Detecting very small amount of movement such as breathing (not PIR)

I’m trying to find a sensor that will detect very slight movement if placed on the stomach. The purpose of my application is to detect if breathing stops for x amount of seconds. One sensor
I’ve found is a gyro sensor that looks to be what I need but I can’t confirm whether or not this will detect this small amount of movement: Adafruit MPU-6050 6-DoF Accel and Gyro Sensor

Perhaps you could make a mechanical arrangement that resonates at typical breathing frequencies thus building up a movement that is large enough to measure. Think jello on a spoon.

Try it. Don't forget the 2 corner cases: "no rotation" and "no acceleration".

Interesting challenge. Will the person have many blankets on that the sensor will have to deal with? How slight of breathing are you hoping to measure? (ie, up and down 10mm? 1 mm?)

What about using an IR distance sensor, suspended above the person pointing at their chest? Something like this from Adafruit? Then to detect an absence of breathing you just check to see if there is any distance change in a certain amount of time.

Getting a sensor being affected by small movements is not the challenge. Getting the signal out of the noise is.

I found this page. Maybe it gives you a couple of ideas. It looked like an good overview of some sensing technologies that have been tried and it had some points about filtering.

That's a good find.

Be interesting to see how you test this ?
Suppose someone dies and your program doesn’t detect it , how would that pan out?

hammy:
Be interesting to see how you test this ?
Suppose someone dies and your program doesn’t detect it , how would that pan out?

Could possibly be used to detect sleep apnea

I was thinking about how a polygraph (lie detector) works to detect breathing I found this

Respiratory rate - Two pneumographs, rubber tubes filled with air, are placed around the test subject's chest and abdomen. When the chest or abdominal muscles expand, the air inside the tubes is displaced. In an analog polygraph, the displaced air acts on a bellows, an accordion-like device that contracts when the tubes expand. This bellows is attached to a mechanical arm, which is connected to an ink-filled pen that makes marks on the scrolling paper when the subject takes a breath. A digital polygraph also uses the pneumographs, but employs transducers to convert the energy of the displaced air into electronic signals.

jmanatee:
Could possibly be used to detect sleep apnea

The sleep apnea test I had was a sensor that was placed just below the nostrils, sorry can't remember anything more about the sensor.

exhale=warm, inhale=cold? at least if your ambient temperature is low enough ...

zwieblum:
exhale=warm, inhale=cold? at least if your ambient temperature is low enough ...

Hot (warm?) wire anemometer maybe -

Best is to get a sleep apnea machine but they are expensive. Can you get some type of mask, the one that goes under the nostrils is called a pillow mask, there are also full face masks. Then use a sensitive differential pressure sensor on the mask air tube. Try this link for a sensor: MEMS-based Pressure Sensors | NXP Semiconductors.
What I would recommend is talk to your doctor and if he agrees have a full blown sleep apnea test. Most insurance will pay if you have the correct symptoms. This response is to help you get started in solving your problem, not solve it for you.
Good Luck & Have Fun!
Gil

I have had two sleep apnea tests - one in a hospital and the 2nd one was at home - they sent a box of things that I stuck and strapped on me - my current machine senses when I have an apnea event and adjusts a bit to minimize them and also keeps track of lost f things including interrupted breathing - if you think you have an issue easiest and best to have a regular test - the machines today are not too bad to use

If the motion would change the distance apart of 2 flat pieces of metal you could measure changes in capacitance between them.