On a sunny day (Mon, 06 Jan 2014 10:41:56 -0500) it happened Neon John wrote in :
Thermoouples can be easily made and are extremely fast:
I guess the breathed out air is usually warmer than the environment, You could try a small thermocouple. LM35 would be slow compared to that,
There is also:
And Doppler..... I have posted about that here too.
ARRRGGG!!! our radiation expert! Sorry to hear about lung. QUESTION: does your collapsed lung pose a pneumonia threat? With treatment like no drinking, antibiotics. that kind of thing?
Anyway all ideas sound great.
A few years ago, as part of a portable patient monitoring system; I designed a volumetric sensor for measuring expiration.
The principle was based upon the variation of magnetic field strength vs distance. Using four coils, two transmit and two receive, with eeach coil transmitting its own, unique tone; it was possible to make four distance measurements and fairly accurately calculate lung volume. Very battery friendly because the 3.3 volt battery only needed to supply a total of 10 mA for the whole sensor system. The sensors could measure anywhere from 6 inches to over 27 inches. Accuracy? At a distance of 8 inches, I measured
1 mil rms. Yes, that's 1/1000 of an inch of rms noise.The coils were constructed of 100 turns on a 6 layer 1/32 inch PCB about 1
1/2 to 2 inch round, so the 'coils' easily fit into a wearable fabric 'jacket' and being so flat, the patient could easily sleep on the coils without noticing, well not noticing too much.The client was ecstatic when they saw the 'clean' waveforms of breathing - they were used to seeing very ratty looking waveforms.
Why the detail? if that piece of electronics you plan on using has something like a soundcard in it with two channels out and two channels in you can easily make the whole sensor system yourself.
If you can break the glass without breaking the filament, a small low voltage lamp makes a good quick-responding anemometer. Put it in one limb a Wheatstone Bridge circuit which passes enough current to heat it, then monitor the changes in off-balance voltage as the filament is cooled by the air currents.
...on the other hand, you may not feel like stuffing a broken light bulb up your nose....
-- ~ Adrian Tuddenham ~ (Remove the ".invalid"s and add ".co.uk" to reply) www.poppyrecords.co.uk
Change doctors ?>:-} ...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
Bummer. Get well please. We need more radiation experts.
I agree with the others that a hot wire anemometer would probably be worth trying. Unlike a turbine or pressure vane, a hot wire anemometer has the advantage of not blocking the air flow. I've built them for weather stations and they work well at very low velocities. However, there's a potential problem. Human breath is about 100% relative humidity. A hot wire will spend much of its energy evaporating the water producing potential accuracy problems. I found a few overpriced papers on the effects of humidity on hot wire anemometer measurements, but nothing for free, yet. The first has an extract that's worth skimming:
Another possibility is an ultrasonic flow meter. There are several different types. I have no clue (yet) as to which one is most appropriate. Again, the air flow is not blocked by the sensors.
I would be tempted to suggest a Pitot tube: which measures a pressure difference to compute the air flow. I have no clue how well it works at low air flows, whether it can be kept clean in a moist environment, or whether it can be made mechanically survivable. I suggest you save this one for the last resort.
Have the body mechanics suggested implanting a chest tube to bleed off the excess air formed around the lung? That's only for severe cases and 6 weeks is probably too little time to give the CPAP machine enough time to work. Also note that there's some anecdotal evidence that the CPAP machine might cause a collapsed lung: I suggest a few questions on the above forum might be useful.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
Oops. I won't get a reading comprehension award for the above. I misread the thread. (I'm fighting a cold or flu and the brain is temporarily out of gear.) The OP complained of chest pains and suggested that it might be a collapsed lung caused by the CPAP machine. Nobody agreed, although there was mention that pain during the first few weeks was common. Sorry for the muddle.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
Is there any information you can glean from the CPAP machine itself?
They dumb down the interface and try to lock the functionality up, but you may be able to find software that will allow access to the data.
For a "hot wire" anemometer you could try self-heating a smaller transistor than a TO-92, for example an SC-70. Not too hard attaching wires to something that size if you have good eyes or a microscope. King's law equation.. and there is some IFD stuff IIRC.
Best regards,
--sp
Article on hot wire anemometers: Various probes: Wire probes are for gases, film probes are for liquids. They claim
100 KHz frequency response, but that's at 30 meters/sec, which is somewhat faster the human breath. With that high frequency response, you should be able to get a clean waveform.-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
Tungsten wire is available on eBay: Looks like you can obtain some really small diameter wire for cheap. Besides anemometers and hight temp thermometers, tungsten wire is also used for the cross hairs on rifle scopes and surveying equipment. However, at 0.0045 ohms/C tempco, you'll need some serious gain to see any changes produced by low velocity air movement. You might also need a tiny spot welder to attach the tungsten wire.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
Is there anyway they could make a pacemaker like device that would stimulate the diaphragm?
Are there many cases like yours that would even make this worth designing such a device? Or is this more like an orphan medical condition?
Sure hope you can find some relief for it.
Regards
The difficulty is getting response at the junction but not conducting the heat down the connecting wire. I've used the broken bulb technique, but it's likely go get covered with gunk when you stuff it up your nose.
It can't be all that hard to buy a REAL thermocouple. I have a commercial HVAC hot wire anemometer. Has two thermocouples in the head. The big one is about the size of a baby gnat. The small one is somewhat bigger than a grain of salt.
from the op Second thought is a self-heated thermistor bead. Major problem is the signal would have to be linearized which would take a little more software effort than I want to dedicate to this project.
Linearization of the data is likely the easiest part of this project. And how linear does it need to be if you're looking for relative measurements?
Q: Why don't you do ? A: Because this is something I want to knock out over a weekend using available materials.
You have a condition that's having a MAJOR negative impact on your life and you can't be bothered to spend more than a weekend to address it?
There are a lot of smart people here willing to collaborate. Use 'em and git-er-done.
There used to be tiny glass coated thermistor probes for this sort of thing. STC R25 rings a bell. Very fast response, much greater resistance change than heated wire types, and the fact that its a bead means the sensor is localised to a small area.
LTC had a neat trick for linearising. Electrically heat the bead to keep the temperature constant, that gets around all the thermistor linearity effects. Then measure the power input, which is directly proportional to a function ( something like the cube, I think ) of the airflow. Its trivial to measure the voltage and current with a couple of ADC channels. From that, you can compute the resistance and power directly. Use PWM from the micro to control the drive current.
-- Regards, Adrian Jansen adrianjansen at internode dot on dot net Note reply address is invalid, convert address above to machine form.
I'd think you'll also need to measure the temperature of the air
afair the MAFs used on many cars have shielded termistor and a hot wire in the flow and keep a constant temperature difference
and remember that is doesn't take direction into account and the it measures mass flow, not volume
-Lasse
You could just buy one, for example: from:
There are a wide variety of breathing sensors on the market. Sleep studies typically measure airflow separately at nose and mouth, plus a chest strap "breathing effort" sensor or two.
Darn good idea, so I searched. Yes, they make "diaphragm stimulators" and "diaphragm pacemakers." Unfortunately I only saw units for totally paralyzed people that bang your whole diaphragm with an external rhythm, nothing that used the existing, natural impulses for timing.
Sounds like all John really needs is a bit of golden jumper wire, either the jump the damage, or to tie the two sides together.
No idea if it's that simple--he might also need a buffer amp. for the one side to drive the other...
Yessir, that's for sure.
James Arthur
Spirometer? I like the name.
Eg.
--sp
"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 recommendations.
You're welcome, and good luck with your project. Glen
t
6 d 1
- n
Was this a respiratory magnetometer? I have been trying to figure out how t o build one for well over a year. I am a student in a field where we study respiratory function and dysfunction. There use to be a company (I think it was just one individual) that made the magnetometers but they stopped many years ago. Today we use other methods but I have always been extremely fas cinated with magnetometers (although I have never used one myself) and I th ink in some cases they would work better than our current systems. I have s een them pop up in research papers from time to time but they are not used very much anymore because of the lack of supply. I don't think anything I build would be use in our program but I really would like to build one to u se on myself and learn more about them. Most of the schematics I have found are very old and use equipment that is not as widely available anymore. Th ese plans also usually leave out one or two critical details. Would you be willing to share any more information about how your system worked or more information on the coils (wire gauge)? Any information would be very great ly appreciated. Thanks!
t
6 d 1
- n
Was this a respiratory magnetometer? I have been trying to figure out how t o build one for well over a year. I am a student in a field where we study respiratory function and dysfunction. There use to be a company (I think it was just one individual) that made the magnetometers but they stopped many years ago. Today we use other methods but I have always been extremely fas cinated with magnetometers (although I have never used one myself) and I th ink in some cases they would work better than our current systems. I have s een them pop up in research papers from time to time but they are not used very much anymore because of the lack of supply. I don't think anything I build would be use in our program but I really would like to build one to u se on myself and learn more about them. Most of the schematics I have found are very old and use equipment that is not as widely available anymore. Th ese plans also usually leave out one or two critical details. Would you be willing to share any more information about how your system worked or more information on the coils? Any information would be very greatly appreciated . Thanks!!
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.