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GSM BASED HOME AUTOMATION 1

CHAPTER 1

INTRODUCTION

1.0 EMBEDEDD SYSTEMS

An embedded system is an application that contains at least one programmable

computer (typically in the form of a microcontroller, a microprocessor or digital signal

processor chip) and which is used by individuals who are, in the main, unaware that the

system is computer-based.

Typical examples of embedded applications that are constructed using the techniques

discussed in this book include:

Mobile phone systems (including both customer handsets and base stations).

Automotive applications (including braking systems, traction control, airbag

release systems, engine-management units, steer-by-wire systems and cruise

control applications).

Domestic appliances (including dishwashers, televisions, washing machines,

microwave ovens, video recorders, security systems, garage door controllers).

Aerospace applications (including flight control systems, engine controllers,

autopilots and passenger in-flight entertainment systems).

Medical equipment (including anesthesia monitoring systems, ECG monitors,

drug delivery systems and MRI scanners).

Defence systems (including radar systems, fighter aircraft flight control systems,

radio systems and missile guidance systems).


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1.1 What is meant by Home Automation?

Automation means the act of implementing the control of equipment

with advanced technology; usually involving electronic hardware . Home Automation

means controlling of home appliances remotely when the user is away from the place and

to operate devices while we are not able to access them physically. Here we used GSM

technology so the controlling of home appliances is done through SMS. An automated

home is sometimes called a smart home. The motivation is to facilitate the users to

automate their homes having ubiquitous access. The use of home automation technology

is to become as common place as owning a DVD player is today. The capabilities of

home automation are endless. Audio, video, home theater, lighting, blinds, air-

conditioning, to name a few can be integrated and operated remotely.

1.2Need of Home Automation?

The main need is forgetting to switch of the devices when we live home.

Activating our air-conditioning from work, so our home is comfortable when we step

through the door on your arrival home. Operating our lights and sound remotely to give

the appearance that our home is occupied when we are away. Home automation is very

popular these days and it is common to read in magazines about its marvels. With state

of the art technology it is possible to achieve home automation with remote control and

monitoring via GSM phones. This is enough to irrigate plants, to monitor old persons, to

switch ON or OFF lights, to open an electric gate, to interface a burglar alarm in order to

send SMS messages in case of intrusion. You can send an SMS and set the temperature at

the correct value 1 hour before going home. Another important feature is the AC power

monitor. Therefore this paper proposes a system that allows user to be control home

appliances via SMS using GSM technology so that we can operate from anywhere.


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1.3 PROJECT OVERVIEW

Working:

Fig.1 Basic working of the system

The Basic working of the system follow below steps:

1. User sends commands via SMS

2. Mobile at the system transfers it to Micro controller

3. The Microcontroller operates the Devices according to the command received.

The working model is explained as:-

GSM Modem: GSM modem is a plug and play device and is attached to the

microcontroller which communicates via RS232 port. GSM modem is a bridge

responsible for enabling/ disabling of SMS capability.

Cell Phone: Mobile device communicates with the GSM Modem via radio waves.

The mode of communication is wireless and mechanism works on the GSM

technology. Cell phone has a SIM card and a GSM subscription. This cell phone

number is configured on the system. User transmits instructions via SMS and the

system takes action against those instructions.


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1.4 ADVANTAGES

The main advantages of Home automation are

Global Range

Low Cost

Low Power Requirement

This can be explained in below:

Our mini project has many advantages such as remote controlling of home

appliances, availability and ease of users. The user can get alerts anywhere through the

GSM technology thus making the system location independent. The system contains low

cost components easily available which cuts down the overall system cost.

Moreover system alerts user about breach via SMS providing home security also it

allows secure access due to pre-configured number. The ease of deployment is due to

wireless mode of communication.

GSM technology provides the benefit that the system is accessible in remote areas

as well. The system reliability increases due to the useful features such as battery level

checking, charging status and signal strength indicating the system about threats. The

system integration is simple and is also scalable and extensible. The auto-configuration

capability allows the system auto enabling/disabling of certain features. As we are using

gsm technology we can operate our home from any where .

1.5 APPLICATIONS

Home automation

Office automation.


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CHAPTER 2

SYSTEM MODEL

2.1 BASIC MODEL OF A SYSTEM

load

GSMMobile

8051

MICROCONTROLLER

GSM

MODEM

LCD

RELAY

GSM

MODEM

POWER

SUPPLY


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2.2 CIRCUIT DIAGRAM


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2.3 REQUIREMENTS & IMPLEMENTATION

The Different Modules required for implementing GSM Based Home

Automation are

1. 8051 Microcontroller

2. GSM Module

3. MAX 232 IC

4. LCD Display

5. Relay

6. Load (electrical lights or any other)

Implementation Devices are connected to an embedded system.

The embedded system is programmed to control the devices according to

commands from a remote.

2.3.1 GSM RANGES

GSM, the Global System for Mobile communications, is a digital cellular

communications system, which has rapidly gained acceptance and market share

worldwide, although it was initially developed in a European context. In addition to digital

transmission, GSM incorporates many advanced services and features, including ISDN

compatibility and worldwide roaming in other GSM networks. The advanced services and

architecture of GSM have made it a model for future third-generation cellular systems,

such as UMTS. This paper will give an overview of the services offered by GSM, the

system architecture, the radio transmission structure, and the signaling functional

architecture


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GSM carrier frequencies

GSM networks operate in a number of different carrier frequency ranges

(separated into GSM frequency ranges for 2G and UMTS frequency bands for 3G), with

most 2G GSM networks operating in the 900 MHz or 1800 MHz bands. Where these

bands were already allocated, the 850 MHz and 1900 MHz bands were used instead (for

example in Canada and the United States). In rare cases the 400 and 450 MHz frequency

bands are assigned in some countries because they were previously used for first-

generation systems.Most 3G networks in Europe operate in the 2100 MHz frequency

band. Regardless of the frequency selected by an operator, it is divided into timeslots for

individual phones to use. This allows eight full-rate or sixteen half-rate speech channels

per radio frequency. These eight radio timeslots (or eight burst periods) are grouped into

a TDMA frame. Half rate channels use alternate frames in the same timeslot. The channel

data rate for all 8 channels is 270.833 kbit/s, and the frame duration is 4.615 ms.

The transmission power in the handset is limited to a maximum of 2 watts in

GSM850/900 and 1 watt in GSM1800/1900.

2.3.2 RS232

In order to connect micro controller or a PC to GSM or ZIGBEE

modem a serial port is used. Serial, is a very common protocol for device communication

that is standard on almost every PC. Most computers include RS-232 based serial ports.

Serial is also a common communication protocol that is used by many devices for

instrumentation. In serial communication, the data is sent one bit at a time where as in

parallel communication; the data is sent a byte or more at time. Serial communication uses

a single data line where as the parallel communication uses 8 bit data line, this makes

serial communication not only inexpensive but also makes it possible for two computers

located in two different cities to communicate over the telephone.
http://en.wikipedia.org/wiki/GSM_frequency_rangeshttp://en.wikipedia.org/wiki/UMTS_frequency_bandshttp://en.wikipedia.org/wiki/2Ghttp://en.wikipedia.org/wiki/Canadahttp://en.wikipedia.org/wiki/United_Stateshttp://en.wikipedia.org/wiki/3Ghttp://en.wikipedia.org/wiki/Time_division_multiplexinghttp://en.wikipedia.org/wiki/Radio_frequencyhttp://en.wikipedia.org/wiki/Burst_transmissionhttp://en.wikipedia.org/wiki/Time_division_multiple_accesshttp://en.wikipedia.org/wiki/Time_division_multiple_accesshttp://en.wikipedia.org/wiki/Burst_transmissionhttp://en.wikipedia.org/wiki/Radio_frequencyhttp://en.wikipedia.org/wiki/Time_division_multiplexinghttp://en.wikipedia.org/wiki/3Ghttp://en.wikipedia.org/wiki/United_Stateshttp://en.wikipedia.org/wiki/Canadahttp://en.wikipedia.org/wiki/2Ghttp://en.wikipedia.org/wiki/UMTS_frequency_bandshttp://en.wikipedia.org/wiki/GSM_frequency_ranges


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RS-232 WAVEFORM

TTL/CMOS Serial Logic Waveform

The diagram above shows the expected waveform from the UART when using the

common 8N1 format. 8N1 signifies 8 Data bits, No Parity and 1 Stop Bit. The RS-232

line, when idle is in the Mark State (Logic 1). A transmission starts with a start bit which

is (Logic 0). Then each bit is sent down the line, one at a time. The LSB (Least

Significant Bit) is sent first. A Stop Bit (Logic 1) is then appended to the signal to make

up the transmission.

The data sent using this method, is said to be framed. That is the data is framed between

a Start and Stop Bit.

RS-232 Voltage levels

1. +3 to +25 volts to signify a "Space" (Logic 0).

2. -3 to -25 volts for a "Mark" (logic 1).

3. Any voltage in between these regions (i.e. between +3 and -3 Volts) is undefined.

The data byte is always transmitted least-significant-bit first.

The bits are transmitted at specific time intervals determined by the baud rate of the

serial signal. This is the signal present on the RS-232 Port of your computer, shown

below.

RS-232 Logic Waveform

RS-232 LEVEL CONVERTER

Standard serial interfacing of microcontroller (TTL) with PC or any RS232C

Standard device , requires TTL to RS232 Level converter . A MAX232 is used for this

purpose. It provides 2-channel RS232C port and requires external 10uF capacitors.
http://www.arcelect.com/rs232.htmhttp://www.bsc.nodak.edu/electron/rs232.htmhttp://www.bsc.nodak.edu/electron/rs232.htmhttp://www.arcelect.com/rs232.htm


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The driver requires a single supply of +5V .

MICROCONTROLLER INTERFACING WITH RS-232 STANDARDDEVICES


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CHAPTER 3

HARDWARE DESCRIPTION

3.1Introduction To Microcontroller:

Micro controller is the heart of total system. The micro controller controls all

the devices connected in the diagram. Micro controller sends pulses to all the devices,

which are connected to it.We can program it in any language i.e., in assembly or C or

C++, depending upon the user. In this flash memory is more compatible with others. In

our design, this controller is compatible and also reliable one.

Micro Controller 8051:

In 1981, Intel Corporation introduced an 8-bit microcontroller called

the 8051. This microcontroller had 128 bytes of RAM, 4K bytes of on-chip ROM, two

timers, one serial port, and four ports (each 8-bits wide) all on a single chip. The 8051 is

an 8-bit processor, meaning that the CPU can work on only 8 bits of data at a time. Data

larger than 8 bits has to broken into 8-bit pieces to be processed by the CPU. The 8051has a total of four I/O ports, each 8 bits wide. Although the 8051 can have a maximum of

64K bytes of on chip ROM, many manufacturers have put only 4K bytes on the chip.

There are different flavors of the 8051 in terms of speed and amount of on-chip ROM, but

they are all compatible with the original 8051 as far as the instructions are concerned.

Features :The basic architecture consists of the following features:

an eight bit ALU

32 discrete I/O pins (4 groups of 8) which can be individually accessed

two 16 bit timer/counters

full duplex UART

6 interrupt sources with 2 priority levels

128 bytes of on board RAM

separate 64K byte address spaces for DATA and CODE memory


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Pin diagram:

Pin Description:

VCC: Supply voltage.

GND: Ground.

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.

Port 1: Port 1 is an 8-bit bidirectional I/O port with internal pull-ups. The Port 1output buffers can sink/source four TTL inputs. When 1s are written to Port 1 pins,


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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. Port 1 also receives the low-order

address bytes during Flash programming and verification

Port pin Alternate functions

P1.0 T2(EXTERNAL COUNT INPUT TO TIMER/COUNTER 2), CLOCK-OUT

P1.1 T2EX(TIMER/COUNTER 2 CAPTURE/RELOAD TRIGGER AND DIRECTION CONTROL)

P1.5 MOSI(USED FOR IN-SYSTEM PROGRAMMING)

P1.6 MISO(USED FOR IN-SYSTEM PROGRAMMING)

P1.7 SCK(USED FOR IN-SYSTEM PROGRAMMING)

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 use 16-bit addresses (MOVX @

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

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

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

address bits and some control signals during Flash programming and verification.

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 following table.

Port pin Alternate functions

P3.0 RXD (serial input port)


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P3.1 TXD (serial output port)

P3.2 INT0 (external interrupt 0)

P3.3 INT1 (external interrupt 1)

P3.4 T0 (timer 0 external input)

P3.5 T1 (timer 1 external input)

P3.6 WR (external data memory write strobe)

P3.7 RD (external data memory read strobe)

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.

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 up to


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

reset. EA should be strapped to VCCfor internal program executions.This pin also

receives the 12-volt programming enable 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

Pin DescriptionPin Number Description

18 P1.0 - P1.7 - Port 1

9 RST - Reset

1017 P3.0 - P3.7 - Port 3

18 XTAL2 - Crystal

19 XTAL1 - Crystal

20 GND - Ground

2128 P2.0 - P2.7 - Port 2

29 PSEN - Program Store Enable30 ALE - Address Latch Enable

31 EA - External Access Enable

3239 P0.7 - P0.1 - Port 0

40 Vcc - Positive Power Supply


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3.2 GSM MODEM

Global system for mobile communication (GSM) is a globally accepted

standard for digital cellular communication. GSM is the name of a standardization group

established in 1982 to create a common European mobile telephone standard that would

formulate specifications for a pan-European mobile cellular radio system operating at 900

MHz. It is estimated that many countries outside of Europe will join the GSM partnership.

3.2.1Description:

A GSM modem can be an external modem device, such as the Wavecom

FASTRACK Modem. Insert a GSM SIM card into this modem, and connect the modem

to an available serial port on your computer. A GSM modem can be a PC Card installed

in a notebook computer, such as the Nokia Card Phone. A GSM modem could also be a

standard GSM mobile phone with the appropriate cable and software driver to connect to a

serial port on your computer. Phones such as the Nokia 7110 with a DLR-3 cable, or

various Ericsson phones, are often used for this purpose.

A dedicated GSM modem (external or PC Card) is usually preferable to a GSM

mobile phone. This is because of some compatibility issues that can exist with mobile

phones. For example, if you wish to be able to receive inbound MMS messages with your

gateway, and you are using a mobile phone as your modem, you must utilize a mobile

phone that does not support WAP push or MMS. This is because the mobile phone

automatically processes these messages, without forwarding them via the modem

interface. Similarly some mobile phones will not allow you to correctly receive SMS text

messages longer than 160 bytes (known as concatenated SMS or long SMS). This is

because these long messages are actually sent as separate SMS messages, and the phone

attempts to reassemble the message before forwarding via the modem interface

When you install your GSM modem, or connect your GSM mobile phone to the

computer, be sure to install the appropriate Windows modem driver from the device

manufacturer. To simplify configuration, the Now SMS/MMS Gateway will communicate

with the device via this driver. An additional benefit of utilizing this driver is that you can

use Windows diagnostics to ensure that the modem is communicating properly with the

computer


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Figure: GSM modem

Now SMS/MMS gateway can simultaneously support multiple modems, provided

that your computer hardware has the available communications port resources

Global System for Mobile Communications (GSM) modems are specialized types of

modems that operate over subscription based wireless networks, similar to a mobile

phone. A GSMmodemaccepts a Subscriber Identity Module (SIM) card, and basically

acts like a mobile phone for acomputer. Such a modem can even be a dedicated

mobile phone that the computer uses for GSM network capabilities. A GSM modem is

a wireless modem that works with a GSM wireless network. A wireless modem

behaves like a dial-up modem. The GSM modem can be an external device or a PC

Card / PCMCIA Card. Typically, an external GSM modem is connected to a computer

through a serial cable or a USB cable. It is a

Most Popular Mobile TechnologyLaunch -1991by Radio linja in Finland

Frequencies -900/1800MHz

RangeGlobal

InterfaceSubscriber Identity Module

ServicesSMS, MMS, GPRS, EDGE
http://www.wisegeek.com/what-is-gsm.htmhttp://www.wisegeek.com/what-is-gsm.htmhttp://www.wisegeek.com/what-is-gsm.htmhttp://www.wisegeek.com/what-is-a-modem.htmhttp://www.wisegeek.com/what-is-a-modem.htmhttp://www.wisegeek.com/what-is-a-modem.htmhttp://www.wisegeek.com/what-is-a-computer.htmhttp://www.wisegeek.com/what-is-a-computer.htmhttp://www.wisegeek.com/what-is-a-computer.htmhttp://www.wisegeek.com/what-is-a-computer.htmhttp://www.wisegeek.com/what-is-a-modem.htmhttp://www.wisegeek.com/what-is-gsm.htm


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3.2.2 AT Commands :

In addition to the standard AT commands, GSM modems support an

extended set of AT commands. These extended AT commands are defined in the GSMstandards. With the extended AT commands, you can do things like:

* Reading, writing and deleting SMS messages.

* Sending SMS messages.

* Reading, writing and searching phone book entries.

AT commands features:

Line settings: A serial link handler is set with the following default values. Autobaud,

8 bits data, 1 stop bit, no parity, flow control.

Command line: Commands always start with AT (which means attention) and finish

with a character. .

Send message +CMGS

Description :

The field is the address of the terminal to which the message is sent. To

send the message, simply type, character (ASCII 26). The text can contain all

existing characters except and (ASCII 27). This command can be aborted

using the character when entering text. In PDU mode, only hexadecimal characters

are used (09,AF).

Syntax :Command syntax in text mode : AT+CMGS= [ , ]


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The message reference, , which is returned to the application is allocated by

the product. This number begins with 0 and is incremented by one for each outgoing

message (successful and failure cases); it is cyclic on one byte (0 follows 255).

Note: this number is not a storage number - outgoing messages are not stored.

Delete message +CMGD

This command is used to delete one or several messages from preferred message

storage (BM SMS CB RAM storage, SM SMSPP storage SIM storage or SR

SMS Status-Report storage).

Syntax : Command syntax :AT+CMGD= [.]


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3.3. LIQUID CRYSTAL DISPLAY(LCD):

An LCD consists of two glass panels, with the liquid crystal material

sand witched in between them. The inner surface of the glass plates are coated withtransparent electrodes which define the character, symbols or patterns to be displayed

polymeric layers are present in between the electrodes and the liquid crystal, which

makes the liquid crystal molecules to maintain a defined orientation angle. One each

polarisers are pasted outside the two glass panels. These polarisers would rotate the

light rays passing through them to a definite angle, in a particular direction

The LCD is used for the purpose of displaying the words which

we are given in the program code. This code will be executed on microcontroller chip.

By following the instructions in code the LCD display the related words.

Fig. LCD Display

The LCD display consists of two lines, 20 characters per line that is interfaced with

the PIC16F73.The display contains two internal byte-wide registers, one for

commands (RS=0) and the second for characters to be displayed (RS=1). It also

contains a user-programmed RAM area (the character RAM) that can be

programmed to generate any desired character that can be formed using a dot

matrix. To distinguish between these two data areas, the hex command byte 80 will

be used to signify that the display RAM address 00h will be chosen Port1 is used

to furnish the command or data type, and ports 3.2 to 3.4 furnish register select and

read/write levels.


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3.3.1 PIN DIAGRAM

The Pin diagram for LCD is shown in the following fig and the pin description is also

explained in Table

Pins Description

1 "Vss" - Ground

2 "Vcc" - +5v power supply

3 "Vee" - Contrast Voltage

4 "R/S" - Instruction/Register Select

5 "R/W" - Read/Write LCD Registers

6 "E" - Enable

714 Data I/O Pins

GN

+5

VD

A K

1 2 3 15 16

4 5 6 7 8 9 10 11 12 13 14

2x16 Liquid Crystal Display

RS R/w

EnD0 D2 D3 D5 D7D6D4D1


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3.2.2 INTERFACING LCD TO 8051

The 44780 standard requires 3 control lines as well as either 4 or 8 I/O lines for

the data bus. The user may select whether the LCD is to operate with a 4-bit data bus or

an 8-bit data bus.

If a 4-bit data bus is used, the LCD will require a total of 7 data lines.

If an 8-bit data bus is used, the LCD will require a total of 11 data lines.

The three control lines are EN, RS, and RW.

Note that the EN line must be raised/lowered before/after each instruction sent to the

LCD regardless of whether that instruction is read or write, text or instruction. In short,

you must always manipulate EN when communicating with the LCD. EN is the LCD's

way of knowing that you are talking to it. If you don't raise/lower EN, the LCD doesn't

know you're talking to it on the other lines.


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3.4.RELAYS

A relay is an electromagnetic switch. In other words it is activated when a

current is applied to it. Normally a relay is used in a circuit as a type of switch (as you

will see below). There are different types of relays and they operate at different voltages.

Relays are switching devices, it has two fixed positions i.e., ON and OFF positions.

Circuit symbol of relay:

NO -"Normally Open", NC -"Normally Closed".

COM -common connection for double pole switches

A relay will switch one or morepoles, each of whose contacts can be thrown by

energizing the coil in one of three ways:

Normally-open (NO) contacts connect the circuit when the relay is activated; the

circuit is disconnected when the relay is inactive. It is also called a Form

A contact or "make" contact.

Normally-closed (NC) contacts disconnect the circuit when the relay is activated;

the circuit is connected when the relay is inactive. It is also called a Form

B contact or "break" contact.

Change-over (CO), or double-throw (DT), contacts control two circuits: one

normally-open contact and one normally-closed contact with a common terminal.

It is also called a Form Ccontact or "transfer" contact ("break before make"). If

this type of contact utilizes a "make before break" functionality, then it is called

a Form D contact.


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Electromagnetic relay:

Out of different types of relays, Most commonly used relay is

Electromagnetic Relay.The electromagnetic relay consists of a multi-turn coil, wound onan iron core, to form an electromagnet. When the coil is energized, by passing current

through it, the core becomes temporarily magnetized.

The magnetized core attracts the iron armature. The armature is pivoted which causes it to

operate one or more sets of contacts. When the coil is de-energized the armature and

contacts are released. The coil can be energized from a low power source such as a

ransistor while the contacts can switch high powers such as the mains supply. The relay

can also be situated remotely from the control source.

Relays can generate a very high voltage across the coil

when switched off. This can damage other components

in the circuit. To prevent this a diode is connected

across the coil. The cathode of the diode is connected to

the most positive end of the coil.The springsets

(contacts) can be a mixture of n.o, n.c and c.o. Look at

the page on switches to see how they can be used in

circuits. Various coil operating voltages (ac and dc) are

available.The actual contact points on the springsets are available for high current and

low current operation. The REED RELAY has a much faster operation than the relays

described above.


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The following designations are commonly encountered:

SPST Single Pole Single Throw. These have two terminals which can be

connected or disconnected. Including two for the coil, such a relay has four

terminals in total. It is ambiguous whether the pole is normally open or normally

closed. The terminology "SPNO" and "SPNC" is sometimes used to resolve the

ambiguity.

SPDTSingle Pole Double Throw. A common terminal connects to either of two

others. Including two for the coil, such a relay has five terminals in total.

DPSTDouble Pole Single Throw. These have two pairs of terminals. Equivalent

to two SPST switches or relays actuated by a single coil. Including two for the

coil, such a relay has six terminals in total. The poles

may be Form A or Form B (or one of each).

DPDTDouble Pole Double Throw. These have two

rows of change-over terminals. Equivalent to two

SPDT switches or relays actuated by a single coil.

Such a relay has eight terminals, including the coil.

The "S" or "D" may be replaced with a number, indicating

multiple switches connected to a single actuator. For example

4PDT indicates a four pole double throw relay (with 14

terminals).

EN 50005 are among applicable standards for relay terminal numbering; a typical EN

50005-compliant SPDT relay's terminals would be numbered 11, 12, 14, A1 and A2 for

the

C, NC, NO, and coil connections, respectively.

Fig. SPST, PDT, DPST, DPDT diagrams

Circuit symbols of relays. "C" denotes the common terminal in SPDT and DPDT types


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3.5. POWER SUPPLY:

The power supply circuits built using filters, rectifiers, and then voltage

regulators. Starting with an ac voltage, a steady dc voltage is obtained by rectifyingthe ac voltage, then filtering to a dc level, and finally, regulating to obtain a desired

fixed dc voltage. The regulation is usually obtained from an IC voltage regulator unit,

which takes a dc voltage and provides a somewhat lower dc voltage, which remains

the same even if the input dc voltage varies, or the output load connected to the dc

voltage changes. The block diagram of power supply is shown in fig below.

AC I/P

Transformer Rectifier Filter Regulator Load

Block diagram of power supply

Transformer

The potential transformer will step down the power supply voltage (0-230V) to (0-

6V) level. Then the secondary of the potential transformer will be connected to the

precision rectifier, which is constructed with the help of opamp. The advantages of

using precision rectifier are it will give peak voltage output as DC, rest of the circuits

will give only RMS output.


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Bridge rectifier

Bridge rectifier is used to maintain the proper DC polarity at the input to the

circuit, irrespective of telephone line polarity. It comprises of four diodes connectedto form a bridge. It uses the entire AC wave (both positive and negative sections).

1.4V is used up in the bridge rectifier because each diode uses 0.7V when conducting

and there are always two diodes conducting, as shown in fig below.

IN4007 AC I/P

IN4007

IN4007 IN4007

O/P

Fig: Bridge rectifier

IC Voltage Regulators:

Voltage regulators comprise a class of widely used ICs. Regulator IC units contain the

circuitry for reference source, comparator amplifier, control device, and overload

protection all in a single IC. Although the internal construction of the IC is somewhat

different from that described for discrete voltage regulator circuits, the external

operation is much the same. IC units provide regulation of either a fixed positive

voltage, a fixed negative voltage, or an adjustably set voltage.


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Three terminal Voltage Regulators:

Fig shows the basic connection of a three-terminal voltage regulator IC to a load. The

fixed voltage regulator has an unregulated dc input voltage, V in, applied to one input

terminal, a regulated output dc voltage, Vout, from a second terminal, with the third

terminal connected to ground.

From Transformer Vout

Secondary Vin

GND

Fig.: Fixed Voltage Regulator

The series 78 regulators provide fixed regulated voltages from 5 to 24 V.

Unregulated input voltage Vin is filtered by capacitor C1and connected to the ICs IN

terminal. The ICs OUT terminal provides a regulated + 12V which is filtered by

capacitor C2. The third IC terminal is connected to ground (GND). The Power

Section consists of a centre tapped step-down transformer, which is used to step down

the 230V AC into 12V. This 12V is given to bridge rectifier. The output from the

diodes is a full-wave rectifier output. Any unwanted ac ripples are filtered out using a

filter. This is fed to the 7805 voltage regulator that gives anoutput voltage of +5v.

.

Fig.:Circuit Diagram of Power Supply

IN OUT

7805

GND


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CHAPTER 4

PROJECT DEVELOPMENT

4.1.INTRODUCTION TO KEIL

This technical note describes the use of the Keil uVision Integrated Development

Environment in the development of a C based, MicroController application.

The Keil 8052 compiler package includes uVision2 which is an Integrated Development

Environment (IDE) along with all the utilities you may need to create embedded

application programs for the MicroController family.

CREATING A PROJECT

Before writing any C-code, a project associated with our code needs to be created. This is

done by first creating a new folder in the Keil directory in which your project will be

saved. Next the Keil uV2 application can be launched and a new project is created. This is

achieved by completing the following steps.

Create a new project. From the main window, choose the Project menu and select New

project. A new window appears as shown below in Figure 1.


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A new window appears as shown in figure 2 below and you are now required to configure

your setup to target the specific MicroController device you wish to use (in this example

we will be using the ADuC834) and the output file format generated after the compilation

stage. This is achieved by completing the following steps.

Next, you need to configure your target output options. This is done by clicking on the

options for target item located inthe project pull-down menu. Alternatively you can

select this option by clicking on the icon from the compile toolbarsituated at the top of

the screen and shown in figure 3 below.

A new window appears as shown in figure 4. Enable the option to Create Hex File by

ticking the check-box and pressing OK as shown circled in figure 4 below.


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Now you can begin writing your C program. In the main window, choose the File pull-

down menu and select New. A new window named will appear on the screen.

Type the C source code that is included in Appendix A of this tech note into the window. Once you've typed all the code, again choose the File pull-down menu and

select Save.


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COMPILING A C PROGRAM

Our C code is compiled by selecting Build Target from the Project pull-down menu on

the main tool-bar. The compile option can also be initiated by selecting the F7 special

function key or by clicking on the Build Target icon in the compile toolbar as shown in

figure 6 below.

If the compilation completes successfully a message indicating that the compile job has

completed with 0 errors will appear in the build dialog screen. Sometimes warnings may

be generated for information purposes to indicate multiple function calls etc.

If the resultant compilation message indicates that there were 1 or more errors, then the

output files will not be created. In this case, the file has been entered incorrectly and

clicking directly on any error message forces uVision to highlight where in the code the

error has occurred.

4.2.SIMULATING C-SOURCE CODE

Another powerful feature of the uVision2 IDE is that it allows you to run your code in a

MicroController specific simulation environment. To start a simulation session you

simply click on the on Start/Stop Debug Session option available from the Debug pull-

down menu. Alternatively you can press or the Debug icon available in the

File toolbar as shown in figure 7.


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CREATING THE SIMULATION ENVIRONMENT

The following steps will allow you to create a generic simulation environment that you

may want to further customize to your own requirements. From the top Debug toolbar,

click on the icon buttons that are shown in figure 8 below which open a Serial I/O

peripheral window as well as a code Performance Analyzer window.

Note: If the Debug toolbar does not appear at the top of the screen, simply select the

Debug Toolbar option availablefrom the View pull-down menu.


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4.3SOURCE CODE

Program :

#include

void transmit(unsigned char *);

void serial_init();

sbit led=P1^3;

unsigned char *tx_dat;

unsigned char a[70],y[5];

unsigned char b[3],c[3]={"Son"},c1[3]={"Sof"};

int i=0,j=0,k=0,x=0,l=0,Z=0;

void main()

{

LCD_Init();

lprintf("Gsm-recv",1,1);

Delay(100);

LCD_Cmd(0x01);

led=0; //led off

serial_init();

///////////////// AT ///////////////////////

while(1)

{

LCD_Cmd(0x80);

tx_dat="at";

transmit(tx_dat); //Transmit AT command

SBUF=13; //Transmit ENTER

j=0;

while(j


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LCD_Data(a[j]); //Display OK

LCD_Data(a[j+1]);

Z=1;

break;

}

j++;

}

if(Z==1)

{

Z=0;

loop:

while(1) /////RECEIVE//////

{

Delay(50); //delay

LCD_Cmd(0x01);

lprintf("send read command",1,1);

tx_dat="at+cmgr=1";

transmit(tx_dat); //Transmit READ command

SBUF=13; //Transmit ENTER

Delay(50);

j=0;

lprintf("wait for error",2,0);

while(j


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j=0;

Delay(50);

LCD_Cmd(0x01);

lprintf("reading message",1,1);

while(j


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lprintf("led off",1,1);

led=0; //led of

Delay(60);

}

b[0]='\0';

b[1]='\0';

b[2]='\0';

Delay(50);

LCD_Cmd(0x01);

lprintf("send delet command",1,1);

tx_dat="at+cmgd=1"; /////delete//////

transmit(tx_dat); //Trasmit delete command

SBUF=13; //Trasmit ENTER

j=0;

while(j


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int i;

while(x-->0)

{

for(i=0;i


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}

void transmit(unsigned char *tx)

{

while(*tx)

{

SBUF=*tx++;

Delay(15);

}

SBUF=13;

Delay(2);

TI=0;

i=0;

}

C51.h program:

#include

#include

// Device Mapping

#define LCD_Port P2

sbit LCD_RS=P1^0;

sbit LCD_RW=P1^1;

sbit LCD_EN=P1^2;

sbit LCD_BP=P0^7; // LCD Busy Pin

// Global variables

unsigned char bc=0,pflag=0,fstore=0;unsigned char xdata RData[100];

unsigned char xdata Msg[20];

// Functions Prototype Declaration

void lprintf(unsigned char *,unsigned char,unsigned char);

void LCD_Init();

void LCD_Cmd(unsigned char);

void LCD_Data(unsigned char);

void Delay_10ms();void Delay(int);


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void LCD_Busy();

void ClrLCD();

void SConfig(void);

void Send_Char(unsigned char);

void Send(unsigned char *);

/*----------------------------------------------*/

// To Clear LCD

/*----------------------------------------------*/

void ClrLCD()

{

LCD_Cmd(0x01);

}

/*----------------------------------------------*/

// Displaying String

/*----------------------------------------------*/

// Displaying String

void lprintf(char *str,unsigned char ln,unsigned char col)

{

static int li;

unsigned char line;

if(li==0)

{li=1;

LCD_Init();

}

switch(ln)

{

case 1:

line = 0x80;

break;

case 2:

line = 0xc0;break;

case 3:

line = 0x94;

break;

case 4:

line = 0xD4;

break;

}

LCD_Cmd(line+col-1);


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while(*str)

{

LCD_Data(*str);

str++;

}

}

/*----------------------------------------------*/

//LCD Initilization

void LCD_Init()

{

LCD_Cmd(0x30);

LCD_Cmd(0x30);

LCD_Cmd(0x30);LCD_Cmd(0x38);

LCD_Cmd(0x06);

LCD_Cmd(0x01);

LCD_Cmd(0x0c);

}

/*----------------------------------------------*/

// LCD Command Run

void LCD_Cmd(unsigned char cmd)

{

LCD_Busy();

LCD_Port=cmd;LCD_BP=0;

_nop_();

LCD_BP=1;

LCD_RS=0;

LCD_RW=0;

LCD_EN=1;

_nop_();

_nop_();

LCD_EN=0;

}

/*----------------------------------------------*///LCD Data Out Function

void LCD_Data(unsigned char dt)

{

LCD_Busy();

LCD_Port=dt;

LCD_BP=0;

_nop_();

LCD_BP=1;

LCD_RS=1;

LCD_RW=0;

LCD_EN=1;


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_nop_();

_nop_();

LCD_EN=0;

}

/*----------------------------------------------*/

// LCD BUSY Check Function

void LCD_Busy()

{

/*

LCD_Port=0xff;

LCD_RS=0;

LCD_RW=1;

while(1){

LCD_EN=0;

_nop_();

_nop_();

LCD_EN=1;

if(!LCD_BP)

break;

}

Delay(1);*/

unsigned int i;

for(i=0; i


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for(i=0; i


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RI=0;

if(t == 'A')

fstore =1;

if(fstore)

{

RData[bc++]=t;

RData[bc]='\0';

}

if(bc>40)

{

pflag=1;

fstore=0;bc=0;

}

// LCD_Data(RData[bc-1]);

// Send_Char(RData[bc-1]); // Uncomment this line to test the Serial

Interrupt.

}

}


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FUTURE ENHANCMENTS

In this project in future we can add a multimedia camera to see what is going

inside the home by sitting in office or somewhere.

It can be used for high security in banks and other organizations

Provision to store mobile numbers

Control of more devices

Theft Alert.

CONCLUSION

In the paper low cost, secure, ubiquitously accessible, auto-configurable, remotely

controlled solution for automation of homes has been introduced. The approach discussed

in the project is novel and has achieved the target to control home appliances remotely

using the SMS-based system satisfying user needs and requirements.GSM technology capable solution has proved to be controlled remotely, provide

home security and is cost-effective as compared to the previously existing systems. Hence

we can conclude that the required goals and objectives of HACS have been achieved.

In addition, which is an era when the number of mobile phone users growing at a

high rate, this system makes use of the mobile networks to provide the users with a

simple and cheap Home Automation System.


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REFERNCES

Reference Books:

The 8051 Microcontroller and Embedded Systems -Muhammad Ali Mazidi

The 8051 Micro-controller - Ayala

Programming and customizing the 8051 - Myke Predko

Websites:

www.atmel.com

www.analogicgroup.com

www.philips.com

www.google.com

www.gsmworld.com
http://www.atmel.com/http://www.atmel.com/

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