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Project Karaburan
Monitoring water quality
Status Initializing
Contact bertrik
Last Update 2024-07-14

Next steps

  • write python scripts
    • arduino turbidity
    • turbidity-to-mqtt
  • hook things into systemd / udev
    • e.g. insert GPS -> create symlink with udev -> trigger (re)start of gpsd

USB HID as analog input

An stm32 based bluepill board can be flashed with firmware to allow its analog inputs to be exposed as USB HID sliders.

Flashing the bluepill with openocd to the freejoy firmware:

  • install openocd
 sudo apt install openocd
  • connect an stlinkv2 to an stm32 bluepill, connect the stlinkv2 to USB
  • flash the freejoy firmware as follows:
 openocd -s /usr/share/openocd/scripts -f interface/stlink.cfg -f target/stm32f1x.cfg -c init -c "program firmware.hex verify reset exit"
  • watch the kernel logs
 sudo dmesg -w
  • connect the stm32 using a USB cable
  • download the freejoy configurator from https://github.com/FreeJoy-Team/FreeJoyConfiguratorQt
  • start the configurator and load the karaburan.cfg setting
  • Write config to device -> it should reboot now and come up with the new settings

Verify that it works:

  • install the evtest package
  • run
 evtest /dev/input/by-id/usb-FreeJoy_FreeJoy_v1.7.1-event-if00

See also https://github.com/vostrenkov/EazyJoy


See https://hub.docker.com/_/influxdb

See https://github.com/bertrik/karaburan/tree/master/influxdb

investigate RTK GPS

Goal: figure out if it is practically possible to achieve cm resolution with a 200-euro GPS and a free correction service: YES

Edit /etc/default/gpsd, set GPSD_OPTIONS:

 GPSD_OPTIONS="-Gn ntrip://user:pass@ntrip.kadaster.nl:2101/CBW100NLD0"

Option -G exposes the control socket on all network interfaces, option -n keeps the GPS active if there is no one currently connected.

Plotting live location on a map:

Station at Stolwijk (close to Gouda): https://gnss1.tudelft.nl/dpga/station/Stolwijk.html#STWK ?

Starting from the command line:

  • stop gpsd.socket
 sudo systemctl stop gpsd.socket
  • run from command line
 sudo /usr/sbin/gpsd -Gn -D 1 -N /dev/ttyUSB0 .... (not sure yet)



  • air quality sensors
    • ammonia
    • NOx
  • water chemical analysis
    • nitrates
    • ammonia
    • dissolved oxygen
    • sulfide/sulfate
    • phosphates?
    • salinity (chlorides?)
  • water physical analysis
    • temperature
    • clarity/turbidity -> investigate standard ways of measuring/expressing this
    • conductivity/total dissolved solids
    • water properties by light reflection, hyperspectral/polarity
    • depth?
  • boat control
    • trajectory -> steering
    • idea: interface with the remote control, not with the boat
    • idea: find a boat with easily hackable remote control protocol
    • idea: can we get sensor data over this link too, e.g. GPS?
  • camera control
  • post-processing
    • data presentation
      • video/photo stitching
      • time lapse view
      • map view of properties
  • use cases
    • verify with domain experts, how to engage?
    • slootview, under/above water
    • minimum viable prototype
    • high-res measurement by location, by time
  • materials
    • boat selection
    • processing platform selection
    • communication platform selection

Air quality sensors

Nitrogen compounds in air

According to https://www.rivm.nl/stikstof/monitoren-advies-onderzoek/overzicht-stikstofmetingen/metingen-stikstof-in-de-lucht average (typical?) values of

  • Ammonia (NH3): 6.7 ug/m3 (9.6 ppb)
  • NOx: 27.3 ug/m3
  • NO2: 18.6 ug/m3 (9.9 ppb)

(ppb-conversion using https://www.breeze-technologies.de/blog/air-pollution-how-to-convert-between-mgm3-%C2%B5gm3-ppm-ppb/ )

RIVM report on inexpensive nitrogen-in-air sensors: https://www.samenmeten.nl/sensoren-voor-no2 Conclusion: most sensors are not sensitive enough to be used in typical outdoor conditions, with perhaps one exception: alphasense NO2-B43F

Water physical analysis

Turbidity / clarity

See https://en.wikipedia.org/wiki/Turbidity

Aliexpress sensor TS-300B: https://nl.aliexpress.com/item/1005006732956937.html Has a range 0 ~ 1000 ± 30 NTU

Order of magnitude for turbidity:

  • Drinking water upper limit: 4 NTU (European turbidity standard for drinking water)
  • Ambient water: 10-150 NTU. The US state of Washington use a "background" value of 50 NTU as reference.

(see https://en.wikipedia.org/wiki/Turbidity#Standards_and_test_methods )

So the Aliexpress sensor is suited only for "dirty" water.

Boat control

Typically the wireless link looks like this:

  • 2.4 GHz working frequency
  • 500m range

Interesting links:

remote control

Image of remote control RF chip: [...]


  • 12.000 MHz crystal/oscillator
  • 16-pin control chip: 20_CL6L071
  • 6-pin RF chip: 1110 / VKA3, could be an rx/tx switch, amplifier or filter circuit

See also: https://www.open-tx.org/

Next steps:

  • map out the connections between the mainboard and the rf board, expected: VCC, GND, spi ?

Use cases


Useful distinction, typically used in documents/guidelines:

  • chemical quality, what substances are present in the water?
  • biological / ecology quality, what kind of living organisms live in the water?

Reeuwijkse plassen


potential applications:

  • inspect water sides (oever) over time
  • underwater camera: detect invasive cray fish
  • sample water properties at high spatial resolution, high time resolution
  • early detection of indicators for cyanobacteria: temperature and nutrients

Detect/find pollution source

  • ...


reading temperature sensor

The idea is to to use a DB18B20 temperature sensor, read it using an arduino nano board acting as a 1-wire adapter. Use openwire-fs as user-side openwire software http://owfs.org


  • Add the regular user to the 'dialout' group, so it can access serial ports
 sudo adduser <name> dialout

Setting up the hardware:

  • connect the DS18B20 to the connector board with the pull-ups
  • wire the connector board to the arduino nano, see ...
  • plug the arduino nano in the pi

Setting up the software:

  • Install openwire fs
 sudo apt install owfs
  • Create the openwire fs mountpoint
 sudo mkdir /mnt/1wire
  • Configure owfs, edit /etc/owfs.conf
 server: device = /dev/ttyUSB0
 mountpoint = /mnt/1wire
 (comment out the line with the FAKE devices)
  • Configure systemd services
 sudo systemctl enable owserver owhttpd
 sudo systemctl disable owftpd
  • Start the systemd service
 sudo systemctl start owserver owhttpd
  • Check the logs
 sudo journalctl -xeu owserver -f
  • Open a browser to view the web interface
 http://localhost:2121 or