PLC but parts of an apparatus of process designing logic chooses a method

As PLC popularize, the sort of PLC product and amount are increasing, and the function is perfect with each passing day also. In recent years, the PLC product that introduces from the country such as the United States, Japan, Germany and domestic manufacturer are assembled or the product of proper motion development already had about a hundred kinds of a few series, type. The breed of PLC is various, method of system of its structure type, function, capacity, instruction, process designing, price each are not identical, applicable circumstance also has each emphasize particularly on. Accordingly, logical choice PLC, to raising PLC the application in controlling a system is having main effect. The chooses PLC type option basic principle of 1 type is, below the premise that satisfies a requirement in the function, the alternative is the most credible, safeguard use the most convenient and the optimization type of performance/price ratio. It is better that fixed, ambient conditions is compared in process (maintenance volume is minor) circumstance, the proposal chooses the PLC of integral type construction; Other circumstance had better choose the PLC of module type construction. Measure to switch control and with switch capacity control is given priority to, in taking a few imitate to measure pilot project project, general its control speed to need not consider, accordingly, choose take A/D changeover, D/A changeover, add decrease operation, data the cheap machine of deferent function can satisfy a requirement. And compare in control complex, in controlling a function to ask to compare tall project project (if want to realize net of couplet of PID operation, closed-loop control, communication,wait) , can inspect control dimensions and complex degree to choose intermediate or high-grade engine. Among them the automation of the distributed control system that high-grade machine basically uses at extensive process control, complete PLC and whole factory. According to different applied object, watch １ listed a few kinds of functions of PLC choose. The function that expresses 1 PLC reachs applied field to combine system of large to company, answer to accomplish type to unite as far as possible. Such, the PLC module of same type but each other is reserve, facilitating machine parts or tools kept in reserve spares parts purchase and manage; In the meantime, its unified function reachs what process designing method also is helpful for technical force to groom, of technical level raise the development with the function; In addition, because its peripheral equipment is current, resource can be shared, accordingly, match above after the computer can become the couplet of much stage PLC that controls each only system a multistage is distributed control system, such facilitating mutual communication, centralized management. 2 inputs / the choice PLC of output is system of control of a kind of industry, its control produces equipment to seeming industry or industry produces a course, working environment is industrial production site. It and the connection that industry produces a course come true through I/O interface module. Can detect through I/O interface module all sorts of parameter that are accused to produce a course, serve as control information to be opposite with these field data object be accusinged undertakes controlling. Pass I/O interface module to give equipment be accusinged or industrial production the course the processing of controller as a result at the same time, thereby all sorts of actuator come to drive implementation control. The information that PLC gathers from the spot and the control signal that export peripheral equipment need to pass certain distance, to ensure of these information do not have correctly by accident, the I/O interface module of PLC has better interference rejection capacity. According to real need, usually, PLC has a lot of I/O interface module, include switch to measure input module, switch to measure output module, imitate to measure input module, imitate to measure output module and other a few special module, use Shi Yinggen undertakes choosing according to their characteristic. 2.

When the demand that basis of check the number of 1 affirmatory I/O controls a system determines the I/O check the number of a need, should increase 10% ～ again the equipment dosage of 20% , so that increase control function at any time. Control a target to, as a result of adoption control the method differs or process designing level differs, i/O check the number also should differ somewhat. Express the I/O check the number that the 2 switch that listed typical transmission and place of commonly used and electric component need measure. The I/O check the number that expresses 2 typical transmission and the switch that commonly used and electric component wants to measure 2.

The interface of input ／ output that 2 switch quantity inputs ／ output to adopt a standard can be mixed from sensor switch (wait like switch of pushbutton, spacing) reach control (open ／ to close) equipment (wait like starter of indicator light, warning apparatus, electromotor) receive signal. Typical communication inputs ／ to output signal to be 24 ～ 240V, dc inputs ／ to output signal to be 5 ～ 240V. Although input differs because of making manufacturer differ, but some character are identical. Shake like what be used at eliminating wrong signal circuit; Avoid the surge at bigger transient over voltage to protect circuit to wait. In addition, most input is inputted in high-pressured power source and the control of interface circuit sets optional segregation circuit between logistic part. When evaluating disperse to output, the segregation circuit between protection of surge of silk of frit of Lv of take an examination, instantaneous and power source and logistic circuit. Frit silk circuit perhaps is in expenditure is more in the begining, but the likelihood installs frit silk cost to want than outer ministry little. 2.

Interface of output of ／ of input of quantity of imitate of output of ／ of input of 3 imitate quantity uses the signal that feels sensor generation commonly. These interface can be used at measuring discharge, temperature and pressure, can use at controlling voltage or voltaic output equipment. The typical span of these interface is - 20mA of 10V of 10V of 10 ～ ＋ , 0 ～ ＋ , 4 ～ or 10 ～ 50mA. A few production manufacturer have special imitate interface in the design on PLC, can receive low n signal consequently, wait like RTD, thermocouple. Generally speaking, module of this kind of interface can be used at receiving the thermocouple that the type differs on same module or RTD to mix signal. 2.

4 special functions are defeated by person ／ when output is choosing a PLC, the user may face a few special kinds and if the I/O demarcate  that cannot come true with standard I/O is fixed position, fast the  such as input, frequency. Right now the user ought to consider manufacturer of supply and marketing to whether be offerred have the special module that conduces to utmost reducing control effect. Oneself of module of a little special interface can process one share field data, the disengagement in making CPU is handled from time-consuming task thereby comes out. 2.

Output of ／ of input of 5 intelligence type is current, the manufacturer home of PLC rolled out the input ／ of type of a few intelligence to output module in succession. General intelligence type inputs ／ to output module itself to contain processor, can make the processing that sets beforehand to input or outputting signal, send CPU or direct output processing as a result, the processing rate that can raise PLC so saves the capacity of memory. Module of output of ／ of intelligent type input has high speed tally (can make addition computation or subtration computation) , cam simulator (use as absolutely encode loses a person) , processor of BASIC of ／ of the PID adjuster that belt speed spends compensatory cam simulator, odd loop or much loop, ASCII, RS, . Watch 3 induced the general regulation that opts I/O module. The memory that the type of memory of general and regular 3 PLC of the I/O interface module that expresses 3 choices PLC and place of system of capacity choice PLC use basically reachs PAM3 sort composition by PROM, E-PROM, memory capacity changes along with the size of the machine, the capacity of the oldest storage of general and small-sized machine under 6kB, the capacity of the oldest storage of medium-sized aircraft can amount to 64kB, the capacity of the oldest storage of large scale computer can go up million byte. The memory that data can reach according to the program when using needs to choose appropriate model, also can undertake the augment of memory is designed technically when necessary. The memory capacity choice of PLC and calculative the first kind of method is: The division check the number that uses according to process designing uses a capacity actually of mathematical calculation memory. The 2nd kind is estimation algorithm, the user can be mixed according to control dimensions applied purpose, according to the watch the formula of 4 comes estimation. Go to the lavatory to use, should stay commonly have 25% ～ the abundant quantity of 30% , the optimal means that gets memory capacity is generating program, used how many word namely. Know the word that every instruction place uses is counted, the user can decide accurate memory capacity. Watch 4 gave out at the same time the estimation method of memory capacity. 4 software choice is in the method that expresses capacity of memory of estimation of 4 control purpose in implementation process of the system, the process designing problem of PLC is very important. The user ought to choose the software function of PLC product to understand somewhat to place. Normally the circumstance falls, of the control hardware that the software of a system always uses at handling controller to have. But, some application system also needs to control the software function beyond hardware component. For example, the special control that an application system may include to need complex maths computation and data processing operation or data collect a function. The choice of instruction collect achieves the decision the difficult easy rate of software task. Practicable instruction collect realizes immediate impact the time that the time that control program place needs and program execute. When the consideration of condition of the 5 technologies that prop up chooses PLC, have having condition of the technology that prop up is important choice basis likewise. Condition of the technology that prop up includes following content: (Method of 1) process designing is portable simple and easy process designing implement basically use at small-sized PLC, its control scope is little, the procedure is simple, usable and simple and easy process designing implement; CRT process designing implement apply to large and medium-sized PLC, divide outside can be being used at weave and inputting a program, still can edit and print program text version; Because IBM-PC already got popular popularizing, IBM-PC reachs his package of software of compatible machine process designing is the process designing tool with very good PLC. Current, PLC manufacturer is in devote oneself to to develop applicable the IBM-PC of own type reachs his package of software of compatible machine process designing, scored a success. (2) undertakes program text version handles the processing of condition of processing of simple program text version and graph, parameter and position, include to print echelon logic; The program is tagged, annotate of the assignment name that includes contact and coil, network, this is read to user or software engineer and debug a program very useful; The processing of graph and text. (3) program stores means is mixed to technical data archives reserve for the data, of the program store the method has the kind such as tape, floppy disk or box of EEPROM storage program, specific choose which kinds to store means, depend on the technical condition that chooses model. (Package of 4) communication software uses the control system of a computer management to the network controls a construction or needing, have be being wrapped without communication software is the main basis that chooses PLC. Communication software package often is used together with communication hardware, wait like the modem. The environmental suitability of 6 PLC is used at industrial control directly normally as a result of PLC, the manufacturer designs it into job of can reliable below harsh ambient conditions ground. Nevertheless, every kinds of PLC has his environmental technology requirement, the user is in when choosing, when designing control system especially, want to give sufficient consideration to ambient conditions. General PLC reachs his exterior circuit (include I/O module, auxiliary power source to wait) can be below the ambient conditions that expresses 5 kinds reliable job. The working environment that expresses 5 PLC the ceaseless progress of 7 last words as science and technology, the sort of PLC is increasingly various, the function also increases gradually. In the article although induced a few methods that choose PLC, but still must make proper adjustment according to actual condition in real work, so that the design gives the control system of contented expectation. CNC Milling