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What Does It Do?

The Coqui: using audio as a sensor data format. We're exploring using audio frequencies to convey sensor readings -- like a modem, but even simpler -- in order to make sensor readings more accessible for people (or to enable data transmission over ubiquitous audio jacks on PCs and smartphones). Look for recent updates on Public Lab here.


This is a list of community-generated guides for specific applications using your coqui. These activities can be categorized, and some may be more reproduced -- or reproducible -- than others. Try them out to build your skills, and help improve them by leaving comments. Together, we can repeat and refine the activities into experiments.

Activity grid

Add an activity  or request an activity guide you don't see listed

Activities should include a materials list, costs and a step-by-step guide to construction with photos. Learn what makes a good activity here.

Add your own activity Request an activity guide

Guides should include a materials list and a step-by-step construction guide with photo documentation. Learn what makes a good activity here.

Frequently Asked Questions

Ask a question about the Coqui

Title Author Updated Likes Comments
Do you have any tips for splicing DVD-Rs for spectrometer builds? @mimiss about 2 months ago 2
Measuring UV-C Sources @jkenny23 3 months ago 4
What light sources might I use to calibrate my spectrometer if I don’t have a CFL available? @mimiss 3 months ago 3
Problem whit workbench spectra. Unable to manipulate(work) whit any image @damian_orovitz 3 months ago 1
How can I get the menu to calibrate SpectralWorkbench? @experimentierwerkstatt_dm 4 months ago 9
what are the best light sensors? @omarion 11 months ago 4
Aside from a wavelength calibration, has there been any discussion on doing some sort of intensity calibration to allow measurement of spectral irradiance? @Light_Guy60 about 1 year ago 1
I just gotten my newly purchased Infragram Pi Camera, my pi.local is blank and pi.local/Cam keeps popping up message "Error in RaspiMJPEG" hence I do not get any live video feed. Anyone can help? @willieong about 1 year ago 1
How do I identify the base polymers in an unknown plastic for recycling? @profpearce about 1 year ago 7
Can you help us with calibrating our spectrometer? @KristinaTamara about 1 year ago 7
Split DVD – which part to use for spectrometer @Nelari about 1 year ago 5
Can you give me measure for spectrum? Thank you. @Skorex over 1 year ago 2
What causes spectrum distortion? @nathanathan over 1 year ago 1
How can I connect my gopro to SpectralWorkbench software? Is there other open software that would? @CD3000 over 1 year ago 3
UV measurements @exekutive almost 2 years ago 5
[SOLVED] Why is my image of the spectrum extremely "slim"? DVD+RW is not good as a diffraction grating! @jaksch about 2 years ago 7
How can I get the absorption spectra once I have calibrated my spectrometer data? @amenzel8 about 2 years ago 1
Most accurate spectrographs? @jneish about 2 years ago 1
Best light source for spectrometer? @jneish about 2 years ago 2
How to measure nutrient concetration in hydroponic system? @Aleksi12358 about 2 years ago 14
Dark images, can't get spectrometer to work @Tomas0413 about 2 years ago 55
Can I use a DVD or does it have to be a DVD-R ? @tmanmerlin about 2 years ago 14
could anyone tell me if it is possible to use the homemade spectrometer to analyze a sample of metal? @gabrielxp46 about 2 years ago 3
How do the new webcam @stinge_nz over 2 years ago 14
Which Public Lab kit is best for testing the impact of different camera settings? @MaggPi over 2 years ago 3
Do a DVD is provided with the LEGO kit ? ty ! @adamsanta over 2 years ago 1
can a spectrometer be used to measure color of water ? @thangvu over 2 years ago 16
Quantitative analysis of wood moisture @MarcioPamplona over 2 years ago 9
How do I make sure the "YELLOW LINE" threshold is the same for each measurement with the spectormeter (trying to maintain consistent conditions for experiments across multiple days) @Dr_Z over 2 years ago 3
Lego Spectrometer suitable for studying sunlight? @jsbonillam over 2 years ago 12
Possible sources of more spectrometer information @Ag8n over 2 years ago 3
Can I get a file of numbers instead of a graph from the foldable spectrometer software? @mountevans over 2 years ago 4
How to interpret the results? @amir129 over 2 years ago 10
Preferred slit size? @asnow over 2 years ago 6
Do I need to use a DVD-R? Will a CD-R work too? @jordankc over 2 years ago 2
Camera that would detect at 1064nm? @jpschaaf over 2 years ago 2
Whats the detection limit of the Desktop Spectrometry kit? @partyparrot4eva over 2 years ago 3
Quantifying Phytonutrients using a Spectrometer, Possible? @zayas over 2 years ago 7
I want to know a method to quantify milk proteins using the foldable mini spectrometer, Is this possible? @julsmill over 2 years ago 3
How can we detect contaminants in water samples with a DIY spectrometer using reagents? @warren over 2 years ago 1
Can a DIY spectrometer be used to measure water turbidity? @warren over 2 years ago 8
Noise when Trying to Analyze Spectrum @matthart610 over 2 years ago 1
Does anyone know what image processing spectral workbench does to find intensity at wavelength/ where to find the coding for that? @Reallygeek over 2 years ago 10
Does the Beer Lambert law apply to the opacity of reagents? @warren over 2 years ago 4
Would the desktop spectrometry kit work for measuring fluorescent responses? @ICSK over 2 years ago 7
Can I use a Diffraction Grating Slide Holographic 1000 lines/mm instead of the CD? @oglezsa almost 3 years ago 3
How to connect a creative cam notebook with a smartphone? @KushalKC almost 3 years ago 2
What's an easy way to compare two liquid samples with a spectrometer? @warren almost 3 years ago 8
Calibaration or switching scale? @jayjay70 almost 3 years ago 1
Spectrometry: degrees between gratings or camera and baseline @obisidian about 3 years ago 1
How To Make Time Lapse Spectrometer @LightWaveResearch8000 about 3 years ago 2
Assembly completed but the camera doesn't work. @1987123 about 3 years ago 4
Desktop Spectrometry Kit to arduino? @jjoll about 3 years ago 5
Any way to improve on the DVD grating? @dsvilko about 3 years ago 2
Can a Spectrometer be used to detect material type? @jjoll about 3 years ago 3
Can this camera be suitable to make a spectrometer v3.0? @osetroff about 3 years ago 3
Alternative spectrometry sample cells for Hach DR900 @fieldlab over 3 years ago 0
Desktop Spectrometer Kit Availablility @bicwood over 3 years ago 3
How do I... @Mekis over 3 years ago 1
Testing Water For Specific Polluting Compounds @rajanzaveri over 3 years ago 2
Paper size for stiff matte black card insert @Vman over 3 years ago 1
making a slit in spectrometer @vafa over 3 years ago 1
JDEPC-OV05 camera intelligent exposure @tim_spec over 3 years ago 5
what causes spectral colors to be reversed? @vgoebel over 3 years ago 2
Fraunhofer Lines at higher resolutions? @stef over 3 years ago 2
How to get spectral data in excel or other formats @suha over 3 years ago 4
Ambient/Light Bulb Testing @idev247 over 3 years ago 11
Photoreactive purple dye: can it block wavelengths longer than green? @axman over 3 years ago 2
Identify Plastic Material Using Infrared Imaging @shaikhgous over 3 years ago 1
Is the webcam from spectrometer v2.0 suitable for the upgrade to 3.0? @pablo over 3 years ago 16
Is there an iPhone app for foldable spectrometer? @CanfieldC almost 4 years ago 4
Error on calibrating uploaded spectrum @sarahcm almost 4 years ago 9
How do you use infrared light with the DIY Public Lab Spectrometer 3.0? @haribhimaraju almost 4 years ago 2
how to delete my spectra on Spectral Workbench @redleon almost 4 years ago 1
What are good containers to use for spectrometry samples? @warren almost 4 years ago 1
Can I upgrade a DIY spectrometer with a Raspberry Pi camera? @warren almost 4 years ago 10
What sensor would I need to detect spectra of small organisms (virtus, bacteria etc) @fouadalnoor almost 4 years ago 4
How can I reduce ambient light inside the Desktop Spectrometry Starter Kit? @warren almost 4 years ago 8
What mechanical specs can and should PLab spectrometers meet? @stoft almost 4 years ago 19
Arc Emissions- What electrodes to use? @m3sca1 almost 4 years ago 2
Is there a simple and reliable way to test the rigidity of the spectrometer? @bsugar almost 4 years ago 6
How can a spectrometer's wavelength resolution be measured? @warren almost 4 years ago 1
Can i upload csv files on spectralworkbench for calibration and other purposes? @shubham almost 4 years ago 1
How to neutralize/remove the source's spectra to obtain absorption spectra? @shubham almost 4 years ago 12
Spectrometer from a drone @sylvainbonhommeau about 4 years ago 7
Question: Can DIY-spectrometer be used for analysis of soil @interestedperson_ha about 4 years ago 7
Question: Using a webcam with a image resolution of 1920x1020 @seko about 4 years ago 1
Mini spectrophotometer - how does this deviate from the Beer-Lambert law? @FoxClass about 4 years ago 9
How to rename a set on Spectral Workbench? @AndrewJamesLaplante about 4 years ago 4
Question: How do I get the calibration user interface? @PeterDH about 4 years ago 3
Question: Why average? And what happens to the second Green? @viechdokter over 4 years ago 10
Question: Calibration... @Georgi over 4 years ago 2
Question: Focus on mobile phone @clownfish over 4 years ago 1
Question: I want to do citizen bee science @FortunaWolf over 4 years ago 7
Question: ccd camera on metascop @leanr over 4 years ago 7
Getting the spectrometer to work with a Raspberry Pi? @anjohn12 over 4 years ago 6
Question: How to I convert the spectrum from the webcam to a spectral power density graph. @cjtiaan over 4 years ago 5
Question: RE: Desktop Spectrometry Kit @Airship7 over 4 years ago 0
Question: Desktop Spectrometry Kit @clmchenr almost 5 years ago 3
Question: Can signal be exported from Spectral Workbench? @clmchenr almost 5 years ago 1
Question: Range @Gasam about 5 years ago 1
Question: IR filter in the camera @Ripingill over 5 years ago 6
Question: the camera look only white and dont have´s teh camera bad? @masolaric almost 6 years ago 4
Question: Will the desk top spectrometer sense wear metals in motor oil? @upson almost 6 years ago 1
Sample container search @warren almost 6 years ago 12
Question: More of a comment, really @bowlerhatman about 6 years ago 8
Accuracy of assembled Desktop Spectrometry kit? @WhiteRabbit about 6 years ago 8
Question: Can the Public Labs Desktop Spectrometer analyze light from a patch of grass? @WhiteRabbit about 6 years ago 6
Question: any low light settings for web cam used in desktop spectrometry kit? @Henry0815 about 6 years ago 7
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Ask a question  or help answer future questions on this topic


A Coqui is a simple, inexpensive, open source device that generates an audible tone that is based on any electric resistance-based measurement. For example, a Coqui can measure:

  • conductivity of liquids
  • temperature
  • ambient light

Build a Coqui

Instructions on the breadboard-based "BBv1.0" edition of the Coqui can be found here:


  • For more information about the Coqui, post a question to the "water quality" mailing list here) (also listed in the left sidebar)
  • The github repo for a PCB version of the coqui is here

The Coquí is a circuit that allows you to 'hear' the readings from various sensors. Once the Coquí is assembled, you'll be able to 'hear' the conductivity of a solution, the temperature of a room, or the color of a pH test strip.

The design was named (onomatopeically) after the several species of small frogs which have a loud, distinctive call at night.

Demo Coqui applications


Building your own Coqui

Building Coqui sensors