##Public Lab's Do-It-Yourself spectrometers are designed to help everyday people detect pollutants where they live.
Our community has been working since the 2010 Deepwater Horizon oil spill to develop a cheap, open source, Do-It-Yourself spectrometer which we hope to use to identify oil pollution in soil and water, as well as a range of other possible contaminants.
Colored light is often a blend of different colors. A spectrometer is a device which splits those colors apart, like a prism, and measures the strength of each color. A typical output of a spectrometer looks like this spectrum of the daytime sky, with the actual light spectrum at the top and the graph of wavelength (horizontal axis) and intensity (vertical axis) below:
##Types of spectrometry
There are different ways to use spectrometers, and the key difference is how you illuminate your sample.
This project focuses on fluorescence spectrometry in order to [identify oil pollution samples](/wiki/oil-testing-kit), which is where a high-energy light like an ultraviolet laser is used to excite a sample so that it fluoresces, or glows.
See the lead image of this page for a diagram of a fluorescence spectrometer setup. Since different oils fluoresce in different colors, this technique can be used to match an unknown sample with a reference sample to identify it.
Read more [on the Oil Testing Kit page »](/wiki/oil-testing-kit)
Emission spectroscopy is the kind often done in the classroom, where burning a material emits a colored flame. A spectrum of this colored flame can be used to match a material, but it can be unsafe to burn unknown samples, so we have primarily begun to use this technique to attempt to [monitor distant flares](/wiki/refinery-watching), for example at gas refineries in Louisiana, to try to detect heavy metals.
[image of refinery watching]
Absorption spectroscopy -- shining a full-spectrum light like a halogen or incandescent (not a fluorescent or laser) through a sample to see what colors are absorbed -- is a bit more difficult in the visible light range, as most of the "fingerprint" features of spectra are too long or too short wavelengths for our webcam-based devices. However, a considerable amount of work has been done on absorption spectrometry of:
##Make a spectrometer
The links at the top of the page offer step-by-step instructions on making your own spectrometer. Our main design, the Desktop Spectrometer features:
* around 400-900 nanometer range, maybe wider (what you can see with the naked eye, plus some infrared)
* 1-5 nm spectral resolution
* 20-30 samples per second
* ~ $15 in materials
* < 1 hour construction time
* web-based, [open-source software](/wiki/spectral-workbench)
Once you've built a spectrometer, there are many ways to improve it -- by using a narrower slit, darkening the interior, using a better camera, and more.
For upgrading the USB webcam-based Desktop Spectrometry Kit, see http://publiclab.org/wiki/dsk#Upgrades
Along with the physical devices, the Public Lab community has also developed [Spectral Workbench](https://spectralworkbench.org), an website to capture data with your spectrometer, analyze and compare spectra, share them in an open database, and comment and collaborate with others.
The software includes:
* direct connection to your USB-based or smartphone-based device
* calibration, comparison, and matching tools
* XML, JSON, and CSV data download
* offline mode
* read more [in the documentation](/wiki/spectral-workbench)
Frequently Asked Questions [can be found here »](/wiki/spectrometer-faq)
This document, and this methodology, is still under active development. What you see on this page is only the best attempt so far at collating and presenting the [work of Public Lab contributors to date](/tag/spectrometer). Some of the challenges that remain include:
* easy auto-calibration of the device (see progress by @sreyanth)
* easier and more consistent [sample preparation methods](/wiki/spectrometry-sampling)
* additional challenges specific to oil identification can be found on the [Oil Testing Kit page](/wiki/oil-testing-kit)
While many of us have focused on [identifying oil pollution with fluorescence spectrometry](/wiki/oil-testing-kit), there are many other uses for cheap, open source spectrometers, and many other ways to use a spectrometer.
In 2012, Public Lab ran a Kickstarter project to distribute an early version of our DIY spectrometers to over 1600 people. The video is a bit out of date, but is still a compelling way to understand what we're attempting to do:
Desktop Spectrometry Kit v3
The standard -- plugs into your laptop
Rigid plastic version which attaches to your smartphone
Cheap, easy, starter version for smartphones and webcams