PAKISTAN INDUSTRIAL TECHNICAL
National ASSISTANCE
Electronics Complex ofCENTRE (PITAC) PESHAWAR
Pakistan
Presenter: Khalid Jamil Azizi (Dir. AT/HRD, NECOP)
PLC
Programmable Logic Controller
Presented by
Engr. Sardar Hussain
Eligible person
D.A.E Electrical
D.A.E Electronics
D.A.E Instruments
D.A.E Automation
Engineers (Electrical, Electronics,Mechanical)
B-Tech (Electrical, Electronics)
Definition of PLC
A digital electronic device that uses a programmable memory to
store instructions and to implement specific functions such as
• Logic
• Sequence
• Timing
• Counting
• Arithmetic
• Analogue Application
Comparison
Hardwired control systems PLC Systems
• The functions are determined • The functions are determined
by the physical wiring. by a program stored in the
memory.
• Changing the function means • The control functions can be
changing the wiring. changed simply by changing
the program.
• Can be contact-making type
(relays, contactors) or • Consist of a control device,
electronic type (logic circuits) to which all the sensors and
actuators are connected.
Hardwire control panel
OUTPUTS
INPUTS MOTOR
CONTACTOR
LAMP
PUSHBUTTONS
PLC
7
The Basic Sections
CPU+Memory
Inputs Outputs
Operator
interface
Major Components of a Common PLC
POWER
SUPPLY
I M O M
N O
P D U O
U U PROCESSOR T D
T L P U
From E U L
To
SENSORS T E
OUTPUT
Pushbuttons, Solenoids,
contacts, contactors,
limit switches, alarms
etc. etc.
PROGRAMMING
DEVICE
9
Major Components of a Common PLC
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.
10
Major Components of a Common PLC
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.
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Inputs
Program
Outputs
What are Inputs?
• Switches and Pushbuttons
• Sensing Devices
• Limit Switches
• Photoelectric Sensors
• Proximity Sensors
• Condition Sensors
• Pressure Switches
• Level Switches
• Temperature Switches
• Vacuum Switches
• Encoders
What are Outputs?
• Valves
• Motor Starters
• Solenoids
• Actuators
• Control Relays
• Horns & Alarms
• Stack Lights
• Fans
• Counter
• Pumps
• Printers
Operator Interface
List of items required when
working with PLCs:
1. Programming Terminal - laptop
or desktop PC.
2. PLC Software. PLC
manufacturers have their own
specific software and license
key.
3. Communication cable for
connection from Laptop to PLC.
PLC Size
1. SMALL - it covers units with up to 128 I/O’s and
memories up to 2 Kbytes.
- these PLC’s are capable of providing
simple to advance levels or machine
controls.
2. MEDIUM - have up to 2048 I/O’s and memories up
to 32 Kbytes.
3. LARGE - the most sophisticated units of the PLC
family. They have up to 8192 I/O’s and
memories up to 750 Kbytes.
- can control individual production
processes or entire plant.
16
Selecting a PLC
Criteria
• Number of logical inputs and outputs.
• Memory
• Number of special I/O modules
• Scan Time
• Communications
• Software
Programming Languages of PLC
Most common programming languages
are:
1) Ladder Logic
2) Functional Block Diagram (FBD)
3) Sequential Function Chart (SFC)
PLC Programming
Ladder logic is the main programming method used
for PLCs [39]
It is a visual and symbolic programming language that
resembles relays logic diagrams
Ladder logic has been developed to copy relay logic to
reduce amount of retraining needed for engineers and
trades people
Ladder Logic
• Ladder logic uses a
variety of
Power rails
programming
symbols
Normally
• Power always flows Closed Contact
from left to right
Normally
• Output devices are Open Contact
in the ON state if
power flows through Output
them Device or Coil
Contacts
Power flows when
Contact
programmed
the input device is
normally open on
Power flows when
Contact
programmed the input device is
normally closed
off
Ladder Logic
Button Motor
Motor output
Motor Off lamp
Contacts
Lamp for power
applied
Motor On lamp
Lamp for power
not applied
Ladder Logic
Start Stop
button button Motor
Latching is the term for
a self-maintaining
circuit.
Motor
AND OPERATION
A B C
Rung
24
OR OPERATION
A C
Rung
25
NOT OPERATION
A C
Rung
In the rung above, it can be seen that if input A is be true (1),
then the output C is true (0) or when A is (0), output C is 1.
26
Leading Brands Of PLC
AMERICAN 1. Allen Bradley
2. Gould Modicon
3. Texas Instruments
EUROPEAN 1. Siemens
2. Festo
3. Telemechanique
27
Leading Brands Of PLC
JAPANESE 1. Toshiba
2. Omron
3. Fanuc
4. Mitsubishi
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List of items required when working with PLCs:
1. Programming Terminal - laptop or desktop PC.
2. PLC Software. PLC manufacturers have
their own specific software and license key.
3. Communication cable for connection from Laptop
to PLC.
4. Backup copy of the ladder program
5. Documentation- (PLC manual, Software manual,
drawings,
ladder program printout, and Seq. of Operations
manual.)
PLC Advantages
•Visual observation
•Less and simple wiring.
•Increased Reliability.
•More Flexibility.
•Lower Cost .
•Faster Response.
•Easier to troubleshoot.
•Remote control capability.
•Communication Capability.
Disadvantages Of Plcs
Newer technology
Fixed Circuit Operations.
PLC devices are proprietary it means that part or software
of one manufacturer can’t be used in combination with
parts of another manufacturer.
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.
PLC Status Indicators
•Power On
•Run Mode
•Programming Mode
•Fault
Troubleshooting
1. Look at the process
2. PLC status lights
HALT - something has stopped the CPU
RUN - the PLC thinks it is OK (and probably is)
ERROR - a physical problem has occurred with the
PLC
3. Indicator lights on I/O cards and sensors
4. Consult the manuals, or use software if available.
5. Use programming terminal / laptop.
Areas of Application
Manufacturing / Machining
Food / Beverage
Metals
Power
Mining
Petrochemical / Chemical
35
HUMAN MACHINE INTERFACE
(HMI)
HARDWARE
LOCAL DISPLAY
GRAPHICAL DISPLAY
SUPERVISORY CONTROL & DATA
ACQUISITION SYSTEM (SCADA)
SOFTWARE
REMOTE & GRAPHICAL DISPLAY
CONTROL ROOM APPLICATION
REMOTELY ACCESSES ALL FIELD DEVICES
Thank You!
Thank You!
Any Question
