webinar 1 sesson 2

Introduction

  • Warm greetings from the presenter at 7:30 local time in South Africa, 18th September 2024.

  • Focus of today's session: Allen Bradley range of PLCs, specifically the ControlLogix 5,000.

  • Phasing out older models (500) due to software unavailability.

  • Interactive session encouraged; questions can be asked either via microphone or chat box.

Course Structure

  • Course code: CAL - excluding SCADA section, focusing solely on Allen Bradley PLCs.

  • Another course (CAU) covers PLCs and SCADA.

  • Aim: Align participants with Allen Bradley's way of thinking.

  • Plan for 7-8 practical demonstrations during the session.

Software Tools

  • Introduction to TLP Logix Pro software for demonstrations, no installation required for participants.

  • Remote labs will be used in future sessions for practical work.

  • Participants encouraged to use their own Allen Bradley PLC software if available.

  • Optional software (The Learning Pit) available for 14-day trial.

  • Reminder: Don't purchase the software.

PLC Basics

  • Overview of the ControlLogix system architecture:

    • Instruments in the field communicate with the PLC controller.

    • Control the final control elements (e.g., variable speed drives).

  • Example of a control loop: measuring tank levels using transmitters connected to indicators and controllers.

Components of a PLC System

  • PLC Rack Setup:

    • Power supply on the left.

    • CPU (central processing unit) next, housing the main brains of the system, followed by I/O cards.

  • Types of I/O:

    • Digital inputs, digital outputs, analog inputs, and analog outputs.

  • Signal Types:

    • Example of level transmitter sending a 4-20 mA signal into the PLC through the analog input card.

Functionality of PLCs

  • PLCs are unique due to their adaptability and high-speed response times.

  • Used globally for tasks such as monitoring and controlling various processes.

  • Programs can be modified without changing physical wiring.

  • Reliability and cost-effectiveness are key advantages.

Communication Systems

  • Discussion on distributed control systems versus SCADA systems.

  • Remote terminal units (RTUs) are essentially PLCs in the field, programmed for operational tasks.

Practical Demonstration 1: Basic Light Control

  • Demonstration of creating a simple electrical circuit with a switch and a light.

  • Transfer of the circuit diagram into a PLC program using Allen Bradley's approach (examine if opened contacts).

  • **Simulation Process: **

    • Setting up IO simulator with digital inputs and outputs.

    • Clear coding processes for practical understanding: Example of a normally open contact controlling a light.

Practical Demonstration 2: Normally Closed Contact

  • Similar setup with a normally closed contact resulting in opposite behavior:

    • Light turns off when the button is pressed.

  • Emphasis on programming practices for different contacts.

Importance of the Key Switch

  • Operators must be trained about the key switch’s function to prevent accidental shut down of systems.

Programmable Logic Controller (PLC) Components

  • CPU Functionality:

    • Executes control programs, maintains memory, requires backup batteries for program retention.

  • Types of Inputs/Outputs:

    • Digital/discrete signals represent present/absent conditions.

    • Analog inputs/outputs vary signals (e.g., from sensors across a measurable range).

Practical Demonstration 3: Start-Stop Circuit

  • Construction of a start-stop circuit managing motor control.

  • Demonstration of using a retained or latching contacts within the program to keep a motor running.

  • Interactive programming description for effectiveness and clarity in writing PLC programs.

Language and Memory in PLCs

  • Programming Languages Supported by Allen Bradley:

    • Ladder logic, function block, sequential function chart, and structured text (but not instruction list – as less utilized).

  • Importance of tags in Logix 5000 versus traditional addressing methods.

Practical Demonstration 4: Timer Implementations

  • Discussion of timers:

    • On-delay timer provides output after a set duration.

    • Off-delay timer continues output for set time after a switch action.

  • Programming examples of timers with specific timing configurations and simulations.

Final Demonstration: Counter Operations

  • Construction of an up counter:

    • Triggers to count inputs and reset functionalities.

    • Differences identified between various counter operations in PLCs.

Conclusion

  • Recap of the demonstrations conducted.

  • Encouragement for continuous engagement and practice with Allen Bradley PLC programming.

  • Reminder about utilizing available recordings for review.

  • Q&A session for final clarification and participant engagement.