A sensor to detect breathing

[absolem]

Hi everybody!

I'm a visual artist and currently working on a project for an exhibition. It includes a cube with LEDs installed inside and a peephole. When the audience look into the peephole to see inside the box, a sensor would sense their breathing, so it could change the brightness of the LEDs according to it—breathing out would equal brighter light, breathing in would decrease the light's intensity.

So my question is: is there any sensor that would enable me to do this? I'd prefer a cheap one - and I need it to be small.

Any tips would be HIGHLY appreciated,

Anna

[Guillermo Schimmel]

@absolem I would try the audio way.

A microphone near the mouth place could detect very different sounds.

I dunno if the usual mic modules do that or you would need to manually make a circuit with two bandpass filters in order to get the 3 states. (nothing, in, out)

[Guillermo Schimmel]

@guillermo-schimmel Combining mic with temperature would also work. Mic for breath, temp for direction. There are some temperature modules very responsive.

[artag]

A hot wire (hot bead) anenometer is often used to measure breath eg in respiration masks. They're a wire or thermistor slightly heated by the cuirrent passing through them. When air is passed over them, they're cooled and the resistance change gives a measure of air speed. Need correcting for temperature if accuracy is required.

[Jokgi]

@absolem Check out the css811 sensor. It can detect CO2 such as we al know we exhale with every breath. This is the same device used on the Nordic Semiconductor “nRF52 Thingy”.

http://infocenter.nordicsemi.com/index.jsp?topic=%2Fcom.nordic.infocenter.rds%2Fdita%2Frds%2Fdesigns%2Fthingy%2Fhw_description%2Fhw_descr.html

[bjacobse]

@artag
Yes I agree, the anemometer should also have a very short responsetime, so it's possible to sense breathing