Dr. D. Y. Patil Institute of Engineering, Management and Research

1. Dr. D. Y. Patil Institute of Engineering, Management and Research Mechatronics - 302050 UNIT –IV PLC Programming Mr. ManojRajale

2. Syllabus PLC Programming • Introduction, Architecture • Ladder Logic programming for different types of logic gates, • Latching, • Timers, Counter, • Practical Examples of Ladder Programming, • Introduction to SCADA system

3. Objectives • Understand key elements of Mechatronics system, representation into block diagram • Understand concept of transfer function, reduction and analysis • Understand principles of sensors, its characteristics, interfacing with DAQ microcontroller • Understand the concept of PLC system and its ladder programming, and significance of PLC systems in industrial application • Understand the system modeling and analysis in time domain and frequency domain. • Understand control actions such as Proportional, derivative and integral and study its significance in industrial applications.

4. Outcomes • Identification of key elements of mechatronics system and its representation in terms of block diagram • Understanding the concept of signal processing and use of interfacing systems such as ADC, DAC, digital I/O • Interfacing of Sensors, Actuators using appropriate DAQ micro-controller • Time and Frequency domain analysis of system model (for control application) • PID control implementation on real time systems • Development of PLC ladder programming and implementation of real life system

5. What is a PLC ? • A Programmable Logic Controller (PLC for short) is simply a special computer device used for automation of electro-mechanical processes in modern factory automation. • A PLC is a miniature industrial grade computer that contains hardware and software – capable of being programmed to perform control functions • Where ever there is a need to control devices, the PLC provides a flexible way to "software" and components together. Evolution of PLC • Manual Control • Hardwire logic (relays, contactors, timers) • LOGIC GATES • PLC

6. Application of PLC- To detect and sort P and Q geometrically different components

7. Examples of Automated Plants

8. Examples of Automated Plants

9. Examples of Automated Plants

10. Before the PLC- The development of the PLC can be compared analogously to the development of the Personal Computer. How were machines and industrial processes controlled before the advent of the PLC? One of the means for controlling machines was through the use of Power Relays Control Relays

11. Control devices: • Rotary drum switch • Limit switch • Electromechanical Counter • Fuses • Control Transformers • Motor Starter • Solenoid Valves • Pneumatic plunger timers etc

12. What are the disadvantages of Relay based control systems? • Hard wired panels / relay logic are very time consuming to implement due to wiring and debugging related issues. • Complexity • Costly • Hardwiring • Troubleshooting problems • Strict Maintenance routine • Not easy to modify , etc

13. Why PLC? • In need of another controller which: • Is faster and operates in real time • Withstands vibrations, temperatures, humidity, noise • Has inbuilt interfacing for inputs and outputs • Is flexible and adaptable (easy to program/re-program) • Easy to troubleshoot and maintain • Consumes less space, requires less wiring, comparatively cheaper

15. Advantages of the PLC- They are re-programmable Complex logics can be easily represented Multiple devices can be embedded in one unit Can easily be scaled up or modified. Smaller physical size than hard-wire solutions. PLCs have integrated diagnostics and override functions. Applications can be immediately documented, duplicated faster and less expensively Connection between switches/output can be modified through software easily. Troubleshooting is Easier and Faster. Ease of Maintenance –less downtime. Easy to develop Programs by offline simulation Less amount of Space Needed

16. Advantages of the PLC-…..cont…. 13. Can withstand severe environmental conditions. 14. Cost effective for controlling complex systems. 15. Computational abilities make possible more sophisticated controls. Disadvantages of the PLC. Most PLCs manufacturers offer only closed architectures for their products . PLC devices are proprietary, which means that parts and from one manufacturer can’t easily be used in combination with parts of another manufacturer, which limits the design and cost options. Subject to the limitations imposed by semiconductor based systems. Setup and training costs could be high

17. PLCs are used in all industries. Manufacturing Process Plants & Systems Machining Packaging Automated Plants Etc

18. Basics of a PLC A small computer with a built-in operating system which monitorinputs and other variable values, make decisions based on a stored program, and controloutputs to automate a process or machine. • Basic parts of a PLC • 1.Power Supply • 2.Processor Module • CPU • Memory • 3.Communication Interface. • 4.I/O Modules • Discrete/Digital Inputs • Analog Inputs • 5.Output Modules

19. Parts of a PLC.

20. Power Supply • A power supply is used to provide power to the PLC and any other modules. Power supplies come in various forms: • Power supply modules that fit into one of the slots in a chassis • External power supplies that mount to the outside of a chassis • Stand alone power supplies that connect to the PLC or I/O through a power cable • Embedded power supplies that come as part of the PLC block.

21. I/O Devices • Input Devices provide inputs to the control system. • In case of discrete-state process control, the inputs are two state specifications such as: • Limit switches – open or closed, • Comparators – high or low, • Push buttons – depressed or not depressed

22. I/O Devices • Output Devices accept outputs from the control system. • In discrete-state process control, the outputs accept only two state commands such as: • Lights: On / OFF, • Motors : Rotating or not rotating, • Solenoids : Engaged or not engaged

23. Input Module • Figure shows the typical wiring to a PLC input module. • The input module examines the state of the physical switches and other input devices and puts their state into a form suitable for the processor. • It is able to accommodate a number of inputs called channels. • If the switch is closed, the input will be 24 V DC, and if open, 0 V DC. The input module converts this into the 1 or 0 state needed by the processor.

24. Input Module • Input Module: Convert real world voltage and currents to signals the PLC can understand. Since there are different types of input devices, there is a wide variety of input modules available, including both digital and analog modules. • Discrete / Digital Module: Use 0 or 1 to depict state • Analog Module: Use numbers to depict state e.g. 30 degree

25. Output Module • Figure shows the typical wiring to the PLC output module. • The Output Module supplies AC power to the external devices such as motors, lights, solenoids, etc. • Internally, the output module accepts a 0 or 1 from the processor, and uses it to turn ON or OFF a device. • An output module can have one or several channels per unit. Each channel is usually provided with an indicator light to show whether the particular channel is being driven ON/OFF.

26. Output Module

27. Processor • The processor is a computer that executes a program to perform the operations specified in a ladder diagram. • It performs arithmetic and logic operations on input variable data and determines the proper state of the output variables.

28. CPU & Memory • CPU: The brain of PLC is the central processing unit (CPU). • It executes the various logic and sequencing functions by operating on the PLC inputs (sensor information) to determine the appropriate output signals for the actuator. • The processor is microprocessor very similar in its construction to those used in personal computers and other data-processing equipment. • Memory: Tied to the CPU is the PLC memory, which contains the program of logic, sequencing, and other input/output operations. • The memory for a programmable logic controller is specified in the same way as for a computer, and may range from 1k to over 48 k(bytes) of storage capacity. • Memory types are ROM, RAM, EPROM

29. Programmable Device • The PLC is programmed by means of a programming device. • The programming device is usually detachable from the PLC cabinet so that it can be shared between different controllers. • Different PLC manufactures provide different devices: • Simple teach pendant-type devices, similar to those used in robotics • PLC programming keyboards and CRT displays.

30. Communication Channel • The CPU uses the: • the data bus for sending data between the constituent elements, • the address bus to send the addresses of locations for accessing stored data • the control bus for signals relating to internal control actions • the system bus is used for communications between the input/output ports and the input/output unit.

31. Communication Channel • The buses are the paths used for communication within the PLC. • The information is transmitted in binary form, i.e. as a group of bits with a bit being a binary digit of 1 or 0, i.e. on/off states. • The term word is used for the group of bits constituting some information. Thus an 8-bit word might be the binary number 00100110. • Each of the bits is communicated simultaneously along its own parallel wire.

32. Communication Channel

33. Requirement of PLC Operation Thestudentneeds: • PC ( Personal Computer ) • PLC’s software ( Simatic Manager) towritetheprogramme in a programminglanguage(LAD). • A physical PLC Unit (With a demo kit) to test the output of theprogrammewrittenonabovelanguage. • Or a Simulator software to test the output of theprogrammewithoutthepresence of a physical PLC Unit.

34. Types of PLCs Single Box Type: (or, as sometimes termed, brick) is commonly used for small programmable controllers and is supplied as an integral compact package complete with power supply, processor, memory, and input/output units. Typically such a PLC might have 6, 8, 12 or 24 inputs and 4, 8 or 16 outputs and a memory which can store some 300 to 1000 instructions. Modular:The modular or the Rack type consists of separate modules for power supply, processor, input module, output module, memory.

35. Types of PLCs Brick Type PLC Rack Type PLC

36. Leading Brands of PLC • AMERICAN: • Allen Bradley • Gould Modicon • Texas Instruments • General Electric • Westinghouse • Cutter Hammer • Square D • EUROPEAN: • Siemens • Klockner & Mouller • Festo • Telemechanique • JAPANESE: • Toshiba • Omron • Fanuc • Mitsubishi

37. A PhysicalCircuitforMaking a Lamp ON by a Switch. HOT line NEUTRAL line

38. Logic Symbols:

40. Physical or Relay Ladder Example

41. Basic logic Functions • AND logic • OR logic • NOT logic • NAND logic • NOR logic • EX-OR logic

42. Ladder Diagram: AND Logic The lamp energizes only if contact A and contact B are simultaneously actuated.

43. Ladder Diagram: OR Logic The lamp energizes if either of contact A or contact B are actuated.

44. Ladder Diagram: NOT Logic The lamp energizes if the contact is not actuated, and de-energizes when the contact is actuated.

45. Ladder Logic Diagrams for AND Gate

46. Ladder Logic Diagrams for OR Gate

47. Ladder Logic Diagrams for NOT Gate

48. Implement a latch to turn ON and OFF a motor using 2 NO push-button switches.

49. (NC)

50. Water Level Control: It’s a single point level control. When the Level is above set point the output pump should be off When the Level is below set point the output pump should be on