How how have you managed to configure a basic HMI to constantly try and increment a tag? Cyclic triggers are not available for basic HMIs.

KenNatton

Hi mystery user 7873714

This is actually something I was looking at very recently, after I stumbled on something from pursuing another thread, actually on a completely different topic.

You have to understand why this is a particular challenge and something of an age-old topic – certainly for me. I have discussed this exact problem with colleagues relating to various brands of PLC on several occasions over many years. The heart of the problem is that, if the PLC is in stop, clearly it cannot process any code or make any changes to the status of any variable that the HMI can pick-up to drive a display of PLC status. I have seen a few different techniques used, one of the obvious ones with Siemens PLCs is to use the OB routines that can be executed when the PLC goes into stop. But, one way or another, none of them prove to be completely robust and totally reliable.

And then, recently, as I said, I stumbled on this technique which I have run some tests on, and seems to be pretty good. I have not yet used it in earnest, but my intention is to do so, and I will see in the coming weeks and months just how dependable it is.

So the heart of the technique is to set up an HMI local integer tag that the HMI is constantly trying to increment, but which is constantly being reset to zero by the PLC. If the PLC goes into stop for whatever reason, the HMI will succeed in incrementing the tag, and that is what drives the display of PLC stopped or PLC running. You can then even set up another HMI local integer tag working very similarly, but used to detect if the PLC and HMI are offline, and that works even if the PLC is in stop. So you understand, your display can show ‘PLC Stop’ – online and PLC in stop; ‘PLC Run’ – online and PLC Running; or ‘PLC Offline’ – no comms between PLC and HMI, this last case working regardless of the PLC status.

Sound good? Inevitably, it’s not quite so straightforward. To work the best way, the detection of PLC offline relies on the HMI to be able to do scheduled tasks. Comfort panels do scheduled tasks but basic panels do not. You can still indicate PLC offline on basic panels, but it requires a user action to test for it. PLC stopped or running works perfectly on both basic panels and comfort panels.

If you, or anyone else is interested, I can attach a copy of my test program that shows how I, at least, implemented this technique.

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Split from TIA Portal V15 Show PLC status.

Zed1

 How how have you managed to configure a basic HMI to constantly try and increment a tag? Cyclic triggers are not available for basic HMIs.

What is your aim?

It is possible to create a lamp on the HMI that is triggered pulsed by the PLC. A bit tag from the PLC can be toggled at an interval of 1s, or even 2s. The tag on the HMI side can be set to a 100ms update rate which is continuously updated (instead of when only used).

This lamp will indicate if the PLC is connected and in run mode.

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Bonus: the opposite as you asked
Telling the PLC that the HMI is active is also possible. A life bit is provided in the area pointer of the HMI.

My aim is to mimic the PLC LEDs. I read this topic and created post Mimic S7-1200 LEDs on basic HMI.

I think the method you suggest would enable dynamisation of an object to change colour, indicating the PLC is in run if the colour is changing. I don't want that - I want to mimic the RUN / STOP LED, so steady green when in run and steady amber in stop.

Closed cause question posted twice.

The second thread with the subject Mimic S7-1200 LEDs on basic HMI is published within the conference SIMATIC WinCC (TIA Portal).