Using the PICO DrDAQ data logger for a distributed sensing environment
The PICO DrDAQ board
The DrDAQ (by Pico Technology) is a low cost data logger with built in sensors for light, sound (level and waveforms) and temperature, a digital output, plus 5 additional sockets for external sensors. It plugs into the parallel port of any PC, and allows capturing of fast signals (such as sound).
The DrDAQ comes with its own logging programs, but these are not very flexible w.r.t. real-time logging for indefinite periods. That's why I wrote a small client/server to do the job: the client constantly reads the sensordata, calculates features that describe the data (such as mean and standard deviation) and forwards it at a slower rate to a server that collects all data and puts it in one giant log file.
Above you can see the interface of the windows client. By pressing the 'Stealthmode' button, it can be hidden away in the system tray.
Program, source code (VC++) and resource files for the windows client are available here and here respectively. Things are a bit trickier for the Linux client, as you first need to add a module to your kernel. Binaries and source are available upon request. For the server-side of the software, look for instance at this little program (here) and source code (here) .
To plot and analyse the data, one usually needs more powerful plotting software than MS Excel (which is very limited). Matlab appeared to be the best software so far, better at handling extremely large data files (than, for instance, gnuplot).
Simple Example
This is report was generated with my serverlog_plot script (in Matlab) using a test-run 10 Mb datalog from my office, taken between Wednesday 12/12/2001 at 19:02:04 and Monday 17/12/2001 at 11:01:30, with a single DrDAQ pico board. Notice how you can easily pick out working days (artificial lights are on, sound levels are higher, and even the temperature and humidity levels increase a bit), Ph, resistance and voltage were not connected to any sensor.
Screenshots
Ingredients: 12 DrDAQ boards, 12 Parallel Cables, 24 Pico sensor cables, 12 humidity sensors, 12 Reed switches, 24 External Temperature sensors, 12 install CDs, 12 Manuals, and 12 Ph electrodes.
The board pinned to the wall, to get the best readings for light, sound level, and temperature.
My workspace monitored by the DrDAQ board.