What is your mistakes in LD programming?

hi all!
I am a Student in Korea! I am a researcher about Programming Lanaguages! I need your help!!!

my question is "what kind of bugs or problems can make hard to find? in Ladder Diagram" and "is there bugs that frequently found?"

"is there any Software for Finding bugs?"
"if you have that SW what kind of SW do you use?"

tell me your episode about your mistake of programming by Ladder Diagram!!

I will provide very nice tools!! as soon as possible!!
please help me!!

let's make great tool together!!

The mistake most commonly encountered by me is a simple typing error inducing double coil syndrome.

The hardware/software used to find and correct that mistake is made by mother nature and is called a brain. And of course the software for the PLC in question is also used in conjunction.

Regards,

Hi jvdcande! (i don't know how can I address your name sorry
What is the double coil syndrome?
I am a stranger here!

Regards,
--------------------------------------------
Minhyuk, Kwon
Programming Language Laboratory
Korea Technology and Education University

Common mistakes usually come down to typos as suggested, causing:

XIO instead of XIC and vice versa

Duplicate memory address used (One shots, Timers)

Copy/Paste errors - A big one when you have duplicate code for similar sections and you have to change the addresses for each section. Some PLCs have good find/replace routines, some don't.

I agree with Robetmee, the majority of bugs I find are simply due too typo's, the ladder is OK, but the tags have been mixed up. But of course you get the occasional "D'oh, I'm an idiot" type of bugs.

Bugs that occur due to the PLC scan are always hard to find as the ladder looks ok and the tags are correct, that’s when you've got to understand the PLC scan, and understand what the logic is trying to do. That bit me when a program was using math calculations across multiple subroutines....

A double coil is when you have the same output used twice. You cant do this in ladder. If you do, the first use of the output basically becomes inactive.
My biggest issues are typos on the addresses as well. Since plcs make poor use of variables, its easy to use the wrong memory address. Think of writing a C program and only using pointers.

matt

the only grief i see with any code is poor structure and documentation. it takes time to become organized and good in writing code that other can follow. this is not specific to particular language, it applies everywhere.

my own biggest mistake in ladder? well, one day i was a young and inexperienced so on my first job i placed three contacts in series before pulse instruction. everything seamed to work fine duting test phase but then we tried to run production... need i say more

Look again and again

Just goes back to the same thing i was tought by an old guy the day I started programming. grab a piece of paper put down all coils, Vmem ext... have it in fromt of you as you type. then look at it to check. Then look and check, then look again. Then before you finish. Look at the damn thing again. set yourself up to succeed and you will is what he kept telling me. Not sure about all that but I usually dont use the same coil twice lol.