SEMINAR REPORT

ON

GSM BASED HOME AUTOMATION SYSTEM

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NATIONAL INSTITUTE OF TECHNOLOGY

SRINAGAR

NAME : RAJNEESH KUMAR SALGOTRA

ENROL : 163/2010

ROLL : 31

SEMESTER : 7th

TABLE OF CONTENT

1) INTRODUCTION2) BLOCK DIAGRAM3) DOUBLE-TONE MULTIFREQUENCY4) MICROCONTROLLER5) RELAYS6) CONCLUSION7) REFERENCE

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INTRODUCTION

GSM (Global System for Mobile Communications): It is a cellular communication standard.

Using GSM networks, this can monitor and control appliances and other devices locally using built-in input and output peripherals. Remotely the system allows the user to effectively monitor and control the house/office appliances and equipment via the mobile phone set by sending commands in the form of DTMF TONE. The main concept behind the project is receiving the CALL and a fixDTMF TONE and processing it further as required to performseveral operations. The type of the operation to be performed depends on the key pressed. The principle in which the project is based is fairly simple. Firstly, the

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DTMF TONE is sent via the mobile keypad and then it is decoded through a decoder and sent to the intermediate hardware that we have designed according to the command received in form of the DTMF TONE.

The DTMF TONE is sent from the mobile set that contains commands in DTMF form which are then processed accordinglyto perform the required task

WHY GSM ?

Because GSM is the one of the most used communication networks today . Almost every person has a mobile station these days , which are used as terminals for the voice calls , they can also be used for many other applications . Now , If we use it for controlling distant home appliances it will be very beneficiary because of tworeasons:

1.The wireless remote controls for appliances are expensive and also it is also difficult for any individual to carry many remote controllers .

2.Now, If we use only the single mobile for communicating with many devices and voice calls also .The User has to carry a single Mobile .

3.Mobile Stations are incorporated with many functions so why not to add few more .

BLOCK DIAGRAM

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POWER SUPPLY

AC POWER

Mobile

Connector

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POWER SUPPLY

SOLID –STATE

RELAY

SOLID-STATE

RELAY

L

O

A

D

L

O

A

D

AC POWER

DTMFThe DTMF (Dual Tone Multiple Frequency) application is associated with digital telephony, and provides two selected output frequencies (one high band, one low band).The matrix for selecting the high and low band frequenciesassociated with each key. 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 and 1477 Hz. The DTMF subroutine assumes that the keydecoding is supplied as a low order hex digit in the accumulator.

If we press 1

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The corresponding signal produced

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DTMF DECODERDTMF decoder is a very easy to use Integrated Circuit to decode DTMF dial tones found on telephone lines with touchtone phones.

The frequencies used for the DTMF (dual-tone, multi-frequency) system, which is also referred to as tone dialling are 697, 770, 852, and 941 Hz at low pass filter and1209, 1336 , 1477 Hz at high pass filter . These frequency signals are encoded as a pair of sinusoidal (sine wave) tones from the table below which are mixed with each other. So, we need to decode it for knowing which digit was pressed at the Encoder .DTMF is used by most PSTN (public switched telephone networks) systems for

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number dialling, and is also used for voice-response systems such as telephone banking and sometimes over private radio networks to provide signalling and transferring of small amounts of data.

A Decoder need to have many units like High pass filters for Higher frequencies correspondingly Low pass Filters , and most of the IC have Zero crossing Detector circuit forCouting the frequency and many other Units . The unit willnot detect numbers dialled using pulse dialling. Circuit uses a CM8870 DTMF receiver chip and pre-programmed microcontroller.

I am using MT8870

MT8870

The MT8870D/MT8870D-1 is a complete DTMF receiver integrating both the bandsplit filter and digital decoder functions. The filter section uses switched capacitor techniques for high and low group filters; the decoder uses digital counting techniques to detect and decode all 16 DTMF tonepairs into a 4-bit code .And the Latch is usedto hold the output for some time . External component count is minimized by on chip provision of a differential input amplifier, clock oscillator and latched three-state bus interface.

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The PIN Diagram of MT8870

The Block Diagram of the MT8870

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The Outputs Generated at Q1 , Q2 , Q3 and Q4

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8051 MICROCONTROLLERAn embedded microcontroller is a chip, which has a computer processor with all its support function (clockingand reset), memory (both program storage and RAM), and I/O(including bus interfaces) built into the device. These built in function minimize the need for external circuits and devices to the designed in the final applications. Theimprovements in micro-controller technology has meant thatit is often more cost effective, faster and more efficientto develop an application using a micro-controller .

There are two types of micro-controller commonly in use. Embedded micro-controller is the micro-controller, which has the entire hardware requirement to run the application, provided on the chip. External memory micro-controller is the micro-controller that allows the connection of external memory when the program memory is insufficient for an application or during the work a separate ROM (or even RAM) will make the work easier.

FEATURES OF 8051

128 bytes of RAM 16 bit address bus 4 Parallel Ports 1 Serial port 4K ROM 6 Interrupts Sources less power consumption 16-bit program counter and data pointer 32 general purpose registers each of 8 bits

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ROM on 8051 is 4 Kbytes in size 2 Timers

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Pin Description

VCC Supply voltage.

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GND Ground.

Port 0 Port 0 is an 8-bit open drain bidirectional I/O port. 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. External pull-ups are required .

Port 1 Port 1 is an 8-bit bidirectional I/O port with internal pull-ups. When 1s are written to Port 1 pins, they are pulled high by the internal pull-ups and can be used as inputs. Port 1 also receives the low-order addressbytes during Flash programming and verification.

Port 2 Port 2 is an 8-bit bidirectional I/O port with internal pull-ups. When 1s are written to Port 2 pins, they are pulled high by the internal pull-ups and can be used as inputs. Port 2 emits the high-order address byte during fetches from external program memory and during accesses to external data memory that use 16-bit address .

Port 3 Port 3 is an 8-bit bidirectional I/O port with internal pull-ups. When 1s are written to Port 3 pins, they are pulled high by the internal pull-ups and can be used as inputs. Port 3 also serves the functions of various special features of the AT89S51, as shown in the Figure above . Hence , Seldom used as I/O PORT

XTAL1 Input to the inverting oscillator amplifier and input to the internal clock operating circuit.

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XTAL2 Output from the inverting oscillator amplifier

RELAYS A relay is an electrically operated switch. Relays are used where it is necessary to control a circuit by a low-power signal with complete electrical isolation between control and controlled circuit .

SOLID STATE RELAYS

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RELAY

LOW POWERInput

HIGH POWER CIRCUIT

A solid-state relay is an ON-OFF control device in which the load current is conducted by one or more semiconductors - e.g., a power transistor, an SCR, or a TRIAC. (The SCR and TRIAC are often called “thyristors,” aterm derived by combining thyratron and transistor, since thyristors are triggered semiconductorswitches.)

Like all relays, the SSR requires relatively low controlcircuit energy to switch the output state from OFF to ON, or vice versa. Since this control energy is very much lower than the output power controllable by the relayat full load, "power gain" in an SSR is substantial--frequently much higher than in an electromagnetic relay ofcomparable output rating. To put it another way, the sensitivity of an SSR is often significantly higher than that of an EMR of comparable output rating.

Photo-coupled SSR's (see figure 3), in which the control signal is applied to a light or infrared source (usually, a light-emitting diode, or LED), and the radiation from that source is detected in a photosensitive semi-conductor(i.e., a photosensitive diode, a photo-sensitive transistor, or a photo-sensitive thyristor). The output ofthe photo-sensitive device is then used to trigger (gate) the TRIAC or the SCR's that switch the load current. Clearly, the only significant “coupling path” between input and output is the beam of light or infrared radiation, and electrical isolation is excellent. These SSR's are also referred to as “optically coupled” or “photo-isolated”.

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CONCULSION

The extensive capabilities of this system are what make itso interesting. From the convenience of a simple cell

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AC

phone, a user is able to control any electrical devices,wherever is the range of GSM which has almost covered thewhole globe . This makes it possible for users to rest assured that their belongings are secure and that the television and other electrical appliances was not left running when they left the house to just list a few of themany uses of this system. The end product will have a simplistic design making it easy for users to interact with .

The major drawback in this system is no feedbackis available , so it may happen that you have Pressed a key for an action but You will noy receive any acknowledgement whether it has happened or Not .

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REFERENCES 1)

http://pdf1.alldatasheet.com/datasheet-pdf/view/77085/MITEL/MT8870.html

2)Mazidi, Muhammad Ali, The 8051 Microcontroller and Embedded Systems

3)SOLID STATE RELAY HAND BOOK4)http://chipscity.com/downloads/Projects/GSM%20based

%20Control%20System.pdf5)www.wikipedia.com 6)8051 MICROCONTROLLERS by SATISH SHAH 7)http://www.informit.com/library/content.aspx?

b=Signaling_System_No_7&seqNum=11

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