In 2020 I noted that you can build a small gadget-charging off-grid solar power system for about $200. In 2021 I deployed it to a spot in the woods of Vermont.
This is largely a tale of what kinda-worked and what I should do better next time.
The full kit:
- 50 Watt "12V" panel (no product link, market constantly changing for this)
- Renogy 10A PWM charge controller
- 12V RV storage battery (many available)
- 10 AWG M4 solar panel cables
- SparkFun wind/rain gauge kit (SparkFun wind/rain gauge kit at Amazon)
- Raspberry Pi 3B+
- Arduino Nano
- a pair of DHT-22 humidity+temperature sensors
- an upturned plastic tote to keep everything and keep the rain off
The Arduino connected to the DHT-22 sensors and did the weird timing-dependent interfacing to those parts and then output their data to the serial port once a second. (The 'serial port' being virtual, connected over USB to the Raspberry Pi.)
The SparkFun weather station mostly outputs tick events, when the rain gauge ticks over or when the anemometer spins (wind direction is analog but I didn't integrate that). I was able to tie it directly to a couple Raspberry Pi GPIO pins, but if I do this over again I'll probably hand off to the Arduino for that too.
The temperature sensors were in the box with all the other components. This was not good and they frequently got hot and reported temperatures over 40C which was pretty unlikely. I should have moved them out into a Stevenson Screen box.
The upturned tote was open on the bottom. I had a few incidents of critters crawling in and one time it got shorted out by a slug. Also while it kept the rain off it could get quite humid and condense water inside the box:
The rain gauge got gummed up by a spider! Most of the summer it was stuck so I didn't get much data out of that.
The other big problem was time. The Raspberry Pi's clock would drift quite a lot, or sometimes the battery would run low after a few cloudy days and then the system would come back some random time later. I could kinda tell from the rise and fall of temperature where the days were, but I ultimately couldn't tell what day or what time of day any weather reading happened at. My solution that I deployed in 2022 was to attach a small USB GPS receiver to the Raspberry Pi and get time from that.
2021 September 26 was the last time I saw it that year. I left figuring I'd get some data until it didn't get enough sun and shut down for the winter. It lasted about another week. The next spring I found it windstrewn with some of the plastic parts 100 meters downwind. In 2022 I built an all new off grid basecamp solar power system.
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