Cheap AND simple respiration detector

Discussion in 'Electronic Design' started by Neon John, Jan 6, 2014.

  1. Neon John

    Robert Baer Guest

    Robert Baer, Jan 7, 2014
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  2. Spirometer? I like the name.


    Spehro Pefhany, Jan 7, 2014
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  3. Dunno, I first read most of those in full dead-tree mode.

    You can buy a CD with all the articles on it for less than $30.. HTML,
    which you could easily edit to render in fuschia (#FF00FF) on a teal
    (#008080) background if it makes you happy.

    Spehro Pefhany, Jan 7, 2014
  4. Neon John

    Glen Walpert Guest

    "respiration rate sensor" seems to be a slightly better search term,
    although I had no luck finding an example of a pressure based sensor with
    that search term. Some of these place a tube in front of the nose and
    mouth to sense stagnation pressuure (similar to a pitot tube); I think
    that these are the most accurate type available.

    The sensors used in sleep studies often use thermistors (never hot wire),
    which as someone else mentioned have better sensitivity than the hot wire
    type, and much better snot resistance. The main problem with these is
    that you inhale ambient temperature air and exhale body temperature air,
    which provides a much larger thermal signal than the airflow cooling of a
    heated thermistor, so it is difficult to get an accurate flow
    measurement, although they are very good for inhale/exhale timing and
    thus good at detecting apnea. For this purpose a single unheated
    thermistor is adequate.

    I just tried "pressure based breathing rate sensor" as a search term and
    got some interesting results, including:


    More expensive than the (presumably thermistor based) sensor from cooking-
    hacks, and even a plain differential pressure sensor from digi-key is
    over $100, although there are undoubtedly cheaper pressure sensors of
    suitable sensitivity (a few cm H2O) available somewhere.

    I like the idea of hacking your CPAP for a usable signal as a low cost
    alternative, although that does limit your measurements to while you are
    using the machine.

    You might ask the doctor who did your sleep studies for sensor
    You're welcome, and good luck with your project.
    Glen Walpert, Jan 7, 2014
  5. Neon John

    RobertMacy Guest

    I do/try to work in my sleep, though. The trick is to go to sleep with the
    purpose of dreaming about the task to solve, dream of sitting at my bench
    solving the problems, and during the dream actually solve the problem. In
    the morning awake and scramble to keep the memory of the dream long enough
    to record the results. Have solved three major problems that way. One
    circa 1966, was a very tricky square root of average squaring circuit as a
    simple rms detector to control filament drivers for mission radios [the
    more accurate control of the filament power extended the life of the
    radios noticeably], another circa 70's was how to cheaply/effectively get
    12 bits from an 8 bit DAC. and in the 80's 'proper' signal processing for
    image scanning WITH OCR, and so on.
    RobertMacy, Jan 7, 2014
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