Tuesday, September 18, 2012

JeeTherm update

Back to electronics, here are some news of the JeeTherm, as, since the cold season is about to start, it is time to do some tweaking.

It has been working fine since I last touched it, back in January, just before a big cold spell around here! but there were a few little issues, namely:

1: The reported values were the last values read from the boiler, however, if for example the hot water was used briefly, I would see an increase in temperatures, but no indication that the burner had been used. This was easily solved by reporting the maximum value of the status that occurred between radio messages.

2: (and this one was trickier) sometimes the daemon running on the server would stop reporting serial messages from the JeeLink. After spending a lot of time improving the serial and socket handling (written in C) and not getting better results, I gave up for a while. The system still worked, as the calculated temperature was still sent via serial and subsequently via radio to the JeeTherm, only I would get no reporting back. Eventually, the solution I found was to automatically restart the serial port if no message would be received, via serial, for more that 2 minutes. The strange thing was that the serial to the JeeLink and radio was still working, so I thought it could be some sort of air waves conflict. However, since there is a sequence number on my radio message, which is increased even if the communication fails, I would have expected to have larger numbers when communication failed, due to the retrials. But this was not the case, all numbers could be accounted for in the minutes that were missing. So the radio message was coming across, being received at the JeeLink, only not making its way into the serial port.
Just as I was re-flashing the JeeTherm, I googled a bit on the subject and found some reports which led me to think that radio noise on the line, from the FHZ1000PC on another USB port could be disrupting something. Changed the JeeLink to a different USB port, and it appears to have improved...time will tell.

3: The JeeTherm reported every 60 seconds, but, since I have no synchronization, a aliasing phenomenon was occurring. I explain. The setpoint calculation is made once a minute, on the minute, on the server, and sent to the JeeLink, where it waits for a message from the JeeTherm, to reply with the new setpoint. Due to the aliasing, sometimes the radio message came in just before the new setpoint calculation, so I wold be running the boiler with a 1 minute delay from the calculation. Not very serious, but not how things are meant to be :)
So, the solution was to report, in the reply from the JeeLink to the JeeTherm, via the radio,, the age of the data, in seconds. So I measure the seconds since a new setpoint was received at the JeeLink and send this back to the JeeTherm. The JeeTherm then uses this age to adjust its reporting interval in order to always have the freshest data. True enough, after the first radio message, which happens whenever I first turn on the JeeTherm, all other messages come in 5 or 6 seconds after the minute (the 5 seconds delay is on purpose, to allow some leeway, it could be anything)! now I have a basic synchronization implemented!

The code for all this will soon be on Github

Soon, more on the self powered OpenTherm interface, and other Jee's!

Wednesday, September 12, 2012


It's been a while since the last post! But I've been busy nevertheless! With electronics, as usual, but also with a completely different kind of thing: sewing!

Last year we got a new camper van, with a popup roof. We use it mainly to go to sunny places, but, either in the way, or at the destination, sometimes there is the eventual rain, and that got me concerned, as the tent that pops up is made of cotton, and although waterproof, when it rains it gets wet, and if I need to lower the roof with the cotton wet it is not very handy. Not a big problem if you are in a warm place for a few days, as it will dry, but if it keeps on raining...

So, time for a solution. First, a google search revealed that there are a few commercial solutions, which are not more than a plastic enclosure to put over the popping roof to keep it dry. As I almost ordered one of these, the holidays were approaching, and it occurred to me that we have a sewing machine, which I always wanted to learn how to use.

Spent one night getting to know how to run the line through it, and how to get all the different stitches and then I felt I was ready.

Bought a big blue tarpaulin, I think it was 3 meters by 4 meters, layed it over the poped roof, and marked the lines I would have to sew.
The night before we departed I was until 1 in the morning sewing the thing, including some eyelets to tie it down to the car, so no time to check if it fitted well or not. Off we went into one more road trip.

Already in the first week we had an opportunity to use it. The rain was coming, so we placed the CarolTop over the van. It was easy, less than 5 minutes with 2 persons, and it did the job! It fitted, although it needs some adjustments, and it kept us dry.

I now plan to redo it using a lighter weight material, like a tent cloth, and once I do that, and have the right sizes figured out I'll publish it here. Meanwhile, here are some photos, I even made a logo for it!
Needs some adjustments on this side, it is not very tight.

 Here is the logo I made, at 1am.

The eyelets, spread around to allow it to be tied down.

 View from the other side, this side is nice and tight.