Double Coil Avoidance

[GaryS]

Actually in Logix 5000 you will get a Warning on duplicate coils but it will not prevent you from downloading the program.
and there at times when the only solution is to use duplicate coils if you are careful there is no problem. I don't normally like to see them but sometimes they are the best solution.

 

[Dayvieboy]

I have never ever seen a time when duplicate coils are an only solution.

One of our company's many specs is your program must be compiled & delivered without any warnings. If it has warnings you will not be paid $$$

The last thing we need to deal with is parsing through 1000 warnings to find the
one 1 that is causing a problem.

This exact issue is what drove this being added to our PLC spec decades ago.
Tool down and it took 1 day checking through all of the warnings to find the root cause.

 

[Dayvieboy]

Hello,
I get why it works the way it does, although in my mind since this is programming, it should work the way I want it to.

My programs have many times not done what I wanted them to do

They have always without exception done EXACTLY what I told them to do

 

[Sydney]

Allen Bradley did caution against using double coils in there training classes. I''m sure part of that was to do with liability, but they also stressed that if used for control it could cause equipment damage or personal injury.

I never went to a training class where double coils were used in logic examples. Most training personal suggested putting all output coils in one location on separate rungs and used internal bits depending on which Allen Bradley platform you were using, PLC5, 500, or 5000.