Wincc connection problem

Hi guys!

I've got a quite annoying problem

I've made a program for an S7-300 PLC (cpu314) to regulate the temperatures of fermentation tanks and a few hot water tanks.

This program seems to be running fine.

As an interface, I've used WinCC to make the control of the settings userfriendly.

This interface works fine for all the tanks, except for one.
When I try to change the settings for this tank, the connection to the PLC crashes, the changes aren't written to the datablocks I'm using to store the settings per tank. Even more, after trying to change the settings of this tank, most of the time, after trying to change the settings for this last tank, the connection fails when trying to change the settings on other tanks.
Sometimes the connection is also lost for a few seconds without changing anything. When I restart WinCC runtime, the problems (except with the last tank) are gone.

In the PLC program I used one function block for the regulation of a tank and I use an instance coupled to an instance DB for each tank. The last tank, is just a copy like all the others. I've already tried to delete the data block and delete the network from OB1 and make a new copy from one of the other tanks, did'nt help.

As for the WinCC part, I've already checked all the parameters, whether the addresses of the tags are correct, whether I used a bad conversion routine, whether I used the wrong tags in the pictures.. Can't find a fault.

Has anyone here got the faintest idea of what could be the cause of this type of problem?

Thanks in advance!!

This sounds like maybe a scripting problem. The script engine is single threaded so if any of your scripts hang up then everything that relies on the script engine also hangs up.

Just a guess,

Nick

Thanks for the guess, but I'm afraid the problem is coming from somewhere else, I only use scripting to enable the output of the function blocks. There should'nt be any scripts used for just changing the desired temperature, this is pure standard WinCC tag used, floats connected to real variable in the PLC datablock.

Also, as of this morning there seems to have developed a huge connection problem, the complete connection seemed corrupted, I had to disconnect the pc adapter and reconnect to get my connection back for only a couple minutes.

Could this be a hardware problem? I'm using a virtualised (VMWare) environment, XP on a Windows 7 pc and I'm using a non authentical pc adapter. Driver was also a thought, but then why did it work fine for all the other tanks for all the time..

Is there a way to check the scripting environment perhaps? A log of sorts?

This sounds like a more general comms issue. I run WinCC 7.0 in VMWare for development with WinXP SP3 but I've never deployed one on VMWare. I've had it communicating with PLCs, real and virtual, across Ethernet no problem.

In WinCC Explorer select "Status of Driver Connections" from the tools menu. This will show you the status of all your defined connections. Select the cyclic update box to see whether the connection is stable or not.

Nick

The connection is the core of the problem, it always disconnects for a couple of seconds ( the driver tool window says it's disconnected for a while, then OK again ). My biggest worry is finding the cause of the disconnect. You say this could be a consequence of the scripting server hanging?

Probably not the scripting engine if nothing is running a script. Are you sure you aren't accessing a tag that doesn't exist? you can test the comms link by making a dummy scada system that only has 1 tag to read and write and see if your connection is stable.

One other possibility springs to mind: Are you asking for more data than the PC adaptor can supply over its connection?

Nick

I'm quite sure all the tags exist, though I'll definately check that.
You might be on to something with the amount of data, in the beginning I didn't set the refresh rate that high, but to make it look more responsive I've set them all to 250ms. Maybe I should try to lower the refresh rates and see what it does.

thanks!

Hi Nick,

You saved my project! You're my personal hero for now
Apperantly it was the hunger for real-time data which ****ed up the connection, like you suggested. Now I've had the opportunity to change all the update cycles and the problems have vanished

Thanks again,

Toon

Toon,

I'm glad that you've sorted the problem. We all get our heads stuck into our projects and often need the council of others to see what's going on.

Nick