Transformer Indication system

8/12/2019 Transformer Indication system

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INTRODUCTION

In search of our project we plan to do something, which is yet to be established and must be

useful to day to day life. We analyzed the current situation and realized that if there may be

system that informs the user about various faults in the transformer, we will be able to prevent

severe damages. So we decided to develop such a system that detects transformer faults. A

system which can detect the voltage of a transformer from normal to abnormal and takes

initiatives to avoid damage to a transformer is designed and implemented.

Power transformers are designed to transmit and distribute electrical power. Depending on the

size of a transformer, replacement costs can range from a few hundred dollars to millions of

dollars. Performing offline and invasive tests also add to the replacement cost. Hence, there is an

increasing need to move from traditional schedule-based maintenance programs to condition-

based maintenance. However, a focused approach is required for diagnostics.


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BLOCK DIAGRAM

MICRO

CONTROLLER

POWERSUPPLY

2X16 LCD DISPLAY

CURRENT

SENSOR MAX232GSM

MODEM

OPTO

COUPLER

VOLTAGE

SENSOR

TEMPRATURE

SENSOR

DC

MOTOR


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BLOCK DIAGRAM DESCRIPTION:

HARDWARE DETAILS

Power supply Microcontroller

Current Sensor

LCD Display

Voltage Sensor

Transformer

GSM Modem

DC Motor with Driver

Temperature Sensor

SOFTWARE DETAILS

Embedded C language

AVR OSP

Code Vision AVR


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TRANSFORMER

INTRODUCTION

The protection system of transformer is inevitable due to the voltage fluctuation, frequent

insulation failure, earth fault, over current etc. Thus the following automatic protection systems

are incorporated.

1. Buchholz devices:A Buchholz relay, also called a gas relay or a sudden pressure relay, is a safety

device mounted on some oil-filled power transformers and reactors, equipped with an

external overhead oil reservoir called a conservator. The Buchholz Relay is used as a

protective device sensitive to the effects of dielectric failure inside the equipment. Italso provides protection against all kind of slowly developed faults such as insulation

failure of winding, core heating and fall of oil level.

2. Earth fault relays:An earth fault usually involves a partial breakdown of winding insulation to earth.

The resulting leakage current is considerably less than the short circuit current. The

earth fault may continue for a long time and creates damage before it ultimately

develops into a short circuit and removed from the system. Usually provides

protection against earth fault only.

3. Over current relays:An over current relay, also called as overload relay have high current setting and

are arranged to operate against faults between phases. Usually provides protection

against phase -to-phase faults and overloading faults.

4. Differential system:Differential system, also called as circulating-current system provides protection

against short-circuits between turns of a winding and between windings that

correspond to phase-to-phase or three phase type short-circuits i.e. it provides

protection against earth and phase faults.


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TRANSFORMERDEFINITION

A device used to transfer electric energy from one circuit to another, especially a pair of

multiple wound, inductively coupled wire coils that affect such a transfer with a change in

voltage, current, phase, or other electric characteristic.

Fig 2.1 Basic Transformer


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THE UNIVERSAL EMF EQUATION

If the flux in the core is sinusoidal, the relationship for either winding between its

number of turns, voltage, magnetic flux density and core cross-sectional area is given by

the universal emf equation (from Faradays Law):

E is the sinusoidal rms or root mean square voltage of the winding,

f is the frequency in hertz,

N is the number of turns of wire on the winding,

a is the cross-sectional area of the core in square meters

B is the peak magnetic flux density in Tesla

P is the power in volt amperes or watts,

NECESSITY FOR PROTECTION

Transformers are static devices, totally enclosed and generally oil immersed. Therefore,

chances of faults occurring on them are very rare. However, the consequences of even a rarefault may be very serious unless the transformer is quickly disconnected from the system. This

necessitates providing adequate automatic protection for transformers against possible faults.

COMMON TRANSFORMER FAULTS

As compared with generators, in which many abnormal conditions may arise, power

transformers may suffer only from:

1.

Open circuits

2. Overheating

3. Winding short-circuits


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Open circuit Faults:

An open circuit in one phase of a 3-phase transformer may cause undesirable heating. In

practice, relay protection is not provided against open circuits because this condition is relatively

harmless. On the occurrence of such a fault, the transformer can be disconnected manually from

the system.

Overheating Faults:

Overheating of the transformer is usually caused by sustained overloads or short circuits

and very occasionally by the failure of the cooling system. The relay protection is also not

provided against this contingency and thermal accessories are generally used to sound an alarm

or control the banks of fans.

Winding Short-circuit Faults:

Winding short-circuits (also called internal faults) on the transformer arise from

deterioration of winding insulation due to overheating or mechanical injury. When an internal

fault occurs, the transformer must be disconnected quickly from the system because a prolonged

arc in the transformer may cause oil fire. Therefore, relay protection is absolutely necessary for

internal faults.


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1.2 EMBEDDED SYSTEM

Embedded systems are controllers with on chip control which consist of microcontrollers,

input and output devices, memories etc. and it can be used for a specific application. A small

computer designed in a single chip is called single chip microcomputer. A single chip

microcomputer typically includes a microprocessor, RAM, ROM, timer, interrupt and peripheral

controller in a single chip. This single chip microcomputer is also called as a microcontroller.

These microcontrollers are used for variety of applications where it replaced the computer. The

usage of this microcomputer for specific applications, in which the microcontroller a part of

application is called, embedded systems.

Computing systems are everywhere. Its probably no surprise that millions of computing

systems are built every year destined for desktop computers (Personal Computers, or PCs),

workstations, mainframes and servers. Thus an embedded system is nearly any computing

system other than a desktop, laptop, or mainframe computer.

1.3 CHARACTERISTICS OF AN EMBEDDED SYSTEM

1.3.1 SINGLE-FUNCTIONED

An embedded system usually executes only one program, repeatedly. For example, a

pager is always a pager. In contrast, a desktop system executes a variety of programs, like

spreadsheets, word processors, and video games, with new programs added frequently.

1.3.2 TIGHTLY CONSTRAINED

All computing systems have constraints on design metrics, but those on embedded

systems can be especially tight. A design metric is a measure of an implementations features,

such as cost, size, performance, and power. Embedded systems often must cost just a few dollars,

must be sized to fit on a single chip, must perform fast enough to process data in real-time, and

must consume minimum power to extend battery life or prevent the necessity of a cooling fan.


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13.3 REACTIVE AND REAL-TIME

Many embedded systems must continually react to changes in the systems environment,

and must compute certain results in real time without delay. For example, a car's cruise controller

continually monitors and reacts to speed and brake sensors. It must compute acceleration or

decelerations amounts repeatedly within a limited time; a delayed computation result could result

in a failure to maintain control of the car.

1.4. EMBEDDED PROCESSOR TECHNOLOGY

1.4.1 STANDARD GENERAL PURPOSE PROCESSORS (SGPP)

Standard general purpose processors (SGPP) are carefully designed and offer a

maximum of flexibility to the designer. Programming SGPPs can be done in nearly every high-

level language or assembly language and requires very little knowledge of the system

architecture. As SGPPs are manufactured to high numbers, NRE is spread upon many units.

Nevertheless SGPPs are more expensive than other solutions like FPGAs or single purpose

processors, when used in products with a large number of selling units. These devices are

produced to work in a broad range of environments since those are not designed to be energy

efficient nor high-performance for specific applications.

Examples for standard general purpose processors are:

Motorola ARM

Atmel AVR

Microchip PIC

Intel Pentium-(I/II/III/IV)-Series


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1.4.2. STANDARD SINGLE PURPOSE PROCESSORS (SSPP)

Standard single purpose processors, sometimes called peripherals, are off-the-shelf pre-

designed processors, optimized for a single task, such as digital signal processing, analog to

digital conversion, timing, etc. SSPPs are manufactured in high quantities, so NRE is spread

upon many units. The total costs per SSPP unit are lower than for custom single purpose

processors.

1.4.3. CUSTOM SINGLE PURPOSE PROCESSORS (CSPP)

Custom single purpose processors are designed for a very specific task. This implies less

flexibility, longer time-to-market and high costs. On the other hand CSPP can be designed to be

very small, fast and power-efficient. Examples for such CSPP are FPGAs or more general PLDs.

1.4.4. APPLICATION SPECIFIC INSTRUCTION-SET PROCESSORS (ASIP)

ASIPs are basically standard general purpose processors which are extended by domain-

specific instructions. This allows domain-relevant tasks to be performed highly optimized, while

keeping the flexibility of general purpose processors.

1.4.5. SPECIFIC DESIGN OF EMBEDDED SYSTEM PROCESSOR

When designing an embedded system, usually, the first step is to specify the intended or

required functionality. This is mostly done using natural language, after the functionality is


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specified it is formalized in some sort of definition language such as VHDL or Verilog.

Subsequently the resulting design is converted into hardware or software components which are

then implemented.

MICROCONTROLLER

4.1 INTRODUCTION

Microcontroller is a microprocessor designed specifically for control applications, and is

equipped with ROM, RAM and facilities I / O on a single chip.AT89S52 is one of the family

MCS-51/52 equipped with an internal 8 Kbyte Flash EPROM (Erasable and Programmable Read

Only Memory), which allows memory to be reprogrammed.

The AT89S52 is a low-power, high-performance CMOS 8-bit microcomputer with 4Kbytes of

Flash programmable and erasable read only memory (PEROM).This device is a Single-chip 8-bit

Microcontroller and is a derivative of the 8051 microcontroller family. The instruction set is

100% compatible with the 8051 instruction set. The on-chip Flash allows the program memory

to be reprogrammed in-system or by a conventional nonvolatile memory programmer. Bycombining a versatile 8-bit CPU with Flash on a monolithic chip, the Atmel AT89S52 is a

powerful microcomputer which provides a highly-flexible and cost-effective solution to many

embedded control applications.


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FEATURES OF MICROCONTROLLER

A CPU (central processing unit) 8 bits.

256 bytes of RAM (random access memory) internally.

Four ports of I/O with each consist of 8 bit.

The internal oscillator and timing circuit.

Two timers/counters 16 bits.

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

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

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

The size of 8 Kbytes EPROM for program memory.

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

execution.

CPU (central processing unit)

This section serves to control the entire operation on the microcontroller. This unit is divided into

two parts, the control unit, or CU (Control Unit) and the arithmetic and logic unit or ALU

(Arithmetic Logic Unit) The main function control unit is to take instructions from memory

(fetch) and then translate the composition of these instructions into a simple collection of work

processes (decode), and implement instruction sequence in accordance with the steps that have

been determined the program (execute). Arithmetic and logic unit is the part that deals with

arithmetic operations like addition, subtraction, and logical data manipulation operations such as

AND, OR, and comparison.

4.2.2 INPUT/OUTPUT (I/O)

This section serves as a communication tool with a single chip device outside the system.

Consistent with the name, I / O devices can receive and provide data to / from a single chip.


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There are two kinds of devices I / O is used, ie devices for serial connection UART (Universal

Asynchronous Receiver Transmitter) and device for so-called parallel relationship with the PIO

(Parallel Input Output).Both types of I / O has been available in a single chip AT89S52.

SOFTWARE

Single flakes MCS-51 family has a special programming language that is not understood by

other types of single flakes. This programming language known by the name of the assembler

language instruction has 256 devices. However, when this can be done with microcontroller

programming using C language. With the C language, microcontroller programming easier,

because the C language format will be automatically converted into assembler language with a

hex file format. Software on a microcontroller can be divided into five groups as follows:


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PIN CONFIGURATION

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

as follows:

4.3.1 THE FUNCTION OF EACH PIN AT89S52

Vcc:Supply Voltage.

GND:Ground.

Port 0:
http://electricly.com/wp-content/uploads/2010/06/AT89S52-MICROCONTROLLER-configuration.jpg


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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 can also be configured to be the multiplexed low-order address/data bus during accesses

to external programmed 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.

Port 1:

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

Port 2:



internal pull-ups and can be used as inputs. As inputs, Port 2 pins that are externally being pulled

low will source current (IIL) because of the internal pull-ups. Port 2 emits the high-order address

byte during fetching from external program memory and during access to external data memory

that uses 16-bit addresses (MOVX @DPTR). In this application, Port 2 uses strong internal pull-

ups when emitting 1s. During accesses to external data memory that uses 8-bit address (MOVX

@R1), Port 2 emits the contents of the P2 Special Function Register. Port 2 also receives the

high-order address bits and some control signals during Flash program and verification.

Port 3:



internal pull-ups and can be used as inputs. As inputs, Port 3 pins that are externally being pulled


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low will source current (IIL) because of the pull-ups. Port 3 also serves the functions of

Port 3 pin alternate Functions:

P 3.0 RXD (Serial Input Port)

P 3.1 TXD (Serial Output Port)

P 3.2 INT0 (External Interrupt 0)

P 3.3 INT1 (External Interrupt 1)

P 3.4 T0 (Timer 0 External Input)

P 3.5 T1 (Timer 1 External Input)

P 3.6 WR (External Data Memory Write Strobe)

P 3.7 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. This

pin drives High for 98 oscillator periods after the Watchdog times out.

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.

In normal operation, ALE is emitted at a constant rate of 1/6 the oscillator frequency and may be

used for external timing or clocking purposes. 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


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It is the read strobe to external program memory. When the AT89S52 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/ Programming Enable Voltage

External Access Enable 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 12-volt programming enable voltage

(Vpp) during Flash programming.

XTAL1:

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

XTAL2:

It is the output from the inverting oscillator amplifier.


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TIMER

Timer0: 8-bit timer/counter with 8-bit prescaler

Timer1: 16-bit timer/counter with prescaler

Timer2: 8-bit timer/counter with 8-bit period register, prescaler and postscaler.

Mode 0: 13-Bit Timer

Lower byte (TL0/TL1) + 5 bits of upper bytes (TH0/TH1).

Backward compatible to the 8048

Not generally used

Timer operation in Mode 0

Mode 1: 16-bit

All 16 bits of the timer (TH0/TL0, TH1,and TL1) are used.

Maximum count is 65,536

At 12 MHz, maximum interval is 65536 microseconds or 65.536

milliseconds

TF0 must be reset after each overflow

THx/TLx must be manually reloaded after each overflow.

Mode 2: 8-bit Auto Reload

Only the lower byte (TLx) is used for counting.

Upper byte (THx) holds the value to reload into TLx after and overflow.

TFx must be manually cleared.

Maximum count is 256

Maximum interval is 256 Microseconds or .256 milliseconds

INTERRUPT

Hardware interrupts were introduced as a way to avoid wasting the processor's valuable time

in polling loops, waiting for external events. They may be implemented in hardware as a distinct

system with control lines, or they may be integrated into the memory subsystem.

If implemented in hardware, an interrupt controller circuit such as the IBM PC's Programmable

Interrupt Controller (PIC) may be connected between the interrupting device and the processors


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interrupt pin to multiplex several sources of interrupt onto the one or two CPU lines typically

available. If implemented as part of the memory controller, interrupts are mapped into the

system's memory address space.

Interrupts can be categorized into: maskable interrupt, non-maskable interrupt (NMI), inter-processorinterrupt (IPI), software interrupt, and spurious interrupt.

Maskable interrupt (IRQ) is a hardware interrupt that may be ignored by setting a bit in

an interrupt mask register's (IMR) bit-mask.

Non-maskable interrupt(NMI) is a hardware interrupt that lacks an associated bit-mask, so

that it can never be ignored. NMIs are often used for timers, especially watchdog timers.

Inter-processor interrupt(IPI) is a special case of interrupt that is generated by one

processor to interrupt another processor in a multiprocessor system.

Software interruptis an interrupt generated within a processor by executing an instruction.

Software interrupts are often used to implement system calls because they implement a

subroutine call with a CPU ring level change.

Spurious interruptis a hardware interrupt that is unwanted. They are typically generated by

system conditions such as electrical interference on an interrupt line or through incorrectly

designed hardware.

Processors typically have an internal interrupt mask which allows software to ignore all external

hardware interrupts while it is set. This mask may offer faster access than accessing an interrupt

mask register (IMR) in a PIC, or disabling interrupts in the device itself. In some cases, such as

the x86 architecture, disabling and enabling interrupts on the processor itself act as a memory

barrier, however it may actually be slower.

An interrupt that leaves the machine in a well-defined state is called a precise interrupt. Such an

interrupt has four properties:

The Program Counter (PC) is saved in a known place.

All instructions before the one pointed to by the PC have fully executed.

No instruction beyond the one pointed to by the PC has been executed (that is no prohibition

on instruction beyond that in PC, it is just that any changes they make to registers or memory

must be undone before the interrupt happens).


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The execution state of the instruction pointed to by the PC is known.

An interrupt that does not meet these requirements is called an imprecise interrupt.

The phenomenon where the overall system performance is severely hindered by excessive

amounts of processing time spent handling interrupts is called an interrupt storm.

TYPES OF INTERRUPT

LEVEL-TRIGGERED

EDGE-TRIGGERED

HYBRID

MESSAGE SIGNALED

DOORBELL

USES OF INTERRUPT

Typical uses of interrupts include the following: system timers, disks I/O, power-off signals,

and traps. Other interrupts exist to transfer data bytes using UARTs or Ethernet; sense key-

presses; control motors; or anything else the equipment must do.

A classic system timer generates interrupts periodically from a counter or the power-line. The

interrupt handler counts the interrupts to keep time. The timer interrupt may also be used by the

OS's task scheduler to reschedule the priorities of running processes. Counters are popular, but

some older computers used the power line frequency instead, because power companies in most

Western countries control the power-line frequency with a very accurate atomic clock.

A disk interrupt signals the completion of a data transfer from or to the disk peripheral. A

process waiting to read or write a file starts up again.

A power-off interrupt predicts or requests a loss of power. It allows the computer equipment to

perform an orderly shut-down.

Interrupts are also used in type ahead features for buffering events like keystrokes.


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NEED OF MICROCONTROLLER

Microcontroller is a general-purpose device which has in-built CPU memory and

peripherals to make it act as a mini-computer

Microcontroller has one or two operational codes for moving data from external to CPU

Microcontroller has many bit handling instructions

Microcontroller works faster than microprocessor because of rapid movement of bits

within the chip

Microcontroller can function as a computer with the addition of no external parts


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POWER SUPPLY

INTRODUCTION

A power supply is a device that supplies electrical energy to one or more electric loads. The term

is most commonly applied to devices that convert one form of electrical energy to another,

though it may also refer to devices that convert another form of energy (e.g., mechanical,

chemical, solar) to electrical energy. A regulated power supply is one that controls the output

voltage or current to a specific value; the controlled value is held nearly constant despite

variations in either load current or the voltage supplied by the power supply's energy source.

Every power supply must obtain the energy it supplies to its load, as well as any energy it

consumes while performing that task, from an energy source. Depending on its design, a power

supply may obtain energy from:

Electrical energy transmission systems. Common examples of this include power supplies

that convert AC line voltage to DC voltage.

Energy storage devices such as batteries and fuel cells.

Electromechanical systems such as generators and alternators.

Solar power.

A power supply may be implemented as a discrete, stand-alone device or as an integral device

that is hardwired to its load. Examples of the latter case include the low voltage DC power

supplies that are part of desktop computers and consumer electronics devices.

The amount of voltage and current it can supply to its load.

How stable its output voltage or current is under varying line and load conditions.

How long it can supply energy without refueling or recharging (applies to power supplies

that employ portable energy sources)

.


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EXPLAINATION AND BLOCK DIAGRAM

The ac voltage, typically 220V rms, is connected to a transformer, which steps that ac

voltage down to the level of the desired dc output. A diode rectifier then provides a full-

wave rectified voltage that is initially filtered by a simple capacitor filter to produce a dcvoltage. This resulting dc voltage usually has some ripple or ac voltage variation.

A regulator circuit removes the ripples and also remains the same dc value even if the input

dc voltage varies, or the load connected to the output dc voltage changes. This voltage

regulation is usually obtained using one of the popular voltage regulator IC units.

POWER SUPPLY

Regulator

Filter

Bridge

RectifierStep down

transformer

230V

AC

D.C

Output


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CIRCUIT DIAGRAM OF POWER SUPPLY


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WORKING OF POWER SUPLLY

TRANSFORMER:

Usually, DC voltages are required to operate various electronic equipment and these voltages are

5V, 9V or 12V. But these voltages cannot be obtained directly. Thus the a.c input available at the

mains supply i.e., 230V is to be brought down to the required voltage level. This is done by a

transformer. Thus, a step down transformer is employed to decrease the voltage to a required

level.

RECTIFIER:

The output from the transformer is fed to the rectifier. It converts A.C. into pulsating D.C. The

rectifier may be a half wave or a full wave rectifier. In this project, a bridge rectifier is used

because of its merits like good stability and full wave rectification.

FILTER:

Capacitive filter is used in this project. It removes the ripples from the output of rectifier and

smoothens the D.C. Output received from this filter is constant until the mains voltage and load

is maintained constant. However, if either of the two is varied, D.C. voltage received at this point

changes. Therefore a regulator is applied at the output stage.

VOLTAGE REGULATOR:

As the name itself implies, it regulates the input applied to it. A voltage regulator is an electrical

regulator designed to automatically maintain a constant voltage level. In this project, power

supply of 5V and 12V are required. In order to obtain these voltage levels, 7805 and 7812

voltage regulators are to be used. The first number 78 represents positive supply and the numbers

05, 12 represent the required output voltage levels.


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5.5 POWER SUPPLY APPLICATION

5.5.1 Computer power supply

A modern computer power supply is a switch-mode power supply that converts AC power from

the mains supply, to several DC voltages. Switch-mode supplies replaced linear supplies due to

cost, weight, and size improvement. The diverse collection of output voltages also has widely

varying current draw requirements.

5.5.2 Welding power supply

Arc welding uses electricity to melt the surfaces of the metals in order to join them together

through coalescence. The electricity is provided by a welding power supply, and can either

be AC or DC. Arc welding typically requires high currents typically between 100 and 350 amps.

Some types of welding can use as few as 10 amps, while some applications of spot

welding employ currents as high as 60,000 amps for an extremely short time. Older welding

power supplies consisted of transformers or engines driving generators. More recent supplies

use semiconductors and microprocessors reducing their size and weight.

5.5.3 AC Adapter

A power supply that is built into an AC mains power plug is known as a "plug pack" or "plug-in

adapter", or by slang terms such as "wall wart". They are even more diverse than their names;

often with either the same kind of DC plug offering different voltage or polarity, or a different

plug offering the same voltage. "Universal" adapters attempt to replace missing or damaged

ones, using multiple plugs and selectors for different voltages and polarities. Re5lacementpower

supplies must match the voltage of, and supply at least as much current as, the original power

supply.


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LIQUID CRYSTAL DISPLAY

LCD (Liquid Crystal Display) screen is an electronic display module and find a wide range of

applications. A 16x2 LCD display is very basic module and is very commonly used in various

devices and circuits. These modules are preferred over seven segment and other multisegment LEDs. The reasons being: LCDs are economical; easily programmable; have no

limitation of displaying special & evencustom characters(unlike in seven

segments), animationsand so on.

A 16x2 LCD means it can display 16 characters per line and there are 2 such lines. In this LCD

each character is displayed in 5x7 pixel matrix. This LCD has two registers, namely, Command

and Data.

The command register stores the command instructions given to the LCD. A command is an

instruction given to LCD to do a predefined task like initializing it, clearing its screen, setting the

cursor position, controlling display etc. The data register stores the data to be displayed on the

LCD. The data is the ASCII value of the character to be displayed on the LCD.

LCDs are used in a wide range of applications, including computer monitors, television,

instrument panels, aircraft cockpit displays, signage, etc. They are common in consumer devices

such as video players, gaming devices, clocks, watches, calculators, and telephones. LCDs have

replaced cathode ray tube (CRT) displays in most applications. They are available in a wider

range of screen sizes than CRT and plasma displays, and since they do not use phosphors, they

cannot suffer image burn-in. LCDs are, however, susceptible to image persistence.

The LCD is more energy efficient and offers safer disposal than a CRT. Its low electrical power

consumption enables it to be used in battery-powered electronic equipment. It is an electronically

modulated optical device made up of any number of segments filled with liquid crystals and

arrayed in front of a light source (backlight) or reflector to produce images in color

or monochrome. The most flexible ones use an array of small pixels. The earliest discovery

leading to the development of LCD technology, the discovery of liquid crystals, dates from 1888.

By 2008, worldwide sales of televisions with LCD screens had surpassed the sale of CRT units.
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6.2 FEATURES

5 x 8 dots with cursor

Built-in controller (KS 0066 or equivalent)

+5V power supply (also available for +3V)

1/16 duty cycle

B/L to be driven 1,pin 2 or pin 15,pin 16

N.V. optional for +3V power supply

LCD can display a character successfully by placing the

1. Data in Data Register

2.

Command in Command Register of LCD

3. Data corresponds to the ASCII value of the character to be printed. This can be done by

placing the ASCII value on the LCD Data lines and selecting the Data Register of the

LCD by selecting the RS (Register Select) pin.

4. Each and every display location is accessed and controlled by placing respective command on

the data lines and selecting the Command Register of LCD by selecting the (Register Select) RS

pin.

TABLE 1: Pin description for LCD

Pin symbol I/O Description

1 Vss -- Ground

2 Vcc -- +5V power supply

3 VEE -- Power supply to

control contrast


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TYPES OF DISPLAY LCD:

Segment (or alphanumeric)

Dot matrix (or character)

Graphic LCD.

4 RS I RS=0 to select

command register

RS=1 to select

data register

5 R/W I R/W=0 for write

R/W=1 for read

6 E I/O Enable

7 DB0 I/O The 8-bit data bus









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Advantages and disadvantages of LCDs

In spite of LCDs being a well proven and still viable technology, as display devices LCDs are

not perfect for all applications.

6.5.1 Advantages

Very compact and light.

Low power consumption.

No geometric distortion.

Little or no flicker depending on backlight technology.

Not affected by screen burn-in.

Can be made in almost any size or shape.

No theoretical resolution limit.

6.5.2 Disadvantages

Limited viewing angle, causing color, saturation, contrast and brightness to vary, even

within the intended viewing angle, by variations in posture.

Bleeding and uneven backlighting in some monitors, causing brightness distortion,

especially toward the edges.

Smearing and ghosting artifacts caused by slow response times (>8 ms) and "sample and

hold" operation.

Only one native resolution. Displaying resolutions either requires a video scaler, lowering

perceptual quality, or display at 1:1 pixel mapping, in which images will be physically

too large or won't fill the whole screen.

Fixed bit depth, many cheaper LCDs are only able to display 262,000 colors. 8-bit S-IPSpanels can display 16 million colors and have significantly better black level, but are

expensive and have slower response time.

Low bit depth results in images with unnatural or excessive contrast.

Input lag

Dead or stuck pixels may occur during manufacturing or through use.


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In a constant-on situation, thermalization may occur, which is when only part of the

screen has overheated and looks discolored compared to the rest of the screen.

Not all LCDs are designed to allow easy replacement of the backlight.

Cannot be used with light guns/pens.

Loss of contrast in high temperature environments.

6.6 MAX 232

max 232 circuit diagram

Since the RS232 (Recommended Standard) is not compatible with todays microprocessor and

microcontrollers, we need a line driver to convert the RS232s signal to TTL voltage levels that

will be acceptable to the AT89C51 TXD and RXD pins.


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One example of such a converter is MAX 232. MAX 232 converts from Rs232 voltage levels to

TTL voltage levels, and vice versa. One advantages of the MAX232 chip is that it uses a +5v

power source which ,is the same as the source voltages for the 89C52.

In other words with a single +5v power supply we can power both the AT89C51 and MAX232,

with no need for the dual power supply that are common in many older systems. The MAX232

has 2 sets of line drivers for transferring and receiving data, as shown the line drivers used for

TXD are called T1 and T2, while the line drives for RXD are designated as R1 and R2.

The MAX232 is anintegrated circuit that converts signals from anRS-232 serial port to signals

suitable for use inTTL compatible digital logic circuits. The MAX232 is a dual driver/receiver

and typically converts the RX, TX, CTS and RTS signals.

The drivers provide RS-232 voltage level outputs (approx. 7.5 V) from a single + 5 V supply

via on-chipcharge pumps and external capacitors. This makes it useful for implementing RS-232

in devices that otherwise do not need any voltages outside the 0 V to + 5 V range, aspower

supply design does not need to be made more complicated just for driving the RS-232 in this

case.

The receivers reduce RS-232 inputs (which may be as high as 25 V), to standard

5 VTTL levels. These receivers have a typical threshold of 1.3 V, and a typicalhysteresis of

0.5 V.

The later MAX232A is backwards compatible with the original MAX232 but may operate at

higherbaud rates and can use smaller external capacitors 0.1Fin place of the 1.0 F

capacitors used with the original device. The newer MAX3232 is also backwards compatible, but

operates at a broader voltage range, from 3 to 5.5 V.
http://en.wikipedia.org/wiki/Integrated_circuithttp://en.wikipedia.org/wiki/RS-232http://en.wikipedia.org/wiki/Transistor-transistor_logichttp://en.wikipedia.org/wiki/Charge_pumphttp://en.wikipedia.org/wiki/Power_supplyhttp://en.wikipedia.org/wiki/Power_supplyhttp://en.wikipedia.org/wiki/Transistor-transistor_logichttp://en.wikipedia.org/wiki/Hysteresishttp://en.wikipedia.org/wiki/Baudhttp://en.wikipedia.org/wiki/Faradhttp://en.wikipedia.org/wiki/Faradhttp://en.wikipedia.org/wiki/Faradhttp://en.wikipedia.org/wiki/Faradhttp://en.wikipedia.org/wiki/Baudhttp://en.wikipedia.org/wiki/Hysteresishttp://en.wikipedia.org/wiki/Transistor-transistor_logichttp://en.wikipedia.org/wiki/Power_supplyhttp://en.wikipedia.org/wiki/Power_supplyhttp://en.wikipedia.org/wiki/Charge_pumphttp://en.wikipedia.org/wiki/Transistor-transistor_logichttp://en.wikipedia.org/wiki/RS-232http://en.wikipedia.org/wiki/Integrated_circuit


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GSM

7.1 INTRODUCTION

GSM (Global System for Mobile Communications: originally from Groupe Special Mobile) is

the world's most popularstandard formobile telephony systems. TheGSM Association estimates

that 80% of the global mobile market uses the standard. GSM is used by over 1.5

billionpeople across more than 212 countries and territories. This ubiquity means that

subscribers can use their phones throughout the world, enabled by

internationalroaming arrangements between mobile network operators. GSM differs from its

predecessor technologies in that both signalling and speech channels aredigital,and thus GSM is

considered a second generation (2G)mobile phone system. This also facilitates the wide-spread

implementation of data communication applications into the system.

The GSM standard has been an advantage to both consumers, who may benefit from the ability

to roam and switch carriers without replacing phones, and also to network operators, who can

choose equipment from many GSM equipment vendors. GSM also pioneered low-cost

implementation of theshort message service (SMS), also called text messaging, which has since

been supported on other mobile phone standards as well. The standard includes a

worldwideemergency telephone number feature.

Newer versions of the standard were backward-compatible with the original GSM system. For

example,Release '97 of the standard added packet data capabilities by means ofGeneral Packet

Radio Service (GPRS). Release '99 introduced higher speed data transmission usingEnhanced

Data Rates for GSM Evolution (EDGE).
http://en.wikipedia.org/wiki/Comparison_of_mobile_phone_standardshttp://en.wikipedia.org/wiki/Mobile_telephonyhttp://en.wikipedia.org/wiki/GSM_Associationhttp://en.wikipedia.org/wiki/1000000000_(number)http://en.wikipedia.org/wiki/Roaminghttp://en.wikipedia.org/wiki/Mobile_network_operatorhttp://en.wikipedia.org/wiki/Digitalhttp://en.wikipedia.org/wiki/2Ghttp://en.wikipedia.org/wiki/Short_message_servicehttp://en.wikipedia.org/wiki/Emergency_telephone_numberhttp://en.wikipedia.org/wiki/3GPP#Standardshttp://en.wikipedia.org/wiki/General_Packet_Radio_Servicehttp://en.wikipedia.org/wiki/General_Packet_Radio_Servicehttp://en.wikipedia.org/wiki/Enhanced_Data_Rates_for_GSM_Evolutionhttp://en.wikipedia.org/wiki/Enhanced_Data_Rates_for_GSM_Evolutionhttp://en.wikipedia.org/wiki/Enhanced_Data_Rates_for_GSM_Evolutionhttp://en.wikipedia.org/wiki/Enhanced_Data_Rates_for_GSM_Evolutionhttp://en.wikipedia.org/wiki/General_Packet_Radio_Servicehttp://en.wikipedia.org/wiki/General_Packet_Radio_Servicehttp://en.wikipedia.org/wiki/3GPP#Standardshttp://en.wikipedia.org/wiki/Emergency_telephone_numberhttp://en.wikipedia.org/wiki/Short_message_servicehttp://en.wikipedia.org/wiki/2Ghttp://en.wikipedia.org/wiki/Digitalhttp://en.wikipedia.org/wiki/Mobile_network_operatorhttp://en.wikipedia.org/wiki/Roaminghttp://en.wikipedia.org/wiki/1000000000_(number)http://en.wikipedia.org/wiki/GSM_Associationhttp://en.wikipedia.org/wiki/Mobile_telephonyhttp://en.wikipedia.org/wiki/Comparison_of_mobile_phone_standards


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7.2 THE CELLULAR NETWORK

GSM REFERENCE MODEL

MS

The MS consist of physical equipment used by the subscriber to access a PLMN for offered

telecommunication services. The MS includes a Mobile Terminal and depending on the services

it can support various Terminal Equipment(TE).Various type of MS, such as vehicle mounted

station, portable station, or handheld station, are used.

The MSs come in five power classes which define the maximum RF power level that the unit

can transmit. Basically, an MS can be divided into two parts. The first part contains the hardware

and software to support radio and human interface functions. The second part contains

terminal/user-specific data in the form of a smart card, which can effectively be considered a sort

of logical terminal. The SIM card plugs into the first part of the MS and remains in for the

duration of use. Without the SIM card, the MS is not associated with any user and cannot make

or receive calls (except possibly an emergency cal l if the network allows). The SIM card is

issued by the mobile service provider after subscription, while the first part of the MS would be


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SIM

The SIM carries the following information

IMSI

Authentication Key (Ki)

Subscriber information

Access control class

Cipher Key (Kc)

TMSI

Additional GSM services

Location Area Identity (LAI)

Forbidden PLMN

BSS

The BSS is the physical equipment that provides radio coverage to prescribed geographical

areas, known as the cells. It contains equipment required to communicate with the MS.

Functionally, a BSS consists of a control function carried out by the BSC and a transmittingfunction performed by the BTS. The BTS is the radio transmission equipment and covers each

cell. A BSS can serve several cells because it can have multiple BTSs.The BTS contains the

Transcoder Rate Adapter Unit (TRAU). In TRAU, the GSM-specific speech encoding and

decoding is carried out, as well as the rate adaptation function for data. In certain situations the

TRAU is located at the MSC to gain an advantage of more compressed transmission between the

BTS and the MSC

NSS


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The NSS includes the main switching functions of GSM, databases required for the subscribers,

and mobility management. Its main role is to manage the communi cat ions between GSM and

other network users.Within the NSS, the switching functions are performed by the MSC.

Subscriber information relevant to provisioning of services is kept in the HLR. The other

database in the NSS is the VLR. The MSC performs the necessary switching functions required

for the MSs located in an associated geographical area, called an MSC area. The MSC monitors

the mobility of its subscribers and manages necessary resources required to handle and update

the location registration procedures and to carry out the handover functions. The MSC is

involved in the interworking functions to communicate with other networks such as PSTN and

ISDN. The interworking functions of the MSC depend upon the type of the network to which it

is connected and the type of service to be performed. The call routing and control and echo

control functions are also performed by the MSC.

The HLR is the functional unit used for management of mobile subscribers. The number of

HLRs in a PLMN varies with the characteristics of the PLMN. Two types of information are

stored in the HLR: subscriber information and part of the mobile information to allow incoming

calls to be routed to the MSC for the particular MS. Any administrative action by the service

provider on subscriber data is performed in the HLR. The HLR stores IMSI, MS ISDN number,

VLR address, and subscriber data (e.g., supplementary services).

The VLR is linked to one or more MSCs. The VLR is the functional unit that dynamically stores

subscriber information when the subscriber is located in the area covered by the VLR. When a

roaming MS enters an MSC area, the MSC informs the associated VLR about the MS the

MS goes through a registration procedure. The registration procedure for the MSincludes these

activities:

The VLR recognizes that the MS is from another PLMN.

If roaming is allowed, the VLR finds the MSs HLR in its home PLMN. The VLR constructs a Global Title (GT) from the IMSI to allow signaling from the VLR

to the MSs HLR via the PSTN/ISDN networks.

The VLR generates a Mobile Subscriber Roaming Number (MSRN) thatis used to route

incoming calls to the MS.


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The MSRN is sent to the MSs HLR.

DC MOTOR:

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 thecurrent in the conductor, and to the strength of

the external magnetic field. As you are well aware of from playing with magnets as a kid,

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.

The shunt motor is different from the series motor in that the field winding is connected

in parallel with the armature instead of in series. You should remember from basic electrical

theory that a parallel circuit is often referred to as a shunt. Since the field winding is placed in

parallel with the armature, it is called a shunt winding and the motor is called a shunt motor.

Figure shows a diagram of a shunt motor. Notice that the field terminals are marked Fl and F2,

and the armature terminals are marked Al andA2. You should notice in this diagram that the

shunt field is represented with multiple turns using a thin line.

Let's start by looking at a simple 2-poleDC electric motor (here red represents a magnet

or winding with a "North" polarization, while green represents a magnet or winding with a

"South" polarization).
http://encyclobeamia.solarbotics.net/articles/current.htmlhttp://encyclobeamia.solarbotics.net/articles/current.htmlhttp://encyclobeamia.solarbotics.net/articles/dc.htmlhttp://encyclobeamia.solarbotics.net/articles/current.htmlhttp://encyclobeamia.solarbotics.net/articles/dc.htmlhttp://encyclobeamia.solarbotics.net/articles/dc.htmlhttp://encyclobeamia.solarbotics.net/articles/current.htmlhttp://encyclobeamia.solarbotics.net/articles/dc.htmlhttp://encyclobeamia.solarbotics.net/articles/current.htmlhttp://encyclobeamia.solarbotics.net/articles/current.html


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Every DC motor has six basic parts -- axle, rotor (a.k.a., armature), stator, commutator, field

magnet(s), and brushes. In most common DC motors (and all that BEAMers will see), the

external magnetic field is produced by high-strength permanent magnets1. The stator is the

stationary part of the motor; this includes the motor casing, as well as two or more permanent

magnet pole pieces. The rotor (together with the axle and attached commutator) rotates with

respect to the stator. The rotor consists of windings (generally on a core), the windings being

electrically connected to the commutator. The above diagram shows a common motor layout --

with the rotor inside the stator (field) magnets.

The geometry of the brushes, commutator contacts, and rotor windings are such that

when power is applied, the polarities of the energized winding and the stator magnet(s) are

misaligned, and the rotor will rotate until it is almost aligned with the stator's field magnets. As

the rotor reaches alignment, the brushes move to the next commutator contacts, and energize the

next winding. Given our example two-pole motor, the rotation reverses the direction ofcurrent

through the rotor winding, leading to a "flip" of the rotor's magnetic field, driving it to continue

rotating.

In real life, though, DC motors will always have more than two poles (three is a very common

number). In particular, this avoids "dead spots" in the commutator. You can imagine how with

our example two-pole motor, if the rotor is exactly at the middle of its rotation (perfectly aligned

with the field magnets), it will get "stuck" there. Meanwhile, with a two-pole motor, there is a

moment where the commutator shorts out the power supply (i.e., both brushes touch both
http://encyclobeamia.solarbotics.net/articles/dc.htmlhttp://encyclobeamia.solarbotics.net/articles/beam.htmlhttp://encyclobeamia.solarbotics.net/articles/current.htmlhttp://encyclobeamia.solarbotics.net/articles/dc.htmlhttp://encyclobeamia.solarbotics.net/articles/dc.htmlhttp://encyclobeamia.solarbotics.net/articles/current.htmlhttp://encyclobeamia.solarbotics.net/articles/beam.htmlhttp://encyclobeamia.solarbotics.net/articles/dc.html


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commutator contacts simultaneously). This would be bad for the power supply, waste energy,

and damage motor components as well. Yet another disadvantage of such a simple motor is that

it would exhibit a high amount oftorque "ripple" (the amount oftorque it could produce is cyclic

with the position of the rotor).

Diagram of DC shunt motor.

Two factors are important in the selection of a motor for a particular application: the

variation of the speed with a change in load, and the variation of the torque with a change in

load. A shunt motor is basically a constant speed device. If a load is applied, the motor tends to

slow down.

The slight loss in speed reduces the counter emf and results in an increase of the armature

current. This action continues until the increased current produces enough torque to meet the

demands of the increased load. As a result, the shunt motor is in a state of stable equilibrium
http://encyclobeamia.solarbotics.net/articles/torque.htmlhttp://encyclobeamia.solarbotics.net/articles/torque.htmlhttp://encyclobeamia.solarbotics.net/articles/torque.htmlhttp://encyclobeamia.solarbotics.net/articles/torque.html


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because a change of load always produces a reaction that adapts the power input to the change in

load.

The basic circuit for a shunt motor is shown in figure. Note that only a shunt field winding

is shown. Figure shows the addition of a series winding to counteract the effects of armature

reaction. From the standpoint of a schematic diagram, figure represents a compound motor.

However, this type of motor is not considered to be a com pound motor because the

commutating winding is not wound on the same pole as the field winding and the series field has

only a few turns of wire in series with the armature circuit. As a result, the operating

characteristics are those of a shunt motor. This is so noted on the nameplate of the motor by the

terms compensated shunt motor or stabilized shunt motor.

DC MOTOR CONTROL CHARACTERISTICS:

A shunt-wound motor is a direct-current motor in which the field windings and the

armature may be connected in parallel across a constant-voltage supply. In adjustable speed

applications, the field is connected across a constant-voltage supply and the armature is

connected across an independent adjustable-voltage supply. Permanent magnet motors have

similar control

DC MOTOR CHARACTERISTICS:

It will be easier to understand the operation of the DC motor from a basic diagram

that shows the magnetic interaction between the rotating armature and the stationary field's coils.

Below Figure shows three diagrams that explain the DC motor's operation in terms of the

magnetic interaction.


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That a bar magnet has been mounted on a shaft so that it can spin. The field winding is

one long coil of wire that has been separated into two sections. The top section is connected to

the positive pole of the battery and the bottom section is connected to the negative pole of the

battery. It is important to understand that the battery represents a source of voltage for this

winding. In the actual industrial-type motor this voltage will come from the DC voltage source

for the motor. The current flow in this direction makes the top coil the north pole of the magnet

and the bottom coil the south pole of the magnet.

The bar magnet represents the armatureand the coil of wire represents the field.The arrow

shows the direction of the armature's rotation. Notice that the arrow shows the armature starting

to rotate in the clockwise direction. The north pole of the field coil is repelling the north pole of

the armature, and the south pole of the field coil is repelling the south pole of the armature.

(a) Magnetic diagram that explains the operation of a DC motor. The rotating magnet moves

clockwise because like poles repel.(b) The rotating magnet is being attracted because the poles are unlike.

(c) The rotating magnet is now shown as the armature coil, and its polarity is determined by

the brushes and commutator segments.


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This action switches the direction of current flow through the armature, which also

switches the polarity of the armature coil's magnetic field at just the right time so that the

repelling and attracting continues. The armature continues to switch its magnetic polarity twice

during each rotation, which causes it to continually be attracted and repelled with the field poles.

This is a simple two-pole motor that is used primarily for instructional purposes.

Since the motor has only two poles, the motor will operate rather roughly and not provide too

much torque. Additional field poles and armature poles must be added to the motor for it to

become useful for industry.

Two factors are important in the selection of a motor for a particular application:

(1) the variation of the speed with a change in load.

(2) the variation of the torque with a change in load.

A shunt motor is basically a constant speed device. If a load is applied, the motor tends

to slow down. The slight loss in speed reduces the counter emf and results in an increase of the

armature current.

This action continues until the increased current produces enough torque to meet the

demands of the increased load. As a result, the shunt motor is in a state of stable equilibrium

because a change of load always produces a reaction that adapts the power input to the change in

load.

The basic circuit for a shunt motor is shown in figure . Note that only a shunt field

winding is shown. Figure 1-10B shows the addition of a series winding to counteract the effects

of armature reaction. From the standpoint of a schematic diagram, figure 1-10B represents a

compound motor. However, this type of motor is not considered to be a com pound motor

because the commutating winding is not wound on the same pole as the field winding and the

series field has only a few turns of wire in series with the armature circuit.

As a result, the operating characteristics are those of a shunt motor. This is so noted on the

nameplate of the motor by the terms compensated shunt motor or stabilized shunt motor.

Speed Control

A dc shunt motor has excellent speed control. To operate the motor above its rated speed, a

field rheostat is used to reduce the field current and field flux. To operate below rated speed,

reduce the voltage applied to the armature circuit.


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A more modem method of speed control is the electronic speed control system. The principles of

control are the same as the manual controls. Speeds above normal are achieved by reducing the

field voltage electronically and speeds below normal reduce the voltage applied to the armature.

Rotation

The direction of armature rotation may be changed by reversing the direction of cur rent in

either the field circuit or the armature circuit. For a motor with a simple shunt field circuit, it may

be easier to reverse the field circuit lead. If the motor has a series winding, or an interpole

winding to counteract armature reaction, the same relative direction of cur rent must be

maintained in the shunt and series windings. For this reason, it is always easier to reverse the

direction of the armature current.

Shunt motor connections:

(A) Without Commutating Poles; (B) With Commutating Poles

Torque

A dc shunt motor has high torque at any speed. At startup, a dc shunt motor develops 150 percentof its rated torque if the resistors used in the starting mechanism are capable of withstanding the

heating effects of the current. For very short periods of time, the motor can develop 350 percent

of full load torque, if necessary.

Speed Regulation

The speed regulation of a shunt motor drops from 5 percent to 10 percent from the no-load state

to full load. As a result, a shunt motor is superior to the series dc motor, but is inferior to a

compound-wound dc motor. Figure shows a dc motor with horse power ratings ranging from 1

hp to 5 hp.

the field coil. In this application the armature coil is usually changed, as was the case with the

series motor. the electrical diagram of a DC shunt motor connected to a forward and reversing

motor starter. You should notice that the Fl and F2 terminals of the shunt field are connected


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directly to the power supply, and the Al and A2 terminals of the armature winding are

connected to the reversing starter. When the FMS is energized, its contacts connect the Al lead

to the positive power supply terminal and the A2 lead to the negative power supply terminal.

The Fl motor lead is connected directly to the positive terminal of the power supply and

the F2 lead is connected to the negative terminal. When the motor is wired in this

configuration, it will begin to run in the forward direction. When the RMS is energized, its

contacts reverse the armature wires so that the Al lead is connected to the negative power

supply terminal and the A2 lead is connected to the positive power supply terminal. The field

leads are connected directly to the power supply, so their polarity is not changed.

Since the field's polarity has remained the same and the armature's polarity has reversed,

the motor will begin to rotate in the reverse direction. The control part of the diagram shows

that when the FMS coil is energized, the RMS coil is locked out. Installing a Shunt Motor A

shunt motor can be installed easily.

The motor is generally used in belt-drive applications. This means that the installation

procedure should be broken into two sections, which include the mechanical installation of the

motor and its load, and the installation of electrical wiring and controls.

When the mechanical part of the installation is completed, the alignment of the motor

shaft and the load shaft should be checked. If the alignment is not true, the load will cause anundue stress on the armature bearing and there is the possibility of the load vibrating and

causing damage to it and the motor. After the alignment is checked, the tension on the belt

should also be tested. As a rule of thumb, you should have about V2 to 1/4 inch of play in the

belt when it is properly tensioned.

Several tension measurement devices are available to determine when a belt is tensioned

properly. The belt tension can also be compared to the amount of current the motor draws.

The motor must have its electrical installation completed to use this method. The motorshould be started, and if it is drawing too much current, the belt should be loosened slightly but

not enough to allow the load to slip. If the belt is slipping, it can be tightened to the point

where the motor is able to start successfully and not draw current over its rating The electrical

installation can be completed before,


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INTERFACING

INTERFACING 16x2 LCD WITH MICROCONTROLLER

A 16x2 LCD means it can display 16 characters per line and there are 2 such lines. In this LCD

each character is displayed in 5x7 pixel matrix. This LCD has two registers.

1. Command/Instruction Register- stores the command instructions given to the LCD. A

command is an instruction given to LCD to do a predefined task like initializing, clearing the

screen, setting the cursor position, controlling display etc.

2. Data Register- stores the data to be displayed on the LCD. The data is the ASCII value of the

character to be displayed on the LCD.

Commonly used LCD Command codes:

Hex

CodeCommand to LCD Instruction Register

1 Clear screen display

2 Return home

4 Decrement cursor

6 Increment cursor

E Display ON, Cursor ON

80 Force the cursor to the beginning of the 1stline

C0 Force cursor to the beginning of the 2ndline

38 Use 2 lines and 5x7 matrix


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The pin description of this module is given below:

Pin configuration:

Pin Symbol Description

1 VSS Ground 0 V

2 VCC Main power supply +5 V

3 VEE Power supply to control contrast Contrast adjustment by providing a

variable resistor through VCC

4 RS Register Select RS=0 to select Command Register

RS=1 to select Data Register

5 R/W Read/write R/W=0 to write to the register

R/W=1 to read from the register

6 EN Enable A high to low pulse (minimum

450ns wide) is given when data is

sent to data pins

7 DB0

To display letters or numbers, their

ASCII codes are sent to data pins

(with RS=1). Also instruction

command codes are sent to these

pins.

8 DB1

9 DB2

10 DB3 8-bit data pins

11 DB4

12 DB5

13 DB6

14 DB7

15 Led+ Backlight VCC +5 V

16 Led- Backlight Ground 0 V


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INTERFACING GSM MODULE WITH MICROCONTROLLER

GSM is widely used mobile communication architecture used in most of the countries. Thisproject demonstrates theinterfacing of microcontrollerAT89S52 with HyperTerminal andGSM

module. It aims to familiarize with the syntax ofAT Commandsand their Information Response

and Result Codes. The ASCII values of characters in the Information Response, Result Codes

and their syntax can be monitored by an LED array. For the basic concepts, working and

operation of AT commands and GSM module referGSM/GPRS Module.

A GSM module has an RS232 interface for serial communication with an external peripheral. In

this case, the transmit pin (Tx) of the computersSerial port is connected with the receive pin(Rx) of the GSM modules RS-232 interface. The transmit pin (Tx) of the RS-232 of GSM

module is connected to receive pin (Rx) of microcontrollers serial transmission pin. And the

serial transmit pin of the microcontroller is connected to the receive pin of the computersSerial

port.
http://www.engineersgarage.com/tutorials/at-commandshttp://www.engineersgarage.com/tutorials/at-commandshttp://www.engineersgarage.com/tutorials/at-commandshttp://www.engineersgarage.com/articles/gsm-gprs-moduleshttp://www.engineersgarage.com/articles/gsm-gprs-moduleshttp://www.engineersgarage.com/articles/gsm-gprs-moduleshttp://www.engineersgarage.com/tutorials/at-commands


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SOFTWARE USED

INTRODUCTION TO EMBEDDED C:

Embedded is the extension of c language. Embedded C is a compiler which constitutes more

build in function. By using c language it is easy to connect the comport easily. The embedded c

compiler has the bias function to connect the comport. The command from fussing kit sends

from the c program according to user wish.

HI-TEC C

HI-TEC C is a set of software that translates the program written in the C language in toexecutable machine code versions are available which compile the program for the operation

under the host operating system.

Some of the Hi-Tec features are

A simple batch file will compile, assemble and link entire program

The compiler perform strong type checking and issues warning about various constructs

which may represent programming errors

The generated code is extremely small and fast in execution

A full run time library is provided implementing all standard c input/ output and other

function

The source code for all run time routine is provided

A power full general purpose macro-assembler is provided

Programs may be generated to execute under the host operating system or customized

for installation in ROM.


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SOFTWARE DESCRIPTION

INTRODUCTION

Code Vision AVR is a C cross-compiler, Integrated Development Environment and

Automatic Program Generator designed for the Atmel AVR family of microcontrollers. The

program is designed to run under the Windows 98, Me, NT 4, 2000, XP and Vista 32bit

operating systems. The C cross-compiler implements all the elements of the ANSI C language,

as allowed by the AVR architecture, with some features added to take advantage of specificity of

the AVR architecture and the embedded system needs. The compiled COFF object files can be C

source level debugged, with variable watching, using the Atmel AVR Studio debugger. The

Integrated Development Environment (IDE) has built-in AVR Chip In-System Programmer

software that enables the automatically transfer of the program to the microcontroller chip aftersuccessful compilation/assembly. The In-System Programmer software is designed to work in

conjunction with the Atmel STK500, AVRISP, AVRISP MkII, AVR Dragon, AVRProg

(AVR910 application note), Kanda Systems STK200+, STK300, Dontronics DT006, Vogel

Elektronik VTEC-ISP, Futurlec JRAVR and MicroTronics' ATCPU, Mega2000 development

boards. For debugging embedded systems, which employ serial communication, the IDE has a

built-in Terminal.

Besides the standard C libraries, the Code Vision AVR C compiler has dedicated libraries for:

Alphanumeric LCD modules

Philips I2C bus

National Semiconductor LM75 Temperature Sensor

Philips PCF8563, PCF8583, Maxim/Dallas Semiconductor DS1302 and DS1307 Real Time

Clocks

Maxim/Dallas Semiconductor 1 Wire protocol

Maxim/Dallas Semiconductor DS1820, DS18S20 and DS18B20 Temperature Sensors

Maxim/Dallas Semiconductor DS1621 Thermometer/Thermostat

Maxim/Dallas Semiconductor DS2430 and DS2433 EEPROMs

SPI


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Power management

Delays

Gray code conversion.

CodeVisionAVR also contains the CodeWizardAVR Automatic Program Generator that allows

you to write, in a matter of minutes, all the code needed for implementing the following

functions:

External memory access setup

Chip reset source identification

Input/ Output Port initialization

External Interrupts initialization

Timers/Counters initialization

Watchdog Timer initialization

UART (USART) initialization and interrupt driven buffered serial communication

Analog Comparator initialization

ADC initialization

SPI Interface initialization

Two Wire Interface initialization

CAN Interface initialization

I2C Bus, LM75 Temperature Sensor, DS1621 Thermometer/Thermostat and PCF8563,PCF8583, DS1302, DS1307 Real Time Clocks initialization

1 Wire Bus and DS1820/DS18S20 Temperature Sensors initialization

LCD module initialization.


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Most of the top-level work is encapsulated in the Job Info class. It uses objects of class

XML File, HEX File and AVR Device to read and write XML and HEX files and to

extract device information from the Part Description Files. The two helper classes Utility

and Error Msg are used throughout the application. The part of Job Info that

communicates with the programmer does not need to know what kind of communication

channel to use. It decodes the command line and creates an instance of the required

derived class, e.g. the Serial Port class. The rest of the code just works through the

generalized Comm-Channel parent class. Currently, only a class for the PC COM port is

implemented, but to use e.g. USB or TCP/IP communication, you could derive a

specialized class from the Comm Channel base class, and add a check for this channel

type in the command line parser. The same method is used for the programmer type. The

code that operates on the programmer does not need to know which type of programmer

is attached. The Job Info class retrieves the programmer ID string and creates an

appropriate object for the specific programmer. The rest of the code operates through thegeneralized AVR Programmer interface. Currently, only classes for the Boot loader

described in the Atmel AVR910 application note and the In-System Programmer

described in the AVR910 application note are implemented. However, you could derive

your own specialized programmer from the AVR Programmer base class, and add a


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check for it in the ID string decoding part of Job Info. This design makes the application

very flexible. Future extension with other communication channels and programmer

types is an easy task.

Features

Open source C++ code

Modular design

Reads device information from the Atmel AVR Studio XML files

Supports the Boot loader in the Atmel AVR 109

Supports the In-System Programmer in the Atmel AVR910

Command-line equivalent to AVR Studio command-line tools

Expandable to other programmer types

Expandable to other communication channels, e.g. USB


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EMBEDDED C PROGRAM

Embedded C is a set of language extensions for theC Programming languageby

theC Standards committee to address commonality issues that exist between C

extensions for differentembedded systems. Historically, embedded C programming

requires nonstandard extensions to the C language in order to support exotic features such

asfixed-point arithmetic, multiple distinctmemory banks, and basicI/O operations. In

2008, the C Standards Committee extended the C language to address these issues by

providing a common standard for all implementations to adhere to. It includes a number

of features not available in normal C, such as, fixed-point arithmetic, named address

spaces, and basic I/O hardware addressing. Embedded C use most of the syntax and

semantics of standard C, e.g., main () function, variable definition, data type declaration,

conditional statements (if, switch. case), loops (while, for), functions, arrays and strings,

structures and union, bit operations, macros, unions, etc.

INTRODUCTION TO EMBEDDED C

Looking around, we find ourselves to be surrounded by various types of embedded

systems. Be it a digital camera or a mobile phone or a washing machine, all of them has

some kind of processor functioning inside it. Associated with each processor is the

embedded software. If hardware forms the body of an embedded system, embedded

processor acts as the brain, and embedded software forms its soul. It is the embedded

software which primarily governs the functioning of embedded systems.

During infancy years of microprocessor based systems, programs were developed using

assemblers and fused into the EPROMs. There used to be no mechanism to find what the

program was doing. LEDs, switches, etc. were used to check correct execution of theprogram. Some very fortunate developers had In-circuit Simulators (ICEs), but they

were too costly and were not quite reliable as well.
http://en.wikipedia.org/wiki/C_Languagehttp://en.wikipedia.org/wiki/SC22http://en.wikipedia.org/wiki/Embedded_systemshttp://en.wikipedia.org/wiki/Fixed-point_arithmetichttp://en.wikipedia.org/wiki/Memory_bankhttp://en.wikipedia.org/wiki/Input/outputhttp://en.wikipedia.org/wiki/Input/outputhttp://en.wikipedia.org/wiki/Memory_bankhttp://en.wikipedia.org/wiki/Fixed-point_arithmetichttp://en.wikipedia.org/wiki/Embedded_systemshttp://en.wikipedia.org/wiki/SC22http://en.wikipedia.org/wiki/C_Language


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As time progressed, use of microprocessor-specific assembly-only as the programming

language reduced and embedded systems moved onto C as the embedded programming

language of choice. C is the most widely used programming language for embedded

processors/controllers. Assembly is also used but mainly to implement those portions ofthe code where very high timing accuracy, code size efficiency, etc. are prime

requirements. Initially C was developed by Kernighan and Ritchie to fit into the space of

8K and to write (portable) operating systems. Originally it was implemented on UNIX

operating systems. As it was intended for operating systems development, it can

manipulate memory addresses. Also, it allowed programmers to write very compact

codes. This has given it the reputation as the language of choice for hackers too.

As assembly language programs are specific to a processor, assembly language didnt

offer portability across systems. To overcome this disadvantage, several high level

languages, including C, came up. Some other languages like PLM, Modula-2, Pascal, etc.

also came but couldnt find wide acceptance. Amongst those, C got wide acceptance for

not only embedded systems, but also for desktop applications. Even though C might have

lost its sheen as mainstream language for general purpose applications, it still is having a

strong-hold in embedded programming. Due to the wide acceptance of C in the

embedded systems, various kinds of support tools like compilers & cross-compilers, ICE,

etc. came up and all this facilitated development of embedded systems using C.

Subsequent sections will discuss what Embedded C is, features of C language,

similarities and difference between C and embedded C, and features of embedded C

programming.

EMBEDDED SYSTEMS PROGRAMMING

Embedded systems programming is different from developing applications on a desktop

computers. Key characteristics of an embedded system, when compared to PCs, are as

follows:

Embedded devices have resource constraints(limited ROM, limited RAM, limited

stack space, less processing power)


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Components used in embedded system and PCs are different; embedded systems

typically uses smaller, less power consuming components. Embedded systems are

more tied to the hardware.

Two salient features of Embedded Programming are code speed and code size. Codespeed is governed by the processing power, timing constraints, whereas code size is

governed by available program memory and use of programming language. Goal of

embedded system programming is to get maximum features in minimum space and

minimum time.

Embedded systems are programmed using different type of languages:

Machine Code

Low level language, i.e., assembly

High level language like C, C++, Java, Ada, etc.

Application level language like Visual Basic, scripts, Access, etc.

Assembly language maps mnemonic words with the binary machine codes that the

processor uses to code the instructions. Assembly language seems to be an obvious

choice for programming embedded devices. However, use of assembly language is

restricted to developing efficient codes in terms of size and speed. Also, assembly codes

lead to higher software development costs and code portability is not there. Developing

small codes are not much of a problem, but large programs/projects become increasingly

difficult to manage in assembly language. Finding good assembly programmers has also

become difficult nowadays. Hence high level languages are preferred for embedded

systems programming.

Use of C in embedded systems is driven by following advantages

It is small and reasonably simpler to learn, understand, program and debug.

C Compilers are available for almost all embedded devices in use today, and there is

a large pool of experienced C programmers.


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Unlike assembly, C has advantage of processor-independence and is not specific to

any particular microprocessor/ microcontroller or any system. This makes it convenient

for a user to develop programs that can run on most of the systems.

As C combines functionality of assembly language and features of high levellanguages, C is treated as a middle-level computer language or high level assembly

language

It is fairly efficient

It supports access to I/O and provides ease of management of large embedded

projects.

Many of these advantages are offered by other languages also, but what sets C apart from

others like Pascal, FORTRAN, etc. is the fact that it is a middle level language; it

provides direct hardware control without sacrificing benefits of high level languages.

Compared to other high level languages, C offers more flexibility because C is relatively

small, structured language; it supports low-level bit-wise data manipulation.

Compared to assembly language, C Code written is more reliable and scalable, more

portable between different platforms (with some changes). Moreover, programs

developed in C are much easier to understand, maintain and debug. Also, as they can be

developed more quickly, codes written in C offers better productivity. C is based on the

philosophy programmers know what they are doing; only the intentions are to be stated

explicitly. It is easier to write good code in C & convert it to an efficient assembly code

(using high quality compilers) rather than writing an efficient code in assembly itself.

Benefits of assembly language programming over C are negligible when we compare the

ease with which C programs are developed by programmers.

Objected oriented language, C++ is not apt for developing efficient programs in resource

constrained environments like embedded devices. Virtual functions & exception handling


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of C++ are some specific features that are not efficient in terms of space and speed in

embedded systems. Sometimes C++ is used only with very few features, very much as C.

Ada, also an object-oriented language, is different than C++. Originally designed by theU.S. DOD, it didnt gain popularity despite being accepted as an international standard

twice (Ada83 and Ada95). However, Ada language has many features that would

simplify embedded software development.

Java is another language used for embedded systems programming. It primarily finds

usage in high-end mobile phones as it offers portability across systems and is also useful

for browsing applications. Java programs require Java Virtual Machine (JVM), which

consume lot of resources. Hence it is not used for smaller embedded devices.

Dynamic C and B# are some proprietary languages which are also being used in

embedded applications.

Efficient embedded C programs must be kept small and efficient; they must be optimized

for code speed and code size. Good understanding of processor architecture embedded C

programming and debugging tools facilitate this.

DIFFERENCE BETWEEN C AND EMBEDDED C

Though C and embedded C appear different and are used in different contexts,

they have more similarities than the differences. Most of the constructs are same; the

difference lies in their applications. C is used for desktop computers, while embedded C

is for microcontroller based applications. Accordingly, C has the luxury to use resources

of a desktop PC like memor

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