This document provides an overview of programmable logic controllers (PLCs). It discusses the basic architecture of PLCs, including their input and output modules. The document also covers the advantages of PLCs over traditional relay-based control systems. Additionally, it examines PLC programming standards like ladder logic and the evolution of PLC architecture over time. Examples are provided to demonstrate basic PLC programming concepts like timers, counters, and logic gates using ladder diagrams.

1. A
SEMINAR
ON
[PROGRAMABLE LOGIC CONTROLLER]
Submitted for partial fulfillment of the award of
BACHELOR OF TECHNOLOGY
Degree
In
ELECTRONICS & COMMUNICATION ENGINEERING
By
SATYAM SHIVANSH
(1614331083)
ECE Department, IMS Engineering College, Ghaziabad
Dr. A.P.J. ABDUL KALAM TECHNICAL UNIVERSITY, LUCKNOW
September 2019

2. PROGRAMMABLE
LOGIC
CONTROLLER

3. Contents
• What Is PLC?
• Architecture Of PLC
• Advantage and Disadvantage of PLC
• Working Of PLC
• PLC Input / Output Module
• PLC Cycle And Signal Flow
• PLC Architecture Evolution
• PLC Programing Standards
• Ladder Diagram
• Basic Symbol Used In Ladder Programing
• PLC Timer And Counter Function
• Examples

4. PLC(Programmable Logic
Controller)
• It ismicroprocessor basedsolidstate/industrial computer that
performdiscreteor sequentiallogic.
• It wasdevelopedto replacemechanical relays,timers, counters.
• TheearlyPLC’swereusedto reducethe changeover
time, wiring/re-wiring.
• ThePLCprogramming proceduresreplacedthe rewiring apanel
full of wires,relays,timers, countersetc.

5. Architecture of aPLC
• BLOCKDIAGRAM
INPUT
DEVICES
PLC
OUTPUT
DEVICES
POWER
SUPPY
MEMORY INTERFACE
(24VDC,
120VAC)
(Toggle or Push
buttons, proximity
or pressure
sensors)
(Displays&
Monitors)
(External memory
module)
(SCADAorHMI)

6. 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 Controllers

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

8. Working
• Source mode: +vesupply is given to the PLC.
• Sink mode: -ve supply is given to the PLC.
• The sink and source modes mainly define the way in which the I/O
is connected to the I/O of the PLC.

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. 120 V acL1 L2
L2
L1
1
2
3
4
PB
input
field
device
Input module
terminal board
Input status
indicator
PLC : Input module

11.  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
PLC : Output module

12. 120 V acL1 L2
L2
L1
1
2
3
4
Output status
indicator
Output field
device
Module blown
Fuse indicator
Output module
PLC : Output module

13. PLC Cycle
 Sense the Input
 Process the Logic
 Give Output
Outputs
Machine OR Process
Programmable
controller
Inputs

14. PLC 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

15. PLC 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

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

17. PLC 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

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

19. ABB Programmable Logic Controller

20. PLC Programming Standards
 Ladder Diagram
 Statement List
 Instruction List
 Function Block Diagram
 Sequential Function Chart
 Structured Text

21. Ladder Diagram
• Ladder diagram, better known as ladder
logic, is a programming language used to
program PLCs (programmable logic controllers
). ... Contacts are placed in series to represent
AND logic and in parallel when using OR logic.
As with real relays, there are normally open
contacts and normally closed contacts

22. Basic symbols Used In Ladder Programing :

23. PLC TIMER/COUNTER FUNCTION

24. Examples
Set And Reset Output Holding Circuit

25. Logic Gates Using Ladder Programing

26. THANKYOU !!!