Dear all,

After having made a lot of trials, I'm going back to you because I don't see how to manage my issue.

In order to explain it in a much clearer way, I have designed two watchdog grafcets :

• the first one in handling only Digital Values (no interactions with real world)
• the second is the exact copy of the 1st one. The only difference is that inputs and outputs are directed to a Siemens Logo module (modbus communication)

The frequency of the watchdog is supposed to be 1 second.

I run the two grafects at the same time.

On the first one, everything is ok: we can see that on the attached picture.

On the second one, (and I can hear the switches from the modules), the response time is very erratic, as you can see on the record.


Does anybody have an idea ? because for my application, Watchdog is mandatory. With such results, the safety is not ok.

I'm a little bit confused because Proview seems to run in an industrial environment for a while. I'm sure I have made some mistakes somewhere, but I don't see where...

Thank you again for your support.
Best regards,
Raphael

Hi Raphael,

I can't see anything wrong with the Grafcet sequence.

One error could be that the output (or input acually) is also written from some other PlcPgm. To assure that this is not the case it's possible to switch off the execution of PlcPgms by setting ScanOff in the window object under the PlcPgm object. By doing this in all other PlcPgm you can assure that they are not interfering.

To examine what happends in detail you can use the Xtt logging function in System/Logging. Collect interesting signals and attributes with Ctrl+V, for example the di, do, step activity (Status[0]) etc, insert them in he logging entry and set a scantime at least two times faster than the PlcPgm scantime.

/Claes

Hi Claes,

Thank you very much for your explanations. Thanks to you, I think I now have identified the root cause, but not solved the issue at all.

In fact, after having followed all your recommendations, I also tried to simplify the program:

• the PLC now only control the output relays of the Siemens module, with no feedback
• I removed the "ReadDiscreteInputs" modbus module from the configuration.

And now, the output relay does exactly what it is supposed to do (thank to the xtt logging, I can ensure that it works perfectly).

The only point is : Why am I not able to send instructions and read the inputs at the same time ? Is it linked to the Siemens Logo! module ?

Do you have any idea ? for your information, I was trying the 8 digital inputs at the same time...
thank you for your support.

Raphael

Dear all,

I finally found what the problem was : in fact the Siemens LOGO seems not to be able to manage several requests at a time.
Putting the parameter "SingleOP" to YES in the Modbus slave configuration solved the issue.

Raphael

Salut, je cherche à connecter un raspbery avec proview sur un LOGO!8. Pour le moment j'ai proview sur mon PC sous mint pour les tests, j'ai suivi les tutos pour m'habituer à proview qui n'est pas simple de prise en main

Je n'arrive à rien, je ne vois pas les connexions ni dans un sens ni dans l'autre.. A part le ping vers mon ordi je n'ai rien, Je voudrais réussir à connecter quelques entrées et quelques sorties mais je suis totalement perdu

Si tu as quelques pistes je suis preneur

Merci