Build your own instruments! DIY data loggers with no custom PCBs

We use si7051 as a cheap 0.1C calibration reference for our thermistors, but that’s the only high accuracy temp sensor I have experience with. After that we go to lab quality nist certified thermometers which start around $250 each.

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Hoping to spend time this winter updating some of our Arduino based prototypes, and many will need real-time output. With I2C OLED’s getting so cheap lately, there’s no reason to squash it all onto just one display

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We’ve been producing Excel tutorials to support Dr. Beddows students in Instrumentation, & Hydrology courses. Where those overlap with material in the Cave Pearl project we post them to YouTube. Two that might be of particular interest to the GOSH community are:

Derive empirical fit constants with Excel’s trendline

Using Excel’s Fast Fourier Transform tool to derive a tidal frequency spectrum

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In our continued effort to support STEM instructors we’ve developed an even simpler 2-module data logger that can be assembled in about 20 minutes and runs for more than a year on a CR2032 coin cell. It stores readings in EEprom memory and the data download is handled through the Arduino IDE’s serial monitor window. This may well be as minimal is it is possible to get with cheap eBay parts and still have a capable data logger that environmental monitoring students can modify and reprogram for their final projects:

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Amazing to see news on this project since the first post back in 2018! :clap: :clap: :exploding_head: :tada: Thank you @TheCavePearlProject for sharing these updates.

My personal interest is in motion-triggered camera traps for wildlife observations, but I think I can learn lots from you in terms of rugged/weatherproof/waterproof casings.

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Posted a general overview of how to make your electronics more water resistant, including recent updates to the PVC housing system we developed. The way we oil-mount pressure sensors might be of particular interest to people working in marine environments

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I know these janky installations will have the weather nerds out there inhaling through their teeth, but it’s worth noting that we made multiple attempts over the years to do things the ‘right way’ that kept failing to go the distance. Even in a harshest environment critters are the biggest threat to actual ‘boots on the ground’ research - both four and two legged. So our rule of thumb for anything that’s going to last is now: “Make it ugly & make it heavy”

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The latest in an ongoing series of build videos supporting Dr. Beddows enviro-sci students who all have to first build the logger(s) that get used for their final research project. These videos also support the other instructors who have adopted our DIY loggers for their own courses. These Falcon tube mini-loggers may well be as minimal as it is possible to go while still offering the flexibility of supporting multiple different sensors. The only limitation is that the CR2032 levels out at 3.0v and runs all the way down to 2.8v before shutdown - which rules out some older sensors like the DS18b20 which has a lower limit of 3.3v. After calibration the NTC has so much more resolution that it’s not much of a problem.

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We needed a way to test our little falcon tube loggers and household water filter housings are a good solution as the domestic water pressure range of 40-80psi overlaps nicely with sport diving depths. The internal clearance of that 4x10 filter housing is only slightly larger than 4.5" x 9.5" but could accommodate a good range of other dive computers, lights, etc for testing.

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The e360 course required different sensors for each lab, so we tweaked the 2022 2-part model with 3D printed rails holding mini breadboards to provide this flexibility. The software has also been streamlined significantly and people shouldn’t have too much trouble adding other sensors provided you stick to 1,2,4,8 or16 bytes/record and your modules don’t pull more power than the coin cell can provide.
e360LoggerW2sensors_640pixw

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Umm, just to be clear, this is an open source science project and we are not selling anything - you have to get the parts yourself. Depending on where you buy them the logger costs about $10.

Who would you say have been the primary course attendees? I.e. age, education, interest/field etc? How many of your loggers (of any version) would you say have been built and deployed in anger, would you say?

Our primary audience is instructors of college undergrads. Their students can reasonably be expected to learn enough coding to adapt the device to different summer research projects. For example one student built more than a dozen of these loggers to monitor temperature in turtle nests. As to the rest of your question, I’m not sure what you mean by ‘deployed in anger’? Why would anyone be angry about an open source science project?

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I mean, how many loggers would you guess were deployed because there actually was some data that needed to be logged, as opposed to as a learning experience for example, or for some other reason?

Thanks again for posting your loggers over the years.

The EDU model described in that recent post is simplified specifically for learning experiences, so I’d estimate less than a hundred (?) of those classroom models have been deployed by students outside of the courses for real world research projects. I can only estimate because I’m not sure how many students have done research projects with our colleagues at other institutions who have also been using the EDU builds. And there have been different teaching models over the last 10 years, and other instructors tweak the design to their own course needs.

By comparison, just for Dr. Beddows research alone we’ve deployed about 500 self-built loggers over the last decade. And that’s just one research project, and not counting all the commercial kit we’ve also deployed. But those research builds are more complicated on software side, and we make very rugged PVC housings for them which is quite time consuming. A typical installation gets 5-10 loggers with various different sensors, and a research site will have up to 10 installations. So you go through a lot of units with a yearly turnover of at least 15-25% because the get damaged, or simply age out.

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I can relate to the difficulty of making rugged housings.

Out of curiosity, what would you do if you had to make 100 units per week, could you modify the design to accomplish that? Say your task was to seriously compete with Hobo on price, features, availability. Could you come up with a plan?

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Seriously? Aside from the fact that the answers to these questions are already obvious to anyone who knows what they are doing - if you are only here to take ideas from people who are actually contributing to the open source hardware movement, so you can turn them into commercial products for your own profit, then you are in the wrong place.

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I’m not asking you to come up with a plan, but whether a plan could be come up with. Yes I am serious in considering this for the Ubiquity 25 initiative. I would normally prefer a project which didn’t have to compete with an incumbent, just because it’s less work, but I’m not averse to competition. Have a think. Or not.

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Ok, after reading that I can see that you meant well so I apologise for my harsh tone.
However, please remove our project from consideration for your initiative.

Happy to see the new logger mentioned in the nerd press:

https://twitter.com/arduino/status/1736145734670451117

https://blog.adafruit.com/2023/12/15/the-e360-a-diy-classroom-data-logger-for-science-arduino-science/

However, interest on reddit is essentially zero. Even the response on r/ScienceTeachers is usually something like “But you didn’t explain what a ‘data logger’ is or can be used for?”

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