Is it Ok to command open to an already open valve?

[chriswarrn]

Im my experience, using double coils greatly increases the difficulty of troubleshooting. Whenever I see an instance of double coil I start to cuss the people who wrote it. Techs like me don't have the time to study a program to find a problem. We're too busy putting out fires. Programs that are written with the maintenance tech in mind are a pleasure do work with and a true asset to the companys who use them.

 

[Bill Simpson]

***Assembly language and C programmers do not have such rules***

There are no rules, just common sense learned from experience and set forth as guidelines... Whether you program in assembly language, c, or ladder logic, the task is almost identical, and if you choose to obscure your code to the point that it's unclear as to what is controlling what, then the results will be identical..

Regardless of the language used, common sense tells us that someday, someone, will want to know why a particular piece of controlled equipment was started, or stopped... If you want to set off a detonation in a mining operation, do you wire in 1 switch or 2?... If you use 2, then are they placed together at the same location,,, or is the second one out of sight in some forgotten location..?

 

[panic mode]

Bad program is a bad program regardless of language.
Sure multiple coils in ladder program can work
but just because something can work it doesn't mean
it is a good thing. And despite many aspects or programming
ladder is not c or assembler. When company's network
is down or creeping slow because of just another hole
in Outlook, nobody gets five Microsoft programmers within
an hour to fix the problem. If you don't believe it,
call Microsoft next time your machine is screwed up.

Using double coils is bad programming practice just like
not commenting programs, extensive use of pulses and
oneshots, not organizing project etc.

All of this makes troubleshooting slower and let's face it,
who like to troubleshoot somebody else's program,
specially when production suffers and guys around you
run like headless chicken...

I do WANT program to let me know that guy who
worked on something before I got there was using
double coils. I want ladder edditor that pop's up
same message when you open project even if one
single bit is not commented.

I want to see detailed
report every time project is open:

used bits: xxx
commented bits : xx%
used words: xxx
commented words: xx%
average comment length (characters) : xx
used rungs: xx
commented rungs: xxx
average rung comment (characters): xxx
used timers: xxx
used counters: xxx
etc. you get the point...

I want that my customer see it too and I want customer
to get uneasy if the numbers are not right when they
commision project, not when they need someone to
come to rescue...