PLC ladder, made to enter an inverted trapezoid, which is to complex, simple post, here is an inverted trapezoid diagram:
The output is made positive trapezoid that briefly after complex.
Writing good ladder, we must follow the above principles, the review does not meet the changes. First, draw the conventional logic circuit diagram, and then facing compile command statement table, table instruction statement written out, can be transformed into a ladder. Simple procedures can be directly edited ladder, more complex, and must be transformed by means of instruction statement tables. Some books say, the ladder of transformation, to follow the "Shen left and right light" principle, with the above said is a meaning. More experience and unwritten rules, but is conducive to the reader to understand, modify. In fact, PLC programming software, as long as the change can succeed, grammatical, are right.