Breath detecting with an environmental sensor

Turns you can do it. I’ve been wondering how I can detect people blowing into a trombone. As you do. A microphone is one possibility, but that involves analogue to digital conversion and sound processing and stuff. And owning a suitable microphone. I do however have a bunch of BMP20 environmental sensors. These contain an air pressure detector. They are supposed to be used for weather data and determining your height above sea level. Would it work for breath?

The answer is yes. If you put a sensor in a closed box (see above) and then blow into the box you can make a detectable difference to the pressure inside. All you have to do is sample the air pressure at the start and then look for a change of around 5 or so during gameplay.

It worked really well for a while. Then the BMP280 stopped working. I had a look in the box and discovered why. It was rather disgusting. Breathing into a box produces not just air, but a lot of water vapour too. The inside of the box and the sensor itself was covered in what you could politely call “dew” but was actually something slightly different. Trombones have a “spit valve” on one end to release all the stuff that accumulates. I’m happy to have proved the principle. I guess I could engineer some baffles or a waterproof membrane over the sensor to keep it dry, but the thought has occurred that in these virus laden times, passing around some thing that you take in turns to breath into might not be a great idea.

So I’m building a version of the controller that uses buttons rather than breathing.