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ABSTRACT
“HIGH TENSION TRANSFORMER PROTECTION” is a very important tool in the field of
power system. As we know that while working with heavy power the transformers go through very
critical stages and over heating is one of them, so it is necessary to protect the transformer from
overheating. Unless it may effect the working of the transformer and the distribution system.
A large portion of fund is expended on the transformer by the electricity department while
designing a power grid. If the transformer is not protected it posses a very high financial burden on
the concerning department.
With these views this project was conceived and designed. We have implemented our project
which can be helpful for the Electricity Board. It is easy to design our project and the logic behind
it is very simple. It includes four sections – Temperature detection section, Micro-controller
section, Relay section, Display section.
We believe our implementation ideas are a boon to the electricity board offering them a chance to
protect their transformers.
1
CHAPTER-1
INTRODUCTION
2
INTRODUCTION OF PROJECT
In this system, there is a sensor RTD which is placed in a transformer whose temperature is to be
controlled. Transformer during its operation gets heat up to prevent it from excess heat we
developed this system. The RTD senses the temperature and supplied the signal to controller which
decide or analysis the temperature and compare it with the reference temperature which is either
maximum or minimum temperature. If the temperature is more than the maximum limit then the
motor is automatically turn ON and pumps the water and split it on the Transformer. Thus the
temperature of the transformer decreases and get controlled.
Thus the High tension transformer protection is an advanced system to control the temperature of
the transformer.
3
CHAPTER-2
AIM OF THE PROJECT
4
AIM OF THE PROJECT
The main aim of this project is save the Transformer from burning. This is mainly done by the
controlling the temperature of transformer. By analyzing the temperature, our system controls the
temperature by running water on the water to remove excess heat.
Here we use a temperature sensor which can sense the temperature of the Transformer, on sensing
temperature it will forward the measured temperature to the microcontroller which control the
entire operation of controlling temperature
5
CHAPTER-3
BLOCK DIAGRAM
6
BLOCK DIAGRAM OF PROJECT
7
POWER SUPPLY
MICROCONTROLLER
SECTION
DISPLAY LCD
TEMP. SENSING OF DEVICE CONTROLLING OF
TEMPERATURE
CHAPTER-4
WORKING OF
THE PROJECT
8
WORKING OF THE PROJECT
Here we are using a PIC microcontroller that has inbuilt ADC ,through which it can sense the
analog signal and at its output generate a digital signal .since temperature sensed by the sensor
provide to the controller is in analog form so from PIC controller the work of this project become
easier .
Here we have used a temperature sensor which will sense the temperature of the transformer ,on
sensing temperature it will forward the measured temperature to the microcontroller which control
the entire operation of controlling temperature.
The microcontroller compare the sensed temperature with the reference temperature which is
either maximum or minimum temperature of the transformer and thus control it.
If the temperature of transformer increases the maximum limit, the relay ON the motor to pump
water and split on the transformer for cooling it.
9
CHAPTER-5
CIRCUIT
DIAGRAM
10
CKT DIAGRAM
11
CHAPTER 6
COMPONENT LIST
12
COMPONENT LIST
Item Quantity Part
1 2 C CER 104PF
2 2 C CER 22PF
3 1 C EL5 10M/63V
4 2 C EL5 1M/63V
5 1 C EL8 1000M/35V
6 2 RLMT 03(M)
7 3 BC547
8 1 R 2K2
9 1 R 560E
10 1 R 1% 100K
11 1 R 1% 10K
12 1 LM7805H
13 2 POT10TH 10K
14 1 XTAL 4MHZ
13
CHAPTER-7
CIRCUIT
DESCRIPTION
14
CIRCUIT DESCRIPTION
7.1 Power supply section
RLMT Connector --- It is a connector used to connect the step down transformer to the
bridge rectifier.
Bridge Rectifier --- It is a full wave rectifier used to convert ac into dc , 9-15v ac made
by transformer is converted into dc with the help of rectifier.
Capacitor: -----It is an electrolytic capacitor of rating 1000M/35V used to remove
the ripples. Capacitor is the component used to pass the ac and block the dc.
Regulator: ----LM7805 is used to give a fixed 5v regulated supply.
Capacitor: -----It is again an electrolytic capacitor 10M/65v used for filtering to give
pure dc.
Capacitor: ----- It is an ceramic capacitor used to remove the spikes generated when
frequency is high(spikes).
So the output of supply section is 5v regulated dc.
7.2 MICROCONTROLLER SECTION
Requires three connections to be successfully done for it’s operation to begin.
+5v supply: This +5v supply is required for the controller to get start which is provided
from the power supply section. This supply is provided at supply pin of the PIC
controller.
Crystal Oscillator: A crystal oscillator of 4 MHz is connected at pin no.9, and pin no.10,
to generate the frequency for the controller. The crystal oscillator works on piezoelectric
effect.The clock generated is used to determine the processing speed of the controller. Two
capacitors are also connected one end with the oscillator while the other end is connected
with the ground. As it is recommended in the book to connect two ceramic capacitor of 22
pf to stabilize the clock generated.
Reset section: It consists of an rc network consisting of capacitor and one resistance .
This section is used to reset the controller.
15
7.3LCD(Liquid Crystal Display) LCD is display screen of 16x2 which is used in this project. It has having 16 pin .
Pin no.1, pin no.16 and pin no.5 is connected to ground.
Pin no.2 and pin no.15 is connected to +5v.
Pin no.4 and pin no.6 are RS and EN respectively.
When something is to be displayed on LCD then RS should be 1
When command is generated for LCD then RS should be 0.
Pin no. 7 to 14 are connected with the microcontroller these pin are data lines. Data to be
written are sent via these data lines (D0-D7)
Pin no.3 is used for contrast control through two resistances.
7.4 RELAY SECTION : RELAY is an isolator and an electrical switch. The relay used is 12V-5A.To control the
operation of relay an NPN transistor BC547 has been used. Whenever high signal comes at
the base of NPN transistor it is switched on and whenever low arrives it is switched off.
Base of the transistor is connected with the I/O pin of the microcontroller. Base resistance
of 1k5 is connected at the base of the transistor. Whenever low is sensed at the pin of
microcontroller transistor gets off and the output of the collector becomes high and the
relay which is connected at the output of the collector becomes off. The reverse action of it
takes place when high is sensed at the pin of microcontroller.
This section also consists of pull up & pull down resistance. A 2k2 resistance is used as
pull up. In any case when more than 5v comes then pull up resistance sinks the excess
voltage & maintains 5v. If pull up is not used then the 12v of relay can damage the
processor when the transistor BC547 is on. A pull down resistor of value 2k2 is also used.
16
CHAPTER-8
STEPS FOR
MAKING PCB
17
STEPS FOR MAIKNG PCB
Prepare the layout of the circuit (positive).
Cut the photofilm (slightly bigger) of the size of the layout.
Place the layout in the photoprinter machine with the photofilm above it. Make sure that the
bromide (dark) side of the film is in contact with the layout.
Switch on the machine by pressing the push button for 5 sec.
Dip the film in the solution prepared (developer) by mixing the chemicals A & B in equal
quantities in water.
Now clean the film by placing it in the tray containing water for 1 min.
After this, dip the film in the fixer solution for 1 min. now the negative of the
Circuit is ready. Now wash it under the flowing water
Dry the negative in the photocure machine.
Take the PCB board of the size of the layout and clean it with steel wool to make the surface
smooth.
Now dip the PCB in the liquid photoresist, with the help of dip coat machine.
Now clip the PCB next to the negative in the photo cure machine, drying for approximate 10-
12 minute.
Now place the negative on the top of the PCB in the UV machine, set the timer for about 2.5
minute and switch on the UV light at the top.
Take the LPR developer in a container and rigorously move the PCB in it.
After this, wash it with water very gently.
Then apply LPR dye on it with the help of a dropper so that it is completely covered by it.
Now clamp the PCB in the etching machine that contains ferric chloride solution for about 10
minutes.
After etching, wash the PCB with water, wipe it a dry cloth softly.
Finally rub the PCB with a steel wool, and the PCB is ready.
18
CHAPTER 9
PROGRAMMING
19
PROGRAMING
LIST P=16F72 ; LIST DIRECTIVE TO DEFINE PROCESSOR
#INCLUDE <P16F72.INC> ; PROCESSOR SPECIFIC VARIABLE DEFINITIONS
#DEFINE RS PORTC,7#DEFINE EN PORTC,6
AD_RESC2 EQU 0X33
AD_RESC4 EQU 0X35
MAIN
MAINLOOPCALL DISPLAY
F_CJNG TEMPERATURE,AD_RESC4,RELAY2_ONBSF PORTC,4BSF PORTC,5
GOTO LA_2RELAY2_ON
L_CJNL TEMPERATURE,.45,GA9BCF PORTC,4BCF PORTC,5GOTO GA10
GA9:
GA10:
LA_2GOTO MAINLOOP
INTR_ADMOVWF AD_RESC2MOVWF TEMPERATURE
MOVWF AD_RESC4RETURN
DISPLAYMOVLW 0X80CALL LCD_COMMANDMOVLW "H"CALL LCD_DATAMOVLW "I"CALL LCD_DATAMOVLW "G"CALL LCD_DATAMOVLW "H"CALL LCD_DATAMOVLW " "CALL LCD_DATAMOVLW "T"CALL LCD_DATA
20
MOVLW "E"CALL LCD_DATAMOVLW "N"CALL LCD_DATAMOVLW "S"CALL LCD_DATAMOVLW "I"CALL LCD_DATAMOVLW "O"CALL LCD_DATAMOVLW "N"CALL LCD_DATA
MOVLW 0XC0CALL LCD_COMMANDMOVLW "T"CALL LCD_DATAMOVLW ":"CALL LCD_DATA
MOVLW "AD_RESC2"CALL LCD_DATAMOVLW 0XC6CALL LCD_COMMANDMOVLW "T"CALL LCD_DATAMOVLW "C"CALL LCD_DATAMOVLW "S"CALL LCD_DATAMOVLW ":"CALL LCD_DATAMOVLW "AD_RESC4"CALL LCD_DATA
RETURN
;******************************************************************************;SUBROUTINE FOR SEND LCD COMMAND ;COMMAND IN W REGISTER;******************************************************************************LCD_COMMAND
BCF RSMOVWF PORTBBSF ENBCF ENRETURN
;******************************************************************************;SUBROUTINE FOR SEND LCD DATA;******************************************************************************LCD_DATA
BSF RSMOVWF PORTBBSF ENBCF EN
21
RETURN
CHAPTER-10
SENSING UNIT
DESCRIPTION
22
SENSING UNIT DESCRIPTION
10.1 TEMPERATURE SENSOR
National Semiconductor’s LM335 IC has been used for sensing the temperature. It is an
integrated circuit sensor that can be used to measure temperature with an electrical output
proportional to the temperature (in oC). The temperature can be measured more accurately
with it than using a thermistor. The sensor circuitry is sealed and not subject to oxidation,
etc.
RTD
(RESISTANCE TEMPERAUTRE DETECTOR)
23
10.2 FEATURES OF RTD:
• Calibrated directly in ° Celsius (Centigrade)
• Linear + 10.0 mV/°C scale factor
• 0.5°C accuracy guaranteed (at +25°C)
• Rated for full −55° to +150°C range
• Suitable for remote applications
• Low cost due to wafer-level trimming
• Operates from 4 to 30 volts
• Less than 60 μA current drain
10.3 FUNCTIONAL DESCRIPTION:
The sensor has a sensitivity of 10mV / oC.
• The output of LM35 is amplified using a single power supply (+5V) op-amp.
• The op-amp is designed to have a gain of 5.
• The circuitry measures temperatures with a resolution of up to 0.5 degree Celsius.
• The output voltage is converted to temperature by a simple conversion factor.
The general equation used to convert output voltage to temperature is:
Temperature ( oC) = (Vout * 100 ) / 5 oC …(4.4)
So if Vout is 5V, then, Temperature = 100 oC
The output voltage varies linearly with temperature.
24
Temperature sensor readings
FORMULA:
Temperature ( Oc ) = (Vout/5) *100( Oc/V)
Temperature Sensor Readings
25
CHAPTER-11
MICRO-
CONTROLLER
UNIT
26
MICROCONTROLLER UNIT
11.1 CRITERIA FOR CHOOSING A MICROCONTROLLER
The basic criteria for choosing a microcontroller suitable for the application are:
The first and foremost criterion is that it must meet the task at hand efficiently and cost
effectively. In analyzing the needs of a microcontroller-based project, it is seen whether an
8- bit, 16-bit or 32-bit microcontroller can best handle the computing needs of the task
most effectively. Among the other considerations in this category are:
Speed: The highest speed that the microcontroller supports.
Packaging: It may be a 28-pin DIP (dual inline package) or a QFP (quad flat package), or
some other packaging format. This is important in terms of space, assembling, and
prototyping the end product.
Power consumption: This is especially critical for battery-powered products.
The number of I/O pins and the timer on the chip.
How easy it is to upgrade to higher –performance or lower consumption versions.
Cost per unit: This is important in terms of the final cost of the product in which a
microcontroller is used.
The second criterion in choosing a microcontroller is how easy it is to develop products
around it. Key considerations include the availability of an assembler, debugger, compiler,
technical support.
The third criterion in choosing a microcontroller is its ready availability in needed
quantities both now and in the future.
11.2 DESCRIPTION
This powerful (200 nanosecond instruction execution) yet easy-to-program (only 35 single
word instructions) CMOS FLASH-based 8-bit microcontroller packs Microchip's powerful
PIC® architecture into an 28-pin package and is upwards compatible with the PIC16C5X,
PIC12CXXX and PIC16C7X devices. The PIC16F72 features 5 channels of 8-bit Analog-
to-Digital (A/D) converter with 2 additional timers, capture/compare/PWM function and
the synchronous serial port can be configured as either 3-wire Serial Peripheral Interface
(SPI™) or the 2-wire Inter-Integrated Circuit (I²C™) bus. All of these features make it
27
ideal for more advanced level A/D applications in automotive, industrial, appliances and
consumer applications.
11.3 DEVICE SPECIFICATION
High Performance RISC CPU:
• Only 35 single word instructions to learn
• All single cycle instructions except for program branches, which are two-cycle
• Operating speed: DC - 20 MHz clock input DC - 200 ns instruction cycle
• 2K x 14 words of Program Memory, 128 x 8 bytes of Data Memory (RAM)
• Pin out compatible to PIC16C72/72A and PIC16F872
• Interrupt capability
• Eight-level deep hardware stack
• Direct, Indirect and Relative Addressing modes
Peripheral Features:
• High Sink/Source Current: 25 mA
• Timer0: 8-bit timer/counter with 8-bit prescaler
• Timer1: 16-bit timer/counter with prescaler, can be incremented during SLEEP via external crystal/clock
• Timer2: 8-bit timer/counter with 8-bit period register, prescaler and postscaler
• Capture, Compare, PWM (CCP) module
- Capture is 16-bit, maximum resolution is 12.5 ns
- Compare is 16-bit, maximum resolution is 200 ns
- PWM maximum resolution is 10-bit
• 8-bit, 5-channel analog-to-digital converter
• Synchronous Serial Port (SSP) with SPI™ (Master/Slave) and I2C™ (Slave)
• Brown-out detection circuitry for Brown-out Reset (BOR)
28
CMOS Technology:
• Low power, high speed CMOS FLASH technology
• Fully static design
• Wide operating voltage range: 2.0V to 5.5V
• Industrial temperature range
• Low power consumption:
- < 0.6 mA typical @ 3V, 4 MHz
- 20 micro A typical @ 3V, 32 kHz
- < 1 micro A typical standby current
Special Microcontroller Features:
• 1,000 erase/write cycle FLASH program memory typical
• Power-on Reset (POR), Power-up Timer (PWRT) and Oscillator Start-up Timer (OST)
• Watchdog Timer (WDT) with its own on-chip RC oscillator for reliable operation
• Programmable code protection
• Power saving SLEEP mode
• Selectable oscillator options
• In-Circuit Serial Programming™ (ICSP™) via 2 pins
• Processor read access to program memory
29
11.4 PIN DIAGRAM OF PIC16F72
30
11.5 BLOCK DIAGRAM OF MICROCONTROLLER
31
11.6 INSTRUCTION SET SUMMARY
Each PIC16F72 instruction is a 14-bit word divided into an OPCODE that specifies the
instruction type and one or more operands that further specify the operation of the
instruction. The PIC16F72 instruction set summary in Table below lists byte-oriented, bit-
oriented, and literal and control operations. Table below shows the opcode field
descriptions. For byte-oriented instructions, ‘f’ represents a file register designator and ‘d’
represents a destination designator. The file register designator specifies which file register
is to be used by the instruction. The destination designator specifies where the result of the
operation is to be placed. If ‘d’ is zero, the result is placed in the W register. If ‘d’ is one,
the result is placed in the file register specified in the instruction. For bit-oriented
instructions, ‘b’ represents a bit field designator which selects the number of the bit
affected by the operation, while ‘f’ represents the number of the file in which the bit is
located. For literal and control operations, ‘k’ represents an eight or eleven-bit constant or
literal value.
The instruction set is highly orthogonal and is grouped into three basic categories:
• Byte-oriented operations
• Bit-oriented operations
• Literal and control operations
All instructions are executed within one single instruction cycle, unless a conditional test is
true or the program counter is changed as a result of an instruction. In this case, the
execution takes two instruction cycles, with the second cycle executed as a NOP. One
instruction cycle consists of four oscillator periods. Thus, for an oscillator frequency of 4
MHz, the normal instruction execution time is 1 s. If a conditional test is true, or the
program counter is changed as a result of an instruction, the instruction execution time is
2S
32
11.7 GENERAL FORMAT FOR INSTRUCTION
33
CHAPTER-12
COMPONENT
DESCRIPTION
34
COMPONENT DESCRIPTION
12.1 Transformers
CURRENT TRANSFORMER: A current transformer is a type of transformer that is
usually placed in the main circuit to step down a high current circuit to drive a low current
device, usually a low current meter or resistor. It is also very useful in measuring or
monitoring high current, high voltage and high power circuits.
POTENTIAL TRANSFORMER
THREE-PHASE POLE-MOUNTED STEP-DOWN TRANSFORMER.
A transformer is a device that transfers electrical energy from one circuit to another by
magnetic coupling without requiring relative motion between its parts. It usually comprises
two or more coupled windings, and, in most cases, a core to concentrate magnetic flux. A
transformer operates from the application of an alternating voltage to one winding, which
creates a time-varying magnetic flux in the core. This varying flux induces a voltage in the other windings. Varying the relative number of turns between primary and secondary windings
35
determines the ratio of the input and output voltages, thus transforming the voltage by stepping it
up or down between circuits.
BASIC PRINCIPLE: The principles of the transformer are illustrated by consideration of a
hypothetical ideal transformer consisting of two windings of zero resistance around a core of
negligible reluctance. A voltage applied to the primary winding causes a current, which develops a
magnetomotive force (MMF) in the core. The current required to create the MMF is termed the
magnetising current; in the ideal transformer it is considered to be negligible. The MMF drives flux
around the magnetic circuit of the core.
The ideal transformer as a circuit element
An electromotive force (EMF) is induced across each winding, an effect known as mutual
inductance. The windings in the ideal transformer have no resistance and so the EMFs are equal in
magnitude to the measured terminal voltages. In accordance with Faraday's law of induction, they
are proportional to the rate of change of flux:
and
EMF induced in primary and secondary windings
where:
and are the induced EMFs across primary and secondary windings,36
and are the numbers of turns in the primary and secondary windings,
and are the time derivatives of the flux linking the primary and secondary windings.
In the ideal transformer, all flux produced by the primary winding also links the secondary, and so
, from which the well-known transformer equation follows:
Transformer Equation
The ratio of primary to secondary voltage is therefore the same as the ratio of the number of turns;
alternatively, that the volts-per-turn is the same in both windings. The conditions that determine
Transformer working in STEP UP or STEP DOWN mode are:
Ns > Np Condition for STEP UP
Ns < Np Condition for STEP DOWN
12.2 RECTIFIER
A bridge rectifier is an arrangement of four diodes connected in a bridge circuit as shown
below, that provides the same polarity of output voltage for any polarity of the input
voltage. When used in its most common application, for conversion of alternating current
(AC) input into direct current (DC) output, it is known as a bridge rectifier. The bridge
rectifier provides full wave rectification from a two wire AC input (saving the cost of a
centre tapped transformer) but has two diode drops rather than one reducing efficiency
over a centre tap based design for the same output voltage.
37
The essential feature of this arrangement is that for both polarities of the voltage at the bridge input,
the polarity of the output is constant.
BASIC OPERATION:
When the input connected at the left corner of the diamond is positive with respect to the one
connected at the right hand corner, current flows to the right along the upper coloured path to the
output, and returns to the input supply via the lower one.
When the right hand corner is positive relative to the left hand corner, current flows along
the upper coloured path and returns to the supply via the lower coloured path.
38
AC, half-wave and full wave rectified signals
In each case, the upper right output remains positive with respect to the lower right one. Since this
is true whether the input is AC or DC, this circuit not only produces DC power when supplied with
AC power: it also can provide what is sometimes called "reverse polarity protection". That is, it
permits normal functioning when batteries are installed backwards or DC input-power supply
wiring "has its wires crossed" (and protects the circuitry it powers against damage that might occur
without this circuit in place).
39
Prior to availability of integrated electronics, such a bridge rectifier was always constructed from
discrete components. Since about 1950, a single four-terminal component containing the four
diodes connected in the bridge configuration became a standard commercial component and is now
available with various voltage and current ratings.
12.3 LM317 (3-TERMINAL ADJUSTABLE REGULATOR)
The LM317 is an adjustable three-terminal positive-voltage regulator capable of supplying
more than 1.5 A over an output-voltage range of 1.2 V to 37 V. It is exceptionally easy to
use and requires only two external resistors to set the output voltage. Furthermore, both
line and load regulation are better than standard fixed regulators. The LM317 is packaged
in the KC (TO-220AB) and KTE packages, which are easy to handle and use. In addition
to having higher performance than fixed regulators, this device includes on-chip current
limiting, thermal overload protection, and safe-operating-area protection. All overload
protection remains fully functional, even if the ADJUST terminal is disconnected.
Figure 16: TOP IC view of LM 317
40
The LM317 is versatile in its applications, including uses in programmable output
regulation and local on-card regulation. Or, by connecting a fixed resistor between the
ADJUST and OUTPUT terminals, the LM317 can function as a precision current regulator.
An optional output capacitor can be added to improve transient response. The ADJUST
terminal can be bypassed to achieve very high ripple-rejection ratios, which are difficult to
achieve with standard three-terminal regulators. The LM317 is characterized for operation
over the virtual junction temperature range of 0°C to 125°C.
Adjustable Voltage Regulator
12.4 LIQUID CRYSTAL DISPLAY(LCD)
A liquid crystal display (commonly abbreviated LCD) is a thin, flat display device made up of
any number of colour or monochrome pixels arrayed in front of a light source or reflector. It is
prized by engineers because it uses very small amounts of electric power, and is therefore suitable
for use in battery-powered electronic devices. Each pixel of an LCD consists of a layer of
perpendicular molecules aligned between two transparent electrodes, and two polarizing filters, the
axes of polarity of which are perpendicular to each other. With no liquid crystal between the
41
polarizing filters, light passing through one filter would be blocked by the electrodes. The surfaces
of the electrodes that are in contact with the liquid crystal material are treated so as to align the
liquid crystal molecules in a particular direction. This treatment typically consists of a thin polymer
layer that is unidirectionally rubbed using a cloth (the direction of the liquid crystal alignment is
defined by the direction of rubbing). Before applying an electric field, the orientation of the liquid
crystal molecules is determined by the alignment at the surfaces. In a twisted nematic device (the
most common liquid crystal device), the surface alignment directions at the two electrodes are
perpendicular, and so the molecules arrange themselves in a helical structure, or twist. Because the
liquid crystal material is birefringent, light passing through one polarizing filter is rotated by the
liquid crystal helix as it passes through the liquid crystal layer, allowing it to pass through the
second polarized filter. Half of the light is absorbed by the first polarizing filter, but otherwise the
entire assembly is transparent. When a voltage is applied across the electrodes, a torque acts to
align the liquid crystal molecules parallel to the electric field, distorting the helical structure (this is
resisted by elastic forces since the molecules are constrained at the surfaces). This reduces the
rotation of the polarization of the incident light, and the device appears gray. If the applied voltage
is large enough, the liquid crystal molecules are completely untwisted and the polarization of the
incident light is not rotated at all as it passes through the liquid crystal layer. This light will then be
polarized perpendicular to the second filter, and thus be completely blocked and the pixel will
appear black. By controlling the voltage applied across the liquid crystal layer in each pixel, light
can be allowed to pass through in varying amounts, correspondingly illuminating the pixel. With a
twisted nematic liquid crystal device it is usual to operate the device between crossed polarizers,
such that it appears bright with no applied voltage. With this setup, the dark voltage-on state is
uniform. The device can be operated between parallel polarizers, in which case the bright and dark
states are reversed.
Both the liquid crystal material and the alignment layer material contain ionic compounds. If an
electric field of one particular polarity is applied for a long period of time, this ionic material is
attracted to the surfaces and degrades the device performance. This is avoided by applying either an
alternating current, or by reversing the polarity of the electric field as the device is addressed (the
response of the liquid crystal layer is identical, regardless of the polarity of the applied field). When
a large number of pixels is required in a display, it is not feasible to drive each directly since then
each pixel would require independent electrodes. Instead, the display is multiplexed. In a
multiplexed display, electrodes on one side of the display are grouped and wired together (typically
in columns), and each group gets its own voltage source. On the other side, the electrodes are also
grouped (typically in rows), with each group getting a voltage sink. The groups are designed so 42
each pixel has unique, unshared combination of source and sink. The electronics or the software
driving the electronics then turns on sinks in sequence, and drives sources for the pixels of each
sink.
12.4.1CLEARING THE DISPLAY:
When the LCD is first initialized, the screen should automatically be cleared by the 44780
controller. However, it's always a good idea to do things yourself so that you can be completely
sure that the display is the way you want it. Thus, it's not a bad idea to clear the screen as the very
first opreation after the LCD has been initialiezd.
An LCD command exists to accomplish this function. Not suprisingly, it is the command 01h.
Since clearing the screen is a function we very likely will wish to call more than once, it's a good
idea to make it a subroutine:
CLEAR_LCD:
CLR RS
MOV DATA, #01h
SETB EN
CLR EN
LCALL WAIT_LCD
RET
How that we've written a "Clear Screen" routine, we may clear the LCD at any time by simply
executing an LCALL CLEAR_LCD.
43
12.4.2CURSOR POSITIONING
The above "Hello World" program is simplistic in the sense that it prints its text in the upper left-
hand corner of the screen. However, what if we wanted to display the word "Hello" in the upper
left-hand corner but wanted to display the word "World" on the second line at the tenth character?
This sounds simple--and actually, it is simple. However, it requires a little more understanding of
the design of the LCD.
The 44780 contains a certain amount of memory which is assigned to the display. All the text we
write to the 44780 is stored in this memory, and the 44780 subsequently reads this memory to
display the text on the LCD itself. This memory can be represented with the following "memory
map":
Memory Mapping in LCD
12.5 RELAY
44
CIRCUIT SYMBOL FOR A RELAY
Relays
A relay is an electrically operated switch. Current flowing through the coil of the relay creates a
magnetic field, which attracts a lever and changes the switch contacts. The coil current can be on or
off so relays have two switch positions and they are double throw (changeover) switches.
Relays allow one circuit to switch a second circuit that can be completely separate from the first.
For example a low voltage battery circuit can use a relay to switch a 230V AC mains circuit. There
is no electrical connection inside the relay between the two circuits, the link is magnetic and
mechanical.
The coil of a relay passes a relatively large current, typically 30mA for a 12V relay, but it can be as
much as 100mA for relays designed to operate from lower voltages. Most ICs (chips) cannot
provide this current and a transistor is usually used to amplify the small IC current to the larger
value required for the relay coil. The maximum output current for the popular 555 timer IC is
200mA so these devices can supply relay coils directly without amplification.
Relays are usually SPDT or DPDT but they can have many more sets of switch contacts, for
example relays with 4 sets of changeover contacts are readily available. For further information
about switch contacts and the terms used to describe them please see the page on switches.
Most relays are designed for PCB mounting but you can solder wires directly to the pins providing
you take care to avoid melting the plastic case of the relay.
The supplier's catalogue should show you the relay's connections. The coil will be obvious and it
may be connected either way round. Relay coils produce brief high voltage 'spikes' when they are
switched off and this can destroy transistors and ICs in the circuit. To prevent damage you must
connect a protection diode across the relay coil.
The animated picture shows a working relay with its coil and switch contacts. You can see a lever
on the left being attracted by magnetism when the coil is switched on. This lever moves the switch
contacts. There is one set of contacts (SPDT) in the foreground and another behind them, making
the relay DPDT.
The relay's switch connections are usually labeled COM, NC and NO:
COM = Common, always connect to this, it is the moving part of the switch.
NC = Normally Closed, COM is connected to this when the relay coil is off.
NO = Normally Open, COM is connected to this when the relay coil is on. 45
Connect to COM and NO if you want the switched circuit to be on when the relay coil is on.
Connect to COM and NC if you want the switched circuit to be on when the relay coil is off.
12.5.1CHOOSING A RELAYYou need to consider several features when choosing a relay:
Physical size and pin arrangement
If you are choosing a relay for an existing PCB you will need to ensure that its dimensions and pin
arrangement are suitable. You should find this information in the supplier's catalogue.
Coil voltage
The relay's coil voltage rating and resistance must suit the circuit powering the relay coil. Many
relays have a coil rated for a 12V supply but 5V and 24V relays are also readily available. Some
relays operate perfectly well with a supply voltage which is a little lower than their rated value.
Coil resistance
The circuit must be able to supply the current required by the relay coil. You can use Ohm's law to
calculate the current:
Relay coil current =Supply voltage/Coil resistance
For example: A 12V supply relay with a coil resistance of 400 passes a current of 30mA. This is
OK for a 555 timer IC (maximum output current 200mA), but it is too much for most ICs and they
will require a transistor to amplify the current.
Switch ratings (voltage and current)
The relay's switch contacts must be suitable for the circuit they are to control. You will need to
check the voltage and current ratings. Note that the voltage rating is usually higher for AC, for
example: "5A at 24V DC or 125V AC".
12.6 CRYSTAL OSCILLATOR
It is often required to produce a signal whose frequency or pulse rate is very stable and exactly
known. This is important in any application where anything to do with time or exact measurement
is
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crucial. It is relatively simple to make an oscillator that produces some sort of a signal, but another
matter to produce one of relatively precise frequency and stability. AM radio stations must have a
carrier frequency accurate within 10Hz of its assigned frequency, which may be from 530 to 1710
kHz. SSB radio systems used in the HF range (2-30 MHz) must be within 50 Hz of channel
frequency for acceptable voice quality, and within 10 Hz for best results. Some digital modes used
in weak signal communication may require frequency stability of less than 1 Hz within a period of
several minutes. The carrier frequency must be known to fractions of a hertz in some cases. An
ordinary quartz watch must have an oscillator accurate to better than a few parts per million. One
part per million will result in an error of slightly less than one half second a day, which would be
about 3 minutes a year. This might not sound like much, but an error of 10 parts per million would
result in an error of about a half an hour per year. A clock such as this would need resetting about
once a month, and more often if you are the punctual type. A programmed VCR with a clock this
far off could miss the recording of part of a TV show. Narrow band SSB communications at VHF
and UHF frequencies still need 50 Hz frequency accuracy. At 440 MHz, this is slightly more than
0.1 part per million.
Ordinary L-C oscillators using conventional inductors and capacitors can achieve typically 0.01 to
0.1 percent frequency stability, about 100 to 1000 Hz at 1 MHz. This is OK for AM and FM
broadcast receiver applications and in other low-end analog receivers not requiring high tuning
accuracy. By careful design and component selection, and with rugged mechanical
construction, .01 to 0.001%, or even better (.0005%) stability can be achieved. The better figures
will undoubtedly employ temperature compensation components and regulated power supplies,
together with environmental control (good ventilation and ambient temperature regulation) and
“battleship” mechanical construction. This has been done in some communications receivers used
by the military and commercial HF communication receivers built in the 1950-1965 era, before the
widespread use of digital frequency synthesis. But these receivers were extremely expensive, large,
and heavy. Many modern consumer grade AM, FM, and shortwave receivers employing crystal
controlled digital frequency synthesis will do as well or better from a frequency stability
standpoint.
An oscillator is basically an amplifier and a frequency selective feedback network (Fig 1). When, at
a particular frequency, the loop gain is unity or more, and the total phaseshift at this frequency is
zero, or some multiple of 360 degrees, the condition for oscillation is satisfied, and the circuit will
produce a periodic waveform of this frequency. This is usually a sine wave, or square wave, but
triangles, impulses, or other waveforms can be produced. In fact, several different waveforms often
are simultaneously produced by the same circuit, at different points. It is also possible to have
several frequencies produced as well, although this is generally undesirable.47
12.7 CAPACITOR
A capacitor or condenser is a passive electronic component consisting of a pair of conductors
separated by a dielectric (insulator). When a potential difference (voltage) exists across the
conductors, an electric field is present in the dielectric. This field stores energy and produces a
mechanical force between the conductors. The effect is greatest when there is a narrow separation
between large areas of conductor, hence capacitor conductors are often called plates.
An ideal capacitor is characterized by a single constant value, capacitance, which is measured in
farads. This is the ratio of the electric charge on each conductor to the potential difference between
them. In practice, the dielectric between the plates passes a small amount of leakage current. The
conductors and leads introduce an equivalent series resistance and the dielectric has an electric field
strength limit resulting in a breakdown voltage.
Capacitors are widely used in electronic circuits to block the flow of direct current while allowing
alternating current to pass, to filter out interference, to smooth the output of power supplies, and for
many other purposes. They are used in resonant circuits in radio frequency equipment to select
particular frequencies from a signal with many frequencies.
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THEORY OF OPERATION
Charge separation in a parallel-plate capacitor causes an internal electric field. A dielectric (orange)
reduces the field and increases the capacitance.
A capacitor consists of two conductors separated by a non-conductive region.The non-conductive
substance is called the dielectric medium, although this may also mean a vacuum or a
semiconductor depletion region chemically identical to the conductors. A capacitor is assumed to
be self-contained and isolated, with no net electric charge and no influence from an external
electric field. The conductors thus contain equal and opposite charges on their facing surfaces, and
the dielectric contains an electric field. The capacitor is a reasonably general model for electric
fields within electric circuits.
An ideal capacitor is wholly characterized by a constant capacitance C, defined as the ratio of
charge ±Q on each conductor to the voltage V between them
Sometimes charge buildup affects the mechanics of the capacitor, causing the capacitance to vary.
In this case, capacitance is defined in terms of incremental changes:
In SI units, a capacitance of one farad means that one coulomb of charge on each conductor causes
a voltage of one volt across the device.
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12.8 RESISTOR
Resistors are used to limit the value of current in a circuit. Resistors offer opposition to the flow of
current. They are expressed in ohms for which the symbol is ‘’. Resistors are broadly classified as
(1) Fixed Resistors
(2) Variable Resistors
12.8.1 Fixed Resistors :
The most common of low wattage, fixed type resistors is the molded-carbon composition resistor.
The resistive material is of carbon clay composition. The leads are made of tinned copper.
Resistors of this type are readily available in value ranging from few ohms to about 20M, having
a tolerance range of 5 to 20%. They are quite inexpensive. The relative size of all fixed resistors
changes with the wattage rating.
Another variety of carbon composition resistors is the metalized type. It is made by
deposition a homogeneous film of pure carbon over a glass, ceramic or other insulating core. This
type of film-resistor is sometimes called the precision type, since it can be obtained with an
accuracy of 1%.
Lead Tinned Copper Material
Colour Coding Molded Carbon Clay Composition
12.9 TRANSISTORS
A transistor is an active device. It consists of two PN junctions formed by sandwiching either p-
type or n-type semiconductor between a pair of opposite types.
There are two types of transistor:
n-p-n transistor
p-n-p transistor
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An n-p-n transistor is composed of two n-type semiconductors separated by a thin section of p-
type. However a p-n-p type semiconductor is formed by two p-sections separated by a thin section
of n-type.
Transistor has two pn junctions one junction is forward biased and other is reversed biased.
The forward junction has a low resistance path whereas a reverse biased junction has a high
resistance path. The weak signal is introduced in the low resistance circuit and output is taken from
the high resistance circuit. Therefore a transistor transfers a signal from a low resistance to high
resistance. Transistor has three sections of doped semiconductors. The section on one side is
emitter and section on the opposite side is collector. The middle section is base.
Emitter : The section on one side that supplies charge carriers is called emitter. The
emitter is always forward biased w.r.t. base.
Collector : The section on the other side that collects the charge is called collector. The
collector is always reversed biased.
Base : The middle section which forms two pn-junctions between the emitter and collector
is called base.
A transistor raises the strength of a weak signal and thus acts as an amplifier. The weak signal is
applied between emitter-base junction and output is taken across the load Rc connected in the
collector circuit. The collector current flowing through a high load resistance Rc produces a large
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voltage across it. Thus a weak signal applied in the input appears in the amplified form in the
collector circuit.
12.10 CONNECTORS
Connectors are basically used for interface between two. Here we use connectors for having interface between PCB and 8051 Microprocessor Kit.
There are two types of connectors they are male and female. The one, which is with pins inside, is female and other is male.
These connectors are having bus wires with them for connection.
For high frequency operation the average circumference of a coaxial cable must be limited to about one wavelength, in order to reduce multimodal propagation and eliminate erratic reflection coefficients, power losses, and signal distortion. The standardization of coaxial connectors during World War II was mandatory for microwave operation to maintain a low reflection coefficient or a low voltage standing wave ratio.
Seven types of microwave coaxial connectors are as follows:
1.APC-3.5
2.APC-7
3.BNC
4.SMA
5.SMC
6.TNC
7.Type N
12.11 LED (LIGHT EMITTING DIODE)
A junction diode, such as LED, can emit light or exhibit electro luminescence. Electro
luminescence is obtained by injecting minority carriers into the region of a pn junction where
radiative transition takes place. In radiative transition, there is a transition of electron from the
conduction band to the valence band, which is made possibly by emission of a photon. Thus,
emitted light comes from the hole electron recombination. What is required is that electrons should
make a transition from higher energy level to lower energy level releasing photon of wavelength
corresponding to the energy difference associated with this transition. In LED the supply of high-
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energy electron is provided by forward biasing the diode, thus injecting electrons into the n-region
and holes into p-region.
The pn junction of LED is made from heavily doped material. On forward bias condition,
majority carriers from both sides of the junction cross the potential barrier and enter the opposite
side where they are then minority carrier and cause local minority carrier population to be larger
than normal. This is termed as minority injection. These excess minority carrier diffuse away from
the junction and recombine with majority carriers.
In LED, every injected electron takes part in a radiative recombination and hence gives rise to
an emitted photon. Under reverse bias no carrier injection takes place and consequently no photon
is emitted. For direct transition from conduction band to valence band the emission wavelength.
In practice, every electron does not take part in radiative recombination and hence, the
efficiency of the device may be described in terms of the quantum efficiency which is defined as
the rate of emission of photons divided by the rate of supply of electrons. The number of radiative
recombination, that take place, is usually proportional to the carrier injection rate and hence to the
total current flowing.
12.11.1 LED MaterialsOne of the first materials used for LED is GaAs. This is a direct band gap material, i.e., it exhibits
very high probability of direct transition of electron from conduction band to valence band. GaAs
has E= 1.44 eV. This works in the infrared region.
GaP and GaAsP are higher band gap materials. Gallium phosphide is an indirect band gap
semiconductor and has poor efficiency because band to band transitions are not normally observed.
Gallium Arsenide Phosphide is a tertiary alloy. This material has a special feature in that it changes
from being direct band gap material.
Blue LEDs are of recent origin. The wide band gap materials such as GaN are one of the most
promising LEDs for blue and green emission. Infrared LEDs are suitable for optical coupler
applications.
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12.11.2 ADVANTAGES OF LEDs: Low operating voltage, current, and power consumption makes Leds compatible with
electronic drive circuits. This also makes easier interfacing as compared to filament
incandescent and electric discharge lamps.
The rugged, sealed packages developed for LEDs exhibit high resistance to mechanical
shock and vibration and allow LEDs to be used in severe environmental conditions where
other light sources would fail.
LED fabrication from solid-state materials ensures a longer operating lifetime, thereby
improving overall reliability and lowering maintenance costs of the equipment in which
they are installed.
The range of available LED colours-from red to orange, yellow, and green-provides the
designer with added versatility.
LEDs have low inherent noise levels and also high immunity to externally generated noise.
Circuit response of LEDs is fast and stable, without surge currents or the prior “warm-up”,
period required by filament light sources.
LEDs exhibit linearity of radiant power output with forward current over a wide range.
12.12 BUZZER
It is an electronic signaling device which produces buzzing sound. It is commonly used in
automobiles, phone alarm systems and household appliances. Buzzers work in the same manner as
an alarm works. They are generally equipped with sensors or switches connected to a control unit
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and the control unit illuminates a light on the appropriate button or control panel, and sound a
warning in the form of a continuous or intermittent buzzing or beeping sound.
The word "buzzer" comes from the rasping noise that buzzers made when they were
electromechanical devices, operated from stepped-down AC line voltage at 50 or 60 cycles.
Typical uses of buzzers and beepers include alarms, timers and confirmation of user input such as a
mouse click or keystroke.
12.13 DIODE
ACTIVE COMPONENT-
Active component are those component for not any other component are used its operation. I used
in this project only function diode, these component description are described as bellow.
SEMICONDUCTOR DIODE-
A PN junctions is known as a semiconductor or crystal diode.A crystal diode has two terminal
when it is connected in a circuit one thing is decide is weather a diode is forward or reversed
biased. There is a easy rule to ascertain it. If the external CKT is trying to push the conventional
current in the direction of error, the diode is forward biased. One the other hand if the conventional
current is trying is trying to flow opposite the error head, the diode is reversed biased putting in
simple words.
If arrowhead of diode symbol is positive W.R.T Bar of the symbol, the diode is forward biased.
The arrowhead of diode symbol is negative W.R.T bar , the diode is the reverse bias.
When we used crystal diode it is often necessary to know that which end is arrowhead and which
end is bar. So following method are available.
Some manufactures actually point the symbol on the body of the diode e. g By127 by 11 4 crystal
diode manufacture by b e b.
Sometimes red and blue marks are on the body of the crystal diode. Red mark do not arrow where’s
blue mark indicates bar e .g oa80 crystal diode.
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12.12.1 ZENER DIODE-
It has been already discussed that when the reverse bias on a crystal diode is increased a critical
voltage, called break down voltage. The break down or zener voltage depends upon the amount of
doping. If the diode is heavily doped depletion layer will be thin and consequently the break down
of he junction will occur at a lower reverse voltage. On the other hand, a lightly doped diode has a
higher break down voltage, it is called zener diode
.
A properly doped crystal diode, which has a sharped break down voltage, is known as a zenor
diode.
CONCLUSION:
We have successfully completed the project of high tension transformer protection . Through this
project we conclude that the temperature of the transformer can control automatically using
temperature sensor and microcontroller.
Microcontroller successfully done the cooling of the transformer in case of increase in
temperature of the transformer. The developing of this project has been a learning experience
for all team members and would prove as a milestone in their academic career. The achievement of
this project are
i. The project has achieved its set target well in “Time” and “Budget”.56
ii. Based on cutting edge technology called Embedded development which is niche in the
market today and its future is much bright.
iii. The product developed is ready for implementation and can bring financial benefits too
by sale in the market.
So, we conclude that the high tension transformer is still far away from the perfect, but we believe
we have laid the groundwork to enable it to improve out of sight.
References
1. Mazedi, The 8051 Microcontroller and Embedded Systems, Prentice Hall, 1ST Edition
2. Kenneth J. Ayala, The 8051 Microcontroller, Penram International Publishing,1996, 2 nd
Edition
3. Some Websites :
www.alldatasheets.com
www.datasheetcatalog.com
www.electronicscircuits.com
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