GSM BASED DIGITAL CODE

LOCK SYSTEM USING 8051

MICROCONTROLLER
A Project Report submitted by
U.SRI HARSHA

D.MANIKANTA

AT

ECIL-ECIT
(ELECTRONICS CORPORATION OF INDIA LIMITED)

Under the esteemed guidance of

Mr. SRIDHARA SHETTY (HEAD CED)

Computer Education Division,

ECIL
 ACKNOWLEDGEMENT

I wish to thank those who were involved in the successful completion of my in-plant
training at ECIL (Electronics corporation of India Limited), starting from
Mr. Sridhara Shetty (Head, CED). Secunderabad, for giving me the opportunity and freedom
to learn as per my interests; the head of the team at ECIL , for being a constant support and
guidance; the project lead for my in-plant training Ms. Mounica, for providing me with the
necessary resources; and the entire staff of the company for their support and positivity
which made my internship a worthwhile experience.

I would also like to thank my parents, for being my motivation to take up this internship; and
last, but not the least, the faculty and management at ECIL, Secunderabad for providing me
with such an avenue to help realize how interesting it is to work in today's industry.

By

U.SRI HARSHA

D.MANIKANTA
 COMPANY PROFILE

ECIL was setup under the Department of Atomic Energy on 11th April, 1967 with a view to
generate a strong indigenous capability in the field of professional grade electronics. The
initial accent was on total self-reliance and ECIL was engaged in the design development,
Manufacture and Marketing of several products with emphasis on three technology lines viz.
Computers, Control Systems and Communications. Over the years, ECIL pioneered the
development of various complex electronics products without any external technology help
and scored several ‘firsts’ in this fields prominent among them being country’s

First Digital Computer

First Solid State TV
First Control & Instrumentation of Nuclear Power Plants
First Earth Station Antenna
First Computerized Operator Information System
First radiation Monitoring & Detection System
First Automatic Message Switching System
First Operation & Maintenance Center for E-108 Exchange
First Programmable Logic Controller
First Solid state Cockpit Voice Recorder
First Electronics Voting Machines

The company played a very significant role in the training and growth of high caliber
technical and managerial man power especially in the fields of Computer and Information
Technology. Though the initial thrust was on meeting the Control & Instrumentation
requirements of the Nuclear Power Program, the expand scope of self-reliance pursued by
ECIL enabled the company to develop various products to cater to the needs of Defense,
Civil Aviation, Information & Broadcasting, Telecommunications, Insurance, banking,
Police and Para-Military Forces, Oil & Gas, Power, Space Education, Health, Agriculture
Steel and Coal Sectors and various user departments in the Government domain. ECIL thus
evolved as multi-product company serving multiple sectors of Indian economy with
emphasis on import of country substitution and development of products & services that are
of economic and strategic significance to the country.
 ABSTRACT
Security is a prime concern in our day-today life. Everyone wants to be as much secure as
possible. An access control for doors forms a vital link in a security chain.

The microcontroller based door locker is an access control system that allows only
authorized persons to access a restricted area.

The system is fully controlled by the 8 bit microcontroller AT89C2051 which has a 2K bytes
of ROM for the program memory. The password is stored in the EPROM so that we can
change it at any time.

The system has a Keypad by which the password can be entered through it. When the entered
password equals with the password stored in the memory then the relay gets on and so that
the door is opened.

If we have entered a wrong password for more than three times then the Alarm is switched
on. When we go inside and comeback then the microcontroller will sense the person using
the Laser light, the microcontroller will automatically open the door for you.

The Global System for Mobile communication represents the second generation of mobile
communications. In this project we are even utilizing the mobile nature of communication
and application provided by the GSM technology, namely SMS. Mobile phone is a
revolutionary invention of the century. It was primarily designed for making and receiving
calls & text messages, but it has become the whole world after the Smartphone comes into
the picture.

A message will be sent to your mobile if the password is wrong or correct. So you will be
able to know if someone tries to open your locker.
 INDEX
1. INTRODUCTION
1.1 PROJECT OBJECTIVE

2. INTRODUCTION TO EMBEDDED SYSTEMS

2.1 INTRODUCTION
2.2 DEFINITION OF AN EMBEDDED SYSTEM
2.3 FEATURES OF AN EMBEDDED SYSTEM
2.4 CHARACTERISTICS OF AN EMBEDDED SYSTEM

3. DESIGN ELEMENTS
3.1 MICROCNTROLLER
3.1.1 INTRODUCTION
3.1.2 FEATURES
3.1.3 DESCRIPTION
3.1.4 PIN CONFIGURATION
3.1.5 PIN DECRIPTION
3.2 POWER SUPPLY
3.2.1 DESCRIPTION
3.3 LIQUID CRYSTAL DISPLAY
3.3.1 PIN DESCRIPTION OF LCD
3.4 MAX 232
3.4.1 FEATURES, PIN DIAGRAM AND CIRCUIT CONNECTIONS
3.4.2 FILTERS
3.4.3 REGULATOR
3.5 GSM (Global System for Mobile Communications)
3.6 DC MOTOR
3.7 PUSH BUTTON
3.8 RESET BUTTON
3.9 FILTERS
 3.10 KEYPAD
3.11 BUZZER
3.12 L293D

4. CIRCUIT EXPLANATION
4.1 CIRCUIT DIAGRAM
4.2 DESCRIPTION
4.3 WORKING OF OUR PROJECT
5. C PROGRAM
6. SOFTWARE DESCRIPTION
7. ADVANTAGES
8. DISADVANTAGES
9. APPLICATIONS FUTURE SCOPE
10. CONCLUSION
11. BIBLIOGRAPHY
 ABBREVATIONS
• PSW: Program Status Word
• IP: Interrupt priority
• SFR: Special Function Register
• ALE: Address Latch Enable
• SP: Stack Pointer
• DPL/DPH: Data Pointer Low/Data Pointer High
• PSEN: Program Store Enable
• PCON: Power Control
• TCON: Timer Control
• TMOD: Timer Mode
• ACC: Accumulator
• CAN: Control Area Network
• LED: Light Emitting Diode
• LCD: Liquid Crystal Display
• IR: Infrared
• EA: External Access Enable
• RTS: Request to Send
• CTS: Clear to Send
• ISP: In System Programmable
• DTR: Data Terminal Ready
• DSR: Data Set Ready
• DB: Define Byte
• SCON: Selection Control
• SBUF: Selection Buffer
• RS: Selection Register
• RW: Read Write
• EN: Enable
 INTERNSHIP SUMMARY
As a part of our curriculum, we have been instructed to do in-plant training for a span of 28
days. The intention of introducing in-plant training as a part of our curriculum is to gain
practical knowledge of the subjects learnt in our classroom and to gain industrial exposure.
The in-plant training’s duration is from 03 June 2019 to 04 July 2019. We were divided into
batches at ECIL and were asked to select projects in the stream of embedded systems for
which problem statements were given and out of our interest and curiosity we have selected
the project GSM based digital code lock using microcontroller 8051.

Being a student, it is a wonderful experience to get a chance to work in an esteemed

Organization. We have learnt Organizational etiquette and attained industrial work
experience while maintaining the bi-lateral relations of the University and the Organization
and thereby fulfilling the intention of the University in introducing in plant training as a part
of our curriculum.

MOTIVATION
The project chosen is GSM based digital code lock system using 8051.This was selected
because of incorporating mobile technology with controlling of appliances which we believe
is the next important step to realize the Home Automation. The comfort of being able to take
control of devices from one particular location has become imperative as it saves a lot of time
and effort.
 PROBLEM STATEMENT

Technology has advanced so much in the last decade or two that it has made life more
efficient and comfortable. The comfort of being able to take control of devices from one
particular location has become imperative as it saves a lot of time and effort. Therefore there
arises a need to do so in a systematic manner which we have tried to implement with our
system. The system we have proposed is an extended approach to automating a control
system. The application of our system comes in handy when people who forget to do simple
things such as turn ON or OFF devices at their home or in their office, they can now do so
without their presence by the transmission of a simple text message from their mobile phone.
For the device to be controlled as per desire, a particular “line” or “path” of communication
need not be taken care of. For example TV cannot be controlled unless a clear path is
maintained for the infrared rays to reach the TV. Our project outreaches such problems and
makes it comfortable for the user to operate devices.
 1.INTRODUCTION

1.1. PROJECT OBJECTIVE:

• To design a keyless door entry by using electronic digital lock code.

• To help users and give them favour to go anywhere.

• To avoid any crimes especially stealing activities.

For utilization of appliances the new concept has been thought to manage them remotely by
using GSM, in which the user gets the information whether the entered password is correct or
wrong.
BLOCK DIAGRAM:
This project can be built with 8051 series microcontroller, keypad, buzzer, LCD. Here the
microcontroller controls the entire process like entering the password from the keypad,
compares the entered password from the keypad, compares the entered password with the
predefined password, drives the buzzer and send the status to the display.
FLOW CHART:

2. INTRODUCTION TO EMBEDDED SYSTEMS

2.1. INTRODUCTION
Each day, our lives become more dependent on 'embedded systems', digital information
technology that is embedded in our environment. More than 98% of processors applied today
are in embedded systems, and are no longer visible to the customer as 'computers' in the
ordinary sense. An Embedded System is a special-purpose system in which the computer is
completely encapsulated by or dedicated to the device or system it controls. Unlike a general-
purpose computer, such as a personal computer, an embedded system performs one or a few
predefined tasks, usually with very specific requirements. Since the system is dedicated to
specific tasks, design engineers can optimize it, reducing the size and cost of the product.
Embedded systems are often mass produced, benefiting from economies of scale. The
increasing use of PC hardware is one of the most important developments in high-end
embedded systems in recent years. Hardware costs of high-end systems have dropped
dramatically as a result of this trend, making feasible some projects which previously would
not have been done because of the high cost of non-PC-based embedded hardware. But
software choices for the embedded PC platform are not nearly as attractive as the hardware.

Typically, an embedded system is housed on a single microprocessor board with the

programs stored in ROM. Virtually all appliances that have a digital interface--watches,
microwaves, VCRs, cars--utilize embedded systems. Some embedded systems include an
operating system, but many are so specialized that the entire logic can be implemented as a
single program.

Physically, Embedded Systems range from portable devices such as digital watches and MP3
players, to large stationary installations like traffic lights, factory controllers, or the systems
controlling nuclear powerplants.

In terms of complexity embedded systems can range from very simple with a single
microcontroller chip, to very complex with multiple units, peripherals and networks mounted
inside a large chassis or enclosure.

2.2 DEFINITION OF AN EMBEDDED SYSTEM

An Embedded system is defined as, for a particular / specific application implementing the
software code to interact directly with that particular hardware what we built. Software
isused for providing features and flexibility, Hardware = {Processors, ASICs, Memory...}is
used for Performance (& sometimes security).

(Or)

An embedded system is a special-purpose computer system designed to perform one or a few

dedicated functions, often with real-time computing constraints. It is usually embedded as
part of a complete device including hardware and mechanical parts. In contrast, a general
purpose computer, such as a personal computer, can do many different tasks depending on
programming.

(Or)

An embedded system is a single-purpose computer built into a larger system for the purposes
of controlling and monitoring the system. A computer system that is part of a larger system
or machine.

There are many definitions of embedded system but all of these can be combined into a
single concept. An embedded system is a special purpose computer system that is used for
particular task.

2.3 FEATURES OF AN EMBEDDED SYSTEM

The versatility of the embedded computer system lends itself to utility in all kinds of
enterprises, from the simplification of deliverable products to a reduction in costs in their
development and manufacture. Complex systems with rich functionality employ special
operating systems that take into account major characteristics of embedded systems.
Embedded operating systems have minimized foot print and may follow real-time operating
system specifics.

The special computers system is usually less powerful than general purpose systems,
although some expectations do exist where embedded systems are very powerful and
complicated. Usually a low power consumption CPU with a limited amount of memory is
used in embedded systems. Many embedded systems use very small operating systems; most
of these provide very limited operating system capabilities.

Since the embedded system is dedicated to specific tasks, design engineers can optimize it,
reducing the size and cost of the product, or increasing the reliability and performance. Some
embedded systems are mass-produced, benefiting from economies of scale.

Some embedded systems have to operate in extreme environment conditions such as very
high temperature & humidity.
For high volume systems such as portable music players or mobile phones, minimizing cost
is usually the primary design consideration. Engineers typically select hardware that is just
“good enough” to implement the necessary functions.

For low volume or prototype embedded systems, general purpose computers may be adapted
by limiting the programs or by replacing the operating system with a real-time operating
system.

2.4 CHARACTERISTICS OF AN EMBEDDED SYSTEM

An Embedded computing system generally exhibit rich functionality complex functionality is
usually there as on for introducing CPUs into the design. However, they also exhibit many
non-functional requirements that make the task especially challenging:

• Real-time deadlines that will cause system failure if not met;

• Multi-rate operation;
• In many cases, low power consumption;
• Low manufacturing cost, which often means limited code size.

Workstation programmers often concentrate on functionality. They may consider the

performance characteristics of a few computational kernels of their software, but rarely
analyze the total application. They almost never consider power consumption and
manufacturing cost. The need to juggle all these requirements makes embedded system
programming very challenging and is the reason why embedded system designers need to
understand computer architecture.
 3.DESIGN ELEMENTS
3.1 MICROCONTROLLER
3.1.1 INTRODUCTION:
Microcontrollers as the name suggests are small controllers. They are like single chip
computers that are often embedded into other systems to function as processing/controlling
unit. For example the remote control you are using probably has microcontrollers inside that
do decoding and other controlling functions. They are also used in automobiles, washing
machines, microwave ovens, toys...etc, where automation is needed.

Micro-controllers are useful to the extent that they communicate with other
devices, such as sensors, motors, switches, keypads, displays, memory and even other micro-
controllers. Many interface methods have been developed over the years to solve the
complex problem of balancing circuit design criteria such as features, cost, size, weight,
power consumption, reliability, availability, manufacturability.

Basically, a microcontroller is a device which integrates a number of the components of a

microprocessor system onto a single microchip. So, a microcontroller combines onto the
same microchip. The following components:

1. CPU
2. Core Memory (Both RAM and ROM)
3. Some Parallel Digital I/Os

Essentially, a microcontroller is obtained by integrating the key components of

microprocessor, RAM, ROM, and Digital I/O onto the same chip die. Modern
microcontrollers also contain a wealth of other modules such as Serial I/O, Timers, and
Analogue to Digital Converters. There are a large number of specialized devices with
additional modules for specific needs. E.g. CAN controllers.

3.1.2 FEATURES:
• 8K Bytes of In-System Reprogrammable Flash Memory
• Endurance: 1,000 Write/Erase Cycles
 • Fully Static Operation: 0 Hz to 24 MHz
• 256 x 8-bit Internal RAM
• 32 Programmable I/O Lines
• Three 16-bit Timer/Counters
• Eight Interrupt Sources
• Programmable Serial Channel
• Low-power Idle and Power-down Modes

3.1.3 DESCRIPTION:
The AT89S52 is a low-power, high-performance CMOS8-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 microcontroller. 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 within-system programmable
flash one monolithic chip; the Atmel AT89S52 is a powerful microcontroller, which provides
a highly flexible and cost-effective solution to many embedded control applications.
FIG: BLOCK DIAGRAM OF AT89S52
 3.1.4 PIN CONFIGURATION:

FIG: PIN DIAGRAM OF 8051 MICROCONTROLLER

The AT89S52 provides the following standard features: 8K bytes of Flash, 256 bytes of
RAM, 32 I/O lines, Watchdog timer, two data pointers, three 16-bit timer/counters, full
duplex serial port, on-chip oscillator, and clock circuitry. In addition, the AT89S52 is
designed with static logic for operation down to zero frequency and supports two software
selectable power saving modes. The Idle Modes tops 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.

3.1.5 Pin Description:

Vcc: Supply Voltage.
GND: Ground.
PORT 0:
Port 0 is an 8-bit open drain bi-directional I/O port. As an output port, each pin can sink eight
TTL inputs. When 1s are written to port 0 pins, the pins can be used as high impedance
inputs. Port 0 can also be configured to be the multiplexed low order address/data bus during
accesses to external program and data memory. In this mode, P0 has internal pull-ups. Port 0
also receives the code bytes during Flash programming and outputs the code bytes during
program verification. External pull ups are required during program verification.

PORT 1:
Port1 is an 8-bit bi-directional I/O port with internal pull-ups. The Port 1 Output buffers can
sink/source four TTL inputs. When 1s are written to Port 1 pins, they are pulled high by the
internal pull-ups and can be used as inputs. In addition, P1. 0 and P1. 1 can be configured to
be the timer/counter 2 external count input.

(P1.0/T2) and the timer/counter 2 trigger input P1.1/T2EX), respectively, as shown in the
following table. Port 1 also receives the low-order address bytes during Flash programming.

TABLE: PORT 1 FUNCTIONS.

PORT 2:
 Port 2 is an 8-bit bi-directional I/O port with internal pull-ups. The Port 2 output
buffers can sink/source four TTL inputs. When 1s are written to Port 2 pins, they are pulled
high by the internal pull-ups and can be used as inputs. Port 2 emits the high order address
byte during fetches from external program memory and during accesses to external data
memory that uses 16-bit addresses (MOVX@DPTR). In this application, Port2 uses strong
internal pull-ups when emitting 1s. During accesses to external data memory that use 8-bit
addresses (MOVX@ RI), Port 2 emits the contents of the P2 Special Function Register. Port2
also receives the high-order address bits and some control signals during Flash programming
and verification.

PORT 3:
Port3 is an 8-bit bi-directional I/O port with internal pull-ups. The Port3 output
buffers can sink/source four TTL inputs. When 1s are written to Port3 pins, they are pulled
high by the internal pull-ups and can be used as inputs. As inputs, Port3 pins that are
externally being pulled low will source current (IIL) because of the pull-ups. Port3 also
serves the functions of various special features of the AT89S52, as shown in the following
table.

Port3 also receives some control signals for Flash programming and verification.

TABLE: PORT 3 FUNCTIONS.

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

ALE/PROG:
Address Latch Enable (ALE) is an output pulse for latching the low byte of the address
during accesses to external memory. This pin is also the program pulse input (PROG) during
Flash programming.

In normal operation, ALE is emitted at a constant rate 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.

PSEN:
Program Store Enable (PSEN) is the read strobe to external program memory. When the
AT89S52 is executing code from external program memory, PSEN is activated twice each
machine cycle, except that two PSEN activations are skipped during each access to external
data memory.

EA/VPP:
External Access Enable. EA must be strapped to GND in order to enable the device to fetch
code from external program memory locations starting at 0000H upto FFFFH. Note,
however, that if lock bit 1 is programmed, EA will be internally latched on reset. A should be
strapped to VCC for internal program executions. This pin also receives the12-volt
Programming enables voltage (VPP) during Flash programming.
XTAL1: Input to the inverting oscillator amplifier and input to the internal clock operating
circuit.

XTAL2: Output from the inverting oscillator amplifier.

OSCILLATOR CHARACTERISTICS:
XTAL1 and XTAL2 are the input and output, respectively, of an inverting amplifier that can
be configured for use as a non-chip oscillator, as shown in Figure1. Either a quartz crystal or
ceramic resonat or may be used. To drive the device from an External clock source, XTAL2
should be left unconnected while XTAL1 is driven, as shown in Figure.

FIG: CRYSTAL CIRCUIT

3.2 POWER SUPPLY

DESCRIPTION:
As the microcontroller operating voltage is +5V DC. Through this power supply circuit we
have to create a +5V DC which is given to the microcontroller. The below components are
used to create the power supply

FIG: BLOCK DIAGRAM OF POWER SUPPLY

230V AC supply is given to the step down transformer of 12A type. It may be a 230V to 9V
or 12V step down transformer. The output of the step down transformer is given to bridge
rectifier. The bridge rectifier is formed with 1N4007 diodes. The bridge rectifier converts the
AC Voltage into DC Voltage. But the output DC Voltage contains some AC component
(ripples). So we use a capacitors-2200uF /25V, 0.1uF/D and resistor of 10K as a filter for
removing ripples. That output DC Voltage is given to the positive voltage regulator LM7805
(i.e.,78 represents the positive series and 5 represent the output voltage it can provide). So the
output of the regulator will be the regulated +5V DC. To indicate the condition of the circuit
we place a LED at the end of the circuit.

FIG: SCHEMATIC OF POWER SUPPLY

3.2 LIQUID CRYSTAL DISPLAY

Liquid crystal display is a type of display used in digital watches and many portable
computers.
 PIN DIAGRAM O LCD
LCD displays utilize two sheets of polarizing material with a liquid crystal solution
between them. An electric current passed through the liquid causes the crystals to align so
that light cannot pass through them. Each crystal, therefore, is like a shutter, either
allowing light to pass through or blocking the light.

The input which we give to the microcontroller is displayed on the LCD of the
transmitter side and the message sent is received at the receiver side which displays at the
receiver end of the LCD and the corresponding operation is performed. They make
complicated equipment easier to operate.
3.3.1 PIN DESCRIPTION OF LCD:
The ASCII code to be displayed is eight bits long and is sent to the LCD either four or eight
bits at a time.

• If four bit mode isused, two "nibbles" of data (Sent high four bits and then low four bits
with an "E" Clock pulse with each nibble) are sent to make up a full eight bit transfer.

• The "E" Clock isused to initiate the data transfer within the LCD.
• Deciding how to send the data to the LCD is most critical decision to be made for an LCD
interface application.

• Eight-bit mode is best used when speed is required in an application and at least ten I/O
pins are available.

• The "R/S" bit is used to select whether data or an instruction is being transferred between
the microcontroller and the LCD.

• If the Bit is set, then the byte at the current LCD "Cursor" Position can be reader written.

• When the Bit is reset, either an instruction is being sent to the LCD or the execution status
of the last instruction is read back.

3.4 Max 232

A standard serial interface for PC, RS232C, requires negative logic, i.e., logic 1 is-3V to-12V
and logic 0 is +3V to +12V. To convert TTL logic, say, TxD and RxD pins of the
microcontroller thus need a converter chip. A MAX 232 chip has long been using in many
microcontroller boards. It is a dual RS232 receiver/transmitter that meets all RS232
specifications while using only +5V power supply. It has two on board charge pump voltage
converters which generate +10V to-10V power supplies from a single 5V supply. It has four
level translators, two of which are RS232 transmitters that convert TTL/CMO S input levels
into +9V RS232 outputs. The other two level translators are RS232 receivers that convert
RS232 input to 5V. Typical MAX 232 circuit is shown below.
Features:
1. Operates With single 5-V Power Supply

2. LinBiCMOSE Process Technology.

3.Two Drivers andTwo Receivers

4. ±30-V Input Levels

5. Low Supply Current. 8mA Typical

6. Designed to be Interchangeable With maxim MAX 232

7. Applications

• TIA/EIA-232-F

• Battery-Powered Systems

• Terminals

• Modems

• Computers

Circuit connections:
A standard serial interfacing for PC, RS232C, requires negative logic, i.e., logic '1' is -3V to-
12V and logic '0' is +3V to +12V. To convert a TTL logic, say, TxD and RxD pins of the uC
chips, thus need a converter chip. A MAX 232 chip has long been using in many uC boards.
It provides 2-channel RS232 C port and requires external 10uF capacitors. ADS275 however,
no need external capacitor and smaller.
3.5 GSM (Global System for Mobile communications)
GSM (Global System for Mobile communications) is a cellular network, which means that
mobile phones connect to it by searching for cells in the immediate vicinity. GSM networks
operate in four different frequency ranges. Most GSM networks operate in the 900 MHz or
1800 MHz bands. Some countries in America use the 850 MHz and 1900 MHz bands
because the 900 and 1800 MHz frequency bands were already allocated.

The rarer 400 and 450 MHz frequency bands are as signed in some countries, where these
frequencies were previously used for first-generation systems.

GSM-900 uses 890–915 MHz to send information from the mobile station to the base station
(uplink) and 935–960 MHz for the other direction (downlink), providing 124 RF channels
(channel numbers1 to124) spaced at 200 kHz. Duplex spacing of 45 MHz isused. In some
countries the GSM-900 band has been extended to cover a larger frequency range. This
'extended GSM', E-GSM, uses 880–915 MHz (uplink) and 925–960 MHz (downlink), adding
50 channels (channel numbers 975 to 1023 and 0) to the original GSM-900 band. Time
division multiplexing is used to allow eight full rate or sixteen half-rate speech channels per
radio frequency channel. There are eight radio times lots (giving eight burst periods) grouped
into what is called a TDMA frame. Half rate channels use alternate frames in the same time
slot. The channel data rate is 270. 833k bit/s, and the frame duration is 4.615 ms.
GSM Advantages:
GSM also pioneered a low-cost, to the network carrier, alternative to voice calls, the Short
message service (SMS, also called "text messaging"), which is now supported on other
mobile standards as well. Another advantage is that the standard includes one worldwide
Emergency telephone number, 112.This makes it easier for international travelers to connect
to emergency services without knowing the local emergency number.

The GSM Network:

GSM provides recommendations, not requirements, The GSM specifications define the
functions and interface requirements in detail but do not address the hardware. The GSM
network is divided into three major systems: the switching system (SS), the base station
system (BSS), and the operation and support system (OSS).
The Switching System:
The switching system (SS) is responsible for performing call processing and subscriber-
related functions. The switching system includes the following functional units.

• Home location register (HLR): The HLR is a database used for storage and management
of subscriptions. The HLR is considered the most important database, as it stores permanent
data about subscribers, including a subscriber's service profile, location information, and
activity status. When an individual buys a subscription from one of the PCS operators, he or
she is registered in the HLR of that operator.

• Mobile services switching center (MSC): The MSC performs the telephony switching
functions of the system. It controls calls to and from other telephone and data systems. It also
performs such functions as toll ticketing, network interfacing, common channel signaling,
and others.

• Visitor location register (VLR): The VLR is a database that contains temporary
information about subscribers that is needed by the MSC in order to service visiting
subscribers. The VLR is always integrated with the MSC. When a mobile station roams into
a new MSC area, the VLR connected to that MSC will request data about the mobile station
from the HLR. Later, if the mobile station makes a call, the VLR will have the information
needed for call setup without having to interrogate the HLR each time.

• Authentication center (AUC): A unit called the AUC provides authentication and
encryption parameters that verify the user's identity and ensure the confidentiality of each
call. The AUC protects network operators from different types of fraud found in today's
cellular world.

• Equipment identity register (EIR): The EIR is a database that contains information about
the identity of mobile equipment that prevents calls from stolen, unauthorized, or defective
mobile stations. The AUC and EIR are implemented as stand-alone nodes or as a combined
AUC/EIR node.

The Base Station System (BSS):

All radio-related functions are performed in the BSS, which consists of base station
controllers (BSCs) and the base transceiver stations (BTSs).

• BSC: The BSC provides all the control functions and physical links between the MSC and
BTS. It is a high-capacity switch that provides functions such as hand over, cell configuration
data, and control of radio frequency (RF) power levels in base transceiver stations. A number
of BSCs are served by an MSC.

• BTS: The BTS handles the radio interface to the mobile station. The BTS is the radio
equipment (transceivers and antennas) needed to service each cell in the network. A group of
BTSs are controlled by a BSC.

The Operation and Support System

The operations and maintenance center (OMC) is connected to all equipment in the switching
system and to the BSC. The implementation of OMC is called the operation and support
system (OSS). The OSS is the functional entity from which the network operator monitors
and controls the system. The purpose of OSS is to offer the customer cost-effective support
for centralized, regional and local operational and maintenance activities that are required for
a GSM network. An important function of OSS is to provide a network overview and support
the maintenance activities of different operation and maintenance organizations.

Additional Functional Elements

• Message center (MXE): The MXE is a node that provides integrated voice, fax, and data
messaging. Specifically, the MXE handles short message srvice, cell broadcast, voicemail,
fax mail, e-mail, and notification.

• Mobile service node (MSN): The MSN is the node that handles the mobile intelligent
network (IN) services.

• Gateway mobile services switching center (GMSC): A gateway is a node used to

interconnect two networks. The gateway is often implemented in an MSC. The MSC is then
referred to as the GMSC.

• GSM inter-working unit (GIWU): The GIWU consists of both hardware and software
that provides an interface to various networks for data communications. Through the GIWU,
users can alternate between speech and data during the same call. The GIWU hardware
equipment is physically located at the MSC/VLR.

GSM Network Areas:

The GSM network is made up of geographic areas. As shown in below figure, these areas
include cells, location areas (LAs), MSC/VLR service areas, and public land mobile network
(PLMN) areas.

Location Areas:
The cell is the area given radio coverage by one base transceiver station. The GSM network
identifies each cell via the cell global identity (CGI) number assigned to each cell. The
location area is a group of cells. It is the area in which the subscriber is paged. Each LA is
served by one or more base station controllers, yet only by a single MSC Each LA is
assigned a location area identity (LAI) number.

MSC/VLR service areas:

An MSC/VLR service area represents the part of the GSM network that is covered by one
MSC and which is reachable, as it is registered in the VLR of the MSC.
PLMN service areas:
The PLMN service area is an area served by one network operator.

GSM Specifications:
Specifications for different personal communication services (PCS) systems vary among the
different PCS networks. Listed below is a description of the specifications and characteristics
for GSM.

• Frequency band: The frequency range specified for GSM is 1,850 to 1,990 MHz (mobile
station to base station).

• Duplex distance: The duplex distance is 80MHz. Duplex distance is the distance between
the uplink and downlink frequencies. A channel has two frequencies, 80 MHz apart.

• Channel separation: The separation between adjacent carrier frequencies. In GSM, this is
200 kHz.

• Modulation: Modulation is the process of sending a signal by changing the characteristics

of a carrier frequency. This is done in GSM via Gaussian minimum shift keying (GMSK).

• Transmission rate: GSM is a digital system with an over-the-air bit rate of 270 kbps.

• Access method: GSM utilizes the time division multiple access (TDMA) concept. TDMA
is a technique in which several different calls may share the same carrier. Each call is
assigned a particular time slot.

• Speech coder: GSM uses linear predictive coding (LPC).The purpose of LPC is to reduce
the bit rate. The LPC provides parameters for a filter that mimics the vocal tract. The signal
passes through this filter, leaving behind a residual signal. Speech is encoded at 13 kbps.

GSM Subscriber Services:

Dual-tone multi frequency (DTMF): DTMF is a tone signaling scheme often used for
various control purposes via the telephone network, such as remote control of an answering
machine. GSM supports full-originating DTMF.
Facsimile group III—GSM supports CCITT Group 3 facsimile. As standard fax machines
are designed to be connected to a telephone using analog signals, a special fax converter
connected to the exchange is used in the GSM system. This enables a GSM–connected fax to
communicate with any analog fax in the network.

Short message services: A convenient facility of the GSM network is the short message
service. A message consisting of a maximum of 160 alphanumeric characters can be sent to
or from a mobile station. This service can be viewed as an advanced form of alphanumeric
paging with a number of advantages. If the subscriber's mobile unit is powered off or has left
the coverage area, the message is stored and offered back to the subscriber when the mobile
is powered on or has reentered the coverage area of the network. This function ensures that
the message will be received.

Cell broadcast: A variation of the short message service is the cell broadcast facility. A
message of a maximum of 93 characters can be broadcast to all mobile subscribers in a
certain geographic area. Typical applications include traffic congestion warnings and reports
on accidents.

Voice mail: This service is actually an answering machine within the network, which is
controlled by the subscriber. Calls can be forwarded to the subscriber's voice-mail box and
the subscriber checks for messages via a personal security code.

Fax mail: With this service, the subscriber can receive fax messages at any fax machine. The
messages are stored in a service center from which they can be retrieved by the subscriber via
a personal security code to the desired fax number

Supplementary Services:
GSM supports a comprehensive set of supplementary services that can complement and
support both telephony and data services.

Call forwarding: This service gives the subscriber the ability to forward incoming calls to
another number if the called mobile unit is not reachable, if it is busy, if there is no reply, or
if call forwarding is allowed unconditionally.

Barring of outgoing calls: This service makes it possible for a mobile subscriber to prevent
all outgoing calls.
Barring of incoming calls: This function allows the subscriber to prevent incoming calls.
The following two conditions for incoming call barring exist: baring of all incoming calls and
barring of incoming calls when roaming outside the home PLMN.

Advice of charge (AoC): The AoC service provides the mobile subscriber with an estimate
of the call charges. There are two types of AoC information: one that provides the subscriber
with an estimate of the bill and one that can be used for immediate charging purposes. AoC
for data calls is provided on the basis of time measurements.

Call hold: This service enables the subscriber to interrupt an ongoing call and then
subsequently reestablish the call. The call hold service is only applicable to normal
telephony.

Call waiting: This service enables the mobile subscriber to be notified of an incoming call
during a conversation. The subscriber can answer, reject, or ignore the incoming call. Call
waiting is applicable to all GSM telecommunications services using a circuit-switched
connection.

Multi party service: The multiparty service enables a mobile subscriber to establish a
multiparty conversation—that is, a simultaneous conversation between three and six
subscribers. This service is only applicable to normal telephony.

Calling line identification presentation/restriction: These services supply the called party
with the integrated services digital network (ISDN) number of the calling party. The
restriction service enables the calling party to restrict the presentation. The restriction
overrides the presentation.

Closed user groups (CUGs): CUGs are generally comparable to a PBX. They are a group
of subscribers who are capable of only calling themselves and certain numbers

Main AT commands:
"AT command set for GSM Mobile Equipment” describes the Main AT commands to
communicate via a serial interface with the GSM sub system of the phone.
AT commands are instructions used to control a modem. AT is the abbreviation of Attention.
Every command line starts with "AT" or "at". That's why modem commands are called AT
commands. Many of the commands that are used to control wired dial-up modems, such as
ATD (Dial), ATA (Answer), ATH (Hook control) and ATO (Return to online data state), are
also supported by GSM/GPRS modems and mobile phones. Besides this common AT
command set, GSM/GPRS modems and mobile phones support an AT command set that is
specific to the GSM technology, which includes SMS-related commands like AT+CMGS
(Send SMS message), AT+CMSS (Send SMS message from storage), AT+CMGL (List SMS
messages) and AT+CMGR (Read SMS messages).

Note that the starting "AT" is the prefix that informs the modem about the start of a
command line. It is not part of the AT command name. For example, D is the actual AT
command name in ATD and +CMGS is the actual AT command name in AT+CMGS.
However, some books and websites use them interchangeably as the name of an AT
command.

Here are some of the tasks that can be done using AT commands with a GSM/GPRS modem
or mobile phone:

• Get basic information about the mobile phone or GSM/GPRS modem. For example, name
of manufacturer (AT+CGMI), model number (AT+CGMM), IMEI number (International
Mobile Equipment Identity) (AT+CGSN) and software version (AT+CGMR).

• Get basic information about the subscriber. For example, MSISDN (AT+CNUM) and IMSI
number (International Mobile Subscriber Identity) (AT+CIMI).

• Get the current status of the mobile phone or GSM/GPRS modem. For example, mobile
phone activity status (AT+CPAS), mobile network registration status (AT+CREG), radio
signal strength (AT+CSQ), battery charge level and battery charging status (AT+CBC).

• Establish a data connection or voice connection to a remote modem (ATD, ATA, etc).

• Send and receive fax (ATD, ATA, AT+F*).

• Send (AT+CMGS, AT+CMSS), read (AT+CMGR, AT+CMGL), write (AT+CMGW) or
delete (AT+CMGD) SMS messages and obtain notifications of newly received SMS
messages. (AT+CNMI).

• Read (AT+CPBR), write (AT+CPBW) or search (AT+CPBF) phone book entries.

• Perform security-related tasks, such as opening or closing facility locks (AT+CLCK),

checking whether a facility is locked (AT+CLCK) and changing passwords (AT+CPWD).
(Facility lock examples: SIM lock [a password must be given to the SIM card every time the
mobile phone is switched on] and PH-SIM lock [a certain SIM card is associated with the
mobile phone. To use other SIM cards with the mobile phone, a password must be entered.])

• Control the presentation of result codes/error messages of AT commands. For example,

you can control whether to enable certain error messages (AT+CMEE) and whether error
messages should be displayed in numeric format or verbose format
(AT+CMEE=1orAT+CMEE=2).

• Get or change the configurations of the mobile phone or GSM/GPRS modem. For example,
change the GSM network (AT+COPS), bearer service type (AT+CBST), radio link protocol
parameters (AT+CRLP), SMS center address (AT+CSCA) and storage of SMS messages
(AT+CPMS).

• Save and restore configurations of the mobile phone or GSM/GPRS modem. For example,
save (AT+CSAS) and restore (AT+CRES) settings related to SMS messaging such as the
SMS center address.

3.6DCMOTOR
A DC motor is designed to run on DC electric power. Two examples of pure DC designs are
Michael Faraday's homo polar motor (which is uncommon), and the ball bear in motor,
which is (so far) a novelty. By far the most common DC motor types are the brushed and
brushless types, which use internal and external commutation respectively to create an
oscillating AC current from the DC source—so they are not purely DC machines in a strict
sense.
Types of DC motors:
1. Brushed DC Motors

2. Brushless DC motors

3. Coreless DC motors

Brushed DC motors: The classic DC motor design generates an oscillating current in a

wound rotor with a split ring commutator, and either a wound or permanent magnet stator. A
rotor consists of a coil wound around a rotor which is then powered by any type of battery.

Many of the limitations of the classic commutator DC motor are due to the need for brushes
to press against the commutator. This creates friction. At higher speeds, brushes have
increasing difficulty in maintaining contact. Brushes may bounce off the irregularities in the
commutator surface, creating sparks. This limits the maximum speed of the machine. The
current density per unit area of the brushes limits the output of the motor. The imperfect
electric contact also causes electrical noise. Brushes eventually wear out and require
replacement, and the commutator itself is subject to wear and maintenance. The commutator
assembly on a large machine is a costly element, requiring precision assembly of many parts.
There are three types of dc motor 1. Dc series motor 2. Dc shunt motor 3. Dc compound
motor -these are also two type a. cumulative compound b. differential compound

Brushless DC motors: Some of the problems of the brushed DC motor are eliminated in the
brushless design. In this motor, the mechanical "rotating switch" or commutator/brush gear
assembly is replaced by an external electronic switch synchronized to the rotor's position.
Brushless motors are typically 85-90% efficient, whereas DC motors with brush gear are
typically 75-80% efficient.

Midway between ordinary DC motor sand stepper motors lies the realm of the brushless DC
motor. Built in a fashion very similar to stepper motors, these often use a permanent magnet
external rotor, three phases of driving coils, one or more Hall effect sensors to sense the
position of the rotor, and the associated drive electronics. The coils are activated, one phase
after the other, by the drive electronics ascued by the signals from the Hall effect sensors. In
effect, they act as three-phase synchronous motors containing their own variable-frequency
drive electronics. A specialized class of brushless DC motor controllers utilize EMF
feedback through the main phase connections instead of Halleffect sensors to determine
position and velocity. These motors are used extensively in electric radio controlled vehicles.
When configured with the magnets on the outside, these are referred to by mode lists as out
runner motors.

Brushless DC motors are commonly used where precise speed control is necessary, as in
computer disk drives or in video cassette recorders, the spindles within CD, CD ROM (etc.)
drives, and mechanisms within office products such as fans, laser printers and photo copiers.
They have several advantages over conventional motors:

• Compared to AC fans using shaded-pole motors, they are very efficient, running much
cooler than the equivalent AC motors. This cool operation leads to much-improved life of the
fan's bearings.

• Without a commutator to wear out, the life of a DC brushless motor can be significantly
longer compared to a DC motor using brushes and a commutator. Commutation also tends to
cause a great deal of electrical and RF noise; without a commutator or brushes, a brushless
motor may be used in electrically sensitive devices like audio equipment or computers.

• The same Hall effect sensors that provide the commutation can also provide a convenient
tachometer signal for closed-loop control (servo-controlled) applications. In fans, the
tachometer signal can be used to derive a "fan OK" signal.
• The motor can be easily synchronized to an internal or external clock, leading to precise
speed control.

• Brushless motors have no chance of sparking, unlike brushed motors, making them better
suited to environments with volatile chemical sand fuels. Also, sparking generates ozone
which can accumulate in poorly ventilated buildings risking harm to occupants 'health.

• Brushless motors are usually used in small equipment such as computers and are generally
used to get rid of unwanted heat.

• They are also very quiet motors which is an advantage if being used in equipment that is
affected by vibrations.

Modern DC brushless motors range in power from a fraction of a watt to many kilowatts.
Larger brushless motors up to about 100kW rating are used in electric vehicles. They also
find significant use in high-performance electric model aircraft.

Coreless DC motors:
Nothing in the design of any of the motors described above requires that the iron (steel)
portions of the rotor actually rotate; torque is exerted only on the windings of the electro
magnets. Taking advantage of this fact is the coreless DC motor, a specialized form of a
brush or brushless DC motor. Optimized for rapid acceleration, these motors have a rotor that
is constructed without any iron core. The rotor can take the form of a winding-filled cylinder
inside the stator magnets, a basket surrounding the stator magnets, or a flat pancake (possibly
formed on a printed wiring board) running between upper and lower stator magnets. The
windings are typically stabilized by being impregnated with Electrical epoxy potting systems.
Filled epoxies that have moderate mixed viscosity and along gel time. These systems are
highlighted by low shrinkage and low exotherm. Typically UL1446 recognized as a potting
compound for use up to 180C (Class H) UL File No.E210549.

Because the rotor is much lighter in weight (mass) than a conventional rotor formed from
copper windings on steel laminations, the rotor can accelerate much more rapidly, often
achieving a mechanical time constant under 1ms. This is especially true if the windings use
aluminum rather than the heavier copper. But because there is no metal mass in the rotor to
act as a heat sink, even small core less motors must often be cooled by forced air.
These motors were commonly used to drive the capstan(s) of magnetic tape drives and are
still widely used in high-performance servo-controlled systems, like radio controlled
vehicles/aircraft, humanoid robotic systems, industrial automation, medical devices, etc.

3.7 PUSHBUTTON
A push-button (also spelled push button) (press-button in the UK) or simply button is a
simple switch mechanism for controlling some aspect of a machine or a process. Buttons are
typically made out of hard material, usually plastic or metal. The surface is usually flat or
shaped to accommodate the human finger or hand, so as to be easily depressed or pushed.
But tons are most often biased switches, though even many un-biased buttons (due to their
physical nature) require a spring to return to thei run-pushed state. Different people use
different terms for the "pushing" of the button, such as press, depress, mash, and punch.

3.8 RESETBUTTON
In electronics and technology, are set button is a button that can reset a device. On video
game consoles, the reset button restarts the game, losing the player's unsaved progress. On
personal computers, the reset button clears the memory and reboots the machine forcibly.
Reset buttons are found on circuit breakers to reset the circuit. This button can cause data
corruption so this button often doesn't exist on many machines. Usually, in computers, it is
present as a small button, possibly recessed into the case, to prevent accidentally pressing it.

3.9 FILTERS:
Filters are electronic circuits which perform signal processing functions, specifically to
remove unwanted frequency components from the signal, to enhance wanted ones, or both.
Electronic filters can be:

• passive or active

• analog or digital

• High-pass, low-pass, bandpass, band-reject (band reject; notch), or all-pass.

• discrete-time (sampled) or continuous-time

• linear or non-linear
• infinite impulse response (IIR type) or finite impulse response (FIR type)

The most common types of electronic filters are linear filters, regard less of other aspects of
their design. See the article on linear filters for details on their design and analysis.

Passive implementations of linear filters are based on combinations of resistors (R), inductors
(L) and capacitors(C). These types are collectively known as passive filters, because they do
not depend upon an external power supply and/or they do not contain active components
such as transistors.

Inductors block high-frequency signals and conduct low-frequency signals, while capacitors
do the reverse. A filter in which the signal passes through an inductor, or in which a capacitor
provides a path to ground, presents less attenuation to low frequency signals than high-
frequency signals and is a low-pass filter. If the signal passes through a capacitor, or has a
path to ground through an inductor, then the filter presents less attenuation to high-frequency
signals than low-frequency signals and is a high-pass filter. Resistors on their own have no
frequency-selective properties, but are added to inductors and capacitors to determine the
time constants of the circuit, and therefore the frequencies to which it responds.

The inductors and capacitors are the reactive elements of the filter. The number of elements
determines the order of the filter. In this context, an LC tuned circuit being used in a band-
pass or band-stop filter is considered a single element even though it consists of two
components.

At high frequencies (above about 100 megahertz), sometimes the inductors consist of single
loops or strips of sheet metal, and the capacitors consist of adjacent strips of metal. These
inductive or capacitive pieces of metal are called stubs.

3.10 KEYPAD-PHONE
A keypad is a set of buttons arranged in a block or "pad" which bear digits, symbols or
alphabetical letters. Pads mostly containing numbers are called a numeric keypad. Numeric
keypads are found on alpha numeric keyboards and on other devices which require mainly
numeric input such as calculators, push-button telephones, vending machines, ATMs, Point
of Sale devices, combination locks, and digital door locks. Many devices follow the E.161
standard for their arrangement.

A computer keyboard usually has a small numeric keypad on the side, in addition to the
other number keys on the top, but with a calculator-style arrangement of buttons that allow
more efficient entry of numerical data. This number pad (commonly abbreviated to
"numpad") is usually positioned on the right side of the keyboard because most people are
right-handed.

Many laptop computers have special function keys which turn part of the alphabetical
keyboard into a numerical keypad as there is insufficient space to allow a separate keypad to
built into the laptop's chassis. Separate external plug-in keypads can be purchased. Keypads
for the entry of PINs and for product selection appear on many devices including ATMs,
vending machines, Point of Sale payment devices, time clocks, combination locks and digital
door locks. The first key-activated mechanical calculators and many cash registers used
"parallel" keys with one column of 0 to 9 for each position the machine could use. A smaller,
10-key input first started on the Standard Adding Machine in 1901. The calculator had the
digit keys arranged in one row, with zero on the left, and 9 on the right. The modern four row
arrangement debuted with the Sundstrand Adding Machine in 1911.

There is no standard for the layout of the four arithmetic operations, the decimal point, equal
sign or other more advanced mathematical functions on the keypad of a calculator. The
invention of the Push-button telephone keypad is attributed to John E. Karlin, an industrial
psychologist at Bell Labs in Murray Hill, NJ. On a telephone keypad, the numbers 1 through
9 are arranged from left to right, top to bottom with 0 in a row below 7 8 9 and in the center.
Telephone keypads also have the special buttons labelled * (star) and # (octothorpe, number
sign, "pound", "hex" or "hash") on either side of the zero key. The keys on a telephone may
also bear letters which have had several auxiliary uses, such as remembering area codes or
whole telephone numbers.
Applications:

• Keyboard (computing)
• Telephone keypad
• Push-button telephone
• Silicone rubber keypad
• Numeric keypad
• Mobile phone
• Digital door lock
• Arrow keys

3.11BUZZER
The electric buzzer was invented by Joseph Henry. They were mainly used in early door bells
until they were phased out in the early1930s in favor of musical chimes, which had a softer
tone. A buzzer or beeper is an audio signaling device, which may be mechanical, electro
mechanical, or piezoelectric (piezo for short). Typical uses of buzzers and beepers include
alarm devices, timers, and confirmation of user input such as a mouse click or key stroke.

• Novelty uses
• Judging panels
• Educational purposes
• Annunciator panels
• Electronic metronomes
• Game show lock-out device
• Microwave ovens and other house hold appliances
• Sporting events such as basketball games
• Electrical alarms
• Joy buzzer (mechanical buzzer used for pranks)
3.12L293D
L293D is a typical Motor driver or Motor Driver IC which allows DC motor to drive on
either direction. L293D is a 16-pin IC which can control a set of two DC motors
simultaneously in any direction. It means that you can control two DC motor with a single
L293DIC. Dual H-bridge Motor Driver integrated circuit (IC). The l293d can drive small and
quiet big motors as well.

WorkingofL293D:
There are 4 input pins for l293d, pin2, 7 on the left and pin 15, 10 on the right as shown on
the pin diagram. Left input pins will regulate the rotation of motor connected across left side
and right input for motor on the righthand side. The motors are rotated on the basis of the
inputs provided across the input pins as LOGIC 0 or LOGIC 1.

In simple you need to provide Logic 0 or 1 across the input pins for rotating the motor.

L293D Logic Table:

Let’s consider a Motor connected on left side output pins (pin3,6). For rotating the motor in
clockwise direction the input pins has to be provided with Logic 1 and Logic 0.
• Pin 2 = Logic 1 and Pin 7 = Logic 0 | Clockwise Direction
• Pin 2 = Logic 0 and Pin 7 = Logic 1 | Anticlockwise Direction
• Pin2 = Logic 0 and Pin 7 = Logic 0 | Idle [No rotation] [Hi-Impedance state]
• Pin 2 = Logic 1 and Pin 7 = Logic 1 | Idle [No rotation]

4. CIRCUIT EXPLANATION
4.1 CIRCUIT DIAGRAM

4.2 Circuit Description:

Circuit diagram for this Digital lock using 8051 has been shown above and can easily be
understood. Keypad module’s Column pins are directly connected to pin P0.0, P0.1, P0.2,
P0.3 and Row pins are connected to P0.4, P0.5, P0.6, P0.7 of 89s52 microcontroller’s port 0.
A 16x2 LCD is connected with 89s52 microcontroller in 4-bit mode. Control pin RS, RW
and En are directly connected to pin P1.0, GND and P1.2. And data pin D4-D7 is connected
to pins P1.4, P1.5, P1.6 and P1.7 of 89s52. And one buzzer is connected at pin P2.6 through a
resistor.

4.3 Working of our project:

The proposed system uses a matrix keypad and an LCD as an input and output devices. A 4-
digit predefined password requires to be specified the person. This password is saved in the
system. While opening, if the given password from matrix keypad matches with the saved
password, then the lock gets opened and a note is displayed on the LCD. Also, an o/p pin is
made high to be used for further purposes.

As the program runs, the string ‘Enter Password’ is exhibited on the LCD. The keypad is
checked for the entered digits one by one. Each time, row & column of the key pushed is
noticed and a * is shown on LCD parallel to the entered number. After the password is
entered, the consumer is provoked to ‘verify Password’ and yet again the key is taken
through the LCD. If the given passwords do not equal, a note is displayed to specify ‘Wrong
Password’; or else the user is provoked to open the device.

To open, a person needs to ‘Enter Password’ through a keypad. Again thekeypad is checked
for the entered digits and equivalent digits are recognized. The pass key is exhibited as
‘****’ on the LCD display. After the password is entered, they are contrasted with the
predetermined password. If all the digits equal to a set password, LCD exhibits ‘Lock Open’
and the output pin of the lock go high. If the code is wrong, ‘Wrong Password’ is sent to be
shown on the LCD. The system gets protected if more than three tries are made with an
incorrect password to unlock the digital code lock. The system desires to be rearranged in
such a case.
 5. C PROGRAM
#include<reg51.h>

#include<intrins.h> //header file used for generating code for routine programs//

#define lcd P0 //defining the LCD DATA pins to port’0’//

sbitrs=P1^5; //DATA/COMMAND control pin of LCD assigning to port ‘1.5’//

sbitrw=P1^6; //READ/WRITE control pin of LCD assigning to port ‘1.6’//

sbit en=P1^7; //ENABLE control pin of LCD assigning to port ‘1.7’//

sbitlcd_bsy=P0^7; //assigning the port ‘0.7’ for checking the busy of LCD//

sbit R0 = P2^7; //KEYPAD ROW 1//

sbit R1 = P2^6; //KEYPAD ROW 2//

sbit R2 = P2^5; //KEYPAD ROW 3//

sbit R3 = P2^4; //KEYPAD ROW 4//

sbit C3 = P2^3; //KEYPAD COLUMN 4//

sbit C2 = P2^2; //KEYPAD COLUMN 3//

sbit C1 = P2^1; //KEYPAD COLUMN 2//

sbit C0 = P2^0; //KEYPAD COLUMN 1//

sbit mt0 = P1^0; //MOTOR PINS//

sbit mt1 = P1^1; //MOTOR//

sbit mt2 = P1^2; //MOTOR//

sbit mt3 = P1^3; //MOTOR//

sbit buzzer = P1^4; //BUZZER PIN//

voidinit_lcd(void); //Initializing Commands for LCD//

voidcmd_lcd(unsigned char); //LCD COMMAND write function(global declaration)//

voidlcd_data(unsigned char); //LCD DATA write function(global declaration)//

voiddisplay_lcd(unsignes char *); //LCD DISPLAY function(global declaration)//

voidLCD_Busy_Chk(void);

void GSM_INIT(void); //GSM initialization Function//

void DELAYMS(unsigned int); //DELAY function(global declaration)

void LCD_KEYPAD(void); //KEYPAD WRITING function(global declaration)//

void LCD_STORE(void); //KEYPAD DATA storing function(global declaration)//

intkeypress(); //KEYPAD KEY PRESS checking function(global declaration)//

void CMND_SEND(char *); //GSM DATA SENDING function(global declaration)//

void SER_CHAR(char); //GSM COMMANDS function(global declaration)//

inti,j,k,row,col;

unsigned char pwd_cnt=0,key_cnt=0,wrg_cnt=0,otp_cnt=0,otp_cnt1=0;

char a[4]={‘0’,’0’,’0’,’0’};

char otppwd[8]= {'0','0','0','0','0','0','0','0'}; //OTP Password strings//

char temp1[8]={'0','0','0','0','0','0','0','0'};

char c[8];

charpwd[4]={'0','0','0','0'}; //Pre – Defined PASSWORD//

unsigned char fkey,sc,sp,dat,byte,key_store,cnt;

unsigned char KEY_PAD[4][4]={'1','1','1','1','0','0','0','0','0','0','0','0','1','1','1','1'}; //4x4

KEYPAD MATRIX DECLARATION//

/**********/

voidserial_communication(void)interrupt 4

While(T!=0)

{
 TI=0; //clear interrupt

I=0;

While(RI!=0)

RI=0; //clear interrupt

Dat=SBUF;

// MAIN PROGRAM //

Void main(void)

mt0=0;mt1=0;mt2=0;mt3=0;buzzer=0;

TMOD = 0x20; //Setting for Serial Communication//

SCON = 0x50; //Serial Communication//

TH1 = 0xFD; //Baud Rate for GSM//

TR1 = 1; //Starting the Timer//

init_lcd(); //GIVING INITIAL COMMANDS TO LCD//

cmd_lcd(0x80);

display_lcd("PROTECTION BASED DOOR");

cmd_lcd(0xC0);

display_lcd(“SECURITY SYSTEM”);

DELAYMS(1000);
Start:

cmd_lcd(0x01);

cmd_lcd(0x80);

display_lcd(“PLS ENTER PWD…”);

cmd_lcd(0xC0);

key_cnt=0:j=0;

while(key_cnt!=4) //To Enter the 4 digit pin or PASSWORD//

LCD_KEYPAD();

if(fkey==1)

fkey=0;

a[j] = key_store;

byte=a[j];

lcd_data(‘*’);

j++;

key_cnt++;

j=0;

cmd_lcd(0x01);

cmd_lcd(0x80);

display_lcd(“PWD VERIFYING…”);

DELAYMS(200);
 pwd_cnt=0;

for(i=0;i<4;i++) //Verifying the entered password

with pre-defined password//

if(a[i]==pwd[i])

pwd_cnt++;

if(pwd_cnt==4)

cmd_lcd(0x01);

cmd_lcd(0x80);

display_lcd(“ PWD MATCHED “);

DELAYMS(200);

cmd_lcd(0x01);

cmd_lcd(0x80);

display_lcd(“DOOR UNLOCK”):

DELAYMS(200);

CMND_SEND(“AT+CMGS=”); //GSM//

SER_CHAR(0x22);

CMND_SEND(“+917981521904”);

SER_CHAR(0x22);

SER_CHAR(0x0D);
 CMND_SEND(“DOOR UNLOCK”);

// OTP PASSWORD LOGIC //

if(otp_cnt==9)

for(i=0;i<7;i++)

temp1[i]=otppwd[i];

otppwd[0]=temp1[1];

otppwd[1]=temp1[2];

otppwd[2]=temp1[7];

otppwd[4]=temp1[5];

otppwd[5]=temp1[4];

otppwd[7]=temp1[0];

otp_cnt=0;

otppwd[0]=otppwd[0]+2;

otppwd[1]=otppwd[1]+6;

otppwd[2]=otppwd[2]+7;

otppwd[4]=otppwd[4]+1;

otppwd[5]=otppwd[5]+2;

otppwd[7]=otppwd[7]+3;

if(otppwd[0]>=0x3A)
{

Otppwd[0]=otppwd[0]-10;

if((otppwd[1]>=0x3A))

otppwd[1]=otppwd[1]-10;

if((otppwd[2]>=0x3A))

otppwd[2]=otppwd[2]-10;

if((otppwd[4]>=0x3A))

otppwd[4]=otppwd[4]-10;

if((otppwd[5]>=0x3A))

otppwd[5]=otppwd[5]-10;

if((otppwd[7]>=0x3A))

otppwd[7]=otppwd[7]-10;

SER_CHAR(otppwd[0]); //Sending the OTP String to Phone//

SER_CHAR(otppwd[1]);

SER_CHAR(otppwd[2]);

SER_CHAR(otppwd[3]);

SER_CHAR(otppwd[4]);

SER_CHAR(otppwd[5]);

SER_CHAR(otppwd[6]);

SER_CHAR(otppwd[7]);

SER_CHAR(0x1A);

DELAYMS(1000);

otp_cnt++;

cmd_lcd(0x01);

cmd_lcd(0x80);

display_lcd("DOORUNCLOCK");

DELAYMS(200);

cmd_lcd(0x80);

display_lcd("........");

cmd_lcd(0xC0);

k=0;key_cnt=0;

while(key_cnt!=8) //To Enter the OTP send in the KEYPAD//

LCD_KEYPAD();

if(fkey==1)

fkey=0;
c[k] = key_store;

byte=c[k];

lcd_data('*');

k++;

key_cnt++;

cmd_lcd(0x01);

cmd_lcd(0x80);

display_lcd("...");

DELAYMS(200);

otp_cnt1=0;

for(k=0;k<8;k++) //Verifying the Entered OTP with send OTP//

if(c[k]==otppwd[k])

otp_cnt1++;

if(otp_cnt1==8)

cmd_lcd(0x01);

cmd_lcd(0x80);

display_lcd("DOORUNLOCKED");
 DELAYMS(500);

cmd_lcd(0x01);

cmd_lcd(0x80);

display_lcd("YOU ARE WELCOME");

mt0=1;mt1=0;mt2=0;mt3=1; //Make Motor To run for some

time in clockwise//

DELAYMS(500);

mt0=0;mt1=0;mt2=0;mt3=0;

DELAYMS(500);

cmd_lcd(0x01);

cmd_lcd(0x80);

display_lcd(" THANKING YOU ");

mt0=0;mt1=1;mt2=1;mt3=0; //Make Motor To run for some

time in anti-clockwise//

DELAYMS(500);

mt0=0;mt1=0;mt2=0;mt3=0;

DELAYMS(500);

wrg_cnt=0;

goto Start;

else

cmd_lcd(0x01);

cmd_lcd(0x80);

display_lcd("DOOR UNLOCKED");
cmd_lcd(0xC0);

display_lcd("YOUR’E WELCOME:-),:-),");

DELAYMS(1000);

goto Start;

else

cmd_lcd(0x01);

cmd_lcd(0x80);

display_lcd(":-)");

DELAYMS(500);

wrg_cnt++;

if(wrg_cnt==4)

cmd_lcd(0x01);

cmd_lcd(0x80);

display_lcd("ACCESS ACCEPTED");

cmd_lcd(0xC0);

display_lcd("MAX TIMES TRIED");

DELAYMS(1000);

cmd_lcd(0x80);

display_lcd("TRY AFTER");

cmd_lcd(0xC0);
 display_lcd("SOME TIME");

DELAYMS(1000);

CMND_SEND("AT+CMGS=");

SER_CHAR(0x22);

CMND_SEND("+917981521904");

SER_CHAR(0x22);

SER_CHAR(0x0D);

CMND_SEND("SOME ONE IS TRYING TO OPEN YOUR DOOR, PLEASE GO

AND CHECK IT");

SER_CHAR(0x1A); //Sending the Warning mgs to phone//

buzzer=1; //sound’s the Alarm//

DELAYMS(5000);

buzzer=0;

DELAYMS(60000); //DELAY FOR 10 MIN//

wrg_cnt=0;

goto Start;

voidinit_lcd(void)

cmd_lcd(0x30);

cmd_lcd(0x30);

cmd_lcd(0x38);
 cmd_lcd(0x0c);

cmd_lcd(0x06);

cmd_lcd(0x01);

DELAYMS(10);

voidcmd_lcd(unsigned char c)

LCD_Busy_Chk();

lcd=c;

rs=0;

rw=0;

en=1;

nop();

en=0;

voidlcd_data(unsigned char c)

LCD_Busy_Chk();

lcd=c;

rs=1;

rw=0;

en=1;

nop();

en=0;
}

voidLCD_Busy_Chk(void)

lcd_bsy=1;

rs=0;

rw=1;

while(lcd_bsy==1)

en=0;

nop();

nop();

nop();

nop();

en=1;

voiddisplay_lcd(unsigned char *s)

while(*s)

lcd_data(*s++);

void CMND_SEND(char*letter)

{
while(*letter)

SBUF=*letter;

DELAYMS(20);

letter++;

void SER_CHAR(char z)

SBUF=z;

DELAYMS(20);

void DELAYMS(unsigned intitime)

unsignedintx,y;

for(x=0;x<itime;x++)

for(y=0;y<1275;y++);

void LCD_KEYPAD(void)

P2=0x0F;

if(keypress())

switch(P2)
 {

case 0x07:col=0;break;

case0x0B:col=1;break;

case 0x0D:col=2;break;

case 0x0E:col=3;break;

P2 = 0xF0;

switch(P2)

case 0x70:row=3;break;

case 0xB0:row=2;break;

case 0xD0:row=1;break;

case 0xE0:row=0;break;

key_store=(KEY_PAD[col][row]);

fkey=1;

P2 = 0x0F;

DELAYMS(50);

intkeypress()

R0=R1=R2=R3=0;

if(C0&C1&C2&C3)
 return0;

else

return 1;

6. SOFTWARE DESCRIPTION
• PROTEUS SOFTWARE is sued for the simulation of circuit.

• CODING USED: Embedded C Language with the implementation of Keil Software.

• USB programmer Avapro + was used to burn the code in microcontroller

• Progisp Flash tool

7. ADVANTAGES
• No keys to be lost, stolen or occupied.

• Can be locked using keypad.

• Automatic door opening.

• Gives an indication for unauthorized entry.

• Totally cost efficient.

 8. DISADVANTAGES
• Currently if the personal identification number is somehow forgotten the system could not
be accessed.

• Powered by electricity may not function properly in the case of a power failure.

9.APPLICATIONS
• Used to automate the door locking process, so the user need not to carry the door lock keys.

• Used in mobile phones for security purposes

• Used in bank lockers

• Used in applications like lift, telephone locking, refrigerators etc

10. FUTURE SCOPE

• We can send this data to a remote location using mobile or internet.

• We can add fingerprint sensor so entry will be allowed for the authorized person using their
fingerprints.

• We can add fire, wind and LPG sensors so that in case of accident, the doors will
automatically open.

11. CONCLUSION
GSM based door locking system is used in the places where we need more security. It can
also be used to secure lockers and other protective doors. The system comprises a number
keypad and the keypads are connected to the 8bit microcontroller AT89S52. The
microcontroller continuously monitor the keypad and if somebody enters the password it will
check the entered password with the password which was stored in the memory and if it they
are same then the microcontroller will switch on the corresponding device. The system will
allow the person who knows the password and it will not allow who don’t know the
password.

12.BIBLIOGRAPHY
TEXT BOOKS REFERRED

• The 8051 Microcontroller and Embedded Systems by Muhammad Ali Mazidi and Janice
Gillispie Mazidi

• The 8051 Microcontroller Architecture, Programming & Applications by Kenneth J. Ayala

• Electronic Components by D. V. Prasad; Goldsmith, Wireless Communications,

Cambridge Press, 2005.

• S. Haykin, Communication Systems, Wiley, NewYork, 2002.

WEBSITES REFERRED

• www.allthedatasheets.com
• www.atmel.com
• www.microcontroller.com
• www.howstuffworks.com