Adjusting RTC for DST?

Sorry if this question has already been asked before!

But I'm wondering if anyone has already come up with a good idea for adjusting the RTC(Real Time CLock) in a PLC(my case a Unitronics Vision 280) for when DST(Daylight Savings Time) changes.

Now I know that it changes on the first sunday in april at 2:00am and then changes back on the last sunday in october at 2:00am.

Thanks
Deke

As you may be know Unitrinics are Isreali company with pretty unique
product.
I personaly dont like them because I had problems with them in the fast.

But the idea when you need to change the time just ues move command
to the hour register.

1.comper date and hour.(Daylight Savings Time)
2.move the hour+1 to huors register.
3.comper date and hour.
4.move the hour-1 to hours register.

I hope I helped you
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Adjunting RTC

I have this working in the Modicon Micro that controls my house.

In Europe, the hour changes at the last Sunday of March and then changes back on the last Sunday in October.

I made a simple program

IF(Month_day>=325 AND Month_day<401 AND Hour_minute=100 AND Day_of_week=7)OR(Month_day>=1025 AND Month_day<1101 AND Hour_minute=200 AND Day_of _week=7)THEN
SR1;
END_IF;

Then, at SR1 I add h256 to RTC in March and set one bit (%m0, p. ex.) if %m0 is not Set. In October I subtract h256 and Reset %m0 if %m0 is not set.


I only moved to this house in December but that worked fine in March. I’m waiting to the end of the month to see if it works again

Hope this help


João

I do this at the plant using RSVIEW. I set up a VBA script to run twice a year. In the fall it sets the PLC clock back an hour in spring it moves it ahead an hour. The thing I have not done yet is write to code to make the VBA script figure when the daylight savings time code is supposed to run. I just go into RSVIEW twice a year and say run thic code on this date at this time. I guess it is about time to do this again. I was also thinking about doing this just in the PLC but I dont like the idea of at 2:00am set the clock back to 1:00am then if I dont set a flag saying I did then it runs again every hour all night. Not a big deal I am probably just lazy.

Well I figured it out on my own... If anyone is interested I'll post the PLC code.

Now I also took in account that if the PLC was turned off when the DST has changed, that it checks for this when first powered up!

Yes I do have a bit latched when in DST mode.


Thanks
Deke