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ECE 4951

ECE 4951. Lecture 1: Programmable Logic Controllers. Course Objectives. ABET OBJECTIVES WORK WITH INDUSTRY TO DEVELOP: Scope and Specification Budget Design DELIVER WRITTEN AND ORAL REPORTS AT UMD. PROJECTS. MP#1: Hydro Automation

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ECE 4951

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  1. ECE 4951 Lecture 1: Programmable Logic Controllers

  2. Course Objectives • ABET OBJECTIVES • WORK WITH INDUSTRY TO DEVELOP: • Scope and Specification • Budget • Design • DELIVER WRITTEN AND ORAL REPORTS AT UMD

  3. PROJECTS • MP#1: Hydro Automation • Develop a PLC based control automation scheme for Winton Hydro (Ely, MN) • MP#2: Power Plant Educational Demo • Develop a PLC based control and data acquisition system for a model power plant • UMD#1: Automated Data Acquisition for Medical School • Develop hardware and software to broadcast metering data from Med. School to ethernet and collect for display and archiving

  4. Skill Sets • MP#1: • PLC programming • Ability to learn MP control Schemes • Ability to work a fast track job • MP#2: • PLC programming • Mechanical ability • Ability to visualize and implement an open-ended spec • UMD#1: • Internet protocols • Software development • Data base development

  5. PLC’s Are ... • Similar to a Microcontroller: • Microprocessor Based • Onboard Memory for Storing Programs • Special Programming Language: Ladder Logic • Input/Output Ports

  6. PLC’s Are... • Dissimilar to Microcontrollers: • Intended for Industrial Applications (High Power) • I/O Designed to interface with Control Relays • Emphasis on Maximum Reliability

  7. PLC’s • Widely Applied in Every Industry • Were Developed to Simplify the Implementation of Control Automation Systems in Plants and Assembly Lines • Designed to Minimize the Number of Control Relays in a Process and Maximize the Ways Relays can be Used • First Applied to Automobile Industry in the Late 1960’s • Flexible, Reliable and Low Cost

  8. PLC Components

  9. I/O Modules • Input Modules: Input Signals can be AC or DC, Analog or Digital • Output Modules: Outputs are either AC or DC Analog Signals (Although it is possible to ‘Construct’ Digital Outputs) • Modern PLC’s have Expansion Ports to Increase the Number of Available Inputs and Outputs

  10. Examples of I/O Signals • Inputs: • Pushbutton (Energizing or Grounding an Input) • Relay Contact Output • DC Voltage Level • Digital Logic Signal (+5V or 0 V, etc) • Outputs: • 24 V ac • 120 V ac • 120 Vdc • etcetera

  11. PLC’s Use Ladder Logic • Ladder Logic Diagrams Provide a Method to Symbolically Show How Relay Control Schemes are Implemented • Relay Contacts and Coils, Inputs and Outputs lie on “Rungs” Between the Positive and Ground Rails

  12. Example of Ladder Diagram

  13. Relays • In General, Relays Transform a Control Signal into a Control Action • Relays Provide: • Isolation Between Input and Output • Leverage (Small Signal Can Control Large Action) • Automation (Minimize Human Interaction with a Control Process)

  14. Relay Components

  15. Basic Relay Symbols

  16. Relay Applications • Relays can be Designed to Perform Many Functions • Detect Out of Limit Conditions on Voltages and Currents • Start Motors • Prevent Motors from Over Heating • Control Assembly Lines • Adjust Lighting

  17. References • Skvarenina/DeWitt, Electrical Power and Controls, Pearson-Prentice Hall, 2004

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