PLC (PROGRAMMABLE LOGIC CONTROLLER)

Presented By
(PROGRAMMABLE LOGICCONTROLLER)
“PLC”
Manoj K
M.Tech (CIM)
1MS16MCM09

Contents
 What is PLC?
 History of PLC
 Major components of PLC
 Operational sequence of PLC
 Ladder logic
 Advantages
 Disadvantages
 Application
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What is PLC?
PLC is an industrial computer designed
for multiple inputs and output
arrangements.
It is capable of storing the instructions to
implement control functions such as
sequencing, timing, counting,
arithmetic, data manipulation and
communication.
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History of PLC
 PLC was introduced in late 1960’s
 First commercial & successful
Programmable Logic Controllers was
designed and developed by Modicon as a
relay replacer for General Motors.
 Earlier, it was a machine with thousands of
electronic parts.
 Later ,in late 1970’s,the microprocessor
became reality & greatly enhanced the role
of PLC permitting it to evolve form simply
relay to the sophisticated system as it is
today.
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PROCESSOR
POWER
SUPPLY
I M
N O
P D
U U
T L
E
O M
U O
T D
P U
U L
T E
PROGRAMMING
DEVICE
From
SENSORS
Pushbuttons,
contacts,
limit switches,
etc.
To
OUTPUT
Solenoids,
contactors,
alarms
etc.
Major Components
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POWER SUPPLY
Provides the voltage needed to run the primary PLC components
I/O MODULES
Provides signal conversion and isolation between the internal logic-
level signals inside the PLC and the field’s high level signal.
PROCESSOR
Provides intelligence to command and govern the activities of the entire
PLC systems.
PROGRAMMING DEVICE
Used to enter the desired program that will determine the sequence of
operation and control of process equipment or driven machine.
Major Components
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PLC operation sequence
1)Self test: Testing of its own hardware and
software for faults.
2)Input scan: If there are no problems, PLC
will copy all the inputs and copy their values
into memory.
3)Logic solve/scan: Using inputs, the ladder
logic program is solved once and outputs are
updated.
4)Output scan: While solving logic the output
values are updated only in memory when
ladder scan is done, the outputs will be
updated using temporary values in memory.
Self test
Input scan
Logic scan
Output
scan
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Programming Languages of
PLC
Most common languages encountered in PLC
programming are:
1) Ladder Logic
2) Functional Block Diagram
3) Sequential Function Chart
4) Boolean mnemonics
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Ladder logic is a programming language
used to develop software for PLC used in
industrial control applications.
RUNGES
RAIL RAIL
Ladder Logic
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Ladder Logic
language for PLC.
 It is well suited to express Combinational
logic.
The main ladder logic symbols represent
the
elements :
Make contact
Break contact
Relay coil
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Ladder Logic For Basic
gates
A B Logic(Y)
OFF
OFF
ON
ON
OFF
ON
OFF
ON
OFF
OFF
OFF
ON
AND Gate
A B Logic(Y)
OFF
OFF
ON
ON
OFF
ON
OFF
ON
OFF
ON
ON
ON
R Gate
OR Gate
A
OR Gate
A
A B
B
Y
Y
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NOR Gate
A B Y
A B Logic(Y)
OFF
OFF
ON
ON
OFF
ON
OFF
ON
ON
ON
ON
OFF
A B Logic(Y)
OFF
OFF
ON
ON
OFF
ON
OFF
ON
ON
OFF
OFF
OFF
NAND Gate
B
Y
A
Ladder Logic For Basic gate
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Block diagram of a PLC
OutputsLED
s
Inputs
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Programming Example:
 Ladder Logic Program for Start/Stop of
Motor :
X1
Y1
Y1X2
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Advantages of PLCs:
 Reliability.
 Flexibility in programming and reprogramming.
 Cost effective for controlling complex systems.
 Small physical size.
 High speed of operation.
 Ease of maintenance /troubleshooting.
 Reduced space.
 Energy saving.
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Disadvantages of PLCs
 PLC devices are proprietary it means that part or
software of one manufacturer can’t be used in
combination with parts of another manufacturer.
 Limited design and cost option.
 Fixed Circuit Operations.
 PLCs manufacturers offer only closed
architectures.
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Applications:
 Wherever automation is desired the PLCs are best
suited to meet the task.
 Few examples of industries where PLCs are used :
1) Robots manufacturing and control
2) Car park control
3) Train control station system
4) Food processing
5) Materials handling
6)Machine tools
7)Conveyer system etc.
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Case study-1
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18
Automation of Soda Ash Handling System using
PLC
and SCADA in Glass Production Line
The glass production line all systems are controlled by DCS
(Distributed Control System) but some sub systems are controlled by
Electromechanical Relay System (Hard Wired Control System).
The relay control system looks toward many issues. To limit that
issues the system change from relay control system to PLC
(Programmable logic controller) control system. In this proposed
system all parameters are controlled, processed and monitored with
help of Allen Bradley PLC.
Abstract

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Schematic Diagram of Soda Ash Handling
System

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Ladder Logic Program

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Ladder Logic Program (cont…)

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Ladder Logic Program (cont…)

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This proposed system was implemented for overcome the
drawbacks of existing system.
This system gives high reliability, easy to trouble shoot, easy to
modify the sequence without changing of wiring, it reduce the
fault occurrence, it eliminated hardwiring, easy to monitoring,
easy to find out the problem occur in the system.
So the system improves the overall productivity and also it
reduce system breakdown because of using programmable logic
controller.
Conclusion

Case study-2
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26
AUTOMATION OF CONVEYOR USING PLC
Abstract - The development of programmable logic
controller (PLC) makes it possible to do the required
changes to the program without changing the electrical
circuit connections.
The Siemens s7-300 series programmable logic
controller is used to mechanize the system and
software for programming used is SIMATIC
manager.

Case study-2(cont…)
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27
Siemens s7-300

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FLOW CHART

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Program in SIMATIC Manager software
Here programming language used is functional block diagram.
Here to make program faster and save memory function block
used.
Following pictures shows program to control conveyor motor in
function block.

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30
Conclusion
Efficient monitoring and control of industrial automation.
There will be immense control and monitoring of
conveyor belt.
Possible to do the required changes to the program
without changing the electrical circuit connections.

PLC (PROGRAMMABLE LOGIC CONTROLLER)

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