Programmable logic controllers (PLCs) are digital electronic devices used to automate industrial processes. A PLC consists of a central processing unit, input/output modules, and a programming device. PLCs scan their program continuously and cyclically to monitor inputs and control outputs. They are programmed using ladder logic to perform functions like timing, counting, and controlling relays. PLCs are used widely in applications like process control, machinery control, and some CNC machine functions. Factors like the number of I/O points, memory, and scan time are considered when selecting a suitable PLC for an application.

1. Programmable Logic Controllers

2. Organization of the Presentation Introduction Components of PLC PLC Functioning PLC Programming Example Problems Applications PLC Selection

3. Introduction

4. PLC Defined Programmable Logic Controller (PLC) is a solid state device designed to perform logic functions. Essentially PLC is an assembly of solid state digital electronic elements designed to make logical decisions and provide outputs

5. Why PLC Relay based Process or Machine Control is expensive and Rigid Need for programmable and reconfigurable control Move towards Flexible Automation

7. Areas of Application Process control Control of Machinery Control of Equipments Certain Aspects of Control in CNC machines and Machining Centers

8. Components of PLC

9. PLC Components Any PLC Has 1. A Central Processing Unit (CPU) Microprocessor based system 2. Input / Output Section (I/O Section) Digital and analog I/O s 3. Programming Device Usually a Computer

10. PLC Components

11. PLC Functioning

12. PLC’s Perform Scans Sequentially and Cyclically

13. Typical PLC Scan Sequence

14. PLC programming

15. Typical Inputs and their Representation

16. Inputs (Continued )

17. Inputs (Continued )

18. Inputs (Continued )

19. Inputs (Continued )

20. An Electro Mechanical Relay

21. Typical Outputs and Their Representation

22. Timers On Delay Timers Off delay timers Retentive Timers

23. Counters Up Counters Down Counters Up Down Counters

24. Relays Internal Relays External Relays Retentive Relays

25. Example Programs

26. Design a Control Program for a Water Pump Motor

27. Product in Position (LS1 Close) Start button on. Conveyer moves product to A (Limit switch LS1 returns to normal) Conveyer moves the Product to A and stops Distance to A counted by encoder (8 Pulses) Waits at A for 10 s Moves again to LS2 and stops Emergency stop Emergency stop resets counter and timer

29. Applications

30. Process Control Electroplating Heat Treatment Powder Coating Chemical Processing Refineries Control of Hydraulic and Pneumatic Circuits

31. Control of Machinery and Equipment Control of Material Handling Equipments like Conveyer Belts Control of Flexible, Automated Assembly Lines Control of Special Purpose Machines like Bottling Machine etc.

32. CNC Machines velocity, displacement and position control is being carried out by exclusive controllers (Hardware interpolators, Closed Loop Controllers etc..) Mostly all ‘M’ codes are transferred to PLC Control PLC Provides one more level of Protection in CNC Machines

33. Machining Centers Automatic Tool Changers Automatic Pallet Changers Overall system protection

34. PLC Selection

35. Criteria for Selecting PLC Number of logical inputs and outputs. Memory Number of special I/O modules Scan Time Communications Software

36. Typical PLC Specification

37. Commercial PLC Manufacturers Omron Electronics Inc. Allen Bradley Aromat GE-Fanuc IDEC Keyence Mitsubishi Modicon Omron Automation Direct Siemens Toshiba

38. PLC Manufacturers Websites Aromat http://www. aromat .com Keyence http://www. keyence .com/ plc /start. htm Toshiba http://www. toshiba .com.au/ plc /index.html

39. Some Interesting PLC Websites http://claymore.gvsu.edu/~jackh/books/plcs/ http://www.plcs.net http://www.geindustrial.com/cwc/solutions ?

40. Reference Programmable Logic Controllers by Frank D Petruzella, McGraw – Hill Books Companey, 1989.

42. Thank You