Create your own magnetic optical density meter

We have created a magnetic optical density meter dedicated to the analysis of magneto-tactic bacteria, and invite you as a developer in an open source community.


  • Up to 800 samples per second, allows precise analysis of the rotation speed of magnetic bacteria
  • Three-dimensional quasi-Helmholtz configuration, with fields up to 3.5 mT and pulsed up to 13 mT.
  • Three color LED: red: 645 nm, 1000 mcd, green: 520 nm, 1700 mcd and blue 460 nm, 500 mcd
  • Power supply with current feedback to compensate for coil heating, cut-off frequency 200 Hz
  • Split detector photodiode (sensitivity 0.5 mlx, with green LED theoretical max OD range of 5.8)
  • Integrated pre-amplifier, SNR 83 dB (max OD range 4.0).
  • Dedicated 16-bit ADS1115 DA converter
  • Integrated temperature sensor
  • Reference light detector
  • Scattered light detector
  • Fully programmable (ESP32 using Arduino IDE), open source
  • User friendly spreadsheet recipe definition (csv format)
  • Data collection on SD card
  • Onboard Wifi link to access data


The sources we have available are:

  • Measurement head design, 3D print file (OpenSCAD, on Thingiverse)
  • Spice simulations, electronic diagrams, PCB layout (Spice, KiCad on Dropbox)
  • Laser cut pattern for housing electronics (DXF, on Dropbox)
  • Arduino program code (.ino, on Github)
  • Matlab program to analyse datafiles, with GUI (on Github)

How to join

We are just starting, and need help to build our environment. Send mail to Leon (This email address is being protected from spambots. You need JavaScript enabled to view it.) if you are interested, all skills are welcome.



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