OVERHEAD LINE BROKEN CONDUCTOR DETECTION
CHAPTER 1INTRODUCTION
1.1 EMBEDDED SYSTEMS
Embedded systems are designed to do some specific task, rather
than be a general-purpose computer for multiple tasks. Some also
have real time performance constraints that must be met, for reason
such as safety and usability; others may have low or no performance
requirements, allowing the system hardware to be simplified to
reduce costs.Anembedded systemis not always a separate block - very
often it is physically built-in to the device it is controlling.
The software written for embedded systems is often calledfirmware,
and is stored in read-only memory or flash convector chips rather
than a disk drive. It often runs with limited computer hardware
resources: small or no keyboard, screen, and little memory.
Wireless communication has become an important feature for
commercialproductsand a popular research topic within the last ten
years. There are now more mobile phone subscriptions than
wired-line subscriptions. Lately, one area of commercial interest
has been low-cost, low-power, and short-distance wireless
communication used for personal wireless networks." Technology
advancements are providing smaller and more cost effective devices
for integrating computational processing, wireless communication,
and a host of other functionalities. These embedded communications
devices will be integrated into applications ranging from homeland
security to industry automation andmonitoring. They will also
enable custom tailored engineering solutions, creating a
revolutionary way of disseminating and processing information. With
new technologies and devices comenew businessactivities, and the
need for employees in these technological areas. Engineers who have
knowledge of embedded systems and wireless communications will be
in high demand. Unfortunately, there are few adorable environments
available for development and classroom use, so students often do
not learn about these technologies during hands-on lab exercises.
The communication mediums were twisted pair, optical fiber,
infrared, and generally wireless radio.
ABSTRACTOverhead line distribution system is generally used in
rural area with a free space. In case of broken conductor, the
pedestrian may be injured from high-voltage conductor, if the
system cannot detect and make a command to open the circuit
breaker. In this paper, we apply the principle of time shifting to
detect the broken line conductor on the source side with a
variation of fault impedance compared with the ratio of negative to
positive sequence current. When the fault is detected the
Microcontroller Operates the Relay Device. The Protective alarm is
connected to Relay and Intimates the Broken Conductor Information
and Fault Information. The studied results were taken from the
Project Demo Kit and the Results are found Satisfactory
CHAPTER 2
LITERATURE REVIEW
1. Service-oriented Advanced Metering Infrastructure for Smart
Grids
AbstractAdvanced Metering Infrastructure (AMI) enables smart
grids to involve power consumers in the business process of power
generation, transmission, distribution and consumption. However,
the participant of consumers challenges the current power systems
with system integration and cooperation and security issues. In
this paper, we introduce a service-oriented approach to AMI aiming
at solving the intercommunication problem and meanwhile providing a
trust and secure environment for smart grids. In this approach
heterogeneous systems expose services to the network. System
integration and cooperation are done through service composition. A
generic service interfacing method is designed to develop
standardized services for heterogeneous power systems. Moreover,
role-based access control mechanism is used to guarantee the secure
access to smart grids.
2. Functional Analysis of Advanced Metering Infrastructure in
Smart Grid
Abstract-Today, smart grid has been widely discussed in
worldwide. As advanced metering infrastructure is one of main
technologies of smart grid, its structure and functions of each
component is represented. In terms of basic features of smart grid,
some key capabilities that advanced metering infrastructure should
possess are analyzed, and its impacts on power grid networks as
well. Combining current research situation of power utility
information acquisition system in china, this paper provides
reference for building smart grid of user side on the basis of
these preliminary analyses.
3. Improvement of the Short Term Load Forecasting Through the
Similarity Among Consumption Profiles
Abstract In order to achieve high quality standards in
electrical power systems, utility companies rely upon load
forecasting to accomplish critical activities such as optimal
dynamic dispatch and smart performance in the power wholesale
market. Several works propose hybrid intelligent forecasting models
to deal with the dynamic and nonlinear characteristics of the load
at a relatively high computational cost. While such approaches give
emphasis to the forecasting itself, this paper presents a procedure
to detect similarities among distinct consumption profiles.
Empirical results show that similar profile share similar sets of
relevant predictors. As finding similarities among profiles is less
costly than finding the set of relevant predictors from scratch, a
new parameter selection method is proposed. Such method is employed
to build some neural forecasters with a marked improvement in the
learning time.
4. Data Collecting from Smart Meters in an Advanced Metering
Infrastructure
Abstract The classical solution for collecting data from energy
meters, based on displacements of peoples, tends to be replaced by
modern solutions: drive-by and Automated Meter Reading (AMR). AMR
means to automatically collectdata from meters and send them to a
central computer. An Advanced Metering Infrastructure (AMI) is an
AMR infrastructure with bidirectional smart meters gateway
communication, this leading to extra facilities. CHAPTER 3
4.1 BLOCK DIAGRAM
4.2 BLOCK DIAGRAM DESCRIPTION
BLOCK DIAGRAM EXPLANATION:The above block diagram gives the
overview of theprojectin the pictorial form with the help of the
block diagram we will create pre model of theprojectand analyze the
function of theprojectthe explanation of theprojectwith block
diagram over view is given as follows.BLOCK DESCRIPTION
Power Supply Section:
This section is meant for supplying Power to all the sections
mentioned above. It basically consists of a Transformer to step
down the 230V ac to 18V ac followed by diodes. Here diodes are used
to rectify the ac to dc. After rectification the obtained rippled
dc is filtered using a capacitor Filter. A positive voltage
regulator is used to regulate the obtained dc voltage.
Microcontroller Section:This section forms the control unit of
the wholeproject. This section basically consists of a
Microcontroller with its associated circuitry like Crystal with
capacitors, Reset circuitry, Pull up resistors (if needed) and so
on. The Microcontroller forms the heart of theprojectbecause it
controls the devices being interfaced and communicates with the
devices according to the program being written.Transformers: In
general, the ac line voltage presentin your housewiring is not
suitable for electronic circuits. Most circuits require a
considerably lower voltage, while a few require higher voltages.
The transformer serves to convert the ac line voltage to a voltage
level more appropriate to the needs of the circuit to be powered.
At the same time, the transformer provides electrical isolation
between the ac line and the circuit being powered, which is an
important safety consideration. However, a line transformer is
generally large and heavy, and is rather expensive. Therefore, some
power supplies (notably for PCs) are deliberately designed to
operate directly from the ac line without a line transformer. The
output of the transformer is still an ac voltage, but now of an
appropriate magnitude for the circuit to be powered.
ADC: Analog to digital (A/D, ADC) converters are electrical
circuit devices that convert continuous signals, such as voltages
or currents, from the analog domain to the digital domain where the
signals are represented by numbers.LCD Display Section: This
section is basically meant to show upthe statusof theproject.
Thisprojectmakes use of Liquid Crystal Display to display / prompt
for necessary information. Sensors: This part of the system
consists of current sensor. These sensor sense various parameters
of load- current and are then sent to the Analog to Digital
Converter.Relay: In thisprojectRelays are used to the Trip the
transformer. A relay is an electrical switch that opens and closes
under control of another electrical circuit. In the original form,
the switch is operated by an electromagnet to open or close one or
many sets of contactsCHAPTER 5
HARDWARE:
POWER SUPPLY:
Power supply is a reference to a source of electrical power. A
device or system that supplies electrical or other types of energy
to an output load or group of loads is called a power supply unit
or PSU. The term is most commonly applied to electrical energy
supplies, less often to mechanical ones, and rarely to others.
A 230v, 50Hz Single phase AC power supply is given to a step
down transformer to get 12v supply. This voltage is converted to DC
voltage using a Bridge Rectifier. The converted pulsating DC
voltage is filtered by a 2200uf capacitor and then given to 7805
voltage regulator to obtain constant 5v supply. This 5v supply is
given to all the components in the circuit. A RC time constant
circuit is added to discharge all the capacitors quickly. To ensure
the power supply a LED is connected for indication purpose.
power supply:
definition:
A power supply (sometimes known as a power supply unit or PSU)
is a device or system that supplies electrical or other types of
energy to an output load or group of loads. The term is most
commonly applied to electrical energy supplies, less often to
mechanical ones, and rarely to others.
Figure A.Block diagram of a basic power supply.
As illustrated in view B of figure, the first section is the
TRANSFORMER.
The transformer steps up or steps down the input line voltage
and isolates the power supply from the power line.
The RECTIFIER section converts the alternating current input
signal to a pulsating direct current. However, as you proceed in
this chapter you will learn that pulsating dc is not desirable. For
this reason a FILTER section is used to convert pulsating dc to a
purer, more desirable form of dc voltage.
Figure B.Block diagram of a basic power supply. The final
section, the REGULATOR, does just what the name implies. It
maintains the output of the power supply at a constant level in
spite of large changes in load current or input line voltages. Now
that you know what each section does, let's trace an ac signal
through the power supply. At this point you need to see how this
signal is altered within each section of the power supply. Later on
in the chapter you will see how these changes take place. In view B
of figure 4-1, an input signal of 115 volts ac is applied to the
primary of the transformer.
The transformer is a step-up transformer with a turns ratio of
1:3. You can calculate the output for this transformer by
multiplying the input voltage by the ratio of turns in the primary
to the ratio of turns in the secondary; therefore, 115 volts ac 3 =
345 volts ac (peak-to- peak) at the output. Because each diode in
the rectifier section conducts for 180 degrees of the 360-degree
input, the output of the rectifier will be one-half, or
approximately 173 volts of pulsating dc. The filter section, a
network of resistors, capacitors, or inductors, controls the rise
and fall time of the varying signal; consequently, the signal
remains at a more constant dc level. You will see the filter
process more clearly in the discussion of the actual filter
circuits. The output of the filter is a signal of 110 volts dc,
with ac ripple riding on the dc. The reason for the lower voltage
(average voltage) will be explained later in this chapter. The
regulator maintains its output at a constant 110-volt dc level,
which is used by the electronic equipment (more commonly called the
load). Simple 5V power supply for digital circuits
1.1 Summary of circuit features Brief description of operation:
Gives out well regulated +5V output, output current capability of
100 mA
Circuit protection: Built-in overheating protection shuts down
output when regulator IC gets too hot
Circuit complexity: Very simple and easy to build
Circuit performance: Very stable +5V output voltage, reliable
operation
Availability of components: Easy to get, uses only very common
basic components
Design testing: Based on datasheet example circuit, I have used
this circuit successfully as part of many electronics projects
Applications: Part of electronics devices, small laboratory
power supply
Power supply voltage: Unregulated DC 8-18V power supply
Power supply current: Needed output current + 5 mA
Component costs: Few dollars for the electronics components +
the input transformer cost
5.1 ATMEGA 8 5.1.1 CONCEPTS OF MICROCONTROLLER: Microcontroller
is a general purpose device, which integrates a number of the
components of a microprocessor system on to single chip. It has
inbuilt CPU, memory and peripherals to make it as a mini computer.
A microcontroller combines on to the same microchip:
The CPU core
Memory(both ROM and RAM)
Some parallel digital i/o
Micro controllers will combine other devices such as:
A timer module to allow the micro controller to perform tasks
for certain time periods.
A serial i/o port to allow data to flow between the controller
and other devices such as a PIC or another Microcontroller.
An ADC to allow the Micro controller to accept analogue input
data for processing.
Micro controllers are :
Smaller in size
Consumes less power
Inexpensive
Micro controller is a stand alone unit ,which can perform
functions on its own without any requirement for additional
hardware like i/o ports and external memory.
The heart of the microcontroller is the CPU core. In the past,
this has traditionally been based on a 8-bit microprocessor unit.
For example Motorola uses a basic 6800 microprocessor core in their
6805/6808 microcontroller devices.
In the recent years, microcontrollers have been developed around
specifically designed CPU cores, for example the microchip PIC
range of microcontrollers.
5.1.2 MICROCONTROLLER ATmega8:
PIN DIAGRAM:
5.1.2.1 Features:
High-performance, Low-power AtmelAVR 8-bit Microcontroller
Advanced RISC Architecture
130 Powerful Instructions Most Single-clock Cycle Execution
32 8 General Purpose Working Registers
Fully Static Operation
Up to 16MIPS Throughput at 16MHz
On-chip 2-cycle Multiplier
High Endurance Non-volatile Memory segments
8Kbytes of In-System Self-programmable Flash program memory
512Bytes EEPROM
1Kbyte Internal SRAM
Write/Erase Cycles: 10,000 Flash/100,000 EEPROM
Data retention: 20 years at 85C/100 years at 25C(1)
Optional Boot Code Section with Independent Lock Bits
In-System Programming by On-chip Boot Program
Peripheral Features
Two 8-bit Timer/Counters with Separate Prescaler, one Compare
Mode
One 16-bit Timer/Counter with Separate Prescaler, Compare Mode,
and Capture
Mode
Real Time Counter with Separate Oscillator
Three PWM Channels
8-channel ADC in TQFP and QFN/MLF package
Eight Channels 10-bit Accuracy
6-channel ADC in PDIP package
Six Channels 10-bit Accuracy
Byte-oriented Two-wire Serial Interface
Programmable Serial USART
Master/Slave SPI Serial Interface
Programmable Watchdog Timer with Separate On-chip Oscillator
On-chip Analog Comparator
Special Microcontroller Features
Power-on Reset and Programmable Brown-out Detection
Internal Calibrated RC Oscillator
External and Internal Interrupt Sources
Five Sleep Modes: Idle, ADC Noise Reduction, Power-save,
Power-down, and
Standby
I/O and Packages
23 Programmable I/O Lines
28-lead PDIP, 32-lead TQFP, and 32-pad QFN/MLF
Operating Voltages
2.7V - 5.5V (ATmega8L)
4.5V - 5.5V (ATmega8)
Speed Grades
0 - 8MHz (ATmega8L)
0 - 16MHz (ATmega8)
5.1.2.2 PIN DESCRIPTIONS:1.VCC Digital supply voltage.
2.GND Ground.
3. XTAL1/XTAL2/TOSC1/TOSC2
Port B (PB7..PB0)
Port B is an 8-bit bi-directional I/O port with internal pull-up
resistors (selected for each bit). The Port B output buffers have
symmetrical drive characteristics with both high sink and source
capability. As inputs, Port B pins that are externally pulled low
will source current if the pull-up resistors are activated. The
Port B pins are tri-stated when a reset condition becomes
active,even if the clock is not running. Depending on the clock
selection fuse settings, PB6 can be used as input to the inverting
Oscillator amplifier and input to the internal clock operating
circuit.Depending on the clock selection fuse settings, PB7 can be
used as output from the inverting Oscillator amplifier.If the
Internal Calibrated RC Oscillator is used as chip clock source,
PB7..6 is used as TOSC2..1input for the Asynchronous Timer/Counter2
if the AS2 bit in ASSR is set.Port C (PC5..PC0)
Port C is an 7-bit bi-directional I/O port with internal pull-up
resistors (selected for each bit). The Port C output buffers have
symmetrical drive characteristics with both high sink and source
capability. As inputs, Port C pins that are externally pulled low
will source current if the pull-up resistors.PC6/RESET
If the RSTDISBL Fuse is programmed, PC6 is used as an I/O pin.
Note that the electrical characteristics of PC6 differ from those
of the other pins of Port C.If the RSTDISBL Fuse is unprogrammed,
PC6 is used as a Reset input. A low level on this pin for longer
than the minimum pulse length will generate a Reset, even if the
clock is not running. Shorter pulses are not guaranteed to generate
a Reset.
Port D (PD7..PD0)
Port D is an 8-bit bi-directional I/O port with internal pull-up
resistors (selected for each bit). The Port D output buffers have
symmetrical drive characteristics with both high sink and source
capability. As inputs, Port D pins that are externally pulled low
will source current if the pull-up resistors are activated. The
Port D pins are tri-stated when a reset condition becomes
active,even if the clock is not running.
RESET
Reset input. A low level on this pin for longer than the minimum
pulse length will generate a reset, even if the clock is not
running. Shorter pulses are not guaranteed to generate a reset.
5.1.2.3 ATmega8(L)
AVCC AVCC is the supply voltage pin for the A/D Converter, Port
C (3..0), and ADC (7..6). It should be externally connected to VCC,
even if the ADC is not used. If the ADC is used, it should be
connected to VCC through a low-pass filter. Note that Port C (5..4)
use digital supply voltage, VCC.AREF AREF is the analog reference
pin for the A/D Converter.
5.1.2.4 ARCHITECTURAL OVER VIEW
5.2 LCD DISPLAY:
Liquid crystal displays (LCDs) have materials which combine the
properties of both liquids and crystals. Rather than having a
melting point, they have a temperature range within which the
molecules are almost as mobile as they would be in a liquid, but
are grouped together in an ordered form similar to a crystal.
An LCD consists of two glass panels, with the liquid crystal
material sand witched in between them. The inner surface of the
glass plates are coated with transparent electrodes which define
the character, symbols or patterns to be displayed polymeric layers
are present in between the electrodes and the liquid crystal, which
makes the liquid crystal molecules to maintain a defined
orientation angle.
One each polarisers are pasted outside the two glass panels.
These polarisers would rotate the light rays passing through them
to a definite angle, in a particular direction
When the LCD is in the off state, light rays are rotated by the
two polarisers and the liquid crystal, such that the light rays
come out of the LCD without any orientation, and hence the LCD
appears transparent.When sufficient voltage is applied to the
electrodes, the liquid crystal molecules would be aligned in a
specific direction. The light rays passing through the LCD would be
rotated by the polarisers, which would result in activating /
highlighting the desired characters.
LCD display:
5.2.1 16 x 2 character LCD display:
An LCD is a small low cost display. it is easy to interface with
a micro-controller because of an embedded controller (the black
blob on the back of the board). This controller is standard across
many displays (hd 44780), which means many micro-controllers have
libraries that make displaying messages as easy as a single line of
code.
LCD
LCD stands for Liquid Crystal Display. LCD is finding wide
spread use replacing LEDs (seven segment LEDs or other multi
segment LEDs) because of the following reasons:
1. The declining prices of LCDs.
2. The ability to display numbers, characters and graphics. This
is in contrast to LEDs, which are limited to numbers and a few
characters.
3. Incorporation of a refreshing controller into the LCD,
thereby relieving the CPU of the task of refreshing the LCD. In
contrast, the LED must be refreshed by the CPU to keep displaying
the data.
4. Ease of programming for characters and graphics.
These components are specialized for being used with the
microcontrollers, which means that they cannot be activated by
standard IC circuits. They are used for writing different messages
on a miniature LCD.
LCD Display
A model described here is for its low price and great
possibilities most frequently used in practice. It is based on the
HD44780 microcontroller (Hitachi) and can display messages in two
lines with 16 characters each . It displays all the alphabets,
Greek letters, punctuation marks, mathematical symbols etc. In
addition, it is possible to display symbols that user makes up on
its own. Automatic shifting message on display (shift left and
right), appearance of the pointer, backlight etc. are considered as
useful characteristics.
PIN FUNCTIONS:
There are pins along one side of the small printed board used
for connection to the microcontroller. There are total of 14 pins
marked with numbers (16 in case the background light is built in).
Their function is described in the table below:
LCD screen:
LCD screen consists of two lines with 16 characters each. Each
character consists of 5x7 dot matrix. Contrast on display depends
on the power supply voltage and whether messages are displayed in
one or two lines. For that reason, variable voltage 0-Vdd is
applied on pin marked as Vee. Trimmer potentiometer is usually used
for that purpose. Some versions of displays have built in backlight
(blue or green diodes). When used during operating, a resistor for
current limitation should be used (like with any LE diode).
LCD display panel
LCD BASIC COMMANDS:
All data transferred to LCD through outputs D0-D7 will be
interpreted as commands or as data, which depends on logic state on
pin RS:
RS = 1 - Bits D0 - D7 are addresses of characters that should be
displayed. Built in processor addresses built in map of characters
and displays corresponding symbols. Displaying position is
determined by DDRAM address. This address is either previously
defined or the address of previously transferred character is
automatically incremented.RS = 0 - Bits D0 - D7 are commands which
determine display mode. List of commands for lcd:
LCD Connection:
Depending on how many lines are used for connection to the
microcontroller, there are 8- bit and 4-bit LCD modes. The
appropriate mode is determined at the beginning of the process in a
phase called initialization. In the first case, the data are
transferred through outputs D0-D7 as it has been already explained.
In case of 4-bit LED mode, for the sake of saving valuable I/O pins
of the microcontroller, there are only 4 higher bits (D4-D7) used
for communication, while other may be left unconnected.
Consequently, each data is sent to LCD in two steps: four higher
bits are sent first (that normally would be sent through lines
D4-D7), four lower bits are sent afterwards. With the help of
initialization, LCD will correctly connect and interpret each data
received. Besides, with regards to the fact that data are rarely
read from
LCD (data mainly are transferred from microcontroller to LCD)
one more I/O pin may be saved by simple connecting R/W pin to the
Ground. Such saving has its price. Even though message displaying
will be normally performed, it will not be possible to read from
busy flag since it is not possible to read from display.
LCD Initialization:Once the power supply is turned on, LCD is
automatically cleared. This process lasts for approximately 15mS.
After that, display is ready to operate. The mode of operating is
set by default. This means that:
1. Display is cleared
2. Mode
DL = 1 Communication through 8-bit interface
N = 0 Messages are displayed in one line
F = 0 Character font 5 x 8 dots
3. Display/Cursor on/off
D = 0 Display off
U = 0 Cursor off
B = 0 Cursor blink off
5. Character entry
6. ID = 1 Addresses on display are automatically incremented by
1
S = 0 Display shift off
Automatic reset is mainly performed without any problems. Mainly
but not always! If for any reason power supply voltage does not
reach full value in the course of 10mS, display will start perform
completely unpredictably? If voltage supply unit can not meet this
condition or if it is needed to provide completely safe operating,
the process of initialization by which a new reset enabling display
to operate normally must be applied.Algorithm according to the
initialization is being performed depends on whether connection to
the microcontroller is through 4- or 8-bit interface. All left over
to be done after that is to give basic commands and of course- to
display messages .
CIRCUIT DIAGRAM
Advantages and disadvantages of LCD
LCD
Pros:
Very compact and light.
Low power consumption.
No geometric distortion.
Little or no flicker depending on backlight technology.
Not affected by screen burn-in.
No high voltage or other hazards present during
repair/service.[citation needed] Can be made in almost any size or
shape.
No theoretical resolution limit.
Cons:
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.
KEYPAD
INTRODUCTION
This note describes an method of interfacing a matrix keyboard
to EZ328 using minimum number of I/O ports. We use a 4x1 matrix
keypad as an example. It requires only five I/O ports. (In general,
it takes n+1 ports to interface a nxn matrix keyboard). It is a low
cost solution. No TTL logic ICs are used. The components mainly
used in the interfacing circuitry include only diodes and resistors
which can greatly reduce the system cost and size of the
product.
HARDWARE
Figure 1 shows a functional block diagram of the keyboard
interface. As seen in this diagram, there are two major parts.
Interrupt & interfacing Circuity - generates interrupt to
EZ328 when there is a key pressed and provides connection to EZ328s
I/O ports
Keyboard matrix - a 4x1 matrix keypad
Interrupt & interfacing Circuit
The interrupt and interfacing circuit includes some diodes,
resistors, pull-up resistors and a NPN transistor.The transistor
part is designed as an inverter for generating interrupt signal to
EZ328 when there is a key pressed. There are two groups of diodes
mainly for restricting signal flow in single direction so as to
enable this circuitry to identify the pressed key uniquely. One of
these two groups of diodes have been wired together to provide a OR
function which in turn allows any key pressed on each column of the
keypad to signal the transistor part for generating interrupt.
Parallel Ports Interface
This solution demonstrates a simple mechanism to build a
keyboard with minimum I/O port used. In this application, we use a
4x4 matrix keypad as an example. It requires only five I/O ports
for interfacing. One of them is used for generating the interrupt
signal in the beginning and used as an I/O port for key scanning
operation afterwards. Detail of the method in scanning and
identifying the pressed key will be discussed in the section SCAN
KEYOperation. It should also be noted that in this design, EZ328
uses five ports for interfacing but only one of them requires
interrupt capability.
SCAN KEY OPERATION
Five ports are used for key scanning function in this system.
One of them (PD7) is used as the interrupt pin before a key is
pressed. Before the key scanning process starts, all of the I/O
ports except the one with interrupt capability is configured as
output high. Then, when there is a key pressed, one of the columns
on the keypad changes state from low to high. As all the columns on
the keypad are wired together to form a OR logic to the base of the
NPN transistor, it will generate an active low interrupt signal to
EZ328 and initiates the interrupt handler to scan the pressed
key.When the key scanning process begins, one of the five I/O ports
will be configured to output high while the other ports are
configured to input. The states on all ports are then read and
compared with the pattern recorded in a predefined lookup table in
order to locate which key is pressed. If the key is not found,
another port will be configured to output high instead and read the
states again. This process is repeated until all ports have been
configured once to output high or a key is found.Since the
circuitry provides feedback paths, one of the input port will
change state from low to high by the output high port and the
states obtained can identify uniquely which key is being pressed.
An example of the scanning procedure is illustrated as follows:
5.3 transformer
Potential Transformer is designed for monitoring single-phase
and three-phase power line voltages in power metering applications.
The primary terminals can be connected either in line-to-line or in
line-to-neutral configuration. Fused transformer models are
designated by a suffix of "F" for one fuse or "FF" for two fuses. A
Potential Transformer is a special type of transformer that allows
meters to take readings from electrical service connections with
higher voltage (potential) than the meter is normally capable of
handling without at potential transformer.
A transformer is a device that transfers electrical energy from
one circuit to another through inductively coupled conductorsthe
transformer's coils. A varying current in the first or primary
winding creates a varying magnetic flux in the transformer's core,
and thus a varying magnetic field through the secondary winding.
This varying magnetic field induces a varying electromotive force
(EMF) or "voltage" in the secondary winding. This effect is called
mutual induction.
If a load is connected to the secondary, an electric current
will flow in the secondary winding and electrical energy will be
transferred from the primary circuit through the transformer to the
load. In an ideal transformer, the induced voltage in the secondary
winding (VS) is in proportion to the primary voltage (VP), and is
given by the ratio of the number of turns in the secondary (NS) to
the number of turns in the primary (NP) as follows:
By appropriate selection of the ratio of turns, a transformer
thus allows an alternating current (AC) voltage to be "stepped up"
by making NS greater than NP, or "stepped down" by making NS less
than NP. In the vast majority of transformers, the windings are
coils wound around a ferromagnetic core, air-core transformers
being a notable exception. Transformers range in size from a
thumbnail-sized coupling transformer hidden inside a stage
microphone to huge units weighing hundreds of tons used to
interconnect portions of power grids. All operate with the same
basic principles, although the range of designs is wide. While new
technologies have eliminated the need for transformers in some
electronic circuits, transformers are still found in nearly all
electronic devices designed for household ("mains") voltage.
Transformers are essential for high voltage power transmission,
which makes long distance transmission economically practical.
5.4 CURRENT TRANSFORMER:
In electrical engineering, a current transformer (CT) is used
for measurement of electric currents. Current transformers,
together with voltage transformers (VT) (potential transformers
(PT)), are known as instrument transformers. When current in a
circuit is too high to directly apply to measuring instruments, a
current transformer produces a reduced current accurately
proportional to the current in the circuit, which can be
conveniently connected to measuring and recording instruments. A
current transformer also isolates the measuring instruments from
what may be very high voltage in the monitored circuit. Current
transformers are commonly used in metering and protective relays in
the electrical power industry.
Like any other transformer, a current transformer has a primary
winding, a magnetic core, and a secondary winding. The alternating
current flowing in the primary produces a magnetic field in the
core, which then induces a current in the secondary winding
circuit. A primary objective of current transformer design is to
ensure that the primary and secondary circuits are efficiently
coupled, so that the secondary current bears an accurate
relationship to the primary current.
The most common design of CT consists of a length of wire
wrapped many times around a silicon steel ring passed over the
circuit being measured. The CT's primary circuit therefore consists
of a single 'turn' of conductor, with a secondary of many hundreds
of turns. The primary winding may be a permanent part of the
current transformer, with a heavy copper bar to carry current
through the magnetic core. Window-type current transformers are
also common, which can have circuit cables run through the middle
of an opening in the core to provide a single-turn primary
winding.
Current transformers are used extensively for measuring current
and monitoring the operation of the power grid. Along with voltage
leads, revenue-grade CTs drive the electrical utility's watt-hour
meter on virtually every building with three-phase service and
single-phase services greater than 200 amp.
The CT is typically described by its current ratio from primary
to secondary. Often, multiple CTs are installed as a "stack" for
various uses. For example, protection devices and revenue metering
may use separate CTs to provide isolation between metering and
protection circuits, and allows current transformers with different
characteristics (accuracy, overload performance) to be used for the
different purpose5.5 SIGNAL CONDITIONING UNIT:
The signal conditioning unit accepts input signals from the
analog sensors and gives a conditioned output of 0-5V DC
corresponding to the entire range of each parameter. This unit also
accepts the digital sensor inputs and gives outputs in 10 bit
binary with a positive logic level of +5V. The calibration
voltages* (0, 2.5 and 5V) and the health bits are also generated in
this unit.
Microcontrollers are widely used for control in power
electronics. They provide real time control by processing analog
signals obtained from the system. A suitable isolation interface
needs to be designed for interaction between the control circuit
and high voltage hardware. A signal conditioning unit which
provides necessary interface between a high power grid inverter and
a low voltage controller unit.
5.6 AMPLIFIER:Generally, an amplifier is any device that will
convert a signal with a small amount of energy into a similar
signal with a larger amount of energy. In popular use, the term
today usually refers to an electronic amplifier, often as in audio
applications. The relationship of the input to the output of an
amplifier usually expressed as a function of the input frequency is
called the transfer function of the amplifier, and the magnitude of
the transfer function is termed the gain.
General characteristics of amplifiers
Most amplifiers can be characterized by a number of
parameters.
Gain
The gain is the ratio of output power to input power, and is
usually measured in decibels . (When measured in decibels it is
logarithmically related to the power ratio:
G(dB)=10log(Pout/Pin)).
Output dynamic range
Output dynamic range is the range, usually given in dB, between
the smallest and largest useful output levels. Since the lowest
useful level is limited by output noise, this is quoted as the
amplifier dynamic range.
Bandwidth and rise time
The bandwidth (BW) of an amplifier is usually defined as the
difference between the lower and upper half power points. This is
therefore also known as the -3 dB BW. Bandwidths for other response
tolerances are sometimes quoted (-1 dB, -6 dB etc.).
A full-range audio amplifier will be essentially flat between
twenty hertz to about twenty kilohertz (the range of normal human
hearing.) In minimalist amplifier design, the amp's usable
frequency response needs to extend considerably beyond this (one or
more octaves either side) and typically a good minimalist amplifier
will have -3 dB points < 10 and > 65 kHz. Professional
touring amplifiers often have input and/or output filtering to
sharply limit frequency response beyond 20-20 kHz; too much of the
amplifier's potential output power would otherwise be wasted on
infrasonic and ultrasonic frequencies, and the danger of AM radio
interference would increase. Modern switching amplifiers need steep
low pass filtering at the output to get rid of high frequency
switching noise and harmonics.The rise time of an amplifier is the
time taken for the output to change from 10% to 90% of its final
level when driven by a step input.Many amplifiers are ultimately
slew rate limited (typically by the impedance of a drive current
having to overcome capacitive effects at some point in the
circuit), which may limit the full power bandwidth to frequencies
well below the amplifiers frequency response when dealing with
small signals.For a Gaussian response system (or a simple RC roll
off), the rise time is approximated by:Tr * BW = 0.35, where Tr is
in seconds and BW is in Hz. Settling time and aberrations
Time taken for output to settle to within a certain percentage
of the final value (say 0.1%). This is usually specified for
oscilloscope vertical amplifiers and high accuracy measurement
systems.
Slew rate
Slew rate is the maximum rate of change of output variable,
usually quoted in volts per second (or microsecond).
Noise
This is a measure of how much noise is introduced in the
amplification process. Noise is an undesirable but inevitable
product of the electronic devices and components. It is measured in
either decibels or the peak output voltage produced by the
amplifier when no signal is applied.
Efficiency
Efficiency is a measure of how much of the input power is
usefully applied to the amplifier's output. Class A amplifiers are
very inefficient, in the range of 1020% with a max efficiency of
25%. Class B amplifiers have a very high efficiency but are
impractical because of high levels of distortion (See: Crossover
distortion). In practical design, the result of a tradeoff is the
class AB design. Modern Class AB amps are commonly between 3555%
efficient with a theoretical maximum of 78.5%. Commercially
available Class D switching amplifiers have reported efficiencies
as high as 97%. The efficiency of the amplifier limits the amount
of total power output that is usefully available. Note that more
efficient amplifiers run much cooler, and often do not need any
cooling fans even in multi-kilowatt designs.
5.7 driver circuit:
In electronics, a driver is an electrical circuit or other
electronic component used to control another circuit or other
component, such as a high-power transistor. The term is used, for
example, for a specialized computer chip that controls the
high-power transistors in AC-to-DC voltage converters. An amplifier
can also be considered the driver for loudspeakers, or a constant
voltage circuit that keeps an attached component operating within a
broad range of input voltages.
The following circuit will allow you to drive a 12V relay using
logic voltage (an input of 4V or greater will trip the relay). The
circuit has its own 12V power supply making it self contained but
the power supply portion can be left out if an external supply will
be used. The circuit shows an output from the power supply that can
be used to power other devices but it should be noted that the
supply is unregulated and not particulary powerful with the parts
stated. The 12V DC output is suitable for powering a few LEDs or
low voltage lights but should not be used to power other electronic
boards or motors.
5.8 relay: A relay is an electrically operated switch. Many
relays use an electromagnet to operate a switching mechanism, but
other operating principles are also used. Relays find applications
where it is necessary to control a circuit by a low-power signal,
or where several circuits must be controlled by one signal. The
first relays were used in long distance telegraph circuits,
repeating the signal coming in from one circuit and re-transmitting
it to another. Relays found extensive use in telephone exchanges
and early computers to perform logical operations. A type of relay
that can handle the high power required to directly drive an
electric motor is called a contactor. Solid-state relays control
power circuits with no moving parts, instead using a semiconductor
device triggered by light to perform switching. Relays with
calibrated operating characteristics and sometimes multiple
operating coils are used to protect electrical circuits from
overload or faults; in modern electric power systems these
functions are performed by digital instruments still called
"protection relays".
Basic design and operation
Small relay as used in electronics
A simple electromagnetic relay, such as the one taken from a car
in the first picture, is an adaptation of an electromagnet. It
consists of a coil of wire surrounding a soft iron core, an iron
yoke, which provides a low reluctance path for magnetic flux, a
movable iron armature, and a set, or sets, of contacts; two in the
relay pictured. The armature is hinged to the yoke and mechanically
linked to a moving contact or contacts. It is held in place by a
spring so that when the relay is de-energized there is an air gap
in the magnetic circuit. In this condition, one of the two sets of
contacts in the relay pictured is closed, and the other set is
open. Other relays may have more or fewer sets of contacts
depending on their function. The relay in the picture also has a
wire connecting the armature to the yoke. This ensures continuity
of the circuit between the moving contacts on the armature, and the
circuit track on the printed circuit board (PCB) via the yoke,
which is soldered to the PCB.
When an electric current is passed through the coil, the
resulting magnetic field attracts the armature, and the consequent
movement of the movable contact or contacts either makes or breaks
a connection with a fixed contact. If the set of contacts was
closed when the relay was De-energized, then the movement opens the
contacts and breaks the connection, and vice versa if the contacts
were open. When the current to the coil is switched off, the
armature is returned by a force, approximately half as strong as
the magnetic force, to its relaxed position. Usually this force is
provided by a spring, but gravity is also used commonly in
industrial motor starters. Most relays are manufactured to operate
quickly. In a low voltage application, this is to reduce noise. In
a high voltage or high current application, this is to reduce
arcing.
5.9 ALARM
An alarm gives an audible or visual warning about a problem or
condition.
Alarms include:
burglar alarms, designed to warn of burglaries; this is often a
silent alarm: the police or guards are warned without indication to
the burglar, which increases the chances of catching him or
her.
alarm clocks can produce an alarm at a given time
distributed control manufacturing systems or DCSs, found in
nuclear power plants, refineries and chemical facilities also
generate alarms to direct the operator's attention to an important
event that he or she needs to address.
alarms in an operation and maintenance (O&M) monitoring
system, which informs the bad working state of (a particular part
of) the system under monitoring.
safety alarms, which go off if a dangerous condition occurs.
Common public safety alarms include:
tornado sirens fire alarms
"Multiple-alarm fire", a locally-specific measure of the
severity of a fire and the fire-department reaction required.
car alarms community Alarm or auto dialer alarm (medical
alarms)
air raid sirens personal alarm tocsins a historical method of
raising an alarm
Alarms have the capability of causing a fight-or-flight response
in humans; a person under this mindset will panic and either flee
the perceived danger or attempt to eliminate it, often ignoring
rational thought in either case. We can characterise a person in
such a state as "alarmed".
With any kind of alarm, the need exists to balance between on
the one hand the danger of false alarms (called "false positives")
the signal going off in the absence of a problem and on the other
hand failing to signal an actual problem (called a "false
negative"). False alarms can waste resources expensively and can
even be dangerous. For example, false alarms of a fire can waste
firefighter manpower, making them unavailable for a real fire, and
risk injury to firefighters and others as the fire engines race to
the alleged fire's location.
CHAPTER-6APPLICATIONS
1. Industries2. EB office
3. Home applications
CHAPTER 7CONCLUSIONThe progress in science & technology is a
non-stop process. New things and new Technology are being invented.
As the technology grows day by day, we can imagine about the future
in which thing we may occupy every place.The proposed system based
on Atmel microcontroller is found to be more compact, user friendly
and less complex, which can readily be used in order to perform.
Several tedious and repetitive tasks. In this phase we collected
existing system of meter reading methods and their disadvantages.
We analysed the existing method meter reading and we introduced new
meter reading method which is very helpful for electricity board.
In proposed system we implementing digital energy meter using wifi,
for that we collected all hardware details and software details. In
phase 2 we implementing the digital energy meter and wireless data
acquation system using WIFI.referenceMILL MAN J and HAWKIES C.C.
INTEGRATED
ELECTRONICS MCGRAW HILL, 1972
ROY CHOUDHURY D, SHAIL JAIN, LINEAR INTEGRATED CIRCUIT, New Age
International Publishers, New Delhi,2000
THE 8051 MICROCONTROLLER AND EMBEDDED SYSTEM by Mohammad Ali
Mazidi.
WEBSITES:
http://www.atmel.com/ http://www.microchip.com/ www.8052.com
http://www.beyondlogic.org http://www.ctv.es/pckits/home.html
http://www.aimglobal.org/CommandRSRWD7D6D5D4D3D2D1D0Execution
TimeClear display00000000011.64mSCursor home000000001x1.64mSEntry
mode set00000001I/DS40uSDisplay on/off
control0000001DUB40uSCursor/Display Shift000001D/CR/Lxx40uSFunction
set00001DLNFxx40uSSet CGRAM address0001CGRAM address40uSSet DDRAM
address001DDRAM address40uSRead BUSY flag (BF)01BFDDRAM
address-Write to CGRAM or DDRAM10D7D6D5D4D3D2D1D040uSRead from
CGRAM or DDRAM11D7D6D5D4D3D2D1D040uS