Ladder conversion utility


Thread Starter

Norm Aylward

We have many PLCs with very little documentation. It would be very helpful to have a program to create drawings from the ladder logic. I have heard of programs that create ladder logic that can produce flow charts etc.. I need to take existing relay ladder logic and make drawings for reference to build documentation.


James Ingraham

Call me crazy, but I don't think that's even theoretically possible.

Sage Automation, Inc.

Daniel Chartier

Hello norm;
I think what youm are looking for requires analysis, judgement and experience. I don't think they make that kind of AI software yet. It
sounds like a pencil and paper job to me.
Daniel Chartier

Eduardo Manuel C. Cipriano

Hello Norm,

Ladder Logic and Flow are are two different types of standards programming PLC as it has been included in the IEC1131-5

These type of programming have different applications like the Ladder Logic are mainly use for Interlocking or converting existing conventional controllers while the flow charts are used for batching process, although it is possible to convert ladder logic to Flow Chart type of programming this will depend on how
powerful is the software as well as the programmer.

the only software that i know who could convert two different types of program standards is from Ladder Logic to Statement List.

so i think you for yourself could do it manually but like i said it would take a hell of programming experience to do it.


[email protected]
Eduardo Manuel C. Cipriano
Sr. Systems Engr.
Systems Engineering Department
Yokogawa Phils. Inc.

Vladimir E. Zyubin

Hello Norm,

The text of program is created mainly for the human-programmer, not for the computer. So, from the human side, the text(and high-level language(s)) is needed to provide readability (maintainability) only. From the other hand the text has formal notation.. so, it can be converted to the machine codes (by a translator)...

The tasks of the language-to-language convertation do not solve the problem of readability, but the problem of cross-language porting only.

So, even if the converter exists, it can not solve your problem (to build documentation). Alas.

IMO, you need to rewrite the program "by hands".

BTW, to provide good (readable) documentation, concealment of some kind of info in the representation is needed... very frequently... So, even if you have original text in SFC, you ought to rewrite it for the doc.

Best regards,
This is simple. You will require:
- 1 Honours student
- 1 Masters student
- PhD students (as available/required)

1) give the problem to the Honours student. Wait one year.
2) give the problem to the Masters student. Wait 2-3 years.
3) give the problem to the PhD students until solved.

At the end, you should have a program which will convert ladder logic into half-decent flow charts.

Unfortunately, there's no easy way to convert ladder into the original control logic. If the original program was auto-converted from a SFC or something and not touched (much) since, it should be reasonably easy to reverse that auto-conversion. But if it hasn't been, or if it's been altered since in a way that doesn't follow the schema, it'll be much more difficult.

> We have many PLCs with very little documentation.
> I need to take existing relay ladder logic and make drawings for
> reference to build documentation.

I'm afraid the most practical way will be by human effort. If you have a simulator for the PLCs, with forces, then it'll be a lot easier, because once you identify the ``state'' coils you'll be able to fix them in each combination and analyze each separately (start with the initial state and only analyze the reachable ones, to save work). You should be able to fairly easily see both the logic within each state and the transitions out of it.

Jiri Baum <[email protected]>
MAT LinuxPLC project --- --- Machine Automation Tools