- source:ELAND CNC Machining
4% ) , chemical / pharmacy (14.
6% ) , metal / mine (11.
5% ) , pulp / papermaking (11.
3% ) wait for an industry. To make each abecedarian understands PLC conveniently more, the basic knowledge such as the article development to PLC, basic structure, configuration, application makes one brief introduction, with period to everybody the netizen is helped somewhat. One, the development course of PLC is in industrial production process, many switch measures sequence control, it has ordinal action according to logistic condition, undertake interlinking protective behavioral control according to logistic relation, the data that reachs many disperse capacity is collected. On the tradition, these functions come true through pneumatic or electric control system. 1968 American GM (general motors) the company puts forward to replace afterwards the requirement of electric control equipment, the 2nd year, development of American number company went to be based on the control equipment of integrated circuit and electronic technology, the method that uses a program to change first applies at electric control, this is generation but program controller, weigh ProgrammableController (PC) . PC (abbreviation PC) after development rises, to go to the lavatory, also can make up the functional characteristic of Cheng controller for report, but program controller denominate is ProgrammableLogicController (PLC) , now, still often PLC abbreviation PC. The definition of PLC has a lot of planting. International Electrotechnical Committee (IEC) it is to the definition of PLC: Can making up Cheng controller is the electronic system that operation of a kind of number operates, design to application falls in industrial environment only. It is used but of program put store implement, use interior to put lay aside to implement the directive of the operation such as logistic operation, sequence control, time, computation and arithmetic manipulation, carry a number, simulative input and output, control the machinery of all sorts of types or manufacturing process. But program controller reachs his to concern equipment, should press form a whole with industrial control system easily, easily the principle of its function devises extension. 80 time come the century on 90 time metaphase, it is the period with PLC the rapiddest development, year increase rate maintains all the time for 30~40% . In this period, PLC measures ability, digital operation ability, man-machine interface ability and network ability to get rising substantially in processing imitate, PLC enters a process to dominate a field gradually, the DCS system that is in regnant position in process control domain was replaced on certain application. PLC has versatility strong, use convenient, get used to wide, dependability ability of tall, interference rejection strong, process designing is simple wait for a characteristic. PLC is controlled in industrial automation especially the position in sequence control, be in what can foreknow to will come, cannot replace. 2, of PLC form divide from the structure, PLC cent is stationary and combined-type (module type) two kinds. Stationary PLC includes CPU board, I/O board, indication face plate, memory piece, power source to wait, these elemental groups synthesize a not dismountable whole. Module type PLC includes module of CPU module, I/O module, memory, power source, motherboard or frame, these module can combine configuration according to certain regulation. 3, of PLCCPU the core that forming CPU is PLC, have neural effect, every PLC has a CPU at least, the function that it gifts by the systematic program of PLC is received coexist program of lay aside user and data, the means that uses scanning collects the condition that delivers by spot input device or data, in the register that stocks a regulation, in the meantime, the solecism in the working status of diagnostic power source and PLC interior circuit and process designing process. Enter after moving, put store from user program implement in read one by one take an instruction, the job that provides via the instruction is being pressed again after the analysis generates corresponding control signal, go leading concerned control circuit. CPU basically reachs the data that implementation connects between them, control and state bus line to form by arithmetic unit, controller, register, CPU unit still includes interface of periphery chip, bus line to reach concerned circuit. Memory basically is used at storage program and data, it is the compositive unit with indispensable PLC. The person that using looks, the in-house circuit of needless labor CPU, but the working mechanism to departmental cent or due and enough understanding. The controller of CPU controls CPU job, read by it take instruction, explanation instruction to reach executive instruction. But working rhythm is controlled by concussion signal. Arithmetic unit is used at having number or logistic operation, work below controller direct. Register participates in operation, store the intermediate result of operation, it also is in controller director come off work is made. CPU speed and memory capacity are the important parameter of PLC, they are deciding the working rate of PLC, IO amount and software capacity, because this is limitting control scope. 4, the interface of PLCI/O module PLC and electric return circuit, it is to pass an input to export a part (I/O) those who finish. I/O module is compositive the I/O circuit of PLC, its input register to reflect input signal condition, output nods report to output Suo Cunqi condition. Input module alternates telegraphic date digital signal enters PLC system, output module is contrary. I/O cent measures an input for switch (DI) , switch measures output (DO) , imitate measures an input (AI) , imitate measures output (AO) wait for module. Switch quantity is to point to leave only and close (or 1 and 0) the signal of two kinds of condition, imitate quantity is the quantity that points to successive change. Commonly used I/O classifies as follows: Switch quantity: Press tension level to divide, have 220VAC, 110VAC, 24VDC, by segregation means is divided, relay keeps apart He Jing body to be in charge of segregation. Imitate quantity: Press signal type cent, flow pattern having report (4-20mA, 0-20mA) , voltage (0-10V, 0-5V, - 10-10V) wait, press precision cent, have 12bit, 14bit, 16bit. Besides afore-mentioned general IO, still have special IO module, wait for module like thermal resistance, thermocouple, pulse. Determine module norms and amount by I/O check the number, i/O module but much but little, but its are the biggest the ability that counts the basic configuration that suffers CPU to be able to manage, accept the biggest motherboard or restriction of frame chamfer number namely. 5, the integrated circuit that power source of PLC of module of PLC power source uses at be PLC each module provides working power source. In the meantime, some still provides the working power source of 24V for input. Power source inputs a type to have: Alternating current source (220VAC or 110VAC) , direct current source (it is 24VAC commonly usedly) . 6, use motherboard of PLC motherboard or PLC of type of module of frame great majority or frame, its action is: Electric go up, realize the connection between each module, make CPU can visit all module on motherboard, on machinery, realize the join between each module, make each module forms a whole. 7, the other equipment of PLC system 1, process designing equipment: Process designing implement it is PLC development application, monitor move, the examination safeguards indispensable parts of an apparatus, use at the process designing, job state that makes system of pilot of PLC of a few set, monitoring and PLC place to the system, but it does not participate in spot control to move directly. Small process designing implement PLC has commonly hold model process designing implement, current and general by the computer (software of moving process designing) appropriative process designing implement. 2, man-machine interface: The simplest man-machine interface is indicator light and pushbutton, at present liquid crystal screen (or touch screen) the application of terminal of operator of type of an organic whole of type is wider and wider, by the computer (moving configuration software) appropriative man-machine interface gains ground very much. 3, the input exports equipment: Use at permanent memory user data, if EPROM, EEPROM is written implement, bar code reader, input the potentiometer that imitate measures, printer. 8, the industrial network technology with the advanced support of communication couplet net of PLC can be collected effectively, deferent production and administrative data. Accordingly, the network is in automation system is compositive the importance in the project is more and more remarkable, even the viewpoint view that somebody offers " network is controller " . PLC has the function of communication couplet net, it makes between PLC and PLC, PLC and go up information can be exchanged between a computer and other intelligence equipment, form an unified whole, implementation centralizes control dispersedly. Most PLC has RS-232 interface, still have a few inside buy has the port that supports respective communication agreement. The communication of PLC, return unfulfilment each other to operate a gender, IEC set standards of a variety of spot bus line, PLC each manufacturer all has use. Cheng of automatic to chemical industry (especially in massive control system) will tell, choice network is very main. Above all, the network must be open, with convenient and different equipment compositive those who reach prospective system scale is patulous; Next, be aimed at the transmission performance demand of different network administrative levels, choose the form of the network, undertake below the premise of the agreement that this must know this network level in more thorough ground, mechanism; Consider the specific issue such as applicability of environment of compatibility of systematic cost, equipment, spot integratedly again, determine the network level that place of disparate arrangement of ideas uses. CNC Milling