Date;Humidity (room);Temp (room);Humidity (out);Temp (out);Pressure (abs);Wind (ave);Wind (gust);Wind (dir);Rain

Currently I programmed the weather station to save the data every 5 minutes. The long-term goal is to decide if a given wind turbine delivers a sane amount of energy (during a complete year) at a given place. As I do not want to wait that long to get some information out of this, the question arises, what I can do with this weather data?

Here an example of the output (ignore the rain and wind values, the sensors are not attached at a place where there is wind or rain, the complete set is horizontally on the floor instead of vertically how they are supposed to be; and do not be shocked about the room  values, it is the “server room” in the basement):

2010-09-02 12:55:01;52.0;18.700;30.0;27.000;978.600;0.0;0.0;135.0;4.200
2010-09-02 12:50:01;53.0;18.700;30.0;27.500;978.600;0.0;0.0;135.0;4.200
2010-09-02 12:45:01;53.0;18.600;30.0;27.300;978.500;0.0;0.0;135.0;4.200
2010-09-02 12:40:01;53.0;18.600;30.0;27.800;978.600;0.0;0.0;135.0;4.200
2010-09-02 12:35:01;53.0;18.600;30.0;27.700;978.500;0.0;0.0;135.0;4.200
2010-09-02 12:30:01;54.0;18.500;31.0;27.500;978.700;0.0;0.0;135.0;4.200

Some things I came up with myself:

• A line-graph of the values during a day/week/month.
• A graph of the amount of accumulated rain per hour/day/week/month/year.
• The average temperature/humidity (as an error bar, so see the min/max too) per day and night, but what to use as the times where the day starts/ends? I would like to have the day-part cover the real daylight time (minus some ramp-up and ramp-down time), but I do not have any idea how to get this for each day and for my region.Does it make sense to do the same per hour (without any ramp-up/-down)?
• Does the combination of temperature and humidity and maybe wind tell something? If yes, how to combine them and how to interpret the result?
• Similar for the pressure. I do not know what it tells me, but in a graph I can maybe add some horizontal lines which tell something (rain probability and maybe danger zones?).
• For the wind speed the instruction manual comes with a nice table of the beaufort scale and a corresponding description. This can be put into some colored horizontal lines which show more or less dangerous speeds.

For the plotting of the data, I intend to use gnuplot with the CSV data as the input. It should allow me to automate a lot of things, and some of the graphs should also be easy to realize inside gnuplot itself without any external processing, the question is only how to realize it. For example for the average of some values I do not know if it makes sense to use something else than the arithmetic mean.

This triggered a question. How much energy would such a device (smaller of course) produce at my place?

The answer depends upon several factors. The wind speed, the wind direction and the wind-speed-to-power-output curve of the device. If you do not take a device which rotates around the horizontal axis but the vertical axis, the wind direction can be taken out of the question (probably not completely, but to answer my question this simplification should be ok). The output-power curve depends upon the device, and I hope it is easy to get it from the vendors. The remaining open question it the wind speed at my place. Is there enough wind with enough speed?

To answer this question I bought a weather station with an anemometer (wind speed sensor). I searched a little bit until I decided to buy a specific one (actually I bought three of them, some coworkers got interested too but they found only much more expensive ones, so soon there will be three more weather stations in use in Belgium, France and Germany). The main point is, I can connect it to an USB port of a PC and there is some software for Linux to read out the data. It also comes with some other outdoor-sensors (temperature, rain, wind direction, humidity, …) and an indoor-control-unit with some internal sensors (temperature, humidity). The user interface is mainly the touchscreen of the control-unit. There is also some Windows software, which is needed to program the interval in which the measurements are taken and saved in the control-unit.

It seems the weather station is produced by Fine Offset Electronics Co.,Ltd and sold within different brands in different locations. The Linux software can read all of them, as the vendor and product IDs are not changed.

Porting the software was easy, it uses libusb and I just had to correct a little problem for the non-portable functions which are used (I asked about them on usb@ and the response was that they just got implemented upon my request and will be committed to HEAD soon). I made a little patch for the software to only use them when available (if you have not loaded the USB HID driver, you do not need to care about them) and committed it to the Ports Collection as astro/fowsr.

Now I just need to attach the outside sensors at the place where I would put the vertical axis wind turbine, install some toolkit which takes a series of measurements and displays them as a nice graph (while keeping all data values) and write some glue code to feed the output of fowsr to it. After a year I can then calculate how much power a given wind turbine would have produced during the year and calculate the return of investment for it.

The Linux software also references several weather sites, for some of them you can get even an iGoogle widget so that you can view the data from wherever you want (as long as you have a suitable internet connection). I think this is also something I will have a look at later.

Note to users in Europe, the device also comes with a DCF77 receiver. As the time is distributed in UTC+1 (or +2, depending on the daylight saving time), you should adjust the timezone setting accordingly to this, not to plain UTC (so for me the timezone should be ‘0’ for the same timezone).

Now I installed rnews on my webserver. It is multi-user capable, so that multiple people can read the feeds they are interested in, without the need to have multiple installations. I can use it from any place where I have an internet connection, without losing the state.

It is in the FreeBSD Ports Collection as www/rnews.

People which want to test the linuxulator part should first make sure a native FreeBSD application has no problem accessing the device.

The WP-login, WP-dashboard, and logged-in users where not affected by this, so if you have some custom rules which deny access to your blog, make sure you make a test of your blog when logged-out.

The discussion about this is happening over at fs@, so go there and have a look for the CFT (with a link to the WIP of the script) and the discussion if you are interested.

So far there are some minor details to sort out (and a little bit of documentation to write) before I can commit it… probably next week.

Unfortunately Analytics is AFAIK not available in OpenSolaris, so we can not go out and adapt it for FreeBSD (which would probably require to port/implement some additional dtrace stuff/probes). I am sure something like this would be very interesting to all those companies which use FreeBSD in an appliance (regardless if it is a storage appliance like NetApp, or a network appliance like a Cisco/Juniper router, or anything else which has to perform good).

Some definitions:

• A direct dependency from A to B is when program/port A uses symbols from library/port B.
• An indirect dependency from A to C is when program/port A uses symbols from library/port B but no symbols from library/port C, and library/port B uses symbols from library/port C.
• An explicit dependency from A to C is when it is a direct or indirect dependency A to C, and when the compiler-time-linker added an explicit reference to C to the program/lib of A.

Ideally we have no indirect dependencies in the explicit dependencies, only direct dependencies. Unfortunately in reality we also have indirect dependencies there. This has at least two causes:

1. libtool (at least 1.x) does not (or was not) come with a hint on FreeBSD, which tells that the run-time-linker is recursively resolving dependencies.
2. Some pkg-config setups list indirect dependencies as explicit dependencies (IIRC it depends if Requires.private and/or Libs.private is used in the .pc file or not; if it is used, there should be no indirect dependency appear from this software, but I am not 100% sure about this).

Three years ago I wrote /usr/ports/Tools/scripts/explicit_lib_depends.sh, it looks at the files of a given port (it needs to be installed), and prints out explicit dependencies. Because of the indirect dependencies which could be listed there, this list is not a list of ports which are real dependencies from a source code point of view, but it reflects the link-time reality. If a port C shows up there, the port which is checked needs to be rebuild in case the ABI of library/port C changes.

I can be happy that he is/was this fast (and that we have such a productive and efficient committer), or I can be sad that I do not have the time anymore to be faster than I am with such things… or both. Hmmm… I think I will go the happy way.

My pragmatic solution (for services started via a good rc.d script which has a working status command) is a crontab entry which checks periodically if it is running and which restarts the service if not. As an example for apache and an interval of 10 minutes:

*/10 * * * *    /usr/local/etc/rc.d/apache22 status >/dev/null 2>&1 || /usr/local/etc/rc.d/apache22 restart

For the use case of this service/machine, this is enough. In case of a problem with the service, a mail with the restart output would arrive each time it runs, else only after a reboot for which the service did not restart.