Notes
What we have learned about FDS and PLC work.
Hints and tips on functional design specs, I/O lists and PLC code, with the odd note on how FDSIQ and ScaffIQ work.
How to write an interlock a programmer cannot misread
One vague sentence in an FDS can become three different interlocks. Here is how to word the condition, the action and the reset so there is only one way to read it.
Five checks to make before you hand an FDS to a programmer
A good handover saves days and a poor one costs weeks. Five quick checks on an FDS catch most of the questions that would otherwise come back mid-project.
Getting from an FDS to a working Studio 5000 project
A functional design spec describes a system in words. Studio 5000 needs tags, routines and an L5X to import. Here is what actually has to happen between the two and where that work usually goes wrong.
What changes when an I/O list is generated instead of typed
Writing an I/O list by hand is a repetition problem, not a skill problem. Here is what actually changes when it comes from the same structured record as the FDS.
Why an FDS, an I/O list and a PLC program drift apart
A functional design spec, an I/O list and a PLC program describe the same system. Kept as separate files, they stop agreeing with each other within weeks.