The project consists of the following elements:
- Solar panel
- LiIon battery (3.7V 2500mAh)
- LiIon/LiPoly USB charger
- Arduino Uno
- Sparkfun microSD shield
- 8GB microSD card
- Various USB adapters
I am getting upwards of 8V from the solar panel in moderate sun. The entire system seems to only be drawing around 40mA. I suspect this is because the Arduino Uno draws about 40mA and the microSD shield draws a negligible amount in comparison.
|Testing the panel + battery + charger
|Close-up of microSD shield
|Panel in a bag for weather protection
|Action shot - on window ledge gathering sun + data
|Consolidated package using found surveillance mount
Data is written to the microSD card every 200ms - a timestamp of milliseconds since startup and a reading from the electret microphone in volts. My latest test was foiled because the microSD card got wet and stopped logging shortly after startup, but I was able to get a solid chunk of real data last week and this is presented below.