PLC Based Automation System

Presented By:
Ruma Bharti
AGM (PC&A)

Gourav Garg
JM (PC&A)
 Highlights:

• Need of Industrial Automation

• Components of Automation
• Different Levels in Automation
• Types of Control system
• Example of Industrial Automation
• PLC
 What is Automation ?..

Automation = Auto + Matos (Greek Words)

SELF MOVING

So, Automation is ‘self dictating’ or ‘a mechanism move by

itself’
 Industrial Automation
• Industrial Automation is the replacement with
computers and machines to that of human
thinking in order to achieve followings:

• Higher Productivity
• Optimum cost of operation
• Reduced man power cost
• Better Accuracy
• Improved product quality
• Reduction in down time
• Reduction in frequency of routine checks
• Higher level of Safety
 Need of Industrial Automation

Man power Equipment

Quantity Quality
cost Cost
• Reduce startup and • Controlling the • Reduce • Reduce
stop time process parameter
• Increase efficiency according to the manual equipment
of the machine design. operation failure
• High level of • Reduce no. of
accuracy
accidents

• Process control
• Automatic operation • Proper Interlocks
• Automatic operation
 Components of Automation
• Sensors
• Controller
• Comparator
• Control Element
• HMI
• PLC
 Levels of Automation…..
• Offline
• Ex. Management functions like

IT
Level-4 sales, marketing

al
tri
us
I nd
• offline
• Ex. Inventory control

Level-3 • Online
• Set point control
Level-2,Supervisory Control
n o
ati
tom
Au

Level-1
al
tri

PLC, HMI etc.

us
I nd

Level-0, Field automation

Sensors/ Actuators
Levels of Automation…..

Level-3
(ERP Connectivity)

Level-2
(Process Model)

Level-1
Basic Automation System (PLC, HMI)

Level-0
Instrumentation System
 Management function/
Level 4 ERP Production/ Sales/ Marketing/
Industrial IT

Product development
(Off Line)

Spatial Scale/ Time Scale

Level 3 Overall
Production Control
Manufacturing
(Off-Line)

Level 2 Supervisory Control Shop Floor

(Off-Line, soft real time, Level
General purpose)
Managed by
Level 1
Industrial Automation

Automatic Control Level Automatic

Control
(Real time S/W, Special H/W) Level

Sensors Direct Interface

Level 0 Actuators with Process &
Machine
(Embedded H/W & S/W)
 Management function/
Level 4 Production/ Sales/ Marketing/
Industrial IT

RP Product development

(Off Line)

Level 3 Overall
Manufacturing
Supervisory Control
(Off-Line, soft real time,
General purpose) Shop Floor
Level 2
Level

Automatic Control Level

Managed by
Level 1 (Real time S/W, Special H/W) Automatic
Control
Level

Sensors
Direct Interface
Level 0 Actuators with Process &
(Embedded H/W & S/W) Machine
 Types of Control……..

Manual
Open Control
Looploop
Control
Closed control
Cold water

controller
Sensor

Hot water
 PLANT Automation

Sump

Tank
HMI

Feedback Signal
PLC
Control System

• Desired output
 Before PLC & After PLC

Son’s Room Father’s Room Daughter’s Room

TV 1 LED 1 TV 2
Switch 1 (S1) LED 2 Switch 2 (S2)
 Inside A PLC:

POWER
SUPPLY

I M O M
N O
P D U O
U U T D
PROCESSOR P U
To
T L
From U L OUTPUT
E
SENSORS T E
Solenoids,
Pushbuttons,
contactors,
contacts,
alarms
limit switches,
etc.
etc. PROGRAMMING
DEVICE
Operation of Machine..
Control Circuit- to
Power Circuit- to
provide necessary
turn on/off the
interlocks for
machine.
safety purpose.
 Speed control with Tacho feedback
The drive will attempt to maintain a
constant speed regardless of the
load’s torque. A speed reference is
input into a ramp function generator
which applies reference voltage to
the speed controller over a specified
period of time. This allows a
smoother acceleration of the motor
and connected load. The output of
the speed controller is routed to the
firing circuit, which controls the
amount of voltage applied to the
armature.
 What is Automation
• It is application of machines to tasks once performed by human beings
or, increasingly, to tasks that would otherwise be impossible.
Automation generally implies the integration of machines into a self-
governing system. Automation has revolutionized those areas in which
it has been introduced, and there is scarcely an aspect of modern life
that has been unaffected by it.
• The term automation was coined in the automobile industry about
1946 to describe the increased use of automatic devices and controls in
mechanized production lines.
• In general usage, automation can be defined as a technology
concerned with performing a process by means of programmed
commands combined with automatic feed back to ensure proper
execution of the instructions. The resulting system is capable of
operating without much human intervention.
Negative feedback
 Need for PLC
Consider something as simple as a switch that turns on a light. In this system with a
flick of the switch the light would turn on or off. Beyond that though there is no more
control. If you want light to turn on thirty seconds after the switch has been flipped,
then you would need to buy a timer and do some rewiring. So it is time, labour and
money for any little change.
Now consider the same device with a PLC in the middle. The switch is
fed as an input into the PLC and the light is controlled by a PLC output.
Implementing a delay in this system is easy since all that needs to be
changed is the program in the PLC to use a delay timer.
Programmable Logic Controllers (PLCs),
• Programmable Logic Controllers (PLCs), also
referred to as programmable controllers, are
in the computer family. They are used in
commercial and industrial applications. A PLC
monitors inputs, makes decisions based on its
program, and controls outputs to automate a
process or machine.
 Basic PLC operation
• PLCs consist of

• input modules or points,

• a Central Processing Unit (CPU), and
• output modules or points.

An input accepts a variety of digital or analog signals from

various field devices (sensors) and converts them into a
logic signal that can be used by the CPU. The CPU makes
decisions and executes control instructions based on
program instructions in memory. Output modules convert
control instructions from the CPU into a digital or analog
signal that can be used to control various field devices
(actuators). A programming device is used to input the
desired instructions. These instructions determine what
the PLC will do
for a specific input. An operator interface device allows
process information to be displayed and new control
parameters to be
entered.
Basic PLC operation-contd
 Relay logic (Hard wired control)
Prior to PLCs, many of these control
tasks were solved with
contactor or relay controls. This is
often referred to as hardwired
control. Circuit diagrams had to be
designed, electrical components
specified and installed, and wiring
lists created.
Electricians would then wire the
components necessary to
perform a specific task. If an error
was made the wires had
to be reconnected correctly. A
change in function or system
expansion required extensive
component changes and rewiring.
 Advantages of PLCs
The same, as well as more complex tasks, can be done with
a PLC. Wiring between devices and relay contacts is done in
the PLC program. Hard-wiring, though still required to connect
field devices, is less intensive. Modifying the application and
correcting errors are easier to handle. It is easier to create and
change a program in a PLC than it is to wire and rewire a circuit.

Following are just a few of the advantages of PLCs:

• Smaller physical size than hard-wire solutions.
• Easier and faster to make changes.
• PLCs have integrated diagnostics and override functions.
• Diagnostics are centrally available.
• Applications can be immediately documented.
• Applications can be duplicated faster and less expensively.
Components of PLC
CPU
PLC Chasis
 Terminology
• Sensor- A sensor is a device that converts a physical condition into an
electrical signal for use by the PLC. Sensors are connected to the input of a
PLC.

• Actuators -Actuators convert an electrical signal from the PLC into a

physical condition. Actuators are connected to the PLC output.
 Digital input/ output- ON/OFF

Pushbuttons, toggle switches, limit switches,

proximity switches, and contact closures are
examples of discrete sensors which are
connected to the PLCs are digital inputs
Solenoids, contactor coils, and lamps are
examples of actuator devices connected as
digital outputs
 Analog input/ Analog output
• 0 to 20 milliamps, 4 to 20milliamps, or 0 to 10 volts. Ex a level transmitter

• An analog output is an output signal that has a continuous signal. The

output may be as simple as a 0-10 VDC level that drives an analog meter.
 CPU
• The central processor unit (CPU)
is a microprocessor system that
contains the system memory and
is the PLC decision making unit.
The CPU monitors the inputs and
makes decisions based on
instructions held in the program
memory. The CPU performs
relay, counting, timing, data
comparison, and sequential
operations.
 Programming
• A program consists of one or more
instructions that accomplish a task.
Programming a PLC is simply constructing a
set of instructions. There are several ways to
look at a program such as ladder logic,
statement lists, or function block diagrams.
Hardware
 Software
A software program is required in order to tell
the PLC what instructions it must follow.
Programming software is typically PLC specific.
A software package for one PLC, or one family
of PLCs, such as the S7 family, would not be
useful on other PLCs. The S7-200 uses a
Windows based software program called STEP
7- micro/WIN32.
 Memory

• RAM Random Access Memory (RAM) -memory where data can be directly accessed at any
address. Data can be written to and read from RAM. RAM is used as a temporary storage
area. RAM is volatile, meaning that the data stored in RAM will be lost if power is lost. A
battery backup is required to avoid losing data in the event of a power loss.
• ROM Read Only Memory (ROM) - data can be read from but not written to. This type of
memory is used to protect data or programs from accidental erasure. ROM memory is
nonvolatile. ROM is normally used to store the programs that define the capabilities of the
PLC.
• EPROM –Changing EPROM data requires a special effort. ultraviolet light/ electronically
erasable
• Firmware -application specific software burned into EPROM and delivered as part of the
hardware. Firmware gives the PLC its basic functionality.
 PROTOCOL
• MODBUS
• MODBUS PLUS
• Profi bus
• Device net
• Ethernet
Typical example of PLC application in Steel
plant