How "HMI Wizard" connects controls & indicators to OPC items in DSC module

[Soroush]

Hi,

I want to know how the HMI wizard of DSC module connects OPC Items to controls and indicators

without the use of DSC, I would connect a control or indicator to OPC items by using DSS connections directly from the front panel, through "Data Connection" dialog box, or by generating codes in the block diagram. I'm also familiar with all of OPC examples in LV.

But the problem began when I tried DSC module. I read somewhere in the forum that connecting OPC items to LV by DSS will result in a high overhead when the number of tags increase. Also I read that the maximum number of DSS items are 1000. So I tried DSC, but it seems that DSC is using DSS too!!

I've read in the DSC manual (Chapter 4), that HMI  wizard will run from the shortcut of controls and indicators on the front panel, but it will  generate some code in the block diagram (page 4-1). Is it true? Does it ONLY generate code in the block diagram?

If you wanna say YES, I will shout, OBJECTION! how a tag is related to a control?

take a look at here. from the second part of the code generated by HMI wizard, it seems that there is a connection between OPC tag and that control. Then, LabVIEW creates a DSS URL to update that tag. Is it true?

May anyone clearly explain the process of transition of OPC item to a control. Tag engine retrieves OPC items as tags. then What will happen? Are front panel objects related to tag engine tags or DSS URLs ?

another important question: Is it necessary to use HMI wizard to develop applications?can user generate exactly similar code himself without using HMI wizard?

Thank you for reading this long message!!

[unclebump]

You do not have to use the HMI wizard to access tag data. There are some vi's in the block diagram for reading and writing tag values. These vi's can also read all tags in a group. Using the group name can really help with getting large amounts of data at one time. I wouldn't use the HMI wizard for a large application. I have some DSC applications with thousands of tags in them. From the block diagram, go to all functions, DSC module vi's, Tags section to see how to read/write tag values.

[Soroush]

Hi,

Thank you for the reply.

i'm quite new to DSC. Let see if I've understood the problem by asking two other questions:

1- You say direct connection of tags to controls and indicators are not suitable for application with large number of tags. True?

    If true is it something like limitations of using DSS for connecting tags to VIs that I've seen here.

2- This approach will leave updating of controls and indicators to the programmer. True? any advantage or disadvantage?

    (I don't suppose it as a limitation!)

.

I have also another question. It is not so relevant to the topic, but I'll be grateful if you can help me solving it too. Anyway it is about Alarms & Events which is another main functionalities of DSC. I have some problems with "Alarm & Event Display". This element has some strange behavior on my PC. Surely, you have used it before. Do you have a very simple example that I can check how it works?

Thanks.

With Regards.

[Donald]

"[Datasocket] connection of tags to controls and indicators are not suitable for application with large number of tags. True? If true is it something like limitations of using DSS for connecting tags to VIs that I've seen here?"
Yes/True. Using Datasocket connections to link large numbers of controls to tags causes serious performance issues for the reasons given in the linked post and elsewhere on this forum. The number given for a "large" number varies between 30 and 100 depending on where you look.

"This approach will leave updating of controls and indicators to the programmer. True? any advantage or disadvantage?"
Yes/True. You have to program all updates with Read/Write Tag vi's and others. An advantage that comes to mind is that you end up with a lot leaner code than you'd get using the Wizard for everything. Never use it myself.

"I have some problems with Alarm & Event Display"
What version of LVDSC are you using?

[Soroush]

Hi Donald,

Thanks for answers. let me add a third question. I think the sequence of gathering data using HMI wizard is exactly like this:

   HMI wizard will

[Soroush]

Hi Donald,

Thanks for answering questions. let me add a third question. I think the sequence of gathering data using HMI wizard is exactly like this:

  HMI wizard will

1. generate a logos URL in the Data Operations > Data socket connection of a control on the front panel
2. links the OPC item, accessible as a tag in Tag Engine,  to the same logos URL.

  Is this sequence True? If yes, when someone buys DSC module and uses HMI wizard to connect OPC items to VIs, he/she gains nothing. because without using DSC module the programmer can connect OPC tags to VIs using OPC type URLs in data socket connection. What's your idea?

I'm using ver. 7.1 and I've also applyed the latest fixes, but I can't still understand what's the matter with "Alarm & Event Display".

Regards.

[Donald]

Hi Soroush,

Yes, that's pretty much the sequence for invoking the HMI wizard on a front panel digital indicator/control as described in Chapter 4 of LVDSCv7 manual (Chapter 5 for LVDSCv6). It generates block diagram code which uses Datasocket.

"If yes, when someone buys DSC module and uses HMI wizard to connect OPC items to VIs, he/she gains nothing because ..."

Well, he/she gets the Citadel database ... and if you invoke the HMI Wizard on an XY graph you get code automatically generated to an graph historical trend. Invoke it on a boolean you can generate code which monitors a tag alarm status ... and I think there's some way of invoking it to generate a Read/Write Tag in a loop, although I couldn't find it when I tried briefly.   But I understand why you bolded "nothing".

In my opinion, the HMI Wizard is useful only for users who are beginners with LabVIEW in that it allows them to see some simple results quickly. If they have small needs, they don't ever have to expand beyond it. There's a "Panel Wizard" as well which can be invoked on a Boolean control, but I think most LVDSC users with a bit of experience just write the code themselves.

Regret that I can't help with your Alarm&EventDisplay problem as I'm a version behind you (and rarely use it).

[Soroush]

Hi Donald,

Thanks for clarifying the role of HMI wizard.

About AE display: The most important thing that got my attention was that you said you rarely use it! Why? is it just another feature for beginners & fast development? I've read some threads in the forum and it seems that even people who are successfully using AE display are complaining on the lack of flexibility of it.

Are you saying that for a professional project, I shall design something like AE display by myself having costumized features? Are you doing so?

If True, I think my True-False questions will end up by now

Regards,

[Donald]

Hi Soroush,

" …you said you rarely use it! Why? is it just another feature for beginners & fast development?"
No/False. I don't think the AE display is just for beginners.
I don’t use it because I don't need to.  All alarms/events that I deal with are configured in the PLCs controlling the individual processes. No DSC tags have alarms enabled. My "Alarm" tag is just 16 or 32 collection of the PLCs alarm bits which gets logged upon change with all the other tags. Works for me, allows me to provide an alarm interface that my colleagues are used to after 10 years, etc. etc. Your mileage may vary.

"Are you saying that for a professional project, I shall design something like AE display by myself having customized features? Are you doing so?
No/False.
I think you should start a new thread with a description of what you're trying to do with the AE Display and the problems you're encountering ("strange behaviour" needs to be detailed).  Much/all of the functionality of the AE Display probably could be programmed by you by others means, but why do it if you don't need to?

Good luck.

[Soroush]

Hi,

Thanks both of you, Donald & unclebump for replies.

I wish I could see an example on AE display. That would speed up my work. Anyway I'll try it.

Let me postpone starting the new thread till I've tried a little more.

Goodluck.