Watchy CO₂ sensor watch

Open source watch/wearable CO₂ sensor for COVID safety

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An add-on board for the Watchy open source watch to turn it into a wearable CO₂ sensor to maintain air quality awareness for COVID safety.

The relationship of CO₂ sensing to COVID safety can be found at a number of places, for example (and more at ).  Briefly CO₂ levels measure the amount of human breath in your vicinity, which is a reasonable proxy for the number of particles of an infectious airborne pathogen potentially in your vicinity.  There are some caveats, mostly related to indoor air filtration systems which can potentially remove (very small) virus particles but not (much smaller) CO₂ molecules, but it's still a reasonably interesting parameter to monitor when you're in a new or unusual setting.

There are four parts to this project:

* A PCB to interface the Sensiron SCD40/41 sensor to the watchy:

* A modified case for the Watchy:

* Source code for the Watchy watch face:

* And, of course, the open source Watchy itself!

Lots of details on github at those three repositories, and on SQFMI's page for Watchy.

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Richard Audette wrote 10/31/2021 at 15:04 point

I love this idea.  Earlier this year, I was reading everything I could find about measuring CO2 and using it as a risk proxy for Covid-19.

I assembled a mobile monitor, and wrote about it here:

In the article, I suggested a "watch" format for this type of sensor would be great, and mocked it up - but it's cool to see you have actually built one. Awesome!

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Ken Yap wrote 10/28/2021 at 04:03 point

What would be nice is a Bluetooth connection to a smartphone to upload the CO2 readings to a website that would display readings from crowd contributions about locations on a map so that people can see where the air quality is worse.

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C. Scott Ananian wrote 10/28/2021 at 12:59 point

Totally possible with this hardware: the watchy has a bluetooth radio.  It also has wifi, but it doesn't have GPS.  So you'd want to do the location tracking on the smartphone and then connect periodically to the watch to correlate the smartphone location with the watchy co2 reading, then upload the results.

I think there was some effort at a hardware hack to add GPS directly to watchy, which would be another approach.

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Ken Yap wrote 10/28/2021 at 13:38 point

You'd probably want to do as much as possible on the smartphone anyway as it's far more capable, and can host an app that can upload (anonymously if desired) the readings. So the watch is just a peripheral sensor to the smartphone.

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