1. PROGRAMMABLE
LOGIC
CONTROLLER

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

3. Introduction
The PLC is an assembly of solid state digital logic elements design to make logical decisions and provide outputs.

4. Programmable Logic Controllers
Sequential logic solver
PID Calculations.
Advanced Subroutines
BIT Operations.
Data Transfer.
Text Handling.

5. Programmable Logic Controllers
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

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

7. P L C Components Central Processing Unit (CPU) Input Output Modules
Power Supply
Bus system
Programming Device IN
CPU
OUT m
MODULE
MODULE
PROGRAM
DEVICE

8. P L C : 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.

9. PLC : 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

10. PLC : Input module 120 V ac L1 L2 1 2 3 4 PB input field device
terminal board
Input status
indicator

11. PLC : 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

12. PLC : Output module L2 L1 120 V ac Output status indicator
Output field device 3
Output module
Terminal board 4
Module blown Fuse indicator L2
Output module Terminal board

13. I/O SPECIFICATION INPUT VOLTAGE – Magnitude and type of voltage
ON-STATE INPUT VOLTAGE RANGE – voltage at which signal is recognized
Nominal current per input – Min. current to operate input circuit
AMBIENT TEMP RATING – Max temp of surrounding the I/O module
INPUT DELAY – Time duration for input signal to be on before known as valid input. ( 9-ms to 25ms)
NOMINAL OUTPUT VOLTAGE – It is min and max o/p operating voltage.e.g. Rated 120 v ac o/p ckt. Works in 92 to 138 v range.
MAX O/P CURRENT RATING – Max current a single o/p or module can safely carry under load
OFF –STATELEAK CURRENT PER O/P – Max value of leak current flows through the o/p in OFF position
ELECTRICAL ISOLATION – Max volts between I/o and logic ckt.

14. P L C : 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.

15. P L C : 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

16. Relay Connection L1 L2 L3 M L1 L1 CR CL M M M 1 1 CR T1 T2 T3 2 2 M
MOTOR 3 3 4 4 M L2 L2
MOTOR

17. Advantage of PLC Over Relay Style
RELAY PLC
1-Hard wiring Less wiring
2-Changes difficult Easy modification
3-More power Low power
4-More maintenance 4-Solid state reliability
5-Difficult to expand Ease of expansion

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

19. PLC Signal Flow Output Modules Input Module Processor Memory O:0/7
Data
Input
Image Table
Output
Image Table
O:0/7
I:0/6
I:0/6
I:1/4
O:1/5
Input Devices
Output Devices
Ladder Program
I:0/6
O:0/7
I:1/4
O:1/5
I:1/4
O:1/5
Programming Terminal

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

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

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

23. PLC Architecture Evolution
Today : Distributed I/O Modules
PLC
Distributed I/O scanner
Data Communication Bus
Distributed I/O modules

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

25. Today : Ethernet Technology in PLCs
PLC Architecture Evolution
Today : Ethernet Technology in PLCs
Workstation
Workstation
Workstation
Workstation
Switched Hub
Controller
Controller
Controller
Controller

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

27. PLC Systems of various vendors
Siemens
S5 -110U, 115U, 135U
S , 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

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

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

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

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

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

33. Scan Rate The completion of one cycle of the sequence is called- SCAN
Time required for one cycle is called SCAN TIME

34. PLC DCS Selection Criteria
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.

35. Memory Types ROM (Read Only Memory) RAM (Random Access Memory)
PROM (Programmable ROM)
EPROM (Erasable PROM)
EAROM- Electrically alterable ROM
EEPROM-Electrically erasable PROM

36. Binary System BIT – Each digit of a binary number
BYTE – Group of 8 bit
WORD – Group of one or more byte
LSB – Least significant bit or smallest value
MSB – Most significant bit or largest value 7 6 5 4 3 2 1
18 BIT WORD
8 BIT WORD
MSB
LSB
BYTE
BYTE
18 BIT WORD

37. PLC : Terminology INPUT is referred by – Ixxyy
OUTPUT is referred by – Qxxyy
TIMER is referred by – T xyyzzzz
FLAGS are referred by – M xxxx
COUNTERS are referred by – C xxxx