Handheld Sky Quality Meter with GPS and SDCard data storage. This is a byproduct of my AstroWeatherStation as people asked me if I could isolate the SQM feature and bundle it separately.
This is still under development. Most of the code base comes from my weather station but additional code needs to be written (SDcard, data retrieval, operation modes, ...). I am also still looking for the right housing to accomodate all the parts, so the hw layout is not done yet. Protoyping on breadboard is done, though.
A first set of features work:
- SQM
- GPS
- Led display of NELM or MSAS value
- Last MSAS/NELM/GPS data retrieval via web server
Features to come:
- Continuous vs. Manually triggered MSAS measurements
- Data storage on SDCard
- Data retrieval via web server
- On/Off web server
It can be made standalone by having a waterproof housing and cable gland to provide power (USB). A solar panel version can also be made but would require a few changes in the power supply as the TP4056 requires a different setup to deal with fluctuating solar panel voltage, conversely a DD04CVSA could be used as it is designed to do load sharing. The GPS could also be removed if it is standalone to make some room and reduce the cost.
Draft BOM with avg. prices in CHF:
- Wemos D1 mini ESP32 (3.50)
- Neo-8m GPS (10.-)
- TFCard reader + Card (5.-)
- 4 red digits HT16K33 (3.50)
- TP4056 charger (4.50)
- FQP27P06 mosfet (0.50)
- SR240 diode (0.10)
- TSL2591 (4.50)
- Si7021 (1.50)
- 2000mAh Li-ion battery (4.-)
- Cables (1.-)
- Perfboard(s) (1.50)
- Housing (4.-)?
- Some switches (1.50)
- 20°FoV lens (0.25)
- Some screws (0.50)
- JST XH (0.10)
- Various headers (2.-)
- Female micro usb (0.60)
- Male micro usb (0.2)
- Optional external GPS antenna (3.-)
I think that the overall cost of material should be around CHF 50.- if you do it yourself, all parts sourced from aliexpress, which is way cheaper than a commercial SQM. With the pleasure of doing it yourself, of course :-)