If you’re at all concerned about the quality of air you’re breathing, you might be interested in an air quality sensor. For example, the Awair 2nd Edition is available on Amazon for $173, has great reviews, and not only detects particulates, but also chemicals, carbon dioxide, and measures humidity and temperature. It also has Alexa integration and a companion mobile app.

For a lot less than this, if you’re willing to forgo some of the features, you can make your own sensor, like the one pictured above, for around $36. I’ve sourced the key components from Amazon, but that’s only because I’m lazy (and please note: these are not affiliate links; I’m not getting compensated for any of this). If you source from eBay or larger components retailers like Mouser, you might be able to bring the cost down a bit.

Here’s your shopping list:

1. mini OLED display from Amazon for $7
2. Arduino Uno from Amazon for $8.49
3. Dust sensor module from Amazon for $19
4. 9V battery connector from Amazon for $6 (pack of 5)

So what does this version do? Basically it uses Sharp’s GP2Y1010AU0F particulate sensor to measure dust and other stuff in the air, measured in micro-grams per cubic meter of air volume. You might be a bit skeptical about this (my picture shows nothing detected) but place this device on a carpet surface and stomp around it, and you’ll be surprised (or maybe grossed-out) by what the sensor measures. If you want to geek out the spec sheet for the module has all kinds of detail about how it works, including a reference guide for what constitutes “excellent” (0-35 μg/m^3) and “average” (35-75 μg/m^3) air quality.

OK, so how do you build one?  Easy:

1. Source the parts above. I didn’t mention wires for connecting the components, but these are super cheap and you don’t have to use prototyping connectors; you can also solder the connections if you want.

2. Wire everything up.  The OLED display connections are: SDA->A4, SCL->A5, GND->GND, VCC->5V.  The sensor module comes with a connector with 4 leads: yellow wire-> D7, blue wire->A0, black wire->GND, red wire->5V.

3. Load the sketch onto the Arduino Uno. I’ve saved the sketch file (.ino) and the two .stl files here.

4. 3D print the base and display holder. I tried to make this a single object file, but both pieces print better for me (Ender 3) as separate pieces. I super-glued the display bracket to the main base.

That’s it! Breathe easy.