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Simple DIY data loggers with no custom PCBs

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We've published a paper about these in Sensors [ http://www.mdpi.com/1424-8220/18/2/530  } (open access, free pdf download) describing how we use these in caves and underwater, but we also use them on the surface in weather stations for atmospheric conditions, etc. These are stand alone loggers, and are relatively simple devices compared to the Pi-based wireless FIDO's that people have already been talking about in the FarmHack forums. So no text messages, etc. but adding sensors it pretty easy with the support libraries available from Adafruit/Sparkfun.

These loggers and surface housings are relatively easy to assemble, and even without any additional sensors the basic build gives you a temperature logger for less than $20.  Step by step instructions are on the projects website: ( https://thecavepearlproject.org ) and operating code that is easy to modify is available on Github. (use the UNO logger code if you are just starting out with Arduino programming)  The two different environmental housings can be constructed from PVC fittings using basic shop tools, and the 4" housing easily survives full immersion in water to about 3-4 m deep. We frequently use these loggers with MS5803 pressure sensors to monitor water levels.

Dorn's picture

Great contribution!  There is a dynamic Farm IOT conversation that I would love to loop you into.  Check out http://forum.goatech.org .  We are working to link the Farm Hack forums into new tools like Discourse and  riot group chat to facilitate exchange of ideas.  Your data loggers would be a great tool to document in the tools section of the site- which will also make it easier to find.  Look forward to next posts!

EdMallon's picture

I'd be happy to put a note about the Pearls in the tools section here. But thought I would check the forum first to see if anyone was actually interested before I did something like that.

I will look around http://forum.goatech.org and see what the discussions are like. I'll sign on if there's something I can make a positive contribution towards. Keep in mind that our work is pretty tightly focused on hydrology, rather than Ag.

EdMallon's picture

Just came across this interesting talk on the different growth rates with the same amounts of light spread out over different time periods.


With all the different I2C light sensors out there, LED level controllers like the one he describes at the end of the video would be relatively easy to build with an Arduino. Especially if you could live without the blue-tooth functionality (it: to change the set level for a different crop, you would need reload the logger from your laptop)

EdMallon's picture

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


EdMallon's picture

Dr. Beddow's instrumentation students have been building our EDU logger for more than three years and, based on that experience, we've redesigned the classroom model to accommodate a wider range of student projects. A full set of part links & YouTube videos explains the new assembly in enough detail for beginners. We've also released a new "Data logger starter script" which should run on just about any Arduino-based project:


Hopefully this version of the logger is easier for people just starting down the path to building their own environmental monitors.

EdMallon's picture

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. The ability to use the red &blue LEDs as a proxy for PAR measurements may be interest to the farming community. (see: Forest Mimms publications on that for further reference)

This version of the Cave Pearl is probably the best starting point for people building  their very first Arduino-based data logger.


EdMallon's picture

We recently posted about application of our 1-hour  'classroom logger' that has a variety of options for fine-tuning to the things people on this forum are interested in.


Now, I know there's alot of hand-wavy unknowns in there, and creating a pseudo NDVI with transmittance rather than reflectance bends the rules a bit: but keep in mind this was meant from the start to be a conceptual experiment, rather than a rigorous tool at this stage. This fun little hack really has legs in an educational context, and it wouldn't take much to tune the idea to any specific application with better LED selection.