After years of underwater deployment, I am thrilled to announce that the Cave Pearl Project has finally published:
Cave Pearl Data Logger: A Flexible Arduino-Based Logging Platform for Long-Term Monitoring in Harsh Environments, Sensors 2018, 18(2), 530; doi:10.3390/s18020530
I am sure a few people will grumble that we've been using everything from Genuine UNO's to cheap eBay clones, but that was one of our design goals from the beginning: To make a working logger using a "lowest common denominator" approach that was agnostic about whatever parts you could get your hands on.
However, our project builds upon the hard work of many members of the Arduino community (especially the contributors & moderators of this forum) so we chose an open access journal, so the paper is free for everyone to download and, hopefully, build upon for their own projects.
A visiting researcher dropped by our humble basement workshop with questions about the physical skill level students would need if they added one of our DIY data loggers to their environmental curriculum. I figured the easiest way to cover that was to simply build one, while they recorded the process.
The result of that 3 hour session is now available on YouTube
While the logger core is generic, the surface deployments tend to use the 4" housing (which is easy to build) while the underwater deployments (~ half of the current fleet) use the 2" body style. Usually those deployments are too deep to record with our little point & shoot camera, but we recently did an install in a coastal outflow that was shallow enough to capture a clip of the method we use to anchor the sensors into place. In this video we are placing the anchor in the fresh water, with extension rods to move the actual sensor into the zone where the saline water in intruding into the system.
That saved me from messing with the hardware SPI bus which we reserve for the SD cards on our loggers. A secondary benefit is that the code is really lean, on the order of about 250 bytes for the default font after the compile if you already have EEprom.h in the build anyway. The font, however takes up about 500 bytes, and I wanted the smallest possible footprint so that we could add live data output to loggers that are already compile near the memory limits.
As it turns out, stuffing those fonts (and some calibration data) into the internal EEprom was pretty easy to do:
As part of our ongoing commitment to create resources that support science education, we've released a new "EDU version" of the Cave Pearl Data Logger for 2019. Dr. Beddow's instrumentation class has been building the 2016 version of the Cave Pearl datalogger for more than three years, and feedback from that experience motivated a redesign to accommodate a wider range of student projects while keeping within the time constraints of a classroom lab schedule. The rugged PVC housing from the older build has been replaced with an inexpensive pre-made box more suitable for "light duty" deployments.
The tutorial includes a full set of youTube videos to explain the assembly. We hope this simplified build supports other STEM educators who want to add Arduino-based experiments to their portfolio of activities that develop programming and "maker" skills.
A teacher friend asked us for faster build that is less dependent on soldering because they don't have the budget for that kit. So we've developed a "minimum version" of the 2019 classroom logger using pre-made Dupont jumper cables (as we did in 2016) to reduce the build time to about 1 hour. I've also added support to the code base for using the indicator LED as a light sensor, so they can use the logger with their existing curriculum even if they don't add extra sensors.
This version is a good starting point for people building their very first data logger.
