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Lecture_PLC_Week for industialization in plc
- 1. 1 Programmable Logic Controller (PLC): Prepared By Srilatha Pamuri and Dr.Pengi
- 3. 3 Outline: • Programmable Logic Controllers (introduction, advantages, disadvantages) • PLC Components • PLC Systems of various vendors • PLC Programming Standards and Languages
- 4. 4 PLC is a digital electronic device to control machines and processes. It is invented to replace traditional control panels whose operations depend on push buttons and the electromagnetic logic relays that are based on timers in industrial control systems. PLCs are capable of monitoring the inputs continuously from sensors and producing the output decisions to operate the actuators based on the program Programmable Logic Controllers (PLC) Push buttons Relay PLC
- 5. 5 The manufacturers of PLCs
- 6. 6 Applications of PLC PLCs find widespread use in diverse industrial applications, ranging from • manufacturing and process control • transportation • and energy sectors. They are employed to automate tasks such as machinery control, production processes, and data acquisition, enhancing efficiency, reliability, and safety in industrial operation
- 7. 7 Advantages of PLCs •Flexibility: PLCs allow for easy modification and reprogramming, enabling quick adaptation to changes in the manufacturing process. •Reliability: PLCs are known for their robustness and reliability in harsh industrial environments. •Modularity: The modular design of PLCs facilitates the addition or removal of input and output modules, making it scalable to meet specific application requirements.
- 8. 8 Components of PLC 1. Central Processing Unit (CPU) 2. Input/Output Modules 3. Power Supply 4. Bus system
- 9. 1. Central Processing Unit (CPU) -Arithmetic Logic Unit (ALU) -Program memory -Internal memory of CPU -Internal timers and counters -Flags Components Of PLC
- 10. 10 1. Central Processing Unit (CPU) • CPU performs the task necessary to fulfill the PLC functions. • These tasks include; - Scanning, - I/O bus traffic control - Program execution - Peripheral and External device communication - Special functions or data handling execution and self diagnostics.
- 11. 11 Input and output modules of the PLC allow to connect the sensors and actuators to the system to sense or control the real-time variables such as temperature, pressure flow, etc. 2. Input/Output modules
- 12. 12 2. Input modules These modules act as interface between real-time status of process variable and the CPU. • Analog input module : Typical input to these modules is 4-20 mA, 0-10 V Examples: Pressure, Flow, Level, RTD (Ohm), Thermocouple (mV) • Digital input module : Typical input to these modules is 24 V DC, 115 V AC, 230 V AC Examples: Switches, Pushbuttons, Relays, pump valve on/off status
- 13. 13 2. Output Modules • Analog output module: Typical output from these modules is 4-20 mA, 0- 10V Example: Servo/Proportional Control Valve, Speed, Vibration • Digital output module: Typical output from these modules is 24 V DC, 115 V AC, 230 V AC Example: Solenoid Valves, lamps, Actuators, Pump valve on/off control
- 14. 14 3. Power Supply • The power supply gives the voltage required for electronics module (I/O Logic signals, CPU, memory unit and peripheral devices) of the PLC from the line supply. • The power supply provides isolation necessary to protect the solid state devices from most high voltage line spikes. • As I/O is expanded, some PLC may require additional power supplies in order to maintain proper power levels. Siemens power supply
- 15. 15 4.Interfacing & Communication Module • interfacing modules provide a way to interface modules to the CPU. This module helps in extending the memory addressing capability of the central processing unit • This communication is established by addressing the I/O modules according to the location from CPU module along the bus. Example: if the input module is located in the second slot, then the address must be I2:1.0 (second slot-first channel) • Communication enables efficient communication between central control unit and remote location using different communication field bus system
- 16. 16 Types of PLCs • An integrated or Compact PLC is built by several modules within a single case. Therefore, the I/O capabilities are decided by the manufacturer, but not by the user.
- 17. 17 Types of PLCs • A modular PLC is built with several components that are plugged into a common rack or bus with extendable I/O capabilities. • These modular PLCs come in different sizes with variable power supply, computing capabilities, I/O connectivity, etc.
- 18. 18 Types of PLCs • Small PLC This type of PLC is used for replacing hard-wired relay logics, counters, timers, etc. This PLC I/O module expandability is limited for one or two modules, and it uses logic instruction list or relay ladder language as programming language. • Medium-sized PLC is mostly used PLC in industries which allows Some hundreds of input/ output points are provided by adding additional I/O cards – and, in addition to these – communication module facilities are provided by this PLC.
- 19. 19 Types of PLCs • Large PLCs are used wherein complex process control functions are required. SCADA These PLCs’ capacities are quite higher than the medium PLCs in terms of memory, programming languages, I/O points, and communication modules, and so on. Mostly, these PLCs are used in Supervisory Control and Data Acquisition (SCADA) systems, larger plants, distributed control systems, etc.
- 21. 21 International Standard for Programmable Controllers (IEC 61131-3) Defined Standard Programming Languages Ladder Diagram (LD) – graphically depicts a process with rungs of logic, similar to the relay ladder logic schemes that were replaced by PLCs. Sequential Function Charts (SFC) – flowchart of steps (one or more actions) and transitions (defined conditions) before passing to the next step. Instruction List (IL) – assembler-type, text-based language for building small applications or optimizing complex systems. Functional Block Diagram (FBD) – graphical depiction of process flow using simple and complex building blocks, ranging from analog I/O to closed loop control, algorithms, and diagnostics. Structured Text (ST) – a language developed for IEC to provide high-level syntax using "If" and "Then" statements.
- 22. 22 PLC Working: • Inputs and Outputs are connected to PLC • Controller monitors them according to the program stored in PLC such as Ladder Logic Programing Ladder Logic Diagram
- 23. 23 PLC programing using Ladder Logic Diagram • Wiring diagrams can be very accurate for depicting equipment layout. • All connection wires are shown and connected from one component to another. • Wiring diagrams are used widely by electricians when connecting electrical or electronic equipment and by technicians when maintaining equipment.
- 24. 24 A schematic diagram, is a type of drawing that illustrates the electrical connections and functions of specific circuit arrangements with graphic symbols. • In troubleshooting, electrical schematics are essential because it enables a technician to trace the circuit and its function without regard to the actual location or physical size of the component. PLC programing using Ladder Logic Diagram
- 25. 25 PLC Programming Ladder Logic Ladder logic is basically a program that is represented by a graphical diagram, which is based on a circuit diagram of relay logic
- 26. 26 PLC Programming Ladder Logic •Firstly, two rails are taken, and then a rungs. The rails will work here as a supply of source or current supply. •The left rail is connected to the input switch and the right rail in connected to the output coil. and the switch and coils are connected through a wire. •Switches/inputs should be placed at the left side rail. The number of switch and placement of it can vary depending on the logic is creating.
- 27. 27 Ladder Logic Components Rail and Rung The rails are the two vertical lines that represent the power source to the control circuit. The control circuit voltage is usually rated at 12V-120V depending on the rated values of the loads connected in the circuit The rungs are the horizontal lines that illustrate how the control devices and loads are interconnected to make up the control circuit Concept of NO/NC switch NO(Normally Open) and NC(Normally Closed) are used to represent the state of current flow or contact in PLC ladder logic programming. These terms define whether the switch is open or closed.
- 28. 28 Normally Open •A normally open switch or contact is open when not actuated. •It closes the circuit when pressed or activated, allowing current flow. Normally Closed •Normally closed switch/contact is closed when not actuated. •Activation of the switch opens the circuit, stopping current flow.
- 29. 29 Output/Coil Output devices are such as motor, valve, indicator, lights etc. but in LLD it is represented by vertical line with a label representing the output device.
- 30. 30 Basic Rules of Ladder Diagrams • Inputs (or sensors) can be used in Series as well as Parallel to form a connection • Multiple Loads (or Acutator) or Outputs (or coil) can be used only in Parallel
- 31. 31 • One Input can be used in multiple times in one program • One Output cannot be used multiple times in one program, except in Set/Reset and Latch/ Unlatch functions • Input Address cannot be used as an Output Address • Outputs Address can be used as Inputs Address Basic Rules of Ladder Diagrams
- 32. 32 Single Push button to ON and OFF a Bulb using Ladder Logic Wiring Diagram Ladder Programming
- 33. 33 PLC programing using Ladder Logic Diagram Implementing Logic Functions
- 34. 34 OR Gate
- 35. 35 Exercise : Implementing Logic Functions
- 36. 36 Advantages and Disadvantages of Ladder Logic Advantages •A graphical diagram of electrical relay diagram, which makes it easy to understand. •The visual representation of rungs reduces maintenance. •LLD allow real time monitoring of the system status, which makes it more reliable. •LLDs are modular and can be easily modified or expanded to accommodate changes in the control process. •LLD is Industry accepted Language.
- 37. 37 Disadvantages •LLD can face problem in complex control system as the lack in sophistication of high-level programming language. •it is not suitable for time based operation or sequential problem. •Proper documentation and version control can be challenging. •It is not suitable for data processing task.
- 38. 38 Applications of Ladder Logic •Widely used in manufacturing control to control different machinery to sort item, quality control, packaging etc. •It controls pressure, chemical balance in Water treatment. •It controls HVAC (Heating, Ventilation, and Air Conditioning) in in buildings to ensure temperature, ventilation and energy efficiency. •They often used in traffic control to maintain the time and sequence of traffic light. •To control Elevator LLD can be used for floor selection, door opening and closing etc. •Ladder logic is also used in food packaging and beverage processing. •It controls various aspects of chemical manufacturing, including temperature, pressure, mixing, and safety systems •LLD play some crucial role to store renewable energy in system
- 39. 39 Instruction List (IL) • If we’ve programmed microcontrollers with assembly language, IL will feel familiar. • One of the simplest PLC programming languages (at least in theory), IL moves step by step and makes the entry of a series of simple mathematical functions easy. • Just like assembly, IL consists of many lines of codes, one line for exactly one operation. These operations can have three modifiers.
- 40. 40 Function Block Diagrams (FBD) Function Block Diagrams have inputs and outputs, and also contain functions, function blocks, conversions etc. Each Function Block Diagram uses its functions, function blocks etc to determine outputs based on the values for its inputs. By creating connections between the various function block components, you can create complex behavior logic. The following Function Block Diagram is used to control a pump in the water industry:
- 41. 41 Summary: • Programmable Logic Controllers (introduction, advantages, disadvantages) • PLC Components • PLC Systems of various vendors • PLC Programming Standards and Languages