Objectives

  • Make a data logger for less than $500. It can store data for the temperature, pH, and DO with a time stamp and using I2C communication.
  • Why I2C (Inter-Integrated Circuit) communication mode? The main reason is one microcontroller can stack up as many sensors with two wires given that each of sensor has an unique address.

1. Parts needed

This data logger is specfic to the need I have with a photobioreactor culturing microalgae. Culturing microalgae needs several key parameters in which the temperature is for thermo control and biological status, pH is for CO2 supply and control, and Dissolved Oxygen (DO) is for photosynthesis activity. This data logger can be used for other biological systems as well such as with aerating or pH static control.

Gallery of the parts
Gallery of parts
Exhibition of the parts used in this tutorial.
Lists of parts with the price (2017):

  1. Arduino MEGA 2560, $35, https://goo.gl/6EdBGu
  2. Power adapter for Arduino board, $5.98, https://goo.gl/BzuZbk
  3. LCD module I2C (display), $8.99, https://goo.gl/za3cBn
  4. Real-Time Clock (RTC) breakout, $7.5, https://www.adafruit.com/product/3296
  5. MicroSD card breakout board, $7.5, https://www.adafruit.com/product/254
  6. 4GB SD card, $6.98, https://goo.gl/tCY2ys
  7. Waterproof DS18B20 Digital sensor, $9.95, https://www.adafruit.com/product/381
  8. pH probe + Kits+ Standard buffers, $149.15, https://www.atlas-scientific.com/product_pages/kit...
  9. DO probe + Kits+ Standard buffers, $247.45, https://www.atlas-scientific.com/product_pages/kit...
  10. Breadboard, jumper cable, $7.98, https://goo.gl/3g3mTe
  11. (Optional) Voltage Isolator, $24, https://www.atlas-scientific.com/product_pages/cir...
  12. (Update) Voltage Isolator with USB connector, $50, Voltage Insolator with USB port.
  13. As of September 2018, the Atlas-Scientific has updated the design of the insolator. The pH/DO breakout can be plugged on top the insolator. The USB port is convenenient for a advance setup such as with Raspberry Pi.

    In addition, the isolation of water is much less in air. The voltage insolator is not cheap, but it worths to invest and reduces the headache later.

Total: $510.48.

  • The price was updated on 2017, slightly changed in September 2018. The DO and pH probes contribute to the major of the total cost. A simple data logger to collect only temperature could cost less $20.
  • Certain parts (like the generic board: Arduino, temperature sensors) can be bought from other vendors (Aliexpress, eBay, Chinese seller) for a lower price. pH and DO probes are recommended to get them from Atlas Scientific or other trusted vendors.
  • A multimeter is recommended to check conductivity and voltage. It costs about $10-15 (https://goo.gl/iAMDJo)