ladder writing etiquette

[turbotater]

is it proper to branch around a timer with a latching bit
instead of writing a new rung ?

 

[BobB]

Why not? Many people do not do it that way because of habit from older PLCs (and some newer ones) that will not let you do it.

I write some fairly large rungs because my favourite PLC will let me do it. Easier to buzz up and down one rung than dig around 8 or 10 rungs.

As far as "proper" goes, we are all different and have different perceptions of "proper".

 

[russrmartin]

"I write some fairly large rungs because my favourite PLC will let me do it. Easier to buzz up and down one rung than dig around 8 or 10 rungs."

Wait till you need to realtime troubleshoot a Logix5000 that has large rungs like this. You will wish they were simpler, as you cannot see the entire rung. Siemens had a function where you could turn the descriptions off in order to see more rungs and more instructions per rung. This was nice, hopefully AB considers it. Not seeing an entire rung makes troubleshooting a momentary problem difficult. That being said, Bob is right, there's no law or anything against it, and if that works best for him, then it is right for him. The same would go for you.

Russ

 

[jstolaruk]

Wait till you need to realtime troubleshoot a Logix5000 that has large rungs like this.

But it really has to do more with the number of characters in the tag symbols and the pixel size of your screen. Its a lot better than ProWorx32 on a VGA size screen.

 

[turbotater]

sounds good , a branched timer it is ...

thanxs

 

[BobB]

Siemens had a function where you could turn the descriptions off in order to see more rungs and more instructions per rung

So do Omron. I normally write 1 rung for fuel pump control with another rung to flip flop the lead pump and a further rung to start pump and lag pump. The main rung includes the second pump taking over from the first in the case of not in auto, fault, flow fault etc. It is a fairly standard rung today and I am lokking at developing a function block for it. FB is good for this type of standardised operation.

 

[MartB]

I often branch timers like this. However..........if the rung is more than one screen long, I would probably tend to not do so. It's just a personal preference, but when I'm bug testing I like to see a whole rung at a time rather than having to scroll the screen to see the whole rung.

 

[BobB]

but when I'm bug testing I like to see a whole rung at a time rather than having to scroll the screen to see the whole rung.

We all have our preferences for sure. I would rather scroll one rung than have to dive up and down from rung to rung.

 

[R_C]

Wait till you need to realtime troubleshoot a Logix5000 that has large rungs like this. You will wish they were simpler, as you cannot see the entire rung. Siemens had a function where you could turn the descriptions off in order to see more rungs and more instructions per rung. This was nice, hopefully AB considers it. Not seeing an entire rung makes troubleshooting a momentary problem difficult. That being said, Bob is right, there's no law or anything against it, and if that works best for him, then it is right for him. The same would go for you.

Russ

In RSLogix 5000 under Tools/Options/Ladder Display you can check Rung wrapping. Then you will be able to see the entire rung.

 

[Bruce99]

Proper code

Proper is a relative term. Program how you like, as long as it works for you. As for long rungs I use a double head video card and two monitors. The ladder is on one whole screen at 1024 x 768 at 32 bit colour. The second monitor is for data tables. The problem comes when you take the program back to work and try to use one monitor again.

 

[TConnolly]

Wait till you need to realtime troubleshoot a Logix5000 that has large rungs like this. You will wish they were simpler, as you cannot see the entire rung. Siemens had a function where you could turn the descriptions off in order to see more rungs and more instructions per rung. This was nice, hopefully AB considers it. Not seeing an entire rung makes troubleshooting a momentary problem difficult.

In all RSLogix incarnations you can use a zoom control at the top of the screen. You can also turn of the comments as already described. The advanced diagnostics is an incredibly powerful tool to smart filter the display of rungs. Try it out someday. Open a file, open advanced diagnostics from the search menu and select a routine. Click expand and see how your screen changes. Expand until the button goes gray, then Click on an item listed on the panel and see how your screen changes. Observe that not all rungs will be displayed, for example you can expand to disply only the output rungs.

Also in the CLX you can do this:

 

---] [----------( )----( )----+------+

                              |TON   |

                              |      |

                              +------+

 

Which will evaluate exactly like this:

 

----] [---------+----( )-

                |

                +----( )-

                |

                +--+------+-

                   |TON   |

                   |      |-

                   +------+

 

[hd_coop]

We all have our preferences for sure. I would rather scroll one rung than have to dive up and down from rung to rung.

I agree with Mart....we have a program at work which has one rung that when printed is 8 pages long.
I make an effort in all my programs to have a rung wrap around no more than one time.

 

[russrmartin]

Sounds like I have some playing around to do. I generally don't have a problem, but we have one machine that was contracted out and brought in and #1, the tagnames are nothing like the tagname convention we instated in the plant, and #2, some rungs have 20 to 30 instructions on them. Even with the wrap, you can't see the entire rung on one page. Just like you guys said though, that is my preference, and the guy who wrote that program has his. Obviously, I am more comfortable using my own preferences, and no doubt he likes breezing through something he wrote more than something I would write. That's the beauty of PLC's, everybody can be different, but they can still accomplish the same thing doing it.

 

[bobwithdana]

Big Rungs

I believe its possible in AB Contrologix to be able to write any size program with one rung. That is without scheduling etc. What do ya all think about that?

Bob

 

[Tom Jenkins]

Writing an extremely long rung of ladder logic, like using one very long run-on long-winded sentence in normal writing, is not technically incorrect and is certainly allowed by the programming software but it is considered bad technique and certainly discouraged by knowledgeable people in the respective fields because this type of run on sentence and very long wrap around ladder logic is difficult to decipher and makes understanding the intent of the author and absorption of the message more difficult, and with ladder logic there is the added disadvantage of making troubleshooting and debugging virtually impossible becuse the inter-relationships of the multiple elements cannot be absorbed at a glance the way you can with well structured ladder logic.