tự động hóa càng ngày càng phát triển , và tiêu biểu cho tự động hóa là công nghệ PLC. đây là tài liệu nói về PLC bằng tiếng anh chuẩn, sẽ mang đến cho bạn đọc những khái niệm cơ bản về PLC theo tiêu chuẩn quốc tế, nên sẽ được trình bày bằng tiếng anh.
Faculty of Electrical and Electronics Engineering Department of Automation Control Chapter 1: Introduction to PLC Lecturer: Nguyen Tan Doi Programmable Logic Controller 11/09/2016 Objectives Upon completion of this chapter, students will be able to: Describe the components of a PLC Understand the PLC specifications Apply PLC to industrial systems Convert a hardwired system to a PLC system Show the areas can be use PLC Programmable Logic Controller 11/09/2016 Content Introduction to PLC Types of Memory Digital and Analog PLC Applications Question and Answer Programmable Logic Controller 11/09/2016 Introduction to PLC Definition PLC What is CONTROL History of PLC Advantages of PLC Comparision PLC operation PLC signal flow Components of a PLC Programmable Logic Controller 11/09/2016 Definition of PLC What is a PLC? Programmable Logic Controller Solid-state control system Control the devices based on user program Definition of PLC Digital electronic device Use a programmble memory to store the instructions and to implement the specific functions A computer designed to work in industrial enviroment Programmable Logic Controller 11/09/2016 Definition of PLC Programmable Logic Controller 11/09/2016 What is CONTROL The proccess in a system One or more input variables influence the other variables Programmable Logic Controller 11/09/2016 History of PLC In late 1960s, General Motors was interested in the computer application to replace the hardwired systems Bedford Associates –Modicon and Allen Bradley responded to General Motors The name given was “Programmable Controllers” or PC Programmable Logic Controller or PLC was a registered trademark of the Allen Bradley Later, PC was used for “Personal Computer” and PLC for “Programmable Controller” Programmable Logic Controller 11/09/2016 Advantages of PLC Less wiring Wiring between devices and relay contacts are done in the PLC program Easier and faster to make changes Trouble shooting aids make programming easier and reduce downtime Reliable components make these likely to operate for years before failure Programmable Logic Controller 11/09/2016 Comparision 10 Hardwired system PLC system The functions are determined by the physical wiring The functions are determined by the program in memory Changing the functions means changing the wiring The functions can be changed simply by changing the program Can be contact circuits (relay, contactor) Consist of a control device which or logic circuits (electronic devices) connected to sensors and actuators Programmable Logic Controller 11/09/2016 Results of Operation PLC 34 Programmable Logic Controller 11/09/2016 Digital and Analog 35 Analog representation: a quantity is represented by a continuous variables, proportional indicator Analog signals are expressed by 0-4mA, 0-5V/10V, … Analog signals are easily converted from physical quantities Digital representaton: the quantities are represented not by continuous variable but by symbols called Digits Digital signals are expressed by and Digital signals are made by electronic circuit Analog = Continuous Digital = Discrete Programmable Logic Controller 11/09/2016 Digital and Analog modules 36 Digital Input (DI) modules adapt digital signals from, e.g, proximity sensors Digital Output (DO) modules convert the internal signal level of PLC into digital process signals, e.g, relays Analog Input (AI) modules adapt analog process signals, e.g, from transducers, convert them to digital values ADC Analog Output (AO) modules convert internal digital values of the PLC to analog process signals e.g temperature controller DAC Programmable Logic Controller 11/09/2016 Digital and Analog modules 37 Digital modules use only a single bit to represent the state of the device For example, a switch is either open or closed Therefore, the bit is either a (switch is open) or a (switch is closed) Analog modules use words to represent the state of a device An analog signal represents a value For example, the temperature could be 0, …, 90, etc degrees Analog modules use a value, such as 0, …, 14000, rather than a or to represent the state of the device Programmable Logic Controller 11/09/2016 PLC Applications 38 o Hardwired arrays of relays were used to control the operation of heavy machines that contain motors and other high power devices o Originally PLCs were used to substitute the switching relay networks used in industrial applications, o Now they can be used implement other tasks such as timing, counting, calculating, comparing and processing of analog signals Programmable Logic Controller 11/09/2016 39 Programmable Logic Controller 11/09/2016 40 Programmable Logic Controller 11/09/2016 41 Programmable Logic Controller 11/09/2016 42 Programmable Logic Controller 11/09/2016 Question and Answer 43 Programmable Logic Controller 11/09/2016 Question and Answer 44 Programmable Logic Controller 11/09/2016 Question and Answer 45 Programmable Logic Controller 11/09/2016 Problems 46 Sketch the connections needed for Inputs and ouputs: Programmable Logic Controller 11/09/2016 Problems 47 Programmable Logic Controller 11/09/2016 Problems 48 Programmable Logic Controller 11/09/2016 [...]... slides into a chassis with other modules PLC that plugs into adjacent modules to form a backplane, no chassis repuired PLC with the modules built in, comes as one block Programmable Logic Controller 11/09/2016 Chassis and Backplane 25 Programmable Logic Controller 11/09/2016 Components of PLC 26 Power Supply A power supply is needed to provide power to the PLC and any other modules Power supplies... 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 Programmable Logic Controller 11/09/2016 Components of PLC 27 Programming sofware Software that runs on a PC, to configure and program PLCs Different... Valves Motor Starters Solenoids Actuators Control Relays Horns & Alarms Stack Lights Fans Counter Pumps Printers Programmable Logic Controller 11/09/2016 Components of PLC 24 Chassis and backplane All PLCs need some method of communicating between the controller and Input/Output/communications modules Three ways used to accomplish these communications: Modular PLC: CPU slides into a chassis... a PLC work 12 24 VDC Sensors Power Supply Program Memory Processor Input modules Output modules Actuators GND The sensors are connected to the Input modules The Processor excutes the program in memory and scan the individual input for presence or absence of voltage Depend on the state of inputs, the processor directs voltage to Ouput modules The actuators are witched ON or OFF according to. .. adjust a motor’s speed, or temperature, … Programmable Logic Controller 11/09/2016 Components of PLC 17 Input/ Output Modules Input modules interface directly to devices such as switches and sensors Input modules convert different types of electrical signals such as, 24V/0-10V/4-20mA, to signals which the controller can understand Output modules take a signal from CPU and convert it to a signal... proximity sensors Digital Output (DO) modules convert the internal signal level of PLC into digital process signals, e.g, relays Analog Input (AI) modules adapt analog process signals, e.g, from transducers, convert them to digital values ADC Analog Output (AO) modules convert internal digital values of the PLC to analog process signals e.g temperature controller DAC Programmable Logic Controller... 11/09/2016 Components of PLC 15 Programmable Logic Controller 11/09/2016 Components of PLC 16 CPU-Central Processing Unit The CPU reads the input signal states, processes the user program and controls the outputs The CPU provides internal memory, timers and counters CPU stores the user program and data in its memory Executes the user program Commands influence outputs to change state based on.. .PLC Operation 11 While a PLC is running, there are 4 steps repeated continueously: 1) Self test: Testing of its own hardware and Self Test software for faults 2) Input scan: Scan all inputs, PLC will copy all Input the inputs and copy their values into memory Scan 3) Program excution: The logic program is solved Program Excution... ROM / PROM Alterable UV erasable EPROM / REPROM Semiconductor RAM Programmable Logic Controller Electrically erasable EEPROM / EAPROM Semiconductor EEPROM / EAPROM 11/09/2016 PLC Memory 29 Programmable Logic Controller 11/09/2016 Input Table 30 Programmable Logic Controller 11/09/2016 Output Table 31 Programmable Logic Controller 11/09/2016 Storage Area 32 Programmable Logic Controller 11/09/2016 Example... Logic Controller 11/09/2016 PLC signal flow 13 Input Module Processor Memory Output Modules Data Output Input Image Table Image Table I:0/6 O:0/7 I:0/6 O:0/7 I:1/4 O:1/5 Input Devices Output Devices Ladder Program I:1/4 I:0/6 O:0/7 I:1/4 O:1/5 O:1/5 Programming Terminal Programmable Logic Controller 11/09/2016 Components of PLC 14 There are five components in a PLC The PLC processor, or CPU I/O