PROGRAMMABLE LOGICAL CONTROLLER

1

• PROGRAMMABLE LOGICAL CONTROLLER
• (PLC)
• PRESENTED BY-
• Mrs. Bindu Thakral
• And
• Jaidev Singh

2
Index

• Introduction
• PLC Basics
• PLC and Controls History
• Advantages of PLCs
• PLC Operation
• Comparison to Relay Logic
• Applications
• Conclusion

3
Introduction

• Programmable Logic Control, or PLC as it
• is universally called, is the work horse of
• industrial automation.
• A PLC is used to control, time and
• regulate the sequence.
• Many production processes are controlled using
  PLCs like metal machining sequences, product
  assembly lines and batch chemical processes.

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PLC Basics

• Programmable Logic Controllers (PLCs), also
  referred to as programmable controllers, are in
  the computer family. They are used in commercial
  and industrial applications

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Basic PLC Operation

• PLCs consist of input modules or points, a
  Central Processing Unit (CPU), and output modules
  or points.

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Basic PLC Operation (cont..)

• Pushbuttons (sensors), in this simple example,
  connected to PLC inputs, can be used to start and
  stop a motor connected to a PLC through a motor
  starter (actuator).

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PLC and Controls History

• Large amount of work required connecting wires
• Difficulty with changes or replacements
• Difficulty in finding errors requiringskillful/e
  xperienced work force
• When a problem occurs, hold-up
• time is indefinite, usually long
• Too many moving parts

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Advantages of PLCs

• Number of wires reduced by
• approximately 80
• Fast and easy error
• detection.
• No change in wiring to
• change program
• Needs fewer spare parts
• Cheaper when large number of I/O
  instruments are needed
• Less moving parts
• Compact
• Cost effective for
• installation/maintenance

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Components

• CPU
• Memory Areas
• Circuits to input oroutput data
• Basically, a big box of
• math

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Specific Components

• Input Relays (contacts)
• Output Relays (coils)
• Data Storage

• Internal Utility Relays
• Counters
• Timers

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PLC Operation

• Continually scans
• ladder diagram
• Consists of 3
• important steps

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Plc scan-
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Ladder Logic

• Definition
• Comparison to RelayLogic

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Definition

• One form of drawing
• electrical logic
• schematics
• Very popular for PLCs
• Originally invented for use with relays

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Comparison to Relay Logic

• First used for
• technicians,electricians engineers
• Still first choice for
• most technicians,
• electricians, etc.

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Relay Logic Ladder Logic
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Jog function added to previous relay
circuit 1 component added 3 wires
added
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Two status indicators added 6
additional wires
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Programming

• Basics NO/NC Contacts/Coils
• AND OR Gates
• Timers and Counters
• Building a PLC Ladder LogicProgramming

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Basics

• NO Contact
• NO Coil (Output)
• NC Contact
• NC Coil (Output)

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AND Gate
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OR Gate
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Timers

• Very simple concept,
• it times
• 2 basic types, on-
• delay and off-delay
• Still sends logic as its
• output

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Counters

• Counts number of
• times a lever ispulled, a button ispushed,
  etc.
• 3 types
• Up Counter
• Down Counter
• Up-Down Counter

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Building a PLC/Ladder Logic Program

• To illustrate, will start in relay logic, convert
  to
• ladder logic at end
• Will need to remove/replace some components

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• Relay Logic converted to Ladder Logic Diagram
• Much fewer hard wired components
• Double Pole Pushbutton for Jog switched toSingle
  Pole
• Instead of motor relays, PLC just checks state of
  motor output

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Applications-

• Manufacturing Industry
• Food Industry
• Textile Industry
• Plastics Industry
• And many other

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Conclusion -

• We can conclude that
• A lot of wiring work have been reduced
• Error detection has became fast and easy
• Size has been reduced
• Cost effective for installation/maintenance

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• THANKS
• QA