Self locking function of PLC ladder diagram


Its normally open coils continue to stay in power ON” State function is called locking. As shown in Figure 5-3 the start, maintain and stop the program (stop program for short) is a typical ladder with locking function, X2 and X1 as the starting signal for the stop signal.

Figure 5-3 from the stop procedure and sequence diagram
A) stop priority b) start priority
Figure 5-3a for the stop priority programs, that is, when X1 and X2 are connected, then Y1 disconnected. 5-3B for starting a program of priority, that is, when X1 and X2 are connected, then Y1 is connected. Stopping programs can also be set (SET) and reset (RST) instructions to implement. In practical applications, the starting signal and stop signal may consist of multiple touch points of series and parallel circuits.

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