CONTENTS

1. INTRODUCTION

2. BLOCK DIAGRAM

3. WORKING PRINCIPLE

4. COMPONENTS REQUIRED

5. PROGRAM

6. PROCEDURE TO INSTALL KIEL SOFT WARE

7. ESTIMATED COST OF PROJECT

8. ADVANTAGES

9. DISADVANTAGES

10. APPLICATIONS

11. CONCLUSION

12. BIBLOGRAPHY

1.INTRODUCTION:

A transformer is a device which transfers electrical energy from one circuit to another through inductively coupled conductors—the transformer's coils. A varying current in the first or primary winding creates a varying magnetic flux in the transformer's core and thus a varying magnetic field through the secondary winding. This varying magnetic field induces a varying electromotive force (EMF) or "voltage" in the secondary winding. This effect is called mutual induction.

If a load is connected to the secondary, an electric current will flow in the secondary winding and electrical energy will be transferred from the primary circuit through the transformer to the load. In an ideal transformer, the induced voltage in the secondary winding (Vs) is in proportion to the primary voltage (Vp), and is given by the ratio of the number of turns in the secondary (Ns) to the number of turns in the primary (Np) as follows:

\FRAC{V_\TEXT{S}}{V_{\TEXT{P}}} = \FRAC{N_\TEXT{S}}{N_\TEXT{P}}

By appropriate selection of the ratio of turns, a transformer thus allows an alternating current (AC) voltage to be "stepped up" by making Ns greater than Np, or "stepped down" by making Ns less than Np.

Our project consists of the LCD-enabled applications where line engineer is alerted

on LCD when transformer shuts down. Each transformer is equipped with

microcontroller interfaced to central LCD control system. When any relay of

transformer is triggered, error message is shown on LCD display

2.BLOCK DIAGRAM:

3.WORKING PRINCIPLE:

All fault alert relays inside transformer are interfaced to microcontroller which in turn

is interfaced to GSM modem. When there is fault in transformer, relays inside

transformer are triggered, Microcontroller detects the triggered relay and SMS is

sent with fault description to line engineer.

4.COMPONENTS REQUIRED

HARDWARE REQUIRMENTS:

1. GSM modem.

2. 89c051 microcontroller.

3. 8051 PCB.

4. Interfacing buses (interfacing wires).

5. Ferric chloride (FeCl3) to make PCB.

6. Power Supply components.

7. IC programmer.

8. Relay

9. Windows PC.

SOFTWARE REQUIRMENTS:

1. Keil software.

2. Eagle software for PCB design

3. Flash magic to program microcontroller.

5.PROGRAM

#include <reg51.h>#include "main"#include "delay.c"#include "lcd.c"#include "i2c.c"#include "gsm.c"#include "ps2.c"

void main(void){ unsigned char k,error_message[10]; initApplication (); while(1){ decodePs2KeyboardData(); if(relay1==0||relay2==0||relay3==0||relay4==0||relay5==0||relay6==0||relay7==0||relay8==0){

if(relay1==0){ view_address=0; }else if(relay2==0){ view_address=1; }else if(relay3==0){ view_address=2; }else if(relay4==0){

view_address=3; }else if(relay5==0){ view_address=4; }else if(relay6==0){ view_address=5; }else if(relay7==0){ view_address=6; }else if(relay8==0){ view_address=7; }

IE=0x00;

recv_data_from_i2c(view_address*FILE_SIZE+RELAY_MESSAGE_ADDRESS,FILE_SIZE);

strncpy(error_message,rtc_recv_val,10); recv_data_from_i2c(PHONE_NUMBER_COUNTER,1); view_address=rtc_recv_val[0]; for(k=0;k<view_address;k++){ sending_sms=1;

recv_data_from_i2c(k*FILE_SIZE+PHONE_NUMBER_ADDRESS,FILE_SIZE);

strcpy(command,SEND_MESSAGE_AT_CMD); strncat(command,rtc_recv_val,10); strcat(command,"\"\r"); strncat(command,error_message,10); sendGsmCommand(command); SBUF=26; } lcd_clear(); lcd_string("SMS SENT"); del_5s(); IE=INTERRUPT;}

}}

void initApplication(){ TMOD=0x20; TH1=0xFD; TR1=1; SCON=0x50; TL1 = 0XFD; RI=0; IE=INTERRUPT; TCON=0xFF; lcd_init(); lcd_clear();

lcd_string("INITIALIZING GSM MODEM WAIT..."); ps2Keyboard_init(); sendGsmCommand(STOP_ECHO); sendGsmCommand(RECIEVE_MESSAGE_AT_CMD); lcd_clear(); lcd_string("TRANSFORMER FAULT ALERT SMS"); is_phone_number=0; is_tab=0; relay1=1; relay2=1; relay3=1; relay4=1; relay5=1; relay6=1; relay7=1; relay8=1;}

#include<string.h>#include "ps2.h"

void ps2Keyboard_init(){ data_packet=0; display_counter=0; data_counter=0; buffer_counter=0; name_buffer_length=0; packet_count_to_recieve=55; KEYBOARD_CLK=1; KEYBOARD_DATA=1;}

void decodePs2KeyboardData(){unsigned char k;

if(buffer_counter>display_counter){ if(buffer[display_counter]!=0xE0) { packet_count_to_recieve=33;

switch(buffer[display_counter]) {

case 0x66://lcd_string("BACK SPACE");if(name_buffer_length!=0){

name_buffer_length--; lcd_cmd(0x80+name_buffer_length);

lcd_data(' '); lcd_cmd(0x80+name_buffer_length);

}break;case 0x0D:

//lcd_string("TAB");lcd_clear();if(is_tab==0 ||view_address==0){ is_tab=1;

recv_data_from_i2c(PHONE_NUMBER_COUNTER,1); view_address=rtc_recv_val[0];

if(view_address==0){ lcd_string("NO PHONE NUMBERS

EXIST"); break;

}}recv_data_from_i2c((view_address-

1)*FILE_SIZE+PHONE_NUMBER_ADDRESS,FILE_SIZE);for(k=0;k<10;k++){

lcd_data(rtc_recv_val[k]); }

view_address--;break;case 0x58:

//lcd_string("CAPS");lcd_clear();if(is_tab==1 ||view_address==0){ is_tab=0; view_address =0;}

recv_data_from_i2c(view_address*FILE_SIZE+RELAY_MESSAGE_ADDRESS,FILE_SIZE);

switch(view_address) {

case 0: lcd_string(" RELAY 1 "); break; case 1: lcd_string(" RELAY 2 "); Break; case 2: lcd_string(" RELAY 3 "); break; case 3: lcd_string(" RELAY 4 "); break; case 4: lcd_string(" RELAY 5 "); break; case 5: lcd_string(" RELAY 6 "); break; case 6: lcd_string(" RELAY 7 "); break; case 7: lcd_string(" RELAY 8 "); break; case 8: lcd_string(" RELAY 9 "); break; case 9: lcd_string(" RELAY 10 "); break; case 10: lcd_string(" RELAY 11 "); break; case 11:

lcd_string(" RELAY 12 "); break; case 12: lcd_string(" RELAY 13 "); break; case 13: lcd_string(" RELAY 14 "); break; case 14: lcd_string(" RELAY 15 "); break; case 15: lcd_string(" RELAY 16 "); break;}lcd_nextline();

if(rtc_recv_val[0]==0){ lcd_string("NO ERROR MESSAGE");}else{ for(k=0;k<10;k++){ lcd_data(rtc_recv_val[k]);

}}view_address++;if(view_address>15){ view_address=0;}

break;case 0x76:

//lcd_string("ESC");initApplication();

break;case 0x05:

//lcd_string("F1");lcd_clear();lcd_string("PLEASE ENTER PHONE NUMBER");name_buffer_length=0;keybaord_data_length=10;is_phone_number=1;

break;

case 0x06://lcd_string("F2");view_address--;lcd_clear();lcd_string("ENTER MESSAGE FOR RELAY ");lcd_display_bcd(view_address+1);name_buffer_length=0;keybaord_data_length=10;is_phone_number=0;resetBuffer();

break;case 0x04

7.Keil uVision v 8.12 - C51 version - How to install

-----------------------------------------------------1) Install Keil software with c51v812.exe a) Press Next b) Accept the license -> Next c) Destination folder: C:\Keil -> Next d) Fill the form with any name -> Next e) Wait the installation f) Finish

2) Copy the file l51.dll to the folder C:\Keil\C51\BIN Overwrite the existing l51.dll file

3) Execute uVision 3 from the Start Menu Or the Desktop Go to File -> License Management... Copy the Computer ID field (CID)

6) Execute the license generator licgen-v32.exe

7) In the MCU type, choose 51 In the right list, choose Prof. Developers Kit In the bellow list, choose With computer ID code Select the V2 item Select External CID code Paste the previously copied CID Press Generate Copy the generated LIC0= field Ignore the SN= field

8) Go to the License Management of uVision Paste the license generated with the licgen in the New License ID Code (LIC) field Press Add Lic Press Close9) Exit from uVision

10) Exit from license generator11) Enjoy!

Micro controller AT89S52

The AT89C52 is a low-power, high-performance CMOS 8-bit

microcomputer with 8K bytes of Flash programmable and erasable read only

memory (PEROM). The on-chip Flash allows the program memory to be

reprogrammed in-system or by a Conventional nonvolatile memory

programmer.

FIGURE:PIN DISCRIPTION OF IC 89S52

Features: Compatible with MCS-51™ Products

8K Bytes of In-System Reprogrammable Flash Memory

Endurance: 1,000 Write/Erase Cycles

Fully Static Operation: 0 Hz to 24 MHz

Three-level Program Memory Lock

256 x 8-bit Internal RAM

32 Programmable I/O Lines

Three 16-bit Timer/Counters

Eight Interrupt Sources

Full Duplex Serial port.

On chip oscillator and clock circuitry.

Low-power Idle and Power-down Modes.

Pin Description:

VCC - Supply voltage.

GND - Ground.

Port 0 - Port 0 is an 8-bit open drain bi-directional I/O port

pin 32 to 39

Port 1 - Port 1 is an 8-bit bi-directional I/O port with internal pullups

Pin no 1 to 8

Port 2 - Port 2 is an 8-bit bi-directional I/O port with internal pullups

Pin no 21 to 28

Port 3 - Port 3 is an 8-bit bi-directional I/O port with internal pullups

Pin no 10 to17.

RST - Reset input. A high on this pin for two machine cycles while the

oscillator is running resets the device.

ALE/PROG - Address Latch Enable 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.

PSEN - Program Store Enable is the read strobe to external program

memory. When the AT89C52 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 FFFFH. EA should be strapped to VCC

for internal program executions.

This pin also receives the 12-volt programming enable voltage (VPP)

during Flash programming when 12-volt programming is selected.

XTAL1 - Input to the inverting oscillator amplifier and input to the internal

clock operating circuit.

XTAL2 - Output from the inverting oscillator amplifier

AT89S52 MICROCONTROLLER

FEATURES :

> Internal Timers/Event Counters

> 2-Level Interrupt Priority Structure

> 32 I/O Lines (Four 8-Bit Ports)

> 64K Program Memory Space

> Security Features Protects EPROM Parts Against Software Piracy

> Boolean Processor

> Bit-Addressable RAM

> Programmable Full Duplex Serial Channel

> 111 Instructions (64 Single-Cycle)

> 64K Data Memory Space

Block Diagram of AT89S52

Internal Block Diagram of AT89S52

Types of Memory:

The 8051 has three very general types of memory. To effectively program the

8051 it is necessary to have a basic understanding of these memory types.

On-Chip Memory refers to any memory (Code, RAM, or other) that

physically exists on the microcontroller itself. On-chip memory can be of

several types, but we'll get into that shortly.

External Code Memory is code (or program) memory that resides off-

chip. This is often in the form of an external EPROM.

External RAM is RAM memory that resides off-chip. This is often in

the form of standard static RAM or flash RAM.

FIGURE Memory Types

Code Memory

Code memory is the memory that holds the actual 8051 program that is to

be run. This memory is limited to 64K and comes in many shapes and

sizes: Code memory may be found

External RAM

As an obvious opposite of Internal RAM, the 8051 also supports

what is called External RAM. As the name suggests, External RAM is

any random access memory which is found off-chip.. To increment a 1-

byte value stored in External RAM requires 4 instructions and 7

instruction cycles. In this case, external memory is 7 times slower! What

External RAM loses in speed and flexibility it gains in quantity. While

Internal RAM is limited to 128 bytes the 8051 supports External RAM up

to 64K.

Microcontroller connection to RS232:

The microcontroller has two pins that are used specifically for

transferring and receiving data serially. These two pins are called TxD and RxD

and are the part of the port 3 group(P3.0 and P3.1).Pin 11 of 89S52 (P3.1) is

assigned to TxD and Pin 10(P3.0) is designated as RxD. These pins are TTL

compatible; therefore they require a line driver to make them RS232

compatible. One such line driver is MAX232.

The MAX232 converts from RS232 voltage levels to TTL voltage levels,

and vice versa.One advantage of the MAX232 is that it uses a +5V power

source which is same as the source voltage for the 89S52.

Inside MAX 232

The T1in pin is the TTL side and is connected to TxD of the microcontroller,

while the T1out is the RS232 side that is connected to the RxD pin of the

RS232 DB coonector.The R1in (pin 13)is the RS232 side that is connected to

the TxD pin of the RS232 DB-connector, and R1out (pin 12)is the TTL side

that is connected to the RxD pin of the microcontroller. MAX 232 requires 4

capacitors ranging from 1 to 22 micro farad. The most widely used is 22 micro

farad.

it’s connection to 89s52

Serial Pin outs (D25 and D9 Connectors)

MAX 232The MAX232 is a dual driver/receiver that includes a capacitive voltage

generator to supply RS 232 voltage levels from a single 5V supply. Each

receiver converts RS 232 inputs to 5V TTL/CMOS levels. Each driver converts

TTL/CMOS input levels into RS 232 levels.

Pin out of MAX 232

FIGURE 2.8

Function Table for each driver Function Table for each receiver

TABLE 2.6

Serial communication using MAX 232

Input Tin

Output Tout

L

H

H

L

FIGURE 2.9

Liquid Crystal Display

In recent years the LCD is finding widespread use replacing LEDs This

is due to following reasons

1) The declining prices of LCDs

2) The ability to display numbers, characters and graphics. This is in

contrast to LEDs, which are limited to numbers and few characters.

3) Incorporation of a refreshing controller in to LCD, there by relieving the

CPU of the task of refreshing the LCD. In contrast LCD must be

refreshed by CPU to keep displaying the data.

LCD display

The internal structure of LCD module:

LCD is connected to the microcontroller through the controller

interface. LCD has an internal memory which stores the lookup table for all the

characters. Any ASCII value of a character that is passed to the LCD module is

compared with the lookup table in the memory and that value is displayed

Internal structure of LCD module.

Interfacing LCD with microcontroller

Interfacing LCD with microcontroller is very easy task. You just have to

know the proper LCD programming algorithm. LCD used here has HD44780u

dot matrix LCD controller. LCD module has 8-bit data interface and control

pins. One can send data as 8-bit or in pair of two 4-bit nibbles. 

To display any character on LCD micro controller has to send its ASCII

value to the data bus of LCD. For e.g. to display 'AB' microcontroller has to

send two hex bytes 41h and 42h respectively. LCD display used here is having

16x2 size. It means 2 lines each with 16 characters.

Internal block diagram

FIGURE 2.6

Internal Block Diagram of LM 7805

Pin out of LM 7805 (TO – 220 PACKAGE)

FIGURE 2.7

SOFTWARE REQUERMENT

Introduction to keil µVision3

The µVision3 IDE is a Windows-based software development platform

that combines a robust editor, project manager, and make facility. µVision3

integrates all tools including the C compiler, macro assembler, linker/locator,

and HEX file generator. The µVision3 IDE offers numerous features and

advantages that help you quickly and successfully develop embedded

applications. They are easy to use and are guaranteed to help you achieve your

design goals.

Features

1) The µVision3 Simulator is the only debugger that completely simulates

all on-chip peripherals.

2) Simulation capabilities may be expanded using the Advanced Simulation

Interface (AGSI).

3) µVision3 incorporates project manager, editor, and debugger in a single

environment.

4) The µVision3 Device Database automatically configures the

development tools for the target microcontroller.

1. INPUT

2. GROUND

3. OUTPUT

5) The µVision3 IDE integrates additional third-party tools like VCS,

CASE, and FLASH/Device Programming.

6) The ULINK USB-JTAG Adapter supports both Debugging and Flash

programming with configurable algorithm files.

7) Identical Target Debugger and Simulator User Interface.

8) The Code Coverage feature of the µVision3 Simulator provides statistical

analysis of your program's execution.

Embedded C:

When designing software for a smaller embedded system with the 8051,

it is very common place to develop the entire product using assembly code.

With many projects, this is a feasible approach since the amount of code that

must be generated is typically less than 8 kilobytes and is relatively simple in

nature. If a hardware engineer is tasked with designing both the hardware and

the software, he or she will frequently be tempted to write the software in

assembly language.

POWER SUPPLY UNIT

The circuit needs two different voltages, +5V & +12V, to work.

These dual voltages are supplied by this specially designed power supply. [6]

The power supply, unsung hero of every electronic circuit, plays very

important role in smooth running of the connected circuit. The main object of

this ‘power supply’ is, as the name itself implies, to deliver the required amount

of stabilized and pure power to the circuit.

The stabilization of DC output is achieved by using the three terminal

voltage regulator IC. This regulator IC comes in two flavors: 78xx for positive

voltage output and 79xx for negative voltage output. For example 7812 gives

+12V output and 7912 gives -12V stabilized output. These regulator ICs have

in-built short-circuit protection and auto-thermal cutout provisions. If the load

current is very high the IC needs ‘heat sink’ to dissipate the internally generated

power. [6]

Fig 3.1: Voltage Regulator IC

KIA 78xx

1 2 3

KIA 78xxSeries

REGULATED POWER S CIRCUIT DIAGRAM OF

+5V & +12V FULL WAVE UPPLY

A C D E

F

components List

SEMICONDUCTORS

IC1

IC2

7812 Regulator IC

7805 Regulator IC

1

1

D1& D2 1N4007 Rectifier Diodes 2

CAPACITORS

C1 1000 µf/25V Electrolytic 1

C2 to C4 0.1µF Ceramic Disc type 3

MISCELLANEOUS

X1 230V AC Pri,14-0-14 1Amp Sec Transformer 1

CIRCUIT DESCRIPTION

B

C1

D21

C2

C3

IC17812

D11

C4

9V

IC17805

+12V

+5V

A DC power supply which maintains the output voltage constant

irrespective of AC. mains fluctuations or load variations is known as regulated

DC. power supply. It is also referred as full-wave regulated power.

Supply as it uses two diodes with the transformer. This laboratory power supply

offers excellent line and load regulation and output voltages of +5V & +12 V at

output currents up to one ampere.

1. Step-down Transformer: The transformer rating is 230V AC at Primary

and 12-0-12V, 1Ampers across secondary winding. This transformer has a

capability to deliver a current of 1Ampere, which is more than enough to drive

any electronic circuit or varying load. The 12VAC appearing across the

secondary is the RMS value of the waveform and the peak value would be 12 x

1.414 = 16.8 volts. This value limits our choice of rectifier diode as 1N4007,

which is having PIV rating more than 16Volts [6]

2. Rectifier Stage: The two diodes D1 & D2 are connected across the

secondary winding of the transformer as a full-wave rectifier. During the

positive half-cycle of secondary voltage, the end A of the secondary winding

becomes positive and end B negative. This makes the diode D1 forward biased

and diode D2 reverse biased. Therefore diode D1 conducts while diode D2 does

not. During the negative half-cycle, end A of the secondary winding becomes

negative and end B positive. Therefore diode D2 conducts while diode D1 does

not. Note that current across the centre tap terminal is in the same direction for

both half-cycles of input AC. voltage. Therefore, pulsating DC. Is obtained at

point ‘C’ with respect to Ground.[6]

3. Filter Stage: Here Capacitor C1 is used for filtering purpose and connected

across the rectifier output. It filters the AC. components present in the rectified

DC. and gives steady DC. voltage. As the rectifier voltage increases, it charges

the capacitor and also supplies current to the load. When capacitor is charged to

the peak value of the rectifier voltage, rectifier voltage starts to decrease. As the

next voltage peak immediately recharges the capacitor, the discharge period is

of very small duration. Due to this continuous charge-discharge-recharge cycle

very little ripple is observed in the filtered output. Moreover, output voltage is

higher as it remains substantially near the peak value of rectifier output voltage.

This phenomenon is also explained in other form as: the shunt capacitor offers a

low reactance path to the AC. components of current and open circuit to DC.

component. During positive half cycle the capacitor stores energy in the form of

electrostatic field. During negative half cycle, the filter capacitor releases stored

energy to the load.

4. Voltage Regulation Stage: Across the point ‘D’ and Ground there is

rectified and filtered DC. In the present circuit KIA 7812 three terminal voltage

regulator IC is used to get +12V and KIA 7805 voltage regulator IC is used to

get +5V regulated DC. output. In the three terminals, pin 1 is input i.e., rectified

& filtered DC. is connected to this pin. Pin 2 is common pin and is grounded.

The pin 3 gives the stabilized DC. output to the load. The circuit shows two

more decoupling capacitors C2 & C3, which provides ground path to the high

frequency noise signals. Across the point ‘E’ and ‘F’ with respect to ground

+5V & +12V stabilized or regulated DC output is measured, which can be

connected to the required circuit.[6]

BUFFER AND DRIVER

BUFFER CIRCUIT

The BUFFER IC used is IC 4050 which is a voltage amplifier; its a non-inverting buffer. A buffer doesn’t change the logical state and it also provides an extra voltage drive.

This 16-pin DIL packaged IC 4050

Acts as Buffer as-well-as a Converter. The

input signals may be of 2.5 to 5V digital

TTL compatible or DC analogue the IC

gives constant output voltage. The IC acts

as buffer and provides isolation to the

main circuit from varying input signals.

Here the IC is use to increase the voltage. It

acts as a voltage amplifier.

DRIVER CIRCUIT

The driver circuit is used to enhance the current handling capacity in the circuit.

Moreover its acts as a driving circuit for the relays. The IC ULN 2004 is

used, this IC consist of an array of emitter-follower circuits.

Fig 3.4: Basic Darlington Pair Circuit

1

2

6

3

16

5

15

4

14

10

11

12

13

7

Vcc

Vss 8 9

IC 4050

Normally to turn on a transistor the base input voltage of the transistor

will need to be greater that 0.7V. As two transistors are used in Darlington Pair

this value is doubled. Therefore the base voltage will need to be greater than

0.7V x 2 = 1.4V. [8]

The output current Ic = total gain (β) * input current.

The DRIVER IC used is ULN 2004. [8]

PIN DESCRIPTION

The UTC ULN2004 are high-voltage, high-current Darlington drivers comprised of NPN Darlington pairs. All units feature integral clamp diodes for switching inductive loads. Applications include relay, hammer, lamp and display (LED) drivers. [9]

3.2.4 FEATURES OF IC ULN2004

Output current (single output): 500mA (MAX.) High sustaining voltage output: 50V (MIN.)

Output clamp diodes

Inputs compatible with various types of logic. [9]

CIRCUIT DIAGRAM OF BUFFER AND DRIVER CIRCUIT

From RF/IRReceiver stage

Fig 3.7: Circuit Diagram of Buffer and Driver

+12 v V

IC14050

IC22004

1

8

93 2 1 1

6

+VCC

VCC

D1 1N4148

GND

N/ON/C

N/ON/C

N/ON/C

N/O

N/C

5 4 2 15

7 6 3 14

12

11

5 12

9 10 1

2

4 13

1111

14

15

6

IC ULN 2004

RELAYS

INTRODUCTION

A relay is an electrically operated switch. Current flowing through the

coil of the relay creates a magnetic field which attracts a lever and changes

the switch contacts. The coil current can be on or off, so relays have two

switch positions and they are double throw (changeover) switches.

Relays allow one circuit to switch a second circuit which can be

completely separate from the first. For example a low voltage battery circuit

can use a relay to switch a 230V AC mains circuit. There is no electrical

connection inside the relay between the two circuits, the link is magnetic and

mechanical.

The coil of a relay passes a relatively large current, typically 30mA

for a 12V relay, but it can be as much as 100mA for relays designed to

operate from lower voltages. Most ICs (chips) cannot provide this current

and a transistor is usually used to amplify the small IC current to the larger

value required for the relay coil. The maximum output current for the

popular 555 timer IC is 200mA so these devices can supply relay coils

directly without amplification.

Relays are usually SPDT or DPDT but they can have many more sets

of switch contacts, for example relays with 4 sets of changeover contacts are

readily available. Most relays are designed for PCB mounting but you can

solder wires directly to the pins providing you take care to avoid melting the

plastic case of the relay.

The coil will be obvious and it may be connected either way round.

Relay coils produce brief high voltage 'spikes' when they are switched off

and this can destroy transistors and ICs in the circuit. To prevent damage

you must connect a protection diode across the relay coil.

The animated picture shows a working relay with its coil and switch

contacts. You can see a lever on the left being attracted by magnetism when

the coil is switched on. This lever moves the switch contacts. There is one

set of contacts (SPDT) in the foreground and another behind them, making

the relay DPDT.

Figure 6.2 Relay showing coil and switches

The relay's switch connections are usually labeled COM, NC and NO:

COM = Common, always connect to this, it is the moving part of the

switch.

NC = Normally Closed, COM is connected to this when the relay coil

is off.

NO = Normally Open, COM is connected to this when the relay coil

is on.

Connect to COM and NO if you want the switched circuit to be on

when the relay coil is on.

Connect to COM and NC if you want the switched circuit to be on

when the relay coil is off.

CHOOSING A RELAY

Physical size and pin arrangement : If you are choosing a relay for

an existing PCB you will need to ensure that its dimensions and pin

arrangement are suitable.

Coil voltage : The relay's coil voltage rating and resistance must suit

the circuit powering the relay coil. Many relays have a coil rated for a

12V supply but 5V and 24V relays are also readily available. Some

relays operate perfectly well with a supply voltage which is a little

lower than their rated value.

Coil resistance: The circuit must be able to supply the current

required by the relay coil. You can use Ohm's law to calculate the

current: Relay coil current = supply voltage / coil resistance

The relay's switch connections are usually labeled COM, NC and NO:

COM = Common, always connect to this; it is the moving part of the

switch.

NC = Normally Closed, COM is connected to this when the relay coil is

off.

NO = Normally Open, COM is connected to this when the relay coil is on.

Figure 3.14: Circuit Symbol of Relay

Connect to COM and NO if you want the switched circuit to be on when

the relay coil is on.

Connect to COM and NC if you want the switched circuit to be on when

the relay coil is off.

We need to consider several features when choosing a relay:

•Physical size and pin arrangement

If you are choosing a relay for an existing PCB you will need to

ensure that its dimensions and pin arrangement are suitable. You should find

this information in the supplier's catalogue.

Relays and transistors compared

Like relays, transistors can be used as an electrically operated

switch. For switching small DC currents (< 1A) at low voltage they are

usually a better choice than a relay. However transistors cannot switch AC

or high voltages (such as mains electricity) and they are not usually a good

choice for switching large currents (> 5A).

Advantages of relays:

• Relays can switch AC and DC, transistors can only switch DC.

• Relays can switch high voltages, transistors cannot.

• Relays are a better choice for switching large currents (> 5A).

• Relays can switch many contacts at once.

Disadvantages of relays:

• Relays are bulkier than transistors for switching small currents.

• Relays cannot switch rapidly (except reed relays), transistors can

switch many times per second.

• Relays use more power due to the current flowing through their coil.

• Relays require more current than many ICs can provide, so a low

power transistor may be needed to switch the current for the relay's

coil.

GSM (GLOBAL SYSTEM FOR MOBILE

COMMUNICATION)

TECHNICAL DETAILS

Global System for Mobile communications is the most popular

standard for mobile phones in the world. Its promoter, the GSM Association,

estimate that 82% of the global mobile market uses the standard. GSM is

used by over 2 billion people across more than 212 countries and territories.

Its ubiquity makes international roaming very common between mobile

phone operators, enabling subscribers to use their phones in many parts of

the world.

GSM has used a variety of voice codecs to squeeze 3.1 kHz audio into

between 5.6 and 13 kbit/s. Originally, two codecs, named after the types of

data channel they were allocated, were used, called Half Rate (5.6 kbit/s)

and Full Rate (13 kbit/s). These used a system based upon linear predictive

coding (LPC). In addition to being efficient with bit rates, these codecs also

made it easier to identify more important parts of the audio, allowing the air

interface layer to prioritize and better protect these parts of the signal.

The modulation used in GSM is Gaussian minimum-shift keying (GMSK), a

kind of continuous-phase frequency shift keying. In GMSK, the signal to be

modulated onto the carrier is first smoothed with a Gaussian low-pass filter

prior to being fed to a frequency modulator, which greatly reduces the

interference to neighboring channels (adjacent channel interference).

SUBSCRIBER IDENTITY MODULE (SIM)

One of the key features of GSM is the Subscriber Identity Module

(SIM), commonly known as a SIM card. The SIM is a detachable smart card

containing the user’s subscription information and phonebook. This allows

the user to retain his or her information after switching handsets.

Alternatively, the user can also change operators while retaining the handset

simply by changing the SIM. Some operators will block this by allowing the

phone to use only a single SIM, or only a SIM issued by them; this practice

is known as SIM locking, and is illegal in some countries.

A subscriber can usually contact the provider to remove the lock for a

fee, utilize private services to remove the lock, or make use of ample

software and websites available on the Internet to unlock the handset

themselves. While most web sites offer the unlocking for a fee, some do it

for free. The locking applies to the handset, identified by its International

Mobile Equipment Identity (IMEI) number, not o the account (which is

identified by the SIM card). It is always possible to switch to another (non-

locked) handset if such a handset is available.

GSM MODEMS

A modem is a communication device that converts binary into analog

acoustic signals for transmission over telephone lines and converts these

acoustics signals back into binary form at the receiving end. Conversion to

analog signal is known as modulation; conversion back to binary signal is

known as demodulation.

In the terminology used in the RS-232C communication standard,

modems are DCEs, which mean the connected at one end to a DTE (e.g.

computer) device. Low-speed modems are designed to operate

asynchronously. Each data frame conforms an asynchronous transmission

mechanism.

High-speed modems as well as leased-lines modems use synchronous

transmission. The two modems use a common time base and operate

continuously at substantially the same frequency and the phase relationship

by circuit that monitors the connection.

A half-duplex modem must alternately send and received signals.

Half-duplex allows more of the channel bandwidth to be put to use but slows

data communications.

A full-duplex modem can simultaneously handle two signals using

two carriers to transmit and receive data. Each carrier uses a half of the

bandwidth available to it and its modulation.

ASK is not used For data communications because it is very

susceptible to electrical noise interference. Low-speed modems use FSK,

higher speed modems use PSK, and the very high speed modems use a

conjunction of ASK and PSK.

The SMS/MMS Gateway requires a connection to an SMSC (Short

Messaging Service Centre) to interface with SMS and MMS networks.

An SMSC connection can consist of one or more of the following:

GSM Modem – A GSM modem or phone connected to a PC serial

port (or to a USB port with an appropriate modem driver).

SMPP (Short Message Peer to Peer Protocol) – A TCP/IP connection

over the internet or a private network to a service that supports v3.3 or

v3.4 of the SMPP protocol.

UCP/EMI (Universal Computer Protocol/ External Machine Interface)

– A TCP/IP connection over the internet or a private network to a

service that supports v3.5 or v4.0 of the UCP/EMI protocol.

HTTP (Hyper Text Transfer Protocol, e.g., the standard protocol for

the “web”) – A TCP/IP connection over the internet or private

network to a service that accepts SMS messages via an HTTP “GET”

based protocol allows you to chain multiple Now SMS/MMS

Gateways together.)

NOKIA 3310: GSM modems

A GSM modem can be an external modem device. 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 card installed in a notebook computer. 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 3310, 7110 with a F-bus, M-bus, DLR-

3 cable, or various Ericsson phones are often used for this purpose.

Figure 3.17: F-Bus Connection

The very popular Nokia 3310 has the F/M Bus connection under the

battery holder. This is a bit of a pain to get to and requires a special cable to

make the connection.The right picture above shows the 4 gold pads used for

the F and M Bus. The left picture shows the F-Bus cable connected to my

Nokia 3310.

Figure 3.18: F- Bus and the modem

GSM (Global System for Mobile communication) is a digital mobile

telephony system that is widely used in Europe and other parts of the world.

GSM uses a variation of time division multiple access TDMA) and is the

most widely used of the three digital wireless telephony technologies

(TDMA, GSM, and CDMA). GSM digitizes and compresses data, then

sends it down a channel with two other streams of user data, each in its own

time slot. It operates at either the 900 MHz or 1800 MHz frequency band.

Mobile services based on GSM technology were first launched in

Finland in 1991. Today, more than 690 mobile networks provide GSM

services across 213 countries and GSM represents 82.4% of all global

mobile connections. According to GSM World, there are now more than 2

billion GSM mobile phone users worldwide. GSM World references China

as "the largest single GSM market, with more than 370 million users,

followed by Russia with 145 million, India with 83 million and the USA

with 78 million users."

Since many GSM network operators have roaming agreements with

foreign operators, users can often continue to use their mobile phones when

they travel to other countries. SIM cards (Subscriber Identity Module)

holding home network access configurations may be switched to those will

metered local access, significantly reducing roaming costs while

experiencing no reductions in service.

GSM, together with other technologies, is part of the evolution of

wireless mobile telecommunications that includes High-Speed Circuit-

Switched Data (HCSD), General Packet Radio System (GPRS), Enhanced

Data GSM Environment (EDGE), and Universal Mobile

Telecommunications Service.

DEFINITION

Global System for Mobile (GSM) is a second generation cellular

standard developed to cater voice services and data delivery using digital

modulation.

GSM IN WORLD

GSM IN INDIA

WORKING OF GSM MODEM

Sending SMS Messages from a microcontroller using a GSM Modem:

A GSM modem is a wireless modem that works with GSM wireless

networks. A wireless modem is similar to a dial-up modem. The main

difference is that a wireless modem transmits data through a wireless

Figures: March, 2005

37%

1%4%43%

4%

3%3%

3% (INDIA)

3%

Arab World

Asia Pacific

Africa

East Central Asia

Europe

Russia

India

North America

South America

Figures: March 2005

Bharti27%

BSNL22%

Spice 4%

IDEA13%

Hutch19%

BPL6%

Aircel4%

Reliance3%

MTNL2%

Bharti

BSNL

Hutch

IDEA

BPL

Aircel

Spice

Reliance

MTNL

network whereas a dial-up modem transmits data through a copper telephone

line. Most mobile phones can be used as a wireless modem.

To send SMS messages, first place a valid SIM card into a GSM

modem, which is then connected to microcontroller by RS232 cable. After

connecting a GSM modem to a microcontroller, you can control the GSM

modem by sending instructions to it. The instructions used for controlling

the GSM modem are called AT commands. GSM modems support a

common set of standard AT commands. In addition to this common set of

standard AT commands, GSM modems support an extended set of AT

commands. One use of the extended AT commands is to control the sending

and receiving of SMS messages.

The following table lists the AT commands that are related to the

writing and sending of SMS messages:

AT command Meaning

+CMGS Send message

+CMSS Send message from storage

+CMGW Write message to memory

+CMGD Delete message

+CMGC Send command

+CMMS More messages to send

Table 8.1 GSM AT Commands

One way to send AT commands to a GSM modem is to use a

program. A program's function is like this:

It sends the characters you typed to the GSM modem. It then displays

the response it receives from GSM modem on the screen.

Below shows a simple example that demonstrates how to use AT commands.

AT

OK

AT+CMGF=1

OK

AT+CMGW="+85291234567"

> A simple demo of SMS text messaging.

+CMGW: 1

OK

AT+CMSS=1

+CMSS: 20

OK

Here is a description of what is done in the above example:

Line 1: "AT" is sent to the GSM modem to test the connection. The GSM

modem sends back the result code "OK" (line 2), which means the

connection between the program and the GSM modem works fine.

Line 3: The AT command +CMGF is used to instruct the GSM modem to

operate in SMS text mode. The result code "OK" is returned (line 4), which

indicates the command line "AT+CMGF=1" has been executed successfully.

If the result code "ERROR" is returned, it is likely that the GSM modem

does not support the SMS text mode. To confirm, type "AT+CMGF=?" in

the program. If the response is "+CMGF: (0, 1)" (0=PDU mode and 1=text

mode), then SMS text mode is supported. If the response is "+CMGF: (0)",

then SMS text mode is not supported.

Line 5 and 6: The AT command +CMGW is used to write an SMS text

message to the message storage of the GSM modem . "+85291234567" is

the recipient mobile phone number.

Line 7: "+CMGW: 1" tells us that the index assigned to the SMS text

message is 1. It indicates the location of the SMS text message in the

message storage.

Line 9: The result code "OK" indicates the execution of the AT command

+CMGW is successful.

Line 10: The AT command +CMSS is used to send the SMS text message

from the message storage of the GSM modem. "1" is the index of the SMS

text message obtained from line 7.

Line 11: "+CMSS: 20" tells us that the reference number assigned to the

SMS text message is 20.

Line 13: The result code "OK" indicates the execution of the AT command

+CMSS are successful.

By using the above procedure message is sent by the GSM modem.

8.3 Characteristics of GSM Standard:

Fully digital system using 900,1800 MHz frequency band.

TDMA over radio carriers(200 KHz carrier spacing.

8 full rate or 16 half rate TDMA channels per carrier.

User/terminal authentication for fraud control.

Encryption of speech and data transmission over the radio path.

Full international roaming capability.

Low speed data services (upto 9.6 Kb/s).

Compatibility with ISDN.

Support of Short Message Service (SMS).

8.4 Advantages of GSM over Analog system:

Capacity increases.

Reduced RF transmission power and longer battery life.

International roaming capability.

Better security against fraud (through terminal validation and user

authentication).

Encryption capability for information security and privacy.

Compatibility with ISDN, leading to wider range of service.

GSM Applications:

Mobile telephony.

GSM-R.

Value Added Services.

Telemetry System

Fleet management.

Automatic meter reading.

Toll Collection.

Remote control and fault reporting of DG sets.

SMS: SMS is an area where the modem can be used to provide features like:

• Pre-stored SMS transmission

• These SMS can be transmitted on certain trigger events in an automation

system

• SMS can also be used in areas where small text information has to be sent.

The transmitter can be an automation system or machines like vending

machines, collection machines or applications like positioning systems

where the navigator keeps on sending SMS at particular time intervals

• SMS can be a solution where GSM data call or GPRS services are not

available [21]

Fig 5.1 : Basic Architecture of GSM Module

8.ESTIMATED COSTSI.NO PARTICULARS UNIT QUANTITY RATE AMOUNT

RS.PS RS.PS

1 PROJECT KIT NO 1 11,000 11,000

a) GSM MODEM

b) LCD DISPLAY

c) POWER SUPPLY

d) RELAYS

e) PCB BOARD

f) IC 89s52(MC)

g) SIM

h) PATCH CHARDS

2 MODEL

a) PLY WOOD (1.9ft*1.9ft) FT 1 500 500

b) FIBER SHEETS(8ft*8ft) FT 1 895 895

c) TRANSFORMERS (12-0-12) NO 2 250 1000

d) RADIUM

i) RED (5cm*5cm) CM 1 50 50

ii) GREEN (5cm*5cm) CM 1 30 30

iii) WHITE (5cm*5cm) CM 1 20 20

iv) BLACK (6cm*2ft) CM*FT 1 100 100

e) MORBEL SHEETS A4 10 5 50

f) GLASS DEADING (10mm) METER 2 10 20

TOTAL AMOUNT 13,665 13,665

GRAND TOTAL AMOUNT OF OUR PROJECT IS=13,665/-

9.ADVANTAGES

Power scheduling time can be reduced.

Wastage of power can be reduced.

Line engineer can easily know for which transformer fault has

occurred.

Line engineer can easily know what fault has occurred to

transformer.

The main advantage of this project is gsm modem because it helps

to send the fault description sms to line engineer.

10.DISADVANTAGES

When network fails this project can’t work.

The main disadvantage is trouble shooting of transformer

is not possible.

.

11.APPLICATIONS

We can implement this project

It is a real time application

It can used in distributer transformer

It is used in power transformer

It is used in agriculture

11.CONCLUSION

By conducting this project we concluded that this project is a real time

application and we can implement this project. By this we alerted the line

engineer by faults occurred in the transformer. We can reduce the human

power and also we can reduce the line engineer work.

12.BIBLOGRAPHY

1. Asha Mehrotra, “Artech House - GSM System Engineering”, Artech

House, Inc.

Boston, London (1997)

2. Gwenaël Le Bodic, “Mobile Messaging Technologies and Services: SMS,

EMS

and MMS”, Second Edition, John Wiley & Sons, Ltd. (2005)

3. Kevin Collins, “PLC Programming for Industrial Automation”, Exposure

Publishing (2006)

4. L. A. Bryan, E. A. Bryan , “Programmable Controllers, theory and

implementation”, Second Edition, An Industrial Text Company Publication,

Atlanta • Georgia • USA (1997)

5. Unitronics, a global company, a designer, developer, producer & marketer

of

Programmable logic Controllers, http://www.unitronics.com/

6. GSMA, association that represents the interests of the worldwide mobile

communications industry,

http://www.gsmworld.com/technology/index.htm