Panelview 7 Time Sync with L81 Logix Controller (Day light saving)

Hi everyone,

I have a CLX PLC which syncs its time (in UTC) with router using SNTP.

Then using GSV I am reading PLC WallClock attribute datatime (not localtime). This UTC time is then sent to remote tags used by the panelview 7.

It all syncs but the interesting thing is daylight saving in the PanelView.

No matter if daylight saving in the panel view is enabled or not it displays UTC time.

How do I display BST instead of UTC on the PanelView but still sync the UTC with the PLC?


Please don't ask me to change PLC code as I am required to sync in UTC. The only issue is displaying the right time on panel view.

I hope I have asked it correctly.

In my time zone, during daylight savings, we are +4 hours, compared to UTC. I adjust the hour based on DST or not and then send out to HMI. Would this be possible?

Hi Ken, thanks for replying

It is not quite possible as I have no control over PLC code as such.

How do the panel view interpret the the PLC time. Does it assume that the remote time from PLC is UTC or with DST?

I'm pretty sure that the time you send to it is the time it uses and displays, regardless of DST. I don't believe the DST setting will take that time and adjust it.

The DST setting simply says that on a specific date, adjust the time by one hour. And it has to actually be powered on to make the change. If it was off when the time changed it will not automatically adjust when it powers on. So, twice a year it does something. The rest of the year it does nothing.

I would have the PV read the LocalDateTime setting and disable DST if your time master or the PLC adjusts for it.

OG

Zero experience with Panel View (PV) here. But here goes ...



I think the problem is that, when the PV is getting the time tags from the PLC, it sees them as values (integers?) and does not "know" they are times. Since the PV considers the tags just a number, it does not to apply DST to it, to convert UTC to BDT (or even to BST the rest of the year).


Often you can re-define, or "cast" the "type" of a value i.e. take an integer and get the program to treat it as a time. I don't know if that is possible here.


Another alternative is if the PV code (do PVs have code?) can access the current time zone it is using; this is typically expressed as +0100 (for BDT) or +0000 (for BDT), i.e. as an offset from UTC, but it could also be a number e.g. 60 (minutes), equivalent to "+0100". Once the PV code has the PV system's time zone in some form, it should be possible to use it to modify the tag from the PLC for display on the PV.


Yet another alternative would be if there was a way to get both the UTC and local time from the internal PV time system, use that to infer the PV-local time zone offset, and add that offset to the UTC from the PLC. Actually in this case, BST=UTC, and BDT=UTC +0100, so if the PV could simply compare the UTC hour to the PV-local hour, and add 1h to the hour tag from the PLC when the compare is NEQ.


Finally, the trigger times, in UTC, for transitions between BST and BDT could be loaded into the PV and used to calculate the offset at any given time.



Again, I have no clue about PVs, how they work, or what they can do, just what I have inferred from reading this forum.


One thing to remember is that times are not numbers in the sense of sequential numbers along a number line, even though they are made up of decimal digits; times are symbols that can be interpreted, according to a cacophony of rules*, to represent offsets in some time unit, typically seconds relative to some base epoch**.


I am saying all of this so the OP knows to not expect that a solution is going to be anything other than complicated, and ignoring some things may be a reasonable choice e.g. the leap year rules for centennials and quadricentennials.



* leap years, daylight savings time, l


** e.g.

• 1900-JAN-01 Microsoft eXcel (also 1899-DEC-30)
• 1980-JAN-01 Micrsoft file systems (FAT, FAT32, etc.)
• 1970-JAN-01 Unix
• 2000-JAN-01T12:00:00 TDB (J2000)eapseconds, etc.