OpenCTD Project Switches to Adafruit Feathers for Revision Two of Its Oceanographic Data Loggers

The new OpenCTD conductivity, temperature, and depth sensor boasts more power, costs just $300 in parts, and is still open source.

The OpenCTD project, which aims to create a low-cost and readily-accessible open source conductivity, temperature, and depth (CTD) sensor for oceanographic research, has officially launched revision two of its design — now built around an Adafruit Feather M0 Adalogger development board.

"In 2013, Kersey Sturdivant and I embarked upon a quixotic quest to create an open source CTD — the core tool of all oceanographic research that measures the baseline parameters of salinity [conductivity], temperature, and depth," project co-creator Andrew David Thaler explains. "We weren’t engineers; neither of us had any formal training in electronics or sensing. And, full confession, we weren’t (and still aren’t) even oceanographers!

"What we were were post-doc marine ecologists working with tight budgets who saw a desperate need among our peers and colleagues for low-cost alternatives to insurmountably expensive equipment. And we had ties to the growing Maker and DIY electronics movements: Kersey through his work developing Wormcam and me through my involvement with OpenROV.

"Seven years and five iterations later," Thaler continues, "we are releasing the long anticipated OpenCTD rev 2 as well as the comprehensive Construction and Operation Manual! OpenCTD rev 2 builds on over half a decade of iteration and testing, consultation with oceanographers, engineers, developers, and makers around the world, extensive coastal and sea trials, and a series of workshops designed to test and validate the assembly process."

Thaler claims the redesigned OpenCTD rev 2 can be built in as little as two days by someone without previous electronics experience while costing just $300 in parts — the majority of which, bar a few custom pieces that need to be 3D-printed, can be found in high-street hardware stores and online retailers. The new design is rated to a 140 metre operational depth, can be deployed by hand from any vessel - and, in one of the changes made for the the latest revision, can be switched on and off externally without dismantling through a clever magnetic switch.

"Our goal has always been to provide a platform for other ocean stakeholders to build upon and expand," Thaler continues. "While the last revisions of the OpenCTD software pushed the limits of the tiny Arduino computer, the new build has a massive amount of headroom for adding custom software to support new sensors, enhanced onboard analytics, incorporate new features, and expanding its capabilities in novel and exciting ways. We release the software open source with no restrictions on use, modification, or commercialization."

More information on the OpenCTD is available on Thaler's blog post, while the hardware and software can be found in the project's GitHub repository under the permissive MIT Licence. A construction and operational manual is additionally available on MarXiv.

Gareth Halfacree
Freelance journalist, technical author, hacker, tinkerer, erstwhile sysadmin. For hire: freelance@halfacree.co.uk.
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