GSK 218M, Руководство по подключению и программированию PLC

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GSK218M CNC System Connection and PLC Manual
15
2 Sequence Program
Since PLC sequence control handled by software and operates on principle difference from a
general relay circuit, the sequence control method must be fully understood in order to design PLC
sequence program.
2.1 Execution process of sequence program
In general relay control circuit, each relay operates at approximately the same time, in the figure
below for example, when relay A operatre, the relay D and E operate at approximately the same
time(when contacts B and C are off)., In PLC sequence control, each relay of circuit operates
sequenctially. When relay A operates, relay D operates, then relay E(see the below figure). Thus
each relay operates in sequence which can be written as a ladder diagram. (programmed
sequence).
Fig. 2.1(a) circuit example
Fig.(b) and (c) illustrate operations varying from the relay circuit to PLC program.
Fig. 2.1(b)
Fig. 2.1(c)
A
A C
D
E
B
A C
A
B
C
A
A
C
B
C