PLC and Automation Concepts

• Key concepts discussed include the importance of material properties in engineering applications.

• The role of thermal conductivity, electrical resistance, and mechanical strength in material selection was emphasized.

• Examples of real-world applications, such as aerospace and automotive industries, were provided to illustrate the relevance of these properties.

Lecture Overview

The session provides a comprehensive introduction to Programmable Logic Controllers (PLCs) and their role in modern industrial automation. Students will learn about different types of automation and the fundamental components that interface with PLCs, contributing to streamlined operations.

Recap - Industrial Revolutions

1. Industrial Revolution 1: Steam Power

   • Marked the transition to mechanization of processes, primarily through steam engines, revolutionizing industries such as textiles and mining.

2. Industrial Revolution 2: Electric Power

   • Saw the advent of electricity which enabled mass production and improved efficiency in factories.

3. Industrial Revolution 3: Automation in industry with PLCs

   • This period introduced programmable devices, allowing for greater automation and control over processes.

4. 4th Industrial Revolution:

   • Characterized by significant advances in processing capabilities and widespread connectivity through the Internet of Things (IoT).

   • Features intelligent sensors and the integration of Artificial Intelligence (AI) for enhanced decision-making.

   • Focuses on the implementation of industrial computers which facilitate the connection between humans and machines.

   • Introduces the Paradox of Automation, emphasizing that as systems become more efficient, the human operators’ role becomes increasingly critical.

PLCs Are Not Computers

• Unlike traditional computers, PLCs lack peripherals like mice, keypads, or monitors.

• Their operating systems are tailored specifically for control tasks, not designed for extensive processing, and therefore exhibit limited functionality compared to PCs.

Why Use Programmable Logic Controllers?

• Easy to Program (Ladder Logic): PLCs utilize Ladder Logic, which mimics relay logic and is visually intuitive for engineers.

• Easy to Interface: Established standards facilitate straightforward communication with various automation components.

• Easy to Extend (Modular Design): PLC systems can be expanded easily by adding modules to support additional inputs, outputs, or functions.

• Rugged: Designed to withstand harsh industrial environments, ensuring longevity and reliability.

• Quick Response Time: PLCs provide fast processing speeds, essential for real-time control and monitoring.

• Trusted in Industry: Widely accepted and employed across various sectors, from manufacturing to transportation.

PLC Components

• Power Supply: Provides the necessary electrical energy for operation.

• Processor Unit (CPU): The brain of the PLC, executing the control program.

• Modules:

  • Digital Input/Output Modules: Interface with sensors and actuators to carry out control tasks.

  • Analogue Input/Output Modules: Manage non-binary signals, allowing for more precise control.

• Variable Frequency Drive: Controls motor speed and torque by varying motor input frequency and voltage.

• Programming Device: Used for programming the PLC, often a computer or dedicated handheld device.

Mechatronics Control Loop

Essential components of a feedback loop for automation:

• Mechanical System: The physical apparatus being controlled.

• Microprocessor: Computes and implements control logic.

• D/A (Digital to Analogue) Converter & Amplifier: Converts digital signals to analogue formats for controlling devices.

• Actuators: Mechanics that take action based on control signals.

• Analogue & Digital Sensors: Gather data on system performance and environment.

Control Cabinets

• Houses PLCs, transformers, and fuses, ensuring organized and safe operation.

• Presents risks such as electrocution if not properly handled.

IEC 60529 – Ingress Protection

Solids: (X, 0, 1, 2, 3, 4, 5, 6)

• Protection ratings that detail the ability to keep particles out of devices.

Liquids: (X, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9K*)

• Ratings that describe water resistance capabilities of devices.

Other: (D, F, H, M, S, W)

• Additional classifications for various environmental conditions impacting device operation.

DIN Rails and Cable Covers

• DIN Rail: Standardized metal rail used to mount various electrical devices.

  • Provides a structural framework for modular systems, ensuring easiness in design and adjustments.

PLC Ladder Logic

• Based on relay logic; represented through Ladder Diagrams, fundamental to understanding hardware configurations.

Fundamentals of Ladder Diagrams

• Switches Categories:

  • Momentary: Input activated while pressed, returns to off position once released.

  • Maintained: Activates toggle operation, remaining on until pressed a second time.

Switches Uses

• Fundamental applications include operator input, machine state indication, and safety mechanisms.

Switch Types

• Variety of Pushbuttons:

  • N/O, N/C, maintained mechanisms – tailored for specific operational needs.

• Garded Pushbuttons: Designed to mitigate accidental activation for critical functions (e.g., start, reset).

• Mushroom Push Button: Emergency stop (E-Stop) feature; identifiable through the red mushroom-shaped head designed for quick access.

Indicator Lamps

• Used across control panels to communicate the machine’s state to operators, employing a color-coding system to denote status:

  • Red: Fault conditions or emergencies.

  • Green: Safe operating conditions.

  • Amber: Warning states; conditions that require attention but are not urgent.

  • Others: Display non-critical information.

Relays

• Distinction between mechanical and solid-state relays, each with specific operational characteristics, user bases, and lifecycle expectations.

Next Lecture

• Focus on time delay relays and advanced ladder diagrams.

• Examples and industry-standard symbols will be introduced to enhance understanding of control systems.

More Resources

• Students are encouraged to explore the provided resources for deeper insights into PLCs and automation technology, which will be beneficial in practical applications and later projects.