This document provides an overview of programmable logic controllers (PLCs), including their components, programming methods, and applications. It discusses PLC architecture, describing the CPU, I/O modules, memory, and other components. Common programming languages like ladder logic and structured text are outlined, as well as different programming methods such as offline, online, and computer-based programming. Applications of PLCs in various industries are highlighted. Troubleshooting techniques and advanced PLC topics like networking, protocols, and safety systems are also summarized.

1. UNIVERSITY OF ENGINEERING AND TECHNOLOGY
PESHAWAR

2. PROGRAMMABLE LOGIC
CONTROLLER (PLC)
It is an industrial computer control system

3. TABLE OF CONTENTS
• Programming languages to
program PLC
• Difference b/w languages
• Advantages and disadvantages of
languages
PROGRAMMING
LANGUAGES
03 04
01 02
• What are PLC’S
• How they work
• Applications
INTRODUCTION
• Different methods to program PLC
• Advantages anddisadvantages of
methods
• Difference b/w methods
PROGRAMMING
METHODS
• Components of PLC
• Function Of PLC
• Components connection
PLC ARCHITECTURE

4. TABLE OF CONTENTS
• Networking
• Communication protocols
• Motion control
• Safety system
ADVANCE TOPICS
07
05 06
• What are I/O modules
• Their interference with
outside world
• Common types of I/O modules
I/O MODULES
• How to troubleshoot PLC
• Common problems in PLC
• Tools used to troubleshoot
PLC
TROUBLESHOOTING

5. INTRODUCTION
What are PLC’s?
PLCs (Programmable Logic Controllers) are specialized
digital computers used to control and automate
industrial processes. They are commonly used in
manufacturing plants, machinery, and various
industrial applications.
01

6. How do they work?
1. Input Scan: PLC reads sensor and device states,
updating internal memory.
2. Program Execution: CPU executes control program,
processing inputs, performing calculations, and making
decisions.
3. Output Update: CPU updates output values based on
control instructions.
4. Output Scan: PLC updates connected devices and
actuators based on output values.
5. Repeat: The process repeats continuously to maintain
real-time control.
02

7. 03
Applications of PLC’S:
1. Industrial Automation: PLCs are used in industrial
automation for controlling manufacturing processes,
assembly lines, and machinery.
2. Transportation Systems: PLCs control traffic signals,
railway systems, airport baggage handling, and
automated material handling in logistics and warehouses.
3. Food and Beverage Industry: PLCs automate processes in
food processing, packaging, bottling.
4. Automotive Industry: PLCs control assembly lines, robotic
systems, and quality control processes in automobile
manufacturing.
5. Pharmaceuticals: PLCs are utilized in pharmaceutical
manufacturing for precise control of dosage, filling,
labeling, and packaging operations.

8. PLC ARCHETECTURE
Components of a PLC and Their Functions:
1. CPU: Executes the control program and coordinates PLC
operation.
2. I/O Modules: Interface between PLC and external
devices, handling input and output signals.
3. Memory: Stores the control program and data variables
used in the program.
4. Power Supply: Provides electrical power for the PLC
system.
5. Programming Device/Software: Enables
programming, configuration, and monitoring of the PLC.
6. Communication Ports: Facilitate connectivity with
other devices or networks. 04

9. PLC ARCHETECTURE
Connection of PLC Components:
1. Input Devices: Connected to input modules, supplying real-time data.
2. Output Devices: Connected to output modules, receiving control signals.
3. Input/Output Modules: Connected to the CPU through communication
buses or backplanes.
4. CPU and Memory: CPU processes inputs, executes control program, and
accesses memory.
5. Programming Device: Connected to PLC for programming and
configuration.
6. Power Supply: Provides electrical power to ensure proper functioning.
05

10. PROGRAM LANGUAGES
Programming Languages for PLCs their advantages and
disadvantages:
1. Ladder Logic (LD): Graphical language resembling relay circuits,
intuitive for sequential control. Advantages: Easy visualization,
suited for electrical engineers. Disadvantages: Complexity for
larger programs, limited for complex calculations.
2. Structured Text (ST): High-level language like Pascal or C, offers
flexibility and modularity. Advantages: Supports complex
calculations, algorithmic control. Disadvantages: Requires higher
programming skills, less intuitive for ladder logic users.
06

11. PROGRAM LANGUAGES
Programming Languages for PLCs their advantages and
disadvantages:
3. Function Block Diagram (FBD): Graphical language using blocks for
functions and interconnections. Advantages: Modularity, code reuse,
suitable for complex control systems. Disadvantages: Less intuitive for
beginners, requires understanding of control systems.
4. Instruction List (IL): Low-level language resembling assembly code.
Advantages: Precise control, efficient for critical sections, time-critical
applications. Disadvantages: Challenging to read and understand,
requires knowledge of PLC internals.
07

12. PROGRAMMING METHODS
Programming methods advantages and disadvantages and
difference:
1. Offline Programming: Develop and test the program separately,
then transfer it to the PLC. Advantages: No interruption to live
systems, allows for debugging. Disadvantages: Synchronization
required, lacks real-time adjustments.
2. Online Programming: Directly program the PLC while it is connected
and running. Advantages: Real-time adjustments, immediate
response, flexibility. Disadvantages: Potential for disruptions, safety
precautions needed.
08

13. PROGRAMMING METHODS
Programming methods advantages and disadvantages:
3. Handheld Programmers: Portable devices for on-site
programming and troubleshooting. Advantages: Portability,
convenience. Disadvantages: Limited functionality, simplified
interface.
4. Computer-Based Programming Software: Use specialized
software on a computer to create, edit, and download programs.
Advantages: Comprehensive capabilities, simulation and
debugging tools, user-friendly interface. Disadvantages: Requires
a computer, learning curve for beginners. 09

14. PROGRAMMING METHODS
Differences:
1. Offline programming: Separate development, no real-time
adjustments.
2. Online programming: Direct programming, real-time
adjustments possible.
3. Handheld programmers: On-site portability, limited
functionality.
4. Computer-based software: Extensive capabilities, simulation,
and user-friendly interface.
10

15. I/O MODULE
I/O modules in PLC:
• I/O modules are devices used in PLC systems to interface
with external devices.
• They receive signals from sensors and switches (inputs)
and convert them for processing by the PLC.
• They also receive signals from the PLC and control
external devices such as motors and valves (outputs).
11

16. I/O MODULE
Common types of I/O modules:
1. Digital Input Modules: Receive discrete on/off signals from
devices like switches and sensors.
2. Digital Output Modules: Provide on/off signals to control
external devices like relays and solenoids.
3. Analog Input Modules: Convert continuous analog signals (e.g.,
voltage, current) from sensors into digital signals for the PLC.
4. Analog Output Modules: Convert digital signals from the PLC
into continuous analog signals to control devices like variable
frequency drives.
5. Specialty Modules: Include high-speed input modules,
communication modules, and motion control modules for
specific applications. 12

17. TROUBLESHOOTING
Troubleshoot PLC system:
1. Identify symptoms
2. Check power supply
3. Review program logic
4. Monitor inputs and
outputs
5. Inspect wiring and
connections
6. Analyze faulty outputs
7. Use debugging tools and
PLC diagnostics
8. Refer to documentation
and manuals.
13
Common problems in PLC systems:
1. Wiring and connection issues
2. Power supply problems
3. Programming errors
4. Sensor and actuator problems
5. Communication failures.
Tools for PLC system
troubleshooting:
1. Multimeter
2. Oscilloscope
3. Programming software
4. Logic analyzer
5. PLC diagnostic tools

18. ADVANCE TOPICS IN PLC
• PLC Networking: PLCs can connect and communicate with other
devices on a network, enabling data exchange and integration in
industrial automation.
• Communication Protocols: Standardized methods for data
exchange between devices, such as Modbus, Profibus, and
Ethernet/IP, determine the rules for transmitting and interpreting
data in PLC systems.
• Motion Control: PLCs enable precise control of motion devices like
motors and actuators, executing speed, position, and trajectory
commands for applications such as robotics and packaging systems.
• Safety Systems: PLCs integrate safety functionality to ensure safe
operation and protect personnel and equipment, implementing
safety functions like emergency stop circuits and safety monitoring.
14

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