Questions regarding --(S)----- coils
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--(s)---is the reset coil; when current can flow through --(S)--, it resets the specified value of the unit to “0”. My question is: regarding the normally open contact corresponding to -(S), does resetting that contact keep it in the normally open state? What purpose does --(S)-- serve then?
This post was last edited by budaoweng123 on 2016-1-17 at 10:05. The components in this ladder diagram are equivalent to the coils of relays; accordingly, (R) sets the value to 0 while (S) sets it to 1. The coil controls the normally open and normally closed contacts.
It’s like this: when (R) is powered, the corresponding contact should be reset to 0. Then, is the corresponding normally open contact closed or open? (According to my understanding, since it is reset to 0, the normally open contact should still remain a normally open contact.) If the normally open contact remains normally open regardless of whether (R) is powered or not, then what’s the use of (R)?
Today I checked the PLC monitoring; in some cases, current couldn’t flow through the circuit, yet they were still clearly powered, causing the associated normally open contacts to become normally closed. In some (R) circuits, there is no current flowing through them; therefore they cannot be activated, and the associated contacts do not function. I’m not sure what the reason for this is