OK now that we have introduced both the RTC and the SD card and verified that they're working, we can move onto logging!

We'll use a pretty good & detailed demonstration to show off the capabilities of this most awesome data logging shield: We'll log both temperature and relative light levels to determine:

1. How much does the temperature in a fridge vary as the compressor turns on and off?
2. Does keeping the door open cause a big temperature drop? How long does it take for it to cool down?
3. Does the light inside really turn off when the door is closed?