wireless request management system
TRANSCRIPT
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
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WIRELESS REQUEST MANAGEMENT SYSTEM
[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]
WIRELESS REQUEST MANAGEMENT SYSTEM
Lecturer
Department of Electronics & Communication EngineeringAryabhatt College of Engineering & Technology, Baghpat
(U.P.)Gautam Buddh Technical University, Lucknow
May, 2012
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WIRELESS REQUEST MANAGEMENT SYSTEM
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unconditionally be withdrawn.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)
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WIRELESS REQUEST MANAGEMENT SYSTEM
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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WIRELESS REQUEST MANAGEMENT SYSTEM
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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WIRELESS REQUEST MANAGEMENT SYSTEM
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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WIRELESS REQUEST MANAGEMENT SYSTEM
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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WIRELESS REQUEST MANAGEMENT SYSTEM
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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WIRELESS REQUEST MANAGEMENT SYSTEM
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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WIRELESS REQUEST MANAGEMENT SYSTEM
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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WIRELESS REQUEST MANAGEMENT SYSTEM
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
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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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WIRELESS REQUEST MANAGEMENT SYSTEM
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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WIRELESS REQUEST MANAGEMENT SYSTEM
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.
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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 .
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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
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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
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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
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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.
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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.
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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
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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
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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]
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Figure2.1 Simple architecture of microcontroller
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Figure 2.2 showing Block Diagram ATMEL 89S52 Microcontroller
2.7 Description of Pin Diagram ATMEL 89S52 Microcontroller
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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
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2.7.5 Port 2
Port 2 is an 8-bit bidirectional I/O port with internal pull-ups. The Port 2 output buffers
can sink/source four TTL inputs. When 1s are written to Port 2 pins, they are pulled high
by the internal pull-ups and can be used as inputs. As inputs, Port 2 pins that are
externally being pulled low will source current (IIL) because of the internal pull-ups.
Port 2 emits the high-order address byte during fetches from external program memory
and during accesses to external data memory that uses 16-bit addresses (MOVX @
DPTR). In this application, 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
Port 3 is an 8-bit bidirectional I/O port with internal pull-ups. The Port 3 output buffers
can sink/source four TTL inputs. When 1s are written to Port 3 pins, they are pulled high
by the internal pull-ups and can be used as inputs. As inputs, Port 3 pins that are
externally being pulled low will source current (IIL) because of the pull-ups. Port 3
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
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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.
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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
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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]
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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
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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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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
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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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Circuit diagram of receiver port
Figure3.4 Circuit diagram of receiver port
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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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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.
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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
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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
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Figure4.1 Block diagram of encoder IC HT12E
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Figure 4.2 Pin diagram of HT12E
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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
9 Ground (0V) Ground
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
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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
Built-in oscillator needs only 5% resistor
Easy interface with an RF or an infrared transmission medium
Minimal external components
Valid transmission indicator
Pair with Holtek’s 212 series of encoders
18-pin DIP, 20-pin SOP package
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Figure 4.3 Block diagram of HT12D decoder
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Figure4.4 Pin diagram of HT12D decoder IC
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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
9 Ground (0V) Ground
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
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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
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5.3 Implementation of transmitter port circuit diagram
Figure 5.3 Implementation of transmitter port circuit diagram
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5.4 Circuit diagram of receiver port
Figure5.4 Circuit diagram of receiver port
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5.5Implementation of receiver port circuit diagram
Figure5.5Implementation of receiver port circuit diagram
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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
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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
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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
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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
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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
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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.
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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
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Pin diagram and description
HT12D
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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
Built-in oscillator needs only 5% resistor
Valid transmission indicator
Easy interface with an RF or an infrared transmission medium
Minimal external components
Pair with Holtek_s 212 series of encoders
18-pin DIP, 20-pin SOP package
Applications
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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.
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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
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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.
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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
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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
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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%.
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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
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[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
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[5] F. Egan, William (2003). Practical RF System Design. Wiley-IEEE Press
[6] Richard C. Dorf (ed.) The Electrical Engineering Handbook, CRC Press, Boca
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[7] Mazedi, The 8051 Microcontroller and Embedded Systems, Prentice Hall, 1ST
Edition
[8] Kenneth J. Ayala, The 8051 Microcontroller, Penram International
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[9] History of wireless, Robert Mallous, Dipak L.Sen Gupta
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[11] Pahlavan, Levesque, Allen H (1995). Wireless Information Networks.
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[12] Geier, Jim (2001). Wireless LANs. Sams
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Networks - a Unified Approach. Prentice Hall.
[16] Rappaport, Theodore (2002). Wireless Communications: Principles and
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[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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