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DTMF BASED SECURITY FOR ATM AND SMS ALERTING SYSTEM

CHAPTER 1

INTRODUCTION

As we all know that today, ATM centers are used by most of the people. such as

students, employees, business people etc., who will be busy during working hours of bank,

are feeling comfortable to use ATM centres for their transactions.

ATM’s became successful in a very short time due to the following reasons-

1. ATM’s will be open for all the 24 hours of the day and all the 7 days of the week.

2. Time will be saved when compared to the direct transactions in bank.

3. There is no need to carry huge amount when travelling to long distances.

But today, hacking is taking place in ATM centres. Hackers use to place the sensors in

the place where we insert the ATM card and using this, they will collect ATM card number,

password and other information. Using this information, they will prepare fake ATM card

and they are withdrawing amount from others account. This type of fraud is increasing day

by day. So we finding a solution to that using our project.

DEPARTMENT OF ELECTRONICS & COMMUNICATION ENGINEERING,PDACEG


CHAPTER 2

LITERATURE SURVEY

The system envisioned by NTT, utilizes a conversion method which takes digital data

into a stream of low power digital pulses. These can be easily transmitted and can be read

back through the human electric field.

While it is true that similar personal area networks are already accessible by using

radio based technologies like Wi-Fi or Bluetooth, this new wireless technology claims to be

able to send data over the human skin surface at transfer speed of up to 10 Mbps, or better

than a broadband connection. Receiving data in such a system is more complicated because

the strength of the pulses sent through the electric field is so low.

Redtacton solves this issue by utilizing a technique called electric field photonics. A

laser is passed through an electro optic crystal, which deflects light differently according to

the strength of the field across it. These deflections are measured and converted back into

electrical signals to retrieve the transmitted data.

According to Tom Zimmerman, inventor of the IBM personal networking system,

body based networking is more secure than broadcast systems, such as Bluetooth, which

have a range of about 10m. The issue is that with Bluetooth, it is difficult to rein in the signal

and restrict it to device we are trying to connect to. But in a busy place there could be

hundreds of Bluetooth devices within range.

Moreover, body-based networking seems to allow for more natural interchanges of

information between humans, as only when we are in true proximity we can make this

system work. There are some specific applications that would appear as being ideal matches

for Redtacton like technologies.



CHAPTER 3

MAIN BLOCK DIAGRAM OF THE PROJECT

DTMF GENERATOR

INFRAREDTRANSMITTER

SIGNALCONDITIONER

DOOR/MAG SENSOR

FILTER

EMBEDDED MICROCONTROLLER

ATMEL'S 89C52

TRANSFORMER

BUZZERDRIVER

DCOUTPUT

MAINS ACINPUT

REGULATOR

MATRIXKEYPAD

16 X 2 LCD DISPLAY UNIT

MODEMINTERFACE

LIMITSWITCHES

H-BRIDGE

CIRCUIT

GATE

MOTOR

DTMF DECODER

INFRAREDRECEIVER

RECTI-FIER

BUZZER

GSM MODEM

Fig 3.1 main block diagram of the system

The system consists of the fallowing sub-sections

1. IR Based Intrusion Sense System.

2. DTMF Encoder.

3. DTMF Decoder.

4. Matrix Keyboard.

5. LCD Display Unit.

6. Buzzer.

7. GSM Module



8. DC motor.

9. Embedded microcontroller

10. Power Supply.

3.1 IR BASED INTRUSION SENSE SYSTEM

This is placed at the entrance of the building to sense the arrival of any intruder. It

uses invisible light beam as a barrier and consists of a IR Transmitter and a IR Receiver. IR

Transmitter is placed at one side of the gate and the IR Receiver is placed on the opposite

side. They are placed face to face, so that the IR light falls straight on the receiver. The IR

transmitter transmits an invisible modulated (38 KHz) IR light beam pointing towards the IR

receiver unit. It consists of a 38 KHz oscillator and IR Light Emitting Diode and Sensor

section consists of 3-terminal IR Sensors. These sensors are sensitive to 38 KHz. They

produce TTL compatible signals when a coded IR light beam is incident on them. This signal

is sensed by the microcontroller and used for further processing. The IR receiver is un-

affected by the surrounding natural light. When any person tries to enter the building, he/she,

unknowingly interrupts this invisible light beam. The sensor then sends a signal to the

microcontroller, indicating that the person has entered the premises.

3.2 DTMF ENCODER

DTMF Encoder is used as transmitter. The data transmitted from DTMF transmitter

to DTMF receiver will be in numerical form. To transmit this numerical data to receiver, we

are using DTMF technique.

3.3 DTMF DECODER

Decoder is used to decode the signal transmitted by encoder and to convert it into

binary form. DTMF decoder is used in Receiver system.

3.4 MATRIX KEYPAD

We have used a 4 X 4 matrix keyboard ,for entering the password ,and other input

parameters. Which is interfaced with the microcontroller of the system, if the entered



password is correct system allows user for further processing ,if the entered password

happens to be wrong then buzzer will sounds ,indicating an unauthorized person trying to use

ATM system.

3.5 LCD DISPLAY UNIT

A LCD display module is used for displaying various prompts and status information

of the system. It is also used display the title messages and other messages while

communicating with the Slave nodes on the network.

3.6 BUZZER

Whenever any abnormality is sensed by the microcontroller in communicating with

various slave nodes in the network, an audio tone is produced by a buzzer, indicating that an

unauthorized person is trying to communicate with ATM system.

3.7 GSM MODULE

When unauthorized person caught inside the ATM premises an SMS is sent to higher

authority of the ATM by GSM module which is interfaced with microcontroller.

3.8 DC MOTOR

A DC motor is used in our system to open/close mechanism of Door.

3.9 EMBEDED MICROCONTROLLER.

It is the heart of entire system which controls the whole system.

3.10 POWER SUPPLAY

It provides the power to all sections of the system.



CHAPTER 4

METHEDOLOGY

4.1 MICROCONTROLLER 89C52

4.1.1 SELECTION OF A MICROCONTROLLER

A microcontroller is basically a small computer for embedded applications. They are

programmable, with features like input and output pins, serial communication interfaces,

memory for data storage (RAM), memory for program storage (ROM, EPROM, EEPROM,

or Flash memory), and analog-to-digital converters. The number and availability of these and

other features vary from model to model, as does the programming language and interface.

Today, microcontrollers are incorporated in many devices used in our daily lives. For

example, office automation equipment such as copiers and factory automation equipment in

plants are equipped with one or more microcontrollers. It is almost difficult to find a device

that does not have one. Microcontrollers are used for a wide range of applications and there

are a lot of different ways to select one. You have to organize your own opinions beforehand,

because the points to be considered may vary depending on the product you are planning to

develop. On what criteria should an engineer make a choice among microcontrollers, which

are used in various applications? This article discusses the considerations in selecting a

microcontroller.

There are a wide variety of microcontrollers available and even if you have decided

on which series to use, you still have plenty of choices. Engineers must have their own

criteria in order to make the right selection. This article discusses the general considerations

and some tips to keep in mind when selecting a microcontroller, serving as a basis for setting

your own criteria. Choosing a suitable Microcontroller for your Embedded system is the most

important and essential part of Embedded System Design.

Selecting a wrong Microcontroller may introduce many unwanted and unavoidable

hurdles to complete the system design without errors and in scheduled time, like:



Increase the complexity of project, which may cause to miss the schedule

Increase the cost of the end product

Increase the board size

Need extra time, expertise, effort, materials and components and many more.......

When you chose a microcontroller, you must examine the delivery time, costs,

development assets and development environment, in addition to the product specifications.

It must be noted that almost all the MCU manufacturers have competitive specifications and

product-line in each segment, which means although there won’t be pin-to-pin matches you

will easily find replacements for certain MCU from each of these manufacturers. And

therefore, familiarity, convenience, prior relations, etc. would suggest which MCU to be

selected.

On performance basis:

MIPS of Microcontroller. Millions of Instructions executed in a second indicates the speed

of a microcontroller. A microcontroller selected should have optimum speed to support the

proposed project or product.

Word Size or Bit Size of the Microcontroller. For example, if a system functionality can be

implemented using an 8-bit Microcontroller, instead of using 16-Bit or 32-Bit

Microcontroller. This may increase the complexity of the project and needs extra efficiency

& efforts demanded by the high-end Microcontroller.

Address Size of the Microcontroller. Select a microcontroller, which can support Address

Bus to access optimum memory.

On physical basis:



DIOs available with microcontroller. A microcontroller selected should have equivalent or

adequate pin count, required for Embedded System. This will save the space on final board

of the product.

Flash Memory of the microcontroller. The size Flash memory depends on the size of

object file generated by the assembler/compiler. The size of Flash program memory is an

important factor when the user has decided to use internal program memory.

Internal RAM of the microcontroller. The selected microcontroller for an Embedded

System should have enough internal RAM required for data memory. The coding style or the

way coding plays the most important role, to limit the usage of internal RAM.

Built-in peripherals of the microcontroller. The microcontroller selected has built-in

peripherals needed by Embedded System, like ADC/DAC, UART/USART, USB, SPI, I2C,

Timers.

Operating Temperature Range of microcontroller. A microcontroller selected should

have a temperature range, if Embedded System is designed for Industrial purpose.

Others important factors:

Development & Programming tools available for development related to the

microcontroller. The available Development & Programming tools like, assemblers,

compilers, simulators and debuggers should cost effective, i.e it should not affect the cost of

the product. The availability and cost of development & programming hardware are be

considered while choosing microcontroller.



Availability and Cost of the microcontroller. Select a microcontroller which is easily

available and comparatively cheap.

Last but the most important factor while selecting the microcontroller is the third

party support available. Number of open source developers, experts, entrepreneurs, hobbyist

keep their work and product ideas on internet, which help many developers to start work in

right direction and complete their design in schedule. While selecting a Microcontroller for

Embedded System, one should look for the third party support available the controller.

The following resources are also checked for various requirements:

Internal EEPROM Flash/ROM/EPROM.

Serial synchronous communication full duplex or half.

Serial UART.

Timer 1, 2 or 3.

Watchdog timer none or 1.

Out-compares none or 1 or 2 or 3 or 4 or 5.

Input captures none or 1 or 2 or 3.

PWM none or 1 or 2 or 3 or 4.

Single or multi-channel ADC and is it required with or without programmable voltage

reference and with single or dual reference.

Modem device.

Digital signal processing (DSP) with DSP instructions processing CPU.

Non-linear controller instructions processing CPU.

Ports with the network interface and network processing related instructions processing

CPU.

Ports with wireless interface and related processing instructions capable CPU.

USB/PCI/I2C/CAN/JTAG/SDIO interface devices.

4.1.2 FEATURES OF 89C52 MICROCONTROLLER

This microcontroller has the following features:

8-bit Central Processing Unit.



Powerful Instruction Set.

Compatible with MCS-51 Products.

4Kbytes of In-System Reprogramable Flash Memory.

Endurance: 1,000 Write/Erase Cycles.

Fully Static Operation: 0 Hz to 24 MHz.

Three-Level Program Memory Lock.

128 x 8-bit Internal RAM.

32 Programmable I/O Lines.

Two 16-Bit Timer/Counters.

Six Interrupt Sources.

Programmable Full Duplex Serial Channel.

On-chip Oscillator and Clock Circuit.

Low Power Idle and Power Down Modes.

4.1.3 PIN DESCRIPTION OF 89C52 FAMILY MICRO CONTROLLER:

VCC: - Supply Voltage.

GND: - Ground



Port 0: - Port 0 is an 8-bit open drain bi-directional I/O port. As an output port each pin can

sink eight TTL inputs. When 1s are written to port 0 pins, the pins can be used as high

impedance inputs. Port 0 may 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. Port 0 also receives the code bytes during flash programming, and outputs

the code bytes during program verification. External pull-ups are required during program

verification.

Port 1: - Port 1 is an 8-bit bi-directional I/O port with internal pull-ups. The port1 output

buffers can sink/source four TTL inputs. When 1s are written to port 1 pins, they are pulled

high by the internal pull-ups and can be used as inputs. As inputs, port 1 pins that are

externally being pulled low will source current (IIl) because of the internal pull-ups. Port 1

also receives the low order address bytes during flash programming and program

verification.



Port 2: - Port 2 is an 8-bit bi-directional I/O port with internal pull-ups. The port2 output



externally being pulled low will source current (IIl) because of the internal pull-ups. 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 addresses.

Port 3: - Port 3 is an 8-bit bi-directional I/O port with internal pull-ups. The port 3 output



externally being pulled low will source current (IIl) because of the pull-ups. Port3 also serves

the functions of various special features of the AT89C52 as listed below:

Port Pin Alternate Function

P3.0 RXD (serial input port)

P3.1 TXD (serial output port)

P3.2 /INT0 (external interrupt 0)

P3.3 /INT1 (external interrupt 1)

P3.4 T0 (timer 0 external input)

P3.5 T1 (timer 1 external input)

P3.6 /WR (external data memory write strobe)

P3.7 /RD (external data memory read strobe)

Port 3 also receives some control signals for Flash programming and programming

verification.

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 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. In normal operation ALE is emitted at a constant rate of 1/6the

oscillator frequency, and may be used for external timing or clocking purpose. Note,

however, that one ALE pulse is skipped during each access to external Data Memory. If

desired, ALE operation can be disabled by setting bit 0 of SFR location 8EH. With the bit

set, ALE is active only during a MOVX or MOVC instruction. Otherwise, the pin is weakly

pulled high. Setting the ALE-disable bit has no effect if the microcontroller is in external

execution mode.

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. Note, however that if lock bit 1 is programmed, EA will be internally latched on

reset. EA should be strapped to Vcc for internal program executions. This pin also receives

the 12V programming enable voltage (Vpp) during Flash programming, for parts that require

12V Vpp.

XTAL1: - Input to the inverting oscillator amplifier and input to the internal clock operating

circuit.

XTAL2: - Output from the inverting oscillator amplifier.

4.1.4 RESET CIRCUIT



Once the program has been entered into flash program memory, power supply and

clocks are provided, the microcontroller starts to fetch, decode and execute instructions from

program memory and then onwards the entire behavior of the system depends on the program

alone. Most microcontrollers execute program from a memory location pointed by a special

register called a Program Counter (PC). This Program Counter (PC), like any other register,

can have any random number when power is newly applied to the microcontroller. Hence

program execution can start from any random location, resulting in unpredictable behavior of

the system. RESET is essential for any microcontroller to bring it back into an initial

condition and execute program from a proper staring point.

Manual reset

Some times, if the user wants to stop the system due to any reason, or when needs to

stop system from doing unexpected or un-wanted things, RESET is the only option. In 8051,

RESET is an active High input. When RESET is set to High, 8051 goes back to the power on

state. Closing the push button momentarily will apply Vcc to pin 9 that makes RESET High

causing microcontroller to suspend all its activities. The 8051 is RESET by holding the

RESET pin high for at least two machine cycles and then returning it low. After a RESET,

the Program Counter is loaded with 0000H but the contents of on-chip RAM are not affected.

When the push button is released, pin 9 connects to ground through 8K2 resister and hence

the program execution continues from starting (0000H) location.

Power-On Reset

An embedded system cannot be rebooted manually, because it has been embedded to

its system and in many occasions there are nobody to start the systems designed using

embedded microcontrollers. They have to start functioning themselves. This should happen

each and every time supply has been disrupted and again applied to them as in the case of

mains failure and resumption. Hence embedded systems have to be self booting type, i.e.

they should start functioning as soon as supply is applied to them. They should execute the

program from the beginning (usually from 0000H location) and must be ready to act



according to the program written into their program flash memory, to ensure a fault free

operation.

+5 V VCC__EA

GND

RST

40

31

RESET 9

20

4 7 E

8 K 2

1 0 u

As shown in the circuit diagram, the capacitor (10uF) and the resister (8K2 form a

voltage divider across Vcc and GND. According to KVL,

Vcc=Vc+Vr.

Where Vcc is applied voltage, Vc is voltage across capacitor and Vr is the voltage across

resister.

Initially when supply is applied, voltage across capacitor Vc is zero and hence

Vr=Vcc i.e RESET pin is at logic 1and microcontroller is suspended. As this situation

continues, capacitor gradually charges towards Vcc and hence Vr=0 i.e RESET pin is at logic

0 and microcontroller starts program execution.

4.1.5OSCILLATOR CIRCUIT

The microcontrollers are designed using huge digital circuitry inside. All

microcontrollers need an oscillator clock unit which generates the clock tick at a



predetermined rate. The clock is used to control the clocking requirement of all internal

digital circuitry in the CPU for executing instructions and the configuration of timers.

+5 V31

RESET

XTAL1

RST

19

XTAL2

20

18

VCC

GND

40

9

__EA

MHz

8 K 2

3 3 p f

0 . 1

1 0 u

3 3 p f

4 7 E

11 . 0592

The 8051 uses the crystal to synchronize its operation. Effectively, the 8051 operates

using what are called "machine cycles." A single machine cycle is the minimum amount of

time in which a single 8051 instruction can be executed. Although many instructions take

multiple cycles, a cycle is, in reality, 12 pulses of the crystal. That is to say, if an instruction

takes one machine cycle to execute, it will take 12 pulses of the crystal to execute. For

example, a classic 8051 clock cycle is (1/12) uS because the clock frequency is 12MHz. A

simple 8051 instruction takes 12 cycles (1uS) to complete an instruction cycle. Of course,

some multi-cycle instructions require multiple machine cycles, such as those instructions

with a memory operand which needs multiple memory accesses. An 8051 machine cycle

consists of 12 crystal pulses (clock cycles). The first 6 crystal pulses (clock cycles) is used to

fetch the opcode and the second 6 pulses are used to perform the operation on the operands in

the ALU. This gives an effective machine cycle rate of 1MIPS (Million Instructions Per

Second). The frequency of a crystal oscillator for the 8051 can be up to 48MHz.

8051 has an on-chip oscillator. It needs an external crystal that decides the operating

frequency of the 8051. The crystal is connected to pins 18 and 19 with stabilizing capacitors.

12 MHz (11.0592MHz) crystal is often used and the capacitance ranges from 20pF to 40pF.

Since we know the crystal is pulsing 11,059,200 times per second and that one machine cycle

is 12 pulses, we can calculate how many instruction cycles the 8051 can execute per

second:11,059,000 / 12 = 921,583



If the 8051 based system has to use its serial port, a 11.0592 MHz crystal is often

used because its frequency can be divided to give you exact clock rates for most of the

common baud rates for the UART, especially for the higher speeds (9600, 19200). Despite

the "odd" value, these crystals are readily available and commonly used.

4.2 INFRARED TRANSCEIVER

4.2.1 BASICS OF INFRARED

All infra red devices use some kind of infrared signals. The major components

involved in IR device are Emitter, Detector and LED. These remote controls use pulses of

IR light to transmit the signal to the receiver. The IR Led used here transmits light in the

frequency range of 30 KHz to 40 KHz. This high frequency is chosen so that other light

source would not interfere with the receiver’s ability to correctly receive the transmitted

signal. The signals transmitted by the IR LED are in some type of binary code, which

varies, in both time and bit length. Most consumer electronic devices such as a remote

control use similar binary code.

4.2.2 IR TRANSMITTERS & RECEIVER CIRCUIT DIAGRAM



Fig 4.2.2 Circuit Diagram Of Infrared Transceiver

This is placed at the entrance of the building to sense the arrival of any intruder. It uses

invisible light beam as a barrier and consists of a IR Transmitter and a IR Receiver. IR

Transmitter is placed at one side of the gate and the IR Receiver is placed on the opposite

side. They are placed face to face, so that the IR light falls straight on the receiver. The IR

transmitter transmits an invisible modulated (38 KHz) IR light beam pointing towards the IR

receiver unit. It consists of a 38 KHz oscillator and IR Light Emitting Diode and Sensor

section consists of 3-terminal IR Sensors. These sensors are sensitive to 38 KHz. They

produce TTL compatible signals when a coded IR light beam is incident on them. This signal

is sensed by the microcontroller and used for further processing. The IR receiver is un-

affected by the surrounding natural light. When any person tries to enter the building, he/she,

unknowingly interrupts this invisible light beam. The sensor then sends a signal to the

microcontroller.

4.2.3 555TIMER



To generate a carrier signal of frequency of 38 KHz we used 555 timer in astable

multivibrator mode which is shown bellow

Standard 555 astable circuit

In astable mode, the 555 timer puts out a continuous stream of

rectangular pulses having a specified frequency. Resistor R1is connected between

VCC and the discharge pin (pin 7) and another resistor (R2) is connected between the

discharge pin (pin 7), and the trigger (pin 2) and threshold (pin 6) pins that share a

common node. Hence the capacitor is charged through R1 and R2, and discharged only

through R2, since pin 7 has low impedance to ground during output low intervals of the

cycle, therefore discharging the capacitor.

Particularly with bipolar 555s, low values of must be avoided so that the

output stays saturated near zero volts during discharge, as assumed by the above

equation. Otherwise the output low time will be greater than calculated above. The first

cycle will take appreciably longer than the calculated time, as the capacitor must charge

from 0V to 2/3 of VCC from power-up, but only from 1/3 of VCC to 2/3 of VCC on

subsequent cycles.

To achieve a duty cycle of less than 50% a small diode (that is fast enough for the

application) can be placed in parallel with R2, with the cathode on the capacitor side. This

bypasses R2 during the high part of the cycle so that the high interval depends


http://en.wikipedia.org/wiki/Duty_cycle

http://en.wikipedia.org/wiki/File:555_Astable_Diagram.svg


approximately only on R1 and C. The presence of the diode is a voltage drop that slows

charging on the capacitor so that the high time is longer than the expected and often-cited

ln(2)*R1C = 0.693 R1C. The low time will be the same as without the diode as shown

above. With a diode, the high time is

where Vdiode is when the diode has a current of 1/2 of Vcc/R1 which can be

determined from its datasheet or by testing. As an extreme example, when Vcc= 5 and

Vdiode= 0.7, high time = 1.00 R1C which is 45% longer than the "expected" 0.693 R1C. At

the other extreme, when Vcc= 15 and Vdiode= 0.3, the high time = 0.725 R1C which is

closer to the expected 0.693 R1C. The equation reduces to the expected 0.693 R1C if

Vdiode= 0.

In astable mode, the 555 timer puts out a continuous

stream of rectangular pulses having a specified frequency. Resistor R1is connected

between VCC and the discharge pin (pin 7) and another resistor (R2) is connected between

the discharge pin (pin 7), and the trigger (pin 2) and threshold (pin 6) pins that share a

common node. Hence the capacitor is charged through R1 and R2, and discharged only

through R2, since pin 7 has low impedance to ground during output low intervals of the

cycle, therefore discharging the capacitor.



4.2.4 DESIGN

The frequency, or Repetation rate of the output pulses is determined by the values of two

resistors, R1 and R2 and by the timing capacitor, C.

The design formula for the frequency of the pulses is:

f = 1.44( R1+2 R 2 ) .C

Hz

The period t, of the pulses is given by:

t=1f=0.69 (R 1+2 R 2 )∗C sec

The HIGH and LOW times of each pulse can be calculated from:

high time=0.69∗( R1+R 2 )∗C sec

low time=0.69∗R 2∗C sec

t=high time+low time

In our project we want to design a circuit to produce a frequency of approximately 38kHz,

So the values of R1, R2 and C can be calculated as follows .

Choose C=0.001µF,then

R1+2R2=1.44/(38k×0.001µ)

R1+2R2=37.894 kΩ

Let us Choose R1 as 3 kΩ

Therefore ,

2R2=(37.894-3) kΩ



R2=17.447 kΩ

Hence we have taken an 10 kΩ resister in series with a 10 kΩ potentiometer.

4.2.5 TSOP17XX

The TSOP1738 miniaturized receiver is for infrared remote control systems.

PIN diode and preamplifier are assembled on lead frame, the epoxy package is designed

as IR filter. The demodulated output signal can directly be decoded by a microprocessor.

TSOP1738 is the standard IR remote control receiver, supporting all major transmission

codes.

Figure 4.2.5.1: Physical structure of TSOP1738 IR sensor.

Features:

Photo detector and preamplifier in one package

Internal filter for PCM frequency

Improved shielding against electrical field disturbance

TTL and CMOS compatibility

Output active low



Low power consumption

High immunity against ambient light

Continuous data transmission possible(up to 2400 bps)

Suitable burst length 10 cycles/burst

Figure 4.2.5.2: Block Diagram of TSOP1738 IR Sensor.

Suitable Data Format:

The circuit of the TSOP1738 is designed in that way that unexpected output pulses

due to noise or disturbance signals are avoided. A bandpass filter, an integrator stage

and an automatic gain control are used to suppress such disturbances. The distinguishing

mark between data signal and disturbance signal are carrier frequency, burst length and

duty cycle.

The data signal should fullfill the following condition:

Carrier frequency should be close to center frequency of the bandpass (e.g.

38kHz).

Burst length should be 10 cycles/burst or longer.



After each burst which is between 10 cycles and 70 cycles a gap time of at least 14

cycles is necessary.

For each burst which is longer than 1.8ms a corresponding gap time is

necessary at some time in the data stream. This gap time should have at least same length as

the burst.

Up to 1400 short bursts per second can be received continuously.

Some examples for suitable data format are: NEC Code, Toshiba Micom Format, Sharp

Code, RC5 Code, RC6 Code, R–2000 Code and Sony Format (SIRCS).

When a disturbance signal is applied to the TSOP1738 it can still receive the data signal.

However, the sensitivity is reduced to that level that no unexpected pulses will occur.

Some examples for such disturbance signals which are suppressed by

TSOP1738 are:

DC light (e.g. from tungsten bulb or sunlight)

Continuous signal at 38kHz or at any other frequency

Signals from fluorescent lamps with electronic ballast (an example of the

signal modulation is in figure below).

Available types for different carrier frequencies



4.3 DTMF ENCODER

4.3.1 DUAL TONE MULTIPLE FREQUENCY (DTMF)

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 complete communication

consists of the tone generator and the tone decoder.

A DTMF signal is the algebraic sum of two different audio frequencies, and can be

expressed as follows:

f(t) = A0sin(2*П*fa*t) + B0sin(2*П*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. The

frequencies associated with various keys on the keypad are shown in figure (A).

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.

DTMF stands for Dual Tone Multi Frequency. Redtacton transmitter and receiver

make use of the DTMF. The basic principle of DTMF is when we have to transmit a number,

for example ‘1’ through medium, the column frequency and row frequency of number ‘1’ is

added and it is converted into single frequency signal and transmitted from transmitter to

receiver through medium. At the receiver, spectrum analysis is done to determine the number

which is transmitted. In the spectrum analysis, we will get peaks at the values of row and

column frequencies. By seeing these peaks, we can determine which number is transmitted

from the transmitter.

Fig 4.3.1.1 The row and column frequencies table

When you press the digit 5 in the keypad it generates a resultant tone signal which is

made up of frequencies 770Hz and 1336Hz. Pressing digit 8 will produce the tone taken from

tones 852Hz and 1336Hz. In both the cases, the column frequency 1336 Hz is the same.

These signals are digital signals which are symmetrical with the sinusoidal wave.



Fig 4.3.1.2 A Typical frequency when 1 is pressed

Due to its accuracy and uniqueness, these DTMF signals are used in controlling systems

using telephones. By using some DTMF generating IC’s (UM91214B) we can generate

DTMF tones without depending on the telephone set.



4.3.2 DTMF ENCODER CIRCUIT DIAGRAM

Fig 4.3.2 Circuit diagram of the DTMF encoder

As shown in fig 4.3.2, 12 different push buttons are connected in 4×3 raw column

structure. All four row terminals and three column terminals are connected with raw (R1,

R2, R3 R4) and column (C1, C2, C3) pins of IC.



A 3.59 MHz crystal with two capacitors C1 & C2 is connected to crystal terminals 3

and 4.

A zener diode D1 is connected across the supply terminals of IC 91214B to limit the

supply voltage of chip to 3.3 V. A 330Ω resistor is used to limit the current to zener diode.

This encoder IC requires a voltage of 3V. For that IC is wired around 4.5V battery.

And 3V backup Vcc for this IC is supplied by using 3.2v zener diode.

The row and column frequency of this IC is as on the fig. "4.3.1.1". By pressing the

number 5 in the key pad the output tone is produced which is the resultant of addition of two

frequencies, at pin no. 13 & pin no.16 of the IC and respective tone which represents number

'5' in key pad is produced at pin no.7 of the IC . This signal is sent to the 7W audio amplifier

for amplification to pass through human body.

4.4 DTMF DECODER

Decoder is used to decode the signal transmitted by encoder and to convert it into

binary form. DTMF decoder is used in Redtacton receiver. On the Redtacton receiving side,

it has a decoder circuit to decode the tone to digital code. For example, the tone of 941hz +



1336hz will be decoded as binary '1010' as the output. This digital output will be read in by

the microcontroller to identify the person.

4.4.1 DTMF DECODER CIRCUIT DIAGRAM

Fig 4.4.1 circuit diagram of dtmf decoder

4.4.2 WORKING OF IC CM8870

The CM-8870 is a full DTMF Receiver that integrates both band split filter and decoder

functions into a single 18-pin DIP. 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 3.579545 MHz crystal, a timing resistor, and a timing capacitor. The CM-8870-02

can also inhibit the decoding of fourth column digits.



CM-8870 operating functions include a band split filter that separates the high and

low tones of the received pair, and a digital decoder that verifies both the frequency and

duration of the received tones before passing the resulting 4-bit code to the output bus.

The low and high group tones are separated by applying the dual-tone signal to the

inputs of two 6thorder switched capacitor band pass filters with bandwidths that correspond to

the bands enclosing the low and high group tones.

Fig 4.4.2 Internal Block diagram of IC CM8870

The filter also incorporates notches at 350 and 440 Hz, providing excellent dial tone

rejection. Each filter output is followed by a single-order switched capacitor section that

smoothes the signals prior to limiting. Signal limiting is performed by high gain comparators

provided with hysteresis to prevent detection of unwanted low-level signals and noise. The

CM-8870 decoder uses a digital counting technique to determine the frequencies of the

limited tones and to verify that they correspond to standard DTMF frequencies. When the

detector recognizes the simultaneous presence of two valid tones (known as signal

condition), it raises the Early Steering flag (ESt). Any subsequent loss of signal condition

will cause ESt to fall. Before a decoded tone pair is registered, the receiver checks for valid



signal duration (referred to as character- recognition-condition). This check is performed by

an external RC time constant driven by ESt. A short delay to allow the output latch to settle,

the delayed steering output flag (StD) goes high, signaling that a received tone pair has been

registered. The contents of the output latch are made available on the 4-bit output bus by

raising the three state control input (OE) to logic high. Inhibit mode is enabled by a logic

high input to pin 5 (INH). It inhibits the detection of 1633 Hz.

The output code will remain the same as the previous detected code. On the CM-8870

models, this pin is tied to ground (logic low).The input arrangement of the CM-8870

provides a differential input operational amplifier as well as a bias source (VREF) to bias the

inputs at mid-rail. Provision is made for connection of a feedback resistor to the op-amp

output (GS) for gain adjustment. The internal clock circuit is completed with the addition of a

standard 3.579545 MHz crystal. The input arrangement of the CM-8870 provides a

differential input operational amplifier as well as a bias source (VREF) to bias the inputs at

mid-rail. Provision is made for connection of a feedback resistor to the op-amp output (GS)

for gain adjustment. The internal clock circuit is completed with the addition of a standard

3.579545 MHz crystal.

4.4.3 FEATURES OF DTMF DECODER IC 8870

Low Power Consumption

Adjustable Acquisition and Release Times

Power-down and Inhibit Modes

Inexpensive 3.58 MHz Time Base

Single 5 Volt Power Supply

Dial Tone Suppression

APPLICATIONS OF DTMF DECODER IC 8870

Telephone switch equipment

Remote data entry

Paging systems



Personal computers

Credit card systems

Here we are using OPAMP with feedback resistor to determine the gain. The output of

OPAMP is given to tone filter where the signal gets separated into high group that is column

frequency and low group that is row frequency. The output is fed to zero crossing detector

which verifies the duration and frequency of the received signal. The output of the zero

crossing detector is given to decoder algorithm block which has internally built look up table.

In this block, the value of the received signal is compared with the values in the look up table

and generates the corresponding output. This output is converted into binary form using the

code converter.



4.5 MATRIX KEY BOARD

+5 V

6

P0.0

0

P0.3

7

8X4K7

4

D

B

1

9

P0.2

P0.435

8 A

33F

38

P0.7

P0.6

5

32

C

P0.1

36

37

P0.5

2

39

E

3

34

Fig 4.5 matrix keypad circuit diagram

Keyboards are the most widely used input devices of a Microcontroller based system.

Keyboards allow the user to enter some value into the system. This makes the

Microcontroller based system user friendly. The operator can interact with the system by

entering desired values for systems variables through the keyboard. Thus, interfacing

keyboard may be a very general requirement of a Microcontroller based product design

When large numbers of keys are required in a system, keys are usually organized in a matrix.

They are arranged as rows and columns. The CPU accesses both rows and columns through

ports. Therefore, with two 8-bit ports, an 8 X 8 matrix, consisting of a total 64 keys can be

interfaced.



When a key is pressed, a row and a column make a contact; otherwise there is no

contact between rows and columns. The microcontroller scans the keys continuously, check

whether any key has been pressed by the user and identify which key has been activated and

react according to the definition of that key or a combination of keys.

We have used a 4 X 4 matrix keyboard connected to P0 port. The columns are

connected to lower portion i.e. on P0.0 to P0.3 and the rows are connected to upper portion

i.e. on P0.4 to P0.7. The upper portion, upon which the rows are connected, is configured as

output port and the lower portion, on which the columns are connected, is configured as an

input port. If no key has been pressed, reading the input port will yield 1’s for all columns

since they are all connected to VCC (high) through pull-up resisters. If all the rows are

grounded and a key is pressed, one of the columns will have 0 since the key pressed provides

the path to ground. It is the function of the microcontroller to scan continuously to detect and

identify the key pressed. This is done by the program, written in the microcontroller’s

memory.

4.6 LCD DISPLAY UNIT

A liquid crystal display (LCD) is a low-cost, low-power device capable

of displaying text and images. LCDs are extremely common in embedded

systems, since such systems often do not have video monitors like those that

come with standard desktop systems. LCDs can be found in numerous common

devices like watches, fax and copy machines, and calculators. These LCD

Modules are very common these days, and are quite simple to work with, as all

the logic required to run them is on board.



Thin- Film Transistor LCD Displays Introduction and Operation

In 1968, the first liquid crystal display (LCD) was developed by RCA Laboratories.

Since then, LCDs have been implemented on almost all types of digital devices, from

watches to computer to projection TVs. LCDs operate as a light "valve", blocking light or

allowing it to pass through. An image in an LCD is formed by applying an electric field to

alter the chemical properties of each LCC (Liquid Crystal Cell) in the display in order to

change a pixel's light absorption properties. These LCCs modify the image produced by the

backlight into the screen output requested by the controller. Though the end output may be in

color, the LCCs are monochrome, and the color is added later through a filtering process.

Modern laptop computer displays can produce 65,536 simultaneous colors at a resolution of

800 x 600.

To understand the operation of an LCD, it is easier to trace the path of a light ray

from the backlight to the user. The light source is usually located directly behind the LCD,

and can use either LED or conventional fluorescent technology. From this source, the light

ray will pass through a light polarizer to uniformly polarize the light so it can be acted upon

by the liquid crystal (LC) matrix. The light beam will then pass through the LC matrix, which

will determine whether this pixel should be "on" or "off". If the pixel is "on", the liquid

crystal cell is electrically activated, and the molecules in the liquid will align in a single

direction. This will allow the light to pass through unchanged. If the pixel is "off", the

electric field is removed from the liquid, and the molecules will scatter. This dramatically

reduces the light that will pass through the display at that pixel.



In a color display, after the light passes through the liquid crystal matrix, it passes

through a color filter (usually glass). This filter blocks all wavelengths of light except those

within the range of that pixel. In a typical RGB display, the color filter is integrated into the

upper glass colored microscopically to render each individual pixel either red, green or blue.

The areas in between the colored pixel filter areas are printed black to increase contrast. After

a beam of light passes through the color filter, it passes through yet another polarizer to

sharpen the image and eliminate glare. The image is then available for viewing.

LCD OPERATION

In recent years the LCD is finding widespread use replacing seven segment LEDs or

other multi segment LEDs. The 2 line X 16 character LCD modules are available from a

wide range of manufacturers and should all be compatible with the HD44780. When viewed

from the front, the left pin is pin 16 and the right pin is pin 1.

The widespread use of the LCDs is due to the 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 a few characters.

3. Incorporation of a refreshing controller into the LCD, there by relieving the CPU of

the task of refreshing the LCD. In contrast, the LED must be refreshed by the CPU

(or in some other way) to keep displaying the data.

4. Ease of programming for characters and graphics.



4.7 GEARED DC MOTORS

A DC motor is an electric motor that uses electricity and a magnetic field to produce

torque, which turns the DC motor. A DC motor consists of two magnets of opposite polarity

and an electric coil. When a power supply is added to the coil electric current flows through

in a circuit and generates a small magnetic field. The repellent and attractive electromagnetic

forces of the magnets provide the torque that causes the armature to turn.

4.7.1 DC MOTOR WORKING

Magnets are polarized, with a positive and a negative side. A DC motor uses the

attraction between opposite poles and the repulsion of like poles to convert electric energy

into kinetic energy. As the magnets within the DC motor attract and repel one another, the

motor turns. The magnetic force on the armature works perpendicular to both wire and

magnetic field. An electric switch called a commutator reverses the direction of the electric

current in the armature twice every cycle. The poles of the electromagnet push and pull

against the permanent magnets on the outside of the motor. As the poles of the armature

electromagnet pass the poles of the permanent magnets, the commutator reverses the polarity

of the armature electromagnet. During that instant of switching polarity, inertia keeps the

motor going in the proper direction. In any electric motor, operation is based on simple

electromagnetism. A current-carrying conductor generates a magnetic field when this is then

placed in an external magnetic field, it will experience a force proportional to the current in

the conductor, and to the strength of the external magnetic field. As everyone is aware,

opposite (North and South) polarities attract, while like polarities (North and North, South

and South) repel. The internal configuration of a DC motor is designed to harness the

magnetic interaction between a current-carrying conductor and an external magnetic field to

generate rotational motion.

Motors come in many sizes and types, but their basic function is the same. Motors of

all types serve to convert electrical energy into mechanical energy. They can be found in

VCR's, elevators, CD players, toys, robots, watches, automobiles, subway trains, fans, space

ships, air conditioners, refrigerators, and many other places. D.C. motors are motors that run


http://encyclobeamia.solarbotics.net/articles/current.html

http://encyclobeamia.solarbotics.net/articles/dc.html




on Direct Current from a battery or D.C. power supply. Direct Current is the term used to

describe electricity at a constant voltage. A.C. motors run on Alternating Current, which

oscillates with a fixed cycle between a positive and negative value. Electrical outlets provide

A.C. power. When a battery or D.C. power supply is connected between a D.C. motor's

electrical leads, the motor converts electrical energy to mechanical work as the output shaft

turns.” The electric motor is the most convenient of all sources of motive power. It is clean

and silent, starts instantly, and can be built large enough to drive the world's fastest trains or

small enough to work a watch."

4.7.2 MOTOR DRIVE H-BRIDGE CIRCUIT

H-bridge, sometimes called a "full bridge" the H-bridge is so named because it has

four switching elements at the "corners" of the H and the motor forms the cross bar. They are

the bane of many robotics hobbyists. H-bridges for controlling brushed DC motors the most

common kind found in hobby robotics. Of course the letter H doesn't have the top and bottom

joined together. The four switching elements within the bridge are often called, high side left,

high side right, low side right, and low side left. The switches are turned on in pairs, either

high left and lower right or lower left and high right, but never both switches on the same

side of the bridge. If both switches on one side of a bridge are turned on it creates a short

circuit between the battery plus and battery minus terminals, this phenomenon is called shoot



through in the Switch-Mode Power Supply (SMPS). If the bridge is sufficiently powerful it

will absorb that load and your batteries will simply drain quickly.

A very popular circuit for driving geared DC motors is an H-bridge circuit. The great

ability of an H-bridge circuit is that the motor can be driven forward or backward at any

speed, optionally using a completely independent power source. An H-bridge design can be

really simple for prototyping or really extravagant for added protection and isolation. An H-

bridge can be implemented with various kinds of components common bipolar transistors,

FET transistors, MOSFET transistors, power MOSFETs, or even chips. Pull-up resistors that

prevent unwanted motor movement while the microcontroller powers up or powers down.

Normally four transistors are needed in an H-bridge. Each transistor forms a corner in

the letter 'H', with the motor being the bar in the middle. each output of the chip forms a

complete vertical side of the letter 'H', with the motor still being in the middle. Because a side

is now a single output, short-circuits can't form from the top of a side to the bottom of a side.

No matter what the inputs, all power must travel from one side to the other through the

motor. Using the microcontroller the commands are sent to turn the inputs on and off

4.7.3 L293D DUAL H-BRIDGE MOTOR DRIVER

It works on the concept of H-bridge. H-bridge is a circuit which allows the voltage to

be flown in either direction. As you know voltage need to change its direction for being able

to rotate the motor in clockwise or anticlockwise direction, Hence H-bridge IC are ideal for

driving a DC motor.

In a single l293d chip there two h-Bridge circuit inside the IC which can rotate two dc

motor independently. Due its size it is very much used in robotic application for controlling

DC motors.

The microcontroller output is not sufficient to drive the DC motors, so current drivers

are required for motor rotation. The L293D is a quad, high-current, half-H driver designed to

provide bidirectional drive currents of up to 600 mA at voltages from 4.5V to 36V. It makes

it easier to drive the DC motors. The L293D consists of four drivers. Pin IN1 through IN4



and OUT1 through OUT4 are input and output pins, respectively, of driver 1 through driver

4. Drivers 1 and 2, and drivers 3 and 4 are enabled by enable pin 1 (EN1) and pin 9 (EN2),

respectively. When enable input EN1 (pin 1) is high, drivers 1 and 2 are enabled and the

outputs corresponding to their inputs are active. Similarly, enable input EN2 (pin 9) enables

drivers 3 and 4.

The L293D is an integrated circuit motor driver that can be used for simultaneous,

bidirectional control of two small motors as shown fig below output current of 1.2A per

channel. Moreover for protection of circuit from back EMF output diodes are included within

the IC. The output supply (VCC2) has a wide range from 4.5V to 36V, which has made

L293D a best choice for DC motor driver. As seen in the circuit, three pins are needed for

interfacing a DC motor (A, B, Enable). As we want the o/p to be enabled completely so we

have connected Enable to VCC and only 2 pins are needed from controller to make the motor

work.

L293D is a dual H-Bridge motor driver, So with one IC we can interface two DC

motors which can be controlled in both clockwise and counter clockwise direction and if you

have motor with fix direction of motion the you can make use of all the four I/Os to connect

up to four DC motors. L293D has output current of 600mA and peak output current of 1.2A

per channel. Moreover for protection of circuit from back EMF output diodes are included

within the IC. The output supply (VCC2) has a wide range from 4.5V to 36V, which has



made L293D a best choice for DC motor driver. A simple schematic for interfacing a DC

motor using L293D is shown below.

As we can see in the circuit, three pins are needed for interfacing a DC motor (A, B,

Enable). If you want the o/p to be enabled continuously Enable pin can be connected to VCC

and only 2 pins are needed from microcontroller to make the motor work. As per the truth

table mentioned in the image above its fairly simple to program the microcontroller. Its also

clear from the truth table of BJT circuit and L293D the programming will be same for both

of them, just keeping in mind the allowed combinations of A and B.

+5 V+9 V

10

OUT1

6

28

9

L293D

IN1

OUT4

7

IN4

5

EN2 VCC3

12

11

P0.2

P0.3

EN1

27

1

IN3

16

IN2

25

P0.1

13

26 OUT3

14

2

15

VS

OUT2

P0.0

8

4

DC

M

OT

OR

M

3D

C M

OT

OR

M

4

Circuit diagram of H-Bridge



High Side

Right

Lower

Left

Lower

Right Quadrant Description

On Off Off On Motor goes Clockwise

Off On On Off Motor goes Counter-clockwise

On On Off Off Motor "brakes" and decelerates

Off Off On On Motor "brakes" and decelerates

4.8 GLOBAL SYSTEM FOR MOBILE COMMUNICATIONS

(GSM)

The Global System for Mobile Communication (GSM) is the most popular standard

for mobile phones in the world. Over 2 billion people use GSM service across more than 212

countries and territories. The ubiquity of the GSM standard makes international roaming

very common between mobile phone operators, enabling subscribers to use their phones in

many parts of the world. GSM differs significantly from its predecessors in that both

signaling and speech channels are digital, which means that it is considered a second

generation (2G) mobile phone system. This fact has also meant that data communication was

built into the system from very early on. GSM is an open standard which is currently

developed the 3GPP.

4.8.1 THE STRUCTURE OF GSM NETWORK

The network behind the GSM system seen by the customer is large and complicated in

order to provide all of the services, which are required. It is divided into a number of sections

and these are each covered in separate articles.

The Base Station Subsystem (the base stations and their controllers).



The Network and Switching Subsystem (the part of the network most similar to a

fixed network). This is sometimes also just called the core network.

The GPRS Core Network (the optional part which allows packet based internet

connection).

All of the elements in the system combine to produce many GSM services such as

voice calls and SMS.



4.8.2 SUBSCRIBER IDENTITY MODULE

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 information

after switching handsets. Alternatively, the user can also change operators while retaining

the handset simply by changing the SIM.

4.8.3 MOBILE STATION

The mobile station (MS) consists of the mobile equipment (the terminal) and a smart card

called the Subscriber Identity Module (SIM). The SIM provides personal mobility, so

that the user can have access to subscribed services irrespective of a specific terminal. By

inserting the SIM card into another GSM terminal, the user is able to receive calls at that

terminal, make calls from that terminal, and receive other subscribed services. The mobile

equipment is uniquely identified by International Mobile Equipment Identity (IMEI). The

SIM card contains the International Mobile Subscriber Identity (IMSI) used to identify the

subscriber to the system, secret key for authentication, and other information. The IMEI

and the IMSI are independent, thereby allowing personal mobility. The SIM card may be

protected against unauthorized use by a password or personal identity number.

4.8.4 BASE STATION SUBSYSTEM

The Base Station Subsystem is composed of two parts, the Base Transceiver Station

(BTS) and the Base Station Controller (BSC). These communicate across the

standardized Abis interface, allowing (as in the rest of the system) operation between

components made by different suppliers. The Base Transceiver Station houses the radio

transceivers that define a cell and handles the radio-link protocols with the Mobile

Station. In a large urban area, there will potentially be a large number of BTSs deployed,

thus the requirements for a BTS are ruggedness, reliability, portability, and minimum

cost. The Base Station Controller manages the radio resources for one or more BTSs. It

handles radio-channel setup, frequency hopping, and handovers, as described below. The

BSC is the connection between the mobile station and the Mobile Switching Service.



4.8.5 NETWORK SUBSYSTEM

The central component of the Network Subsystem is the Mobile services Switching

Center (MSC). It acts like a normal switching node of the PSTN or ISDN, and

additionally provides all the functionality needed to handle a mobile subscriber, such as

registration, authentication, location updating, handovers, and call routing to a roaming

subscriber. These services are provided in conjunction with several functional entities

which together form the Network Subsystem. The MSC provides the connection to the

fixed networks (such as the PSTN or ISDN). Signaling between functional entities in the

Network Subsystem uses Signaling System Number 7(SS7), used for trunk signaling in

ISDN and widely used in current public networks Messaging Center (MSC).

4.8.6 SHORT MESSAGE SERVICE (SMS)

is popular among mobile phone users as a cheap and convenient method of

communicating. Therefore, SMS technology is a common feature with all mobile

network service providers. They provide many information and services via SMS such as

latest news updates, stock information, and various entertaining applications stuffs. Some

common examples are

1. Send and receive confidential information of bank accounts,

2. Enhance security in households and vehicles,

3. Monitoring physical quantities remotely,

4. Transfer data between remote locations,

5. Alerting method, and

6. Information distributing system and many more...

In order to use SMS for various applications it is necessary to understand their data

communication methods and protocols since several unnecessary information needed to be

filtered out. Filtering and manipulating hardware assistance is very important and this could

be performed using a microcontroller. Since the use of SMS technology is a cheap,

convenient and flexible way of conveying data, researchers are trying to apply this

technology in many different areas that were not provided by service providers at present.



One of such areas that the SMS technology could be used as a cost effective and more

flexible way will be remote monitoring and controlling.

4.8.7 GSM MODEMs

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

wireless modem behaves like a dial-up modem. The main difference between them is that a

dial-up modem sends and receives data through a fixed telephone line while a wireless

modem sends and receives data through radio waves.

A GSM modem can be an external device or a PC Card / PCMCIA Card. Typically,

an external GSM modem is connected to a computer through a serial cable or a USB cable. A

GSM modem in the form of a PC Card / PCMCIA Card is designed for use with a laptop

computer. It should be inserted into one of the PC Card / PCMCIA Card slots of a laptop

computer.Like a GSM mobile phone, a GSM modem requires a SIM card from a wireless

carrier in order to operate.Computers use AT commands to control modems. Both GSM

modems and dial-up modems support a common set of standard AT commands. You can use

a GSM modem just like a dial-up modem.

In addition to the standard AT commands, GSM modems support an extended set of

AT commands. These extended AT commands are defined in the GSM standards.

With the extended AT commands, you can do things like:

Reading, writing and deleting SMS messages.

Sending SMS messages.

Monitoring the signal strength.

Monitoring the charging status and charge level of the battery.

Reading, writing and searching phone book entries.

The number of SMS messages that can be processed by a GSM modem per minute is

very low ie: only about six to ten SMS messages per minute. A dedicated GSM modem

(external or PC Card) is usually preferable to a GSM mobile phone. This is because of some

compatibility issues that can exist with mobile phones. For example, if you wish to be able to

receive inbound MMS messages with your gateway, and you are using a mobile phone as



your modem, you must utilize a mobile phone that does not support WAP push or MMS. This

is because the mobile phone automatically processes these messages, without forwarding

them via the modem interface. Similarly some mobile phones will not allow you to correctly

receive SMS text messages longer than 160 bytes (known as "concatenated SMS" or "long

SMS"). This is because these long messages are actually sent as separate SMS messages, and

the phone attempts to reassemble the message before forwarding via the modem interface.

(We've observed this latter problem utilizing the Ericsson R380, while it does not appear to

be a problem with many other Ericsson models.) When you install your GSM modem, or

connect your GSM mobile phone to the computer, be sure to install the appropriate Windows

modem driver from the device manufacturer. To simplify configuration, the Now SMS/MMS

Gateway will communicate with the device via this driver. An additional benefit of utilizing

this driver is that you can use Windows diagnostics to ensure that the modem is

communicating properly with the computer.



4.8.8 CHARACTERISTICS:

Dual Band or Tri-band GSM modem (EGSM 900/1800MHz) / (EGSM 900/1800

1900 MHz ).

Designed for GPRS, data, fax, SMS and voice applications.

Input voltage: 8V-40V.

Input current: 8mA in idle mode, 150mA in communication GSM 900 @ 12V.

Input current: 8mA in idle mode, 110mA in communication GSM 1800 @ 12V.

Temperature range: Operating -20 to +55 degree Celsius; Storage -25 to +70 degree

Celsius.

Overall dimensions: 80mm x 62mm x 31mm.

Weight: 200g.



4.9 BUZZER AND DRIVE CIRCUIT

+5 V

BUZZER

21P2.0

BC 5474K7

L E D

6 8 0 E

Fig 4.9.1 CIRCUIT DIAGRAM OF BUZZER AND DRIVE CIRCUIT

When any abnormality is sensed by the microcontroller through the door sensors, an

audio tone produced by a buzzer. The microcontroller controls the sound produced by buzzer

through a drive transistor. The buzzer driver consists of a npn transistor operated in ce

configuration. It supplies current to the buzzer element connected in its collector. The

microcontroller sends ttl level signals, a logic ‘1’ to turn on the buzzer and a logic ‘0’ to turn

it off. Buzzer is a component producing sound of alarm and electronic sound. Ex) security

buzzer, fire-alarm device and alarm clock etc. Buzzer plays an important part as a man-

machine interface.

Buzzer is a component producing sound of alarm and electronic sound. Security

buzzer, fire-alarm device and alarm clock etc. Buzzer plays an important part as a man-made

machine interface. A buzzer or beeper is an audio signaling device, which may be

mechanical, electromechanical, or piezoelectric. Piezo buzzer is based on the inverse

principle of piezo electricity discovered in 1880 by Jacques and Pierre Curie. It is the

phenomena of generating electricity when mechanical pressure is applied to certain materials

and the vice versa is also true. Such materials are called piezo electric materials. Piezo

electric materials are either naturally available or manmade. Piezoceramic is class of

manmade material, which poses piezo electric effect and is widely used to make disc, the

heart of piezo buzzer. When subjected to an alternating electric field they stretch or

compress, in accordance with the frequency of the signal thereby producing sound.



4.10 POWER SUPPLY

4.10.1 INTRODUCTION

Power supply is an essential part, of every, electronic equipment. Since the healthy

functioning of all stages in an equipment requires a well-designed power supply. A great

many factors, like voltages required, current rating, power drawn and the percent of

regulation permitted etc, influence the design of particular power supply. Existing power

supplies may be too big in power output or physical size Generally, since the various voltages

required, at various points of an equipment, are already known, the kind of power supply used

in an instrument is of fixed voltage type,. However in some rare cases, a facility to vary the

supply voltage may be required. In general, the power supply section should be capable of

providing higher load as well as line regulation, along with the mains isolation.

For most non-critical applications the best and simplest choice for a voltage regulator

is the 3-terminal type. The 3 terminals are input, ground and output. The 78XX & 79XX

series can provide up to 1A load current and it have on-chip circuitry to prevent damage in the

event of over heating or excessive current. That is, the chip simply shuts down rather than

blowing out. These regulators are inexpensive, easy to use, and they make it practical to

design a system with many PCBs in which an unregulated supply is brought in and regulation

is done locally on each circuit board.

Fig 4.10.1.1 Block diagram of 5V regulated power supply



Fig 4.10.1.2 circuit diagram of regulated 5V power supply

The working principle and the design details of the power supply unit, capable of supplying

various voltages, at 1A current rating is shown in the circuit diagram. It comprises of the

following sections.

1. Transformer

2. Rectifiers

3. Filters

4. Regulators

4.10.2TRANSFORMER

A step-down type transformer is used to reduce the mains voltages to a suitable low

voltage. It is a device, which transforms the 230 volts 50 Hz, A.C mains voltage, to required

small voltages. Ordinary shell type transformer, made of silicon steel cores, having a current

rating of 1A is used. The transformer primary is connected to mains AC through ON/OFF



switch and a fuse. This transformer, along with reducing mains voltage to a required small

voltage, also provides isolation from mains, to avoid any electrical shock to the operator.

Our design uses a full wave bridge rectifier with a center-tapped transformer, to obtain

dual-tracking voltages i.e., to get +Ve and –Ve voltages with respect to ground. a transformer

with a power output rated at at-lest 15 VA should be used. If the transformer is rated by

output RMS-current then the value should be divided by 1.2 to get the current, which can be

supplied. For example, in this case a 1A RMS can deliver 1/(1.2) or 830 mA. The transformer

is mounted outside the main PCB since it is bulky and also to avoid hum.

4.10.3RECTIFIER

The rectifier is built using power diodes. For the maximum efficiency and low ripple, a full

wave or a bridge configuration is always preferred. The diodes chosen should have a peak

inverse voltage of at-least 200 volts. For safety, the diode voltage rating should be at-least 3

to 4 times that of the transformer secondary voltage. The current rating of the diodes should

be twice the maximum load current.

If a single polarity regulated voltage is required, i.e., either +Ve or –Ve, two diodes

are connected to the top and bottom of secondary terminals of the transformer. For a +Ve

output power supply, the anodes of diodes are connected towards the secondary, & the

cathodes of both diodes are shorted together, to supply +Ve rectified D.C. For a -Ve output

power supply, the cathodes of diodes are connected towards the secondary, & the anodes of

both diodes are shorted together, to supply -Ve rectified D.C. The center tap terminal is

connected to the ground rail.

If a dual tracking regulated voltage is required, i.e., both +Ve & -Ve voltages are

required, two diodes are connected to the top and bottom of secondary terminals, with their

anodes towards secondary and both cathodes shorted to supply +Ve rectified D.C & to more

diodes connected in opposite direction to supply –Ve rectified D.C .The center tap terminal is

again connected to the ground rail.

4.10.4 FILTER



The output of the diode bridge is a DC consisting of ripples also called as pulsating DC. This

pulsating DC can be filtered using an inductor filter or a capacitor filter or a resistor-

capacitor-coupled filter for removing the ripples. Consider a capacitor filter which is

frequently used in most cases for smoothing.

We know that a capacitor is an energy storing element. In the circuit capacitor stores

energy when the input increases from zero to a peak value and when the supply voltage

decreases from peak value to zero, capacitor starts discharging. This charging and

discharging of the capacitor will make the pulsating DC into pure DC, as shown in figure.

Capacitors :

Knowledge of Ripple factor is essential while designing the values of capacitors

It is given by

γ=1/(4√3fRC) (as the capacitor filter is used)

1. f= frequency of AC ( 50 Hz)

2. R=resistance calculated

R= V/Ic

V= secondary voltage of transformer

V=12√2=16. 97v

R=16.97/1A=16.9Ω standard 18Ω chosen

3. C= filtering capacitance

We have to determine this capacitance for filtering

γ=Vac-rms/Vdc

Vac-rms = √3*Vr/2

Vdc= VMax-(Vr/2)

Vr= VMax- VMin



Vr = 5.2-4.8 =0. 4V

Vac-rms = 0.3464V

Vdc = 5V

γ=0 .06928

Hence the capacitor value is found out by substituting the ripple factor in γ =1/(4√3fRC)

Thus, C= 2314 µF and standard 2200µF is chosen

Datasheet of 7805 prescribes to use a 0.1μF capacitor at the output side to

avoid transient changes in the voltages due to changes in load and a 22μF at the output side

of regulator to avoid ripples if the filtering is far away from regulator.

4.10.5 REGULATOR

There are many designs possible for a voltage regulator. Many conventional regulators are

best suited for constant voltage supply, but the number of discrete components and circuit

design makes it not much an attractive choice, especially for the dual tracking type power

supplies. Fixed voltage regulator, which are very much efficient, compact and economic are

available as three terminal regulator chips. These chips needs no external components and

provide up to 1A current and operate well, even under worst situations of line, load and

temperature. The 78XX series, are the positive fixed voltage regulators, with its output

voltage specified by the last two digits. Similarly the 79XX series are the negative fixed

voltage regulators

CHAPTR 5



SOFTWARE DESCRIPTION

In any embedded systems application development life cycle one has to adopt one of

the finest hierarchical approach. This approach directly influences the development

productivity. Because of one is dealing with both hardware and software and vast

comprehensibility the development process is very complex.

The developers JOB becomes easy when necessary soft wares to carry out many

phases of development. This is given in the line diagram.

IDE

GVI application Cross compiler Assembler Simulator

Debugger Linker Loader

Fig: 5.1 classification of integrated development environment (ide)



Integrated Development Environment is the first necessity. The IDE is user friendly

software in which one can write the program and see its out come. The IDE will be equipped

with many other tools. In this application Keil micro vision 2 IDE has been used.

5.1 CROSS COMPILER:

This tool is required to build the if user adopts high level language for his application

development. Cross compiler converts source code into the instructions of the target

controller.

The output of the cross compiler given to an assembler. Since it is the programmers

choice to go to high level languages Keil offers C51 as the cross compiler it compiles only

Embedded C code not other like Embedded C++ and Embedded Java.

5.2 ASSEMBLER:

This tool takes instructions and converts into operation code of the target controller.

This process is quite lengthy and carried out phase by phase. Assembler is the combination of

debugger, linker and loader. In Keil we have A51 assembler to build our assembly language

code.

5.3 DEBUGGER:

As its name itself indicates it is for fixing the bugs that is all syntax errors from the

code. Once the code is free from bugs it will be passed to liker.

5.4 LINKER:

Linking operations like attaching starting address of a subroutine to the main

program will be done by liker. It creates an absolute sequential code which is to be executed.

5.5 LOADER:



It simply takes liked file and converts into hex code which can be downloaded into

the micro controller.

All debugger, liker and loader are the part of assembler software.

5.6 SIMULATOR:

Once the code is ready then it is always not a good idea to dump into micro

controller. First it has to be tested in our IDE itself. The tool provided by an IDE which

shows an exact replica of micro controllers perception is nothing but our simulator.

CHAPTER 6



ADVANTAGES AND DISADVANTAGES

ADVANTAGES

No current flows through the human body.

Our project uses the electric field to be transferred on the surface of the human body

for communication. Transmitter and receiver electrodes are covered with an

insulating film. So no current flows into the body from the DTMF transmitter.

Displacement current occurring in the body is small enough to transmit data.

There is no current flowing from the DTMF transmitter however, the body

indirectly receives a minute electric field. This causes electrons already present inside

the body to move, creating a minute displacement current.

Duplex data transfer, synchronization with user behavior, transfer speed- these

are excellent in the case of our project.

DISADVANTAGES

It's too Costly to implement in real time.

CHAPTER 7



APPLICATIONS

Useful in commercial banks, to prevent the unauthorized entry of the person.

As a security system.

For authentication and control systems in vehicles.



CHAPTER 8

CONCLUSION

In “DTMF based security for ATMs and sms alerting system “, there is no need to

insert the ATM card into the ATM machine. Just we have to keep the ATM card in our

pocket, the data present the magnetic stripe will be transmitted through the human body.

Since the data is transmitted via the human body, it is not possible for the hackers to

collect the unique information present in DTMF ATM card. So if we implement this method

in real ATM centres, hacking will be reduced to a large extent.

REFERENCESDEPARTMENT OF ELECTRONICS & COMMUNICATION ENGINEERING,PDACEG


[1]. Bhawik Kotadia , Vibhor Agrawal, “RedTacton”, IEEE

[2]. Reena Antil, Pinki, Mrs. Sonal Beniwal, “Red Tacton : A Review” International Journal

of Scientific & Engineering Research, Volume 4, Issue3, March,2013.

[3]. Siu-Cheng, Charles Chang, “Overview of smart card security”, 1997

[4]. J.E Flood ,Telecommunication switching, Traffic and networks

[5]. Mazidi, The 8051 microcontroller and embedded system 980


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