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Topic: Respiration rate sensor (Read 608 times) previous topic - next topic

ggmu5

Hi all,

I am working on some project with Arduino UNO and I need a respiration rate sensor.
It has to be cheap and easy to make. I was searching all over the internet but I didnt
come across any good example, just found a couple of ideas. There is finished product
via e-health platform but it is too expensive and not compatible with UNO.
The best idea I could think of is to use a thermistor to detect temperature from nose
when breathing in and out, but my main concerns are whether it is sensitive enough to
detect the temperature change from breathing and if it is how could i convert that temperature
detection into respiratory rate, I was thinking of graphical display where the amplitude would be
the exhalation since then temperature is higher...

I could use any help :)

robtillaart

temperature sensor is the way to go if the temperature of the environment differs enough from the body temperature. If both are 37C / 100F you can't see the diff.
Rob Tillaart

Nederlandse sectie - http://arduino.cc/forum/index.php/board,77.0.html -
(Please do not PM for private consultancy)

ggmu5

Although I need to finish it by mid of July the temperatures shouldnt be as hish as 37C...and in the room they shouldnt be more than 26-27 so I hope that would do...But is thermistor the best sensor for it, is it the most sensitive for that kind of thing? and how can I put the values of temperature to breath rate?

ggmu5

Hi all,

I am working on some project with Arduino UNO and I need a respiration rate sensor.
It has to be cheap and easy to make. I was searching all over the internet but I didnt
come across any good example, just found a couple of ideas. There is finished product
via e-health platform but it is too expensive and not compatible with UNO.
The best idea I could think of is to use a thermistor to detect temperature from nose
when breathing in and out, but my main concerns are whether it is sensitive enough to
detect the temperature change from breathing and if it is how could i convert that temperature
detection into respiratory rate, I was thinking of graphical display where the amplitude would be
the exhalation since then temperature is higher...

I could use any help :)

DrDiettrich

Which shape and placement of the sensor do you have in mind? Something like a headset microphone, only located at the nose instead of the mouth? Perhaps such a microphone will already provide a useful (pressure) signal?

ggmu5

Well I was hoping to put it under the nose yes, but not like headphones and mic, just with some tape that would hold it there for small amount of time while I mesure, its not permanent solution but I dont need it to be(maybe I can even connect it to a clip and then clip it to the shirt)...I saw how they made it for the e-health platform it is called airflow sensor and it has sensor that goes into nostrils but it is too expensive for me and it isnt UNO compatible (I tried to figure out what kind of sensor it is but they didnt write the description of how its made)...
I didnt think of electric (condensing) microphone, I am not very familiar with it...

robtillaart

the smaller the sensor the faster it can adjust to its environment.

You might need to try different temp sensors, I would go for the watertight DS18B20 (fast),
When set in low resolution 9 bit it can sample several times per second.

to remove noise you can take the (running) average of the temperature.
When the average is going up the person is breathing out / exhaling
When the average is going down ten person is breathing in / inhaling
YOu follow this with a variable  (0 = out, 1 = in)
When that variable changes you update a counter, and after 2 update you have one breath cycle.
Comparing time stamp millis() of the begin of breath cycles gives you the interval.
Dividing 60000 millis by that time stamp gives you the breaths per minute.

That is the theory, your turn to code the above.



Rob Tillaart

Nederlandse sectie - http://arduino.cc/forum/index.php/board,77.0.html -
(Please do not PM for private consultancy)

robtillaart

moderator mode: Merged cross posts
Rob Tillaart

Nederlandse sectie - http://arduino.cc/forum/index.php/board,77.0.html -
(Please do not PM for private consultancy)

ggmu5

Hmmm yeah that could be good enough provided that my measurements will be good enough...Im bit low on my budget since I already spent a lot on other sensors and parts so I dont have a luxury to buy 3-4-5 different temperature sensors and test which one is best for the job (although they are not expensive but still) thats why I asked You guys if You have any experience which one is most sensitive and would be the best for the job...I dont know even what type it should be: thermistor, termocouple, etc...

Paul_KD7HB

I have a customer that manufactures an oxygen supply system for aircraft that uses a Nasal cannula to both sense the beginning of inhalation and then supply a shot of oxygen. I can't disclose anymore, but perhaps you could use a Nasal cannula in conjunction with a microphone to detect breathing.

Paul

ggmu5

That woould be cool but I think it would get me way over my budget...I searched for nasal cannula on the ebay and the cheapest one was not below 6-7$ and thats just one part of the sensor...I think I will most definately go with temperature sensor but my biggest problem is I dont know which type is moste sensitive for this kind of measurement...Should I go with some regular temperature sensor like LM35 or thermistor,termo-couple,...

Paul_KD7HB

That woould be cool but I think it would get me way over my budget...I searched for nasal cannula on the ebay and the cheapest one was not below 6-7$ and thats just one part of the sensor...I think I will most definately go with temperature sensor but my biggest problem is I dont know which type is moste sensitive for this kind of measurement...Should I go with some regular temperature sensor like LM35 or thermistor,termo-couple,...
Go to your local fire station that has on-duty EMTs. Ask them for a nasal cannula that has been opened, but not used. They probably have some that are just laying around.

Paul

m9898

#12
May 17, 2015, 12:36 pm Last Edit: May 17, 2015, 12:36 pm by m9898
To detect airflow through the nasal cannulla, you could use a gage pressure sensor instead of a microphone, so you could easily distinguish between in- and exhalation. Just connect the pressure port of the sensor with a T Connector to the nasal cannula tube and leave one end open.
Maybe you could make that end a little bit thinner to get a bigger pressure difference.

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