A Programmable Logic Controller (PLC) or Programmable Controller is an electronic device used for Automation of industrial processes, such as control of machinery on factory assembly lines.

1. PROGRAMMABLE
LOGIC
CONTROLLER

2. Control Systems TypesControl Systems Types
 Programmable Logic Controllers
 Distributed Control System
 PC- Based Controls

3. Programmable Logic ControllersProgrammable Logic Controllers
PLC
 Sequential logic solver
 PID Calculations.
 Advanced Subroutines
 BIT Operations.
 Data Transfer.
 Text Handling.

4. Applications :
 Machine controls, Packaging, Palletizing, Material handling, similar
Sequential task as well as Process control
Advantages of PLC :
 They are fast and designed for the rugged industrial environment.
 They are attractive on Cost-Per-Point Basis.
 These Devices are less Proprietary ( E.g.. Using Open Bus Interface.)
 These Systems are upgraded to add more Intelligence and Capabilities
with dedicated PID and Ethernet Modules.
Disadvantages of PLC :
 PLC were Designed for Relay Logic Ladder and have Difficulty with
some Smart Devices.
 To maximize PLC performance and Flexibility, a number of Optional
Modules must be added
Programmable Logic ControllersProgrammable Logic Controllers

5. PLC Types
 Nano (Small)
 Micro (Medium)
 Large
Basic criteria for PLC Types
 Memory Capacity
 I/O Range
 Packaging and Cost per Point
Programmable Logic ControllersProgrammable Logic Controllers

6. Components
 Central Processing Unit (CPU)
 Input Output Modules
 Power Supply
 Bus system
Programmable Logic ControllersProgrammable Logic Controllers

7. Central Processing Unit
 It is a micro-controller based circuitary. The CPU consists
of following blocks :
Arithmatic Logic Unit (ALU), Program memory
Process image memory (Internal memory of CPU)
Internal timers and counters
Flags
 CPU performs the task necessary to fulfill the PLC
funtions. These tasks include Scanning, I/O bus traffic
control, Program execution, Peripheral and External device
communication, special functions or data handling
execution and self diagnistics.
Programmable Logic ControllersProgrammable Logic Controllers

8. Input module
 These modules act as interface between real-time status of
process variable and the CPU.
 Analog input module : Typical input to these modules is
4-20 mA, 0-10 V
Ex : Pressure, Flow, Level Tx, RTD (Ohm), Thermocouple
(mV)
 Digital input module : Typical input to these modules is 24 V
DC, 115 V AC, 230 V AC
Ex. : Switches, Pushbuttons, Relays, pump valve on off
status
Programmable Logic ControllersProgrammable Logic Controllers

9. Output module
 These modules act as link between the CPU and the output
devices in the field.
 Analog output module : Typical output from these modules
is 4-20 mA, 0-10 V
Ex : Control Valve, Speed, Vibration
 Digital output module : Typical output from these modules
is 24 V DC, 115 V AC, 230 V AC
Ex. : Solenoid Valves, lamps, Actuators, dampers, Pump
valve on off control
Programmable Logic ControllersProgrammable Logic Controllers

10. Power Supply
 The power supply gives the voltage required for
electronics module (I/O Logic signals, CPU, memory
unit and peripheral devices) of the PLC from the line
supply.
 The power supply provides isolation necessary to
protect the solid state devices from most high voltage
line spikes.
 As I/O is expanded, some PLC may require additional
power supplies in order to maintain proper power
levels.
Programmable Logic ControllersProgrammable Logic Controllers

11. Bus System
 It is path for the transmission of the signal . Bu system is
responsible for the signal exchange between processor
and I/O modules
 The bus system comprise of several single line ie wires /
tracks
Programmable Logic ControllersProgrammable Logic Controllers

12. PLC CyclePLC Cycle
Outputs
Machine
or
Process
Programmable
controller
Inputs
 Sense the Input
 Process the Logic
 Give Output

13. PLC Signal FlowPLC Signal Flow
Programming Terminal
O:0/7
O:0/7
O:1/5
Output Devices
Output ModulesProcessor MemoryInput Module
Input Devices
Ladder Program
O:0/7
O:1/5
I:0/6
I:1/4
O:1/5
I:0/6
I:1/4
I:0/6
I:1/4
DataInput
Image Table
Output
Image Table

14. PLC Architecture EvolutionPLC Architecture Evolution
Mid - 1970s : Discrete Machine Control
Programming
Terminal
PLC
I/O
Connection is Point to Point
Programming Language :
- Relay ladder logic
- Flexibility in altering
Control system operation
Connection is Point to Point

15. Early - to - Mid 1980 : Discrete and Process Control
PLC Architecture EvolutionPLC Architecture Evolution
Reasonable Computer
Running PLC
Programming Software
PLC
I/O
Programming Language :
- Ladder Program
- PID
- Data Storage
MS - DOS

16. PLC Architecture EvolutionPLC Architecture Evolution
Late 1980’s to early 1990’s : Discrete and Process
Control
PC running
PLC Programming Software
PLC
I/O
Connection in networked allowing
Multiple PLC
PLC became a part of the
developing enterprise resource
system
Windows
PLC

17. TodayToday :: Distributed I/O ModulesDistributed I/O Modules
Distributed I/O modules
PL
C
Distributed I/O scanner
Data Communication Bus
PLC Architecture EvolutionPLC Architecture Evolution

18. Remote
I/O Network
SPLITTERS
FIBER OPTIC LINK
TAPS
Remote I/O
Today :Today : Hot Redundant SystemHot Redundant System
PLC Architecture EvolutionPLC Architecture Evolution

19. Controller Controller
Controller
Controller
Workstation Workstation Workstation Workstation
Switched Hub
PLC Architecture EvolutionPLC Architecture Evolution
Today :Today : Ethernet Technology in PLCsEthernet Technology in PLCs

20. Remote
Platform
Wireless Modem
Wireless Modem
PLC
H M I
Display
PC
PLC Architecture EvolutionPLC Architecture Evolution
Today :Today : Wireless communicationWireless communication
PLC

21. PLC Systems of various vendorsPLC Systems of various vendors
Siemens
 S5 -110U, 115U, 135U
 S7 - 200, 300, 400
Allen Bradley
 Micrologix 1000, 1200, 1500
 SLC 5/01, 5/02, 5/03
 PLC 5/10, 5/25 and 5/40
Modicon
 Nano
 Micro
 Premium
 Quantum

22. 8 Analog Inputs 1
Analog Output
Up/Down Fast
Counter
Up Counter
Programming Terminal PC Connection
Unitelway Port for connection
of up to 5 Slaves
PCMCIA memory expansion port
PCMCIA communications port
TSX37-22
Built in display for I/O
(in-rack, AS-i) and Diag
I/O Modules
Configuration of PLC : ModiconConfiguration of PLC : Modicon

23. Configuration of PLC : SiemensConfiguration of PLC : Siemens
CPU
External Power
Supply
I/O Modules

24. Configuration of PLC : Allen BradleyConfiguration of PLC : Allen Bradley
CPU
Power Supply
I/O Modules

25. Configuration of PLC : GE FANUCConfiguration of PLC : GE FANUC
CPU
I/O Modules Back plane

26. PLC Programming StandardsPLC Programming Standards
The open, manufacturer-independent programming
standard for automation is IEC 61131-3. You can thus choose
what configuration interface you wish to use when writing your
application :
 Ladder Diagram
 Instruction List
 Function Block Diagram
 Sequential Function Chart
 Structured Text

27.  Cost of hardware, software, Integration Engineering,
Design, Installation, Start-up and Commissioning,
Validation documentation and Execution, Training, Spare
parts, Maintenance, System service contract and system life
cycle.
 Reliability, Flexibility, Scalability and Validatability.
 Ease of Database configuration, Graphics development,
Interlocks and Batch processing.
 Integration of High-level Application.
 Control Philosophy for Centralized versus Remote
Operator Console or both.
 Compliance with an Industry batch standard such as ISA
SP88 and new Communication Protocol.
PLC DCS Selection CriteriaPLC DCS Selection Criteria