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Sms based appliance control system

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Apart from the efforts of me, the success of this training depends largely on the encouragement and guidelines of many others. I take this opportunity to express my gratitude to the people who have been instrumental in the successful completion of this project report.

I would like to show my greatest appreciation to Dr. Satinder Sharma of INDIAN INSTITUTE OF TECHNOLOGY MANDI HIMACHAL PRADESH. I can’t say thank you enough for his tremendous support and help. I feel motivated and encouraged every time I attend his meeting. Without his encouragement and guidance this training would not have materialized. Finally, I am indebted to all whosoever have contributed in this project.

A general-purpose embedded systems is that devices used to control, monitor or assist the operation of equipment, machinery or plant. “Embedded” reflects the fact that they are an integral part of the system and it is a combination of hardware and software to performs a specific task. Common examples of embedded systems include MP3 players, navigation systems on aircraft and intruder alarm systems. An embedded system can also be defined
as a single purpose computer. CLASSIFICATION

1. Small Scale Embedded Systems: These systems are designed with a single 8- or 16-bit microcontroller; they have little hardware and software complexities and involve board-level design. 2. Medium Scale Embedded Systems: These systems are usually designed with a single or few16- or 32-bit microcontrollers or DSPs or Reduced Instruction Set Computers (RISCs). These have both hardware and software complexities 3. Sophisticated Embedded Systems: Sophisticated embedded systems have enormous hardware and software complexities and may need scalable processors or configurable processors and programmable logic arrays. They are used for cutting edge applications that need hardware and software co-design and integration in the final system.

Embedded systems are designed to do some specific task, rather than be a general-purpose computer for multiple tasks. Some also have real-time performance constraints that must be met, for reasons such as safety and usability; others may have low or no performance requirements, allowing the system hardware to be simplified to reduce costs. Embedded systems are not always standalone devices. Many embedded systems consist of small, computerized parts within a larger device that serves a more general purpose. Similarly, an embedded system in an automobile provides a specific function as a subsystem of the car itself.

A processor is the heart of the embedded system. For an embedded system designer, knowledge of microprocessors and microcontrollers is a necessary.Processor has two essential units: 1.Program Flow Control Unit (CU)

2.Execution Unit (EU).
1.The CU includes a fetch unit for fetching instructions from the memory. 2.The EU has circuits that implement the instructions pertaining to data transfer operations and data conversion from one form toanother. The EU includes the Arithmetic and Logical Unit (ALU) and also the circuits that execute instructions for a program control task, say, halt, interrupt, or jump to another set of instructions. Itcan also execute instructions for a call or branch to another program and for a call to a function. A processor runs the cycles of fetch and execute. The instructions, defined in the processor instruction set, are executed in the sequence that they are fetched from the memory. An embedded system processor chip or core can be one of the following. a. Microprocessor.

b. Microcontroller( Embedded Processor).
c. Digital Signal Processor (DSP).

A microprocessor is a single VLSI chip that has a CPU and may also have some other units (forexamples, caches, floating point processing arithmetic unit, pipelining and super-scaling units) that are additionally present and that result in faster processing of instructions. b.) MICROCONTROLLER

A microcontroller is a single-chip VLSI unit (also called ‘microcomputer’) which, though having limited computational capabilities,possesses enhanced input-output capabilities and a number of on-chip functional units. c.)DIGITAL SIGNAL PROCESSOR

A digital signal processor (DSP) is an essential unit of an embedded system for a large number of applications needing processing of signals. Exemplary applications are in image processing, multimedia, audio, video, HDTV, DSP modem and telecommunication processing systems. DSPs also find use in systems for recognizing animage pattern or a DNA sequence fast. PERIPHERALS

Embedded Systems talk with the outside world via peripherals, such as: Serial Communication Interfaces (SCI): RS-232, RS-422, RS-485 etc. Synchronous Serial Communication Interface Universal Serial Bus (USB) Multi Media Cards (SD Cards, Compact Flash etc.)

Networks: Ethernet, Lon Works, etc.
Discrete IO: aka General Purpose Input /Output
Embedded system designers use compilers, assemblers, and debuggers to develop embedded system software. However, they may also use some more specific tools: In circuit debuggers or emulator.
Utilities to add a checksum or CRC to a program, so the embedded system can check if the program is valid. For systems using digital signal processing, developers may use a math workbench such as MATLAB, MathCad, Mathematica Custom compilers and linkers may be used to optimize specialized hardware. An embedded system may have its own special language or design tool, Another alternative is to add a real-time operating system or embedded operating system. MICROCONTROLLER

• Microcontroller (MC) may be called computer on chip since it has basic features of microprocessor with internal ROM, RAM, Parallel and serial ports within single chip. Or we can say microprocessor with memory and ports is called as microcontroller. This is widely used in washing machines,vcd player, microwave oven, robotics or in industries. • Microcontroller can be classified on the basis of their bits processed like 8bit MC, 16bit MC. • 8 bit microcontroller, means it can read, write and process 8 bit data. Ex. 8051 microcontroller. Basically 8 bit specifies the size of data bus. 8 bit microcontroller means 8 bit data can travel on the data bus or we can read, write process 8 bit data.

8051 Microcontroller Architecture
The 8051 Microcontroller was designed in 1980’s by Intel. Its foundation was on Harvard Architecture and was developed principally for bringing into play in Embedded Systems. At first it was created by means of NMOS technology but as NMOS technology needs more power to function therefore Intel re-intended Microcontroller 8051 employing CMOS technology and a new edition came into existence with a letter ‘C’ in the title name, for illustration: 80C51. These most modern Microcontrollers need fewer amount of power to function in comparison to their forerunners. There are two buses in 8051 Microcontroller one for program and other for data. As a result, it has two storage rooms for both program and data of 64K by 8 size. The microcontroller comprise of
8 bit accumulator & 8 bit processing unit. It also consists of 8 bit B register as majorly functioning blocks. It also has a number of other 8 bit and 16 bit registers. For internal functioning & processing Microcontroller 8051 comes with integrated built-in RAM. This is prime memory and is employed for storing temporary data. It is unpredictable memory i.e. its data can get be lost when the power supply to the Microcontroller switched OFF. Block Diagram of 8051 Microcontroller

8051 Microcontroller Block Diagram Explanation:
CPU (Central Processor Unit):
Central Processor Unit or CPU is the mind of any processing machine. It scrutinizes and manages all processes that are carried out in the Microcontroller. User has no power over the functioning of CPU. It interprets program printed in storage space (ROM) and carries out all of them and do the projected duty. Interrupts:

Interrupt is a sub-routine call that reads the Microcontroller’s key function or job and helps it to perform some other program which is extra important at that point of time. The characteristic of Interrupt is extremely constructive as it aids in emergency cases. Interrupts provides us a method to postpone or delay the current process, carry out a sub-routine task and then all over again restart standard program implementation. The Micro-controller 8051 can be assembled in such a manner that it momentarily stops or break the core program at the happening of interrupt. When sub-routine task is finished then the implementation of core program initiates automatically as usual. There are 5 interrupt supplies in 8051 Microcontroller, two out of five are peripheral interrupts, two are timer interrupts and one is serial port interrupt. Memory:

Micro-controller needs a program which is a set of commands. This program enlightens Microcontroller to perform precise tasks. These programs need a storage space on which they can be accumulated and interpret by Microcontroller to act upon any specific process. The memory which is brought into play to accumulate the program of Microcontroller is recognized as Program memory or code memory. In common language it’s also known as Read
Only Memory or ROM. Micro-controller also needs a memory to amass data or operands for the short term. The storage space which is employed to momentarily data storage for functioning is acknowledged as Data Memory and we employ Random Access Memory or RAM for this principle reason. Microcontroller 8051 contains code memory or program memory 4K so that is has 4KB Rom and it also comprise of data memory (RAM) of 128 bytes. Bus:

Fundamentally Bus is a group of wires which functions as a communication canal or mean for the transfer Data. These buses comprise of 8, 16 or more cables. As a result, a bus can bear 8 bits, 16 bits all together. There are two types of buses: 1. Address Bus: Microcontroller 8051 consists of 16 bit address bus. It is brought into play to address memory positions. It is also utilized to transmit the address from Central Processing Unit to Memory. 2. Data Bus: Microcontroller 8051 comprise of 8 bits data bus. It is employed to cart data.

Microcontroller is a digital circuit piece of equipment, thus it needs timer for its function. For this function, Microcontroller 8051 consists of an on-chip oscillator which toils as a time source for CPU (Central Processing Unit). As the productivity thumps of oscillator are steady as a result, it facilitates harmonized employment of all pieces of 8051 Microcontroller. Input/output Port: As we are acquainted with that Microcontroller is employed in embedded systems to manage the functions of devices. Thus to gather it to other machinery, gadgets or peripherals we need I/O (input/output) interfacing ports in Micro-controller. For this function Micro-controller 8051 consists of 4 input/output ports to untie it with other peripheral devices. Timers/Counters: Micro-controller 8051 is incorporated with two 16 bit counters & timers. The counters are separated into 8 bit registers. The timers are utilized for measuring the intervals, to find out pulse width etc. Explanation on 8051 Pin Diagram:

For explaining the pin diagram and pin configuration of microcontroller 8051, we are taking into deliberation a 40 pin Dual inline package (DIP). Pins 1 – 8:- recognized as Port 1. Different from other ports, this port doesn’t
provide any other purpose. Port 1 is a domestically pulled up, quasi bi directional Input/output port. Pin 9:- As made clear previously RESET pin is utilized to set the micro-controller 8051 to its primary values, whereas the micro-controller is functioning or at the early beginning of application. The RESET pin has to be set elevated for two machine rotations. Pins 10 – 17:- recognized as Port 3. This port also supplies a number of other functions such as timer input, interrupts, serial communication indicators TxD & RxD, control indicators for outside memory interfacing WR & RD, etc. This is a domestic pull up port with quasi bi directional port within. Pins 18 and 19:- These are employed for interfacing an outer crystal to give system clock.

Pin 20:- Titled as Vss – it symbolizes ground (0 V) association. Pins- 21-28:- recognized as Port 2 (P 2.0 – P 2.7) – other than serving as Input/output port, senior order address bus indicators are multiplexed with this quasi bi directional port. Pin- 29:- Program Store Enable or PSEN is employed to interpret sign from outer program memory. Pin-30:- External Access or EA input is employed to permit or prohibit outer memory interfacing. If there is no outer memory need, this pin is dragged high by linking it to Vcc. Pin-31:- Aka Address Latch Enable or ALE is brought into play to de-multiplex the address data indication of port 0 (for outer memory interfacing). Two ALE throbs are obtainable for every machine rotation. Pins 32-39: recognized as Port 0 (P0.0 to P0.7) – other than serving as Input/output port, low order data & address bus signals are multiplexed with this port (to provide the use of outer memory interfacing). This pin is a bi directional Input/output port (the single one in microcontroller 8051) and outer pull up resistors are necessary to utilize this port as Input/output. Pin-40: termed as Vcc is the chief power supply. By and large it is +5V DC. 8051 Microcontroller Applications:

The microcontroller 8051 has been in application in a large amount of machines, principally because it is simple to incorporate in a project or to assemble a machine around it. The following are the key spots of spotlight: 1. Energy Management: Competent measuring device systems aid in calculating energy consumption in domestic and industrialized applications. These meter systems are prepared competent by integrating microcontrollers. 2. Touch screens: A high degree of microcontroller suppliers integrate touch sensing abilities in their designs. Transportable devices such as media players, gaming devices & cell phones are some illustrations of micro-controller integrated with touch sensing screens. 3. Automobiles: The microcontroller 8051 discovers broad recognition in supplying automobile solutions. They are extensively utilized in hybrid motor vehicles to control engine variations. In addition, works such as cruise power and anti-brake mechanism has created it more capable with the amalgamation of micro-controllers. 4. Medical Devices: Handy medicinal gadgets such as glucose & blood pressure monitors bring into play micro-controllers, to put on view the measurements, as a result, offering higher dependability in giving correct medical results.

OBJECTIVE :- A system that allows user to remotely control home appliances using a GSM-based interface. Example : As the homeowner is somewhere out of home and he forgot to switch off the light ,then he can power off the light even from that place by sending a SMS. FLOW CHART :-

AT89C51 is an 8-bit microcontroller and belongs to Atmel’s 8051 family.ATMEL 89C51 has 4KB of Flash programmable and erasable read only memory. In 40 pin AT89C51, there are four ports designated as P1, P2, P3 and P0. All these ports are 8-bit bi-directional ports, i.e., they can be used as both input and output ports. Except P0 which needs external pull-ups, rest of the ports have internal pull-ups. When 1s are written to these port pins, they are pulled high by the internal pull-ups and can be used as inputs. These ports are also bit addressable and so their bits can also be accessed individually.


This GSM Modem can accept any GSM network operator SIM card and act just like a mobile phone with its own unique phone number. Advantage of using this modem will be that you can use its RS232 port to communicate and develop embedded applications. Applications like SMS Control, data transfer, remote control and logging can be developed easily.The modem can either be connected to PC serial port directly or to any microcontroller. It can be used to send and receive SMS or make/receive voice calls. It can also be used in GPRS mode to connect to internet and do many applications for data logging and control. In GPRS mode you can also connect to any remote FTP server and upload files for data logging.This GSM modem is a highly flexible plug and play quad band GSM modem for direct and easy integration to RS232 applications. Supports features like Voice, SMS, Data/Fax, GPRS and integrated TCP/IP stack.

Crystal oscillator:
A crystal oscillator is an electronic oscillator circuit that uses the mechanical resonance of a vibrating crystal of piezoelectric material to create an electrical signal with a very precise frequency. This frequency is commonly used to keep track of time , to provide a stable clock signal for digital integrated circuits, and to stabilize frequencies for radio transmitters and receivers. The most common type of piezoelectric resonator used is the quartz crystal, so oscillator circuits incorporating them became known as crystal oscillators. but other piezoelectric materials including polycrystalline ceramics are used in similar circuits. Quartz crystals are manufactured for frequencies from a few tens of kilohertz to tens of megahertz. More than two billion crystals are manufactured annually. Most are used for consumer devices such as wristwatches, clocks, radios, computers, and cellphones. Quartz crystals are also found inside test and measurement equipment, such as counters, signal generators, and oscilloscopes.

A capacitor is a passive two-terminal electrical component used to store energy electrostatically in an electric field. By contrast, batteries store energy via chemical reactions. The forms of practical capacitors vary widely, but all contain at least two electrical conductors separated by a dielectric (insulator); for example, one common construction consists of metal foils separated by a thin layer of insulating film. Capacitors are widely used as parts of electrical circuits in many common electrical devices.

A resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element.The current through a resistor is in direct proportion to the voltage across the resistor’s terminals. Resistors are common elements of electrical networks and electronic circuits and are ubiquitous in electronic equipment. Practical resistors can be made of various compounds and films, as well as resistance wire (wire made of a high-resistivity alloy, such as nickel-chrome). Resistors are also implemented within integrated circuits,
particularly analog devices, and can also be integrated into hybrid and printed circuits.

 IC 7408:
The 7408 is a 2 input AND gate. This takes two logic signals and outputs a true if and only if both inputs are true. There are four gates on this part. There are numerous voltage levels based on the technology used (the silicon, etc.) to produce the part.

ULN 2003 is a high voltage and high current Darlington array IC.It contains seven open collector darlington pairswith common emitters.A Darlinton pair is an arrangement of two bipolar transistors. These ICs are used driving a wide range of loads and are used as reley drivers,display drivers,line dvivers etc.

The LM324.OpAmp is based on the early µA741 design so it is not “rail to rail” input or output, nor does it have ultra low distortion, low input noise, high frequency capability or fast slew rate capability. It is economic, suited to medium quality audio processing and relatively benign in most application. .


In electronics, a diode is a two-terminal electronic component with asymmetric conductance, it has low (ideally zero) resistance to current flow in one direction, and high (ideally infinite) resistance in the other.

A transistor is a semiconductor device usedto amplify and switch electronic signals and electrical power. It is composed of semiconductor material with at least three terminals for connection to an external circuit. A voltage or current applied to one pair
of the transistor’s terminals changes the current through another pair of terminals. Because the controlled (output) power can be higher than the controlling (input) power, a transistor can amplify a signal. Today, some transistors are packaged individually, but many more are found embedded in integrated circuits.

A printed circuit board, or PCB, is used to mechanically support and electrically connect electronic components using conductive pathways, tracks or signal traces etched from copper sheets laminated onto a non-conductive substrate. When the board has only copper tracks and features, and no circuit elements such as capacitors, resistors or active devices have been manufactured into the actual substrate of the board, it is more correctly referred to as printed wiring board (PWB) or etched wiring board.

· Insert SIM card: Press the yellow pin to remove the tray from the SIM cardholder. After properly fixing the SIM card in the tray, insert the tray in the slot provided. · Connect Antenna: Screw the RF antenna if not already connected. · Connect RS232 Cable to PC/MCU: (Cable provided for RS232 communication). Default baud rate is 9600 with 8-N-1, no hardware handshaking. · Connect the power Supply (12V 1A) to the power input of board. Polarity should be Center +ve and outer –ve DC jack. · Network Led indicating various status of GSM module eg. Power on, network registration & GPRS connectivity. · After the Modem registers the network, led will blink in step of 3 seconds. At this stage you can start using Modem for your application. · AT commands can be sent to control GSM Modem.

To read a message the microcontroller sends the appropriate AT command to the Receiver GSM Modem through UART. The Modem then responds with the message and the microcontroller stores the message in the RAM,when the message ends there is no way to know by the microcontroller. The time-out generator circuit performs the vital function of providing the microcontroller board with the ability to detect the end of a message from the receiver GSM mobile. The output of the time-out generator circuit (connected to port1_3 of the microcontroller) is low until the message is being received and becomes high at the end of the message.

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