My girlfriend needed to know if a particular area got enough sun for work so I built her a portable, weather-proof, PPF(μmol m-2 s-1) logger that’s also solar powered.
- Solar Cell Small – 0.45W
- Pelican 1010 Micro Case, Black with Clear Lid
- Adafruit Feather 32u4 Adalogger
- Adafruit TSL2591 High Dynamic Range Digital Light Sensor
- USB DIY Connector Shell – Type Micro-B Plug
- Lithium Ion Polymer Battery – 3.7v 500mAh
- Misc. headers and wire
The only weird thing I did was making cables using solid core wire because I ran out of stranded wire. I’ll have to redo these in the future. I stuck the solar panel and sensor to the inside of the lid using thermal tape and so far it is holding up. The Adalogger is great because it doesn’t require any additional hardware to connect and charge a lipo battery. It’s also low power and easy to work with. Since the TSL2591 measures in Lux a conversion factor is required to convert to ppf. The nice thing about the TSL2591 is that because it filters out UV using two diodes (one with a UV filter) you can get a rough reading of the spectrum we are looking for which is PAR (400-700 nm). I used apogee instruments website to figure out the necessary conversion factor for sunlight (0.0185) to log lux as ppf at our desired interval and write it to the SD card.