wonderware simple question.

sapoleon

Member
Join Date
Aug 2003
Location
salta, salta
Posts
315
Hi again.
I have a question about wanderware. Althought, I am not working directly with it.
I am making some modifications in an AB SCL5 routine, and a working partner is making the changes in the wonderware.
What is happening, and the plant operator said it also happens in the plant, is that, for any reason, the wonderware is turned off, or the pc shut down, it sends 0 to every variable that have a connection with the PLC.
That is to say, i am in the middle of a run with the oven (it is an oven control) and if they turn off the pc with the wonderware.... pufff. i dont have any more data in the PLC. cero. nada. no mor CV, timers, security values...

So..., the question. is there some way of avoiding this nasty and unsecure way of operation?

thanks.
 
I'm out of date with Wonder Ware, so I'm just guessing here.

Does it write the zeros on shut down or when the PC is restarted?
Many packages have a write initial value on start up feature, that may be causing your problems.

If you have memory enough in the SLC you could code around the problem.

At the beginning of you ladder have a "status" word written to some register that is compared to zero, if it is greater than zero set a bit true (HMI active). Then in the rest of you logic, instead of writting directly to the timers, counters etc... write values to holding registers, and then move them to the desired location if the HMI active bit is true, else do nothing, and the current value will be retained. It would be much easier if the Wonderware configuration could be changed, hopefully someone more familiar with the software can point you in the right direction.
 
Years ago with an iFix system I ran into the same thing. The data, timer values etc were set via the PC screen and iFix, the plc used this data directly so when the PC was shut down iFix no longer transmitted the values the plc would zero the registers...ie no input

I did something similar to what Ken just said that moved the data into holding registers, which retain the values whether the PC was on or not. I dont think I used the HMI is on bit but that sounds like an excellent method.
 
Let's look at it this way: Some one has programmed this to happen.

Wonderware itself doesn't do anything. There may be a script that executes when you tell WW to shutdown.

There may be a startup script that writes zero's. Or the tags may have an initial value.

There may be some 'heart beat' variable in the plc that is changed periodicaly by WW and if the PLC don't see it, the PLC writes zeros.

Remember, when a PC is turned off, it can't do anything, ie. write zero's.

Try this: pull the communications cable from the PC to the PLC. What happens ? Zero's: then the PLC is doing it.
 
hi, and thanks for the reply.

I think i will just make the bit thing. its something simple, and it won't take me so long. specialy when i allready used a table for the hmi, and then i wright the values wherever i want. (it allways seems to me a good method, and some hmi works better when they can make block transfers).

And, answering the last question, it does not happens if you take the comm cable, and i wasn't talking of just cutting the power off from the PC.

The system works normaly without problem, because in normal operation, no one shuts the pc off, less when they are running, because they do all the monitoring with it.

I will tell the people that works with the hmi to verify if they are giving initial or shut down values to the variables.

once more, thanks
 
sapoleon said:
I will tell the people that works with the hmi to verify if they are giving initial or shut down values to the variables.

Yes, Check this carfully,
Each Tagname in the Tagname Dictionary has a programmable intial value that is used when you first start WindowViewer.
 
ayman metwally said:
Yes, Check this carfully,
Each Tagname in the Tagname Dictionary has a programmable intial value that is used when you first start WindowViewer.

In WonderWare, the 'Initial Value' is used only until the first update from the PLC. It is NOT written to any device, unless there is an explicit (programmed) script to force values to be written to a device.

If you are getting Zero's written to the PLC on Startup/Shutdown of WindowViewer, than the original programmer did that on purpose; either through a lack of understanding, or for some other reason.
 
rdrast said:
In WonderWare, the 'Initial Value' is used only until the first update from the PLC. It is NOT written to any device, unless there is an explicit (programmed) script to force values to be written to a device.

Right you are rdrast, After I wrote my comment, I went to the office and searched for information in the manual and found that Tag's initial value is not written to any I/O device as stated in the manual. So I was going to correct my comment but you were faster than Iam.
 
I've never seen this.

I have two computers with Wonderware, looking at the same PLC5 racks. One is using RSLinx, one is using ABCIP. I have never had a problem shutting down either one. You said all your bits are changing to zero's. Are you sure it isn't faulting the processor. It almost sounds like the PC is acting like a remote rack, and when it is disconnected, it gives your PLC a rack fault. I know if you have a panelmate set up this way, it will shut your equipment down. Unless someone specifically scripted for this to happen, I don't understand it. I agree with the idea of disconnecting the cable without powering down the PC, and see what happens. Keep us informed. It might be a good headsup if seen in the future. This type of stuff is what makes this site excellent.
 
OK, ill send on sunday the news.

tomorow we are going to the site to make some tests, and tune the PID of the ovens.

I will try to check first what is the problem with the scada.

Also, maybe i explained it bad. It is not that all the PLC went blank or only the bits. It was that every value that have a connection with the Wanderware, gets a cero. We are making a recipe, and then send it to the PLC. All those values (and some othes not in the recipe also!) are put to zero. It doesnt matters of it is bit, integer or real.

Tell you more on sunday.

claudio
 
sapoleon said:
OK, ill send on sunday the news.

tomorow we are going to the site to make some tests, and tune the PID of the ovens.

I will try to check first what is the problem with the scada.

Also, maybe i explained it bad. It is not that all the PLC went blank or only the bits. It was that every value that have a connection with the Wanderware, gets a cero. We are making a recipe, and then send it to the PLC. All those values (and some othes not in the recipe also!) are put to zero. It doesnt matters of it is bit, integer or real.

Tell you more on sunday.

claudio

That is definately a fault in your recipe handling. My initial guess, is that you are modifying the recipe setpoints in a script somewhere, and manually writing them down to your PLC.

If not that, and if you are using WonderWare's built-in Recipe Manager, I'd be willing ot bet that you either are downloading the recipe to the wrong UNIT, or downloading the wrong recipe to the right UNIT. (As well as having errors in your recipe unit definition).
 
you were all correct!

well, after arguing with the people that was making the scada modification part, and checking everything again... they start looking for the problem.

and yes... it was that they were sending null values to every connection they have with the plc in the startup of the wonderware.

thanks to all for the comments.
 
sapoleon said:
and yes... it was that they were sending null values to every connection they have with the plc in the startup of the wonderware.
This is a/the reason why many plc programmers do not give HMIs direct access to the PLC data.

Many PLC programmers will set-up memory blocks which the HMI reads/writes from, then in the program you enter logic to move the HMI data to where it belongs. This way you can turn off the move logic and say "See, it's the HMI that is causing the problem" :)


I have no idea why the quote won't work for me.
 
Wonder 'forgot' last value?

You can have W/Ware retain last value, so that a re-boot will not give you the '0' problem.
 

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