I recently had the good fortune to discover for myself Public Laboratory (www.publiclaboratory.org) and one of their magnificent projects, Spectral Workbench (www.spectralworkbench.org). I was on a spin bike at the gym and read an article in the science column of Popular Mechanics in which the writer touted the resources and the do-it-yourself plans for building a homemade spectrometer.
The science department at my school ordered a few of the kits to build the spectrometers, since they were only $40. Now that I’ve built one, I see how easy it would be to truly build your own. During construction, it is necessary to adjust the focus on the web cam to 9 inches, which proved to be the most challenging piece ( had to install some web cam software on my work laptop ). Once you’ve built the device, it is time to join Public Laboratory so that you can save results and participate in their message boards.
With the device built and plugged into the laptop, I logged onto Spectral Workbench and chose “Capture Spectra”. Chrome browser alerts you that the website wants to use a camera on your computer. From there I needed only to be able follow the well documented (though nearly intuitive) procedures for capturing sample spectra. From a seated position at my desk, I was able to point the spectrometer toward the ceiling fluorescent fixture and get a quite good first spectrum. However, the result lacked a wavelength correlation. So, I followed the directions to calibrate the device against the mercury spectrum of a compact fluorescent bulb.
Once you have completed the calibration, all spectra that you collect will be scaled to the initial calibration. Though the spectra are only in the visible range, it would be possible to obtain near infra-red if you successfully remove the IR filter from the web camera. However, the directions that come with the kit are insufficient to successfully remove the filter. I took a webcam completely apart in order to figure out how to safely get the filter out, but ruined that camera in the process. My next goal is to set up the next kit with no IR filter.
There are so many uses for such a device in the chemistry and biology classroom and lab. We will certainly be using these next year when doing flame tests for cations. I encourage you to try it out and add your discoveries to the growing community at Public Laboratory.