latched input
latched input
(OP)
anyone have any experienced of inputs being latched on on plcs and suggestions to the possible causes. I have heard that poor neutral faults can cause this but cant really see how
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RE: latched input
But that is history. Gone. No problem anymore. A badly designed system that relied on connection to the neutral to reduce input voltage could cause that phenomenon if you lost the neutral. So that part of the story is also plausible.
But do not use that as an explanation for problems in a modern PLC. All major CMOS manufactorer have "Latch-Up-Hardened" inputs nowadays.
Gunnar Englund
www.gke.org
RE: latched input
I know 120 volts into a DC input card will permanently latch the input. I saw it done TWICE in a row by the same technician. He did not appreciate the humor I found in the situation, but we ALL make mistakes (especially me at times).
Bigbillnky,C.E.F.....(Chief Electrical Flunky)
RE: latched input
Gunnar Englund
www.gke.org
RE: latched input
The capacitive reactance forms a parallel path with the remote contact.
Also, at least in the past, driving an input directly from a solid-state output module can cause the input to latch.
RE: latched input
thanks for your reply. the input was 24vdc i actually disconnected the wire to it. could you explain the cmos bit a little further for me
thanks
RE: latched input
Gunnar Englund
www.gke.org
RE: latched input