Basic logix 500 questions

For the past 6 months or so, since I discovered this forum, I have been realizing that my tech school education just touched the surface of logix programming. I feel I know just enough to be dangerous some times.
Any way I was reading a post by Ron about online programming. In school we did everything offline. Everything around the plant is on 24/7 so I don't have a processor to play with. My question is if I want to add say an input to a rung and I do it online What happens when I download to the processor? What happens when the test functions are used? I have not used the single or continous functions yet. Will they turn on real world I/O etc? Also, will these edits now work in the program or do you need to "assemble" the edits. Could someone walk me through how offline editing is don. Finally, I don't know what the drop down arrow box is about that has "raw" or "^A" is all about.
Thanks to anyone who takes the time to answer.

A quick overview.
Accept basically just checks if the logic is acceptable to the processor, ie that you dont have an input at the end of the rung etc.
Test actually loads the edited rung into a separate bit of memory and actually runs the logic. You can untest from here which drops the program back to the original logic.
When you are happy that it works the way you want it to work, the assemble command makes the test rung permanent and deletes the original rung.
I seriously suggest getting someone with experience to step you through this at your factory. You can cause some very serious damage.
Regards Alan

Greetings sheirj,

coincidentally I just finished answering most of your questions in this post ... read through that and see if you have anything that still confuses you ... please post again if you do ...

as for:

I don't know what the drop down arrow box is about that has "raw" or "^A" is all about.

Click to expand...

is this what you’re talking about?

if so, this is a VERY HANDY “text search feature” that searches through your ladder logic program ... there’s more to this story than I have time to cover right now, but the notes in the picture should help get you started ... the best way to learn about this particular feature is to experiment/work/play with it ...


by the way, if “raw” is in the box, then someone has recently searched the ladder logic looking for the word “raw” (probably in an address comment) ... the “^A” code means (basically) that someone has recently searched for “all types of rung edits” that were existing in the program ...

finally, you also said:

I have been realizing that my tech school education just touched the surface of logix programming.

Click to expand...

I wish I had a nickel for every time that I’ve heard that particular song ...

Allen,
Yes I can do some serious damage. I found out I am fully capable of that. Actually, I am in a pretty safe environment. If I make a mistake It usuallly just causes a feed rate problem and when you are making 5 million gallons a day of water you can make up the difference. I once broke into the flow loop and we quit feeding some chemicals for a while but ultimatly had no effect on water quality. Probably a good fit for me since I am right out of school and have no one here to help or mentor so I do make some mistakes. Hence the value of this forum to me.

Ron,
Once again you have have shinned the light on another dark area for me. Got a chance to use it this morning. I just used a spare output and a bit then removed them. Worked great. Much easier on the system, pumps don't shut down etc. Now I know why I got some strange looks when I would download a change and everything would stop and restart. Makes me look more professional.

Thanks again for all your help
Shierj

Hi, Just an update for you (with thanks to Ron who has forgotten more about SLCs than I will ever know).
When you press "accept" the rung is transferred to the PLC. It is not in use but is there.
Regards Alan Case

I take it from your last post, Sheir that you realize online editing doesn't always mean you have to download to the processor. In fact, online editing prevent you from having to in most cases. If you are adding a bit or integer file or expanding an existing file, say from 50 to 100 integers, then you must download. But just to add or edit ladder rungs doesn't require downloading.

EDIT: I went back and read Ron B.s post and realized we covered some of the same things. I didn't mean to trample on anyone's toes.

Thanks Guys, I think I got a handle on it now.
I think I am going to go back to my school and ask why we never were taught online programming. I remember some students overfilling a level trainer because they stopped the processor to edit. I would think that would be a flag to the instructor. hmmm
Well thanks again for all your help
Happy programming!

I'm sure I'm not alone when I say if I had to stop a line or process every time I edited a program, I'd have been fired long ago!

Greetings sheirj,

I think I am going to go back to my school and ask why we never were taught online programming.

Click to expand...

be gentle ... there could be a VERY logical reason for that ... the PLC labs in many (most?) schools are equipped with smaller processors such as the MicroLogix platform ... these are less expensive than the SLC-5/03 that you’re currently using - and they don’t allow online editing ... (exception: I haven’t worked with the brand new MicroLogix 1100 systems yet - but I understand that this MicroLogix model does allow online editing) ... anyway ... if your school’s lab wasn’t equipped with “online-edit-capable” processors, then the procedures that we’ve been discussing in this thread would probably never have come up for discussion in your classes ...



but then there is another reason ... I used to work with an instructor who would insist that his students ALWAYS go “offline” and make their edits - even though the equipment was fully capable of doing online edits ...



the reason that he gave for this policy was that “online” edits are too dangerous ... remember, the machine is usually RUNNING! while we’re doing this ... so for safety’s sake, he absolutely outlawed online edits ... no sense in encouraging the students to pick up “bad habits” in the lab that could create problems down the road ...



now I’ve learned over the years that debating “safety” issues can get you into a lot of trouble ... so I am NOT going to enter the debate over the safety considerations involved in making “online” edits vs. making “offline” edits ... but I’m just going to offer some “food for thought” along those lines ... everyone is free to make their own decisions about what “fits” in their particular situation ...



I was teaching a class of students several years ago, and one of the students was the plant maintenance foreman ... three or four of his workers were also in the class ... after I had covered the basic ideas behind how to make “online” edits, the foreman asked if he could speak to the class for a few seconds ... his remarks went something along these lines: “I appreciate Ron showing us how to do these edits online - but I just want my guys to remember that at our plant we don’t allow you to use these procedures. For safety reasons, all of our edits MUST be done offline.” ... when he was finished, I said something along the lines of: “OK, all of you Acme guys probably will never need these steps, but we’re going to cover them anyway for the benefit of the other students.” ... and the class continued ...



later as the students were leaving for lunch, I drew the foreman aside and started a very gentle and polite conversation ...



Ron: “So your plant does ALL of their edits offline for safety reasons?”

Foreman: “Yep. That’s been our iron-clad rule for years.”

Ron: “Well, after you do the offline edits, what do you do next?”

Foreman: “Then we download the modified program and test it out.”

Ron: “So you put the machinery back into operation - and see how it operates with the changes in place?”

Foreman: “Sure. How else can we test it to see if the changes work?”

Ron: “Well, I’m just wondering about something. Suppose that you’ve made some type of error while doing your offline edits. When you finally download the modified program and test it out, how is that any safer than testing exactly the same program changes during an online edit?”



you could see the wheels turning behind his eyes ... in a few seconds the light bulb over his head came on ...



after lunch the foreman made the following announcement to his workers: “I want you guys to pay careful attention to the online edit procedures for the rest of the class. We just might be needing these procedures from time to time.”



once again, I’m not advocating the use of online edits instead of offline edits ... and I’m not going to debate the safety issues involved in either method ... but in my classes I make absolutely sure that everyone knows how to use both procedures ... and I do everything in my power to make sure that each student fully understands the safety implications involved in using each method ...



when you think about it the following way, I suppose that you COULD make the argument that the online procedures are actually safer ... suppose that your PLC is in the “Remote Run” mode ... you make an online edit ... you “accept” the rung ... you “test” the edits ... but suppose that you hold off for a few seconds on doing the “assemble” edits step ... then during the “try-it-out-test” you notice that things aren’t going exactly the way you planned ... in the online edit mode (usually) all that you’ve got to do to get back to where you were is to “untest” and “cancel” the edits ...



now on the other hand, suppose that you’re in the middle of testing those same edits but you had made them while offline ... now if you wanted to get back to where you were, you’d have to pull up a copy of the original program (hope you've got a backup copy handy) - and then download it back into the processor ...



now if that’s a safer procedure in your particular situation, then by all means use the safer procedure ... but in a lot of cases, the “offline-edit-download-run-and-try-it-out” process doesn’t seem to be much safer (if any) than the “online-edit-accept-test” procedures ...



and along the lines of Rube’s statement:

I'm sure I'm not alone when I say if I had to stop a line or process every time I edited a program, I'd have been fired long ago!

Click to expand...

in some plants, just shutting off the equipment to allow a program download can be a time-consuming process ... (days in some continuous-process plants)...



and now back to my instructor buddy who wouldn’t let his students do any online edits - ever ... he always maintained that his only reason for this policy was due to the safety issues involved ... but just between you and me, this particular instructor wasn’t known as being a workaholic ... personally, I know that teaching online edits is quite a bit more demanding than showing people how to do it offline ... so ... maybe he was just taking the easy way out? ...

Wow! another very informative reply by Ron.
The processors we all used were 5/03 or higher. I wonder if he knows how. He was a very knowledgeable person but definatly not a people person. Not to rant but he would usually start class by saying "get to work" and then disappear. He told one student if he never sees his face in his class again he would give him a C. Maybe he was too busy writing his book. We got a copy and burned it at my graduation party. Too bad because he has great knowledge.
Anyway, I understand the safety issue but as you stated in your reply, If it is wrong its wrong. Either way you could do damage.
Thanks again
Shierj