SPRINKLER TALK FORUM - You Got Questions, We've Got Answers

Quoted from "Amateur"

Thank you. So that means, I assume, that it takes separate time-keeping circuitry (chips, etc.) powered by either line voltage or battery, to maintain clock and date settings during power failures. Why is this absent in so many controllers when it’s so essential to proper automatic program operation? Is it merely a cost-saving factor?

Yes, an RTC or Real Time Clock is needed to keep the time. An RTC circuit consists of a crystal to generate cycles which is then converts into time, and a memory chip to keeps track of the time. The memory cannot be non-volatile because non-volatile memory chips have limited number of write operations and the chip will be worn out soon if it is constantly written. This is why an RTC circuit typically has a battery and a volatile memory chip. The power to run an RTC isn't much. It can run on a 3.3v coin battery for years, but it too, eventually dies. Then you just replace the battery, tell it the current time and the battery will keep it running.

RTC circuit isn't cheap. That's why many low cost controllers avoid it. They would rather put a 9V battery in order to keep the whole controller alive during the temporary power outage.

Internet based controllers can get the time from the internet so they usually don't have RTC or backup battery. The time only needs to be updated once, right after the controller comes back from the outage, and it can just keeps on running until the power is interrupted.

Quoted from "Amateur"

I assume, that it takes separate time-keeping circuitry (chips, etc.) powered by either line voltage or battery, to maintain clock and date settings during power failures. Why is this absent in so many controllers when it’s so essential to proper automatic program operation? Is it merely a cost-saving factor?

Name another controller on the market that doesn't have a back up battery.

If a controller uses some of its non-volatile memory to store the displayed time, that still wouldn't change the need to correct the time after a power failure.

It happens that the Rainbird SST is a product not offered to the professional trade. Every controller a contractor might buy will have a battery backup that keeps time during power failures.

Thank you. So that means, I assume, that it takes separate time-keeping circuitry (chips, etc.) powered by either line voltage or battery, to maintain clock and date settings during power failures. Why is this absent in so many controllers when it’s so essential to proper automatic program operation? Is it merely a cost-saving factor?

The time settings might very well be retained, by way of non-volatile memory, but the usual desire of controller owners is to never have to reset the clock after a power failure. That is a job for battery backup, and not for controller memory. Controller memory can't keep time.

Good idea,
scercpio, but I'm afraid I wouldn't begin to have the smarts to make it
work. Besides, my present internet provider isn't reliable enough to
depend on for consistent service.

Incidentally, do you (or anyone
else reading this) happen to know why controllers that have a
non-volatile memory for program settings, don't have it for the clock
and date too? Is there some kind of digital problem that way?

Quoted from "Amateur"

Another item: On the box for the SST it says, "No need to reprogram after a power outage. All timer settings are stored in memory indefinitely. No backup battery needed." But I find that if there is a power outage for more than a very few minutes the clock setting is lost. And that effectively stops everything else no matter what. If I'm out of town and the power goes out for even a very brief time, my lawn will not be watered because of this. Am I missing something? Do you know of any controllers that keep ALL the settings, INCLUDING the clock and date, in permanent (or at least long-term) memory?

Get an internet based controller. You don't have to worry about time clock, not even when daylight saving time changes.

Thank you for your information. Looks like a good choice.

Did you click the link and read the description? The model number is XC-600i, while the name given the series is now X-Core. Only a few enhancements came with the name change, so there was no need to come up with different model numbers, and the lithium backup battery part didn't change.

Thanks for the recommendation of the Hunter XC 600 controller. I see, though, that the XC models are discontinued, and replaced by the X-core models. Do you know if these still have the battery backup as you've described? http://www.hunterindustries.com/irrigation-product/discontinued-models/xc