Ladder Rungs Per Routine

[keshik]

I've just opened a Logix program for a large plant and am looking through it for a few things that I need to modify. I'm finding that routines are typically 50-100 rungs long which means there's a ton to go through. My question is if there are any "good practice" rules of thumb for lengths of routines? What do you guys normally do for the longer programs?

 

[daba]

The simple answer is NO.

But best practice, and people differ on this subject, is to break the application into "manageable" chunks. Obviously definition of manageable will vary.

I would suggest you try to think as you write your routines that they may be useful in another application, so limit the routine to a basic function.

Of course, with the Add-On Instruction, this has taken over the concept of subroutine files being "function-blocks", but the idea of making each routine deal with a specific part of the whole does tend to make it easier to understand.

And it doesn't matter how many routines you have, the less they do, the more you can forget about when troubleshooting, and the easier they are to give a sensible name to...

 

[Lancie1]

Keshik,

My rule of thumb is to make PLC routines like a woman's skirt: short to keep it interesting, but long enough to cover the subject.

 

[daba]

Keshik,

My rule of thumb is to make PLC routines like a woman's skirt: short to keep it interesting, but long enough to cover the subject.

one way to put it, i hope our female members take no offense, lol

 

[keshik]

Keshik,

My rule of thumb is to make PLC routines like a woman's skirt: short to keep it interesting, but long enough to cover the subject.

I wouldn't call this my expected reply!

 

[dcooper33]

Keshik,

My rule of thumb is to make PLC routines like a woman's skirt: short to keep it interesting, but long enough to cover the subject.

Well done, sir!

Can't WAIT to use this in conversation!

 

[dmroeder]

Keshik,

My rule of thumb is to make PLC routines like a woman's skirt: short to keep it interesting, but long enough to cover the subject.

Well played sir!

 

[Lancie1]

one way to put it, i hope our female members take no offense, lol

I don't think so, because most women are well aware of that rule.

It was a female high-school English teacher who first told me that rule in answer to my question about how long a paper had to be.

 

[uptown47]

Keshik,

My rule of thumb is to make PLC routines like a woman's skirt: short to keep it interesting, but long enough to cover the subject.

Ha Ha !! Class !!

As a general rule of thumb, I like to keep Functions (I'm a Siemens guy) less than 24 Networks. If it's more than that then it's likely you can split it into 2 Functions (not always - but most of the time).

(But after saying that, I prefer Lancie's answer!)