It’s been a long time since I posted, and you’d be forgiven for thinking the Cave Pearl Project was yet another victim of COVID. While the attendant travel restrictions did require replacement of entire field deployments (due to battery leakage) we are still very much alive & kicking. Several sensor development & student projects are on a slow burn, but unfortunately that also involves a ‘soft embargo’ on the newest toys until certain students finish their papers...

Anyway, at this point we’ve proven that it IS possible to teach a ‘hands on’ instrumentation courses over zoom. Though that required removing soldering from the labs - something which is highly suboptimal from a fieldwork perspective. Other teachers stepped into the breach with us, and with feedback about their time & budget limitations we've developed a new 2-Part ‘EEprom only’ version of the logger which handles all download & control through the IDE’s serial monitor window. Unix timestamps are reconstituted from the record number during download which means none of the limited storage space gets used for that predictably repeating sequence.

A typical sleep current below 5uA means this new data logger will easily run for a year on the CR2032 backup coin cell that’s already attached to the RTC module, and unlike just about every other low-power Arduino project we haven’t used custom fuse settings or bootloaders to lower the BOD. With a 220uF tantalum  buffering the rail none of that annoying confabulation is necessary. Add a couple of cheap 32 or 64k EEproms and you have the perfect platform for low power sensor ICs like the BH1750, BMP280 or the SiLabs7051.  This may well be as minimal as it is possible to get and still offer beginner level students an opportunity to develop their own final projects.

https://thecavepearlproject.org/2022/03/09/powering-a-promini-logger-for-one-year-on-a-coin-cell/