Chapter # 1 1

TABLE OF CONTENTS
Preface i
Acknowledgement iii
Abstract v
Chapter # 1 INTRODUCTION 1
1.1 Background 1
1.2 Introduction 1
1.3 Introduction To Power Systems 2
1.4 Power System Alternatives 2
1.6 Types 5
1.6.1 Open Transition 5
1.6.2 Closed Transition 5
1.7 Soft Loading 6
1.7.1 Static Transfer Switch 6
1.8 Applications 6
1.9 Home Use 7
1.10 Conclusion 7
Chapter # 2 FPGA (FIELD PROGRAMMABLE GATE ARRAY) 8

2.1 Introduction 8
2.2 Background 9
2.3 History 9
2.4 Fpga Programming Overview 11
2.4.1 Mitrion C 12
2.5 Features And Aspects Of The Language 13
2.5.1 Overview 13
2.5.2 Variables 13
2.5.3 Functions 13
2.5.4 Block Expressions 14
2.5.5 Data I/O 14
2.6 Development 14
2.6.1 Program Suitability 14
2.6.2 Interacting With The Fpga 15
2.6.3 Mitrion Sdk Pe 15
2.7 Modern Developments 15
2.8 Gates 16
2.9 Market Size 16
2.10 Fpga Design Starts 17
2.11 Fpga Comparisons 17
2.12 Complex Programmable Logic Devices 18
2.13 Security Considerations 19
2.14 Applications 19
2.15 Architecture 19
2.16 Simplified Example Illustration Of A Logic 21
2.16.1 Logic Block Pin Locations 21
2.17 FPGA Architecture 24
Chapter # 3 OPTOCOUPLER 27
3.1 Introduction 27
3.2 Description 28
3.3 History 29
3.4 Operation 30
3.5 Electric Isolation 30
3.6 Types Of Opto-Isolators 33
3.6.1 Resistive Opto-Isolators 33
3.6.2 Photodiode Opto-Isolators 35
3.6.3 Photo Transistor Opto-Isolators 36
3.6.4 Bidirectional Opto-Isolators 37
3.7 Opto Couplers 38
3.7.1 4n35 38
3.7.2 Description 39
3.6.3 Features 39
3.6.4 Applications 40
Chapter # 4 CONTACTOR 41
4.1 Introduction 41
4.2 Industry Classifications 42
4.3 Features Of Contactors 43
4.4 Contactor – Design And Construction 44
4.5 Working Of Contactor 45
4.6 Component Description 46
4.6.1 AC Contactor Lc1-D09 Description 46
4.6.2 Contactor Ratings 47
Chapter # 5 RELAY 49
5.1 Introduction 49
5.2 Relay Construction 49
5.3 Relay Design 50
5.4 Relay Basics 51
5.4.1 Why Is A Relay Used? 51
5.4.2 Energized Relay (On) 52
5.5 Types Of Relays 54
5.6 Relay My4n 57
5.6.1 Relay Selection 57
5.7 Applications 58
Chapter # 6 A.M.F. (AUTO MAN FAILURE) 60

6.1 Introduction 60
6.2 0peration 61
6.3 Features 61
6.4 Description 62
6.4.1 Dc Supply 62
6.4.2 Cranking Dropouts 62
6.4.3 Max. Current 62
6.4.4 Alternator Input Frequency 62
6.4.5 Start Output 63
6.4.6 Dimensions 63
6.4.7 Charge Fail 63
6.4.8 Operating Temperature Range: 63
Chapter # 7 MOR MANUAL OVER RIDING 64

7.1 Background 64
GLOSSARY
APPENDICES
Appendix A
Time Analysis
Cost Analysis
Appendix B
Flow Chart
Flow Diagram of FPGA
Block Diagram of Overall System
Circuit or Wiring Diagram
Real Picture of ATS Panel
Appendix C
Data Sheets
REFERENCES
LIST OF FIGURES
Figure 2-1 Logic Block Pin Locations 22

Figure 2-2 FPGA Architecture 24
Figure 2-3 Xilinx Spartan3 25
Figure 2-4 Block Diagram of Xilinx Spartan3 25
Figure 3-1 Internal Diagram of Opto Coupler 28
Figure 3-2 Electric Isolation 32
Figure 3-3 Photodiode Opto Isolators 35
Figure 3-4 4N35 38
Figure 4-1 Contactor 41
Figure 4-2 LC1D09 47
Figure 5-1 Relay Construction 50
Figure 5-2 Relay Operation 52
Figure 5-3 Energized Relay (ON) 52
Figure 5-4 De-Energized Relay (OFF) 53
Figure 5-5 Relay MY4N 57
LIST OF TABLE
Table 3-1 Types Of Opto-Isolators 34

Chapter # 1 Introduction
CHAPTER ONE
INTRODUCTION
1.1 BACKGROUND
Formerly UPS was the work which was used for the designated purpose of ATS. The
system was widely used for uninterrupted power supply and reconciled with the
automated supply.
Automation has taken it’s uphold not only in the industrial sector but is making its
mark in home and other purposeful areas of life. Since the day man has started doing
work it has been in search of ways of making his work easier. This is where
automation has helped him to the extremes and made him think of dreams that are
without doubt turned into reality.
1.2 INTRODUCTION
Our project itself is a step towards the fulfillment of one more of man’s creative
thoughts bought into reality. Since our project mainly involves around the importance
of none stop processing in the industrial sector, thus the prime endeavor of our project
is to device a system which automatically switches the power source between the
MAIN and the generator, depending on the source available, thus evidently preventing
any major delay in process controlled system. Such types of systems are well known
in the world as power systems.
As well as transferring the load to the backup generator, an ATS also commands the
backup generator to start, based on the voltage monitored on the primary supply. The
transfer switch isolates the backup generator from the electric utility, when the
generator is on and is providing temporary power. The control capability of a transfer
switch may be manual only, or a combination of automatic and manual. The switch
transition mode of a transfer switch may be Open Transition (OT) (the usual type), or
Closed Transition (CT).
Sir Syed University of Engineering & Technology 1

1.3 INTRODUCTION TO POWER SYSTEMS

A wide variety of natural disasters can cause long-term power outage. Things like
tornadoes, hurricanes, flooding, lightning and blizzards can take out the power for
hours or days at time. Even something as simple as a blown transformer or a car
running into a utility pole can knock out the electricity in an neighborhood for a day
or two.
We are all dependent on electricity, so a power outage of more than a few minutes
becomes pretty annoying. As the duration of a power failure stretches beyond an hour,
there are more severe problems that can cause things to get expensive or dangerous:
 During the winter, a power failure normally disables a home’s heating system. As
the house cools,(depending on where you live) it can become uninhabitable.
 In the case of a running industry, a power failure means delay in fulfilling a
consignment resulting in bad customer relations, eventually affecting the business.
 If there is a medical condition that requires special equipment, a power failure can
create a life-or-death situation.
 If living in a rural area with a private well, a power failure cuts off the water
supply, which is without doubt a major necessity.
1.4 POWER SYSTEM ALTERNATIVES

To generate the normal 220-volt power on an emergency basis, one can select from
the two main option stated on the next page.
1. One can buy an engine-powered generator. The engine can burn gasoline,
diesel or propane.
2. One can buy an inverter and power it from has automobile battery or a deep-
cycle battery he must have purchased for the inverter.
3. To decide which alternative is best, one needs to decide what equipment is t be
operate in the case of a power failure and what amount of power will be needed by
such device.

1.5 UNDERSTANDING YOUR POWER NEEDS

In order to choose the right emergency power source and to size it properly, one needs
to understand something about the power requirements of the devices he plans to
operate.
The basic unit of power measurement is the watt, and with an emergency power
source there are two wattage ratings that are important: steady-state wattage and surge
wattage. A normal 60-watt luminescent light bulb requires, as you would expect, 60
watt, and it requires that wattage both when you turn it on and while it is running. A
ceiling fan motor, on the other hand, might require 150 watts to get it started and 75
watts while it is running. That extra wattage to start the motor is called the surge
wattage and is typical of anything that contains an electric motor. Given in the table
on the next page are the usual wattage of some of the devices found in a typical
household.
Device Typical wattage Surge wattage

Light bulb 60 watts 60 watts
Ceiling fan 75 watts 150 watts
Small black/white 100 watts 150 watts
television 300 watts 400 watts
Color television 400 watts 600 watts
Home computer & monitor 750 watts 1000 watts
Microwave oven 1200 watts 2400 watts
Refrigerator 2400 watts 3600 watts
Well pump 15000 watts 30000 watts
Whole house a/c or heat
pump
As visible from the above chart the heat pump or air conditioner for an entire house
has a huge appetite for power. If once home is equipped with a heat pump and he
wishes to keep the house warm during a power failure in the winter then he should
either purchase a large generator or else he will need a backup heat source such a
wood or propane

One another thin to note is that if one plans to operate sensitive equipment like TVs
and computer from an emergency power supply he must have in place excellent surge
protection equipment specially in the case of a computer an power supply (ups) will
be required when a large device like a refrigerator turns on there is no way that a
small generator will be able to keep power stable during the surge. A ups will be
prevent your computer from crashing during the act up.
To calculate the power need one need to add up the normal and surge wattage figure
for all of the device he wishes to operate simultaneously. Two similar examples are
given of the following page.
a. If one plans to operate a black and white TV and two 60-watt light bulb then he
will need an emergency power supply that has a capacity of at least 220 watts and
a surge capacity of 270 watts rounding up that is 250 watt continues and 300 watt
surge
b. However if one plans to operate his refrigerator a color TV and a microwave
simultaneously he will required 2,250 watts continues and 3,800 watts surge in the
worst case (if all three happen to turn on at exactly the same moment). If person is
willing to manage his power then he must take to sure all three devices do not
turn on at once eventually his surge power requirement is reduced to 2,400 watts
if he is within to operate only one o these devices at a time then because the
refrigerator is the largest power extractor he will need to size his emergency
power system so it is large enough to handle the refrigerator
c. The point made in the second example is about staggering your power
consumption which is quiet important. Generator t end to get very expensive and
bulky in size as their wattage capacity increases.

1.6 TYPES
1.6.1 OPEN TRANSITION

An open transition transfer switch is also called a break before make transfer switch.
A break before make transfer switch breaks contact with one source of power before it
makes contact with another. It prevents back feeding from an emergency generator
back into the utility line. One example is an open transition automatic transfer switch
(ATS). During the split second of the power transfer the flow of electricity is
interrupted. Another example is a manual three position circuit breaker, with utility
power on one side, the generator on the other, and "off" in the middle, which requires
the user to switch through the full disconnect "off" position before making the next
connection.
1.6.2 CLOSED TRANSITION

A closed transition transfer switch is also called a make before break transfer switch.
In a typical emergency system, there is an inherent momentary interruption of power
to the load when it is transferred from one available source to another (keeping in
mind that the transfer may be occurring for reasons other than a total loss of power).
In most cases this outage is inconsequential, particularly if it is less than 1/6 of a
second.
There are some loads, however, that are affected by even the slightest loss of power.
There are also operational conditions where it may be desirable to transfer loads with
zero interruption of power when conditions permit. For these applications, closed
transition transfer switches can be provided. The switch will operate in a make-
before-break mode provided both sources are acceptable and synchronized. Typical
parameters determining synchronization are: voltage difference less than 5%,
frequency difference less than 0.2 Hz, and relative phase angle between the sources of
5 electrical degrees. Since the maximum frequency difference is 0.2 Hz, the engine
will generally be required to be controlled by an isochronous governor.
It is generally required that the closed transition, or overlap time, be less than 100
milliseconds. If either source is not present or not acceptable (such as when normal

power fails) the switch must operate in a break-before-make mode (standard open
transition operation) to ensure no backfeeding occurs.
Closed transition transfer makes code-mandated monthly testing less objectionable

because it eliminates the interruption to critical loads, which occur during traditional
open transition transfer.
With closed transition transfer, the on-site engine generator set is momentarily
connected in parallel with the utility source. This requires getting approval from the
local utility company.
1.7 SOFT LOADING

A soft-loading transfer switch actively changes the amount of load accepted by the
generator.
1.7.1 STATIC TRANSFER SWITCH

A static transfer switch uses power semiconductors such as Silicon-controlled
rectifiers (SCRs) to transfer a load between two sources. Because there are no
mechanical moving parts, the transfer can be completed rapidly, perhaps within a
quarter-cycle of the power frequency. Static transfer switches can be used where a
reliable and independent second source of power is available and it is necessary to
protect the load from even a few power frequency cycles interruption time, or from
any surges or sags in the prime power source.
1.8 APPLICATIONS
Typical load switching applications for which closed transition transfer is desirable
include data processing and electronic loads, certain motor and transformer loads,
load curtailment systems, or anywhere load interruptions of even the shortest duration
are objectionable. A closed transition transfer switch (CTTS) is not a substitute for
a UPS (uninterruptible power supply); a UPS has a built-in stored energy that
provides power for a prescribed period of time in the event of a power failure. A
CTTS by itself simply assures there will be no momentary loss of power when the
load is transferred from one live power source to another.

1.9 HOME USE

Homes with standby generators may use a transfer switch for a few circuits or the
whole home. Different models are available, with both manual and automatic transfer.
Often small transfer switch systems use circuit breakers with an external operating
linkage as the switching mechanism. The linkage operates two circuit breakers in
tandem, closing one while opening the other. Manufacturers of transfer switches can
provide installation guides to select the size of switch and provide recommended
installation procedures. Like all other electrical apparatus, local electrical codes
require transfer switches to carry safety approvals. However, some transfer switches
are sold via the Internet, and there have been problems with counterfeit circuit
breakers.
1.10 CONCLUSION
• In this project, Our FULLY AUTOMATIC FPGA BASED THREE PHASE
ATS PANEL is a combination of extremely powerful electrical structure and its
control system based on latest technology industrial Control systems.
• The setup controlled by FPGA 3E which makes hold of each and every part
involve in the circuitry.
• Key to success is base designing and phase sensing.
• After KESC failure power would be easily switched to inverter.
We have done our best efforts to complete this project in the given time but there is
still some hardships in it we will try our best to over some this problem.

Chapter # 2 FPGA (Field Programmable Gate Array)
CHAPTER TWO
FPGA (FIELD PROGRAMMABLE GATE ARRAY)
2.1 INTRODUCTION
A field-programmable gate array (FPGA) is an integrated circuit designed to be
configured by the customer or designer after manufacturing—hence "field-
programmable". The FPGA configuration is generally specified using a hardware
description language (HDL), similar to that used for an application-specific integrated
circuit (ASIC) (circuit diagrams were previously used to specify the configuration, as
they were for ASICs, but this is increasingly rare). FPGAs can be used to implement
any logical function that an ASIC could perform. The ability to update the
functionality after shipping, partial re-configuration of the portion of the design[1] and
the low non-recurring engineering costs relative to an ASIC design (notwithstanding
the generally higher unit cost), offer advantages for many applications.
FPGAs contain programmable logic components called "logic blocks", and a

hierarchy of reconfigurable interconnects that allow the blocks to be "wired
together"—somewhat like many (changeable) logic gates that can be inter-wired in
(many) different configurations. Logic blocks can be configured to perform
complex combinational functions, or merely simple logic gates likeAND and XOR. In
most FPGAs, the logic blocks also include memory elements, which may be
simple flip-flops or more complete blocks of memory.
In addition to digital functions, some FPGAs have analog features. The most common
analog feature is programmable slew rateand drive strength on each output pin,
allowing the engineer to set slow rates on lightly loaded pins that would
otherwise ring unacceptably, and to set stronger, faster rates on heavily loaded pins on
high-speed channels that would otherwise run too slow. Another relatively common
analog feature is differential comparators on input pins designed to be connected to
differential signaling channels. A few "mixed signal FPGAs" have integrated
peripheral Analog-to-Digital Converters (ADCs) and Digital-to-Analog Converters
(DACs) with analog signal conditioning blocks allowing them to operate as a system-
on-a-chip.[5]Such devices blur the line between an FPGA, which carries digital ones

and zeros on its internal programmable interconnect fabric, and field-programmable

analog array (FPAA), which carries analog values on its internal programmable
interconnect fabric.
2.2 BACKGROUND
FPGA is an acronym for field programmable gate array. It is basically a
programmable hardware device, which can be reconfigured to run different algorithms
in hardware, rather than processing a stream of instructions as is done in a typical
microprocessor. While FPGAs see heavy use in areas like electrical engineering for
integrated circuit prototyping, they have yet to make substantial inroads in the HPC
market since they have traditionally been very expensive and notoriously difficult to
program.
In recent years developments in high-level software tools that target FPGAs have
made them much easier to use as HPC accelerators. They are now utilized as integral
components in HPC systems, having been incorporated in SGI Altix and Cray X-
series supercomputers. Recent developments include FPGAs provided as PCIe cards
(in the same fashion as GPUs) or even as CPU-socket add-ons.
The use of FPGAs in HPC is targeted at data-intensive applications that spend nearly
all of their time in a particular mathematical kernel, which exhibits finely-grained
parallelism, both in terms of being able to provide many independent steams of data
as well as pipelining operations on each stream. It will not aid complex programs that
are constrained by Ahmdal's Law. FPGAs are best at tasks that use short word length
integer or fixed point data, and exhibit a high degree of parallelism.
2.3 HISTORY
The FPGA industry sprouted from programmable read-only memory (PROM)
and programmable logic devices (PLDs). PROMs and PLDs both had the option of
being programmed in batches in a factory or in the field (field programmable),
however programmable logic was hard-wired between logic gates.

In the late 1980s the Naval Surface Warfare Department funded an experiment
proposed by Steve Casselman to develop a computer that would implement 600,000
reprogrammable gates. Casselman was successful and a patent related to the system
was issued in 1992
Some of the industry’s foundational concepts and technologies for programmable

logic arrays, gates, and logic blocks are founded in patents awarded to David W. Page
and LuVerne R. Peterson in 1985.
Xilinx Co-Founders, Ross Freeman and Bernard Vonderschmitt, invented the first
commercially viable field programmable gate array in 1985 – the XC2064. ] The
XC2064 had programmable gates and programmable interconnects between gates, the
beginnings of a new technology and market. The XC2064 boasted a mere 64
configurable logic blocks (CLBs), with two 3-input lookup tables (LUTs) More than
20 years later, Freeman was entered into the National Inventors Hall of Fame for his
invention
Xilinx continued unchallenged and quickly growing from 1985 to the mid-1990s,
when competitors sprouted up, eroding significant market-share. By 1993, Actel was
serving about 18 percent of the market
The 1990s were an explosive period of time for FPGAs, both in sophistication and the
volume of production. In the early 1990s, FPGAs were primarily used in
telecommunications and networking. By the end of the decade, FPGAs found their
way into consumer, automotive, and industrial applications
FPGAs got a glimpse of fame in 1997, when Adrian Thompson, a researcher working
at the University of Sussex, merged genetic algorithm technology and FPGAs to
create a sound recognition device. Thomson’s algorithm configured an array of 10 x
10 cells in a Xilinx FPGA chip to discriminate between two tones, utilising analogue
features of the digital chip. The application of genetic algorithms to the configuration
of devices like FPGAs is now referred to as Evolvable hardware

2.4 FPGA PROGRAMMING OVERVIEW

In the past users had to program an FPGA with a hardware description language like
VHDL/Verilog, a process that required knowledge of circuit timing considerations
and other complex hardware issues.
New high-level languages have been developed that abstract the FPGA system to the
level where a user can program in typical C/Fortran fashion and have that code
automatically translated to a description language. The implementation we've gone
with for school is Mitrion-C.
Once the hardware description for the FPGA has been created, one must then compile
a device specific bitstream which is actually loaded onto the FPGA (much like
firmware for a device in a PC). The process of compiling the bitstream is commonly
referred to as "place and route", or "synthesis". The synthesis software is usually
provided by the hardware vendor who manufactures the FPGA, in the case of the
RC100 FPGA blade this is Xilinx. Their tool, the Xilinx ISE is integrated into the
Mitrion-C SDK, which greatly simplifies this stage of the development process.
Unfortunately, the Xilinx software does not run on Itanium, hence the need for a
second x86 based system (tope) to compile the bitstream.
Once the bitstream has been compiled (it is called a "virtual processor" in Mitrion
parlance) it can be loaded onto the FPGA using the devmgr RASC utility, which
manages bitstreams in a database and loads them when a host program specifies that
they should be used.
In addition to the Mitrion virtual processor, one must also instrument their host
system program to interface with the FPGA. There are a number of APIs for doing so,
Mithal, the Mitrion abstraction layer, is a C and Fortran interface to the virtual
processor on the FPGA provided by Mitrion. An alternative approach is to use the
RASCAL (RASC abstraction layer) which is provided by SGI. General FPGA
programming Issues

FPGA programming is highly non-portable.

Cannot expect code written for a particular FPGA or using a particular SDK to work
elsewhere.
Place and route times are substantial - may require over 1 day of computing time just
to build the FPGA design.
There is only a limited amount of resources on the FPGA.

large kernels, especially ones using double precision, can quickly exhaust available
resources.
2.4.1 MITRION C
CURRENT STATUS
Mitrionics is closing down operations. As such, SHARCNET has no support for the
mitrion platform moving forward. This tutorial may be of interest and users are
certainly able to continue using the software at SHARCNET, however, should one
wish to move forward with FPGA programming beyond the VHDL/Verilog level it is
recommended that they learn a different platform. The Mitrionics IP is being sold
(although there was some potential for it to be open-sourced the shareholders decided
against it).
USAGE AT SHARCNET
The Mitrion-C SDK (and in particular, the Xilinx ISE) are not supported on the
Itanium architecture, so users should not use the SDK on school. This includes the
resource intensive and time-consuming synthesis stage, which must be done on a
seperate machine. Code development and simulation can be done on most platforms.
To compile a bitstream one has to use tope, including the supported version of
Mitrion-C which is installed on the system.

2.5 FEATURES AND ASPECTS OF THE LANGUAGE
2.5.1 OVERVIEW
 At face value similar to many high level languages like C or Fortran
 implicitly parallel language (user doesn't control threads or actively code
parallelism)
 Centers around intrinsic parallelism and data-dependencies while traditional
languages are sequential and focused on order-of-execution.
 Single-Assignment Language (operations can and do occur out of order)
o Can use C pre-processor
o No global variables
2.5.2 Variables
 scalar types include int,uint,bool,float,bits with same meaning as in C
 Ability to use any type of precision; eg. uint:12 == 12 bit unsigned integer,
float:10.9 == float with 10 bit mantissa and 9 bit exponent
 collections of scalars include:
o lists: an ordered stream of data with a specific length, no indexing
o vector: same as list, but can be accessed in any order (it's indexed) and uses
much more buffer space on die
o stream: dynamic length, may contain vectors,scalars,tuples or other streams.
can't contain a list
o all collections can be multidimensional
o tuples: create items for other collections with mixed types
2.5.3 FUNCTIONS
 Similar to C / Fortran
 all variables have to be passed in / out of functions
 Don't have to be fully typed (can be polymorphic)
 Can be nested
 Ability to call external VHDL IP blocks

 Intrinsics exist for some functions, as well as typical operators for different scalar
types.

2.5.4 BLOCK EXPRESSIONS
For each
parallel operation on a collective
For
Sequential (iterative) operation over a collective
Requires at least one variable which has a loop iteration dependency
while
sequential operation over a collective of indeterminate length (specified by data itself)
2.5.5 DATA I/O

 when program starts it expects all input to be in external ram banks, when it ends
results are stored there tokens to reference these are passed to main()
 can use internal ram banks for intermediate data, created with _memcreate internal
ram banks are accessed via instance tokens, these order the I/O
2.6 DEVELOPMENT
2.6.1 PROGRAM SUITABILITY

One typically starts with a high-level program in C/C++/Fortran/etc that shows
potential for being accelerated. It should be amenable to fine-grained parallelism, as
the performance gains in FPGAs are obtained by designing the algorithm such that
many independent operations can occur simultaneously. The clock frequency of an
FPGA is typically slower than on a conventional CPU, but one can do much more in
one clock on the FPGA than on the CPU.
One should have a very good idea of how long various parts of their program take to
run, or in other words, the program should be profiled. It is important to determine
that the nearly all of the execution time occurs during one or more subroutines or
functions, all of which must be parallelizable. The degree to which a particular
algorithm can be accelerated is commonly known as Ahmdal's Law, and applies to
any parallel system.

If the code depends on a language feature that does not exist in Mitrion-C, one can
attempt to program the missing functionality. It may be that the particular algorithm is
poorly suited for the FPGA and / or Mitrion.
2.6.2 INTERACTING WITH THE FPGA

Transfer of data and activation of the accelerated portion of the code on the FPGA is
accomplished by implementing either the SGI RASCAL API or the Mitrion Mithal
API. This does not require significant modification to the host cpu code, but it is
something that one has to take into account when porting their program.
2.6.3 MITRION SDK PE

The Mitrion SDK PE will allow developers to write and simulate programs for the
FPGA. This development platform can be obtained for free after registering at
this registration page. It is available for Windows, Linux and Mac OS X. It is not
necessary for users to download and install this software, as the official SDK version
is accessible on tope, but it may provide for a better development experience.
2.7 MODERN DEVELOPMENTS

A recent trend has been to take the coarse-grained architectural approach a step
further by combining the logic blocks and interconnects of traditional FPGAs with
embedded microprocessors and related peripherals to form a complete "system on a
programmable chip". This work mirrors the architecture by Ron Perlof and Hana
Potash of Burroughs Advanced Systems Group which combined a reconfigurable
CPU architecture on a single chip called the SB24. That work was done in 1982.
Examples of such hybrid technologies can be found in the Xilinx Virtex-II PRO and
Virtex-4 devices, which include one or more PowerPC processors embedded within
the FPGA's logic fabric. The Atmel FPSLIC is another such device, which uses
an AVR processor in combination with Atmel's programmable logic architecture. The
Actel SmartFusion devices incorporate an ARM architecture Cortex-M3 hard
processor core (with up to 512kB of flash and 64kB of RAM) and analog peripherals
such as a multi-channel ADC and DACs to their flash-based FPGA fabric.

In 2010, an extensible processing platform was introduced for FPGAs that fused
features of an ARM high-end microcontroller (hard-core implementations of a 32-bit
processor, memory, and I/O) with an FPGA fabric to make FPGAs easier for
embedded designers to use. By incorporating the ARM processor-based platform into
a 28 nm FPGA family, the extensible processing platform enables system architects
and embedded software developers to apply a combination of serial and parallel
processing to address the challenges they face in designing today's embedded
systems, which must meet ever-growing demands to perform highly complex
functions. By allowing them to design in a familiar ARM environment, embedded
designers can benefit from the time-to-market advantages of an FPGA platform
compared to more traditional design cycles associated with ASICs.
An alternate approach to using hard-macro processors is to make use of soft

processor cores that are implemented within the FPGA logic. MicroBlaze and Nios
II are examples of popular softcore processors.
As previously mentioned, many modern FPGAs have the ability to be reprogrammed

at "run time," and this is leading to the idea of reconfigurable computing or
reconfigurable systems —CPUs that reconfigure themselves to suit the task at hand.
Additionally, new, non-FPGA architectures are beginning to emerge. Software-

configurable microprocessors such as the Stretch S5000 adopt a hybrid approach by
providing an array of processor cores and FPGA-like programmable cores on the
same chip.
2.8 GATES
 1987: 9,000 gates, Xilinx
 1992: 600,000, Naval Surface Warfare Department
 Early 2000s: Millions
2.9 MARKET SIZE

 1985: First commercial FPGA technology invented by Xilinx
 1987: $14 million

 ~1993: >$385 million

 2005: $1.9 billion
 2010 estimates: $2.75 billion
2.10 FPGA DESIGN STARTS

 10,000
 2005: 80,000
 2008: 90,000
2.11 FPGA COMPARISONS

Historically, FPGAs have been slower, less energy efficient and generally achieved
less functionality than their fixed ASIC counterparts. A study has shown that designs
implemented on FPGAs need on average 18 times as much area, draw 7 times as
much dynamic power, and are 3 times slower than the corresponding ASIC
implementations
Advantages include the ability to re-program in the field to fix bugs, and may include
a shorter time to market and lower non-recurring engineering costs. Vendors can also
take a middle road by developing their hardware on ordinary FPGAs, but manufacture
their final version so it can no longer be modified after the design has been
committed.

Xilinx claims that several market and technology dynamics are changing the
ASIC/FPGA paradigm.
Integrated circuit costs are rising aggressively ASIC complexity has lengthened
development time R&D resources and headcount are decreasing Revenue losses for
slow time-to-market are increasing Financial constraints in a poor economy are
driving low-cost technologies These trends make FPGAs a better alternative than
ASICs for a larger number of higher-volume applications than they have been
historically used for, to which the company attributes the growing number of FPGA
design starts (see History).
Some FPGAs have the capability of partial re-configuration that lets one portion of
the device be re-programmed while other portions continue running.
2.12 COMPLEX PROGRAMMABLE LOGIC DEVICES

The primary differences between CPLDs (Complex Programmable Logic Devices)
and FPGAs are architectural. A CPLD has a somewhat restrictive structure consisting
of one or more programmable sum-of-products logic arrays feeding a relatively small
number of clocked registers. The result of this is less flexibility, with the advantage of
more predictable timing delays and a higher logic-to-interconnect ratio. The FPGA
architectures, on the other hand, are dominated by interconnect. This makes them far
more flexible (in terms of the range of designs that are practical for implementation
within them) but also far more complex to design for.
In practice, the distinction between FPGAs and CPLDs is often one of size as FPGAs
are usually much larger in terms of resources than CPLDs. Typically only FPGA's
contain more advanced embedded functions such as adders, multipliers,
memory, serdes and other hardened functions. Another common distinction is that
CPLDs contain embedded flash to store their configuration while FPGAs usually, but
not always, require an external flash

2.13 SECURITY CONSIDERATIONS

With respect to security, FPGAs have both advantages and disadvantages as compared
to ASICs or secure microprocessors. FPGAs' flexibility makes malicious
modifications during fabrication a lower risk. For many FPGAs, the loaded design is
exposed while it is loaded (typically on every power-on). To address this issue, some
FPGAs support bitstream encryption. Researchers published papers highlighting
vulnerabilities in the bitstream encryption of some devices related to the analysis of
the device's power usage fluctuations. These vulnerabilities apply to the current
devices of most FPGA manufacture, including Altera and Xilinx.
2.14 APPLICATIONS
Applications of FPGAs include digital signal processing, software-defined
radio, aerospace and defense systems, ASIC prototyping, medical imaging, computer
vision, speech recognition, cryptography, bioinformatics, computer hardware
emulation, radio astronomy, metal detection and a growing range of other areas.
FPGAs originally began as competitors to CPLDs and competed in a similar space,

that of glue logic for PCBs. As their size, capabilities, and speed increased, they began
to take over larger and larger functions to the state where some are now marketed as
full systems on chips (SoC). Particularly with the introduction of dedicated multipliers
into FPGA architectures in the late 1990s, applications which had traditionally been
the sole reserve of DSPs began to incorporate FPGAs instead.
Traditionally, FPGAs have been reserved for specific vertical applications where the
volume of production is small. For these low-volume applications, the premium that
companies pay in hardware costs per unit for a programmable chip is more affordable
than the development resources spent on creating an ASIC for a low-volume
application. Today, new cost and performance dynamics have broadened the range of
viable applications.
2.15 ARCHITECTURE
The most common FPGA architecture consists of an array of logic blocks (called
Configurable Logic Block, CLB, or Logic Array Block, LAB, depending on vendor),
I/O pads, and routing channels. Generally, all the routing channels have the same

width (number of wires). Multiple I/O pads may fit into the height of one row or the
width of one column in the array.
An application circuit must be mapped into an FPGA with adequate resources. While
the number of CLBs/LABs and I/Os required is easily determined from the design, the
number of routing tracks needed may vary considerably even among designs with the
same amount of logic. For example, a crossbar switch requires much more routing
than a systolic array with the same gate count. Since unused routing tracks increase
the cost (and decrease the performance) of the part without providing any benefit,
FPGA manufacturers try to provide just enough tracks so that most designs that will
fit in terms of Lookup tables (LUTs) and IOs can be routed. This is determined by
estimates such as those derived from Rent's rule or by experiments with existing
designs.
In general, a logic block (CLB or LAB) consists of a few logical cells (called ALM,
LE, Slice etc.). A typical cell consists of a 4-input LUT, a Full adder (FA) and a D-
type flip-flop, as shown below. The LUTs are in this figure split into two 3-input
LUTs. In normal mode those are combined into a 4-input LUT through the left mux.
In arithmetic mode, their outputs are fed to the FA. The selection of mode is
programmed into the middle multiplexer. The output can be either synchronous or
asynchronous, depending on the programming of the mux to the right, in the figure
example. In practice, entire or parts of the FA are put as functions into the LUTs in
order to save space.

2.16 SIMPLIFIED EXAMPLE ILLUSTRATION OF A LOGIC

CELL
ALMs and Slices usually contains 2 or 4 structures similar to the example figure, with
some shared signals.
CLBs/LABs typically contains a few ALMs/LEs/Slices.

In recent years, manufacturers have started moving to 6-input LUTs in their high
performance parts, claiming increased performance
Since clock signals (and often other high-fanout signals) are normally routed via
special-purpose dedicated routing networks in commercial FPGAs, they and other
signals are separately managed.
For this example architecture, the locations of the FPGA logic block pins are shown
below.
2.16.1 LOGIC BLOCK PIN LOCATIONS

Each input is accessible from one side of the logic block, while the output pin can
connect to routing wires in both the channel to the right and the channel below the
logic block.
Each logic block output pin can connect to any of the wiring segments in the channels
adjacent to it.
Similarly, an I/O pad can connect to any one of the wiring segments in the channel
adjacent to it. For example, an I/O pad at the top of the chip can connect to any of the
W wires (where W is the channel width) in the horizontal channel immediately below
it.
Generally, the FPGA routing is un segmented. That is, each wiring segment spans
only one logic block before it terminates in a switch box. By turning on some of the
programmable switches within a switch box, longer paths can be constructed. For

higher speed interconnect, some FPGA architectures use longer routing lines that span
multiple logic blocks.
Whenever a vertical and a horizontal channel intersect, there is a switch box. In this
architecture, when a wire enters a switch box, there are three programmable switches
that allow it to connect to three other wires in adjacent channel segments. The pattern,
or topology, of switches used in this architecture is the planar or domain-based switch
box topology. In this switch box topology, a wire in track number one connects only
to wires in track number one in adjacent channel segments, wires in track number 2
connect only to other wires in track number 2 and so on. The figure below illustrates
the connections in a switch box.
Figure 2-1 Logic Block Pin Locations
SWITCH BOX TOPOLOGY

Modern FPGA families expand upon the above capabilities to include higher level
functionality fixed into the silicon. Having these common functions embedded into
the silicon reduces the area required and gives those functions increased speed
compared to building them from primitives. Examples of these include multipliers,
generic DSP blocks, embedded processors, high speed IO logic and embedded
memories.

FPGAs are also widely used for systems validation including pre-silicon validation,
post-silicon validation, and firmware development. This allows chip companies to
validate their design before the chip is produced in the factory, reducing the time-to-
market.
To shrink the size and power consumption of FPGAs, vendors such as Tabula and
Xilinx have introduced new 3D or stacked architecture. Following the introduction of
its 28 nm 7-series FPGAs, Xilinx revealed that that several of the highest-density
parts in those FPGA product lines will be constructed using multiple dice in one
package, employing technology developed for 3D construction and stacked-die
assemblies. The technology stacks several (three or four) active FPGA dice side-by-
side on a silicon interposer – a single piece of silicon that carries passive interconnect.
BASIC PROCESS TECHNOLOGY TYPES

 SRAM - based on static memory technology. In-system programmable and re-
programmable. Requires external boot devices. CMOS.
 Antifuse - One-time programmable. CMOS.
 PROM - Programmable Read-Only Memory technology. One-time programmable
because of plastic packaging.
 EPROM - Erasable Programmable Read-Only Memory technology. One-time
programmable but with window, can be erased with ultraviolet (UV) light. CMOS.
 EEPROM - Electrically Erasable Programmable Read-Only Memory technology.
Can be erased, even in plastic packages. Some but not all EEPROM devices can
be in-system programmed. CMOS.
 Flash - Flash-erase EPROM technology. Can be erased, even in plastic packages.
Some but not all flash devices can be in-system programmed. Usually, a flash cell
is smaller than an equivalent EEPROM cell and is therefore less expensive to
manufacture. CMOS.
 Fuse - One-time programmable. Bipolar.

2.17 FPGA ARCHITECTURE

Field Programmable Gate Array chips (FPGAs) are the most powerful and versatile
programmable logic devices. They combines the idea of programmability from the
earlier PLDs and the architecture of Uncommitted Gate Array which was one of the
ways to develop ASICs.
Figure 2-2 FPGA Architecture
The main elements of an FPGA chip are a matrix of programmable logic

blocks (these blocks are called differently, depending upon a vendor) and
a programmable routing matrix.
FPGA configuration memory is usually based on volatile SRAM (static memory), so

these FPGAs must be configured on every power-up from an external source, such as
a dedicated Flash chip. However, there are also both SRAM-based FPGAs with
intergrated flash module and pure Flash-based FPGAs that don't use SRAM at all.

Figure 2-3 Xilinx Spartan3
The Spartan-3 Starter Board provides a powerful, self-contained development

platform for designs targeting the new Spartan-3 FPGA from Xilinx. It features a
200K or 1000K gate Spartan-3, on-board I/O devices, and 1MB fast asyncronous
SRAM, making it the perfect platform to experiment with any new design, from a
simple logic circuit to an embedded processor core.
The board also contains a Platform Flash JTAG-programmable ROM, so designs can
easily be made non-volatile. The Spartan-3 Starter Board is fully compatible with all
versions of the Xilinx ISE tools, including the free WebPack. The board ships with a
power supply, and you can add a programming cable at checkout.\
Figure 2-4 Block Diagram of Xilinx Spartan3

The main elements of an FPGA chip are a matrix of programmable logic blocks (these
blocks are called differently, depending upon a vendor) and a programmable routing
matrix.
FPGA configuration memory is usually based on volatile SRAM (static memory), so

these FPGAs must be configured on every power-up from an external source, such as
a dedicated Flash chip. However, there are also both SRAM-based FPGAs with
intergrated flash module and pure Flash-based FPGAs that don't use SRAM at all.

Chapter # 3 Opto Coupler
CHAPTER THREE
OPTOCOUPLER
3.1 INTRODUCTION
A solid state component that uses a light-emitting diode to transmit light through an
optically transparent barrier between two isolated circuits. This barrier insulates
circuits by allowing light to pass through, but not current.
Contactors are useful in commercial and industrial applications, particularly for

controlling large lighting loads and motors. One of their hallmarks is reliability.
However, like any other device, they are not infallible. In most cases, the contactor
does not simply wear out from normal use. Usually, the reason for contactor failure is
misapplication. That's why you need to understand the basics of contactors.
When someone uses a lighting contactor in a motor application, that's a

misapplication. The same is true when someone uses a "normal operation" motor
contactor for motor jogging duty. Contactors have specific designs for specific
purposes.
When selecting contactors, you'll use one of two common standards: NEMA or IEC.
Both match a contactor with the job it has to do, but they do so in different ways
A contactor does not provide overload protection. Contactors are used to electrically
turn on or off high current, non-motor loads or in motor circuits where overload
protection is separately provided. The contactor operates by applying a control
voltage to the contactor coil. When the coil is energized, the movable contacts are
closed against the stationary contacts, thus completing the circuit. The contactor is
therefore used to supply and interrupt power to an electrical load.

3.2 DESCRIPTION
In electronics, an opto-isolator (or optical isolator, optocoupler, photocoupler, or
photoMOS) is a device that uses a short optical transmission path to transfer a signal
between elements of a circuit, typically a transmitter and a receiver, while keeping
them electrically isolated — since the signal goes from an electrical signal to an
optical signal back to an electrical signal, electrical contact along the path is broken.
Figure 3-1 Internal Diagram of Opto Coupler
A common implementation involves a LED and a phototransistor, separated so that

light may travel across a barrier but electrical current may not. When an electrical
signal is applied to the input of the opto-isolator, its LED lights, its light sensor then
activates, and a corresponding electrical signal is generated at the output. Unlike a
transformer, the opto-isolator allows for DC coupling and generally provides
significant protection from serious overvoltage conditions in one circuit affecting the
other.
With a photodiode as the detector, the output current is proportional to the amount of
incident light supplied by the emitter. The diode can be used in a photovoltaic mode
or a photoconductive mode.
In photovoltaic mode, the diode acts like a current source in parallel with a forward-
biased diode. The output current and voltage are dependent on the load impedance
and light intensity.

In photoconductive mode, the diode is connected to a supply voltage, and the

magnitude of the current conducted is directly proportional to the intensity of light.
An opto-isolator can also be constructed using a small incandescent lamp in place of

the LED; such a device, because the lamp has a much slower response time than an
LED, will filter out noise or half-wave power in the input signal. In so doing, it will
also filter out any audio- or higher-frequency signals in the input. It has the further
disadvantage, of course, (an overwhelming disadvantage in most applications) that
incandescent lamps have finite life spans. Thus, such an unconventional device is of
extremely limited usefulness, suitable only for applications such as science projects.
The optical path may be air or a dielectric waveguide. The transmitting and receiving
elements of an optical isolator may be contained within a single compact module, for
mounting, for example, on a circuit board; in this case, the module is often called an
optoisolator or opto-isolator. The photosensor may be a photocell, phototransistor, or
an optically triggered SCR or Triac. Occasionally, this device will in turn operate a
power relay or contactor
3.3 HISTORY
Photoresistor-based opto-isolators were introduced in the 1960s. They are the slowest,
but also the most linear isolators and still retain a niche market in audio and music
industry. Commercialization of LED technology in 1968–1970 caused a boom
in optoelectronics, and by the end of the 1970s the industry developed all principal
types of opto-isolators. The majority of opto-isolators on the market use bipolar
silicon phototransistor sensors. They attain medium data transfer speed, sufficient for
applications like electroencephalography. The fastest opto-isolators use PIN
diodes in photoconductive mode and contain electronic circuitry
for amplification, shaping and interfacing of the signal detected by the sensor, and can
attain data transfer rates of 50 MBd. Their role in computing and communications is
being challenged by new integrated isolation devices based on
microminiature transformers, capacitive or spin valves.

3.4 OPERATION
An opto-isolator contains a source (emitter) of light, almost always a near
infrared light-emitting diode (LED), that converts electrical input signal into light, a
closed optical channel (also called dielectrical channel[8]), and a photosensor, which
detects incoming light and either generates electric energy directly,
or modulates electric current flowing from an external power supply. The sensor can
be a photoresistor, a photodiode, a phototransistor, a silicon-controlled rectifier (SCR)
or a triac. Because LEDs can sense light in addition to emitting it, construction of
symmetrical, bidirectional opto-isolators is possible. An optocoupled solid state
relay contains a photodiode opto-isolator which drives a power switch, usually a
complementary pair of MOSFET transistors. A slotted optical switch contains a
source of light and a sensor, but its optical channel is open, allowing modulation of
light by external objects obstructing the path of light or reflecting light into the sensor.
3.5 ELECTRIC ISOLATION
Figure 3-2 Electric Isolation
Planar (top) and silicone dome (bottom) layouts - cross-section through a

standarddual in-line package. Relative sizes of LED (red) and sensor (green) are
exaggerated.
Electronic equipment and signal and power transmission lines can be subjected to
voltage surges induced by lightning, electrostatic discharge,radio frequency
transmissions, switching pulses (spikes) and perturbations in power supply. Remote

lightning strikes can induce surges up to 10 kV, one thousand times more than the
voltage limits of many electronic components. A circuit can also incorporate high
voltages by design, in which case it needs safe, reliable means of interfacing its high-
voltage components with low-voltage ones.
The main function of an opto-isolator is to block such high voltages and voltage
transients, so that a surge in one part of the system will not disrupt or destroy the other
parts. Or, according to the authors of The Art of Electronics, "in a nutshell, opto-
couplers let you send digital(and sometimes analog) signals between circuits with
separate grounds." Historically, this function was delegated to isolation transformers,
which use inductive coupling between galvanically isolated input and output sides.
Transformers and opto-isolators are the only two classes of electronic devices that
offer reinforced protection — they protect both the equipment and the human user
operating this equipment. They contain a single physical isolation barrier, but provide
protection equivalent to double isolation. Safety, testing and approval of opto-couplers
are regulated by national and international standards: IEC 60747-5-2, EN
(CENELEC) 60747-5-2, UL 1577, CSA Component Acceptance Notice. Opto-
isolator specifications published by manufacturers always follow at least one of these
regulatory frameworks.
An opto-isolator connects input and output sides with a beam of light modulated by
input current. It transforms useful input signal into light, sends it across
the dielectric channel, captures light on the output side and transforms it back into
electric signal. Unlike transformers, which pass energy in both directions with very
low losses, opto-isolators are unidirectional (see exceptions) and they cannot
transmit power. Typical opto-isolators can only modulate the flow of energy already
present on the output side. Unlike transformers, opto-isolators can passDC or slow-
moving signals and do not require matching impedances between input and output
sides. Both transformers and opto-isolators are effective in breaking ground loops,
common in industrial and stage equipment, caused by high or noisy return currents
in ground wires.
The physical layout of an opto-isolator depends primarily on the desired isolation

voltage. Devices rated for less than a few kV have planar (or sandwich)

construction. The sensor dieis mounted directly on the lead frame of its package
(usually, a six-pin or a four-pin dual in-line package). The sensor is covered with a
sheet of glass or clear plastic, which is topped with the LED die. The LED beam fires
downward. To minimize losses of light, the useful absorption spectrum of the sensor
must match the output spectrum of the LED, which almost invariably lies in the near
infrared. The optical channel is made as thin as possible for a desired breakdown
voltage. For example, to be rated for short-term voltages of 3.75 kV and transients of
1 kV/μs, the clear polyimide sheet in the Avago ASSR-300 series is only 0.08 mm
thick. Breakdown voltages of planar assemblies depend on the thickness of the
transparent sheet and the configuration of bonding wires that connect the dies with
external pins. Real in-circuit isolation voltage is further reduced by creepage over
the PCB and the surface of the package. Safe design rules require a minimal clearance
of 25 mm/kV for bare metal conductors or 8.3 mm/kV for coated conductors.
Opto-isolators rated for 2.5 to 6 kV employ a different layout called silicone

dome.http://en.wikipedia.org/wiki/Opto-isolator - cite_note-Basso-24 Here, the LED
and sensor dies are placed on the opposite sides of the package; the LED fires into the
sensor horizontally. The LED, the sensor and the gap between them are encapsulated
in a blob, or dome, of transparent silicone. The dome acts as a reflector, retaining all
stray light and reflecting it onto the surface of the sensor, minimizing losses in a
relatively long optical channel. In double mold designs the space between the silicone
blob ("inner mold") and the outer shell ("outer mold") is filled with dark dielectric
compound with a matched coefficient of thermal expansion.

3.6 TYPES OF OPTO-ISOLATORS

Current
Device
Source of light Sensor type Speed transfer
type
ratio
Incandescent light Very
Resistive
bulb low
opto- <100%[note
Neon lamp CdS or CdSe photoresistor (LDR) Low 6]
isolator
GaAs infrared LE
(Vactrol) Low
D
Diode
0.1% -
opto- GaAs infrared LED Silicon photodiode Highest
0.2%[23]
isolator
2% -
Transisto Bipolar silicon phototransistor Medium
120%[23]
r opto- GaAs infrared LED
100% -
isolator Darlington phototransistor Medium
600%[23]
Opto-
Low to
isolated GaAs infrared LED Silicon-controlled rectifier >100%
medium
SCR
Opto-
Low to
isolated GaAs infrared LED TRIAC Very high
medium
triac
Solid-
Stack of GaAs Stack of photodiodes driving Low to Practically
state
infrared LEDs a pair of MOSFETs or an IGBT high unlimited
relay
Table 3-1 TYPES OF OPTO-ISOLATORS
3.6.1 RESISTIVE OPTO-ISOLATORS

The earliest opto-isolators, originally marketed as light cells, emerged in the 1960s.
They employed miniature incandescent light bulbs as sources of light, and cadmium
sulfide (CdS) orcadmium selenide (CdSe) photo resistors (also called light-
dependent resistors, LDRs) as receivers. In applications where control linearity was
not important, or where available current was too low for driving an incandescent
bulb (as was the case in vacuum tube amplifiers), it was replaced with a neon lamp.

These devices (or just their LDR component) were commonly named Vactrols, after a
trademark of Vactec, Inc. The trademark has since been genericized. but the original
Vactrols are still being manufactured by PerkinElmer.
The turn-on and turn-off lag of an incandescent bulb lies in hundreds

of milliseconds range, which makes the bulb an effective low-pass
filter and rectifier but limits the practical modulation frequency range to a few Hertz.
With the introduction of light-emitting diodes (LEDs) in 1968–1970, the
manufacturers replaced incandescent and neon lamps with LEDs and achieved
response times of 5 milliseconds and modulation frequencies up to 250 Hz. The
name Vactrol was carried over on LED-based devices which are, as of 2010, still
produced in small quantities.
Photoresistors used in opto-isolators rely on bulk effects in a uniform film

of semiconductor; there are no p-n junctions. Uniquely among photo sensors, photo
resistors are non-polar devices suited for either AC or DC circuits. Their resistance
drops in reverse proportion to the intensity of incoming light, from virtually infinity to
a residual floor that may be as low as less than a hundred Ohms. These properties
made the original Vactrol a convenient and cheap automatic gain
control and compressor for telephone networks. The photo resistors easily withstood
voltages up to 400 Volts, which made them ideal for driving vacuum fluorescent
displays. Other industrial applications included photocopiers, industrial automation,
professional light measurement instruments and auto-exposure meters. Most of these
applications are now obsolete, but resistive opto-isolators retained a niche in audio, in
particular guitar amplifier, markets.
American guitar and organ manufacturers of the 1960s embraced the resistive opto-
isolator as a convenient and cheap tremolo modulator. Fender's early tremolo effects
used two vacuum tubes; after 1964 one of these tubes was replaced by an optocoupler
made of a LDR and a neon lamp. To date, Vactrols activated by pressing the stompbox
pedal are ubiquitous in the music industry. Shortages of genuine PerkinElmer Vactrols
forced the DIY guitar community to "roll their own" resistive opto-
isolators. Guitarists to date prefer opto-isolated effects because their
superior separation of audio and control grounds results in "inherently high quality of

the sound". However, the distortion introduced by a photoresistor at line levelsignal is

higher than that of a professional electrically-coupled voltage-controlled
amplifier. Performance is further compromised by slow fluctuations of resistance
owing to light history, a memory effect inherent in cadmium compounds. Such
fluctuations take hours to settle and can be only partially offset with feedback in the
control circuit.
3.6.2 PHOTODIODE OPTO-ISOLATORS
Figure 3-3 Photodiode Opto Isolators
A FAST PHOTODIODE OPTO-ISOLATOR WITH AN OUTPUT-

SIDE AMPLIFIER CIRCUIT.
Diode opto-isolators employ LEDs as sources of light and silicon photodiodes as
sensors. When the photodiode is reverse-biased with an external voltage source,
incoming light increases the reverse current flowing through the diode. The diode
itself does not generate energy; it modulates the flow of energy from an external
source. This mode of operation is called photoconductive mode. Alternatively, in the
absence of external bias the diode converts the energy of light into electric energy by
charging its terminals to a voltage of up to 0.7 V. The rate of charge is proportional to
the intensity of incoming light. The energy is harvested by draining the charge
through an external high-impedance path; the ratio of current transfer can reach
0.2%. This mode of operation is called photovoltaic mode.
The fastest opto-isolators employ PIN diodes in photoconductive mode. The response
times of PIN diodes lie in the subnanosecond range; overall system speed is limited
by delays in LED output and in biasing circuitry. To minimize these delays, fast
digital opto-isolators contain their own LED drivers and output amplifiers optimized
for speed. These devices are called full logic opto-isolators: their LEDs and sensors
are fully encapsulated within a digital logic circuit. The Hewlett-

Packard 6N137/HPCL2601 family of devices equipped with internal output amplifiers

was introduced in the late 1970s and attained 10 MBd data transfer speeds. It
remained an industry standard until the introduction of the 50 MBd Agilent
Technologies 7723/0723 family in 2002. The 7723/0723 series opto-isolators
contain CMOS LED drivers and a CMOS buffered amplifiers, which require two
independent external power supplies of 5 V each.
Photodiode opto-isolators can be used for interfacing analog signals, although

their non-linearity invariably distorts the signal. A special class of analog opto-
isolators introduced by Burr-Brown uses two photodiodes and an input-
side operational amplifier to compensate for diode non-linearity. One of two identical
diodes is wired into the feedback loop of the amplifier, which maintains overall
current transfer ratio at a constant level regardless of the non-linearity in the second
(output) diode.
Solid-state relays built around MOSFET switches usually employ a photodiode opto-
isolator to drive the switch. The gate of a MOSFET requires relatively small
total charge to turn on and its leakage current in steady state is very low. A photodiode
in photovoltaic mode can generate turn-on charge in a reasonably short time but its
output voltage is many times less than the MOSFET's threshold voltage. To reach the
required threshold, solid-state relays contain stacks of up to thirty photodiodes wired
in series.
3.6.3 PHOTO TRANSISTOR OPTO-ISOLATORS

Phototransistors are inherently slower than photodiodes. The earliest and the slowest
but still common 4N35 opto-isolator, for example, has rise and fall times of 5 μs into a
100 Ohm load and its bandwidth is limited at around 10 kiloHertz - sufficient for
applications like electroencephalography or pulse-width motor control Devices like
PC-900 or 6N138 recommended in the original 1983 Musical Instrument Digital
Interface specification allow digital data transfer speeds of tens of
kiloBauds. Phototransistors must be properly biasedand loaded to achieve their
maximum speeds, for example, the 4N28 operates at up to 50 kHz with optimum bias
and less than 4 kHz without it.

Design with transistor opto-isolators requires generous allowances for wide

fluctuations of parameters found in commercially available devices. Such fluctuations
may be destructive, for example, when an opto-isolator in the feedback loop of a DC-
to-DC converter changes its transfer function and causes spurious oscillations,[21] or
when unexpected delays in opto-isolators cause a short circuit through one side of
an H-bridge.[45] Manufacturers' datasheets typically list only worst-case values for
critical parameters; actual devices surpass these worst-case estimates in an
unpredictable fashion. Bob Pease observed that current transfer ratio in a batch of
4N28's can vary from 15% to more than 100%; the datasheet specified only a
minimum of 10%. Transistor beta in the same batch can vary from 300 to 3000,
resulting in 10:1 variance in bandwidth.
Opto-isolators using field-effect transistors (FETs) as sensors are rare and, like
vactrols, can be used as remote-controlled analog potentiometers provided that the
voltage across the FET's output terminal does not exceed a few hundred mV. Opto-
FETs turn on without injecting switching charge in the output circuit, which is
particularly useful in sample and holdcircuits.
3.6.4 BIDIRECTIONAL OPTO-ISOLATORS

All opto-isolators described so far are uni-directional. Optical channel always works
one way, from the source (LED) to the sensor. The sensors, be it photoresistors,
photodiodes or phototransistors, cannot emit light. But LEDs, like all semiconductor
diodes,are capable of detecting incoming light, which makes possible construction of
a two-way opto-isolator from a pair of LEDs. The simplest bidirectional opto-isolator
is merely a pair of LEDs placed face to face and held together with heat-shrink tubing.
If necessary, the gap between two LEDs can be extended with a glass fiber insert.
Visible spectrum LEDs have relatively poor transfer efficiency, thus near infrared
spectrum GaAs, Si and AlGaAs Si LEDs are the preferred choice for bidirectional
devices. Bidirectional opto-isolators built around pairs of GaAs:Si LEDs have current
transfer ratio of around 0.06% in either photovoltaic or photoconductive mode — less
than photodiode-based isolators, but sufficiently practical for real-world applications.

3.7 OPTO COUPLERS

The Optocoupler is a device that consists of a LED (light-emitting diode) and
a phototransistor. When the LED emits light, it illuminates the phototransistor
causing a current to flow through it.
These two elements are coupled in the most efficient possible way. The Ic output
current of the optocoupler (phototransistor`s collector current) is proportional to
the input current IF (LED`s current). The relation between these two currents is
called Current Transfer Rate (CTR), and depends on the enviromental
temperature.
The most common industrial use of the optocouplers (or optically-coupled isolators)
is as a signal converter between high-voltage pitot devices (limit switches etc.) and
low voltage solid-state logic circuits. Optical isolators can be employed in any
situation where a signal must be passed between two circuits which are isolated from
each other. Complete electrical isolation between two circuits (i.e. the two circuits
have no conductors in com mon) is often necessary to prevent noise generated in one
circuit from being passed to the other circuit. This is especially necessary for the
coupling between high-voltage informa tion-gathering circuits and low-voltage digital
logic circuits. The information circuits are almost badly exposed to noise sources and
the logic circuits cannot tolerate noise signals.
3.7.1 4N35
Figure 3-4 4N35
3.7.2 DESCRIPTION

 The 4N35 is an optocoupler for general purpose applications. It contains a light

emitting diode optically coupled to a phototransistor. It is packaged in a 6-pin
DIP package and available in wide- lead spacing option and lead bend SMD
option. Response time, tr, is
 typically 3 µs and minimum CTR is 100% at input current of 10 mA.
3.6.3 FEATURES
 High Current Transfer Ratio (CTR: min. 100% at IF = 10 mA, VCE = 10 V)
 Response time (tr: typ., 3 µs at
 VCE = 10 V, IC = 2 mA, RL = 100 Ω)
 Input-output isolation voltage (Viso = 3550 Vrms)
 Dual-in-line package UL approved
 CSA approved
 IEC/EN/DIN EN 60747-5-2 approved
 4N35-XXXE
 Lead Free Option Number
 Options available:
– Leads with 0.4" (10.16 mm) spacing (W00)
– Leads bends for surface mounting (300)
– Tape and reel for SMD (500) – IEC/EN/DIN EN 60747-5-2
 approvals (060)
 = No Options
 060 = IEC/EN/DIN EN 60747-5-2 Option
 W00 = 0.4" Lead Spacing Option 300 = Lead Bend SMD Option 500 = Tape and
Reel Packaging
 Option

3.6.4 APPLICATIONS
 I/O interfaces for computers System appliances, measuring instruments
 Signal transmission between circuits of different potentials and impedances

Chapter # 4 Contactor
CHAPTER FOUR
CONTACTOR
4.1 INTRODUCTION
A contactor is an electrically controlled switch used for switching a power circuit,
similar to a relay except with higher current ratings. A contactor is controlled by a
circuit which has a much lower power level than the switched circuit.
Contactors come in many forms with varying capacities and features. Unlike a circuit
breaker, a contactor is not intended to interrupt a short circuit current. Contactors
range from those having a breaking current of several amperes and 24 V DC to
thousands of amperes and many kilovolts. The physical size of contactors ranges from
a device small enough to pick up with one hand, to large devices approximately a
meter (yard) on a side.
Contactors are used to control electric motors, lighting, heating, capacitor banks, and
other electrical loads.
A contactor has three components. The contacts are the current carrying part of the
contactor. This includes power contacts, auxiliary contacts, and contact springs. The
electromagnet provides the driving force to close the contacts. The enclosure is a
frame housing the contact and the electromagnet. Enclosures are made of insulating
materials like Bakelite, Nylon 6, and thermosetting plastics to protect and insulate the
contacts and to provide some measure of protection against personnel touching the
contacts. Open-frame contactors may have a further enclosure to protect against dust,
oil, explosion hazards and weather.
Magnetic blowouts use blowout coils to lengthen and move the electric arc. These are
especially useful in DC power circuits. AC arcs have periods of low current, during
which the arc can be extinguished with relative ease, but DC arcs have continuous
high current, so blowing them out requires the arc to be stretched further than an AC
arc of the same current. The magnetic blowouts in the pictured Albright contactor

(which is designed for DC currents) more than double the current it can break,
increasing it from 600 A to 1,500 A.
Sometimes an economizer circuit is also installed to reduce the power required to
keep a contactor closed; an auxiliary contact reduces coil current after the contactor
closes. A somewhat greater amount of power is required to initially close a contactor
than is required to keep it closed. Such a circuit can save a substantial amount of
power and allow the energized coil to stay cooler. Economizer circuits are nearly
always applied on direct-current contactor coils and on large alternating current
contactor coils.
A basic contactor will have a coil input (which may be driven by either an AC or DC
supply depending on the contactor design). The coil may be energized at the same
voltage as the motor, or may be separately controlled with a lower coil voltage better
suited to control by programmable controllers and lower-voltage pilot devices.
Certain contactors have series coils connected in the motor circuit; these are used, for
example, for automatic acceleration control, where the next stage of resistance is not
cut out until the motor current has dropped.
4.2 INDUSTRY CLASSIFICATIONS

Electrical contractors are generally classified by three major types of work performed.
 "Outside" or "line" contractors are responsible for high-voltage power
transmission and distribution lines. Line contractors build and maintain the
infrastructure required to transport electricity generated at a power plant through a
series of high-voltage lines and substations before it is used to power facilities,
buildings, and homes.
 "Inside" electrical contractors provide electricity to any structure within a
property’s boundary lines, including outdoor lighting or substations. Under current
construction specification guidelines, "inside" electrical contractors can serve as
prime contractors for all electrical and cabling design, installation, and
maintenance for commercial, institutional, and residential buildings.
 "Integrated building systems" (IBS) or "Voice/Data/Video" (VDV) electrical
contractors work primarily with low-voltage installations such as back-up power,
climate controls, wireless networks, energy-efficient

lighting, telecommunications, fiber optics, and security systems. IBS contractors

are particularly skilled at integrating these system controls to work together for
maximum energy efficiency and building performance.
When a relay is used to switch a large amount of electrical power through its contacts,
it is designated by a special name: contactor. Contactors typically have multiple
contacts, and those contacts are usually (but not always) normally-open, so that power
to the load is shut off when the coil is de-energized. Perhaps the most common
industrial use for contactors is the control of electric motors.
Figure 4-1 Contactor
The top three contacts switch the respective phases of the incoming 3-phase AC
power, typically at least 480 Volts for motors 1 horsepower or greater. The lowest
contact is an "auxiliary" contact which has a current rating much lower than that of
the large motor power contacts, but is actuated by the same armature as the power
contacts. The auxiliary contact is often used in a relay logic circuit, or for some other
part of the motor control scheme, typically switching 120 Volt AC power instead of
the motor voltage. One contactor may have several auxiliary contacts, either
normally-open or normally-closed.
4.3 FEATURES OF CONTACTORS

 A contactor is a relay that is used for switching power for high voltages.
 They usually handle very heavy loads like an electric motor, lighting and heating
equipments and so on.

 Though their output is used for switching very high loads, they are controlled by a
circuit with very less power.
 According to the loads they handle, they vary in sizes from a small device to as
huge as a yard.
 Though they are used for switching purposes, they do not interrupt a short-circuit
current like a circuit breaker.
 They have ratings ranging from a breaking current of a few amperes and 24 DC
volts to thousands of amperes with many kilo volts.
4.4 CONTACTOR – DESIGN AND CONSTRUCTION

Like a relay, a contactor also has
 Contact
 Spring
 Electromagnet
The contact part of the contactor includes the power contacts as well as the auxiliary
contacts. The power contacts gains the power for the contactor and the auxiliary
contacts is used to bring a loop with the rest of the rest of the devices it is attached to.
These contacts are connected to the contact springs.
The contacts are controlled by the electromagnet. These electromagnets give the
initial force to the contacts and make them closed. Both these contacts and
electromagnet are enclosed in a frame which is usually made of insulating materials.
The usually used insulating materials are Nylon 6, thermosetting plastics and so on.
They are useful, as they completely insulate the contacts and help in preventing the
touch of contacts. For high-end contactors, an open-frame contactor is commonly
used. This will provide a greater protection from oil, dust, weather and also from
explosion. The type of frame housing used may also differ according to the voltage
rating used. The ones given above are restricted up to a certain voltage. If the
contactors are used to manage volts higher than 1000 volts, inert gases and also
vacuum is used as frame housing.
Contactors are also used in DC circuits. For their use in DC circuits, magnetic
blowouts are also used. The use of blowout coils help in stretching and moving the

electric arc. The electric arcs can be AC or DC. An AC arc will have can be easily
extinguished as they have low current characteristics. DC arcs of the same current
characteristics need more stretching need more current to be blown out. They ratings
differ from about 500 Amperes to about 1500 Amperes.
In order to save power in a contactor when it is closed, an economizer circuit is also

introduced. This circuit helps in reducing the coil current. There is difference in the
amount of power that is required to close the contactor and that from keeping it
closed. Greater power is required to close it. This circuit will also help it to stay
cooler. Take a look at the diagram given below.
4.5 WORKING OF CONTACTOR

As contactors are used for high-current load applications they are designed to control
and reduce the arc produced when the heavy motor currents are interrupted. Other
than the low current contacts, they are also setup with Normally Open contacts.
These are devices which handle more than 20 Amperes current and over 100 Kilo
Watts power.
The contactor has an AC/DC supply driven coil input. This will depend on the
requirement. This coil will mostly be controlled by a lower voltage PLC. They can
also be controlled by the motor voltage. The motor may have series of coils connected
to either control the acceleration or even the resistance.
When current is passed through the contactor, the electromagnet starts to build up,
producing a magnetic field. Thus the core of the contactor starts to wind up. This
process helps in energizing the moving contact. Thus the moving and fixed contacts
make a short circuit. Thus the current is passed through them to the next circuit. The
armature coil brings in high current in the initial position. This reduces as soon as the
metal core enters the coil. When the current is stopped, the coil gets de-energized and
thus the contacts get open circuited.
Unlike general-purpose relays, contactors are designed to be directly connected to

high-current load devices. Relays tend to be of lower capacity and are usually

designed for both normally closed and normally open applications. Devices switching
more than 15 amperes or in circuits rated more than a few kilowatts are usually called
contactors. Apart from optional auxiliary low current contacts, contactors are almost
exclusively fitted with normally open contacts. Unlike relays, contactors are designed
with features to control and suppress the arc produced when interrupting heavy motor
currents.
When current passes through the electromagnet, a magnetic field is produced, which
attracts the moving core of the contactor. The electromagnet coil draws more current
initially, until its inductance increases when the metal core enters the coil. The moving
contact is propelled by the moving core; the force developed by the electromagnet
holds the moving and fixed contacts together. When the contactor coil is de-energized,
gravity or a spring returns the electromagnet core to its initial position and opens the
contacts.
For contactors energized with alternating current, a small part of the core is
surrounded with a shading coil, which slightly delays the magnetic flux in the core.
The effect is to average out the alternating pull of the magnetic field and so prevent
the core from buzzing at twice line frequency.
Most motor control contactors at low voltages (600 volts and less) are air break
contactors; air at atmospheric pressure surrounds the contacts and extinguishes the arc
when interrupting the circuit. Modern medium-voltage motor controllers use vacuum
contactors. High voltage contactors (greater than 1000 volts) may use vacuum or an
inert gas around the contacts. High-voltage electric locomotives may be isolated from
their overhead supply by roof-mounted circuit breakers actuated by compressed air;
the same air supply may be used to "blow out" any arc that forms.
4.6 COMPONENT DESCRIPTION
4.6.1 AC CONTACTOR LC1-D09 DESCRIPTION

LC1 Series AC contactors (simplified AC contactor in the following)are suitable for
using 50Hz or 60Hz rated rated voltage up to 660V rated current up to 95A. It is

maining used for making/breaking electric circuits at a long distance and for frequent
starting/stopping and control AC motors. Combined with the auxiliary contact group,
air delayer, machine inter locking device etc. It is combined into the delay contactor.
Into thedelay contactor. Mechanicat inter locking contactor star-triangle starter with
the thermal relay. It iscombinde into the tle electromagnetic starter mechanical.
Figure 4-2 LC1D09
4.6.2 CONTACTOR RATINGS

Contactors are rated by designed load current per contact (pole), maximum fault
withstand current, duty cycle, voltage, and coil voltage. A general purpose motor
control contactor may be suitable for heavy starting duty on large motors; so-called
"definite purpose" contactors are carefully adapted to such applications as air-
conditioning compressor motor starting. North American and European ratings for
contactors follow different philosophies, with North American general purpose
machine tool contactors generally emphasizing simplicity of application while
definite purpose and European rating philosophy emphasizes design for the intended
life cycle of the application.
Ratings of a contactor are given according to the pole of the contactor. It also depends
on factors like fault withstand current, coil voltage and so on. According to their
rating, contactors are classified into the following.
AC1 – Non-inductive rows
AC2 – Contactors for starting of slip-ring motors

AC3 – Starting of squirrel-cage motors and switching off only after the motor is up to
speed.
AC4 – Starting of squirrel-cage motors with inching and plugging duty.
AC11 – Auxiliary control circuits
4.6.3 CONTACTOR APPLICATIONS

 Lighting control
 Magnetic starter
LIGHTING CONTROL
Contactors are often used to provide central control of large lighting installations,
such as an office building or retail building. To reduce power consumption in the
contactor coils, latching contactors are used, which have two operating coils. One
coil, momentarily energized, closes the power circuit contacts, which are then
mechanically held closed; the second coil opens the contacts.
MAGNETIC STARTER
A magnetic starter is a device designed to provide power to electric motors. It
includes a contactor as an essential component, while also providing power-cutoff,
under-voltage, and overload protection

Chapter # 5 Relay
CHAPTER FIVE
RELAY
5.1 INTRODUCTION
We know that most of the high end industrial application devices have relays for their
effective working. Relays are simple switches which are operated both electrically
and mechanically. Relays consist of a n electromagnet and also a set of contacts. The
switching mechanism is carried out with the help of the electromagnet. There are also
other operating principles for its working. But they differ according to their
applications. Most of the devices have the application of relays.
The main operation of a relay comes in places where only a low-power signal can be
used to control a circuit. It is also used in places where only one signal can be used to
control a lot of circuits. The application of relays started during the invention of
telephones. They played an important role in switching calls in telephone exchanges.
They were also used in long distance telegraphy. They were used to switch the signal
coming from one source to another destination. After the invention of computers they
were also used to perform Boolean and other logical operations. The high end
applications of relays require high power to be driven by electric motors and so on.
Such relays are called contactors.
5.2 RELAY CONSTRUCTION

It is an electro-magnetic relay with a wire coil, surrounded by an iron core. A path of
very low reluctance for the magnetic flux is provided for the movable armature and
also the switch point contacts. The movable armature is connected to the yoke which
is mechanically connected to the switch point contacts. These parts are safely held
with the help of a spring. The spring is used so as to produce an air gap in the circuit
when the relay becomes de-energized.
The working of a relay can be better understood by explaining the following diagram
given below.

Chapter # 5 Relay
Figure 5-1 Relay Construction
5.3 RELAY DESIGN

The diagram shows an inner section diagram of a relay. An iron core is surrounded by
a control coil. As shown, the power source is given to the electromagnet through a
control switch and through contacts to the load. When current starts flowing through
the control coil, the electromagnet starts energizing and thus intensifies the magnetic
field. Thus the upper contact arm starts to be attracted to the lower fixed arm and thus
closes the contacts causing a short circuit for the power to the load. On the other hand,
if the relay was already de-energized when the contacts were closed, then the contact
move oppositely and make an open circuit.
As soon as the coil current is off, the movable armature will be returned by a force
back to its initial position. This force will be almost equal to half the strength of the
magnetic force. This force is mainly provided by two factors. They are the spring and
also gravity.
Relays are mainly made for two basic operations. One is low voltage application and
the other is high voltage. For low voltage applications, more preference will be given
to reduce the noise of the whole circuit. For high voltage applications, they are mainly
designed to reduce a phenomenon called arcing.

Chapter # 5 Relay
There are only four main parts in a relay. They are

 Electromagnet
 Movable Armature
 Switch point contacts
 Spring
The figures given below show the actual design of a simple relay.
5.4 RELAY BASICS

The basics for all the relays are the same. Take a look at a 4 – pin relay shown below.
There are two colours shown. The green colour represents the control circuit and the
red colour represents the load circuit. A small control coil is connected onto the
control circuit. A switch is connected to the load. This switch is controlled by the coil
in the control circuit. Now let us take the different steps that occour in a relay.
5.4.1 WHY IS A RELAY USED?

The main operation of a relay comes in places where only a low-power signal can be
used to control a circuit. It is also used in places where only one signal can be used to
control a lot of circuits. The application of relays started during the invention of
telephones. They played an important role in switching calls in telephone exchanges.
They were also used in long distance telegraphy. They were used to switch the signal
coming from one source to another destination. After the invention of computers they
were also used to perform Boolean and other logical operations. The high end
applications of relays require high power to be driven by electric motors and so on.
Such relays are called contactors.

Chapter # 5 Relay
Figure 5-2 Relay Operation
5.4.2 ENERGIZED RELAY (ON)

As shown in the circuit, the current flowing through the coils represented by pins 1
and 3 causes a magnetic field to be aroused. This magnetic field causes the closing of
the pins 2 and 4. Thus the switch plays an important role in the relay working. As it is
a part of the load circuit, it is used to control an electrical circuit that is connected to
it. Thus, when the relay in energized the current flow will be through the pins 2 and 4.
Figure 5-3 Energized Relay (ON)

Chapter # 5 Relay
5.4.3 DE – ENERGIZED RELAY (OFF)

As soon as the current flow stops through pins 1 and 3, the switch opens and thus the
open circuit prevents the current flow through pins 2 and 4. Thus the relay becomes
de-energized and thus in off position.
Figure 5-4 De-Energized Relay (OFF)
In simple, when a voltage is applied to pin 1, the electromagnet activates, causing a

magnetic field to be developed, which goes on to close the pins 2 and 4 causing a
closed circuit. When there is no voltage on pin 1, there will be no electromagnetic
force and thus no magnetic field. Thus the switches remain open.
POLE AND THROW

Relays have the exact working of a switch. So, the same concept is also applied. A
relay is said to switch one or more poles. Each pole has contacts that can be thrown in
mainly three ways. They are
Normally Open Contact (NO) – NO contact is also called a make contact. It closes
the circuit when the relay is activated. It disconnects the circuit when the relay is
inactive.

Chapter # 5 Relay
Normally Closed Contact (NC) – NC contact is also known as break contact. This is
opposite to the NO contact. When the relay is activated, the circuit disconnects. When
the relay is deactivated, the circuit connects.
Change-over (CO) / Double-throw (DT) Contacts – This type of contacts are used
to control two types of circuits. They are used to control a NO contact and also a NC
contact with a common terminal. According to their type they are called by the
names break before make and make before break contacts.
Relays are also named with designations like

Single Pole Single Throw (SPST) – This type of relay has a total of four terminals.
Out of these two terminals can be connected or disconnected. The other two terminals
are needed for the coil.
Single Pole Double Throw (SPDT) – This type of a relay has a total of five
terminals. Out f these two are the coil terminals. A common terminal is also included
which connects to either of two others.
Double Pole Single Throw (DPST) – This relay has a total of six terminals. These
terminals are further divided into two pairs. Thus they can act as two SPST’s which
are actuated by a single coil. Out of the six terminals two of them are coil terminals.
Double Pole Double Throw (DPDT) – This is the biggest of all. It has mainly eight
relay terminals. Out of these two rows are designed to be change over terminals. They
are designed to act as two SPDT relays which are actuated by a single coil.
5.5 TYPES OF RELAYS

Here is a detailed list of the different types of relays.
1. Latching Relay
Latching relays are also called impulse relays. They work in the bistable mode, and
thus have two relaxing states. They are also called keep relays or stay relays because
as soon as the current towards this relay is switched off, the relay continues the

Chapter # 5 Relay
process that it was doing in the last state. This can be achieved only with a solenoid
which is operating in a ratchet and cam mechanism. It can also be done by an over-
centre spring mechanism or a permanent magnet mechanism in which, when the coil
is kept in the relaxed point, the over-centre spring holds the armature and the contacts
in the right spot. This can also be done with the help of a remanent core.
In the ratchet and cam method, power consumption occurs only for a particular time.
Hence it is more advantageous than the others.
2. Reed Relay
These types of relays have been given more importance in the contacts. In order to
protect them from atmospheric protection they are safely kept inside a vacuum or
inert gas. Though these types of relays have a very low switching current and voltage
ratings, they are famous for their switching speeds.
3. Polarized Relay
This type of relay has been given more importance on its sensitivity. These relays
have been used since the invention of telephones. They played very important roles in
early telephone exchanges and also in detecting telegraphic distortion. The sensitivity
of these relays are very easy to adjust as the armature of the relay is placed between
the poles of a permanent magnet.
4. Buchholz Relay
This relay is actually used as a safety device. They are used for knowing the amount
of gas present in large oil-filled transformers. They are designed in such a way that
they produce a warning if it senses either the slow production of gas or fast
production of gas in the transformer oil.
5. Overload protection Relay

As the name implies, these relays are used to prevent the electric motors from damage
by over current and short circuits. For this the heating element is kept in series with
the motor. Thus when over heat occurs the bi-metallic strip connected to the motor
heats up and in turn releases a spring to operate the contacts of the relay.

Chapter # 5 Relay
6. Mercury Wetted Relay

This relay is almost similar to the reed relay explained earlier. The only difference is
that instead of inert gases, the contacts are wetted with mercury. This makes them
more position sensitive and also expensive. They have to be vertically mounted for
any operation. They have very low contact resistance and so can be used for timing
applications. Due to these factors, this relay is not used frequently.
7. Machine Tool Relay

This is one of the most famous industrial relay. They are mainly used for the
controlling of all kinds of machines. They have a number of contacts with easily
replaceable coils. This enables them to be easily converted from NO contact to NC
contact. Many types of these relays can easily be setup in a control panel. Though
they are very useful in industrial applications, the invention of PLC has made them
farther away from industries.
8. Contactor Relay
This is one of the most heavy load relay ever used. They are mainly used in switching
electric motors. They have a wide range of current ratings from a few amps to
hundreds. The contacts of these relays are usually made with alloys containing a small
percentage of silver. This is done so as to avoid the hazardous effects of arcing. These
type of relays are mainly categorized in the rough use areas. So, they produce loud
noises while operated and hence cannot be used in places where noise is a problem.
9. Solid State relay

SSR relays, as its name implies are designed with the help of solid state components.
As they do not have any moving objects in their design they are known for their high
reliability.
10. Solid State Contactor Relay

These relays combine both the features of solid state relays and contactor relays. As a
result they have a number of advantages. They have a very good heat sink and can be
designed for the correct on-off cycles. They are mainly controlled with the help of
PLC, micro-processors or microcontrollers.

Chapter # 5 Relay
5.6 RELAY MY4N
Figure 5-5 Relay MY4N

 An Improved Miniature Power Relay with Many Models for Sequence Control
and Power Applications
 A wide range of relay variations including ones with operation indicators, high-
capacity capability,
 built-in diodes, etc.
 Arc barrier standard on 3- and 4-pole relays.
 Withstand voltage: 2,000 VAC.
5.6.1 RELAY SELECTION

 Protection – Different protections like contact protection and coil protection must
be noted. Contact protection helps in reducing arcing in circuits using inductors.
Coil protection helps in reducing surge voltage produced during switching.
 Look for a standard relay with all regulatory approvals.
 Switching time – Ask for high speed switching relays if you want one.
 Ratings – There are current as well as voltage ratings. The current ratings vary
from a few amperes to about 3000 amperes. In case of voltage ratings, they vary
from 300 Volt AC to 600 Volt AC. There are also high voltage relays of about
15,000 Volts.
 Type of contact used – Whether it is a NC or NO or closed contact.
 Select Make before Break or Break before Make contacts wisely.
 Isolation between coil circuit and contacts

Chapter # 5 Relay
5.7 APPLICATIONS
Selection of an appropriate relay for a particular application requires evaluation of
many different factors:
 Number and type of contacts – normally open, normally closed, (double-throw)
 Contact sequence – "Make before Break" or "Break before Make". For
example, the old style telephone exchanges required Make-before-break so that
the connection didn't get dropped while dialing the number.
 Rating of contacts – small relays switch a few amperes, large contactors are
rated for up to 3000 amperes, alternating or direct current
 Voltage rating of contacts – typical control relays rated 300 VAC or 600 VAC,
automotive types to 50 VDC, special high-voltage relays to about 15 000 V
 Operating lifetime, useful life - the number of times the relay can be expected
to operate reliably. There is both a mechanical life and a contact life; the
contact life is naturally affected by the kind of load being switched.
 Coil voltage – machine-tool relays usually 24 VAC, 120 or 250 VAC, relays for
switchgear may have 125 V or 250 VDC coils, "sensitive" relays operate on a
few milliamperes
 Coil current - including minimum current required to operate reliably and
minimum current to hold. Also effects of power dissipation on coil temperature
at various duty cycles.
 Package/enclosure – open, touch-safe, double-voltage for isolation between
circuits, explosion proof, outdoor, oil and splash resistant, washable for printed
circuit board assembly
 Operating environment - minimum and maximum operating temperatures and
other environmental considerations such as effects of humidity and salt
 Assembly – Some relays feature a sticker that keeps the enclosure sealed to
allow PCB post soldering cleaning, which is removed once assembly is
complete.
 Mounting – sockets, plug board, rail mount, panel mount, through-panel
mount, enclosure for mounting on walls or equipment
 Switching time – where high speed is required
 "Dry" contacts – when switching very low level signals, special contact
materials may be needed such as gold-plated contacts

Chapter # 5 Relay
 Contact protection – suppress arcing in very inductive circuits

 Coil protection – suppress the surge voltage produced when switching the coil
current
 Isolation between coil circuit and contacts
 Aerospace or radiation-resistant testing, special quality assurance
 Expected mechanical loads due to acceleration – some relays used
in aerospace applications are designed to function in shock loads of 50 g or
more
 Accessories such as timers, auxiliary contacts, pilot lamps, test buttons
 Regulatory approvals
 Stray magnetic linkage between coils of adjacent relays on a printed circuit
board.

Chapter # 6 AMF (Auto Manufacture)
CHAPTER SIX
A.M.F. (AUTO MAN FAILURE)
6.1 INTRODUCTION
An Automatic Mains Failure module with generator monitoring, protection and start
facilities. It utilizes advanced surface mount construction techniques to provide a
compact yet highly specified module. Operation of the module is via three
pushbuttons mounted on the front panel with STOP, MANUAL and AUTO positions.
Selection of the ‘Auto’ mode is confirmed by LED indicator, and monitors the
incoming mains supply (3 phase or single phase). Should the incoming AC mains
supply fall below a configurable pre-set limit (180V default), the generator will be
started, and load transferred to the gen-set.
When the AC mains supply returns to within limits, the module will wait for a
configurable, pre-set stabilization period, and then transfer load back to the mains.
The engine will be instructed to stop after a cool-down period. The module’s
microprocessor provides a comprehensive list of timers and functions, and access to
the settings is via a small Configuration Switch on the rear of the module. Parameter
settings can be adjusted using the front panel pushbuttons once in Configuration
Mode. The module monitors the engine and provides the following functions:
 Automatic Start with 3 start attempts
 Automatic Crank Disconnect -with adjustable Start and Stop Timers and Fail to
Start indication.
 Configurable Pre-heat and Energized Stop functions.
 Low Oil Pressure and High Engine Temperature Shutdown.
 Overspeed and Underspeed (frequency) protection.
 Charge Fail alarm
 Two fully configurable auxiliary inputs.
 Adjustable Warming and cooling timers
 Adjustable Mains Fail voltage level
 Change-over contactor control.

All alarms are indicated by high visibility red LED’s.

Issues such as environmental compliance and EMC have been carefully engineered
into the design. Advanced features such as Protected Solid State Outputs mean that
there are no moving parts or contacts to burn out.
6.2 0PERATION
Stop mode - This is used to stop the engine when it is running and to cancel ‘Auto’
mode. It is also used to reset any Shutdown alarm conditions.
Manual mode - This is used to manually start and run the engine. It can be stopped by
pressing the Stop button.Auto mode - This selects the automatic mode of operation, in
which the module will await a mains failure. Once detected, the module will initiate
its pre-configured start sequence, observing the Start Delay Timer before starting the
engine. When the mains supply returns, the module will initiate its pre-configured
stopping sequence.
6.3 FEATURES
 Micro-processor based design
 Automatic Engine Starting and
 Stopping
 Automatic Shutdown on Fault
 Condition
 Configurable via front panel
 Simple pushbutton controlled operation
 Configurable Digital Inputs
 Configurable Solid State Outputs
 Configurable Timer Settings
 Solid State Fuel and Crank Outputs
 External Remote Start Input
 LED Alarm indication
 Start/Stop Delay Timer
 Warm-up/Cooling Timer

 Energise to Stop Timer

 Single/Three phase mains sensing
 Load contactor control Solid State
 Outputs
 Pre-heat Timer
 Over Speed Shutdown
 Optional Underspeed Protection
 Low Oil Pressure Shutdown
 High Engine Temp Shutdown
 Optional Crank Disconnect from Oil
 Pressure
6.4 DESCRIPTION
6.4.1 DC SUPPLY
8 to 35 V Continuous.
6.4.2 CRANKING DROPOUTS

Able to survive 0 V for 50 mS, providing supply was at least 10 V before dropout and
supply recovers to 5V. This is achieved without the need for internal batteries.
6.4.3 MAX. CURRENT

 Operating 50mA
 Standby 10mA
 Alternator Input Range:
 75(ph-N) to 277(ph-N) 3 Phase
 4wire AC (+20%)
6.4.4 ALTERNATOR INPUT FREQUENCY

50 - 60 Hz at rated engine speed
(Minimum: 75V AC Ph-N) (Crank
Disconnect from 15V Ph-N @ 20Hz)

Overspeed +14% (+24% overshoot)

Underspeed –20%
6.4.5 START OUTPUT

1.2 Amp DC at supply voltage.
Fuel Output:
Auxiliary Outputs:
6.4.6 DIMENSIONS
125 X 165 X 28 mm
6.4.7 CHARGE FAIL

12V = 8V CF 24V = 16V CF
6.4.8 OPERATING TEMPERATURE RANGE:

Low Voltage Directive
Compliant with BS EN 50081-2
EMC Directive
Compliant with BS EN 50082-2 AND EMC Directly

Chapter # 7 MOR Manual Over Riding
CHAPTER SEVEN
MOR MANUAL OVER RIDING
7.1 BACKGROUND
A manual override is a mechanism wherein control is taken from an automated
system and given to the user. A manual override in photography refers to the ability
for the human photographer to turn off the automatic aperture sizing, automatic
focusing, or any other automated system on the camera.
Some manual overrides can be used to veto an automated system's judgment when the
system is in error. An example of this is a printer's ink level detection: in one case, a
researcher found that when he overrode the system, up to 38% more pages could be
printed at good quality by the printer than the automated system would have allowed
Automated systems are becoming increasingly common and integrated into everyday
objects such as automobiles and domestic appliances. This development of computing
raises general issues of policy and law about the need for manual overrides for matters
of great importance such as life-threatening situations and major economic decisions.
The loyalty of such autonomous devices then becomes an issue. If they follow rules
installed by the manufacturer or required by law and refuse to cede control in some
situations then the owners of the devices may feel disempowered, alienated and
lacking true ownership.

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TABLE OF CONTENTS

Chapter # 2 FPGA (FIELD PROGRAMMABLE GATE ARRAY) 8

Chapter # 6 A.M.F. (AUTO MAN FAILURE) 60

Chapter # 7 MOR MANUAL OVER RIDING 64

Figure 2-1 Logic Block Pin Locations 22

Table 3-1 Types Of Opto-Isolators 34

Sir Syed University of Engineering & Technology 1

1.3 INTRODUCTION TO POWER SYSTEMS

1.4 POWER SYSTEM ALTERNATIVES

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1.5 UNDERSTANDING YOUR POWER NEEDS

Device Typical wattage Surge wattage

Sir Syed University of Engineering & Technology 3

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1.6.1 OPEN TRANSITION

1.6.2 CLOSED TRANSITION

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Closed transition transfer makes code-mandated monthly testing less objectionable

1.7 SOFT LOADING

1.7.1 STATIC TRANSFER SWITCH

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1.9 HOME USE

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FPGAs contain programmable logic components called "logic blocks", and a

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and zeros on its internal programmable interconnect fabric, and field-programmable

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Some of the industry’s foundational concepts and technologies for programmable

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2.4 FPGA PROGRAMMING OVERVIEW

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FPGA programming is highly non-portable.

There is only a limited amount of resources on the FPGA.

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2.5 FEATURES AND ASPECTS OF THE LANGUAGE

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2.5.4 BLOCK EXPRESSIONS

2.5.5 DATA I/O

2.6.1 PROGRAM SUITABILITY

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2.6.2 INTERACTING WITH THE FPGA

2.6.3 MITRION SDK PE

2.7 MODERN DEVELOPMENTS

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An alternate approach to using hard-macro processors is to make use of soft

As previously mentioned, many modern FPGAs have the ability to be reprogrammed

Additionally, new, non-FPGA architectures are beginning to emerge. Software-

2.9 MARKET SIZE

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 ~1993: >$385 million

2.10 FPGA DESIGN STARTS

2.11 FPGA COMPARISONS

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2.12 COMPLEX PROGRAMMABLE LOGIC DEVICES

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2.13 SECURITY CONSIDERATIONS