Mini Pearl Logger Kit


This item is no longer kept in stock.


A Mini Pearl Logger is also available in a solder-free kit with a TPL5110 timer and Pro kit with TPL5110 timer and minimal accessories.

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, removing resistors from the modules, and modifying the supplied sketches. The key to longevity is coaxing the components into a low current sleep mode between logging events.

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, a low power timer can control the logger, so instead of putting the logger into a low power sleep mode between logging events, the timer turns the logger off completely--see the Mini Pearl Snap Logger Kit and the Mini Pearl Pro Logger Kit

If you want to try an external low power timer with this logger, select the option above to include a Log-a-Long Timer Kit for an additional $4.00. A different sketch to support the timer can be found with the documentation for the Mini Pearl Snap and Pro loggers at the Guides page.

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. Sensors must operate at 3.3 volts.

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 UART adapter or cable which is not included in the kit. A UART 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 reduce power consumption.

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. This research note describes the assembly process. 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 three AAA batteries (has switch and leads)
  • Loose headers for Pro Mini
  • A bunch of 24AWG stranded wire of different colors
  • Custom 3D printed mounting plate

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. A case for 3 AAA batteries in included (3 x 1.5v = 4.5v).

 You must supply:

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