So, we spent a few weeks working through some of the basic atmospheric science presented in the book. Then, I got started building a prototype UV data logger based on a couple of RadioShack UV (405nm) LEDs. I started with the logger running on a PicAxe 08M chip. I encountered problems that I later found had NOTHING to do with the PicAxe. I was working my way to the bottom of my sporadic voltage reading issues where the numbers coming out of the ADC would randomly climb and then drop back to 0. I figured it was related to my poorly structured circuit and/or the very small number of electrons produced by the LEDs.
I switched to an Arduino but I still had the same issues — that didn’t surprise me. But it made me feel better. Then I was determined I needed to handle the very low ampere output of the LED better and wired it to a unity gain OpAmp circuit based on the one that Forest Mimms III presents in that Makezine article I referenced above. That worked like a charm! I extended it a little bit because I reason that, since the LEDs are so directional in their detection of light, that I’ll need at least four pointing outward spaced 90 degrees apart. My hope is that, if I average the values of all four LEDs we’ll be able to detect the trend in UV light intensity and factor out the angle of the LEDs with respect to the sun.
Here is a sneak peak at my very first prototype that seems to work:
Here’s how it looked when I figured out how to put the circuits inside the the official UMaine provided enclosure:
I’ve got a few different pieces of code I’ve written for handling this datalogging and testing process. However, I’ll save that for another post.
And just in case you haven’t seen the Sun and Sky Monitoring Station: