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A PROJECT REPORT ON
“WIRELESS ELECTRICAL APPLIANCES SWITCHING SYSTEM”
In the partial fulfillment of the
BACHELOR ‘S DEGREE IN
B.TECH
―ELECTRICAL & ELECTRONICS ENGINEERING‖
DEPARTMENT OF ELECTRICAL & ELECTRONICS ENGINEERING
HINDUSTAN INSTITUTE OF TECHNOLOGY & MANAGEMENT
KEETHAM AGRA
SESSION 2009 - 2013
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A PROJECT ON
“WIRELESS ELECTRICAL APPLIANCES SWITCHING SYSTEM”
Submitted for partial fulfillment of award of
―BACHELOR OF TECHNOLOGY‖
IN
―ELECTRICAL & ELECTRONICS ENGINEERING‖
UNDER THE SUPERVISION OF
MR.S.P.MAGO SIR
(DEAN ACADEMICS)
SUBMITTED BY
JITENDRA KUMAR (0900321049)
GAUTAM BUDDH TECHNICAL UNIVERSITY
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CERTIFICATE
This is to certify that project report on “ WIRELESS
ELECTRIC L PPLI NCES SWITCHING SYSTEM
has been successfully completed by itendra Kumar
student of final year.
Submitted in partial fulfillment for the award of
„BACHELOR OF TECHNOLOGY (B.TECH)‟ in
ELECTRICAL & ELECTRONICS ENGINEERING
from H.I.T.M College of Engineering affiliated to
G.B.T.U University , LUCKNOW during session
2009-13.
MR.S.P.MAGO SIR MR.VIRENDRA SHARMA
SIR(PROJECT COORDINATOR) (PROJECT GUIDE)
(DEAN ACADEMIC) (H.O.D)
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ACKNOWLEDGEMENT
The satisfaction and euphoria that accompany the successfulcompletion of any task would be incomplete without the mentioning
of the people whose constant guidance and encouragement made it
possible. We take pleasure in presenting before you, our project,
which is result of studied blend of both research and knowledge.
We express our earnest gratitude to our project guide
Mr.VIRENDRA SHARMA SIR, H.O.D OF EEE Department, for
his constant support, encouragement and guidance. We are grateful
for his cooperation and his valuable suggestions.
Our deep sense of gratitude to MR. S.P.MAGO SIR, Dean
Academics, for his support. We also thank our institution and my
faculty members without who this project would have been a distant
reality. We also extend my heartfelt thanks to our family and well
wishing friends.
Finally, we express our gratitude to all other members who are
involved either directly or indirectly for the completion of this project.
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ABSTRACT
The cheapest way to remotely control a device within a
range is via wireless. Due to this wide spread use the required
components are quite cheap, thus making it ideal for us to use wireless
control for our own projects.
Wireless communication, as the term implies, allows
information to be exchanged between two devices without the use of
wire or cable. In all such cases, information is being transmitted and
received using electromagnetic energy, also referred to as
electromagnetic radiation. The applications are they can operate multi
number of appliances without moving from the place where we are .This
project describes to control the Home appliances wirelessly using
wireless communication. When we access the remote by pressing a key,
the wireless transmitter sends a 4 bit code l to the Receiver which is
placed in the desired room as bursts of electromagnetic waves. The
Receiver in the other end detects and captures the code, which are then
processed via microcontroller to retrieve the information they contain.
This application uses ht12d & 433 mhz receiver which
will accept signals. The microcontroller captures the code and controller
performs the necessary action by turning ON/OFF the home appliances.
The applications are they can operate multi number of appliances
without moving from the place where we are .This project describes to
control the Home appliances wirelessly using wireless communication.
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When we access the remote by pressing a key, the wireless transmitter
sends a 4 bit code l to the Receiver which is placed in the desired room
as bursts of electromagnetic waves.
The Receiver in the other end detects and captures the
code, which are then processed via microcontroller to retrieve the
information they contain. This application uses ht12d & 433 mhz receiver
which will accept signals. The microcontroller captures the code and
controller performs the necessary action by turning ON/OFF the home
appliances.
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DECLARATION
We, the undersigned, declare that the project
entitled ‘ WIRELESS ELECTRIC L PPLI NCES
SWITCHING SYSTEM’, being submitted in partial
fulfillment for the award of Bachelor of Technology
Degree in ELECTRICAL AND ELECTRONICS
ENGINEERING affiliated to G.B.T.U University, is
the work carried out by us.
The results embodied in this thesis have not been
submitted to any other University or Institute for
the award of any diploma or degree.
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Table of Contents
Certificate……………………………………………………………………………………..i
Acknowledgement…………………………………………………………………………....ii
Abstract………………………………………………………………………………………iii
Declaration………………………………………………………………………………….
Chapter 0 : Introduction ………………………………………………..……………....11
Chapter 1 : Hardware Requirement…………..………………..………………………12
Chapter 2: Block diagram
3.1 Block Diagram of Receiver……………………….…………………………..13
3. 2 Block Diagram of Transmitter…………………….…………………………13
Chapter 3: Pin Diagram
3.1 Pin Diagram of Receiver……………………………………….……………..15
3.2 Block Diagram of Transmitter………………………………………………..14
Chapter 4 : Microcontroller (AT896S52)
4.1 Description …………………………………….……………..………………..17
4.2 Blockdiagram…………………………………………...…….……………… 18
4.3 Pin configuration ………………………….…………………………………...19
Chapter 5 : Encoder IC (HT12E)
5.1 General Description……………………………………...……………………23
5.2 Pin Configuration …………………………………...………………………..24
5.3 Pin Description………………………………………………………………..25
5.4 Features……………………….………………………………………………26
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5.5 Applications………………………… ……………………………26
5.6 Block Diagram………………………… ……………………..26
Chapter 6 : Decoder IC (HT12E)
6.1 2. Pin Configuration ……………………………….…………………...28
6.2 Pin Description ……………………… ………….…………………….29
6.3 Features………………………………………………………………….30
6.4 Applications………………………………………….………...………..30
6.5 General Description……………………………………………….…….30
6.6 Block diagram………………………………………………..………….31
Chapter 7 : Transformer
7.1 Introduction…………………………………………….…………………..32
7.2 Working………………………………………………………………..…...33
7.3 Step down transformer…………………………………….……………….34
Chapter 8 : Capacitor
8.1 About capacitor…………………………………………….…………………..35
8.2 Theory of operation…………………………………………..………………...35
8.3 Energy of electric field……………………………………………..…………..36
8.4 Current-voltage relation…………………………………………….………….36
8.5 Network connection……………………………………………….…………...37
8.6 Capacitor used……………………………………………………….…………38
8.7 Markings……………………………………………………………..…………39
Chapter 9 : Resistor
9.1 About resistor…………………………………………….……………...........40
9.2 Theory of operation………………………………………..………………….41
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9.3 Network connection……………………………………….………………….41
9.4 Resistor marking………………………………………..……………………..42
9.5 Resistor used………………………………………………..…………………43
Chapter 12 : RF Module
12.1 RF Module…………………………………………………..……………44
12.2 Physical Diagram……………………………………..………………......46
12.3 RF signal modulation…………………………………………...………...46
12.4 Main Factors affecting RF module performance………………………….47
Chapter 11: Diode
11.1 Introduction……………………………………………………….………….48
11.2 Physical structure & working……………………………………..………….49
11.3 V-I Characteristic……………………………………………….……………50
11.4 Diode equation………………………………………………….……………51
11.5 Numbering & Coding Schemes……………………………..……………......51
11.6 Diode used…………………………………………………..………………..52
Chapter 12: Antenna……………………………………………………….………….53
Chapter 13: Rectifier......................................................................................................55
Chapter 14: Filter…………………………………………………………..………….56
Chapter 15: Voltage Regulator.......................................................................................57
Chapter 16: Light Emitting Diode…………………………………………………….58
How It Works……………………………………………………………………………62
Conclusion and Future scope…………………………………………………….……..63
Result…………………………………………………………………………………….64
Bibliography……………………………………………………………///..…………….65
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INTRODUCTION Wireless communication, as the term implies, allows information to be
exchanged between two devices without the use of wire or cable. In all
such cases, information is being transmitted and received using
electromagnetic energy, also referred to as electromagnetic radiation.
The applications are they can operate multi number of appliances
without moving from the place where we are .This project describes to
control the Home appliances wirelessly using wireless communication.
When we access the remote by pressing a key, the wireless transmitter
sends a 4 bit code l to the Receiver which is placed in the desired room
as bursts of electromagnetic waves. The Receiver in the other end
detects and captures the code, which are then processed via
microcontroller to retrieve the information they contain. This application
uses ht12d & 433 mhz receiver which will accept signals. The
microcontroller captures the code and controller performs the necessary
action by turning ON/OFF the home appliances. The applications are
they can operate multi number of appliances without moving from the
place where we are .This project describes to control the Home
appliances wirelessly using wireless communication. When we access
the remote by pressing a key, the wireless transmitter sends a 4 bit code
l to the Receiver which is placed in the desired room as bursts of
electromagnetic waves. The Receiver in the other end detects and
captures the code, which are then processed via microcontroller to
retrieve the information they contain. This application uses ht12d & 433
mhz receiver which will accept signals. The microcontroller captures the
code and controller performs the necessary action by turning ON/OFF
the home appliances.
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Chapter: 1
HARDWARE REQUIREMENTS
HARDWARE COMPONENTS
1. MICROCONTROLLER (AT89S52).
2. ENCODER IC (HT12E).
3. DECODER IC (HT12D).
4. WIRELESS MODULE (433MHZ).
5. TRANSFORMER (12-0-12,500MA).
6. DIODE.
7. RESISTOR (10K&1K).
8. RELAY (12v).
9. ELECTRIC BULB.
10.TRANSISTOR (cl100b).
11. MHZ OSCILLATOR (0592).
12. 10 MICROFARAD ELECTROLYTIC CAPACITTOR.
13. GENERAL PCB.
14. CERAMIC CAPACITOR (33PF).
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Chapter: 2
Block DiagramBlock Diagram Of Transmitter:
Block Diagram Of Rceiver:
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Chapter: 3
Pin DiagramPin Diagram Of Transmitter:
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Pin Diagram Of Receiver:
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Chapter: 4
Microcontroller(AT89S52)
A Microcontroller (sometimes abbreviated µC, or MCU) is a small computer on a
single integrated circuit containing a process or core ,memory ,and programmable
input/output peripherals. Program memory in the form of NOR flash or OTP ROM is also
often included on chip, as well as a typically small amount of RAM. Microcontrollers are
designed for embedded applications, in contrast to the microprocessors used in personal
computers or other general purpose applications.
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7.1 Description
The AT89S52 is a low-power, high-performance CMOS 8-bit microcontroller with 8K bytesof in-system programmable Flash memory.
The device is manufactured using Atmel‘s high-density nonvolatile memory technology and
is compatible with the industry-standard 80C51 instruction set and pin out. The on-chip Flash
allows the program memory to be reprogrammed in-system or by a conventional nonvolatile
memory programmer. By combining a versatile 8-bit CPU with in-system programmable
Flash on a monolithic chip.
The Atmel AT89S52 is a powerful microcontroller which provides a highly-flexible and cost-
effective solution to many embedded control applications. The AT89S52 provides the
following standard features: 8K bytes of Flash, 256 bytes of RAM, 32 I/O lines, Watchdog
timer, two data pointers, three 16-bit timer/counters, a six-vector two-level interrupt
architecture, a full duplex serial port, on-chip oscillator, and clock circuitry.
In addition, the AT89S52 is designed with static logic for operation down to zero frequency
and supports two software selectable power saving modes. The Idle Mode stops the CPU
while allowing the RAM, timer/counters, serial port, and interrupt system to continue
functioning.
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7.2 Block Diagram
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7.3 Pin Configurations
7.4 Pin Description
PIN 1-8 :
Port 1 is an 8-bit bidirectional I/O port with internal pull-ups. The Port 1 output buffers can
sink/source four TTL inputs. When 1s are written to Port 1 pins, they are pulled high by the
internal pull-ups and can be used as inputs. As inputs, Port 1 pins that are externally being
pulled low will source current (IIL) because of the internal pull-ups.
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In addition, P1.0 and P1.1 can be configured to be the timer/counter 2 external count input
(P1.0/T2) and the timer/counter 2 trigger input (P1.1/T2EX), respectively, as shown in the
following table.
Port 1 also receives the low-order address bytes during Flash programming and verification.
PIN 9 : RST Reset input.
A high on this pin for two machine cycles while the oscillator is running resets the device.
This pin drives high for 98 oscillator periods after the Watchdog times out. The DISRTO bit
in SFR AUXR (address 8EH) can be used to disable this feature. In the default state of bit
DISRTO, the RESET HIGH out feature is enabled.
PIN 10-17 :
Port 3 is an 8-bit bidirectional I/O port with internal pull-ups. The Port 3 output buffers can
sink/source four TTL inputs. When 1s are written to Port 3 pins, they are pulled high by the
internal pull-ups and can be used as inputs. As inputs, Port 3 pins that are externally being
pulled low will source current (IIL) because of the pull-ups.
Port 3 receives some control signals for Flash programming and verification. Port 3 also
serves the functions of various special features of the AT89S52, as shown in the following
table.
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PIN 18 : XTAL2 Output from the inverting oscillator amplifier.
PIN 19 : XTAL1 Input to the inverting oscillator amplifier and input to the inter clock
operating circuit.
PIN 20 : GND
PIN 21-28 :
Port 2 is an 8-bit bidirectional I/O port with internal pull-ups. The Port 2 output buffers can
sink/source four TTL inputs. When 1s are written to Port 2 pins, they are pulled high by the
internal pull-ups and can be used as inputs. As inputs, Port 2 pins that are externally being
pulled low will source current (IIL) because of the internal pull-ups.
Port 2 emits the high-order address byte during fetches from external program memory and
during accesses to external data memory that use 16-bit addresses (MOVX @ DPTR). In this
application, Port 2 uses strong internal pull-ups when emitting 1s. During accesses to external
data memory that use 8-bit addresses (MOVX @ RI), Port 2 emits the contents of the P2
Special Function Register.
Port 2 also receives the high-order address bits and some control signals during Flash
programming and verification.
PIN 29 : PSEN
Program Store Enable (PSEN) is the read strobe to external program memory. When the
AT89S52 is executing code from external program memory, PSEN is activated twice each
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machine cycle, except that two PSEN activations are skipped during each access to external
data memory.
PIN 30 : ALE/PROG
Address Latch Enable (ALE) is an output pulse for latching the low byte of the address
during accesses to external memory. This pin is also the program pulse input (PROG) during
Flash programming.
In normal operation, ALE is emitted at a constant rate of 1/6 the oscillator frequency and
may be used for external timing or clocking purposes. Note, however, that one ALE pulse is
skipped dur-ing each access to external data memory.
If desired, ALE operation can be disabled by setting bit 0 of SFR location 8EH. With the bit
set, ALE is active only during a MOVX or MOVC instruction. Otherwise, the pin is weakly
pulled high. Setting the ALE-disable bit has no effect if the microcontroller is in external
execution mode.
PIN 31 : EA/VPP
External Access Enable. EA must be strapped to GND in order to enable the device to fetchcode from external program memory locations starting at 0000H up to FFFFH. Note,
however, that if lock bit 1 is programmed, EA will be internally latched on reset. EA should
be strapped to VCC for internal program executions. This pin also receives the 12-volt
programming enable voltage (VPP) during Flash programming.
PIN 32-39 :
Port 0 is an 8-bit open drain bidirectional I/O port. As an output port, each pin cansink eight TTL inputs. When 1s are written to port 0 pins, the pins can be used as high-
impedance inputs.
Port 0 can also be configured to be the multiplexed low-order address/data bus during
accesses to external program and data memory. In this mode, P0 has internal pull-ups.
Port 0 also receives the code bytes during Flash programming and outputs the code bytes
during program verification. External pull-ups are required during program verification.
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Chapter: 5
ENCODER IC (HT12E)
1. GENERAL DESCRIPTION
The 212 encoders are a series of CMOS LSIs for remote control system
applications. They are capable of encoding information which consists of N
address bits and 12_N data bits. Each address/ data input can be set to one of the
two logic states. The programmed addresses/data are transmitted together with
the header bits via an RF or an infrared transmission medium upon receipt of a
trigger signal. The capability to select a TE trigger on the HT12E or a DATA
trigger on the HT12A further enhances the application flexibility of the 212
series of encoders. The HT12A additionally provides a 38kHz carrier for
infrared systems. [10]
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Pin Configuration
Fig.4.12 ENCODER(HT12E)
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2. Pin Description
Table4.5 PIN DESCRIPTION OF HT12E
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3. FEATURES
4. APPLICATIONS
5. BLOCK DIAGRAM
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Fig.4.12 Block diagram of H T12E
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Chapter: 6
DECODER IC (HT12D)
1. Pin Configuration
Fig.4.13 DECODER(HT12)
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2:Pin Description
Table4.6 PIN DESCRIPTION OF HT12D
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3:FEATURES
4:APPLICATIONS
5:GENERAL DESCRIPTION
The 212 decoders are a series of CMOS LSIs for remote control system
applications. They are paired with Holtek_s 212 series of encoders (refer to the
encoder/decoder cross reference table). For proper operation, a pair of
encoder/decoder with the same number of addresses and data format should be
chosen. The decoders receive serial addresses and data from a programmed 212
series of encoders that are transmitted by a carrier using an RF or an IR
transmission medium. They compare the serial input data three times
continuously with their local addresses. If no error or unmatched codes are
found, the input data codes are decoded and then transferred to the output pins.
The VT pin also goes high to indicate a valid transmission. The 212 series of
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decoders are capable of decoding informations that consist of N bits of address
and 12_N bits of data. Of this series, the HT12D is arranged to provide 8
address bits and 4 data bits, and HT12F is used to decode 12 bits of address
information. [11]
6:BLOCK DIAGRAM
Fig.4.12 Block diagram of HT12D
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Chapter: 7 TRANSFORMER
13.1 Introduction
A transformer is a device that transfers electrical energy from one circuit to another through
inductively coupled conductors — the transformer's coils. A varying current in the first or
primary winding creates a varying magnetic flux in the transformer's core and thus a varying
magnetic field through the secondary winding. This varying magnetic field induces a varying
electromotive force (EMF), or "voltage", in the secondary winding. This effect is called
inductive coupling.
If a load is connected to the secondary, 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 (V s) is in
proportion to the primary voltage (V p) and is given by the ratio of the number of turns in the
secondary (Ns) to the number of turns in the primary (N p) as follows:
By appropriate selection of the ratio of turns, a transformer thus enables an alternating current
(AC) voltage to be "stepped up" by making Ns greater than N p, or "stepped down" by making
Ns less than N p.
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 on 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")
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voltage. Transformers are essential for high-voltage electric power transmission, which
makes long-distance transmission economically practical.
13.2 Working
Figure : Transformer
The transformer is based on two principles: first, that an electric current can produce a
magnetic field (electromagnetism) and second that a changing magnetic field within a coil of
wire induces a voltage across the ends of the coil (electromagnetic induction). Changing the
current in the primary coil changes the magnetic flux that is developed. The changing
magnetic flux induces a voltage in the secondary coil.
An ideal transformer is shown in the adjacent figure. Current passing through the primary
coil creates a magnetic field. The primary and secondary coils are wrapped around a core of
very high magnetic permeability, such as iron, so that most of the magnetic flux passes
through both the primary and secondary coils. If a load is connected to the secondary
winding, the load current and voltage will be in the directions indicated, given the primarycurrent and voltage in the directions indicated (each will be alternating current in practice).
The ideal transformer model assumes that all flux generated by the primary winding links all
the turns of every winding, including itself. In practice, some flux traverses paths that take it
outside the windings. Such flux is termed leakage flux, and results in leakage inductance in
series with the mutually coupled transformer windings. Leakage results in energy being
alternately stored in and discharged from the magnetic fields with each cycle of the power
supply. It is not directly a power loss (see "Stray losses" below), but results in inferior voltage
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regulation, causing the secondary voltage to not be directly proportional to the primary
voltage, particularly under heavy load. Transformers are therefore normally designed to have
very low leakage inductance. Nevertheless, it is impossible to eliminate all leakage flux
because it plays an essential part in the operation of the transformer. The combined effect of
the leakage flux and the electric field around the windings is what transfers energy from the
primary to the secondary.
Air gaps are also used to keep a transformer from saturating, especially audio-frequency
transformers in circuits that have a direct current component flowing through the windings.
13.3 Step Down Transformer
A step down transformer is a device that has its secondary voltage less than its primary
voltage. This transformer reduces voltage and often ranges in sizes from 0.5 kva to 500 kva.
The uses of step down transformers range from large devices used in our electrical power
systems to smaller units found in electronic equipment. In our electrical power systems, a
step up transformer is used at power plants to carry current through transmission lines.
Before the electricity's arrival at its final destination, a step down transformer is used to lower
voltage input. In electronic equipment, step down transformers are used largely ahead of a
rectifier. These step down transformers, which primarily are the 1-100-W power level, areused in loudspeakers in radios, television sets and high fidelity equipment. They are
sometimes called audio transformers, and they reproduce sound-wave frequencies with
minimal distortion over the full sound power levels.
Working
The basic concept of a transformer is that is has step up or step down power. Without these
transformers, distribution of our electric power over long distances would be impossible.
There a primary circuit and a secondary circuit. There is no connection between the two
circuits, but each of these circuits contains a winding, which links it inductively to the other
circuits. The windings are wound onto an iron core. The iron core channels the magnetic flux
generated by the current flowing around the primary winding, and as much as possible, also
links the secondary winding. The ratio of the peak voltages and peak currents in the primary
and secondary windings are determined by the ratio of the number of turns in the primary and
secondary windings. The latter ratio is usually called the turn ratio of the transformer.
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Chapter: 8
CAPACITOR
A capacitor (originally known as condenser) is a passive two-terminal electrical component
used to store energy in an electric field. The forms of practical capacitors vary widely, but all
contain at least two electrical conductors separated by a dielectric (insulator); for example,
one common construction consists of metal foils separated by a thin layer of insulating film.
Capacitors are widely used as parts of electrical circuits in many common electrical devices.
When there is a potential difference (voltage) across the conductors, a static electric field
develops across the dielectric, causing positive charge to collect on one plate and negative
charge on the other plate. Energy is stored in the electrostatic field. An ideal capacitor is
characterized by a single constant value, capacitance, measured in farads. This is the ratio of
the electric charge on each conductor to the potential difference between them.
The capacitance is greatest when there is a narrow separation between large areas of
conductor, hence capacitor conductors are often called "plates," referring to an early means of
construction. In practice, the dielectric between the plates passes a small amount of leakagecurrent and also has an electric field strength limit, resulting in a breakdown voltage, while
the conductors and leads introduce an undesired inductance and resistance.
Capacitors are widely used in electronic circuits for blocking direct current while allowing
alternating current to pass, in filter networks, for smoothing the output of power supplies, in
the resonant circuits that tune radios to particular frequencies, in electric power transmission
systems for stabilizing voltage and power flow, and for many other purposes.
9.2 Theory of operation
A capacitor consists of two conductors separated by a non-conductive region. The non-
conductive region is called the dielectric. In simpler terms, the dielectric is just an electrical
insulator. Examples of dielectric media are glass, air, paper, vacuum, and even 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
any external electric field. The conductors thus hold equal and opposite charges on their
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facing surfaces, and the dielectric develops an electric field. 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.
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:
9.3 Energy of electric field
Work must be done by an external influence to "move" charge between the conductors in a
capacitor. When the external influence is removed the charge separation persists in the
electric field and energy is stored to be released when the charge is allowed to return to its
equilibrium position. The work done in establishing the electric field, and hence the amount
of energy stored, is given by:
9.4 Current-voltage relation
The current i(t) through any component in an electric circuit is defined as the rate of flow of a
charge q(t) passing through it, but actual charges, electrons, cannot pass through the dielectric
layer of a capacitor, rather an electron accumulates on the negative plate for each one that
leaves the positive plate, resulting in an electron depletion and consequent positive charge on
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one electrode that is equal and opposite to the accumulated negative charge on the other.
Thus the charge on the electrodes is equal to the integral of the current as well as proportional
to the voltage as discussed above. As with any antiderivative, a constant of integration is
added to represent the initial voltage v (t0). This is the integral form of the capacitor equation,
.
Taking the derivative of this, and multiplying by C, yields the derivative form,
.
The dual of the capacitor is the inductor, which stores energy in a magnetic field rather than
an electric field. Its current-voltage relation is obtained by exchanging current and voltage in
the capacitor equations and replacing C with the inductance L.
9.5 Networks Connection
For capacitors in parallel
Capacitors in a parallel configuration each have the same applied voltage. Their capacitances
add up. Charge is apportioned among them by size. Using the schematic diagram to visualize
parallel plates, it is apparent that each capacitor contributes to the total surface area.
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For capacitors in series
Several capacitors in series.
Connected in series, the schematic diagram reveals that the separation distance, not the plate
area, adds up. The capacitors each store instantaneous charge build-up equal to that of every
other capacitor in the series. The total voltage difference from end to end is apportioned to
each capacitor according to the inverse of its capacitance. The entire series acts as a capacitor
smaller than any of its components.
Capacitors are combined in series to achieve a higher working voltage, for example for
smoothing a high voltage power supply.
9.6 Capacitor Used
1. Ceramic Capacitor : Ceramic capacitors are generally small, cheap and useful for high
frequency applications, although their capacitance varies strongly with voltage and they age
poorly. Ceramic capacitors are often used in resonators.
Ceramic Capacitor
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2. Electrolytic Capacitor : Electrolytic capacitors are used to store small and larger amounts
of energy. These capacitors use an aluminum or tantalum plate with an oxide dielectric layer.
The second electrode is a liquid electrolyte, connected to the circuit by another foil plate.
Electrolytic capacitors offer very high capacitance but suffer from poor tolerances, high
instability, gradual loss of capacitance especially when subjected to heat, and high leakage
current.
Electrolytic Capacitor
9.7 Capacitor Markings
Most capacitors have numbers printed on their bodies to indicate their electrical
characteristics. Larger capacitors like electrolytics usually display the actual capacitance
together with the unit (for example, 220 μF). Smaller capacitors like ceramics, however, use a
shorthand consisting of three numbers and a letter, where the numbers show the capacitance
in pF (calculated as XY × 10Z for the numbers XYZ) and the letter indicates the tolerance (J,
K or M for ±5%, ±10% and ±20% respectively).
Example :A capacitor with the text 473K 330V on its body has a capacitance of 47 × 10 3 pF
= 47 nF (±10%) with a working voltage of 330 V.
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Chapter: 9
RESISTOR
A resistor is a passive two-terminal electrical component that implements electrical resistance
as a circuit element. The current through a resistor is in direct proportion to the voltage across
the resistor's terminals. Thus, the ratio of the voltage applied across a resistor's terminals to
the intensity of current through the circuit is called resistance. This relation is represented by
Ohm's law:
where I is the current through the conductor in units of amperes, V is the potential difference
measured across the conductor in units of volts, and R is the resistance of the conductor in
units of ohms. More specifically, Ohm's law states that the R in this relation is constant,
independent of the current. Resistors are common elements of electrical networks and
electronic circuits and are ubiquitous in electronic equipment. Practical resistors can be made
of various compounds and films, as well as resistance wire (wire made of a high-resistivityalloy, such as nickel-chrome). Resistors are also implemented within integrated circuits,
particularly analog devices, and can also be integrated into hybrid and printed circuits
RESISTOR
The ohm (symbol: Ω) is the SI unit of electrical resistance, named after Georg Simon Ohm.
An ohm is equivalent to a volt per ampere. Since resistors are specified and manufactured
over a very large range of values, the derived units of milliohm (1 mΩ = 10−3 Ω), kilohm (1
kΩ = 103 Ω), and megohm (1 MΩ = 106 Ω) are also in common usage.
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10.2 Theory of operation
Ohm's law
The behavior of an ideal resistor is dictated by the relationship specified by Ohm's law:
Ohm's law states that the voltage (V) across a resistor is proportional to the current (I), where
the constant of proportionality is the resistance (R).
Equivalently, Ohm's law can be stated:
This formulation states that the current (I) is proportional to the voltage (V) and inversely
proportional to the resistance (R). This is directly used in practical computations.
For example, if a 300 ohm resistor is attached across the terminals of a 12 volt battery, then a
current of 12 / 300 = 0.04 amperes (or 40 milliamperes) occurs across that resistor.
10.3 Networks Connection
For Resistors in series
In a series configuration, the current through all of the resistors is the same, but the voltage
across each resistor will be in proportion to its resistance. The potential difference (voltage)
seen across the network is the sum of those voltages, thus the total resistance can be found as
the sum of those resistances:
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As a special case, the resistance of N resistors connected in series, each of the same resistance
R, is given by NR.
For Resistors in parallel
Resistors in a parallel configuration are each subject to the same potential difference
(voltage), however the currents through them add. The conductance‘s of the resistors then
add to determine the conductance of the network. Thus the equivalent resistance ( Req) of the
network can be computed:
The parallel equivalent resistance can be represented in equations by two vertical lines "||" (as
in geometry) as a simplified notation. Occasionally two slashes "//" are used instead of "||", in
case the keyboard or font lacks the vertical line symbol. For the case of two resistors in
parallel, this can be calculated using:
As a special case, the resistance of N resistors connected in parallel, each of the same
resistance R, is given by R/N.
10.4 Resistor marking
Most axial resistors use a pattern of colored stripes to indicate resistance. Surface-mount
resistors are marked numerically, if they are big enough to permit marking; more-recent small
sizes are impractical to mark. Cases are usually tan, brown, blue, or green, though other
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colors are occasionally found such as dark red or dark gray. Early 20th century resistors,
essentially uninsulated, were dipped in paint to cover their entire body for color coding. A
second color of paint was applied to one end of the element, and a color dot (or band) in the
middle provided the third digit. The rule was "body, tip, dot", providing two significant digits
for value and the decimal multiplier, in that sequence. Default tolerance was ±20%. Closer-
tolerance resistors had silver (±10%) or gold-colored (±5%) paint on the other end.
10.5 Resistance Used
1 kΩ resistor 10 kΩ resistor
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Chapter:10
RF Module
RF Tag
Figure : RF TAG
An RFID tag is a microchip combined with an antenna in a compact package; the packaging
is structured to allow the RFID tag to be attached to an object to be tracked. "RFID" stands
for Radio Frequency Identification.
The tag's antenna picks up signals from an RFID reader or scanner and then returns the
signal, usually with some additional data (like a unique serial number or other customized
information).
RFID tags can be very small - the size of a large rice grain. Others may be the size of a small
paperback book.
15.2 RF Tag Antenna
The antenna in an RFID tag is a conductive element that permits the tag to exchange data
with the reader. Passive RFID tags make use of a coiled antenna that can create a magnetic
field using the energy provided by the reader's carrier signal.
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15.3 Tag cost
The cost of tags depends on their type. In the 2003 report ‗RFID Systems in the
Manufacturing Supply Chain‘, ARC Advisory Group predicted the following decrease of tag
prices:
Price in 2003Estimated price
in 2008
Passive UHF tag 57 cents 16 cents
Passive HF tag 91 cents 30 cents
This predicted decrease is still deemed insufficient, as economic use of tags — taking the
associated 5 – 35% decrease of labor costs and zero tag information generation costs into
account as well — would require a maximum of 25 cents per tag for high-end products, and 5
cents for common item-level tagging.
Prices of active or semi-passive tags (at least $1 per tag) are even more of a hindrance,
allowing their economic application only for scanning high-value goods over long ranges.
15.4 Frequency
The optimal choice of frequency depends on several factors, such as:
a.) Transmission mode. RFID tags basically use two kinds of data transmission, depending
on the behavior of electromagnetic fields at the frequency used. In lower frequencies (such as
125 – 134kHz in the LF band or 13.56MHz in the HF band), inductive coupling is used, while
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in frequency bands above (UHF with typical frequency ranges of 433MHz, 865 – 956MHz and
2.45GHz), wave backscattering is the main means of transmission. This also affects the safe
reading range, as it is easier to build direction-selective devices with a longer read range in
higher frequencies. This may restrict design freedom if either reading range or spatial
selectivity are an important issue.
b.) Behavior of tagged goods and environment. Properties of some materials may be an
obstacle to RFID application at a given frequency, as they may corrupt data transmission
either by absorption or by ambient reflection of the signals. Typically, conductive materials
such as goods containing water, or metal surfaces may be the source of problems. However,
absorption and reflection being frequency-dependent, failure at one frequency does not rule
out applicability at other frequencies. Electromagnetic disturbance can also have external
sources, which is also a common — though also frequency-dependent — problem in an
industrial environment.
c.) International standards in frequency allocation. Due to historic reasons, the world is
divided into three large regions of frequency allocation for various purposes, region 1
containing Europe, Africa, the Middle East and former SU member states, region 2 with
North and South America and the part of the Pacific east of the date line, and region 3 with
Asia, Australia and the Pacific west of the date line. The industry exerts pressure towards a
uniformization of frequencies allowed for RFID, yet there still are notable differences
between the three regions, forcing companies planning to employ tags in several regions to
restricting themselves to bands shared by all regions concerned. A compromise for tags only
modulating the reader signal without actively producing a carrier wave on their own may be
their ability to work in a wider frequency range than nominally specified, allowing their
usage even in regions where RFID bands are ‗close enough‘.
RF TRANSCEIVER 433 MHz MODULE
These RF Transmitter Modules are very small in dimension and have a wide
operating voltage range (3V-12V). The low cost RF Transmitter can be used to
transmit signal up to 100 meters (the antenna design, working environment and
supply voltage will seriously impact the effective distance). It is good for short
distance, battery power device development. Cytron Technologies provides 2
types of RF Transmitter Modules at either 315MHz or 433MHz for user:
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The application includes:
• Industrial remote control, telemetry and remote sensing.
• Alarm systems and wireless transmission for various types of low-rate
digital signal.
• Remote control for various types of household appliances and
electronics projects. [9]
1. PRODUCT SPECIFICATION
1.1 The Specifications of RF Transmitter Module
Except for the frequency and antenna length, RF_TX_315 and RF_TX_433
share the same product specifications as shown in table below:
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Chapter:11
DIODE
Introduction
A diode is a two-terminal electronic component with asymmetric transfer characteristic,
with low (ideally zero) resistance to current flow in one direction, and high (ideally infinite)
resistance in the other. A semiconductor diode, the most common type today, is a crystalline
piece of semiconductor material with a p-n junction connected to two electrical
terminals. A vacuum tube diode. now rarely used except in some high-power technologies
and by enthusiasts, is a vacuum tube with two electrodes, a plate (anode) and cathode.
The most common function of a diode is to allow an electric current to pass in one direction
(called the diode's forward direction), while blocking current in the opposite direction
(the reverse direction). Thus, the diode can be thought of as an electronic version of a check
valve. This unidirectional behavior is called rectification, and is used to convert alternating
current to direct current, including extraction of modulation from radio signals in radio
receivers — these diodes are forms of rectifiers.
Semiconductor diodes' nonlinear current – voltage characteristic can be tailored by varying
the semiconductor materials and introducing impurities into (doping) the materials. These are
exploited in special purpose diodes that perform many different functions. For example,
diodes are used to regulate voltage (Zener diodes), to protect circuits from high voltage
surges (avalanche diodes), to electronically tune radio and TV receivers (varactor diodes), to
generate radio frequency oscillations (tunnel diodes, Gunn diodes, IMPATT diodes), and to
produce light (light emitting diodes). Tunnel diodes exhibit negative resistance, which makes
them useful in some types of circuits.
12.2 Physical Structure & working
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A diode is an electrical device allowing current to move through it in one direction with far
greater ease than in the other. The most common kind of diode in modern circuit design is
the semiconductor diode, although other diode technologies exist. Semiconductor diodes are
symbolized in schematic diagrams such as Figure below. The term ―diode‖ is customarily
reserved for small signal devices, I ≤ 1 A. The term rectifier is used for power devices, I > 1
A.
Diode representations: PN-junction model, schematic symbol, physical part.
Working
When placed in a simple battery-lamp circuit, the diode will either allow or prevent current
through the lamp, depending on the polarity of the applied voltage. (Figure below)
Diode operation: (a) Current flow is permitted; the diode is forward biased. (b) Current flow
is prohibited; the diode is reversed biased.
When the polarity of the battery is such that electrons are allowed to flow through the diode,
the diode is said to be forward-biased. Conversely, when the battery is ―backward‖ and
the diode blocks current, the diode is said to be reverse-biased. A diode may be thought of as
like a switch: ―closed‖ when forward- biased and ―open‖ when reverse-biased.
Oddly enough, the direction of the diode symbol's ―arrowhead‖ points against the direction of
electron flow. This is because the diode symbol was invented by engineers, who
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predominantly use conventional flow notation in their schematics, showing current as a flow
of charge from the positive (+) side of the voltage source to the negative (-). This convention
holds true for all semiconductor symbols possessing ―arrowheads:‖ the arrow points in the
permitted direction of conventional flow, and against the permitted direction of electron flow.
12.3 V-I Characteristic
Diode curve : showing knee at 0.7 V forward bias for Si, and reverse breakdown.
A semiconductor diode‘s behavior in a circuit is given by its current – voltage characteristic, or
I – V graph (see graph below). The shape of the curve is determined by the transport of charge
carriers through the so-called depletion layer or depletion region that exists at the p – n
junction between differing semiconductors. When a p – n junction is first created, conduction-
band (mobile) electrons from the N-doped region diffuse into the P-doped region where there
is a large population of holes (vacant places for electrons) with which the electrons
"recombine". When a mobile electron recombines with a hole, both hole and electron vanish,
leaving behind an immobile positively charged donor (dopant) on the N side and negativelycharged acceptor (dopant) on the P side. The region around the p – n junction becomes
depleted of charge carriers and thus behaves as an insulator.
However, the width of the depletion region (called the depletion width) cannot grow without
limit. For each electron – hole pair that recombines, a positively charged dopant ion is left
behind in the N-doped region, and a negatively charged dopant ion is left behind in the P-
doped region. As recombination proceeds more ions are created, an increasing electric field
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develops through the depletion zone that acts to slow and then finally stop recombination. At
this point, there is a "built-in" potential across the depletion zone.
If an external voltage is placed across the diode with the same polarity as the built-in
potential, the depletion zone continues to act as an insulator, preventing any significant
electric current flow (unless electron/hole pairs are actively being created in the junction by,
for instance, light. see photodiode). This is the reverse bias phenomenon. However, if the
polarity of the external voltage opposes the built-in potential, recombination can once again
proceed, resulting in substantial electric current through the p – n junction (i.e. substantial
numbers of electrons and holes recombine at the junction). For silicon diodes, the built-in
potential is approximately 0.7 V (0.3 V for Germanium and 0.2 V for Schottky). Thus, if an
external current is passed through the diode, about 0.7 V will be developed across the diode
such that the P-doped region is positive with respect to the N-doped region and the diode is
said to be "turned on" as it has a forward bias.
12.4 Diode Equation
12.5 Numbering and coding schemes
There are a number of common, standard and manufacturer-driven numbering and coding
schemes for diodes; the two most common being the EIA/JEDEC standard and the European
Pro Electron standard:
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EIA/JEDEC -A standardized 1N-series numbering system was introduced in the US by
EIA/JEDEC (Joint Electron Device Engineering Council) about 1960. Among the most
popular in this series were: 1N34A/1N270 (Germanium signal), 1N914/1N4148 (Silicon
signal), 1N4001-1N4007 (Silicon 1A power rectifier) and 1N54xx (Silicon 3A power
rectifier).Pro ElectronThe European Pro Electron coding system for active components was
introduced in 1966 and comprises two letters followed by the part code. The first letter
represents the semiconductor material used for the component (A = Germanium and B =
Silicon) and the second letter represents the general function of the part (for diodes: A = low-
power/signal, B = Variable capacitance, X = Multiplier, Y = Rectifier and Z = Voltage
reference), for example:
AA-series germanium low-power/signal diodes (e.g.: AA119)
BA-series silicon low-power/signal diodes (e.g.: BAT18 Silicon RF Switching Diode)
BY-series silicon rectifier diodes (e.g.: BY127 1250V, 1A rectifier diode)
BZ-series silicon Zener diodes (e.g.: BZY88C4V7 4.7V Zener diode)
Other common numbering / coding systems (generally manufacturer-driven) include:
GD-series germanium diodes (e.g.: GD9) — this is a very old coding system
OA-series germanium diodes (e.g.: OA47) — a coding sequence developed
by Mullard, a UK company As well as these common codes, many manufacturers or
organisations have their own systems too — for example:
HP diode 1901-0044 = JEDEC 1N4148
UK military diode CV448 = Mullard type OA81 = GEC type GEX23
12.6 Diode Used
Diode 1N4007
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Chapter: 12
Antenna1. User may use any soft or hard wire (likes Drawbars antenna) as antenna.
The frequency is determined by the length of antenna, please select the
correct length with refer to specification of RF Transmitter above.
If a soft wire is used, please make sure it is fully extended.
2. If the transmitter module is molded in a metal casing, please use an
external antenna. [9]
For better result, use A 50 Ohm coaxial cable can be used as antenna to themodule.
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Fig.4.11 RF TRANSMITTER AND RECEI VER
- PIN DESCRIPTION
RF Transmitter
Pin No Function Name 1 Ground (0V) Ground 2 Serial data input pin Data 3 Supply voltage; 5V Vcc 4 Antenna output pin ANT
RF Receiver
Pin No Function Name 1 Ground (0V) Ground 2 Serial data output pin Data 3 Linear output pin; not connected NC 4 Supply voltage; 5V Vcc 5 Supply voltage; 5V Vcc 6 Ground (0V) Ground 7 Ground (0V) Ground 8 Antenna input pin ANT
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Chapter: 13
RectifierA rectifier is an electrical device that converts alternating current (AC), which
periodically reverses direction, to directcurrent (DC), current that flows in only
one direction, a process known as rectification. Rectifiers have many
uses including as components of powersupplies and as detectors of radio signals. Rectifiers
may be made of solidstate
diodes
, vacuumtube
diodes, mercuryarc valves
, and other components. Theoutput from the transformer is fed to the rectifier. It converts A.C. into
pulsating D.C. The rectifier may be a half wave or a full wave rectifier. In
this project, a bridge rectifier is used because of its merits like good
stability and full wave rectification. In positive half cycle only two
diodes( 1 set of parallel diodes) will conduct, in negative half cycle
remaining two diodes will conduct and they will conduct only in
forward bias only.
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Chapter: 14
FilterCapacitive filter is used in this project. It removes the ripples from the
output of rectifier and smoothens the D.C. Output received from this
filter is constant until the mains voltage and load is maintained
constant. However, if either of the two is varied, D.C. voltage received at
this point changes. Therefore a regulator is applied at the output stage.
The simple capacitor filter is the most basic type of power supply filter.
The use of this filter is very limited. It is sometimes used on extremelyhigh-voltage, low-current power supplies for cathode-ray and similar
electron tubes that require very little load current from the supply. This
filter is also used in circuits where the power-supply ripple frequency is
not critical and can be relatively high. Below figure can show how the
capacitor changes and discharges.
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Chapter: 15
VOLTAGE REGULATOR (7805) Features
• Output Current up to 1A.
• Output Voltages of 5, 6, 8, 9, 10, 12, 15, 18, 24V.
• Thermal Overload Protection.
• Short Circuit Protection.
• Output Transistor Safe Operating Area Protection.
Description
The
LM78XX/LM78XXA series of three-terminal positive regulators are available in the TO-220/D-PAK
package and with several fixed output voltages, making them useful in a Wide range of applications.
Each type employs internal current limiting, thermal shutdown and safe operating area protection,
making it essentially indestructible. If adequate heat sinking is provided, they can deliver over 1A
output Current. Although designed primarily as fixed voltage regulators, these devices can be used
with external components to obtain adjustable voltages and currents.
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Chapter:16
Light Emitting Diode
Introduction
A light-emitting diode (LED) is a semiconductor light source. LEDs are used as indicator
lamps in many devices and are increasingly used for other lighting. Introduced as a practical
electronic component in 1962, early LEDs emitted low-intensity red light, but modern
versions are available across the visible, ultraviolet, and infrared wavelengths, with very high
brightness.
When a light-emitting diode is forward-biased (switched on), electrons are able to recombine
with electron holes within the device, releasing energy in the form of photons. This effect iscalled electroluminescence and the color of the light (corresponding to the energy of the
photon) is determined by the energy gap of the semiconductor. LEDs are often small in area
(less than 1 mm2), and integrated optical components may be used to shape its radiation
pattern. LEDs present many advantages over incandescent light sources including lower
energy consumption, longer lifetime, improved robustness, smaller size, and faster switching.
LEDs powerful enough for room lighting are relatively expensive and require more precise
current and heat management than compact fluorescent lamp sources of comparable output.
LED Symbol
.
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11.2 Physical Structure
Figure : LED Structure
LED is a two terminal device i.e. Anode and Cathode.
11.3 Working
Figure : Working of LED
The LED consists of a chip of semiconducting material doped with impurities to create a p-n
junction. As in other diodes, current flows easily from the p-side, or anode, to the n-side, or
cathode, but not in the reverse direction. Charge-carriers — electrons and holes — flow into the
junction from electrodes with different voltages. When an electron meets a hole, it falls into a
lower energy level, and releases energy in the form of a photon.
The wavelength of the light emitted, and thus its color depends on the band gap energy of the
materials forming the p-n junction. In silicon or germanium diodes, the electrons and holes
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recombine by a non-radiative transition, which produces no optical emission, because these
are indirect band gap materials. The materials used for the LED have a direct band gap with
energies corresponding to near-infrared, visible, or near-ultraviolet light.
LED development began with infrared and red devices made with gallium arsenide.
Advances in materials science have enabled making devices with ever-shorter wavelengths,
emitting light in a variety of colors.
LEDs are usually built on an n-type substrate, with an electrode attached to the p-type layer
deposited on its surface. P-type substrates, while less common, occur as well. Many
commercial LEDs, especially GaN/InGaN, also use sapphire substrate.
Most materials used for LED production have very high refractive indices. This means thatmuch light will be reflected back into the material at the material/air surface interface. Thus,
light extraction in LEDs is an important aspect of LED production, subject to much research
and development.
11.4 Different types of LED
The different types of LED‘s are as follows :
F lashing LEDs are used as attention seeking indicators without requiring external
electronics. Flashing LEDs resemble standard LEDs but they contain an integrated
multivibrator circuit that causes the LED to flash with a typical period of one second.
In diffused lens LEDs this is visible as a small black dot. Most flashing LEDs emit
light of one color, but more sophisticated devices can flash between multiple colors
and even fade through a color sequence using RGB color mixing.
Bi-color LEDs are two different LED emitters in one case. There are two types of
these. One type consists of two dies connected to the same two leads antiparallel to
each other. Current flow in one direction emits one color, and current in the opposite
direction emits the other color. The other type consists of two dies with separate leads
for both dies and another lead for common anode or cathode, so that they can be
controlled independently.
Tri-color LEDs are three different LED emitters in one case. Each emitter is
connected to a separate lead so they can be controlled independently. A four-lead
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How It WorksBy integrating a mechanical limit switch with an IEEE 802.15.4
trans receiver , these wireless limit switches can communicatetheir position changes to a monitoring receiver that can handle
multiple switches in a star configuration network. Every network,
and each switch within the network, has a unique identification
number.
These identification numbers allow a switch and its associated
monitor to encode their signals so that the communications link
between them is both private and virtually immune to crosstalk
from other switches or networks. 802.15.4 radios provideexcellent results in large single room and outdoor installations
with a relatively open line-of-sight between switch and monitor. A
35-dB link margin ensures that minor obstacles or even intense
precipitation will not compromise communications. Depending
on composition, the signal can penetrate intervening walls in
some installations.
An 802.15.4 radio allowable operating range is more than 1000
feet (304 meters). In extreme conditions such as heavyprecipitation, rain or snow, the signal could be reduced by
approximately 75 feet (23 meters).
To ensure reliable operation and provide for almost limitless
options for installation, 802.15.4 draws so little power that the
switches can be operated by industry standard batteries rather
than depending on situation-dependent, unreliable ,and
expensive energy scavenging. With the proper design, a wireless
switch should be able to operate for several years without abattery replacement or re-charging.
The monitor/receiver unit that forms the other half of a wireless
switch installation can be designed to support a single switch or
multiple switches. For example, the Honeywell Limitless WDRR
receiver can support up to 14 different remote battery-powered
wireless limit switches. In addition to switch activation status, the
controller can also monitor the signal strength and battery levels
for each individual switch on its network.
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Conclusion
Wireless limit switches can lower equipment costs in a variety of
ways. For one, the cost of manufacturing and installation is
reduced. Not only is the expense of wiring eliminated, there are
no conduits, clips or connectors required to place a limit switch
where it is needed. There are no wire routing problems to solve,
no need for pulling wire during installation and fewer restrictions
on location and placement of the limit switch.
Wireless limit switches can also reduce maintenance
costs.Equipment wiring is less complex with the elimination of
wired switches from the mix, simplifying troubleshooting and
reducing commissioning time. Further, going wireless increases
system reliability by eliminating the potential for having
continuity issues with switch wiring or connectors. Switches also
become simpler to replace, with no need to disconnect and re-attach wiring and no risk of incorrect wire attachment.
Global limit switches are an essential element of industrial and
transportation controls, monitoring position and presence of
doors, booms and valves. Conventional wired switches, however,
present installation and maintenance challenges, especially in
installations that are subject to harsh environments or involve
frequent flexing in the wiring.ÿIn some cases, traditional wirescan represent tripping hazards or can be compromised during
normal equipment operation, thus causing expensive machine
down-time.
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ResultReceiver:
Transmitter:
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Bibliography
Reference Books:
1. Weis, Stephen A. (2007), RFID (Radio Frequency Identification): Principles andApplications, MIT CSAIL,
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2. Daniel M. Dobkin, The RF in RFID: Passive UHF RFID In Practice, Newnes 2008
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3. John R. Vacca Computer and information security handbook, Morgan Kaufmann,
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