applications:

Burglar alarm, smoke alarm, fire alarm, car alarm, security system

Garage door and car door controllers

Cordless telephone

EEPROM:

DESCRIPTION:

The AT24C01A/02/04/08A/16A provides 1024/2048/4096/8192/16384 bits of serial electrically

erasable and programmable read-only memory (EEPROM) organized as 128/256/512/1024/2048

words of 8 bits each. The device is optimized for use in many automotive applications where

low-power and low-voltage operation are essential.

The AT24C01A/02/04/08A/16A is available in space-saving 8-lead PDIP, 8-lead JEDEC SOIC,

and 8-lead TSSOP packages and is accessed via a two-wire serial interface. In addition, the

entire family is available in 2.7V (2.7V to 5.5V) versions.

FEATURES:

Medium-voltage and Standard-voltage Operation

– 5.0 (VCC = 4.5V to 5.5V)

– 2.7 (VCC = 2.7V to 5.5V)

Automotive Temperature Range –40°C to 125°C

Internally Organized 128 x 8 (1K), 256 x 8 (2K), 512 x 8 (4K), 1024 x 8 (8K) or 2048 x

8 (16K)

Two-wire Serial Interface

Schmitt Trigger, Filtered Inputs for Noise Suppression

Bidirectional Data Transfer Protocol

400 kHz (2.7V) Compatibility

Write Protect Pin for Hardware Data Protection

8-byte Page (1K, 2K), 16-byte Page (4K, 8K, 16K) Write Modes

Self-timed Write Cycle (5 ms max)

High-reliability

– Endurance: 1 Million Write Cycles

– Data Retention: 100 Years

DEVICE OPERATION:

CLOCK and DATA TRANSITIONS:

The SDA pin is normally pulled high with an external device. Data on the SDA pin may change

only during SCL low time periods. Data changes during SCL high periods will indicate a start or

stop condition as defined below.

Start Condition:

A high-to-low transition of SDA with SCL high is a start condition which must precede any

other command.

Stop Condition:

A low-to-high transition of SDA with SCL high is a stop condition. After a read sequence, the

stop command will place the EEPROM in a standby power mode.

Acknowledgement:

All addresses and data words are serially transmitted to and from the EEPROM in 8-bit words.

The EEPROM sends a “0” to acknowledge that it has received each word. This happens during

the ninth clock cycle.

Standby Mode:

The AT24C01A/02/04/08A/16A features a low-power standby mode which is enabled: (a) upon

power-up and (b) after the receipt of the STOP bit and the completion of any internal operations.

DEVICE ADDRESSING:

The 1K, 2K, 4K, 8K and 16K EEPROM devices all require an 8-bit device address word

following a start condition to enable the chip for a read or write operation. The device address

word consists of a mandatory “1”, “0” sequence for the first four most significant bits. This is

common to all the Serial EEPROM devices. The next 3 bits are the A2, A1 and A0 device

address bits for the 1K/2K EEPROM. These 3 bits must compare to their corresponding

hardwired input pins.

The 4K EEPROM only uses the A2 and A1 device address bits with the third bit being a memory

page address bit. The two device address bits must compare to their corresponding hardwired

input pins. The A0 pin is not connected.

The 8K EEPROM only uses the A2 device address bit with the next two bits being for memory

page addressing. The A2 bit must compare to its corresponding hardwired input pin. The A1 and

A0 pins are not connected.

The 16K does not use any device address bits but instead the three bits are used for memory page

addressing. These page addressing bits on the 4K, 8K and 16K devices should be considered the

most significant bits of the data word address which follows. The A0, A1 and A2 pins are no

connected. The eighth bit of the device address is the read/write operation select bit. A read

operation is initiated if this bit is high and a write operation is initiated if this bit is low. Upon

comparison of the device address, the EEPROM will output a “0”. If a comparison is not made,

the chip will return to a standby state.

WRITE OPERATIONS:

Byte Write:

A write operation requires an 8-bit data word address following the device address word and

acknowledgment. Upon receipt of this address, the EEPROM will again respond with a “0” and

then clock in the first 8-bit data word. Following the receipt of the 8-bit data word, the EEPROM

will output a “0” and the addressing device, such as a microcontroller, must terminate the write

sequence with a stop condition. At this time the EEPROM enters an internally timed write cycle

tWR, to the nonvolatile memory. All inputs are disabled during this write cycle and the

EEPROM will not respond until the write is complete.

Page Write:

The 1K/2K EEPROM is capable of an 8-byte page write, and the 4K, 8K and 16K devices are

capable of 16-byte page writes. A page write is initiated the same as a byte write, but the

microcontroller does not send a stop condition after the first data word is clocked in. Instead,

after the EEPROM acknowledges receipt of the first data word, the microcontroller can transmit

up to seven (1K/2K) or fifteen (4K, 8K, 16K) more data words. The EEPROM will respond with

a “0” after each data word received. The microcontroller must terminate the page write sequence

with a stop condition

The data word address lower three (1K/2K) or four (4K, 8K, 16K) bits are internally incremented

following the receipt of each data word. The higher data word address bits are not incremented,

retaining the memory page row location. When the word address, internally generated, reaches

the page boundary, the following byte is placed at the beginning of the same page. If more than

eight (1K/2K) or sixteen (4K, 8K, 16K) data words are transmitted to the EEPROM, the data

word address will “roll over” and previous data will be overwritten.

Page write

Acknowledge Polling:

Once the internally timed write cycle has started and the EEPROM inputs are disabled,

acknowledge polling can be initiated. This involves sending a start condition followed by the

device address word. The read/write bit is representative of the operation desired. Only if the

internal write cycle has completed will the EEPROM respond with a “0”, allowing the read or

write sequence to continue.

READ OPERATIONS:

Read operations are initiated the same way as write operations with the exception that the

read/write select bit in the device address word is set to “1”. There are three read operations:

current address read, random address read and sequential read.

Current address read:

The internal data word address counter maintains the last address accessed during the last read or

write operation, incremented by one. This address stays valid between operations as long as the

chip power is maintained. The address “roll over” during read is from the last byte of the last

memory page to the first byte of the first page. The address “roll over” during write is from the

last byte of the current page to the first byte of the same page. Once the device address with the

read/write select bit set to “1” is clocked in and acknowledged by the EEPROM, the current

address data word is serially clocked out. The microcontroller does not respond with an input “0”

but does generate a following stop condition.

Random read:

A random read requires a “dummy” byte write sequence to load in the data word address. Once

the device address word and data word address are clocked in and acknowledged by the

EEPROM, the microcontroller must generate another start condition. The microcontroller now

initiates a current address read by sending a device address with the read/write select bit high.

The EEPROM acknowledges the device address and serially clocks out the data word. The

microcontroller does not respond with a “0” but does generate a following stop condition.

Sequential Read:

Sequential reads are initiated by either a current address read or a random address read. After the

microcontroller receives a data word, it responds with an acknowledgement. As long as the

EEPROM receives an acknowledgement, it will continue to increment the data word address and

serially clock out sequential data words. When the memory address limit is reached, the data

word address will “roll over” and the sequential read will continue. The sequential read operation

is terminated when the microcontroller does not respond with a “0” but does generate a

following stop condition.

BUS TIMINGS:

WRITE CYCLE TIMINGS:

START AND STOP DEFINITION:

PIN DIAGRAM:

Figure: Pin Diagram Figure: Pin Function

PIN DESCRIPTION:

Serial Clock (SCL):

The SCL input uses positive edge clock to send data into each EEPROM device and negative

edge clock to bring data out of each device.

Serial Data (SDA):

The SDA pin is bi-directional for serial data transfer. This pin is open-drain driven and may be

wire-O Red with any number of other open-drain or open collector devices.

Device/Page Address (A2, A1 and A0):

The A2, A1 and A0 pins are device address inputs that are hard wired for the AT24C01A and the

AT24C02. As many as eight 1K/2K devices may be addressed on a single bus system. The

AT24C04 uses the A2 and A1 inputs for hard wire addressing and a total of four 4K devices may

be addressed on a single bus system. The A0 pin is not connected. The AT24C08A only uses the

A2 input for hardwire addressing and a total of two 8K devices may be addressed on a single bus

system. The A0 and A1 pins are not connected. The AT24C16A does not use the device address

pins, which limits the number of devices on a single bus to one. The A0, A1 and A2 pins are not

connected.

Write Protect (WP):

The AT24C01A/02/04/08A/16A has a Write Protect pin that provides hardware data protection.

The Write Protect pin allows normal read/write operations when connected to ground (GND).

When the Write Protect pin is connected to VCC, the write protection feature is enabled and

operated as shown in the table.

MEMORY ORGANISATION:

AT24C01A, 1K SERIAL EEPROM:

Internally organized with 16 pages of 8 bytes each, the 1K requires a 7-bit data word address for random word addressing.

AT24C02, 2K SERIAL EEPROM:

Internally organized with 32 pages of 8 bytes each, the 2K requires an 8-bit data word address

for random word addressing.

AT24C04, 4K SERIAL EEPROM:

Internally organized with 32 pages of 16 bytes each, the 4K requires a 9-bit data word address

for random word addressing.

AT24C08A, 8K SERIAL EEPROM:

Internally organized with 64 pages of 16 bytes each, the 8K requires a 10-bit data word address

for random word addressing.

AT24C16A, 16K SERIAL EEPROM:

Internally organized with 128 pages of 16 bytes each, the 16K requires an 11-bit data word

address for random word addressing.

INTERFACING AT24C16A SERIAL EEPROM WITH AT89C51 MICRO

CONTROLLER:

Serial memory devices offer significant advantages over parallel devices in applications where

lower data transfer rates are acceptable. In addition to requiring less board space, serial devices

allow microcontroller I/O pins to be conserved. This is especially valuable when adding external

memory to low-pin count microcontrollers such as AT89C2051 and AT89C4051.

This application note presents a suite of software routines which may be incorporated into a

user’s application to allow an AT89CX051 microcontroller to read and write AT24C16A serial

EEPROM. The software supports all members of the AT24CXX family, and may easily be

modified for compatibility with any of the Atmel 8051-code compatible microcontrollers.

Hardware:

A typical interconnection between an AT89C51 microcontroller and an AT24C16A serial

EEPROM may share the bus, up to eight members of the AT24CXX family utilizing the same

two microcontroller I/O pins. Each device on the bus must have its address inputs (A0, A1 and

A2) hard-wired to a unique address. The first device recognizes address zero (A0, A1, A2 tied

low), while the eighth recognizes address seven (A0, A1, A2 tied high). Not all members of the

AT24CXX family recognize all 3 address inputs, limiting the number of some devices which

may be present to less than eight.

Bi-directional Data Transfer Protocol:

The Bi-directional Data Transfer Protocol utilized by the AT24CXX family allows a number of

compatible devices to share a common 2-wire bus. The bus consists of a serial clock (SCL) line

and a serial data (SDA) line. The clock is generated by the bus master and data is transmitted

serially on the data line, most significant bit first, synchronized to the clock. The protocol

supports bi-directional data transfers in 8-bit bytes. In this application, the microcontroller serves

as the bus master, initiating all data transfers and generating the clock which regulates the flow

of data. The serial devices present on the bus are considered slaves, accepting or sending data in

response to orders from the master. The bus master initiates a data transfer by generating a start

condition on the bus. This is followed by transmission of a byte containing the device address of

the intended recipient. The device address consists of a 4-bit fixed portion and a 3-bit

programmable portion. The fixed portion must match the value hard-wired into the slave, while

the programmable portion allows the master to select between a maximum of eight slaves of

similar type on the bus. The AT24C16A serial EEPROM responds to device addresses with a

fixed portion equal to “1010” and a programmable portion matching the address inputs (A0, A1

and A2).

KEYPAD (matrix):

A keypad is a set of buttons arranged in a block or "pad" which usually bear digits and other

symbols and usually a complete set of alphabetical letters. If it mostly contains numbers then it

can also be called a numeric keypad.

Keypads are found on many alphanumeric keyboards and on other devices such as calculators,

push-button telephones, combination locks, and digital door locks, which require mainly numeric

input. In keypad we have keys arrays in which keys can be arranged in different combinations

and the matrix keypad in which keys are arrange in a particular rows and columns.

Figure: matrix keypad on PCB board.

CONSTRUCTING A MATRIX KEYPAD:

Construction of a keypad is really simple. As per the outline shown in the figure below we have

four rows and four columns. In between each overlapping row and column line there is a key.

So keeping this outline we can construct a keypad using simple SPST Switches as shown below:

Figure: Internal Key Connections SCANNING A MATRIX KEYPAD:

There are many methods depending on how you connect your keypad with your controller, but

the basic logic is same. We make the columns as i/p and we drive the rows making them o/p, this

whole procedure of reading the keyboard is called scanning.

In order to detect which key is pressed from the matrix, we make row lines low one by one and

read the columns. Let’s say we first make Row1 low, and then read the columns. If any of the

key in row1 is pressed will make the corresponding column as low i.e. if second key is pressed in

Row1, then column2 will give low. So we come to know that key 2 of Row1 is pressed. This is

how scanning is done.

So to scan the keypad completely, we need to make rows low one by one and read the columns.

If any of the buttons is pressed in a row, it will take the corresponding column to a low state

which tells us that a key is pressed in that row. If button 1 of a row is pressed then Column 1 will

become low, if button 2 then column2 and so on...

SCHEMATIC :

Figure: keypad arrangement

The internal arrangement of the keys in a matrix keypad can be seen in the above figure. We can

arrange them in the particular columns and particular rows. Interface of the key pad to the micro

controller is shown the figure below. Depending on the number of keys required for the

application the matrix form is prepared. So for each key has two terminals one for the ground

and one is for the port pins. Each key need port allotment.

Matrix keypad of 4*4 (four rows and four columns) for that one columns ground terminals are

connected commonly and that is given to the one port pin. Input terminal of the keys according

to the one row all are connected commonly and that is given to the one port pins.

Like for 4*4 matrix keypad one port of micro controller totally used. Four pins for the ground

purpose and four pins for the input purpose.

Keypad Interfacing to Microcontroller:

Flow Chart:

Application:

Key pad is used for the telephones, mobile phones.

Key pads are used at the bank locker system.

There used the companies to enter the id numbers of the particular employee.

Uses

The keypad of a calculator contains the digits 0 through 9, from bottom upwards,

together with the four arithmetic operations.

Keypads are also a feature of some combination locks. This type of lock is often used on

doors, such as that found at the main entrance to some offices.

Many laptop computers have special function keys which turn part of the alphabetical

keyboard into a numerical keypad as there is insufficient space to allow a separate keypad

to be built into the laptop's chassis. Separate external plug-in keypads can be purchased.

LCD(Liqiud Crystal Display ):

One of the most common devices attached to an controller is an LCD display. Some of the most

common LCDs connected to the controllers are 16X1, 16x2 and 20x2 displays. This means 16

characters per line by 1 line 16 characters per line by 2 lines and 20 characters per line by 2 lines,

respectively. But in this project we are interfacing the 16*2 LCD it consists a 16 pins.

Schematic Diagram:

Figure: Schematic Diagram

Pin Description:

LCD consists of the three control line (RS, R/W &En), eight data lines (D0-D7), Supply Voltage

(Vcc), Contrast control (Vee) and ground (Vss).

PinSymbol Level Function

1 VSS - Power, GND

2 VDD - Power, 5V

3 Vo - Power, for LCD Drive

4 RS H/L

Register Select Signal

H: Data Input

L: Instruction Input

5 R/W H/LH: Data Read (LCD->MPU)

L: Data Write (MPU->LCD)

6 E H,H->LEnable

7-14 DB0-DB7 H/L Data Bus; Software selectable 4- or 8-bit mode

15 NC - NOT CONNECTED

16 NC - NOT CONNECTED

Control Pins Description :

EN (Enable):

Line is called "Enable." This control line is used to tell the LCD that you are sending it data. To

send data to the LCD, your program should make sure this line is low (0) and then set the other

two control lines and/or put data on the data bus. When the other lines are completely ready,

bring EN high (1) and wait for the minimum amount of time required by the LCD datasheet (this

varies from LCD to LCD), and end by bringing it low (0) again.

RS (Register Select):

Line is the "Register Select" line. When RS is low (0), the data is to be treated as a command or

special instruction (such as clear screen, position cursor, etc.). When RS is high (1), the data

being sent is text data which should be displayed on the screen. For example, to display the letter

"T" on the screen you would set RS high.

R/W (Read write):

Line is the "Read/Write" control line. When RW is low (0), the information on the data bus is

being written to the LCD. When RW is high (1), the program is effectively querying (or reading)

the LCD. Only one instruction ("Get LCD status") is a read command. All others are write

commands, so RW will almost always be low.

Finally, the data bus consists of 4 or 8 lines (depending on the mode of operation selected by the

user). In the case of an 8-bit data bus, the lines are referred to as DB0, DB1, DB2, DB3, DB4,

DB5, DB6, and DB7.

Logic status on control lines:

• E - 0 Access to LCD disabled

- 1 Access to LCD enabled

• R/W - 0 Writing data to LCD

- 1 Reading data from LCD

• RS - 0 Instructions

- 1 Character

Writing data to the LCD:

1) Set R/W bit to low

2) Set RS bit to logic 0 or 1 (instruction or character)

3) Set data to data lines (if it is writing)

4) Set E line to high

5) Set E line to low

Read data from data lines (if it is reading) on LCD:

1) Set R/W bit to high

2) Set RS bit to logic 0 or 1 (instruction or character)

3) Set data to data lines (if it is writing)

4) Set E line to high

5) Set E line to low

CHAPTER-6

SOFTWARE EXPLANATION

KEIL Software:

Installing the Keil software on a Windows PC:

Insert the CD-ROM in your computer’s CD drive.

On most computers, the CD will “auto run”, and you will see the Keil installation menu.

If the menu does not appear, manually double click on the Setup icon, in the root

directory: you will then see the Keil menu.

On the Keil menu, please select “Install Evaluation Software”. (You will not require a

license number to install this software).

Follow the installation instructions as they appear.

Loading the Projects:

The example projects for this book are NOT loaded automatically when you install the

Keil compiler. These files are stored on the CD in a directory “/Pont”. The files are arranged by

chapter: for example, the project discussed in Chapter 3 is in the directory “/Pont/Ch03_00-

Hello”. Rather than using the projects on the CD (where changes cannot be saved), please copy

the files from CD onto an appropriate directory on your hard disk.

Note: you will need to change the file properties after copying: file transferred from the CD will

be ‘read only’.

Configuring the Simulator:

Open the Keil Vision2

Go to Project – Open Project and browse for Hello in Ch03_00 in Pont and open it.

Go to Project – Select Device for Target ‘Target1’

Select 8052(all variants) and click OK

Now we need to check the oscillator frequency:

Go to project – Options for Target ‘Target1’

Make sure that the oscillator frequency is 12MHz.

Building the Target

Build the target as illustrated in the figure below

Running the Simulation

Having successfully built the target, we are now ready to start the debug session and run the

simulator. First start a debug session

The flashing LED we will view will be connected to Port 1. We therefore want to observe the activity on this

To ensure that the port activity is visible, we need to start the ‘periodic window update’ flag

Go to Debug - Go

While the simulation is running, view the performance analyzer to check the delay durations.

Go to Debug – Performance Analyzer and click on it

Double click on DELAY_LOOP_Wait in Function Symbols: and click Define button

Schematics

Transmitter Section

Receiver Section

Schematic Explanation

Transmitter Section

In this project we are interfacing different devices to microcontroller (AT89S52).AT89S52 is the

40 pin DIP (Dual In-Line Package) in this controller we have 32 I/O pins. To these Pins we can

connect to any devices and can be used as input /output devices. In order to make the IC work we

need to supply some voltage i.e., 5V supply is given to microcontroller i.e., 40 pin and GND is

connected to 20 pin to microcontroller.

Internal Clock frequency of microcontroller is 12MHz, in order to trigger the controller we have

to give the external clock frequency or external clock pulses i.e., 11.0592 MHz approximately it

is generated by the quad crystal from pins 18 & 19 in controller (XLAT1 & XLAT2).For

resetting the controller we have to connect a capacitor, a resister and a switch to 9 pin in

controller.

Here we interfaced the RF receiver, Encoder (HT12E), EEPROM, Buzzer, LCD and switches.

To port3 we interface the encoder, a encoder is one which consists the ‘n‘ inputs and ‘2n’

outputs.HT 12 E is a 18 pin IC in that 1 to 9 pin are connected to ground from 17 is connected to

RF transmitter RF transmitter consisting total 4 pin in that ground pin (GUD),One Data pin, one

are given to supply voltage (+5v supply)and one pin for antenna ,10to13 pins in

HT12D(decoder) are connected to microcontroller port 3.4 to 3.7 pins. In project we using the

434MHz frequency, the maximum range of these project is 50meters or 500feets.

EEPROM (24LC02B) is the 8-pin DIP IC; it is interfaced to microcontroller port 2.0 and port

2.1(SCL &SDA) 8-pin connected to supply (5Volt),4-pin is for GND, pin 1to pin 3 are address

pins these pins are connected to GND.

Here four switches are connected to port2 of microcontroller; those switches are connected to

port2.2 to port 2.5 in microcontroller port pins.

Receiver Section

In this project we are interfacing different devices to microcontroller (AT89S52).AT89S52 is the

40 pin DIP (Dual In-Line Package) in this controller we have 32 I/O pins. To these Pins we can

connect to any devices and can be used as input /output devices. In order to make the IC work we

need to supply some voltage i.e., 5V supply is given to microcontroller i.e., 40 pin and GND is

connected to 20 pin to microcontroller.

Internal Clock frequency of microcontroller is 12MHz, in order to trigger the controller we have

to give the external clock frequency or external clock pulses i.e., 11.0592 MHz approximately it

is generated by the quad crystal from pins 18 & 19 in controller (XLAT1 & XLAT2).For

resetting the controller we have to connect a capacitor, a resister and a switch to 9 pin in

controller.

Here we interfaced the RF receiver, decoder (HT12D), EEPROM, Buzzer, LCD and switches.

To port3 we interface the decoder, a decoder is one which consists the ‘2n ‘ inputs and ‘n’

outputs.HT 12 D is a 18 pin IC in that 1 to 9 pin are connected to ground from 14 is connected to

RF receiver RF receiver consisting total 8 pin in that ground pin (GUD),One Data pin, two are

given to supply voltage (+5v supply)and one pin for antenna ,10to13 pins in HT12D(decoder)

are connected to microcontroller port 3.4 to 3.7 pins. In project we using the 433MHz frequency,

the maximum range of these project is 50meters or 500feets.

LCD stands for Liquid Crystal Display it is used for displaying purpose. It is connected to port 1

of microcontroller.LCD contains 16-pins in this three control pins and seven data(D0…….D7)

pins for 8-bit mode and remaining two are used for back light or we can connect to GND and

Vcc supply. But here we using the 4-bit instead of 8-bit mode (i.e., four data pin are connected to

microcontroller).Pin1 is for GND, Pin2 is for supply (Vcc) it required 5volt and three control

pin4, pin5 & pin6 (Register Select (RS), Read/Write (RW) & Enable (EN)).Pin11 to Pin14 are

connected as a data pins it given interface port 1.2 to port 1.5 and control pins are connected to

port1.0 to port1.1.

EEPROM (24LC02B) is the 8-pin DIP IC; it is interfaced to microcontroller port 2.0 and port

2.1(SCL &SDA) 8-pin connected to supply (5Volt),4-pin is for GND, pin 1to pin 3 are address

pins these pins are connected to GND.

Here four switches are connected to port2 of microcontroller; those switches are connected to

port2.2 to port 2.5 in microcontroller port pins. Finally, buzzer is connected to port 3.0 it is used

to indication purpose.

BIBLIOGRAPHY

The 8051 Micro controller and Embedded Systems

Muhammad Ali Mazidi Janice Gillispie Mazidi

The 8051 Micro controller Architecture, Programming & Applications

Kenneth J. Ayala

Fundamentals of Micro processors and Micro computers

B. Ram

Micro processor Architecture, Programming & Applications

Ramesh S. Gaonkar

Electronic Components

D.V.Prasad

REFERENCES ON THE WEB:

www.national.com

www.atmel.com

www.microsoftsearch.com

www.geocities.com