More OpenTherm

Back from holidays! and with good news - I managed to communicate with the boiler using OpenTherm!

If you remember, the last time I managed to communicate, however, the boiler was not doing what I was telling it to do, namely, to heat up the central heating water to 35 degrees, instead, it was displaying an error state, and not a very informative one, in the small display.

Here is a picture showing the oscilloscope trace, where both the master to slave and slave to master burst messages are visible.

Since I had not implemented a decoder for OpenTherm, to analyse the reply from the boiler, I could not know what the boiler was complaining about. So I came up with a solution: I installed the OpenTherm arduino decoder found in the palebluedot site, and commented my emitter directly to the arduino with the decoder. As expected, the message was going with an data error. After finding a couple of bugs in my manchester encoder, I managed to get a correct message across.

Time to send the message to the boiler.

Another trip to the attic, and the boiler received the message, but didn't start heating up, but also no longer went into the error state. A careful read of the protocol, and I realised that I was disabling the CH when sending the message with ID=0. At the end of page 24, one can read that the "CHenable bit has priority over the Control Setpoint". So, another change to the message, another trip to the attic, and success!! The boiler started up, heating up the central heating water to the set temperature of 35 degrees!!

Next step is to implement the decoder in the same JeeNode, and the make a little PCB shield. After that, it is a matter of software, both in the JeeNode and in the server, to implement the communication layers, and of course, the much awaited and though of PID controller!

OpenTherm success

I have been waiting for someone to connect an arduino to a boiler using OpenTherm. Someone has managed to use some circuit and an arduino to listen, but I want to be able to send messages as well.

So, I read and reread the OpenTherm standard which is available, v2.2, and have been cooking a solution.

The thing is a current loop, so to read it, one doesn't need more then an optocoupler. to control it, one has to vary the voltage between around 5V and 17V, but the boiler provides a fixed current. So, if the current is fixed and you want (have) to change the voltage, you need to change the resistance.

My plan was then to use two optocouplers, one to read, and one to write the messages. Here is my circuit:

I used a 4N27 and not a 4N35 as in the diagram. The boiler connects at the terminals at the right, and the bridge is also an integrated bridge. The boiler side resistor is 2.2K and 1W, so not the normal low power resistors!! The arduino resistor is a 220 to drive the led.

I haven't yet connected the output of the other optocoupler, the receiver one, but that should not be much work, the worse is to detect and decode the pulses, but for that someone also wrote a library (see link above).



And the good news, is...it works! or at least I think it does...

I tried first doing a PWM control, corresponding to OpenTherm lite (OT-) as defined in the standard, but my boiler doesn't seem to support that, so I wrote a manchester encoder, and sent a message to the boiler, and the boiler replied. It uses interrupt driven code to deliver the pulses with the proper timing.

I haven't actually decoded the reply yet, or sent any real commands to the boiler, I only saw the reply from the boiler in the oscilloscope. Images and code will follow soon...the camera had no battery to take a picture of the oscilloscope in that moment of glory!

Home dashboard V2

Since the last post, not much has happened, but I have been busy with the dashboard.


I made some changes to it, so here it is:

The left dial is the electricity consumption, and the one on the right is the gas. They go from 0 to 5, so at the moment I took the snapshot, there was a very high electricity consumption - vacuum cleaner :)
The pointer indicates the instantaneous consumption, the white number the total for the last hour, the blue number (month) is the running total for the last 30 days, as well as the cost, which is simplz the number in blue multiplied by the average cost.

It is all made using HTML5 canvas, and AJAX (I think...). On the server side, php does the job of answering the requests. The thing updates every 5 seconds, and the temperature updates every couple of minutes. The agenda fetches data from google calendar and does that only at the moment the page is loaded, so the plan is to reload the page every few hours (my agenda hardly changes...)

I now have to polish it a bit, to display properly in portable devices - it works in android 2.1 - and to lighten the load on the server...my database structure is far from ideal, and the requests take a very long time to process - 1 to 2 seconds - when most data doesn't change that fast.

Home dashboard

Here is my new dashboard for the house! this built with HTML5 and AJAX technologies (sorry if any of the terminology is incorrect, but it's hard to keep up with all these mash ups :)

This is a project that I have been thinking about for many years, and now I finally found the technologies to get it all together! And especially, the touch screens are becoming affordable, with all the tablets around, the final piece of technology will come together and I can finally stick a touch screen somewhere in the house, showing what the house is doing, and allowing control!

It became possible when I found out about RGraph, I then spent a night or two getting some graphs together, but they didn't look very slick, so I investigated, and I found a few nice dashboards, and then I almost copied one of them, this control4 energy, and after one night of iWeb, vi, php, and HTML5 coding, I got to the result above.

I think it looks really nice! I still have to make the whole interface language better and get labels closer to the fields, and that kind of usability stuff going on. This is an AJAX thing, fetches data every few seconds, and adapts the graphics and displayed information. The other pages, for gas and agenda, are not yet ready.
I am particularly proud of the pointer, which moves smoothly between the values, and keeps waving when it reaches a value, mimicking a real pointer on a car or analog meter - it's a pity I can not show it here...maybe I will do a movie...or put the html in here one day.

Hope you enjoy it!

As for the batteries of the RFID lock, they didn't last nearly as long as I had expected, so I am now powering them from a small adapter...will still consider powering them from a solar cell connected to rechargeable batteries.

RFID lock: ready! finally...

After years and years of thinking, googling and trying things out, I finally managed to finish my RFID lock!

So here is what it is: I have a door from the outside to the garden, which I use to get the bikes in the garden. There is a small slope leading to said door. I find it pretty annoying to have to go down the slope, get the keys out of the pocket, unlock the door, get in with the bike, put the bike in the shed, get the keys out again, lock the door. Especially in the rain, and in the winter, when all this implies the further step of taking the gloves out, and finding the lock hole in the dark.

For a long time I did not lock the door. I simply left it unlocked, but that always felt like a big security risk, so I started locking it. But in the back of my mind there was always the will to get it automatic. At work I have a badge which I use to get all the doors open until I reach the bike shed, and this is pretty easy to get out of the jacket pocket, even with the gloves on, so why shouldn't it be also easy to do at home.

So here is the final solution:

- a JeeNode, for wireless connectivity;
- a RFID reader module for Mifare cards, from Stronglink, an SL30
- an Abloy EL561 electronic lock (this is the expensive part of the project)

The RFID module is pretty nice, it uses I2C for communication, and can be put into sleep mode. Stronglink has a pretty good service too! quickest delivery - modules arrived in 3 days from Beijing - and when I had a problem with the power saving mode, they couldn't help me, but sent a whole new set of modules to replace mine, in case it was a hardware problem. The sleep mode problem is still there, as it doesn't quite work as expected, but I managed to get it to work in a procedure that is close to voodoo :) change something in the code and it mysteriously stops working. I wrapped it in FIMO to make a module to have on the outside, since the range on the sensor is not very big - about 4cm.

Then the Jeenode. It controls the whole thing, and when the card number is an authorised one, it closes a SSR relay, which provides 12V to the lock, thereby enabling it to be opened just by using the door handle. It also sends a radio message to the server informing which card was used. It does not yet using central authorisation, as I will need to get encryption going on for that. The Jeenode sleeps for most of the time, but wakes up every 500ms to check for a card, it then wakes up the SL30 module, checks for a card, puts the module back to sleep and sleeps again. It is now powered by 4.5V, so lets see how long before the batteries need replacement. I am hoping they will last a few months, but I will be glad if they last 1 month...

And the lock, is a pretty nice lock, which locks automatically, so the door is always locked now.it also provides a lot of signals, like cylinder used, handle down, door open, and a few more I think, but I do not yet make use of them. I want to, but that will be the next hardware iteration.

There are a lot more details, but those are for next time.

here are a few photos:

The electronics box, with the Jeenode, 12V battery for the lock, 3xAA for the controller, and the cables coming in, one from the lock, and one from the sensor outside the door.


The sensor on the outside.

Heating season report

The temperatures around here have been souring, although today it is back to normal, with low temperatures, and the threat of a storm approaching, but I consider the heating season officially closed!
So here is a final report of this season - 2010/2011.
Last year we started pretty early with the heating, in August, due to the birth of our little daughter, and the fact that the end of August was pretty cold already, at the end, with the last days averaging less than 15 degrees.
After that, the boiler didn't stop working, during a pretty long and cold winter, with snow for about a month, and an average December temperature of -1.1C, when it is normally 4.0C.
Last year we got a new boiler installed, a new condensing boiler, so I was very curious to be able to compare the performance of this boiler to the previous old one with pilot light. Since that one spend about 0.7m3 a day just on the pilot light, I guess I would have about 21m3 a month less than usual, which, for the 7 months of heating translates to about 150m3 less, and about 90 euro of gas (about 60 cents per m3).
But, I could not do a proper comparison, since, with the arrival of the baby our habits changed a lot. First, the overall set point was raised by 1C, from 18C to 19C; second, my wife stayed at home for most of the winter on maternity leave, so the house was warmed the whole day instead of the usual night only; third, and similar to the previous, we spend most (if not all) days/nights at home, whereas before we were going out quite often for dinner, movies, parties...

With all these to take into account, I knew that it would not be easy to compare. But anyway, here are the values, and a small analysis (sorry for the bad formatting, but couldn't figure it out...):

month	Spent	Predicted	temperature
August	38.01	59.553	16.8
September	65.75	121.541	13.6
October	150.74	217.062	10.4
November	309.34	413.124	5.8
December	523.18	837.144	-1.1
January	415.31	537.14015	3.5
February	350.72	475.666584	4.6
March	252.13	398.224854	6.1

I did not include April although for almost half of the month the heating was still on.

This leads to a grand total of 2105.18m3 spent, against a predicted (formula based on the first year of occupancy of the house) 3059.46m3. So we spent 69% of the predicted gas consumption.
The other years this value was around 55%, so there was a large increase in our consumption, although, the comfort levels were increased and the time the house was occupied also increased significantly. Maybe it would be a nice idea to make some statistics on this, since I have all the data available.
I cannot however conclude much about the improvement, since the usage conditions have changed so dramatically. I am nevertheless convinced that if I had kept the other boiler I would have spent more than the prediction.
So overall I am quite happy with the result. Next project is still to get a PID controller going based on opentherm (maybe starting with opentherm lite) to try to get the boiler to operate in its ideal range. Now it is still on/off control, which isn't the most efficient. I do try to run the boiler efficiently by limiting the temperature of the water to 55C whenever the outside temperature allows it.

Thermal camera

This past week I got a hold of a nice infrared camera! or thermal camera or however those things are called...

Due to unforeseen circumstances, however, I didn't have as much time to play with it, as I had foreseen, but nevertheless, I managed to take a few snapshots.
The weather has also been pretty warm (as warm as it get in Holland...) and so it was difficult to get the ideal conditions to identify heat leaks.

One of the main purposes that I was interested in it, is that we are about to change the windows, which are now steel frames - ideal cold bridges - to some high-tech aluminium profile with high performance double glass. So I wanted to snap some shots of the current windows before the new ones come in so that I can compare. I will anyway compare in the energy spending next winter. By the way, the next post will probably be the energy assessment for the past winter.

I'll get the camera again once the windows are in! and the cold sets in!

So, there is not much to say about these, but the images are nice! Here are some samples, outside the temperature was about 6C and inside 15C:

Fig. 1: The iron/steel frames, almost as cold as the outside

Fig. 2: The house outside. Upstairs we already have the nice aluminium windows, with the super glass

Fig. 3: The electricity meter - gets pretty warm in there. It would be interesting to compare it to an old fashioned one.

Fig. 4: The CNY70 doing the gas metering

Fig. 5: Heating pipes when starting to warm up, the inflow is pretty warm , as the return is still cold. That is the best case.

Fig. 6: Old cast iron radiator warming up.

Fig. 7: GU10 spots - This one is a kind of CFL

Fig. 8: GU10 spots - this one is a standard halogen.

Fig. 9: GU10 spots - this one is a 3.5W LED

Fig. 10: Just a funny picture of a plug with a switch that I use in the computer to have it completely off when not in use.