
B–61863E/15
2. SEQUENCE PROGRAMPMC SEQUENCE PROGRAM
43
In a general relay sequence circuit, each relay operates at approximately
the same time. In the figure below for example, when relay A operates,
the relay D and E operate at approximately the same time. (When both
contacts B and C are off.) In PMC sequence control, each relay of the
circuit operates sequentially. When relay A operates, relay D operates,
then relay E (see Fig. 2.1 (a)). Thus each relay operates in sequence which
can be written as a ladder diagram. (programmed sequence)
A B
D
A C
E
Fig. 2.1 (a) Circuit examples
Although the PMC sequential operation is performed at high speed, the
speed will change with the order to be executed.
Fig. 2.1 (b) (A) and (B) illustrate operations varying from the relay circuit
to PMC program.
A C
B
A
C
A
C
A C
B
(A)
(B)
(P.B)
(P.B)
Fig. 2.1 (b) Circuit examples
(1) Relay circuit
Operations are the same in both Fig. 2.1 (b) (A) and (B). Turning on
A (P.B) causes current to flow to coils B and C, which turns on B and
C. When C turns on, B turns off.
(2) PMC program
In Fig. 2.1 (b) (A), as in the relay circuit, turning on A (P.B) turns on
B and C, and after one cycle of the PMC sequence, turns off B. But
in Fig. 2.1 (b) (B), turning on A (P.B) turns on C, but does not turn
on B.
2.1
EXECUTION
PROCEDURE OF
SEQUENCE
PROGRAM