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Coqui conductivity sensor

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What Does It Do?

The Coqui: a simple device to read a sensor via an audible tone. 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.

Purpose Category Status Author Time Difficulty Replications
Coqui BBv1.0 - - @donblair - - 1 replications: Try it »
DIY Science Lesson with the Coqui - - @pdhixenbaugh - - 0 replications: Try it »
Build a Coquí: A Simple Water Conductivity Sensor build review-me @akshaya 1h easy 3 replications: Try it »
Sensor Journalism: A Guide for Educators - - @kanarinka - - 0 replications: Try it »
How much are Coqui measurements affected by hot/cold water? - - @warren - - 0 replications: Try it »
Adding a jack to the Coqui build - @imvec - - 0 replications: Try it »
Analizing the signal of the Coqui using Audacity - - @imvec - - 0 replications: Try it »
Making a DIY conductivity probe from a water bottle and metal screws build draft @donblair 1h easy 0 replications: Try it »
Coqui BBv1.0: Testing conductivity of a solution observe draft @donblair 1h easy 1 replications: Try it »
Coqui draft board design on Upverter - - @warren - - 0 replications: Try it »
Coqui BBv1.0: Assessing Ambient Light with a Photoresistor observe draft @donblair 1h easy 0 replications: Try it »
Riffle Device: Water Conductivity Sensor - - @rebeccah - - 0 replications: Try it »
Coqui BBv1.0: Reacting to an LED with Sound verify draft @donblair 1h easy 0 replications: Try it »
Coqui PCB + audio jack build proposal @donblair - - 0 replications: Try it »
Coqui wave audio recording - - @imvec - - 0 replications: Try it »
Coqui BBv1.0: Using a thermistor as a temperature probe verify draft @donblair 1h easy 0 replications: Try it »
Show 6 more

Add an activity  or request an activity

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

Frequently Asked Questions

Title Author Updated Likes
How can we adjust the frequency of the coqui? @liz 19 days ago
How can we adjust the volume of the coqui? @liz 19 days ago
Will this single timer work for the coqui? @asnow 6 months ago
How much are Coqui measurements affected by hot/cold water? @warren about 4 years ago
Accessible procedure for calibrating conductivity measurements? @donblair over 4 years ago

Ask a question  or help answer future questions


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:


  • The github repo for a more permanent printed circuit board 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

Parts list

See the initial parts list here: #13459 and #11209 for a DigiKey shopping cart link at $19 per kit. And @kanarinka mentions:

there are a couple other things that are helpful to have that are not shown (like the probe made from the top of a water bottle with two screws in it and alligator clips to attach that to the breadboard)

Scans of an invoice from DigiKey:



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