Mini Pearl Logger Kit


Price includes US shipping.

Note: This kit now includes a 3.3 volt microSD board and 128MB or 256MB microSD card. These allow sleep current to be much lower and the logger can last longer on batteries. A 128MB SD card should allow 2 to 4 million data logging events to be recorded.

This kit includes all the parts to build a very capable data logger based on an Arduino Pro Mini microcontroller. Connections among the Pro Mini and two other electronic modules, a microSD board and real time clock board, must be soldered using the included wires. 

Environmental data loggers made with these components have seen much recent research and development by Ed Mallon for his Cave Pearl Project. That site has extensive discussions and instructions for fine-tuning the Cave Pearl Logger for reliability and longevity -- Ed's loggers reliably collect data unattended for more than a year. This can require disabling LEDs and removing resistors from the modules and modifying the supplied sketches.

Without all of Ed's modifications, this kit will build a data logger that is likely capable of collecting data unattended for a few weeks on small batteries. For greater longevity, all of Ed's modifications are open source, well documented, and easy to do. The real world performance with only a subset of the modifications is still being tested.

This kit does not include any sensors other than the temperature sensor built into the real time clock. Several types of environmental sensors can be added to your order from this page.

The Arduino Pro Mini does not have a USB port (that's why it can last so long on batteries), so programming the Arduino requires an FTDI USB to serial adapter or cable which is not included in the kit. An FTDI adapter is available as an add-on purchase.

An included LED can be programmed to flash red, green, or blue when the sketch completes certain tasks. This is intended for use during programming (e.g., debugging) and for confirming that the logger is working just before field deployment. If all looks good, the LED should be disconnected so it does not use extra battery power. Installing the LED is optional, but is very helpful especially if you remove the LEDs on the modules to save power.

This kit does not include step by step instructions for assembly. A quick start guide, assembly suggestions, and a starter sketch can be downloaded here. The wiring diagram below is your primary guide to assembly. If you have any questions check these research notes and leave comments or click Contact above.

Included parts:

  • Arduino Pro Mini compatible microcontroller (3.3v)
  • 3.3v MicroSD card board
  • 128MB or 256MB microSD card
  • Real time clock (DS3231) board
  • CR2032 coin cell battery for RTC
  • Common cathode RGB LED
  • Resistor for LED (470Ω to 1kΩ)
  • Case for four AA batteries (has switch and leads)
  • Loose headers for Pro Mini
  • A bunch of 24AWG stranded wire of different colors

The recommended way to wire the Mini Pearl Logger. One or more I2C sensors can be connected to an I2C hub built into the RTC.

 You must supply:

  • soldering iron
  • solder
  • wire cutter/stripper
  • heat shrink tubing (optional)
  • connectors (optional)
  • sensors
  • cables for sensors
  • FTDI converter for programming
  • weatherproof enclosure for field use
  • batteries