Expand effectively but the practical method that program controller I/O chooses

4 document label piles up B as PLC system of complex degree increase the grow in quantity with equipment be accusinged, the user uses the method that adds patulous module to solve I/O to select the issue of resource insecurity normally, this raises cost necessarily. It is with Xi Menzi PLC exemple, introduce the practical method that a few kinds of patulous on the foundation of existing natural resources I/O choose. One, the main train of thought that software way software designs is instruction of process designing of have the aid of, implementation is used. The first time press pushbutton output is tall n (low n) , press pushbutton output is low n again (tall n) , press output is tall n again the 3rd times (low n) , the rest may be deduced by analogy, a such switch can save an input point. 1. Use jump change the edge detects the instruction adds in-house and auxiliary relay to be started with pushbutton / stop equipment to be exemple, normally the need below the circumstance inputs a dot 2 times (start, stop) , and can save an input point through process designing, see a picture 1. The program explains: I0 of pushbutton SB join.

0, press for the first time after SB, i0.

Of 0 often open contact to close, detect in RLO edge below the action of instruction FP, auxiliary relay M0.

0 put through a scanning is periodic, output relay Q0.

The coil of 0 gets report and from the lock, at the same time Q0.

0 another often open contact to close, for M0.

1 put through ready-made; Press the 2nd times after SB, below the action that dictates in FP, m0.

Of 0 often open contact to put through M0.

The coil of 1, m0.

The often shut contact to cut off PLC output of 1 (Q0.

0) , implementation is used. 2. Use R/S instruction adds in-house and auxiliary relay to still be used " 1 " example, the program sees a picture 2. Nextpage 3. Use edge detects, jump turn instruction A I0.

0FP M0.

0JNB OUT AN Q0.

Q0 of 0 ＝ .

0OUT: N0P0 program explains: The 4th, the function of 5 statements is implementation Q0.

Take of 0 oneself instead, the 1st, the action of 2 statements is demarcate is become only I0.

The Q0 when the ascendant edge of 0 arrives.

0 take instead, jump out to take otherwise combat block (if did not jump,turn instruction, every scanning cycle meets the program Q0.

The condition of 0 is taken instead) , implementation is used. 4. Use edge detects, different or instruction A I0.

0FP M0.

0X Q0.

Q0 of 0 ＝ .

0 programs explain: Detect for the first time I0.

The ascendant edge of 0, right now Q0.

0 for 0, different or hind output is 1, when the 2nd scanning cycle comes, already not was I0 right now.

The ascendant edge of 0, because of this Q0.

0 for 0, however right now Q0.

0 it is however 1, different or hind maintain a result to still be 1; Detect the 2nd times I0.

The ascendant edge of 0, q0.

0 for 1, different or hind output is 0, when next scanning cycle comes, not be I0.

The ascendant edge of 0, because of this Q0.

0 for 0, right now Q0.

0 just about 0, accordingly different or maintain output to still be 0. 2, hardware law 1. Equipment of pilot of system of PLC of the input when dividing constituent often needs " automatic ／ hand uses control " , automatic ／ hand is moved in equipment moving process won't undertake at the same time, because this can change automatic ／ hand,receive PLC to input end in group according to control requirement, reduce input point, electric equipment receives a plan repeatedly 3, among them SA moves ／ for the hand automatic diverter switch, SB1, SB2, SB3 is a group of inputs, SB10, SB20, SB30 is another group of inputs. To a little interlocking processing, if PLC interior does not collect the condition of this contact signal, but outer ministry undertakes hardware interlocking, need not the input end that each switch quantity receives PLC, OK also and a few more managing I/O dot. 2. Shunt-wound and common the executive component with identical status of the job in moving process of output general system is shunt-wound, notice circumstance of laden general power cannot exceed what individual output nods to permit laden capability, see a picture 4. Nextpage 3. Simplify exterior join this law is commonly used open ／ to stop control at the much ground of electric machinery. 3 ground open some electric machinery graceful control wiring sees a picture 5, among them SB1, SB2, SB3 is the pushbutton that start, SB11, SB12, SB13 is stop pushbutton. 3, form of soft, hardware is legal this kind of method can reduce what I/O nods to use in great quantities, input the circumstance with more signal to fall in control system for example, can use coder to code to inputting signal first, receive the input end of PLC next, repass PLC in-house program undertakes coding, identify each to input signal, exterior wiring sees a picture 6. Introduce 8 lines preferential coder 74LS148 can prevent one 3 lines random code appears when many signal are inputted at the same time, by its function is knowable, this chip low n is effective, because this uses 3 blame,n of door general output is changed into logistic. Sometimes even coder in choosing an output end and patulous end to also receive PLC, reduce systematic miscarriage of justice to break. It is with pushbutton SB2 now exemple, the program that shows coding of PLC internal software identifies a method: Press after SB2, no matter whether press SB0 and SB1, should not press only SB3 ～ SB7, right now output of A, B, C is I01, the course is not the I0 after the door.

0=0, I0.

1=1, I0.

2=0, corresponding STL translation program is as follows: LDN I0.

1A I0.

1AN I0.

M0 of 2 ＝ .

2 should press pushbutton SB2, m0.

2 for 1, after SB2 bounces, m0.

2 it is again 0, use M0 namely.

Of 2 often opened contact to replace pushbutton SB2, realized software coding. This exemple PLC can read in an input condition in 8 inputs only in each scanning cycle, if 2 above switch closes, PLC can detect only that signal with a high priority. Manage together, when control the system outputs signal relatively a long time, the method that can use software code to add hardware coding expands output is nodded. Use soft, hardware to combine a law to want to notice to n matchs and receive ventriloquial art standard (drive electric current and voltage level-headed limits) , the method that still needs to increase to appropriate signal magnifies and lie between I/O to nod sometimes realizes way appreciably to differ in the PLC of different brand, but main train of thought is same. In project practice, reasonable use these methods, can reduce I/O to order use quantity, raise I/O effectively to nod utilization rate, those who reduce PLC is redundant, reduce cost. CNC Milling CNC Machining