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Sensor Logging with Beaglebone Black




Environmental Monitoring using Single-board Computer

Long-term sensor data logging requires large storage space (in embedded terms), which is often not easily accessible using 8-bit microcontrollers. The Beaglebone Black with internet access and a 16GB microSD card solve this problem nicely: recorded data can be stored on the card until read out via Ethernet/WiFi, and the excess processing power can be used for pre-processing like filtering, plotting and web page hosting.

A BMP180 barometric pressure sensor and an HTU21D humidity sensor are connected to a Beaglebone Black via I2C. Technologies used:
  • OS: Debian for ARM
  • Data processing: Python and matplotlib
  • Storage: SQLite
  • Task scheduling: crontab
  • Webpage generation: a tiny bit of Jinja2 for HTML template
  • Web hosting: Apache and CGI with Python

So many technologies for such a simple task.

Ear Popping on Airplanes


Here's one recorded during a flight from Denver to LA (the date is incorrect - the BBB hadn't had a real time clock installed at the time):


So the air pressure in LA really is higher than that in Denver. My ears pop every time during take off and landing and I always wondered whether it is popping "out" or "in". Now I know it's more complicated than that. Interesting to know, hope I didn't break any law (shouldn't; smartphones these days have barometric pressure sensor built-in).


Update: this has turned into a research project.