AB Online edit advice

Hi all.

By my recent posts you will notice I use a lot of Red Lion HMI panels. I am a software programer from way back (electrician by trade) and I still like writing code so I like doing PROGRAMS in Crimson 3.

In most of my cases we have slc500 units connected to the panels. I can easily do what I want using ladder logic but am a bit hesitant to make changes to running syste, I am now going to bite the bullett and have a couple of questions in regards to live editing. My plc stuff is normally down then downloaded as I lack the self confidence to do live stuff but here goes

The system is currently in RUN mode (key switch) and the equipment is running . SO I gather I have to put it into program mode

Can I do this while its running and it wont stop?

As for the live editing, I found a tutorial but my main question is above. I am sure I will have more

First off -

The SLC PLCs have *3* keyswitch positions.
Prog - Program
Rem - Remote
Run - Run

If you put the keyswitch into the Prog position, your PLC will NOT be running.

From the quickstart guide, which I recommend reading http://literature.rockwellautomation.com/idc/groups/literature/documents/qs/1747-qs001_-en-p.pdf

"RUN Position
This position places the processor in the Run mode. The processor
scans/executes the ladder program, monitors input devices, energizes
output devices, and acts on enabled I/O forces. You can only change
the processor mode by changing the key position. You cannot
perform online program editing.
To change the mode to Run, turn the key from PROG or REM to
RUN. When the key is in the RUN position, you cannot use a
programmer/operator interface device to change modes.

PROG Position
This position places the processor in the Program mode. The
processor does not scan/execute the ladder program, and the
controller outputs are de-energized. You can perform online
program editing. You can only change the mode by changing the
key position.
To change the processor mode to Program, turn the key from REM
or RUN to PROG. When the key is in the PROG position, you
cannot use a programmer/operator interface device to change
modes.

REM Position
This position places the processor in the Remote mode: either the
REMote Run, REMote Program, or REMote Test mode. You can
change the processor mode by changing the keyswitch position or by
changing the mode from a programmer/operator interface device.
You can perform online program editing in this position.
To change the mode to REM, turn the key from RUN or PROG to
REM. When the key is in the REM position, you can use a
programmer/operator interface device to change modes."

Now, yes you can perform some kinds of edits online and keep the ladder scanning/exec.

In order to do this, the PLC must be in Remote Run(not remote program).

!!! WARNING !!!

Turn the key gently from RUN to REM, and stop there !!

If you go too far (to the PROG position), it will stop your PLC immediately !!

When you go from Prog to Run, turn the key over to turn and leave it in remote. There are a few reasons why you wouldn't want to do this, but I had them all connected to wifi via a secure unbroadcasted SSID, so I wanted them in remote. If you specifically want to protect against possible change for security, put them back into run.

If you are planning on doing online edits, you want to assign a certain address range for things like binary arrays and integer files so that if you need another address while performing the online edit you can with no issues. More than once I ran into a situation where I couldn't do the work during the day and had to stay late because I didn't have spare memory spaces allocated to store the information for my new logic. That was mostly SLC and MLX though, I did work on CLX and Compactlogix but I can't remember if I could create tags while online.

Don't be scared, just pay attention to what you are doing.

If you are making online edits you have to determine whether you have the potential to cause harm to people or dangerous situations to/for equipment/processes. If so, wait until the system is safe to make the changes. If not, proceed and test your changes often.

We run a lot of conveyor systems here in the four buildings I work in. Our PLCs are left in the Remote/Run position. We often make changes, that don't relate directly to an operator's safety, from one building to another. All motion related editing is done in sight of the equipment we are affecting.

Thanks all. I am currently waiting on production to stop so I can play. As it turns out one of the issues we are having occurred again last night so they are now pushing me to get it all happening

Thanks everyone. I ended up doing it offline but learnt a lot. I need to set up a PLC on the bench and test the above instead of worrying about breaking production machines?

secs said:

Thanks everyone. I ended up doing it offline but learnt a lot. I need to set up a PLC on the bench and test the above instead of worrying about breaking production machines?

Click to expand...

That would be correct. You also need to do some googling. Online edits have a few quirks.

I'd like to add a few comments regarding online edits in Allen-Bradly processors....

There is no way to select which edits are put into "Test Edits" mode, it's "all-or-nothing"....

If you visit a processor/controller that already has edits in, and you didn't put them there, you will have a hard job deciding whether they are correct/safe/valid/appropriate...

a: IF those edits are not being Tested, then delete them. They are not part of the running program, but their presence is a concern because when you do your edits, the pre-existing ones will also be tested and assembled.

b: IF those edits are being Tested, then assemble them. They are part of the running program, and you will be prevented from doing further edits while in Test Edits mode.

I strongly recommend that edits are never left in a processor, and you should complete the job so that no-one else can "trip-up" over them. Remember, you can always copy rungs into an unused, i.e. un-called, subroutine file if you ever need to put them back, or for reference.