PLC is used in a certain number of difficulty analysises

The collection of exterior input signal the peripheral equipment of PLC basically is to accuse the input in making a system exports equipment, transporting person fixture among them is issue all sorts of control signal to the system advocate your electric equipment, what must notice when writing control program exterior input equipment is used is to often leave to often still close contact, have to program for the foundation with this. Otherwise easy occurrence control is wrong. Have in PLC in-house memory special the input relay that stores at inputting condition area, each input equipment (switch of switch, pushbutton, journey or sensor signal) memory of circuit of interface of condition by input is inside this area, every input relay can store one inputs facility status. " is not the " relay that uses in PLC hypostatic relay, however " soft relay " , can offer countless to often leave, often shut contact to be used at process designing. Every " soft relay " only one of corresponding PLC location (Bit) , this condition is "1" , express this " soft relay coil " electrify, criterion the contact of all this relay in the program movement. Input relay is received as PLC exterior advocate the parts of an apparatus of your signal, pass wiring and connection of photograph of exterior input equipment, condition of " of its " coil can by drive of exterior input signal. The collection that inputs signal works if sketch map pursues 1. Input relay coil its condition depends on signal of input of 1PLC of peripheral equipment state diagram collects sketch map to pursue 1 in, inputting what equipment chooses is pushbutton SB0 often close contact, input relay the coil condition of X0 depends on the condition of SB0. When this pushbutton did not press, x0 coil condition is input relay "1" electrify condition, all X0 contact in the program all movement, often open contact to put through namely, often shut contact to disconnect; If press this pushbutton, input relay X0 coil condition cuts off the power for "0" condition, all X0 contact in the program all restore normality. If input relay,connective inputs equipment is pushbutton SB0 to often open contact, criterion the situation is apropos and opposite: Did not press in this pushbutton when, x0 coil condition is input relay "0" cuts off the power condition, all X0 contact in the program all not movement; If press this pushbutton, x0 coil condition is input relay "1" electrify condition, all X0 contact in the program all movement. 2.

Jockey pushbutton is used often shut model when because PLC is in,contact of moving program differentiate opens position, depend on only relay of the input in its memory the condition of coil, do not identify peripheral equipment directly, accordingly when process designing, of peripheral equipment choose with the program closely related medium contact type. This is one is in contrast when graph of electric control principle undertakes PLC process designing easy occurrence problem. The most typical case is main control- - protect since " stop control " to jockey mediumly control. Protect since graph 2 " stop graph of control " electric principle to pursue 2 halt plan of control " electric principle to be protected since " , in this system, pushbutton SB0 is used at jockeying to control, because this is used,its often shut contact to establish ties at control line road. SBl is starting pushbutton, use its often open contact. If use identical device (jockey namely SB0 is used often close contact, starting SBl is used often open contact) , use PLC to have this control, require process of graph of process designing echelon (graph 3) : Protect since graph 3 " stay course of graph of control " echelon (jockey pushbutton uses often close contact) I/O allocation: SB0- - X0, SBl- - Xl, outputting what X0 of the shutdown alarm in graph of Y0 this echelon uses is to often open contact series connection to be in control line road, because,this is exterior jockey equipment chooses pushbutton to often shut contact be caused by, do not operate this pushbutton, output Y0 to put through normally, if press this pushbutton, output Y0 cuts off the power. 3.

Jockey pushbutton is used often leave model if hope the work out gives the echelon graph order that accords with us to read a habit at ordinary times (graph 4) , be in choose exterior jockey use pushbutton SB0 needs when equipment often open contact and X0 to be linked together. Protect since graph 4 " stay course of graph of control " echelon (jockey pushbutton uses often open contact) I/O allocation: SB0- - X0, SBl- - Xl, output Y0 pursues 3, 4 echelon graph fulfils same control function, the contact kind that X0 of the shutdown alarm in the program uses is not same however, its reason joins namely inputting relay on X0 exterior jockey pushbutton contact type is chosen different. The graph shows echelon plan program 4 times more accord with us read a habit, analyse its more easily also to control a function logically, in because this is formed in PLC,controlling a system, no matter exterior switch, pushbutton is used at start or jockeying, choose commonly often leave model, this is a problem that notes all the more in the need when use PLC. 2, the run mode of " serial " of PLC and the work out PLC that control a process and pilot of afterwards report contactor are important one of distinction work namely kind is different. By " collateral " means works system of control of afterwards report contactor, work by the means that carries out at the same time that is to say, want to form voltaic access only, have a few electric equipment possibly at the same time movement. And with " serial " means works PLC, when PLC is executing an order circularly, it is the book according to the statement writes ordinal from above to below to have logistic operation, and in front the result of logistic operation can be affected from the back the logistic operation result of the statement. Accordingly echelon pursues when process designing, the position of each statement also can produce crucial effect to controlling a function. For example: Graph 5 programs 1 program 1 debug a result: X0 puts through 3 times, y3 puts through, x0 puts through 1 times again, y3 disconnects. Graph 6 programs 2 programs debug 2 programs result. X0 puts through 3 times, y3 puts through the instant disconnects namely. Above in two programs, the logistic condition homogeneous phase before CTl02 of output Y3, tally and R0 of in-house general relay is the same as, it is tally CTl02 was in statement position to produce change merely, and the moving result of two paragraphs of programs is disparate. Because the effect kind to outputting Y3 happened CTl02 to change,this is. When executing the first paragraph of order, the condition that judges output Y3 above all, judge the condition of CTl02 again, the status change of CTl02 can scan in the next only cycle produces an effect to Y3; And when executing the 2nd paragraph of order, the condition that judges CTl02 above all, judge the condition that outputs Y3 again, the status change of CTl02 will scan in this the condition of Y3 of periodic and immediate impact. Can reach from above discussion, because PLC uses means of job of " serial " , so even if same component, located in echelon graph position is different, its job status also can differ somewhat, when using echelon graph to undertake dominating to program accordingly, answer control task to undertake sufficient analysis, reasonable arrangement the position of component of each process designing, ability realizes control well and truly quite. 3, all sorts of functions of the PLC of process designing component of PLC basically are to pass moving control program to come true. When work out program, the process designing component that needs reasonable use PLC to offer (namely soft component) . The commonly used process designing component in FPO PLC has two kinds: Component (Bit) with word component (Word) . Component is the unit of a binary digit that place of PLC memory area offers actually, be called again soft relay, basically use as the process designing component that dictates basically orderly, if input relay relay of Xn, output is Rn of Yn, in-house general relay, time (computation) implement wait, its participate in pilot means basically is pass corresponding contact connect status change to affect logistic operation result to be outputted namely. Word component is the unit of a word inside PLC memory area (16bit) , basically use the process designing component that makes functional instruction and advanced statement, normally in order to deposits data, exactly the amount occupies register DTn, time (computation) implement EVn of value of set value SVn, course. Word component does not have contact, share control with integral content normally. Notable is the input in memory (X) area, output (Y) area and interior are general (R) area, every Bit in this area all can use as a component, and every 16bit can make component of a word, if WRIO is namely by 16 word component that R10F makes a component R100 ～ , once the content in this word component produces change, these 16 condition also produces a change subsequently. Be like: Graph programme diagram of give typical examples of component of 7 process designing shows a program 7 times in, WR0 is word component namely, it is the process designing component of SR of left shift instruction, and Y0 is the coil that outputs soft relay, x0, X1, X2, X3 is the contact that loses person soft relay, among them the R4 contact of the 4th pace is a component R4 often open contact, and component R4 is one of word component WR0, accordingly its condition gets the shift result of WR0 of be confined to. 4, the sequence control of process designing method that sequence control much pace exports together is the task of a kind of control with manufacturing common site, PLC dictates the pace receives an instruction to library technical secondary school is used at sequence control. When the pace enters instruction process designing, according to the block that technological process differentiates the program to become independent for each, when carrying out, CPU presses order of echelon graph process designing strictly, activation of the ability after before be being carried out only one paragraph of program issues a paragraph of order, before issueing a paragraph of program to carry out, will in front block restoration. And ask on grammar the output that each block uses does not allow repeat. When the case that this has much pace to be outputted together in solving sequence control task, brought certain difficulty. Have the aid of can go to the lavatory at in-house general relay solve this one difficult problem. If task of some sequence control is like the following flow chart (graph 8) be shown. Graph flow chart of movement of 8 some manipulator can see from manipulator movement flow chart, the job that this control task circulates every can differentiate for 8 paces, among them the 1st pace and act of the 5th pace are same, all be rise; The 3rd pace and act of the 7th pace are same, all be drop. When using a pace to undertake process designing into the instruction, the output of the block of correspondence of place of situation of these two labor cannot be installed directly for Y3, Y4, same output uses a meeting twice to appear solecism. Should consider to use the Rn of in-house general relay that is used at memory mediacy to solve this problem at this moment. If the graph shows echelon plan program 7 times, among them R1, R5 is defined to be the 1st pace and the output of the 5th pace respectively, r3, R7 is defined to be the 3rd pace and the output of the 7th pace respectively, output the condition of R1, R5 ascendant Y3 again after the pace enters an end, the position of R3, R7 output reachs drop Y4, can go to the lavatory through such method the question with a certain number of labor situation same output in solving sequence control task. Graph echelon of 9 manipulator control pursues 5, last word abecedarian masters easily to the fundamental application of PLC, but should accomplish use neatly still want difficulty of pair of a few technologies and understanding of use skill profundity. Before process designing, want to undertake serious analysis to controlling the job, logical choice peripheral equipment and process designing component, undertake process designing for the foundation with this; In process designing process, if can clever word uses process designing cell ably, undertake a program weave reasonably, can make program logic clear, readability increases. CNC Milling