Project blog 2011....

7.6.2011
Visit of the "Sensor + Test" fair in Nürnberg.
The companies Senseair and Driesen & Kern promise to help by a donation of sensors.
20.6.2011
The people from Senseair have held their promise :-) ! They sent us 5 sensors for the next project. Thanks, Mr. Egeland!
6.7.2011
I had an interesting talk with Mr. Bo Hansson, Managing Director of LogiCO2 in Mersch.
Mr. Hansson will help us to calibrate the sensors.
27.7.2011
The measuring station is replaced by a reworked one. Main changes: new sensor 0...4% with ABC turned off, ventilation every 60s to reduce lag time, better thermal isolation.
30.7.2011
First diagrams
10.5. to 24.5.2011
24.5. to 27.7.2011
At first glance the diagrams show astonishingly low CO2 values below 10000ppm = 1%, compared to last year with values above 10000ppm.
However, due to the automatic baseline correction (ABC) of the sensor there is a bias of ca. 3700ppm in the values, which means that the real values are 3700ppm higher than indicated, at least at the end of the time period.
(The ABC algorithm assumes that the sensor is periodically taken to fresh air with 400ppm. As this is not the case in the mine, we get an error from the ABC algorithm. The value of 3700ppm is the mismatch between the installed station and a handheld CO2 sensor.)
There is a daily variation in the values that is obvious to see (if you know what epoch seconds are. In fact they are seconds elapsed since 1.1.1970 at midnight. I use this time unit as it combines time and date into one sole time variable, so the scale of the diagrams is no problem.)
Ther seem to be other periodicities. A Fourier analysis will show.

Project blog september 2011...july 2012

September 2011
A new group of students starts working on the project.
The task description (in german) can be found here: Aufgabenstellung 2011/2012
The new task is divided into 3 parts:
  • elaboration of a testing box for CO2 and temperature sensors
  • elaboration of a control and display box that can be linked into the cable to the measuring station at any point in the mine, especially in the place of the measuring station
  • extension of the measuring system so that other parameters can be measured: concentration of O2, air velocity, air pressure and gravity (to detect stability problems of the gallery)


    • School year 2011/2012
    Everything runs so fast. The educational reform and the opposition against its absurdities consume much energy.
    In my free time i'm learning Linux and Python programming language, to be able to program a nice interface for the data collection and manipulation. Though Python is a very friendly language, it's not trivial to learn about objects, classes and threading.

    As strange as it seems, I don't find the time to go and have a look at the station in Rumelange, and collect the data


    March 2012
    Didn't we just start working on the project, at school? And now it's already time to stop!
    Unfortunately only the testing box for the sensors is totally finished. The hard- and firmware for the sensors of the new measuring station are ready, but not the station itself. We would have needed another month or so to accomplish the rest.


    May 2012: new ideas
    It's time to review the concept of the whole system.
    The master station was designed at the beginning to be used as stand alone or in combination with a computer.
    Now it looks as if a computer would always be present near the master station. If so, wouldn't it be much simpler to do the master station job of issuing commands and collecting data by a software running on the computer rather than by a microcontroller?
    This would be more flexible and part of the hardware could be economized.
    Even better: we could use the new Raspberry Pi for this job.


    Naming of stations
    To avoid confusion it's time to give the stations a name:
  • Station Alpha (A) is the first station built by me before starting the project with the students
  • Station Beta (B) is the station built by the students in 2010 and reworked by me in july 2011
  • Station Gamma (G) will be the new station containing new sensors (O2, air velocity, air pressure)
    • To call the stations from the master station, "A", "B", "G" will be used instead of "*" in the future (this has to be changed!)


    Mid may 2012
    I start reworking the Alpha station to make it compatible with the Beta station currently installed in the mine.


    9th july 2012
    The new Alpha station with the new computer interface and software is installed in the mine.


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    Project blog september 2012...

    September 2012
    A new team of 2 students is working on station Gamma (O2, air velocity, air pressure).
    I start filtering and plotting the data. This takes much more time than I thought (still learning Python and Gnuplot), and it appears that more attention must be brought to data transmission. There are a lot of transmission errors that didn't appear when the station was tested outside the mine. There are even 2 months (march and april 2012) that give no useful data. Maybe some sort of checksum or the like should be used to check if incoming data are correct.

    CO2 diagrams july 2011 to july 2012