An Arduino-based data logger, from the work of GreatScott

As mentioned, this project is based on the work of GreatScott. It merely aims on learning and improvement.

Project's Instructables page

Project's Youtube video

A data logger is a tool which monitors physical data such as voltage, current, power, ... and stores that information somewhere.

It can have a display, a storage space, anything useful to treat data.

• Adafruit INA219 by Adafruit (with dependencies)
• SSD1306Ascii by Bill Greiman
• SdFat by Bill Greiman

Arduino AVR Boards by Arduino

• Board: "Arduino Pro or Pro Mini"
• Processor: "ATmega328P (3.3V, 8MHz)"

• Used SSD1306AsciiAvrI2c.h instead of Adafruit_SSD1306.h (more optimised)
• Got rid of SPI.h (less clogging)
• Used a tinier font + reorganised display (faster display)
• Each display line updates only if value changed since last measurment (faster display)

• Used a SdFat32 object instead of an SdFat (more optimised but requires FAT32 formatting)
• Merged all 3 text files into one *.CSV (faster and more manageable)
• Used optimised SDfat settings
• Made the file open only at startup instead of each cycle (faster SD timing)
• CSV lines are written for 10 cycles, then the file is synched every 10 cycles

• Made ina219 go to sleep after measurments (is up only 11 ms / 100 ms, less power consumption)
• Disabled ADC (less power consumption)
• Used an Arduino Pro Mini 3.3V (less power consumption)
• Used a timer interrupt instead of a timed loop (more precise when cycle < 100 ms)
• Fixed a power consumption calculation mistake (t = elapsed[ms] / (3600[s/h] * 1000[ms/s]))

• Sometimes (34 times over 26500 cycles), SD logging can take up to 100ms alone.
  • Use of a circular buffer to write 64 bytes blocks at a time
  • Use of a binary file instead of a text file
  • Asynchronous use of the files (measurments buffered each 100ms, then written when free time)
• Power consumption is still high
  • Disable Brownout Detection, as it is almost useless because of the LiPo management chip (Vcc never < 2.4V)
  • Use of sleep modes
  • SD card reader can be disconnected via the ENABLE pin on the onboard voltage rectifier when no SD card inserted
• Screen refresh every 100 ms can be hard to read
  • A switch to choose between 100ms and 300ms refresh rate
  • A button to hold a value