Wireless Request Management System

WIRELESS REQUEST MANAGEMENT SYSTEM

To develop a working model of Wireless Request Management System

A report submitted

In partial fulfilment of the requirements for the degree

of

Bachelor of Technology

in

Electronics and Communication Engineering

Submitted By

Guru

Vashist

(0830531011)

Under the supervision of

Mr. Shashank Joheri

2


[Wireless Communication]

[These technologies allow drastic reductions in

network deployment costs, particularly for last-mile

connectivity in low-density areas. More important, the

technologies make possible an infrastructure development

model based on community-shared resources, small-scale

investments, and user experimentation. , for this potential

to be realized governments must rethink current

assumptions about spectrum management and universal

service policies.]

By –Guru Vashist

[12-May-2012]


Lecturer

Department of Electronics & Communication EngineeringAryabhatt College of Engineering & Technology, Baghpat

(U.P.)Gautam Buddh Technical University, Lucknow

May, 2012

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UNDERTAKING

I declare that the project work presented in this report entitled “ To develop a working

model of Wireless Request Management System”, submitted to the department of

electronics and communication, Aryabhatt College of Engineering and technology,

Baghpat, for the award of Bachelor of Technology degree in Electronics and

Communication Engineering from Gautam Budhh Technical University, Lucknow is my

original work. The contents of the report do not form the basis for the award of any other

degree to the candidate or to anybody else from this or any other University/Institution.

Further I have not plagiarized or submitted the same work for the award of any other

degree. In this case undertaking is found incorrect; I accept that our degree may

unconditionally be withdrawn.

May…………., 2012

A.C.E.T, Baghpat Name of student:

Guru Vashist (0830531011)

4


Certificate

It is Certified that Guru Vashist (0830531011) has carried out the project work presented

in this report entitled “To develop a working model of Wireless Request Management

System” for the award of Bachelor of Technology in Electronic & Communication from

Gautam Buddh Technical University, Lucknow under my supervision. The report

embodies results of original work, and studies are carried out by the myself and the

contents of the report do not form the basis for the award of any other degree to candidate

or to anybody else from this or any other University/Institution.

Supervisor

(Mr. Shashank Joheri)

(Lecturer)

Dept. of Electronics & Communication Engineering Aryabhatt College of Engineering & Technology Baghpat- 250 601, Uttar Pradesh, India

Date: ……………………..

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Acknowledgement

I wish to take this opportunity to express my deep sense of gratitude and thanks to

my head of department Mr. Vijendra Singh and supervisor Mr. Shashank Joheri. I am

thankful; to all faculty members and lab staff members of the department who helped me

directly or indirectly in completing the work. Last, but not the least, I am thankful to the

management members and director of Aryabhatt College of Engineering and Technology,

Baghpat (U.P.) who permitted and supported us for completing this project work.

Project associates:

Guru Vashisht (0830531011)

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ABSTRACT

These technologies allow drastic reductions in network deployment costs,

particularly for last-mile connectivity in low-density areas. More important, the

technologies make possible an infrastructure development model based on community-

shared resources, small-scale investments, and user experimentation. , for this potential to

be realized governments must rethink current assumptions about spectrum management

and universal service policies.

Wireless networks enable new applications Owing to the requirement for low

device complexity together with low energy consumption (i.e., long network lifetime), a

proper balance between communication and signal/data processing capabilities must be

found. This motivates a huge effort in research activities, standardization process, and

industrial investments on this field since the last decade. This report aims at reporting an

overview of wireless network technologies in case of handling request in hotels, hospitals

and in industries, which reduces human efforts as well as the complexity of handling the

wired networks

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Contents

Abstract v

List of figures ix

List of tables x

CHAPTER-1 Overview of the project 1

1.1 Introduction 1

1.2 Review of literature 1

1.2.1 History of wireless communication 2

1.2.2 Recent development 5

1.3Aim of the project 6

1.4 Wireless communication 6

1.4.1. Radio Frequency and its necessity 6

1.4.2 Brief Description of RF 7

1.4.3 Properties of Radio Frequency 7

1.5 Unique feature of our project 7

1.6 Block diagram 8

1.7 List of major component used 9

1.8 Requirements for RF communication 9

1.8.1 Power Supply 10

1.8.2 Regulated Power Supply 10

1.8.3 Diode rectifier- Full wave bridge rectifier 11

1.8.4 Capacitor Filter 12

1.9 Modulation techniques 14

1.10 Applications 16

CHAPTER-2 Microcontroller 18

2.1 Introduction 18

2.2 Reason to use microcontroller 18

2.3 General Description about Microcontroller 89S52 19

2.4 Features of ATMEL 89S52 Microcontroller 19

2.5 Comparison between 89S52 & 89C51 20

2.6 Block Diagram of Microcontroller 20

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2.7 Description of Pin Diagram ATMEL 89S52 Microcontroller 23

2.7.13 Special Function Registers 27

2.7.14 Memory Organization 27

2.7.15 Program Memory 28

2.7.16 Data Memory 28

CHAPTER-3 Transmitting and Receiving Sections 29

3.1 RF module introduction 29

3.2 RF Transmitter 30

3.2.2Pin Description 30

3.2.2General Description 31

3.3 Circuit diagram of Transmitting port 31

3.3.1 Detail working of Transmitter port 31

3.4 RF receiver module 32

3.4.1General description 32

3.4.2 Detail working description of receiving port 34

3.5 LCD 34

3.5.1 Reason to use 16x2 LCD display 34

3.5.2 Pin Description 36

CHAPTER 4 Encoder and decoder 37

4.1Reason to use encoder and decoder 37

4.2 Introduction of encoder IC used 37

4.2.1Features 37

4.2.2 Description of pin diagram 38

4.3 Introduction of decoder IC used 41

4.3.1 Features 41

4.3.2 Pin description 43

CHAPTER 5 Hardware Implementation of wireless request management system 45

5.1 Introduction 45

5.2 Circuit diagram of transmitter port 45

5.3 Implementation of transmitter port circuit diagram 46

5.4 Circuit diagram of receiver port 47

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5.5 Implementation of receiver port circuit diagram 48

5.6 Data sheets 49

Appendices 74

Conclusion 80

Future scope 81

References 82

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List of figure

Figure 1.1 Block diagram of request management system 10

Figure 1.2 Regulated power supply voltage regulator IC 7805 12

Figure 1.3 Full wave rectifier 13

Figure 1.4 Circuit Diagram and the respective output waveforms of Capacitive Filter 13

Figure 1.5 Block diagram of ASK modulation 15

Figure 2.1 Simple architecture of microcontroller 21

Figure 2.2 showing Block Diagram ATMEL 89S52 Microcontroller 22

Figure 2.3 Pin diagram of 89S52 microcontroller 23

Figure 3.1 ST-TX-01-ASK Transmitter 30

Figure 3.2 Circuit diagram of transmitting port 31

Figure 3.3 Pin diagram of ST-RX02-ASK 32

Figure 3.4 Circuit diagram of receiver port 33

Figure 3.5 Pin diagram of 16x2 LCD 35

Figure 4.1 Block diagram of encoder IC HT12E 38

Figure 4.2 Pin diagram of HT12E 39

Figure 4.3 Block diagram of HT12D decoder 42

Figure 4.4 Pin diagram of HT12D decoder IC 43

Figure5.2 Circuit diagram of transmitter port 45

Figure 5.3 Implementation of transmitter port circuit diagram 46

Figure5.4 Circuit diagram of receiver port 47

Figure5.5Implementation of receiver port circuit diagram 48

Figure 5.6.1: Types of capacitors 63

Figure 5.6.2: principle of working of capacitor 64

Figure5.6.3: A simple demonstration of a parallel-plate capacitor 64

Figure 5.6.4: Operation of pressure switch 72

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List of table

Table2.1 Comparison between 89S52 & 89C51 16

Table2.2 Different functions of port1 21

Table2.3 Different functions of port3 22

Table3.1 LCD pin description 33

Table4.1 Pin description of HT12E IC 38

Table4.2 Pin description of HT12D IC 42

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CHAPTER 1

Overview of the project

1.1 Introduction

In this project, we present the concept of transmitting information wirelessly, because in

wired network there arise many problems like handling management maintenance cost

factor reliability safety which is almost eliminated by wireless network.

1.2 Review of literature

It consist of theories, backgrounds and recent work going on these days related with

Wireless request management system

1.2.1 History of wireless communication

We know that wireless networking has emerged as its own discipline over the past

decade. Wireless communication can be used for cellular voice telephony, wireless access

to the internet, wireless home networking etc. wireless networks have profoundly

impacted our life-style. After a decade of exponential growth, today’s wireless industry is

one of the largest industries in the world. The use of light for wireless communications

reaches back to ancient times. In former times, the light was either modulated using

mirrors to create a certain light on/light off pattern. All optical transmission systems

suffer from the high frequency of the carrier light as every little obstacle shadows the

signal rain and fog make communication almost impossible. At that time it was not

possible to focus light as efficiently as can be done today by means of a laser, so actual

wireless communication did not actually started until the discovery of electromagnetic

waves and the development of the equipment to modulate them. It all started with

Michael Faraday demonstrating EM waves induction in 1831 and James C. Maxwell

(1831-79) laying the theoretical foundations for electromagnetic fields with his famous

equations. And finally, Heinrich hertz (1857-94) was the first to demonstrate the wave

character of electrical transmission through space (1886), thus proving Maxwells

equations. Today we are using that HZ. After that Nikala Tesla (1856-1943) soon

increased the distance of EM waves.

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The ability to communication with people on the move has evolved remarkably

since Guglielmo Marconi first demonstrated radio’s ability to provide continuous contact

with ships sailing the English channel. We can say that the name, which is most closely

connected with the success of wireless communication, is certainly that of Guglielmo

Marconi (1874-1937). He gave the first demonstration of wireless telephony in 1895

using long wave transmission with very high transmission power (>200 kW).

In 1907, the first commercial transatlantic connections were set up. Huge base

stations using up to 30 hundred meter high antennas were used on both sides of the

Atlantic ocean. The first radio broadcast took place in 1906 when Reginald A. Fessenden

(1866-1932) transmitted voice and music for Christmas. In 1915 the first wireless voice

transmission was set up between Newyork and Sanfrancisco. The 1st commercial radio

station started in 1920, but at that time sender and receiver required huge antennas and

high transmission power. Again in 1920 Marconi developed short waves, using short

waves it is possible to send short radio waves around the world bouncing at the

ionosphere, now a days also we are using this technique. After 1906 when vacuum tube is

involved, distance between transmitter and receiver is reduced. One of the first ‘mobile’

transmitters was on board a Zeppelin in 1911. Now a days both AM and FM is used for

TV broadcasting Many national and international projects started in the area of wireless

communications after the 2nd world war. The first wireless network is started in 1958 by

Germany, on carrier frequency of 160 MHz. Connection setup was only possible from the

mobile station, but it is not possible to transfer a call from one base station to other (i.e.,

handoff is not possible).

In 1972 a wireless network started using same 160 MHz carrier known as B-Netz

by Germany. By using this network it is possible to initiate the connection setup, from a

station in the fixed telephone network, if the current location of the mobile receiver had to

be known. At the same time, the northern European countries of Denmark, Finland,

Norway, and Sweden setup one wireless network by using 450 MHz carrier known as

Nordic mobile telephone (NMT) system, NMT at 900 MHz started in 1986. After 1982

European countries decided to develop a pan-European mobile phone standard. The new

system is designed by using new spectrum of 900 MHz, provide seamless handover of a

telephone call from on network provider to another while crossing national boundaries

(which is known as interstate Roaming) and it offer both voice and data service with fully

digital transmission. All above criteria are the foundation of Group special mobile

(GSM).

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After 1983 Ist generation mobile technology started by US known as advance

mobile phone system (AMPS). AMPS carrier frequency is 850 MHz and it is an analog

mobile phone systems. In 1984 our basic telephones at homes become wireless by

development of standard CT1 (cordless telephones). By using AMPS handoffs between

different cells is possible and all AMPS MSC’s are connected with signalling system-7

protocol. Also MSC’s are able to locates its mobile user automatically within the whole

network supported by that MSC’s. This analog network was switched off in 2000. By

using AMPS we can transmit voice, fax, data (via modem), X.25 protocol and email.

In 1987 system CT2 started which is successor of CT1, was embodied into British

standards and later adopted by ETSI for Europe (ETS, 1994), it uses the spectrum at 864

MHz and offers a data channel at a rate of 32 K bit/S. Basic digital systems started in

1990s. In 1991, ETSI adopted the standard digital European cordless telephone (DECT)

for digital cordless telephony (ETSI, 1998). DECT technology works at a spectrum of

1880-1900 MHz with a range of 100-500 m, it support nearly 120 duplex channels and

data transmission rate is 1.2 M bit/S. Some other features of DECT are voice encryption

authentication etc. New DECT is known as Digital enhanced cordless

telecommunications.

After many years of discussions and field trials, GSM was standardized in a

document of more than, 5,000 pages in 1991. GSM is the most successful digital mobile

telecommunication system in the world today. It is used by over 800 million people in

more than 190 countries. For a second generation system which was fully digital system.

In 1992, GSM changed its name to the Global system for mobile communications for

marketing reasons. The setting of standards for GSM is under the aegis of the European

Technical Standards Institute (ETSI). GSM was first introduced into the European market

in 1991. By the end of 1993, several non-European countries in South America, Asia and

Australia had adopted GSM and the technically equivalent offshoot, DCS 1800, which

supports personal communication system (PCS) in the 1.8 GHz to 2.0 GHz radio bands

recently created by governments throughout the word.[4]

GSM is a 2nd generation (2G) cellular system standard that was developed to solve the

fragmentation problems of the first cellular system in Europe. Basic aim of GSM was to

provide a mobile phone system that allows users to roam throughout Europe and provide

voice services compatible to ISDN and other PSTN systems. GSM was the world’s first

cellular system to specify digital modulation and network level architectures and services,

GSM has initially been deployed in Europe user 890-915 MHz for uplinks and 935-960

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MHz for downlinks, this system is also known as GSM 900. Other version of GSM is

known as GSM 1800 MHz (1710-1785 MHz uplink, 1930-1990 MHz downlink) also

known as DCS (Digital Cellular System) 1800. GSM system used by US is GSM 1900

MHz (1850-1900 MHz uplink, 1930-1990 MHz downlink) also known as PCS-1900

(Personal Communication Services). A GSM system that has been introduced in several

European countries for railroad systems is GSM rail (GSM-R, 2002), (EISI 2002) Main

application of GSM-R is the control of trains, switches, gates and signals.

GSM provides facility like full international roaming, automatic location services,

authentication encryption on the wireless link, efficient interoperation with ISDN systems

and high audio quality. Also it provides services like short message (SMS) with upto 160

alphanumeric characters, Fax group 3, and data services at 9.6 K bit/S have been

integrated. Know a days over 70% of world’s wireless market is under control of GSM.

But in most populated areas where user densities is high it is found that analog

AMPS technology used in US and digital GSM technology at 900 MHz in Europe are not

sufficient. To solve this problem in the US different companies developed different new,

more bandwidth–efficient technology to operate side-by-side with AMPS in the same

frequency band, and three new technology developed.

1. Analog narrowband AMPS (IS-88, TIA, 1993a).

2. TDMA (IS-136, TIA-1996).

3. CDMA (IS-95, TIA-1993b).

The Europeans countries agreed to use GSM in the 1800 MHz spectrums this

system is also known as DCS 1800 digital cellular system. GSM-1800 system having

better voice quality due to newer speech codes. GSM is also available in the US as GSM-

1900 (also called PCS 1900) using spectrum at 1900 MHz like the newer versions of the

TDMA and CDMA systems. During the development of new technology Europe is

concentrated up on standards of technology but US believes in market forces. So while all

European countries working on common standard and roaming is possible in other

countries also, but US still struggles with many incompatible systems.

HIPERLAN (High performance radio local area network) started in 1996. On

ETSI standard HIPERLAN type should operate at 5.2 GHz and should offer data rates of

up to 23.5 Mbit/S.In 1997, the IEEE standard 802.11 started and it is popular than

HIPERLAN. It works at the license free Industrial Science Medical (ISM) band at 2.4

GHz and Infrared offering 2 M bit/S in the beginning (Up to 10 M bit/S with proprietary

solutions already at that time). In 1998 mobile communication via satellites started with

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the Iridium system (Iridium, 2002). After introduction of Iridium technology, very small

and portable mobile satellite telephones using data services started. In consists of 66

satellites in low earth orbit and uses the 1.6 GHz band for communication with the mobile

phone. Universal mobile telecommunications system (UMTS) started in 1998 by

European countries as the European proposal for the International Telecommunication

Union (ITU) IMT-2000 (International mobile telecommunications). Initially UMTS

combines GSM network technology with more bandwidth efficient CDMA solutions. The

IMT-2000 recommendations define a common worldwide framework for future mobile

communication at 2 GHz (ITU, 2002). This includes a framework for services, satellite

communication network architecture, strategies for developing countries requirements of

the radio interface, spectrum considerations, security and management frameworks, and

different transmission technique. The IEEE standard 802.11 (IEEE 1999) specifies the

most famous family of WLANs in which many products are available.

As the standard’s number indicates, this standard belongs to the group of 802.X

LAN standards e.g., 802.3 Ethernet on 802.5 Token ring. This standard specifies the

physical and medium access layer adopted to the special requirement of wireless LAN’s,

but offers the same interface as the others to higher layers to maintain interoperability,

with standard 802.11 the subscription presents the enhancements of the original standard

for higher data rates, 802.11a (up to 54 Mbit/S at 5 GHz) and 802.11b (11 Mbit/S).

In 1998 five companies (Ericsson, Intel, IBM, Nokia, Toshiba) founded the Bluetooth

consortium with the goal of developing a single-chips low, cost radio-based wireless

network technology. Known as Special Interest Group (SIG), many other companies and

research institutions joined this group. Main goal of this group was the development of

mobile phones, laptops, notebooks, headsets etc. including Bluetooth technology, by the

end of 1999. In 2001, the first products hit the mass market, and many mobile phones,

laptops, PDAs video cameras etc. equipped with Bluetooth technology today. The IEEE

802.11b offering 11 M bit/S at 2.4 GHz. The same spectrum is used by Bluetooth, a short

range technology to set-up wireless personal area networks with gross data rates loss than

1 M bit/S. The WAP (wireless application protocol (WAP) started at the same time as i-

male in Japan. But WAP did not succeed in the beginning i-male soon became a

tremendous success.

In 2000 higher data rates packet-oriented transmission for GSM (HSCSD, GPRS)

started. The third generation of mobile communication started in 2001 in Japan with the

FDMA services, in Europe with several field trials and in Korea with cdma 2000. IEEE

17


started new WLAN standard, 802.11a operating of 5 GHz and offering gross data rates of

54 Mbit/S. In 2002 new WLAN developments followed. Example are 802.11g which

provide 54 Mbit/S at 2.4 GHz and many new Bluetooth applications.

Now we are waiting for 4G technology no one knows exactly what the new

generation of mobile and wireless system will look like, but, there are strong indications

that it will be widely internet based the system will use internet protocols and internet

applications. By using 4G technology it may possible when your washing machine will

send an e-mail to your cell phone informing you about the washing information. Suppose

you are driving and cannot read the e-mail. Your car audio will connected to your cell-

phone, using Bluetooth and you may read your e-mail. You can then dictate your e-mail

reply, just in case want to modify the program. And when you reach home, you will find

your laundry all done while you are away. [9] [10]

1.2.2 Recent development

Wireless communications have become synonymous with relatively short range radio

communications that are able to replace wired installations. Recent years have seen a

phenomenal level of growth, to the extent that they are common place for many

applications, and they are one of the fastest growing areas of the electronics industry.

Even though the technology is growing rapidly some standards have already gone by the

board. One notable example is Home RF. Despite this new standards and technologies are

being introduced to meet the demands of new sectors of this growing industry.

For many years there has been a variety of short range wireless systems. These

have normally not conformed to world wide specifications and often they were developed

for individual applications. However the development of integrated circuit technology

started to open far greater possibilities. Not only were costs reducing, but the capabilities

were increasing. Before any further developments could take place other enablers needed

to be set in place. One of the major changes took place in radio licensing. It had been a

requirement to possess a licence for most radio transmissions. This had been a

requirement to ensure that use of the radio spectrum was regulated in a way that

prevented undue interference to other users. Then in 1985 the Federal Communications

Commission (FCC) in the USA opened up some small portions of the spectrum for

licence free communications applications. The bands that were used were the 900 MHz,

2.4 GHz, and 5.8 GHz Industrial, Scientific, and Medical (ISM) bands. These portions of

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the spectrum were allocated to a variety of non-communications applications including

microwave ovens. As such they were already used by non-licensed users, but for

communications purposes it was stated that any new systems that were implemented

would have to avoid the other transmissions and successfully communicate in the

presence of the interference.

In our project we are using ST TX01 –ASK and RX02 rf link based transmitter

and receiver which are too small in size and does not require any type of antenna for

transmission and reception purpose.

1.3Aim of the project

The aim of this project is to transmit the request from transmitter side to receiver side

with the help of RF module. The main objectives of this project are to use radio frequency

bands.

1. The transmission of request from transmitter through air.

2. The receiver senses these signals from the air.

3. This major project makes use of the transmitter and receiver at 433MHz that is

available at low cost hence making it very complicated.

4. The Radio Frequency based control proves to be more advantageous compared

to the Infrared Red based control that limits the operating range to only a few

meters of distance.

Now first come on Wireless Communication System which is as follows

1.4 Wireless communication

Wireless communication, as the term implies, allows information to be exchanged

between two devices without the use of wire or cable. A wireless keyboard sends

information to the computer without the use of a keyboard cable; a cellular telephone

sends information to another telephone without the use of a telephone cable. Changing

television channels, opening and closing a garage door, and transferring a file from one

computer to another can all be accomplished using wireless technology. In all such cases,

information is being transmitted and received using electromagnetic energy, also referred

to as electromagnetic radiation. One of the most familiar sources of electromagnetic

radiation is the sun; other common sources include TV and radio signals, light bulbs and

microwaves.[2]

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1.4.1. Radio Frequency and its necessity

Radio frequency is a frequency or rate of oscillation within the range of about 3Hz to 300

GHz. This range corresponds to frequency of alternating current electrical signals used to

produce and detect radio waves. Since most of this range is beyond the vibration rate the

most mechanical systems can respond to, RF usually refers to oscillations in electrical

circuits. RF is widely used because it does not require any line of sight, less distortions

and no interference. Examples include, Cordless and cellular telephone, radio and

television broadcast stations, satellite communications systems, and two-way radio

services all operate in the RF spectrum.[1]

1.4.2 Brief Description of RF

Radio frequency (abbreviated RF) is a term that refers to alternating current (AC) having

characteristics such that, if the current is input to an antenna, an electromagnetic (EM)

field is generated suitable for wireless broadcasting and/or communications. These

frequencies cover a significant portion of the electromagnetic radiation spectrum,

extending from nine kilohertz (9 kHz),the lowest allocated wireless communications

frequency (it's within the range of human hearing), to thousands of gigahertz(GHz).

When an RF current is supplied to an antenna, it gives rise to an electromagnetic

field that propagates through space. This field is sometimes called an RF field; in less

technical jargon it is a "radio wave." Any RF field has a wavelength that is inversely

proportional to the frequency.

As the frequency is increased beyond that of the RF spectrum, EM energy takes the form

of infrared (IR), visible, ultraviolet (UV), X rays, and gamma rays. ), X rays, and gamma

rays. Many types of wireless devices make use of RF fields. Some wireless devices

operate at IR or visible-light frequencies, whose electromagnetic wavelengths are shorter

than those of RF fields.[1]

1.4.3 Properties of Radio Frequency

Electrical currents that oscillate at RF have special properties not shared by direct current

signals:

1. One such property is the ease with which it can ionize air to create a conductive

path through air. This property is exploited by 'high frequency' units.

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2. Another special property is an electromagnetic force that drives the RF current to

the surface of conductors, known as the skin effect.[5]

1.5 Unique feature of our project

Easy to maintain

In compare to wired system of request management it is a very complicated task to detect

or sort out the problem, because in wired communication all we need is to follow the

number of cables that used in communication which arise a lot of confusion, but in our

system as there is no introduction of wire between transmitter and receiver module so in

case of any kind of problem we only need to check only receiving or transmitting module

to sort out the error.

Cost factor

In wired request management system we need a long connections of wires between room

and reception are required .As the number of room increases it increase the number of

wires which effect the cost of system.

Reliable:

In case of infrastructure development of a building some wires may be disconnected

which may interrupt the system and arise problem to visitor for request serving purpose

and also make a negative mark on reputed image of a hotel but no such problem is arise in

wireless communication.

Security

In wired system there may arise a problem of crosstalk, but no such kind of problem is

arise in wireless system. In wireless system data is encoded in particular code which can

only be decoded by the decoder present at receiver site.

1.6 Block diagram

Our project is simply divided into two ports:

1. Transmitting port

2. Receiving port

Both modules are connected with each other through a Radio frequency link.

There are no of switches available at each room, if a visitor from any room

require any kind of room service a switch is press by a visitor , when a switch is pressed,

an electrical signal is pass to the encoder the encoder will take the signal in parallel and

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transfer the signal in a serial manner to the transmitting module which further transmit

bit by bit information to the receiver module through a Radio frequency link and a L.E.D.

will blink on receiving port. Now from the receiver module the signal will transmit

serially to the input of decoder which will transmit in a parallel manner to the port two of

the microcontroller then a particular function will be perform by a microcontroller as per

the instruction of coding and the request will display on lcd screen with a beep sound of a

buzzer.

Figure 1.1 Block Diagram of Request Management System

1.7 List of major component used

Device I.C. used

Encoder HT12E

Radio frequency transmitting module ST -TX01-ASK

Radio frequency receiving module ST-RX02 -ASK

Decoder HT12D

Microcontroller 89S52

Lcd display (16X2)

Buzzer

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1.8 Requirements for RF communication

RF communication is required for the transmission of radio waves from RF transmitter

(remote) to RF receiver (robot) to enable the movement of the robot in this project. The

basic requirements for the RF communication used in this project are as follows:

Power supply

RF Transmitter

RF Receiver

Encoder and Decoder

Microcontroller

1.8.1 Power Supply

The input to the circuit is applied from the regulated power supply. The a.c. input i.e.,

230V from the mains supply is step down by the transformer to 12V and is fed to a

rectifier. The output obtained from the rectifier is a pulsating d.c voltage. So in order to

get a pure d.c voltage, the output voltage from the rectifier is fed to a filter to remove any

a.c components present even after rectification. Now, this voltage is given to a voltage

regulator to obtain a pure constant dc voltage.

1.8.2 Regulated Power Supply

A variable regulated power supply, also called a variable bench power supply, is one

where you can continuously adjust the output voltage to your requirements. Varying the

output of the power supply is the recommended way to test a project having doubled

checked parts placement against circuit drawings and the parts placement guide. Most

digital logical circuits and processors need a 5 volt power supply. To use these parts we

need to build a regulated 5 volt source. Usually you start with an unregulated power

supply ranging from 9 volts to 24 volts DC. To make a 5 volt power supply, we use a

LM7805 voltage regulator IC (Integrated circuit). The IC is shown below.

Specifications of voltage regulator IC

V REG +5.0V, 7805, TO-220FP-3

Dropout voltage:2V

No. of Outputs:1

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No. of Pins:3

Voltage Regulator IC Case Style:TO-220FP

Operating Temperature Range:0°C to +150°C

Max Input Voltage:35V

Max Output Current:1.5A

Max Output Voltage:5V

Max Supply Voltage:20V

Min Input Voltage:7V

Min Supply Voltage:8V

Operating Voltage Tolerance +:4%

Termination Type: Through Hole

Figure 1.2: Regulated Power Supply

The LM7805 is simple to use. you simply connect the positive lead of your unregulated

DC power supply (anything from 9 VDC to 24 VDC ) to the Input pin , connect the

negative lead to the Common pin and then when you turn on the power , you get a 5 volt

supply from the Output pin.

1.8.3 Diode rectifier- Full wave bridge rectifier

The need for a centre tapped power transformers is eliminated in the bridge rectifier .it

contains four diodes D1 , D2 , D3 and D4 connected to from bridge as shown below.

24


Figure 1.3: Full wave

bridge rectifier

1.8.4 Capacitor Filter

A capacitive filter helps in reducing the ripples. A capacitive filter is shown below.

Figure 1.4: Circuit Diagram and the respective output waveforms of Capacitive Filter

The a.c. supply to be rectified is applied to the diagonally opposite ends of the

bridge through the transformer. Between other two ends of the bridge , the load resistance

RL is connected .

25


1.9 Modulation techniques

The transmission of digital signals is increasing at a rapid rate. Low-frequency analogue

signals are often converted to digital format (PAM) before transmission. The source

signals are generally referred to as baseband signals. Of course, we can send analogue

and digital signals directly over a medium. From electro-magnetic theory, for efficient

radiation of electrical energy from an antenna it must be at least in the order of magnitude

of a wavelength in size; c = fl, where c is the velocity of light, f is the signal frequency

and l is the wavelength. For a 1kHz audio signal, the wavelength is 300 km. An antenna

of this size is not practical for efficient transmission. The low-frequency signal is often

frequency-translated to a higher frequency range for efficient transmission. The process is

called modulation. The use of a higher frequency range reduces antenna size.

Amplitude-shift keying (ASK) is a form of modulation that represents digital

data as variations in the amplitude of a carrier wave. Any digital modulation scheme uses

a finite number of distinct signals to represent digital data. ASK uses a finite number of

amplitudes, each assigned a unique pattern of binary digits. Usually, each amplitude

encodes an equal number of bits. Each pattern of bits forms the symbol that is represented

by the particular amplitude. The demodulator, which is designed specifically for the

symbol-set used by the modulator, determines the amplitude of the received signal and

maps it back to the symbol it represents, thus recovering the original data. Frequency and

phase of the carrier are kept constant.

In the modulation process, the baseband signals constitute the modulating signal

and the high-frequency carrier signal is a sinusoidal waveform. There are three basic

ways of modulating a sine wave carrier. For binary digital modulation, they are called

binary amplitude-shift keying (BASK), binary frequency-shift keying (BFSK) and binary

phase shift keying (BPSK). Modulation also leads to the possibility of frequency

multiplexing. In a frequency-multiplexed system, individual signals are transmitted over

adjacent, no overlapping frequency bands. They are therefore transmitted in parallel and

simultaneously in time. If we operate at higher carrier frequencies, more bandwidth is

available for frequency-multiplexing more signals. Like AM, ASK is also linear and

sensitive to atmospheric noise, distortions, propagation conditions on different routes in

PSTN, etc. Both ASK modulation and demodulation processes are relatively inexpensive.

The ASK technique is also commonly used to transmit digital data over optical fiber. For

26


LED transmitters, binary 1 is represented by a short pulse of light and binary 0 by the

absence of light. Laser transmitters normally have a fixed "bias" current that causes the

device to emit a low light level. This low level represents binary 0, while a higher-

amplitude lightwave represents binary 1.

The simplest and most common form of ASK operates as a switch, using the

presence of a carrier wave to indicate a binary one and its absence to indicate a binary

zero. This type of modulation is called on-off keying, and is used at radio frequencies to

transmit Morse code (referred to as continuous wave operation).

More sophisticated encoding schemes have been developed which represent data

in groups using additional amplitude levels. For instance, a four-level encoding scheme

can represent two bits with each shift in amplitude; an eight-level scheme can represent

three bits; and so on. These forms of amplitude-shift keying require a high signal-to-noise

ratio for their recovery, as by their nature much of the signal is transmitted at reduced

power.

Here is a diagram showing the ideal model for a transmission system using an ASK

modulation:-

Figure1.5 Block diagram of ASK modulation

It can be divided into three blocks. The first one represents the transmitter, the

second one is a linear model of the effects of the channel, the third one shows the

structure of the receiver. The following notation is used:

ht(f) is the carrier signal for the transmission

hc(f) is the impulse response of the channel

n(t) is the noise introduced by the channel

hr(f) is the filter at the receiver

L is the number of levels that are used for transmission

27


Ts is the time between the generation of two symbols

A binary amplitude-shift keying (BASK) signal can be defined by s(t) = A m(t)

cos 2fct, 0 < t< T where A is a constant, m(t) = 1 or 0, f c is the carrier frequency,

and T is the bit duration. It has a power P = A2/2. [2][3]

Amplitude shift keying digital modulation technique is one of the best modulation

techniques and has several advantages over others for small ranges like in our project

range up to 100 meters. Fsk is the nearest competitor of ask in this field, ask has certain

advantages over Fsk as mentioned below.

Ask Transmitter and Receiver are quite simpler than Fsk.

Ask Transmitter current is 50% more than the Ask, hence Ask require less power.

Saw Based Ask transmitter are more robust when exposed to extreme temperature

vibrations and shock..

Fsk Transmitter requires 1.5 times the Bandwidth compared to Ask.

Ask Receiver sensitivity is nearly equal or better than Fsk.

Properly implemented Ask Receiver performance of co-channel interference is

generally better than Fsk..

Properly implemented Ask Receiver performance with amplitude flutter is equal

to or better than Fsk..

APPLICATIONS

In hospitals there are so many patients for whom it is not easy to call a person, a

doctor or a nurse for their help so it can be very useful for patient to call a doctor at the

time of emergency or in absence of a nurse in their room. In case of restaurant we can

apply the same system on each and every table so that there is no need of a waiter to ask

the order at each table, the order will automatically be placed by the person to the

reception and waiter will serve the person as per the order. It may also be use in restaurant

to inform the cook about which dish to be prepared and how much is to be prepared

according to the order of the customer. We can also implement the same system on each

seat of a train and in airplane to call an airhostess for their services. In case of hotels the

each room will equip pied with such system so that visitor can simply press his switch in

his room and order place by a visitor will be visible on a LCD screen at reception.

Many other works can also be performed in hotels using the same system for example if

we implement the receiver port at laundry department then a visitor can place his request

28


for laundry service by simply pressing a switch present in his room. It can be used for the

purpose of informing the employees, managers and workers for receiving of materials and

transferring the material from one department to another.

29


CHAPTER 2

MICROCONTROLLER

2.1 Introduction

A microcontroller (sometimes abbreviated µC, uC or MCU) is a small computer on a

single integrated circuit containing a processor core, memory, and programmable

input/output peripherals. Programmable 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.

Microcontrollers are used in automatically controlled products and devices, such

as automobile engine control systems, implantable medical devices, remote controls,

office machines, appliances, power tools, toys and other embedded systems. By reducing

the size and cost compared to a design that uses a separate microprocessor, memory, and

input/output devices, microcontrollers make it economical to digitally control even more

devices and processes. Mixed signal microcontrollers are common, integrating analog

components needed to control non-digital electronic systems.

Some microcontrollers may use four-bit words and operate at clock rate

frequencies as low as 4 kHz, for low power consumption (milliwatts or microwatts). They

will generally have the ability to retain functionality while waiting for an event such as a

button press or other interrupt; power consumption while sleeping (CPU clock and most

peripherals off) may be just nano watts, making many of them well suited for long lasting

battery applications. Other microcontrollers may serve performance-critical roles, where

they may need to act more like a digital signal processor (DSP), with higher clock speeds

and power consumption.[7]

2.2Reason to use microcontroller

As we need to display a message on LCD with a beep sound of buzzer this function

displaying a request on just pressing a switch is perform by a microcontroller on the basis

of coding. A microcontroller is one and only a simple and cheap device to perform such

controlling and multitasking functions at a time.

30

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

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

http://en.wikipedia.org/wiki/Word_(computer_architecture)

http://en.wikipedia.org/wiki/Mixed-signal_integrated_circuit

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

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

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

http://en.wikipedia.org/wiki/Random-access_memory

http://en.wikipedia.org/wiki/Programmable_read-only_memory

http://en.wikipedia.org/wiki/Flash_memory#NOR_flash

http://en.wikipedia.org/wiki/Input/output

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


2.3 General Description about Microcontroller 89S52

The AT89S52 is a low-power, high-performance CMOS 8-bit microcontroller with 8K

bytes of in-system programmable Flash memory. The device is manufactured using

Atmel’s high-density non-volatile memory technology and is compatible with the

industry-standard 80C51 instruction set and pin out. The on-chip Flash allows the

program memory to be reprogrammed in-system or by a conventional non-volatile

memory programmer. By combining a versatile 8-bit CPU with in-system programmable

Flash on a monolithic chip, the Atmel AT89S52 is a powerful microcontroller which

provides a highly-flexible and cost-effective solution to many 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, a six-vector two-level interrupt architecture, a 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 con-tents but freezes the oscillator, disabling all other chip functions until the next

interrupt or hardware reset. [7][8]

2.4 Features of ATMEL 89S52 Microcontroller

8K Bytes of In-System Programmable (ISP) Flash Memory – Endurance: 10,000

Write/Erase Cycles

4.0V to 5.5V Operating Range

Fully Static Operation: 0 Hz to 33 MHz

Three-level Program Memory Lock • 256 x 8-bit Internal RAM

32 Programmable I/O Lines

Three 16-bit Timer/Counters

Eight Interrupt Sources

Full Duplex Serial Channel

Low-power Idle and Power-down Modes

Interrupt Recovery from Power-down Model

Fast Programming Time

31


2.5 Comparison between 89S52 & 89C51

89C51 89S52

4K Bytes of In-System Reprogrammable

Flash Memory

8K Bytes of In-System Reprogrammable

Flash Memory

128 x 8-bit Internal RAM 256 x 8-bit Internal RAM

Two 16-bit Timer/Counters Three 16-bit Timer/Counters

Six Interrupt Sources Eight Interrupt Sources

Table2.1 Comparison between 89S52 & 89C51

First of all both microcontroller has been discontinued by Atmel. If your design is

based on 89C51, you don't have to worry if it's changed later with 89S52. No changes are

to be performed, neither software nor hardware (some minor settings in the hardware

programmer device).But if your software relies on 89S52 then simple looking at the

features provided by both microcontroller will tell you in what aspect will changes affect

your design if a replacement with 89C51 has to be done.

2.6 Block Diagram of Microcontroller

The block diagram is the architecture the 89S52 device can seem very complicated, and

since we are going to use the C high level language to program it, a simpler architecture

can be represented as the figure2.1.The figure shows the main features and components

that the designer can interact with. You can notice that the 89S52 has four different ports,

each one having eight Input/output lines providing a total of 32 I/O lines. Those ports can

be used to output DATA and orders do other devices, or to read the state of a sensor, or a

switch. Most of the ports of the 89S52 have ‘dual function’ meaning that they can be used

for two different functions: the fist one is to perform input/output operations and the

second one is used to implement special features of the microcontroller like counting

external pulses, interrupting the execution of the program according to external events,

performing serial data transfer or connecting the chip to a computer to update the

software.

Each port has eight pins, and will be treated from the software point of view as an

8-bit variable called ‘register’, each bit being connected to a different Input/output pin.

There are two different memory types: RAM and EEPROM. Shortly, RAM is used to

32


store variable during program execution, while the EEPROM memory is used to store the

program itself, that’s why it is often referred to as the ‘program memory’.

It is clear that the CPU (Central Processing Unit) is the heart of the

microcontrollers; it is the CPU that will Read the program from the FLASH memory and

execute it by interacting with the different peripherals [7]

33


Figure2.1 Simple architecture of microcontroller

34


Figure 2.2 showing Block Diagram ATMEL 89S52 Microcontroller

2.7 Description of Pin Diagram ATMEL 89S52 Microcontroller

35


Figure2.3 Pin diagram of 89S52 microcontroller

2.7.1 VCC

Supply voltage.

2.7.2 GND

Ground

2.7.3 Port 0

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

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

impedance inputs.

Port 0 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.

2.7.4 Port1

Port 1 is an 8-bit bidirectional I/O port with internal pull-ups. The Port 1 output buffers

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

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

externally being pulled low will source current (IIL) because of the internal pull-ups.

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.

Table2.2

36


2.7.5 Port 2




externally being pulled low will source current (IIL) because of the internal pull-ups.

Port 2 emits the high-order address byte during fetches from external program memory

and during accesses to external data memory that uses 16-bit addresses (MOVX @

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

accesses to external data memory that uses 8-bit addresses (MOVX @ RI), Port 2 emits

the contents of the P2 Special Function Register.

Port 2 also receives the high-order address bits and some control signals during Flash

programming and verification.

2.7.6 Port 3




externally being pulled low will source current (IIL) because of the pull-ups. Port 3

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

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

Table2.3

37


2.7.7 RST

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

resets the device. This pin drives high for 98 oscillator periods after the Watchdog times

out. The DISRTO bit in SFR AUXR (address 8EH) can be used to disable this feature. In

the default state of bit DISRTO, the RESET HIGH out feature is enabled.

2.7.8 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 of 1/6

the oscillator frequency and may be used for external timing or clocking purposes. Note,

however, that one ALE pulse is skipped during each access to external data memory. If

desired, ALE operation can be disabled by setting bit 0 of SFR location 8EH. With the bit

set, ALE is active only during a MOVX or MOVC instruction. Otherwise, the pin is

weakly pulled high. Setting the ALE-disable bit has no effect if the microcontroller is in

external execution mode.

2.7.9 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.

2.7.10 EA/VPP

External Access Enable. EA must be strapped to GND in order to enable the device to

fetch code from external program memory locations starting at 0000H up to FFFFH.

Note, however, that if lock bit 1 is programmed, EA will be internally latched on reset.

EA should be strapped to VCC for internal program executions. This pin also receives the

12-volt programming enable voltage (VPP) during Flash programming.

2.7.11 XTAL1

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

38


2.7.12 XTAL2

Output from the inverting oscillator amplifier.

2.7.13 Special Function Registers

A map of the on-chip memory area called the Special Function Register (SFR) space is

shown in Table 5-1. Note that not all of the addresses are occupied, and unoccupied

addresses may not be implemented on the chip. Read accesses to these addresses will in

general return random data, and write accesses will have an indeterminate effect. User

software should not write 1s to these unlisted locations, since they may be used in future

products to invoke new features. In that case, the reset or inactive values of the new bits

will always be 0.

Timer 2 Registers:

Control and status bits are contained in registers T2CON (shown in Table 5- 2) and

T2MOD (shown in Table 10-2) for Timer 2. The register pair (RCAP2H, RCAP2L) are

the Capture/Reload registers for Timer 2 in 16-bit capture mode or 16-bit auto-reload

mode.

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.

Dual Data Pointer Registers:

To facilitate accessing both internal and external data memory, two banks of 16-bit Data

Pointer Registers are provided: DP0 at SFR address locations 82H-83H and DP1 at 84H-

85H. Bit DPS = 0 in SFR AUXR1 selects DP0 and DPS = 1 selects DP1. The user should

always initialize the DPS bit to the appropriate value before accessing the respective Data

Pointer Register. Power off flag: The Power Off Flag (POF) is located at bit 4 (PCON.4)

in the PCON SFR. POF is set to “1” during power up. It can be set and rest under

software control and is not affected by reset.

2.7.14 Memory Organization

39


MCS-51 devices have a separate address space for Program and Data Memory. Up to

64K bytes each of external Program and Data Memory can be addressed.

2.7.15 Program Memory

If the EA pin is connected to GND, all program fetches are directed to external memory.

On the AT89S52, if EA is connected to VCC, program fetches to addresses 0000H

through 1FFFH are directed to internal memory and fetches to addresses 2000H through

FFFFH are to external memory.

2.7.16 Data Memory

The AT89S52 implements 256 bytes of on-chip RAM. The upper 128 bytes occupy a

parallel address space to the Special Function Registers. This means that the upper 128

bytes have the same addresses as the SFR space but are physically separate from SFR

space. When an instruction accesses an internal location above address 7FH, the address

mode used in the instruction specifies whether the CPU accesses the upper 128 bytes of

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

For example, the following direct addressing instruction accesses the SFR at location

0A0H (which is P2). MOV 0A0H, #data Instructions that use indirect addressing access

the upper 128 bytes of RAM. For example, the following indirect addressing instruction,

where R0 contains 0A0H, accesses the data byte at address 0A0H, rather than P2 (whose

address is 0A0H). MOV @R0, #data Note that stack operations are examples of indirect

addressing, so the upper 128 bytes of data RAM are available as stack space.[7][8]

40


Chapter 3

Transmitting and Receiving Sections

3.1 RF module introduction

An RF Module is a (usually) small electronic circuit used to transmit, receive, or

transceiver radio waves on one of a number of carrier frequencies. RF Modules are

widely used in consumer application such as garage door openers, wireless alarm

systems, industrial remote controls, smart sensor applications, and wireless home

automation systems. They are often used instead of infrared remote controls as they have

the advantage of not requiring line-of-sight operation. Several carrier frequencies are

commonly used in commercially-available RF modules, including 433.92MHz, 315MHz,

868MHz and 915MHz.

There are two types of RF receiver modules: super heterodyne receiver and super-

regenerative receiver. Super heterodyne has performance advantage over Super-

regenerative ones, but also is more complicated and in general the price is a little higher.

When attaching an external antenna to an RF Module, superior performance can

be achieved by selecting an antenna length related to the wavelength of the carrier

frequency. For a 315MHz Module, use a 24 cm antenna length, while for a 433.92 MHz,

use a 18 cm antenna.

As with any other radio-frequency device, the performance of an RF Module will

depend on a number of factors. For example, by increasing the transmitter power, a larger

communication distance will be achieved. However, this will also result in a higher

electrical power drain on the transmitter device, which will cause shorter operating life

for battery powered devices. Also, using a higher transmit power will make the system

more prone to interference with other RF devices, and may in fact possibly cause the

device to become illegal depending on the jurisdiction.

Correspondingly, increasing the receiver sensitivity will also increase the effective

communication range, but will also potentially cause malfunction due to interference with

other RF devices.

The performance of the overall system may be improved by using matched antennas at

each end of the communication link, such as those described earlier.

Finally, the labeled remote distance of any particular system is normally measured

in an open-air line of sight configuration without any interference, but often there will be

41

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


obstacles such as walls, floors to absorb the radio wave signals, so the effective

operational distance will in most practical instances be less than specified.

The RF module is divided into two parts:-

Transmitter

Receiver

3.2 RF Transmitter

A Transmitter or radio transmitter is an electronic device which, with the aid of an

antenna, produces radio waves. The transmitter itself generates a radio frequency

alternating current, which is applied to the antenna. When excited by this alternating

current, the antenna radiates radio waves. The term transmitter is often abbreviated

"XMTR" or "TX" in technical documents. The Transmitter used here is 315/434 MHz

ASK TRANSMITTER

3.2.1 PIN Description

Figure: 3.1 ST-TX-01-ASK Transmitter

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

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

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


http://en.wikipedia.org/wiki/Antenna_(radio)

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


ANT:Not connected

VCC : Connected with supply voltage

Data: Connected with output pins of encoder

GND: Use for ground connection

3.2.2General Description

The ST-TX01-ASK is an ASK Hybrid transmitter module. ST-TX01-ASK is designed by

the Saw Resonator, with an effective low cost, small size, and simple-to-use for

designing. Frequency Range: 315 / 433.92 MHZ Supply Voltage: 3~12V. ,Output Power:

4~16dBm and Circuit Shape is Saw .

3.3 Circuit diagram of Transmitting port

Figure: 3.2 Circuit diagram of transmitting port

3.3.1 Detail working of Transmitter port

Figure 3.2 shows a circuit diagram of a transmitter port, as shown in a figure here we use

four switch , the one terminal of each switch is connected with a voltage regulated power

supply and another one is with the input terminal of encoder ic by the help of 1k

43


resistance in a parallel manner , when a switch is pressed in a room a signal is transmit to

the encoder ,the encoder take data coming from each switch in a parallel manner and

convert the parallel data input into serial manner and transmit it to the RF transmitter(Rx

433) in a serial manner.

3.4 RF receiver module

A Radio Receiver is an electronic device that receives radio waves and converts the

information carried by them to a usable form. It is used with an antenna. The antenna

intercepts radio waves (electromagnetic waves) and converts them to tiny alternating

currents which are applied to the receiver, and the receiver extracts the desired

information. The receiver uses electronic filters to separate the wanted radio frequency

signal from all other signals, an electronic amplifier to increase the power of the signal for

further processing, and finally recovers the desired information through demodulation.

3.4.1General description:

The ST-RX02-ASK is an ASK Hybrid receiver module. It is an effective low cost

solution for using at 315/433.92 MHZ. The circuit shape of ST-RX02-ASK is L/C. The

Receiver Frequency: 315 / 433.92 MHZ Typical sensitivity of receiver is of 105dBm.and

supply Current: 3.5mA With IF frequency of 1MHz

Figure3.3 Pin diagram of ST-RX02-ASK

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

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

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

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



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

http://en.wikipedia.org/wiki/Antenna_(radio)



Circuit diagram of receiver port

Figure3.4 Circuit diagram of receiver port

45


3.4.2 Detail working description of receiving port

Rx433 is a four terminal device in which two are used to transmit data to the decoder

one is grounded and another one is connected with the power supply of +5 volt which is

provided by a voltage regulator IC 7805 .The entire data will receive serially by a decoder

ic at pin number 14,pin number 17 is connected with the LED which will turn on when

decoder receive signal from RX433 .The decoder convert the serial data input into the

parallel manner and transmit it to the pin number 1,2,3,4 of microcontroller 89S52

IC .Pin number nine is connected with a switch which will present at receiver site the

receiver will use this switch to clear the message present on LCD screen and reset the lcd

screen to the initial stage. Now the input which is receive by a microcontroller through

decoder will be transmit to the LCD display from pin 32 to pin 39 of microcontroller to

the pin number 3 to pin number 10 of a LCD screen, and a message will display on a

screen. Pin number 24 of a microcontroller is connected with buzzer, which will produce

a beep sound when a message is display on a LCD screen.

3.5 LCD

A liquid crystal display (LCD) is a flat panel display, electronic visual display, or video

display that uses the light modulating properties of liquid crystals (LCs). LCs do not emit

light directly.LCDs have replaced cathode ray tube (CRT) displays in most applications.

They are available in a wider range of screen sizes than CRT and plasma displays, and

since they do not use phosphors, they cannot suffer image burn-in. LCDs are, however,

susceptible to image persistence.

3.5.1 Reason to use 16x2 LCD display

1. To display a request at receiver

2. Cheap

3. Easy to interface with microcontroller

LCD (Liquid Crystal Display) screen is an electronic display module and find a

wide range of applications. A 16x2 LCD display is very basic module and is very

commonly used in various devices and circuits. These modules are preferred over seven

segments and other multi segment LEDs. The reasons being: LCDs are economical;

easily programmable; have no limitation of displaying special & even custom characters

(unlike in seven segments), animations and so on.

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

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

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

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

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

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

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

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


A 16x2 LCD means it can display 16 characters per line and there are 2 such lines.

In this LCD each character is displayed in 5x7 pixel matrix. This LCD has two registers,

namely, Command and Data.

Figure3.5 Pin diagram of 16x2 LCD

The command register stores the command instructions given to the LCD. A

command is an instruction given to LCD to do a predefined task like initializing it,

clearing its screen, setting the cursor position, controlling display etc. The data register

stores the data to be displayed on the LCD. The data is the ASCII value of the character

to be displayed on the LCD.

47


3.5.2 Pin Description

Pin

No Function Name

1 Ground (0V) Ground

2 Supply voltage; 5V (4.7V – 5.3V) Vcc

3 Contrast adjustment; through a variable resistor VEE

4 Selects command register when low; and data

register when high

Register

Select

5 Low to write to the register; High to read from the

register

Read/write

6 Sends data to data pins when a high to low pulse is

given

Enable

7

8-bit data pins

DB0

8 DB1

9 DB2

10 DB3

11 DB4

12 DB5

13 DB6

14 DB7

15 Backlight VCC (5V) Led+

16 Backlight Ground (0V) Led-

Table3.1

48


CHAPTER 4

ENCODER AND DECODER

4.1Reason to use encoder and decoder

As we are working on a wireless system so coding and decoding of data is necessary for

security purpose, which can only perform by an encoder and a decoder.

4.2 Introduction of encoder IC used

HT12E is an encoder integrated circuit of 212 series of encoders. They are paired with 212

series of decoders for use in remote control system applications. It is mainly used in

interfacing RF and infrared circuits. The chosen pair of encoder/decoder should have

same number of addresses and data format.

Simply put, HT12E converts the parallel inputs into serial output. It encodes the

12 bit parallel data into serial for transmission through an RF transmitter. These 12 bits

are divided into 8 address bits and 4 data bits. HT12E has a transmission enable pin

which is active low. When a trigger signal is received on TE pin, the programmed

addresses/data are transmitted together with the header bits via an RF or an infrared

transmission medium. HT12E begins a 4-word transmission cycle upon receipt of a

transmission enable. This cycle is repeated as long as TE is kept low. As soon as TE

returns to high, the encoder output completes its final cycle and then stops.

4.2.1Features

Operating voltage=-2.4 to12volt

Low power and high noise immunity

Low standby current(0.1 micro ampere at 5volt)

Minimum four words can be coded at a time

Minimum transmission word- Four words for the HT12E

Built-in oscillator needs only 5% resistor

Data code has positive polarity

Minimal external components

HT12E: 18-pin DIP/20-pin SOP package

49


Figure4.1 Block diagram of encoder IC HT12E

50


Figure 4.2 Pin diagram of HT12E

51


4.2.2 Description of pin diagram

Pin

No

Function Name

1

8 bit Address pins for input

A0

2 A1

3 A2

4 A3

5 A4

6 A5

7 A6

8 A7


10

4 bit Data/Address pins for input

AD0

11 AD1

12 AD2

13 AD3

14 Transmission enable; active low TE

15 Oscillator input Osc2

16 Oscillator output Osc1

17 Serial data output Output

18 Supply voltage; 5V (2.4V-12V) Vcc

Table 4.1

4.3 Introduction of decoder IC used

52


HT12D is a decoder integrated circuit that belongs to 212 series of decoders. This series of

decoders are mainly used for remote control system applications, like burglar alarm, car

door controller, security system etc. It is mainly provided to interface RF and infrared

circuits. They are paired with 212 series of encoders. The chosen pair of encoder/decoder

should have same number of addresses and data format.

In simple terms, HT12D converts the serial input into parallel outputs. It decodes

the serial addresses and data received by, say, an RF receiver, into parallel data and sends

them to output data pins. The serial input data is compared with the local addresses three

times continuously. The input data code is decoded when no error or unmatched codes are

found. A valid transmission in indicated by a high signal at VT pin.

HT12D is capable of decoding 12 bits, of which 8 are address bits and 4 are data

bits. The data on 4 bit latch type output pins remain unchanged until new is received.

4.3.1Features

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

HT12D: 8 address bits and 4 data bits


Easy interface with an RF or an infrared transmission medium


Valid transmission indicator

Pair with Holtek’s 212 series of encoders

18-pin DIP, 20-pin SOP package

53


Figure 4.3 Block diagram of HT12D decoder

54


Figure4.4 Pin diagram of HT12D decoder IC

55


4.3.2 Pin description

Pin

No

Function Name

1

8 bit Address pins for input

A0

2 A1

3 A2

4 A3

5 A4

6 A5

7 A6

8 A7


10

4 bit Data/Address pins for output

D0

11 D1

12 D2

13 D3

14 Serial data input Input

15 Oscillator output Osc2

16 Oscillator input Osc1

17 Valid transmission; active high VT

18 Supply voltage; 5V (2.4V-12V) Vcc

Table4.2

56


CHAPTER 5

HARDWARE IMPLEMENTATION OF CIRCUIT

5.1 Introduction

A hardware implementation means that the job is done using a physical device or

electronic circuit as opposed to being done by a computer program. A hardware

implementation often takes longer to create and that can make it more expensive. It is

usually faster in operation and has the advantage that once built it cannot easily be

tampered with or reprogrammed.

In this project , we consider basically two ports which are transmitter and receiver.

First of all we take transmitter part, for it a zero pcb is required on which we mount

various components like four push switches, Encoder ic, transmitting module ,Led..After

this we connect the required components by connecting wires with the help of data sheets

and circuit diagram drawn on a page and connections are performed by the help of a

solder we will perform a neat and clean connections on a zero pcb which is also known as

general pcb with various precautions.

The circuit diagram and hardware implementation of transmitting and receiving

port are shown as below:

5.2 Circuit diagram of transmitter port

Figure5.2 Circuit diagram of transmitter port

57


5.3 Implementation of transmitter port circuit diagram

Figure 5.3 Implementation of transmitter port circuit diagram

58


5.4 Circuit diagram of receiver port

Figure5.4 Circuit diagram of receiver port

59


5.5Implementation of receiver port circuit diagram

Figure5.5Implementation of receiver port circuit diagram

60


Data sheets

Microcontroller 89S52

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

• 256 x 8-bit Internal RAM

• 32 Programmable I/O Lines

• Three 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

Description

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

8K bytes of in-system programmable Flash memory. The device is manufactured using

Atmel’s high-density non-volatile memory technology and is compatible with the

industry- standard 80C51 instruction set and pin out. The on-chip Flash allows the

program memory to be reprogrammed in-system or by a conventional non-volatile

memory programmer.

By combining a versatile 8-bit CPU with in-system programmable Flash on a

monolithic chip, the Atmel AT89S52 is a powerful microcontroller which provides a

highly-flexible and cost-effective solution to many 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

61


timer/counters, a six-vector two-level interrupt architecture, a 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.

Special Function Registers

A map of the on-chip memory area called the Special Function Register (SFR).

Note that not all of the addresses are occupied, and unoccupied addresses may not be

implemented on the chip. Read accesses to these addresses will in general return random

data, and write accesses will have an indeterminate effect.

User software should not write 1s to these unlisted locations, since they may be

used in future products to invoke new features. In that case, the reset or inactive values of

the new bits will always be 0.

Timer 2 Registers

Control and status bits are contained in registers T2CON and T2MOD for Timer

2. The register pair (RCAP2H, RCAP2L) are the Capture/Reload registers for Timer 2 in

16-bit capture mode or 16-bit auto-reload mode. 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.

Dual Data Pointer Registers

To facilitate accessing both internal and external data memory, two banks of 16-

bit Data Pointer Registers are provided: DP0 at SFR address locations 82H-83H and DP1

at 84H-85H. Bit DPS = 0 in SFR AUXR1 selects DP0 and DPS = 1 selects DP1. The user

should always initialize the DPS bit to the appropriate value before accessing the

respective Data Pointer Register.

Power off Flag

The Power Off Flag (POF) is located at bit 4 (PCON.4) in the PCON SFR. POF

is set to “1” during power up. It can be set and rest under software control and is not

affected by reset.

Memory Organization

62


MCS-51 devices have a separate address space for Program and Data Memory. Up

to 64K bytes each of external Program and Data Memory can be addressed. Program

Memory If the EA pin is connected to GND, all program fetches are directed to external

memory. On the AT89S52, if EA is connected to VCC, program fetches to addresses

0000H through 1FFFH are directed to internal memory and fetches to addresses 2000H

through FFFFH are to external memory. Data Memory The AT89S52 implements 256

bytes of on-chip RAM. The upper 128 bytes occupy a parallel address space to the

Special Function Registers. This means that the upper 128 bytes have the same addresses

as the SFR space but are physically separate from SFR space. When an instruction

accesses an internal location above address 7FH, the address mode used in the instruction

specifies whether the CPU accesses the upper 128 bytes of RAM or the SFR space.

Instructions which use direct addressing access of the SFR space.

For example, the following direct addressing instruction accesses the SFR at

location 0A0H (which is P2).MOV 0A0H, #data Instructions that use indirect addressing

access the upper 128 bytes of RAM. For example, the following indirect addressing

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

P2 (whose address is 0A0H).

MOV @R0, #data

Note that stack operations are examples of indirect addressing, so the upper 128

bytes of data RAM are available as stack space.

Watchdog Timer

(One-time Enabled with Reset-out)

The WDT is intended as a recovery method in situations where the CPU may be

subjected to software upsets. The WDT consists of a 13-bit counter and the Watchdog

Timer Reset (WDTRST) SFR. The WDT is defaulted to disable from exiting reset. To

enable the WDT, a user must write 01EH and 0E1H in sequence to the WDTRST register

(SFR location 0A6H). When the WDT is enabled, it will increment every machine cycle

while the oscillator is running. The WDT timeout period is dependent on the external

clock frequency. There is no way to disable the WDT except through reset (either

hardware reset or WDT overflow reset). When WDT overflows, it will drive an output

RESET HIGH pulse at the RST pin.

Using the WDT To enable the WDT, a user must write 01EH and 0E1H in

sequence to the WDTRST register (SFR location 0A6H). When the WDT is enabled, the

63


user needs to service it by writing 01EH and 0E1H to WDTRST to avoid a WDT

overflow. The 13-bit counter overflows when it reaches 8191 (1FFFH), and this will reset

the device. When the WDT is enabled, it will increment every machine cycle while the

oscillator is running. This means the user must reset the WDT at least every 8191

machine cycles. To reset the WDT the user must write 01EH and 0E1H to WDTRST.

WDTRST is a write-only register. The WDT counter cannot be read or written. When

WDT overflows, it will generate an output RESET pulse at the RST pin. The RESET

pulse duration is 96xTOSC, where TOSC=1/FOSC. To make the best use of the WDT, it

should be serviced in those sections of code that will periodically be executed within the

time required to prevent a WDT reset. WDT During Power-down and Idle In Power-

down mode the oscillator stops, which means the WDT also stops. While in Power-down

mode, the user does not need to service the WDT. There are two methods of exiting

Power-down mode: by a hardware reset or via a level-activated external interrupt which is

enabled prior to entering Power-down mode. When Power-down is exited with hardware

reset, servicing the WDT should occur as it normally does whenever the AT89S52 is

reset. Exiting Power-down with an interrupt is significantly different. The interrupt is held

low long enough for the oscillator to stabilize.

When the interrupt is brought high, the interrupt is serviced. To prevent the WDT

from resetting the device while the interrupt pin is held low, the WDT is not started until

the interrupt is pulled high. It is suggested that the WDT be reset during the interrupt

service for the interrupt used to exit Power-down mode. To ensure that the WDT does not

overflow within a few states of exiting Power-down, it is best to reset the WDT just

before entering Power-down mode. Before going into the IDLE mode, the WDIDLE bit

in SFR AUXR is used to determine whether the WDT continues to count if enabled. The

WDT keeps counting during IDLE (WDIDLE bit = 0) as the default state. To

prevent the WDT from resetting the AT89S52 while in IDLE mode, the user should

always set up a timer that will periodically exit IDLE, service the WDT, and reenter

IDLE mode. With WDIDLE bit enabled, the WDT will stop to count in IDLE mode and

resumes the count upon exit from IDLE. UART The UART in the AT89S52 operates the

same way as the UART in the AT89C51 and AT89C52..

Timer 0 and 1

64


Timer 0 and Timer 1 in the AT89S52 operate the same way as Timer 0 and Timer 1 in

the AT89C51 and AT89C52.). From the home page, select ‘Products’, then ‘8051-

Architecture Flash Microcontroller’, then ‘Product Overview’.

Timer 2

Timer 2 is a 16-bit Timer/Counter that can operate as either a timer or an event

counter. The type of operation is selected by bit C/T2 in the SFR T2CON. Timer 2 has

three operating modes: capture, auto-reload (up or down counting), and baud rate

generator. The modes are selected by bits in T2CON, as shown in Table 3.

Timer 2 consists of two 8-bit registers, TH2 and TL2. In the Timer function, the TL2

register is incremented every machine cycle. Since a machine cycle consists of 12

oscillator periods, the count rate is 1/12 of the oscillator frequency.

Interrupts

The AT89S52 has a total of six interrupt vectors: two external interrupts (INT0 and

INT1), three timer interrupts (Timers 0, 1, and 2), and the serial port interrupt. These

interrupts are all shown in Figure 10. Each of these interrupt sources can be individually

enabled or disabled by setting or clearing a bit in Special Function Register IE. IE also

contains a global disable bit, EA, which disables all interrupts at once. Note that Table 5

shows that bit position IE.6 is unimplemented. In the AT89S52, bit position IE.5 is also

unimplemented. User software should not write 1s to these bit positions, since they may

be used in future AT89 products. Timer 2 interrupt is generated by the logical OR of bits

TF2 and EXF2 in register T2CON. Neither of these flags is cleared by hardware when the

service routine is vectored to. In fact, the service routine may have to determine whether

it was TF2 or EXF2 that generated the interrupt, and that bit will have to be cleared in

software. The Timer 0 and Timer 1 flags, TF0 and TF1, are set at S5P2 of the cycle in

which the timers overflow. The values are then polled by the circuitry in the next cycle.

However, the Timer 2 flag, TF2, is set at S2P2 and is polled in the same cycle in which

the timer overflows.

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 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, There are no requirements on the duty cycle

of the external clock signal, since the input to the internal clocking circuitry

65


is through a divide-by-two flip-flop, but minimum and maximum voltage high and low

time specifications must be observed.

Idle Mode

In idle mode, the CPU puts itself to sleep while all the on chip peripherals remain

active. The mode is invoked by software. The content of the on-chip RAM and all the

special functions registers remain unchanged during this mode. The idle mode can be

terminated by any enabled interrupt or by a hardware reset.

Note that when idle mode is terminated by a hardware reset, the device normally

resumes program execution from where it left off, up to two machine cycles before the

internal reset algorithm takes control. On-chip hardware inhibits access to internal RAM

in this event, but access to the port pins is not inhibited. To eliminate the possibility of

an unexpected write to a port pin when idle mode is terminated

by a reset, the instruction following the one that invokes idle mode should not write to a

port pin or to external memory.

Power-down Mode

In the Power-down mode, the oscillator is stopped, and the instruction that invokes

Power-down is the last instruction executed. The on-chip RAM and Special Function

Registers retain their values until the Power-down mode is terminated. Exit from Power-

down mode can be initiated either by a hardware reset or by an enabled external interrupt.

Reset redefines the SFRs but does not change the on-chip RAM. The reset should not be

activated before VCC is restored to its normal operating level and must be held active

long enough to allow the oscillator to restart and stabilize.

66


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 38kHz

carrier for infrared systems.

Features

• Operating voltage 2.4V~12V for the HT12E

• Low power and high noise immunity CMOS technology

• Low standby current: 0.1_A (typ.) at

• VDD=5V

• HT12A with a 38kHz carrier for infrared transmission medium

• Minimum transmission word=Four words for the HT12E

• Built-in oscillator needs only 5% resistor

• Data code has positive polarity

• Minimal external components

• HT12E: 18-pin DIP/20-pin SOP package

Applications

• Burglar alarm system

• Smoke and fire alarm system

• Garage door controllers

• Car door controllers

• Car alarm system

• Security system

• Cordless telephones

67


Pin diagram and description

HT12D

68


General Description

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

applications. They are paired with Holtek_s 212 series of encoders (refer to the

encoder/decoder cross reference table). For proper operation, a pair of encoder/decoder

with the same number of addresses and data format should be chosen.

The decoders receive serial addresses 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 informations that consist 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, and HT12F is used to decode 12 bits of address information.

Features

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

HT12D: 8 address bits and 4 data bits


Valid transmission indicator

Easy interface with an RF or an infrared transmission medium


Pair with Holtek_s 212 series of encoders

18-pin DIP, 20-pin SOP package

Applications

69


Burglar alarm system

Smoke and fire alarm system

Garage door controllers

Car door controllers

Car alarm system

Security system

Cordless telephones

Other remote control systems

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 receive data

that are transmitted by an encoder and interpret the first N bits of code period as addresses

and the last 12_N bits as data, where N is the address code number. The decoders will

then check the received address three times continuously. If the received address codes all

match the contents of the decoder 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 received.

70


71


72


ASK Transmitter Module

General Description: ST-TX01-ASK(Saw Type)

The ST-TX01-ASK is an ASK Hybrid transmitter module.ST-TX01-ASK is designed by

the Saw Resonator, with an effective low cost, small size, and simple-to-use for

designing.

Frequency Range:315 / 433.92 MHZ.

Supply Voltage: 3~12V.

Output Power : 4~16dBm

Circuit Shape: Saw

Applications

Wireless security systems

Car Alarm systems

Remote controls.

Sensor reporting

73


Crystal OscillatorIt is often required to produce a signal whose frequency or pulse rate is very stable

and exactly known. This is important in any application where anything to do with time

or exact measurement is crucial. It is relatively simple to make an oscillator that produces

some sort of a signal, but another matter to produce one of relatively precise frequency

and stability. AM radio stations must have a carrier frequency accurate within 10Hz of its

assigned frequency, which may be from 530 to 1710 kHz. SSB radio systems used in the

HF range (2-30 MHz) must be within 50 Hz of channel frequency for acceptable voice

quality, and within 10 Hz for best results. Some digital modes used in weak signal

communication may require frequency stability of less than 1 Hz within a period of

several minutes. The carrier frequency must be known to fractions of a hertz in some

cases. An ordinary quartz watch must have an oscillator accurate to better than a few parts

per million. One part per million will result in an error of slightly less than one half

second a day, which would be about 3 minutes a year. This might not sound like much,

but an error of 10 parts per million would result in an error of about a half an hour per

year. A clock such as this would need resetting about once a month, and more often if you

are the punctual type. A programmed VCR with a clock this far off could miss the

recording of part of a TV show. Narrow band SSB communications at VHF and UHF

frequencies still need 50 Hz frequency accuracy. At 440 MHz, this is slightly more than

0.1 part per million.

Ordinary L-C oscillators using conventional inductors and capacitors can achieve

typically 0.01 to 0.1 percent frequency stability, about 100 to 1000 Hz at 1 MHz. This is

OK for AM and FM broadcast receiver applications and in other low-end analog receivers

not requiring high tuning accuracy. By careful design and component selection, and with

rugged mechanical construction, .01 to 0.001%, or even better (.0005%) stability can be

achieved. The better figures will undoubtedly employ temperature compensation

components and regulated power supplies, together with environmental control (good

ventilation and ambient temperature regulation) and “battleship” mechanical construction.

This has been done in some communications receivers used by the military and

commercial HF communication receivers built in the 1950-1965 era, before the

widespread use of digital frequency synthesis. But these receivers were extremely

expensive, large, and heavy. Many modern consumer grade AM, FM, and shortwave

receivers employing crystal controlled digital frequency synthesis will do as well or better

from a frequency stability standpoint.

74


An oscillator is basically an amplifier and a frequency selective feedback network (Fig 1).

When, at a particular frequency, the loop gain is unity or more, and the total phaseshift at

this frequency is zero, or some multiple of 360 degrees, the condition for oscillation is

satisfied, and the circuit will produce a periodic waveform of this frequency. This is

usually a sine wave, or square wave, but triangles, impulses, or other waveforms can be

produced. In fact, several different waveforms often are simultaneously produced by the

same circuit, at different points. It is also possible to have several frequencies produced as

well, although this is generally undesirable.

Capacitor

A capacitor or condenser is a passive electronic component consisting of a pair of

conductors separated by a dielectric (insulator). When a potential difference (voltage)

exists across the conductors, an electric field is present in the dielectric. This field stores

energy and produces a mechanical force between the conductors. The effect is greatest

when there is a narrow separation between large areas of conductor, hence capacitor

conductors are often called plates.

An ideal capacitor is characterized by a single constant value, capacitance, which

is measured in farads. This is the ratio of the electric charge on each conductor to the

potential difference between them. In practice, the dielectric between the plates passes a

small amount of leakage current. The conductors and leads introduce an equivalent series

resistance and the dielectric has an electric field strength limit resulting in a breakdown

voltage.Capacitors are widely used in electronic circuits to block the flow of direct

current while allowing alternating current to pass, to filter out interference, to smooth the

output of power supplies, and for many other purposes. They are used in resonant circuits

in radio frequency equipment to select particular frequencies from a signal with many

frequencies.

Figure 5.6.1: Types of capacitors

75

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

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

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


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

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

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

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

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

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

http://en.wikipedia.org/wiki/Lead_(electronics)

http://en.wikipedia.org/wiki/Leakage_(electronics)

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

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

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

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

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

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

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

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

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

http://en.wikipedia.org/wiki/Passivity_(engineering)


Theory of operation

Figure 5.6.2: principle of working of capacitor

Charge separation in a parallel-plate capacitor causes an internal electric field. A

dielectric (orange) reduces the field and increases the capacitance.

Figure5.6.3: A simple demonstration of a parallel-plate capacitor

A capacitor consists of two conductors separated by a non-conductive region.The

non-conductive substance is called the dielectric medium, although this may also mean a

vacuum or a semiconductor depletion region chemically identical to the conductors. A

capacitor is assumed to be self-contained and isolated, with no net electric charge and no

influence from an external electric field. The conductors thus contain equal and opposite

charges on their facing surfaces, and the dielectric contains an electric field. The capacitor

is a reasonably general model for electric fields within electric circuits.

An ideal capacitor is wholly characterized by a constant capacitance C, defined as the

ratio of charge ±Q on each conductor to the voltage V between them

76

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

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

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

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

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

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


Sometimes charge buildup affects the mechanics of the capacitor, causing the capacitance

to vary. In this case, capacitance is defined in terms of incremental changes:

In SI units, a capacitance of one farad means that one coulomb of charge on each

conductor causes a voltage of one volt across the device.

Energy storage

Work must be done by an external influence to move charge between the

conductors in a capacitor. When the external influence is removed, the charge separation

persists and energy is stored in the electric field. If charge is later allowed to return to its

equilibrium position, the energy is released. The work done in establishing the electric

field, and hence the amount of energy stored, is given by:

Resistor

Resistors are used to limit the value of current in a circuit. Resistors offer

opposition to the flow of current. They are expressed in ohms for which the symbol is

‘’. Resistors are broadly classified as

1. Fixed Resistors

2. Variable Resistors

Fixed Resistors

The most common of low wattage, fixed type resistors is the molded-carbon

composition resistor. The resistive material is of carbon clay composition. The leads are

made of tinned copper. Resistors of this type are readily available in value ranging from

few ohms to about 20M, having a tolerance range of 5 to 20%. They are quite

inexpensive. The relative size of all fixed resistors changes with the wattage rating.

Another variety of carbon composition resistors is the metalized type. It is made by

deposition a homogeneous film of pure carbon over a glass, ceramic or other insulating

core. This type of film-resistor is sometimes called the precision type, since it can be

obtained with an accuracy of 1%.

77

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

http://en.wikipedia.org/wiki/Work_(thermodynamics)

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

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

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

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


A variable/ wire wound resistor

It uses a length of resistance wire, such as nichrome. This wire is wounded on to a

round hollow porcelain core. The ends of the winding are attached to these metal pieces

inserted in the core. Tinned copper wire leads are attached to these metal pieces. This

assembly is coated with an enamel coating powdered glass. This coating is very smooth

and gives mechanical protection to winding.

Connectors

Connectors are basically used for interface between two. Here we use connectors

for having interface between PCB and 8051 Microprocessor Kit.

There are two types of connectors they are male and female. The one, which is with pins

inside, is female and other is male.

These connectors are having bus wires with them for connection.

For high frequency operation the average circumference of a coaxial cable must

be limited to about one wavelength, in order to reduce multimodal propagation and

eliminate erratic reflection coefficients, power losses, and signal distortion. The

standardization of coaxial connectors during World War II was mandatory for microwave

operation to maintain a low reflection coefficient or a low voltage standing wave ratio.

Seven types of microwave coaxial connectors are as follows:

1.APC-3.5

2.APC-7

3.BNC

4.SMA

5.SMC

6.TNC

7.Type N

LED (Light Emitting Diode)

A junction diode, such as LED, can emit light or exhibit electro luminescence.

Electro luminescence is obtained by injecting minority carriers into the region of a pn

junction where radiative transition takes place. In radiative transition, there is a transition

of electron from the conduction band to the valence band, which is made possibly by

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emission of a photon. Thus, emitted light comes from the hole electron recombination.

What is required is that electrons should make a transition from higher energy level to

lower energy level releasing photon of wavelength corresponding to the energy difference

associated with this transition. In LED the supply of high-energy electron is provided by

forward biasing the diode, thus injecting electrons into the n-region and holes into p-

region.

The pn junction of LED is made from heavily doped material. On forward bias

condition, majority carriers from both sides of the junction cross the potential barrier and

enter the opposite side where they are then minority carrier and cause local minority

carrier population to be larger than normal. This is termed as minosrity injection. These

excess minority carrier diffuse away from the junction and recombine with majority

carriers.

In LED, every injected electron takes part in a radiative recombination and hence

gives rise to an emitted photon. Under reverse bias no carrier injection takes place and

consequently no photon is emitted. For direct transition from conduction band to valence

band the emission wavelength.

In practice, every electron does not take part in radiative recombination and hence,

the efficiency of the device may be described in terms of the quantum efficiency which is

defined as the rate of emission of photons divided by the rate of supply of electrons. The

number of radiative recombination, that take place, is usually proportional to the carrier

injection rate and hence to the total current flowing.

LED Materials

One of the first materials used for LED is GaAs. This is a direct band gap

material, i.e., it exhibits very high probability of direct transition of electron from

conduction band to valence band. GaAs has E= 1.44 eV. This works in the infrared

region.

Gallium Arsenide Phosphide is a tertiary alloy. This material has a special feature in that

it changes from being direct band gap material.

Blue LEDs are of recent origin. The wide band gap materials such as GaN are one of the

most promising LEDs for blue and green emission. Infrared LEDs are suitable for optical

coupler applications.

Advantages of LEDS

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Low operating voltage, current, and power consumption makes Led’s compatible with

electronic drive circuits. This also makes easier interfacing as compared to filament

incandescent and electric discharge lamps.

The rugged, sealed packages developed for LEDs exhibit high resistance to

mechanical shock and vibration and allow LEDs to be used in severe environmental

conditions where other light sources would fail.LED fabrication from solid-state materials

ensures a longer operating lifetime, thereby improving overall reliability and lowering

maintenance costs of the equipment in which they are installed.

The range of available LED colours-from red to orange, yellow, and green-

provides the designer with added versatility. LEDs have low inherent noise levels and

also high immunity to externally generated noise. Circuit response of LEDs is fast and

stable, without surge currents or the prior “warm-up”, period required by filament light

sources.

LEDs exhibit linearity of radiant power output with forward current over a wide range.

Limitations of LED

Temperature dependence of radiant output power and wave length.

Sensitivity to damages by over voltage or over current.

Theoretical overall efficiency is not achieved except in special cooled or pulsed

conditions.

Buzzer

It is an electronic signaling device which produces buzzing sound. It is commonly

used in automobiles, phone alarm systems and household appliances. Buzzers work in the

same manner as an alarm works. They are generally equipped with sensors or switches

connected to a control unit and the control unit illuminates a light on the appropriate

button or control panel, and sound a warning in the form of a continuous or intermittent

buzzing or beeping sound.

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The word "buzzer" comes from the rasping noise that buzzers made when they

were electromechanical devices, operated from stepped-down AC line voltage at 50 or 60

cycles.

Typical uses of buzzers and beepers include alarms, timers and confirmation of user input

such as a mouse click or keystroke.

Types of Buzzers

The different types of buzzers are electric buzzers, electronic buzzers, mechanical

buzzers, electromechanical, magnetic buzzers, piezoelectric buzzers and piezo buzzers.

(i) Electric buzzers –

A basic model of electric buzzer usually consists of simple circuit components

such as resistors, a capacitor and 555 timer IC or an integrated circuit with a range of

timer and multi-vibrator functions. It works through small bits of electricity vibrating

together which causes sound.

(ii) Electronic buzzers –

An electronic buzzer comprises an acoustic vibrator comprised of a circular metal

plate having its entire periphery rigidly secured to a support, and a piezoelectric element

adhered to one face of the metal plate. A driving circuit applies electric driving signals to

the vibrator to vibrationally drive it at a 1/N multiple of its natural frequency, where N is

an integer, so that the vibrator emits an audible buzzing sound. The metal plate is

preferably mounted to undergo vibration in a natural vibration mode having only one

nodal circle. The drive circuit includes an inductor connected in a closed loop with the

vibrator, which functions as a capacitor, and the circuit applies signals at a selectively

variable frequency to the closed loop to accordingly vary the inductance of the inductor to

thereby vary the period of oscillation of the acoustic vibrator and the resultant frequency

of the buzzing sound.

(iii) Mechanical Buzzer-

A joy buzzer is an example of a purely mechanical buzzer.

(iv) Piezo Buzzers/ Piezoelectric Buzzers-

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A piezo buzzer is made from two conductors that are separated by Piezo crystals. When a

voltage is applied to these crystals, they push on one conductor and pull on the other. The

result of this push and pull is a sound wave. These buzzers can be used for many things,

like signaling when a period of time is up or making a sound when a particular button has

been pushed. The process can also be reversed to use as a guitar pickup. When a sound

wave is passed, they create an electric signal that is passed on to an audio amplifier.

Piezo buzzers are small electronic devices that emit sounds when driven by low voltages

and currents. They are also called piezoelectric buzzers. They usually have two electrodes

and a diaphragm. The diaphragm is made from a metal plate and piezoelectric material

such as a ceramic plate.

(v) Magnetic Buzzers–

Magnetic buzzers are magnetic audible signal devices with built-in oscillating

circuits. The construction combines an oscillation circuit unit with a detection coil, a

drive coil and a magnetic transducer. Transistors, resistors, diodes and other small devices

act as circuit devices for driving sound generators. With the application of voltage,

current flows to the drive coil on primary side and to the detection coil on the secondary

side. The amplification circuit, including the transistor and the feedback circuit, causes

vibration. The oscillation current excites the coil and the unit generates an AC magnetic

field corresponding to an oscillation frequency. This AC magnetic field magnetizes the

yoke comprising the magnetic circuit. The oscillation from the intermittent magnetization

prompts the vibration diaphragm to vibrate up and down, generating buzzer sounds

through the resonator.

In this project, a magnetic buzzer has been used.

Circuit of buzzer –

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Role of buzzer in this project

Buzzer in this system gives the beep when car moves inside cutting the infrared light.

Basically it generates the signal to indicate that car has entered in the parking space.

Pressure Sensor/Switch

A pressure sensor or switch measures pressure. Pressure is usually expressed in terms of

force per unit area. A pressure sensor usually acts as a transducer; it generates a signal as

a function of the pressure imposed.

Pressure sensors can be classified in term of pressure ranges they measure, temperature

ranges of operation, and most importantly the type of pressure they measure. In terms of

pressure type, pressure sensors can be divided into five categories:

1) Absolute pressure sensor

This sensor measures the pressure relative to perfect vaccum pressure.

2) Gauge pressure sensor

This sensor is used in different applications because it can be calibrated to measure the

pressure relative to a given atmospheric pressure at a given location.

3) Vaccum pressure sensor

This sensor is used to measure pressure less than the atmospheric pressure at a given

location.

4) Differential pressure sensor

This sensor measures the difference between two or more pressures introduced as inputs

to the sensing unit.

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5) Sealed pressure sensor

This sensor is the same as the gauge pressure sensor except that it is previously calibrated

by manufacturers to measure pressure relative to sea level pressure.

Figure 5.6.4: Operation of pressure switch

Pressure Sensing Technology

There are two basic categories of analog pressure sensors:

(i) Force collector types - These types of electronic pressure sensors generally use a

force collector (such a diaphragm, piston, bourdon tube, or bellows) to measure strain (or

deflection) due to applied force (pressure) over an area.

(ii) Other types - These types of electronic pressure sensors use other properties (such as

density) to infer pressure of a gas, or liquid.

Here we’ll discuss only about Force collector type of pressure sensors. Force collecting

pressure sensors are of following types:

Piezoresistive Strain Gauge-

It uses the piezoresistive effect of bonded or formed strain gauges to detect strain due to

applied pressure. Generally, the strain gauges are connected to form a wheat stone bridge

circuit to maximize the output of the sensor. This is the most commonly employed

sensing technology for general purpose pressure measurement.

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Capacitive - Uses a diaphragm and pressure cavity to create a variable capacitor to detect

strain due to applied pressure. Common technologies use metal, ceramic, and silicon

diaphragms. Generally, these technologies are most applied to low pressures (Absolute,

Differential and Gauge)

Electromagnetic - Measures the displacement of a diaphragm by means of changes in

inductance (reluctance), LVDT, Hall Effect, or by eddy current principal.

Piezoelectric - Uses the piezoelectric effect in certain materials such as quartz to measure

the strain upon the sensing mechanism due to pressure. This technology is commonly

employed for the measurement of highly dynamic pressures.

Optical - Uses the physical change of an optical fiber to detect strain due to applied

pressure.

Potentiometric - Uses the motion of a wiper along a resistive mechanism to detect the

strain caused by applied pressure .

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APPENDIX

Introduction

Assembly language is a symbolic representation of a processor's native code. Using

machine code allows the programmer to control precisely what the processor does. It

offers a great deal of power to use all of the features of the processor. The resulting

program is normally very fast and very compact. In small programs it is also very

predictable. Timings, for example, can be calculated very precisely and program flow is

easily controlled. It is often used for small, real time applications.

However, the programmer needs to have a good understanding of the hardware being

used. As programs become larger, assembly language get very cumbersome. Maintenance

of assembly language is notoriously difficult, especially if another programmer is brought

in to carry out modifications after the code has been written. Assembly langauge also has

no support of an operating system, nor does it have any complex instructions. Storing and

retrieving data is a simple task with high level languages; assembly needs the whole

process to be programmed step by step. Mathematical processes also have to be

performed with binary addition and subtraction when using assembly which can get very

complex. Finally, every processor has its own assembly language. Use a new processor

and you need to learn a new language each time.

Assembly is a great language to use for certain applications, rotten for others and never

for the faint hearted.

In our project we divide the programming of microcontroller into four modules

that are as follows

1. Main program

2. Display function

3. LCD initialisation

4. Delay function

In the next article we describe the coding that we used in 89s52 microcontroller to run our

program.

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Coding of controller

ORG 00H

LJMP MAIN

/*----------------------------------------------

MAIN_PROGRAME_STARTS-------------------------------------*/

MAIN: MOV P1,#0FFH

CLR P2.5

ACALL LCD_INIT

HERE: MOV A,P1

CJNE A,#0FEH,NEXT1

ACALL ROOM1

NEXT1: CJNE A,#0FDH,NEXT2

ACALL ROOM2

NEXT2: CJNE A,#0FBH,NEXT3

ACALL ROOM3

NEXT3: CJNE A,#0F7H,NEXT4

ACALL ROOM4

NEXT4: SJMP HERE

/*----------------------------------------------

MAIN_PROGRAME_END-------------------------------------*/

/*----------------------------------------function to display-----------------------------------------*/

ROOM1: SETB P2.5

MOV A,#0C2H

ACALL COMNWRT

ACALL DELAY

CLR A

MOV DPTR,#MYDATA1

D2: CLR A

MOVC A,@A+DPTR

ACALL DATAWRT

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ACALL DELAY

INC DPTR

JZ L3

SJMP D2

L3: CLR P2.5

RET

ROOM2: SETB P2.5

MOV A,#0C4H

ACALL COMNWRT

ACALL DELAY

CLR A

MOV DPTR,#MYDATA2

D3: CLR A

MOVC A,@A+DPTR

ACALL DATAWRT

ACALL DELAY

INC DPTR

JZ L4

SJMP D3

L4: CLR P2.5

RET

ROOM3: SETB P2.5

MOV A,#0C6H

ACALL COMNWRT

ACALL DELAY

CLR A

MOV DPTR,#MYDATA3

D4: CLR A

MOVC A,@A+DPTR

ACALL DATAWRT

ACALL DELAY

INC DPTR

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JZ L5

SJMP D4

L5: CLR P2.5

RET

ROOM4: SETB P2.5

MOV A,#0C8H

ACALL COMNWRT

ACALL DELAY

CLR A

MOV DPTR,#MYDATA4

D5: CLR A

MOVC A,@A+DPTR

ACALL DATAWRT

ACALL DELAY

INC DPTR

JZ L6

SJMP D5

L6: CLR P2.5

RET

/*----------------------------------------function to display-----------------------------------------*/

/*-------------------------------------------LCD_INITIALIZATION_START-------------------

*/

LCD_INIT: MOV DPTR,#MYCOM

L1: CLR A

MOVC A,@A+DPTR

ACALL COMNWRT

ACALL DELAY

JZ SEND_DAT

INC DPTR

SJMP L1

SEND_DAT: MOV DPTR,#MYDATA0

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D1: CLR A

MOVC A,@A+DPTR

ACALL DATAWRT

ACALL DELAY

INC DPTR

JZ L2

SJMP D1

L2: MOV A,#0C2H

ACALL COMNWRT

ACALL DELAY

RET

COMNWRT: MOV P0,A

CLR P2.0

CLR P2.1

SETB P2.2

ACALL DELAY

CLR P2.2

RET

DATAWRT: MOV P0,A

SETB P2.0

CLR P2.1

SETB P2.2

ACALL DELAY

CLR P2.2

RET

/*-------------------------------------------LCD_INITIALIZATION_END----------------------*/

/*-------------------------------------------DELAY_START----------------------------------*/

DELAY: MOV R3,#250

H1: MOV R4,#255

H: DJNZ R4,H

DJNZ R3,H1

RET

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/*-------------------------------------------DELAY_END----------------------------------*/

ORG 300H

MYCOM: DB 38H,0EH,01,06,81H,0

MYDATA0: DB "HOTEL_MANAGMENT",0

MYDATA1: DB "1",0

MYDATA2: DB "2",0

MYDATA3: DB "3",0

MYDATA4: DB "4",0

END

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FUTURE SCOPE

To improve the efficiency of the project some changes can be done with this module.

Multitasking Multitask can be perform at a time means a particular message instead of

a request will be display on a board and also control various functions like status of

room and controlling of lights in a room. Remote sensing A remote is provided in

each room for transmitter port instead of a switch, to establish a link between remote

and RF transmitter. Recording An APR9 IC can be used which is used to record a

particular sound message instead of buzzer. Voice Decoder By using advance

technology, voice decoder, and direct voice command can be applied and used

optimally. Increase in Number of switches by using smart antenna and frequency

division multiplexing and large number of encoder-decoder circuitry, number of

request can be increases up to a large level. Use of GSM Technology By use of GSM

technology its efficiency can be increased further to a large amount.

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CONCLUSION

In comparison to other wireless transmitter and receiver systems, this wireless radio

frequency link is extremely low cost and easy to build. Many limitations exist, like the

need to limit the distance of transmitter and receiver is up to 100 meters, however even

with these limitations there are many applications for this type of wireless system. This

system showed you how easy and how standard digital communication can be passed

across the link. This was just a simple example, but it should be enough to get anyone

started for bigger and better things with wireless radio frequency link.

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References

[1] M. Schwartz, Information Transmission, Modulation, and Noise, 4/e, McGraw

Hill, 1990.

[2] P. Z. Peebles, Jr., Digital Communication Systems, Prentice Hall, 1987.

[3] Simon Haykin, "Digital Communications", John Wiley & Sons, 1988.

[4] Sergio Benedetto, Ezio Biglieri, "Principles of Digital Transmission: With

Wireless Applications",

[5] F. Egan, William (2003). Practical RF System Design. Wiley-IEEE Press

[6] Richard C. Dorf (ed.) The Electrical Engineering Handbook, CRC Press, Boca

Raton

[7] Mazedi, The 8051 Microcontroller and Embedded Systems, Prentice Hall, 1ST

Edition

[8] Kenneth J. Ayala, The 8051 Microcontroller, Penram International

Publishing,1996, 2nd Edition

[9] History of wireless, Robert Mallous, Dipak L.Sen Gupta

[10] Introduction to wireless systems, P. Mohana Shankar

[11] Pahlavan, Levesque, Allen H (1995). Wireless Information Networks.

John Wiley & Sons.

[12] Geier, Jim (2001). Wireless LANs. Sams

[13] Goldsmith, Andrea (2005). Wireless Communications. Cambridge

University Press.

[14] Molisch, Andreas (2005). Wireless Communications. Wiley-IEEE Press.

[15] Pahlavan, Kaveh; Krishnamurthy, Prashant (2002). Principles of Wireless

Networks - a Unified Approach. Prentice Hall.

[16] Rappaport, Theodore (2002). Wireless Communications: Principles and

Practice. Prentice Hall.

[17] Rhoton, John (2001). The Wireless Internet Explained. Digital Press.

[18] Tse, David; Viswanath, Pramod (2005). Fundamentals of Wireless

Communication. Cambridge University Press.

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Wireless Request Management System

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