This page is being migrated to the new spectrometry page -- with new activities and upgrades for ...
Public Lab is an open community which collaboratively develops accessible, open source, Do-It-Yourself technologies for investigating local environmental health and justice issues.
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This page is being migrated to the new spectrometry page -- with new activities and upgrades for the various versions of this project. Take a look!
The standard -- plugs into your laptop
Cheap, easy, starter version for smartphones and webcams
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:
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, 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 »
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, 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:
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:
You can also purchase a desktop spectrometry starter kit 3.0 or a foldable smartphone spectrometer kit from our online store
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 the Upgrades section of its documentation.
Along with the physical devices, the Public Lab community has also developed Spectral Workbench, 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:
Frequently Asked Questions can be found here »
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. Some of the challenges that remain include:
While many of us have focused on identifying oil pollution with fluorescence spectrometry, 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:
The Homebrew Sensing Project is made possible in part by the generous support of the John S. and James L. Knight Foundation, Knight News Challenge: Health.
You can also purchase a desktop spectrometry starter kit 3.0 or a foldable smartphone spectrometer kit from our website
Rigid plastic version which attaches to your smartphone
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
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:
Since different oils fluoresce in different colors, this technique can be used to match an unknown sample with a reference sample to identify it.
The Public Lab Spectrometer is a Do-it-Yourself device made from simple materials:
The DVD's tightly packed grooves act as a diffraction grating -- like a prism.
The above link offers step-by-step instructions on making your own spectrometer. It features:
Though these specs look pretty good, they still need to be compared rigorously with a traditional laboratory spectrometer. Are you interested in trying it?