28-01-2013, 02:46 PM
GSM Based Home Security System
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Abstract
Home security has been a major issue where crime is increasing and everybody wants to
take proper measures to prevent intrusion. In addition there was a need to automate home
so that user can take advantage of the technological advancement in such a way that a
person getting off the office does not get melted with the hot climate.
Introduction
The project is aimed at developing the security of Home against Intruders , Gas Leak and
Fire . In any of the above three cases any one met while you are out of your home than
the device sends SMS to the emergency no provided to it.
The report consists of a background into the area of 8051 microcontroller and mobile
communication, how they are interfaced to each other and AT (Attention) commands set
used in communication.
THEORY OF OPERATION
In this project we interfaced 8051 microcontroller with Motorola’s C168 GSM
mobile phone to decode the received message and do the required action. The
protocol used for the communication between the two is AT command.
The microcontroller pulls the SMS received by phone, decode it, recognizes the
Mobile no. and then switches on the relays attached to its port to control the
appliances. After successful operation, controller sends back the
acknowledgement to the user’s mobile through SMS.
AT-Command set
The following section describes the AT-Command set. The commands can be tried out by
connecting a GSM modem to one of the PC’s COM ports. Type in the test-command,
adding CR + LF (Carriage return + Line feed = \r\n) before executing. Table gives an
overview of the implemented AT-Commands in this application. The use of the
commands is described in the later sections.
A BRIEF INTRODUCTION TO 8051
MICROCONTROLLER:
When we have to learn about a new computer we have to familiarize about the
machine capability we are using, and we can do it by studying the internal hardware
design (devices architecture), and also to know about the size, number and the size of the
registers.
A microcontroller is a single chip that contains the processor (the CPU), nonvolatile
memory for the program (ROM or flash), volatile memory for input and output
(RAM), a clock and an I/O control unit. Also called a "computer on a chip," billions of
microcontroller units (MCUs) are embedded each year in a myriad of products from toys
to appliances to automobiles. For example, a single vehicle can use 70 or more
microcontrollers. The following picture describes a general block diagram of
microcontroller.
89s52:
The AT89S52 is a low-power, high-performance CMOS 8-bit microcontroller
with 8K bytes of in-system programmable Flash memory. The device is manufactured
using Atmel’s high-density nonvolatile memory technology and is compatible with the
industry-standard 80C51 instruction set and pinout. The on-chip Flash allows the
program memory to be reprogrammed in-system or by a conventional nonvolatile
memory pro-grammer. By combining a versatile 8-bit CPU with in-system programmable
Flash on a monolithic chip, the Atmel AT89S52 is a powerful microcontroller, which
provides a highly flexible and cost-effective solution to many, embedded control
applications. The AT89S52 provides the following standard features: 8K bytes of Flash,
256 bytes of RAM, 32 I/O lines, Watchdog timer, two data pointers, three 16-bit
timer/counters, a six-vector two-level interrupt architecture, a full duplex serial port, onchip
oscillator, and clock circuitry. In addition, the AT89S52 is designed with static logic
for operation down to zero frequency and supports two software selectable power saving
modes. The Idle Mode stops the CPU while allowing the RAM, timer/counters, serial
port, and interrupt system to continue functioning. The Power-down mode saves the
RAM con-tents but freezes the oscillator, disabling all other chip functions until the next
interrupt