Programmable Logic Controller (PLC)

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Programmable Logic Controller(PLC)

• Brian Caldwell
• Michael Davis
• November 28th, 2007

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• Definition
• Dedicated computer for rapid processing of simple
  logic instructions in a defined time.
• A solid state control system with a user
  programmable memory that can read input
  conditions and set output conditions to control a
  machine or process.

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Where are they Used?

• PLCs are widely available and used in several,
  in fact almost all automated processes.
• Aerospace
• Automotive Industry
• Entertainment
• Petroleum Industry
• Food, Beverage, and Packaging
• AND EVERYTHING IN-BETWEEN

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Required Technology

• Here is a simplistic view of a PLC system which
  consists of three main components an
  Input/Output Section, the Processor and a
  Programming Unit.

Machine or Process
Programmable Logic Controller
Output Devices
Input Devices
Programming Unit
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Costs

• The most simple and basic PLC will cost around
  50
• The most advanced and sophisticated PLC run
  around 10,000

Http//web4.automationdirect.com/adc/overview/Cata
log
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LADDER LOGIC

• Ladder logic is really just a symbolic
  representation of an electrical circuit. Symbols
  were chosen that actually look similar to
  schematic symbols of electrical devices.
• Three broad Categories
• Contacts (Inputs)
• Coils (Outputs)
• Special Function blocks (timers, countersetc.)

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Sample Problem

• In the figure, will the power on the first wrung
  normally be on or off?
• And for the second wrung?

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Standards limitations

• Standards
• Work in severe conditions (dust, moisture, heat,
  cold, etc)
• Have the facility for extensive input/output
  (I/O) arrangements
• Uninterrupted production
• Long life of equipment
• Limitations
• Limited by the number of input/output ports
• More sophisticated harder to program

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Vendors

• Allen-Bradley
• Mitsubishi Electric
• ABB Ltd.
• Honeywell
• Siemens
• Modicon
• Omron
• General Electric
• Square-D
• Panasonic

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Video Clip

• http//video.google.com/videosearch?qplcapplicat
  ionduration3Ashortnum10so0start0

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REFERENCES

• Dr. Red- Professor Brigham Young University
• http//www.eod.gvsu.edu/jackh/books/plcs/chapters
  /plc_intro.pdf
• http//en.wikipedia.org/wiki/Programmable_logic_co
  ntroller
• http//www.tri-plc.com/applications/m-plc2.htm
• http//www.tri-plc.com/applications.htm
• http//etidweb.tamu.edu/hsieh/LadderLogic/Symbols_
  vers5.5.html
• http//web4.automationdirect.com/adc/Overview/Cata
  log/PLC_Hardware

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Summary

• PLC are used Everywhere
• Controls processes with inputs and outputs
• Cost range for 50 - 10,000
• Ladder logic is commonly used to program PLCs
• Built to perform in severe conditions