Webserver text field refresh rate

[FilipM]

Hi, 

Im making appilication to control oil burners in industry furnace and Im having problems with my HMI over Webserver. All text fields  just like for example "Timer box" refreshes over 1 second. Right now Im using Chrome browser to work with my HMI. Is there any chance to force (or other way to view) webserver HMI to have shorter values update time like 0,1s?

Thanks

[Joe Tauser]

I don't think you're going to get high speed updates on a web page.  One of the Creators can chime in on this.

Have you tried the VNC server?

Joe T>

[FilipM]

Yes, but VNC (as far as I know) offer weaker control over priviliges and display. We want to configure one HMI screen only for display and other for control purposes. Both should be accesable in the same time on two or three different machines. Im not sure if VNC method can fulfill these requirements.

[AlexUT]

1. @FilipM, What refresh rate will be comfortable for operator eye and will be readable?

You can add to this some network delay, and bear in mind that PLC main task is to manage process, but not fast refresh tags at web page(s) and displays.

And there is no obligation from LAN/WAN/Internet not for delay, not for jitter, not for retransmissions, etc.

Believe that optimazing requirements is a way to make a good project design.

Experts - tell me know if I am wrong.

2. You published your post in "We're Listening".

Please tell us what PLC model do you use (I suppose - UniStream) and we will move post to proper topic.

B.R.

 

[FilipM]

Hi

My PLC model is USC-B10-TR22 and I understand that process control have highest priority, but Im also concerned about usefullnes or friendliness of HMI (in this case virtual).

Web server over ethernet seems eneough to fulfill our requiments  and its more flexible than physical HMIs but, to be more precise, some dynamic analog values in our process must be controlled by operator and the problem is operator see changes 1 second after touching button. While using webserver toolbox premade gauges we can see analog changing value indication, but with textboxes values refreshing time is ~1 sec.  which of course not correspond with real delay in vHMI - PLC path.

[AlexUT]

@FilipM,

If display, even virtual make variable/tag refresh at each scan (scan time may be number of mSec), will lead to creating queue of messages, which make effect of delay.

This means, that all created and sent messages are not lost and each one leads to variable/tag refresh.

Solution:

To display result in readable form, use intermediate variable to store counter samples each 0.1 Sec.

This make less queue length and it will show variable/tag with no delay of 1 Sec.

This solution is much simplest than requirement for fastest refresh.

Test it and you will fell difference.

B.R.

 

[Gabriel Franco]

VNC will meet your requirements. You can acces the PLC from multiple clients at the same time (but they will all see the same screen). It is also possible to configure two types of access: full control or view only.

Delays depends on number of elements of each display.

[FilipM]

Thank You, 

Ill try this method tomorrow.