CHAPTER-1

INTRODUCTION TO WIRELESS DEVICE CONTROL

1.1 INTRODUCTION

Being able to achieve reliable long distance communication is an important open area of research. Today, everyone wants a comfortable lifestyle with everything controlled by just a press of some buttons. This project intends to make a device which can be used to control home Appliances by just pressing some buttons of a cell phone. It will use the existing infrastructure of cell phone networks for communication and device control. This will eliminate the need of a new infrastructure and detailed technical research. Currently, the primary mode for wireless communication uses RF (radio frequency). RF is an obvious choice for communication since it allows more information to be transferred at high speed and over long distance. However, creating RF network of long range for many simple applications is an impractical solution. Thus, by using existing RF Network of Cell Phones it minimizes the cost development and maintenance. It will help in conserving energy as with help of this device any appliance can be controlled from any distance. It also has application in Robotics and various other fields which require long distance communication. Here we designed a system which can be used to control Appliances (maximum of 8) from anywhere in the world just by pressing some buttons on a cell phone i.e. it is totally DTMF based.

1.2 HISTORY OF DTMF

Before DTMF was created, telephone networks used a dialling system called Decadic (also known as Pulse Dial). The Decadic system was used extensively in modern telephone networks to dial numbers, which were entered by the telephone companies users. The Decadic (Pulse Dialling) system used a series of clicks (which could be heard through the speaker of the phone) to dial the numbers which were dialled via a keypad or rotary dial. The clicking sounds were actually the connection of the phone line being connected, disconnected, and reconnected again in a certain pattern. The Decadic (Pulse Dialling) system was very useful, but was limited to the local exchange connections, requiring an operator to connect long distance calls. 1

In the late years of 1950, DTMF was being developed at Bell Labs for the purpose of allowing tone signals to dial long distance numbers, which could be potentially be dialled not only via standard wire networks, but also via radio links and or satellites. DTMF was being developed for the future of electronic telecommunications switching systems, as opposed to the mechanical crossbar systems, which were currently in use at the time. After DTMF was created, Decadic dialling was made pointless to continue, it made no sense to continue using that particular dialling system in the equipment circuits which the telephone exchanges were using at the time. Plans were then made to begin the manufacture of DTMF controlled switching systems in the communications exchanges and later standard customer owned telephones were upgraded to using DTMF circuits rather than Decadic (Pulse Dial). After various tests were performed on the DTMF system throughout the 1960s (when DTMF became known as Touch-Tone), DTMF was made official, and was then used as the main telecommunications dialling and switching system, and remains that way to this day.

1.3 MOTIVATION

³Save Electricity´, this statement motivated us in designing this system. It has been noticed several times that people are not use to in switching off the lights and fans when they are leaving their respective places. And later, they realize that they have forgotten to switch off the lights and fans. In order to deal with this problem we have designed a system from which one can operate the lights and fans of his home from a little cell-phone only i.e a DTMF based device is been introduced which will help in controlling the electric appliances of one¶s place. In this way, this system saves energy as well as brings comfort in life.

1.4 OBJECTIVE

The fundamental requirements for the cell phone based device control system remained fixed throughout the design process. The goal was to design a system which would allow the user automated and convenient access to their appliances through a telephone network. The fundamental objectives of the system include: y Correctly decode DTMF signals from the user2. Correctly decode caller identification information from the phone line. y Allow the user to automatically switch ON/OFF the devices.

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1.5 PROJECT OVERVIEW In this project the system, is controlled by a mobile phone that makes call to the mobile phone attached to the system in the course of the call, if any button is pressed control corresponding to the button pressed is heard at the other end of the call. This tone is called dual tone multi frequency tone (DTMF) microcontroller receives this DTMF tone with the help of phone stacked in the decoder. The received tone is processed by the microcontroller with the help of DTMF decoder CM8870 the decoder decodes the DTMF tone in to its equivalent binary digit and this binary number is send to the microcontroller, the microcontroller is programmed to take a decision for any give input and outputs its decision to relay drivers in order to energize or de-energize the relay for switching purpose. The mobile that makes a call to the mobile phone stacked on the system acts as a remote. So this simple project does not require the construction of receiver and transmitter units. DTMF signalling is used for telephone signalling over the line in the voice frequency band to the call switching centre. The version of DTMF used for telephone dialling is known as touch tone. DTMF assigns a specific frequency (consisting of two separate tones) to each keys that it can easily be identified by the electronic circuit. The signal generated by the DTMF encoder is the direct algebraic submission, in real time of the amplitudes of two sine (cosine) waves of different frequencies, i.e., pressing 5 will send a tone made by adding 1336 Hz and 770 Hz to the other end of the mobile. The important components of this system are DTMF decoder, Microcontroller and relay driver & relay. A CM8870 series DTMF decoder is used here. All types of the MT8870 series use digital counting techniques to detect and decode all the sixteen DTMF tone pairs in to a four bit code output. The built -in dial tone rejection circuit eliminated the need for pre- filtering. When the input signal given at pin (IN-) single ended input configuration is recognized to be effective, the correct four bit decode signal of the DTMF tone is transferred to outputs. The microcontroller used here is a common 8 bit Atmel microcontroller AT89S52.It is a low power, high-performance CMOS 8-bit microcontroller with 8K bytes of In-System Programmable (ISP) Flash program memory and 256 bytes of RAM,. It has 32 programmable input output lines .The resulting architecture is more code efficient. Outputs from port pins of the microcontroller are fed to inputs IN1 through IN4 to relay. Switch S1 is used for manual reset.

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CHAPTER-2 DTMF

2.1 DTMF BASICS

DTMF is a generic communication term for touch tone (a Registered Trademark of AT&T). The tones produced when dialling on the keypad on the phone could be used to represent the digits, and a separate tone is used for each digit. However, there is always a chance that a random sound will be on the same frequency which will trip up the system. It was suggested that if two tones were used to represent a digit, the likelihood of a false signal occurring is ruled out. This is the basis of using dual tone in DTMF communication. DTMF dialling uses a keypad with 12/16 buttons. Each key pressed on the phone generates two tones of specific frequencies, so a voice or a random signal cannot imitate the tones. One tone is generated from a high frequency group of tones and the other from low frequency group. The DTMF (Dual Tone Multiple Frequency) application is associated with digital telephony, and provides two selected output frequencies (one high band, one low band) for a duration of 100 ms. The matrix for selecting the high and low band frequencies associated with each key is shown in Figure 1 .

Figure2.1 DTMF keyboard matrix

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Each key is uniquely referenced by selecting one of the four low band frequencies associated with the matrix rows, coupled with selecting one of the four high band frequencies associated with the matrix columns. The low band frequencies are 697,770, 852, and 941 Hz, while the high band frequencies are 1209, 1336, 1477, and 1633 Hz. The frequencies generated on pressing different phone keys are shown in the Table 1.

Button Low Frequency(Hz) High Frequency(Hz) 1 697 1209 2 697 1336 3 697 1477 4 770 1209 5 770 1336 6 770 1477 7 852 1209 8 852 1336 9 852 1477 0 941 1209 * 941 1336 # 941 1477

Table 2.2 ± Frequencies generated on Key presses

Each row and column of the keypad corresponds to a certain tone and creates a specific frequency. Each button lies at the intersection of the two tones as shown in Table2.

1 2 3 697 4 5 6 770 7 8 9 852 * 0 # 941 1209 1336 1477 Frequency (Hz)

Table 2.3 ± Row and Column Frequency Correspondence

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When a button is pressed, both the row and column tones are generated by the telephone instrument. These two tones will be unique and different from tones of other keys. So, whenever we say that there is a low and high frequency associated with a button, it is actually the sum of two waves is transmitted. When you press a button in the telephone set keypad, a connection is made that generates a resultant signal of two tones at the same time. These two tones are taken from a row frequency and a column frequency. The resultant frequency signal is called "Dual Tone Multiple Frequency". These tones are identical and unique. A DTMF signal is the algebraic sum of two different audio frequencies, and can be expressed as follows: f(t) = A0sin(2*ɉ*fa*t) + B0sin(2*ɉ*fb*t) + ...... ------>(1)

Where fa and fb are two different audio frequencies with A and B as their peak amplitudes and f as the resultant DTMF signal. fa belongs to the low frequency group and fb belongs to the high frequency group. Each of the low and high frequency groups comprise four frequencies from the various keys present on the telephone keypad; two different frequencies, one from the high frequency group and another from the low frequency group are used to produce a DTMF signal to represent the pressed key. The amplitudes of the two sine waves should be such that

(0.7 < (A/B) < 0.9)V ------>(2)

The frequencies are chosen such that they are not the harmonics of each other. When you send these DTMF signals to the telephone exchange through cables, the servers in the telephone exchange identifies these signals and makes the connection to the person you are calling.

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CHAPTER-3 DTMF-Decoder

3.1 DTMF DECODER IC 8870. 3.1.1 Description The M-8870 is a full DTMF Receiver that integrates both band split filter and decoder functions into a single 18-pin DIP or SOIC package. Manufactured using CMOS process technology, the M-8870 offers low power consumption (35 mW max) and precise data handling. Its filter section uses switched capacitor technology for both the high and low group filters and for dial tone rejection. Its decoder uses digital counting techniques to detect and decode all 16 DTMF tone pairs into a 4-bit code. External component count is minimized by provision of an on-chip differential input amplifier, clock generator, and latched tri-state interface bus. Minimal external components required include a low-cost 3.579545MHz color burst crystal, a timing resistor, and a timing capacitor. The M-8870-02 provides a ³power- down´ option which, when enabled, drops consumption to less than 0.5mW.

3.1.2 Features

‡ Low Power Consumption ‡ Adjustable Acquisition and Release Times ‡ Central Office Quality and Performance ‡ Power-down and Inhibit Modes (-02 only) ‡ Inexpensive 3.58 MHz Time Base ‡ Single 5 Volt Power Supply ‡ Dial Tone Suppression

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3.1.3 Pin Description of 8870

Figure 3.1 Pin diagram of 8870 IC

Figure 3.2 pin description of 8870

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Figure 3.3 Logic table of 8870

3.1.4 Applications ‡ Telephone switch equipment ‡ Remote data entry ‡ Paging systems ‡ Personal computers ‡ Credit card systems

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CHAPTER 4 MICROCONTROLLER(AT89S52)

4.1 AT89S52 MICROCONTROLLER

Microcontroller is a microprocessor designed specifically for control applications, and is equipped with ROM, RAM and facilities I / O on a single chip. AT89S52 is one of the family MCS-51/52 equipped with an internal 8 Kbyte Flash EPROM (Erasable and Programmable Read Only Memory), which allows memory to be reprogrammed. Designed by Atmel AT89S52 in accordance with standard instructions and pin layout 80C5.

4.1.1 AT89S52 MICROCONTROLLER FEATURES:

‡ A CPU (Central Processing Unit) 8 Bit.

‡ 256 bytes of RAM (Random Access Memory) internally.

‡ Four-port I / O, which each consist of eight bits

‡ The internal oscillator and timing circuits.

‡ Two timer / counters 16 bits

‡ Five interrupt lines (two fruits and three external interrupt internal interruptions).

‡ A serial port with full duplex UART (Universal Asynchronous Receiver Transmitter).

‡ Able to conduct the process of multiplication, division, and Boolean.

‡ The size of 8 Kbyte EPROM for program memory.

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‡ Maximum speed execution of instructions per cycle is 0.5 at 24 MHz clock frequency. If the microcontroller clock frequency used is 12 MHz, the speed is 1 instruction execution

CPU (Central Processing Unit)

This section serves to control the entire operation on the microcontroller. This unit is divided into two parts, the control unit, or CU (Control Unit) and the arithmetic and logic unit or ALU (Arithmetic Logic Unit) The main function control unit is to take instructions from memory (fetch) and then translate the composition of these instructions into a simple collection of work processes (decode), and implement instruction sequence in accordance with the steps that have been determined the program (execute). Arithmetic and logic unit is the part that deals with arithmetic operations like addition, subtraction, and logical data manipulation operations such as AND, OR, and comparison.

Part Input / Output (I / O)

This section serves as a communication tool with a single chip device outside the system. Consistent with the name, I / O devices can receive and provide data to / from a single chip.There are two kinds of devices I / O is used, ie devices for serial connection UART (Universal Asynchronous Receiver Transmitter) and device for so-called parallel relationship with the PIO (Parallel Input Output). Both types of I / O has been available in a single chip AT89S52.

Software

Single flakes MCS-51 family has a special programming language that is not understood by other types of single flakes. This programming language known by the name of the assembler language instruction has 256 devices. However, when this can be done with microcontroller programming using C language. With the C language, microcontroller programming easier, because the C language format will be automatically converted into assembler language with a hex file format. Software on a microcontroller can be divided into five groups as follows:

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1. Data Transfer Instructions

This instruction serves to move the data, between registers, from memory to memory, from registers to memory, and others.

2. Arithmetic Instruction

These instructions perform arithmetic operations including addition, subtraction, addition of one (increments), a reduction of one (decrement), multiplication and division.

3. Logic and Bit Manipulation Instructions

Functions perform logic operations AND, OR, XOR, comparison, shift and complement data.

4. Branching instructions

Serves to alter the normal sequence of execution of a program. With this instruction, the programs that are implemented will jump to a particular address.

5. Instruction Stack, I / O and Control

These instructions set the stack usage, read / write I / O ports, and controlling.

Pin Configuration

AT89S52 microcontroller has 40 pins with a single 5 Volt power supply. The pin 40 is illustrated as follows:

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Figure 4.1 Pin description of Microcontroller AT89S52

The function of each pin AT89S52 is:

1. Pin 1 to 8 (Port 1) is an 8-bit parallel port of a two-way (bidirectional) that can be used for different purposes (general purpose).

2. Pin 9 is a pin reset, reset is active if a high ration.

3. Pin 10 to 17 (Port 3) is 8-bit parallel port which has a two-way alternate function as follows:

‡ P3.0 (10): RXD (serial port data receiver)

‡ P3.1 (11): TXD (serial port data sender)

‡ P3.2 (12): INT0 (external interrupt 0 input, active low)

‡ P3.3 (13): INT1 (external an interrupt input, active low)

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‡ P3.4 (14): T0 (external input timer / counter 0)

‡ P3.5 (15): T1 (external input timer / counter 1)

‡ P3.6 (16): WR (Write, active low) control signal from port 0 write data to memory and input-output data externally.

‡ P3.7 (17): RD (Read, active low) control signal of the reading of input-output data memory external to the port 0.

4. XTAL pin 18 as the second, the output is connected to the crystal oscillator.

5. XTAL pin 19 as the first, high berpenguatan input to the oscillator, connected to the crystal.

6. Pin 20 as Vss, is connected to 0 or ground on the circuit.

7. Pin 21 to 28 (Port 2) is 8 bits parallel ports in both directions. This port sends the address byte when accessing external memory is carried on.

8. Pin 29 as the PSEN (Program Store Enable) is the signal used for reading, move the program the external memory (ROM / EPROM) to microcontroller (active low).

9. Pin 30 as the ALE (Address Latch Enable) to hold down the address for accessing external memory. This pin also functions as a prog (active low) that is activated when the internal program flash memory on the microcontroller (on chip).

10. Pin 31 as the EA (External Accesss) to select the memory to be used, the internal program memory (EA = Fcc) or external program memory (EA = Vss), also serves as Vpp (programming supply voltage) when programming the internal flash memory on the microcontroller.

11. Pin 32 to 39 (Port 0) is an 8-bit parallel port in both directions. Under which functions as a multiplexed address data to access an external program and data memory.

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12. Pin 40 as Fcc, connected to +5 V as a ration to the microcontroller.

Memory Organization

All single chip in the family division of MCS-51 has the address space to programs and data. The separation of program memory and data memory allows data to be accessed by a memory address 8 bits. Even so, the address memory 16 bits of data can be generated through the DPTR register (Point Data Register). Program memory can only be read can not be written because it is stored in the EPROM. In this case the EPROM is available in a single chip AT89S52 for 8 Kbyte

Memory Program

In EPROM 8 Kbytes, if the EA (External Access) high-value, then the program will occupy the address 0000 H to H 0FFF internally. If EA¶s low value, the program will occupy the address 1000 H to FFFF H to external programs.

Data memory

Internal data memory are mapped as shown below memory space is divided into three blocks of the 128 down, 128 up, and space SFR (Special Function Register)

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Under Section 128 bytes of RAM mapped into the 32 bytes are grouped into four banks and eight registers (R0 to R7).In the next 16 bytes, on the banks of register, form a block of memory space that can teralamati per bit (bit addressable).These addresses are 00 bits up to 7FHH. All the bytes that are within 128 can be accessed either directly or indirectly. Section 128 above can only be accessed by indirect addressing. Section 128 of the RAM is solely in the devices have 256 bytes of RAM.

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CHAPTER 5 RELAY(SPDT)

5.1 INTRODUCTION

A relay is an electrically operated switch. Many relays use an electromagnet to operate a switching mechanism mechanically, but other operating principles are also used. Relays are used where it is necessary to control a circuit by a low-power signal (with complete electrical isolation between control and controlled circuits), or where several circuits must be controlled by one signal. The first relays were used in long distance telegraph circuits, repeating the signal coming in from one circuit and re-transmitting it to another. Relays were used extensively in telephone exchanges and early computers to perform logical operations.

A type of relay that can handle the high power required to directly drive an electric motor is called a contactor. Solid-state relays control power circuits with no moving parts, instead using a semiconductor device to perform switching. Relays with calibrated operating characteristics and sometimes multiple operating coils are used to protect electrical circuits from overload or faults; in modern electric power systems these functions are performed by digital instruments still called "protective relays".

5.2 BASIC DESIGN AND OPERATION

A simple electromagnetic relay consists of a coil of wire surrounding a soft iron core, an iron yoke which provides a low reluctance path for magnetic flux, a movable iron armature, and one or more sets of contacts (there are two in the relay pictured). The armature is hinged to the yoke and mechanically linked to one or more sets of moving contacts. It is held in place by a spring so that when the relay is de-energized there is an air gap in the magnetic circuit. In this condition, one of the two sets of contacts in the relay pictured is closed, and the other set is open. Other relays may have more or fewer sets of contacts depending on their function. The relay in the picture also has a wire connecting the armature to the yoke. This ensures continuity of the circuit between the moving contacts on the armature, and the circuit track on the printed circuit board (PCB) via the yoke, which is soldered to the PCB.

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When an electric current is passed through the coil it generates a magnetic field that attracts the armature, and the consequent movement of the movable contact(s) either makes or breaks (depending upon construction) a connection with a fixed contact. If the set of contacts was closed when the relay was de-energized, then the movement opens the contacts and breaks the connection, and vice versa if the contacts were open. When the current to the coil is switched off, the armature is returned by a force, approximately half as strong as the magnetic force, to its relaxed position. Usually this force is provided by a spring, but gravity is also used commonly in industrial motor starters. Most relays are manufactured to operate quickly. In a low-voltage application this reduces noise; in a high voltage or current application it reduces arcing.

When the coil is energized with direct current, a diode is often placed across the coil to dissipate the energy from the collapsing magnetic field at deactivation, which would otherwise generate a voltage spike dangerous to semiconductor circuit components. Some automotive relays include a diode inside the relay case. Alternatively, a contact protection network consisting of a capacitor and resistor in series (snubber circuit) may absorb the surge. If the coil is designed to be energized with alternating current (AC), a small copper "shading ring" can be crimped to the end of the solenoid, creating a small out-of-phase current which increases the minimum pull on the armature during the AC cycle.

A solid-state relay uses a thyristor or other solid-state switching device, activated by the control signal, to switch the controlled load, instead of a solenoid. An optocoupler (a light- emitting diode (LED) coupled with a photo transistor) can be used to isolate control and controlled circuits.

5.3 Single pole, double throw (SPDT)

This relay is similar to a SPST, but pin 30 is switched to either output pin 87A or pin 87. Pin 87A is connected in the unpowered state.

Here is a schematic showing uses for some SPDT relays.

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Figure 5.1 Basic relay circuit

5.4 Why use a relay?

Here are a couple different circuits that perform the same function...turning on a pair of driving lights. Let's compare the two circuits.

Circuit 1 - A simple circuit with a switch and lights. Some concerns:

- The high current going to the lights will pass through the switch. Unless you buy a very heavy duty switch the switch will eventually fail. - There will be noticeable (measurable) voltage loss by the time the circuit reaches the lights. - When hooking up a circuit like this most people will simply tap into the fuse panel or a wire under the dash. This will usually overload the factory circuit. It might blow a fuse or melt wire, but more likely will degrade the wire and cause intermittant failures of whatever the circuit is hooked to.

Circuit 2 - A proper circuit with a relay and fuse.

- The switch is only switching the relay. It draws a very small current which is good for the switch and whatever power source has been used. - There will be little or no voltage loss using a relay. A light burns brighter and lasts longer

19 when supplied with proper voltage. - All the high current is kept between the battery and lights and is properly protected by a fuse. Building a circuit properly takes more components and time, but will work better, last longer, and be safer.

5.5 POWER SUPPLY CIRCUIT

This circuit is a small +5V power supply, which is useful when experimenting with digital electronics. Small inexpensive wall tranformers with variable output voltage are available from any electronics shop and supermarket. Those transformers are easily available, but usually their voltage regulation is very poor, which makes then not very usable for digital circuit experimenter unless a better regulation can be achieved in some way. The following circuit is the answer to the problem.

This circuit can give +5V output at about 150 mA current, but it can be increased to 1 A when good cooling is added to 7805 regulator chip. The circuit has over overload and therminal protection. The capacitors must have enough rating to safely handle the input voltage feed to circuit. The circuit is very easy to build for example into a piece of veroboard.

Fig 5.2 Pinout of the 7805 regulator IC.

1. Unregulated voltage in

2. Ground

3. Regulated voltage out

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Figure 5.3 Simple 5 volt power supply

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CHAPTER 6 WORKING

In this system, there is a control unit/module. The control unit is able to connect to the cellular network automatically, to receive DTMF and will be able to decode for password identification and instructions to be sent to the microcontroller. The microcontroller within the control unit will issue the command to the electrical appliances through a simple control circuit. while the input from the mobile using a headphone is connected b/w the 0.1uf capacitor and the ground, DTMF tones can be transferred to the decoder ic (8870) and once the ic is powered up the o/p can be seen by connecting bulbs at relay 1,2,3 and 4. To operate some devices remotely as the Mobile phone connected can be called from anywhere in the world and by pressing the keys the DTMF tones can be transmitted to the receiving end mobile and hence any device connected can be operated globally.

In order to operate the system you have to make a call to the cell phone attached to the main circuitry of the project from any other phone. The phone is picked at the receiving end through auto answer mode (which is in the phone, just enable it). Each number on the cell phone keypad has a distinct sound (called DTMF tones). This sound is used to identify the key pressed, using a CM8870 DTMF decoder. Here the sound is firstly preamplified by the microphone unit. This sound is now fed into the M8870 IC which decodes them in form of numbers. These decoded numbers are fed into the microcontroller .It checks the code and energize/de-energize that particular relay for which that signal is send ,in response of which the switching takes place in the appliance which is connected to it. Like:

Figure 6.1 Block diagram of the system using DTMF.

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CHAPTER-7 APPLICATIONS

Since a cell phone based home appliance control system has overcome the limitations of the range of a normal RF controlled systems (or a manual switch on/off system), it has endless applications. It can be used by any layman due to its simplistic nature. Also any commonly available cell phone be used to control this system. These features extend the scope of this system to a large number of diversified fields. Some of the common applications have been listed below: y This system of operating devices can be used to control all the appliances at the home even when you are far away from the home. This increases your control over the house and makes your home more secured and make these devices more users friendly. For e.g.- y You can turn off the TV yourself when you don¶t want that small children at your home to watch it (in your absence). y You can open the garage door only to allow some authorized person to take your vehicles out of our house. y You can automatically open the main door of your house when some of your workers/relatives come home unexpectedly when you are away at your office. y You can turn your Air Conditioner on when you are about to come back to your home to find your room already cooled to the desired temperature.

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CONCLUSION AND FUTURE SCOPE

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REFERENCES

1. ³DTMF Based Remote Control System´- R. Sharma, K. Kumar, and S. Viq, IEEE International Conference ICIT , pp. 2380-2383, December 2006. 2. ³Integrated DTMF Receiver´-M.Callahan Jr, IEEE Transactions on communications, vol. 27, pp. 343-348, February 1979. 3. ³A phone based Remote Controller for Home´- I. Coskun and H. Ardam IEEE Trans. Consumer , vol.44,no. 4,pp. 1291-1297,November 1998 4. SPDT relay- ³Mason, C. R., Art & Science of Protective Relaying´, Chapter 2, GE Consumer & Electrical. 5. ³Microcontroller Technology:16F84A´, prentice hall , 7th edition, page32, 2002.

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