Reply To: Datalogger build

I’d say if you want to start monitoring ASAP you’ll need to buy the “value added” sy

I’d say if you want to start monitoring ASAP you’ll need to buy the “value added” system that has had the work done for you.
You need to pay attention to the specification sheets.
This should be integrated piece of equipment with all functions, logger,SD card/USB drive, solar panel and sensor – so that if there is any queries you have one place to ask questions “How do I make this work per specification sheet”
This would be used by the “stream monitors/biologists?” – and it would need to teach reliable data measurements and management – reading integrity and traceability – and of course offer the chance of a fact based opinion on water quality in a specific locatiion/stream.
This could become a “reference test system” for putting your own lower cost systems together later – probably by a different group of students as its different skills. Teaches team work as well.

My suggestion for an RS485 based logger with solar power:
arduino.cc development environment,
I recommend ARM based processor (thats where its heading) and for students to be able to have the most extensible environment – 65Kram is good.
https://forum.pjrc.com/ – have ARM based processor with great detailed technical support, including low power.
Teensy3.1 – Processor with 65Kram /256K program memory
http://www.pjrc.com/store/teensy31.html
http://www.pjrc.com/store/sd_adaptor.html

RS485
https://www.sparkfun.com/products/10124

Solar Cell
https://www.sparkfun.com/products/9241

Solar Charger & Battery needs to be same technology – either LiPo (LiFePO4) or LiIon. LiIon is used through out cell phones but can explode/catch fire if discharged too fast
Solar Charger
https://www.sparkfun.com/products/12885
http://www.seeedstudio.com/depot/LiPo-Rider-Pro-p-992.html Max1A $15

LiPo battery
http://www.seeedstudio.com/depot/Crazyflie-Nano-Quadcopter-Spare-battery-BCBL01A-p-1362.html

However, your mileage is likely to vary, these are parts that can fit together lego like, but need an analysis of data and power flow.
If used wrongly they can break/smoke, but other then LiIon batteries are not dangerous.

To start, I would get the Teensy3.1 and RS485 and power supply and Decagon CTD – and get the data from the sensor Decagon CTD. This would verify your toolchain (prjc variant of Arduino) and data flow. I’ve used it and its worked well for me and lots of other people – however your mileage may vary.

Then you build the other parts in “brick by brick”

Hope that overview is useful?