Thermostat as Time Master

I have just started to notice my Thermostats had the wrong day set. Everytime I reset it, a couple of hours later it would change back.

I hunted down the culprit using the Diagnostics utility, and it was coming from the PAC which had recently been power reset and was now using the default date of 1/1/2008

I reset it by re-downloading the project with PICED but it has raised a few questions.

I notice I can set the time broadcast interval on the thermostat. Given this device has a user interface for setting the time, it should be the time master over the PAC.

In theory, setting the thermostat update interval to something less than 120m (which is the unchangeable PAC interval) should keep the thermostat as the time master.

But depending on where each device is in its time update cycle, the PAC could broadcast before the thermostat, and thereby regain master status.

So my question is when the thermostat sends out a time update when the time on it is actually changed by the user, will this update be sufficient for the PAC to stand down as time master and let the thermostat assume that role?

And when I am talking about time, I'm also assuming Date, does it react the same way?
I notice the update time, and not the update date is sent when the thermostat is changed, probably because it has no input for the date? In this case how can the correct date be set other than re-downloading the PAC from PICED?

Cheers

Rohan

 

Thanks Ashleigh, that's pretty much what I have done.

However it still leaves the problem of the date.

If you consider the following scenario;

• Complete system power cycle due to power outage.
• Both the PAC and thermostat will power up with default time and date (PAC 1/1/2008, Thermostat unknown).
• The user sets the time on the thermostat which broadcasts a time message that the PAC receives and updates its self, but only the time and not the date, so the PAC still thinks its 2008.
• The user also sets the day, but this does not broadcast any message.
• Sometime in the future the PAC becomes time master again and starts broadcasting time and date updates which is received by the thermostat causing the day to change and align with the date in 2008.
• There is now no way (other than re-program the PAC from PICED) to set the correct date in the PAC.

This causes the problem I was seeing where no mater how many times I corrected the day on the thermostat, a couple of hours later it was changed back by the PAC. This of course causes my heater scheduling to run on incorrect days i.e. a weekday schedule when it is really a weekend.

I'm also not completely convinced that setting the time manually on the thermostat causes the PAC to relinquish time master control, but I need to confirm that.

One last observation is when the PAC does send out periodic broadcasts, it sends both the time and date, I'm not yet sure if the thermostat does date as well or just time. I suspect the thermostat has a clock, but not a calendar, and whilst it can read the day from the date message generated by the PAC, it can't ever send such a message.

Cheers

Rohan

 

Yeah, turning off the PAC broadcasts was my thought also, but I haven't found a way of doing it. Perhaps it can't be done.

I also found from extended logging of the network, that the PAC is actually transmitting date/time messages every 70 minutes on the dot, and not every 120 minutes as I was led to believe from another thread here.

To compound the problem, the thermostats smallest time interval is 90 minutes, that's why regardless of the thermostats capabilities, the PAC will always become time master (at least when there is no other timekeeping device).

It seems to me that any device with a human interface should have priority over one that doesn't and the thermostat should allow date entry, even if all it does is broadcast it once when it is set, just like it does with the time. Allowing just the day to be set on the thermostat (as it is now), is of no use unless it's the only time/date dependent device on the network.

Cheers

Rohan

 

Another option is to provide and connect a 12VDC rechargeable battery backed power supply to the PAC 12VDC BATT input for those home automation installations where you need to allow the PAC to ride through mains outages longer than the 24Hrs supported by its internal capacitor. Then no one including the normal user need worry about resetting the time after a power outage (unless it is exceptionally long). The specified current consumption of the PAC from the 12VDC BATT inputs is only 30mA, so a rechargeable battery backed power supply may maintain the PAC's clock for a considerable period.