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Answer Posted / carl_ellis
You'd all fail my class for failure to mention these three
things:
- A project scope document
What is to be controlled, alarmed, displayed and
communicated? What is the purpose and what are the
functional criteria for the project? What are requirements
for acceptance of the project? What limits the
dreaded 'scope creep' ("Oh, I thought it would
include . . ." or "we need to add this")
I tell my pupils that the homework problem description
constitutes the 'scope' for purposes of a class, but in the
real world it might be a 400 page scope document, but
whatever form it takes, they should never accept a verbal
description, but should insist on a written document,
because that's what defines whether their programming meets
the standard of having been done properly.
- An I/O list is absolutely essential. What are the
inputs, what are the outputs?
- The PLC's documentation
Nobody remembers all the little syntax or functional
details. It's up to the programmer to look this stuff up
because in the real world, there's no 'teacher' to answer
the question about the timer's minimum interval.
Those three things are essential. Lack of any of the 3
constitutes negligence.
Lack of mention of any of the 3 ?in the 5 answers already
posted tells me your instructors are book people, not real
world PLC programmers.
------------------------------
Carl Ellis, Measure First
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