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Web page change by Ladder function or actions


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Hi all,
It is possible to change screen on web server from ladder? I tried do it by action function but I can choose there only HMI screen. I need it to inform remote user about alarms.  
User often have web page minimilized on windows try and he want to be inform about alarms by web page icon blinking,  maximalize web page  or some alarm sound on his computer. How I can solve this issue?

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This PLC works around 1,200 m underground in a copper mine. You can not send an SMS there. Employees do not use e-mails underground. They watch the main process on the screen, our visualization is minimized, they maximize it only a few times per shift. Sometimes our system stops because of an alarm and they do not know about it 1-2 hours.

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Well, redirecting a page from the server side is not something that is done. HTTP works in a way of a request sent from the browser, and then the server responses, if if chrome loaded a page, then the server cannot notify the client to redirect. Off course there are ways to notify the client, but that involves polling from the client side, or using web sockets in order to have an open connection to the server in order to read messages.


Furthermore, a web server serves multiple users where each of them can view a different page. This is why you don't put a "redirect" code in the ladder (simply because you can't).

Redirection implementation must be done on the client side JavaScript code, where for example a status is read via web sockets, and if the status f.e. is Alarm, then redirect the browser to a different page.

Btw, can you put an "Alarm" message on each web page, and have it's visibility linked to some kind of a bit?

This way if there is an alarm, each client (even all of them are surfing different pages) will see the message, which can then redirect them to a different page when a button in that message is clicked. 

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Another option is to view the PLC panel directly via VNC. Either by installing a VNC software, or using some kind of a Web VNC implementation like this one:



With VNC, all users sees the same thing, and the panel can control the screens change (redirect to a different screen when something happens, or show the alarms banner)

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  • MVP 2023

Spider, I initially thought the same as Joe in that you should use a standard machine alarm stack light if the web display wouldn't work.  However, from your description of the location I assume that there must be some sort of ethernet network from the underground location to the screens in use. 

If that is so, then perhaps you could consider using some type of remote I/O that works via network to  relay  an alarm signal that the plc could be made to do.  This would be mirrored at the linked end, thus alerting the users to the alarm.  A gizmo like this as an example, but not as complex given only one I/O needed, might solve the issue.

cheers, Aus


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