ppt on PLC

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ppt on PLC

  1. 1. Presented By Veenita Rao More B.Tech (EC) III yr Banasthali University (Programmable Logic Controller) Banasthali University
  2. 2. Contents What is PLC? History of PLC Major components of PLC Operational sequence of PLC Ladder logic Example of starting and stopping of a motor Advantages Disadvantages Application
  3. 3. What is PLC? PLC is a digital computer designed for multiple inputs and output arrangements, extended temperature ranges, immunity to electrical noise, and resistance to vibration and impact. A PLC is an example of a real time system.
  4. 4. PLC was introduced in late 1960’s First commercial & successful Programmable Logic Controllers was designed and developed by Modicon as a relay replacer for General Motors. Earlier, it was a machine with thousands of electronic parts. Later ,in late 1970’s,the microprocessor became reality & greatly enhanced the role of PLC permitting it to evolve form simply relay to the sophisticated system as it is today.
  5. 5. 5 Major Components of a Common PLC PROCESSOR POWER SUPPLY I M N O P D U U T L E O M U O T D P U U L T E PROGRAMMING DEVICE From SENSORS Pushbuttons, contacts, limit switches, etc. To OUTPUT Solenoids, contactors, alarms etc.
  6. 6. 6 Major Components of a Common PLC POWER SUPPLY Provides the voltage needed to run the primary PLC components I/O MODULES Provides signal conversion and isolation between the internal logic- level signals inside the PLC and the field’s high level signal. PROCESSOR Provides intelligence to command and govern the activities of the entire PLC systems. PROGRAMMING DEVICE Used to enter the desired program that will determine the sequence of operation and control of process equipment or driven machine.
  7. 7. PLC operation sequence 1)Self test: Testing of its own hardware and software for faults. 2)Input scan: If there are no problems, PLC will copy all the inputs and copy their values into memory. 3)Logic solve/scan: Using inputs, the ladder logic program is solved once and outputs are updated. 4)Output scan: While solving logic the output values are updated only in memory when ladder scan is done, the outputs will be updated using temporary values in memory. Self test Input scan Logic scan Output scan
  8. 8. Programming Languages of PLC Most common languages encountered in PLC programming are: 1) Ladder Logic 2) Functional Block Diagram 3) Sequential Function Chart 4) Boolean mnemonics
  9. 9. Ladder Logic  The ladder logic is the oldest programming language for PLC.  It is well suited to express Combinational logic. The main ladder logic symbols represent the elements : make contact break contact relay coil
  10. 10. A B Logic(Y) OFF OFF ON ON OFF ON OFF ON OFF OFF OFF ON AND Gate A B Y A B Logic(Y) OFF OFF ON ON OFF ON OFF ON OFF ON ON ON OR Gate A B Y
  11. 11. NOR Gate A B Y A B Logic(Y) OFF OFF ON ON OFF ON OFF ON ON ON ON OFF A B Logic(Y) OFF OFF ON ON OFF ON OFF ON ON OFF OFF OFF NAND Gate B Y A
  12. 12. Block diagram of a PLC Outputs LEDs Inputs
  13. 13. Ladder Logic Program for Start/Stop of Motor : X2X1 Y1 Y1
  14. 14. Programming PLC:
  15. 15. Starting of Motor:
  16. 16. Continuous Running of motor when Start Button is released:
  17. 17. To Stop the Motor :
  18. 18.  Reliability.  Flexibility in programming and reprogramming.  Cost effective for controlling complex systems.  Small physical size, shorter project time.  High speed of operation.  Ability to communicate with computer systems in the plant.  Ease of maintenance /troubleshooting.  Reduced space.  Energy saving.
  19. 19. Disadvantages of PLCs PLC devices are proprietary it means that part or software of one manufacturer can’t be used in combination with parts of another manufacturer. Limited design and cost option Fixed Circuit Operations. PLCs manufacturers offer only closed architectures.
  20. 20. Wherever automation is desired the PLCs are best suited to meet the task. Few examples of industries where PLCs are used : 1) Robots manufacturing and control 2) Car park control 3) Train control station system 4) Food processing 5) Materials handling 6)Machine tools 7)Conveyer system etc.
  21. 21. Thank You!!!

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