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Programmable logic controllers (PLCs) have been an integral part of factory automation and industrial process control for decades. PLCs control a wide array of applications from simple lighting functions to environmental systems to chemical processing plants. These systems perform many functions, providing a variety of analog and digital input and output interfaces; signal processing; data conversion; and various communication protocols. All of the PLC's components and functions are centered around the controller, which is programmed for a specific task.
The basic PLC module must be sufficiently flexible and configurable to meet the diverse needs of different factories and applications. Input stimuli (either analog or digital) are received from machines, sensors, or process events in the form of voltage or current. The PLC must accurately interpret and convert the stimulus for the CPU which, in turn, defines a set of instructions to the output systems that control actuators on the factory floor or in another industrial environment
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• Introduction of PLC
• Introduction of Scada
• What is PLC
• Importance of PLC
• How PLC works
• What is Scada
• Importance of Scada
• How Scada works
• Components of SCADA
• Scada Architectures
• Why Plc-Scada
• Benefits Of PLC-Scada
• Scope of PLC-Scada
TABLE OF CONTENT
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INTRODUCTION OF PLC
Programmable logic controllers (PLCs) have been an integral part of factory
automation and industrial process control for decades. PLCs control a wide array of
applications from simple lighting functions to environmental systems to chemical
processing plants. These systems perform many functions, providing a variety
of analog and digital input and output interfaces; signal processing; data conversion;
and various communication protocols. All of the PLC's components and functions
are centered around the controller, which is programmed for a specific task.
The basic PLC module must be sufficiently flexible and configurable to meet the
diverse needs of different factories and applications. Input stimuli (either analog or
digital) are received from machines, sensors, or process events in the form
of voltage or current. The PLC must accurately interpret and convert the stimulus for
the CPU which, in turn, defines a set of instructions to the output systems that
control actuators on the factory floor or in another industrial environment.
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INTRODUCTION OF SCADA
SCADA (Supervisory Control and Data Acquisition)
Now a days automation system contains PLCs and SCADA software. If you use PLC &
SCADA combination the advantages you have is you have better monitoring and
control of the plant and also you have access to the information the way you want.
SCADA enables engineers, supervisors, managers and operators to view and interact
with the workings of entire operations through graphical representation of their
SCADA runs on a PC and is generally connected to various PLCs and other peripheral
devices. It enables you to generate applications for the most demanding
requirements of plant engineers, operators, supervisors and managers tailored
precisely to the needs of each plant. SCADA constantly gathers data from the plant
in real-time, stores and processes it in the database, evaluates and generates
alarms, displays information to plant operators, supervisors and managers and can
issue instructions to PLCs on the plant floor.
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PLC: A PROGRAMMABLE LOGIC
A Programmable Logic Controller, or PLC, is more or less a small computer
with a built-in operating system (OS). This OS is highly specialized to handle
incoming events in real time, or at the time of their occurrence.
The PLC has input lines where sensors are connected to notify upon events
(e.g. temperature above/below a certain level, liquid level reached, etc.),
and output lines to signal any reaction to the incoming events (e.g. start an
engine, open/close a valve, etc.).
The system is user programmable. It uses a language called "Relay Ladder"
or RLL (Relay Ladder Logic). The name of this language implies that the
control logic of the earlier days, which was built from relays, is being
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IMPORTANCE OF PLC
The PLC is primarily used to control machinery. A program is written for the
PLC which turns on and off outputs based on input conditions and the
internal program. In this aspect, a PLC is similar to a computer. However, a
PLC is designed to be programmed once, and run repeatedly as needed. In
fact, a crafty programmer could use a PLC to control not only simple devices
such as a garage door opener, but their whole house, including switching
lights on and off at certain times, monitoring a custom built security system,
Most commonly, a PLC is found inside of a machine in an industrial
environment. A PLC can run an automatic machine for years with little
human intervention. They are designed to withstand most harsh
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HOW PLC LOOKS
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HISTORY OF PLC
When the first electronic machine controls were designed, they used relays to
control the machine logic (i.e. press "Start" to start the machine and press "Stop" to
stop the machine). A basic machine might need a wall covered in relays to control all
of its functions. There are a few limitations to this type of control.
The delay when the relay turns on/off.
There is an entire wall of relays to design/wire/troubleshoot.
A PLC overcomes these limitations, it is a machine controlled operation.
PLCs are becoming more and more intelligent. In recent years PLCs have been
integrated into electrical communications(Computer network)i.e., all the PLCs in an
industrial environment have been plugged into a network which is usually
hierarchically organized. The PLCs are then supervised by a control centre. There
exist many proprietary types of networks. One type which is widely known is SCADA
(Supervisory Control and Data Acquisition).
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PLC: A PROGRAMMABLE LOGIC CONTROLLER
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HOW PLC WORKS
How the PLC operates: The PLC is a purpose-built machine control
computer designed to read digital and analog inputs from various sensors,
execute a user defined logic program, and write the resulting digital and
analog output values to various output elements like hydraulic and
pneumatic actuators, indication lamps, solenoid coils, etc.
Scan cycle: Exact details vary between manufacturers, but most PLCs follow
a 'scan-cycle‘s format.
Overhead includes testing I/O module integrity, verifying the user program
logic hasn't changed, that the computer itself hasn't locked up (via a
watchdog timer), and any necessary communications. Communications may
include traffic over the PLC programmer port, remote I/O racks, and other
external devices such as HMIs (Human Machine Interfaces).
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Input scan A 'snapshot' of the digital and analog values present at the input
cards is saved to an input memory table. Logic execution The user program
is scanned element by element, then rung by rung until the end of the
program, and resulting values written to an output memory table .Output
scan Values from the resulting output memory table are written to the
output modules. Once the output scan is complete the process repeats
itself until the PLC is powered down.
The time it takes to complete a scan cycle is, appropriately enough, the
"scan cycle time", and ranges from hundreds of milliseconds (on older PLCs,
and/or PLCs with very complex programs) to only a few milliseconds on
newer PLCs, and/or PLCs executing short, simple code.
HOW PLC WORKS
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(SUPERVISORY CONTROL AND DATA ACQUISITION)
SCADA is a system operating with coded signals over communication
channels so as to provide control of remote equipment (using typically one
communication channel per remote station). The supervisory system may
be combined with a data acquisition system by adding the use of coded
signals over communication channels to acquire information about the
status of the remote equipment for display or for recording functions. It is a
type of industrial control system (ICS). Industrial control systems
are computer-based systems that monitor and control industrial processes
that exist in the physical world. SCADA systems historically distinguish
themselves from other ICS systems by being large-scale processes that can
include multiple sites, and large distances.
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(SUPERVISORY CONTROL AND DATA ACQUISITION)
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IMPORTANCE OF SCADA
Scada processes include industrial, infrastructure, and facility-based
processes, as described below:
Industrial processes include those of manufacturing,
production, power generation, fabrication, and refining, and may run
in continuous, batch, repetitive, or discrete modes.
Infrastructure processes may be public or private, and include water
treatment and distribution, wastewater collection and treatment, oil
and gas pipelines, electrical power
transmission and distribution, wind farms, civil defense siren systems,
and large communication systems.
Facility processes occur both in public facilities and private ones,
including buildings, airports, ships, and space stations. They monitor
and control heating, ventilation, and air conditioning systems
(HVAC), access, and energy consumption.
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SCADA can be a great tool while working in an environment where
operational duties need to be monitored electronical communication
instead of locally. For example, an operator can position a valve to open or
closed as desired through SCADA without leaving the control station or the
computer. The SCADA system also allows to switch a pump or motor on or
off and has the capability of putting motors on a Hand operating status, off,
or Automatic. Hand would be referring to operate the equipment locally,
and automatic would be scaling the equipment to be operated according to
set points the operator instructs on a computer that can communicate with
the equipment through SCADA.
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COMPONENTS OF SCADA
Remote terminal units (RTUs) connect to sensors in the process and convert
sensor signals to digital data. They have telemetry hardware capable of
sending digital data to the supervisory system, as well as receiving digital
commands from the supervisory system. RTUs often have embedded
control capabilities such as ladder logic in order to accomplish boolean logic
Programmable logic controller (PLCs) connect to sensors in the process
and converting sensor signals to digital data. PLCs have more sophisticated
embedded control capabilities, typically one or more IEC 61131-
3 programming languages, than RTUs. PLCs do not have telemetry
hardware, although this functionality is typically installed alongside them.
PLCs are sometimes used in place of RTUs as field devices because they are
more economical, versatile, flexible, and configurable.
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A telemetry system is typically used to connect PLCs and RTUs with control
centers, data warehouses, and the enterprise. Examples of wired telemetry
media used in SCADA systems include leased telephone lines and WAN
circuits. Examples of wireless telemetry media used in SCADA systems
include satellite (VSAT), licensed and unlicensed radio, cellular and
A data acquisition server is a software service which uses industrial
protocols to connect software services, via telemetry, with field devices
such as RTUs and PLCs. It allows clients to access data from these field
devices using standard protocols.
A human–machine interface or HMI is the apparatus or device which
presents processed data to a human operator, and through this, the human
operator monitors and interacts with the process. The HMI is a client that
requests data from a data acquisition server.
COMPONENTS OF SCADA
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A Historian is a software service which accumulates time-stamped
data, boolean events, and boolean alarms in a database which can be
queried or used to populate graphic trends in the HMI. The historian is a
client that requests data from a data acquisition server.
A supervisory (computer) system, gathering (acquiring) data on the process
and sending commands (control) to the SCADA system.
Communication infrastructure connecting the supervisory system to the
remote terminal units.
Various process and analytical instrumentation
COMPONENTS OF SCADA
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HOW SCADA WORKS
The term SCADA usually refers to centralized systems which monitor and
control entire sites, or complexes of systems spread out over large areas
(anything from an industrial plant to a nation). Most control actions are
performed automatically by RTUs or by PLCs. Host control functions are
usually restricted to basic overriding or supervisory level intervention. For
example, a PLC may control the flow of cooling water through part of an
industrial process, but the SCADA system may allow operators to change
the set points for the flow, and enable alarm conditions, such as loss of flow
and high temperature, to be displayed and recorded. The feedback control
loop passes through the RTU or PLC, while the SCADA system monitors the
overall performance of the loop.
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Data acquisition begins at the RTU or PLC level and includes meter readings
and equipment status reports that are communicated to SCADA as
required. Data is then compiled and formatted in such a way that a control
room operator using the HMI can make supervisory decisions to adjust or
override normal RTU (PLC) controls. Data may also be fed to a Historian,
often built on a commodity Database Management System, to allow
trending and other analytical auditing.
HOW SCADA WORKS
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SCADA systems typically implement a distributed database, commonly
referred to as a tag database, which contains data elements called
tags or points. A point represents a single input or output value monitored
or controlled by the system. Points can be either "hard" or "soft". A hard
point represents an actual input or output within the system, while a soft
point results from logic and math operations applied to other points. (Most
implementations conceptually remove the distinction by making every
property a "soft" point expression, which may, in the simplest case, equal a
single hard point.)
SCADA systems are significantly important systems used in national
infrastructures such as electric grids, water supplies and pipelines.
However, SCADA systems may have security vulnerabilities, so the systems
should be evaluated to identify risks and solutions implemented to
mitigate those risks.
HOW SCADA WORKS
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First generation: "Monolithic“
Early SCADA system computing was done by large minicomputers. Common
network services did not exist at the time SCADA was developed. Thus
SCADA systems were independent systems with no connectivity to other
systems. The communication protocols used were strictly proprietary at
that time. The first-generation SCADA system redundancy was achieved
using a back-up mainframe system connected to all the Remote Terminal
Unit sites and was used in the event of failure of the primary mainframe
system. Some first generation SCADA systems were developed as "turn key"
operations that ran on minicomputers such as the PDP-11 series made by
the Digital Equipment Corporation
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Second generation: "Distributed“
SCADA information and command processing was distributed across
multiple stations which were connected through a LAN. Information was
shared in near real time. Each station was responsible for a particular task
thus making the size and cost of each station less than the one used in First
Generation. The network protocols used were still not standardized. Since
the protocols were proprietary, very few people beyond the developers
knew enough to determine how secure a SCADA installation was. Security
of the SCADA installation was usually overlooked.
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Third generation: "Networked“
Similar to a distributed architecture, any complex SCADA can be reduced to
simplest components and connected through communication protocols. In
the case of a networked design, the system may be spread across more
than one LAN network and separated geographically. Several distributed
architecture SCADAs running in parallel, with a single supervisor and
historian, could be considered a network architecture. This allows for a
more cost effective solution in very large scale systems.
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Fourth generation: "Internet of Things“
With the commercial availability of cloud computing, SCADA systems have
increasingly adopted Internet of Things technology to significantly reduce
infrastructure costs and increase ease of maintenance and integration. As a
result SCADA systems can now report state in near real-time and use the
horizontal scale available in cloud environments to implement more
complex control algorithms than are practically feasible to implement on
traditional programmable logic controllers. Further, the use of open
network protocols such as TLS inherent in Internet of Things technology
provides a more readily comprehendable and manageable security
boundary than the heterogeneous mix of proprietary network protocols
typical of many decentralized SCADA implementations.
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In recent times, all most every industry use automation or control systems
for working. Every industry needs more engineers to grow their production
rate. Foreign countries have also understood the importance of automation.
It is a type of control system which involves information technology and
reduces the human manually works in production. For automation industry
PLC and SCADA are the most important tools, without these tools
automation is not possible. It plays a vital role in the world economy as it
replaces all manual systems power.
If you want to get a best job in automation industry, you must have an idea
about industry’s requirement. Almost every industry needs professionally
trained students who have some experience and detailed knowledge about
PLC-Scada technology. Candidate needs to get trained in the same, because
Training helps them to get practical knowledge and skills that required to
get placed in a famous industry. By getting trained with the professionals
who have industry experience, you will get the industry exposure with the
industrial training project as well.
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If you are looking for a better career in an automation industry after
completing your degree, You should get trained from the company who has
expertise in the same. Appin is a well-known company in the field of
Information Technology which provides industrial training for all courses
related to IT, electronics and telecom field. We also provides the Job
Oriented Training programs in Information Security/IRM/Secured
Application programming/ Secured Mobile Application Development
programming in Android, BlackBerry, iOS. Our placement record is better
than other players in the market.
Our training programs are on the latest technologies with the updated
versions & advanced concepts. Like cloud computing PLC-Scada.
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HOW SCADA LOOKS
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BENEFITS OF PLC-SCADA
PLC and SCADA are the success behind the automation industry. PLC is designed
in such a way that it can be used to control multiple inputs and outputs and it
can be handled in extreme temperature changes. Without these two
automation concepts the automation industry fails. So there is a huge demand
for skilled manpower in PLC and SCADA in automation industry. We cannot even
think of surviving without this technology even for a day. If the system fails then
there would be losses of cores of rupees. After the application of PLC and
SCADA technology in Industrial automation process.
It is creating a lot of employment opportunities
There is a huge demand for skilled manpower in this sector
Economies of scale
Increased Accuracy and speed
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SCOPE OF PLC SCADA
If you have PLC-Scada training certificate , you will get a chance in different
companies on different profiles specially in the manufacturing industry.
Some of the profiles are mentioned below:-
1. PLC-SCADA Trainee
2. PLC-SCADA Software Engineer
3. Automation and Drives manufacturer at global firms
4. PLC SCADA HMI AC DC
5. Application Engineer – PLC-Scada
6. Electrical Maintenance automation Manager maintenance
Manager PLC SCADA
7. Automation Engineer.
8. Instrumentation Engineer.
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COMPANIES HIRING FOR PLC SCADA
and many more….
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For more details please visit:
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