Electronics > Projects, Designs, and Technical Stuff
Sprint Day 2: What developing world substitutions are there for flow meters?
<< < (6/12) > >>
tkutscha:
You can get a cheap acrylic air flow meter (<$20) and use a series of optical sensors with an MCU to read it out live.  I initially thought of putting a magnet ball in there and using hall-effect senors, but changing the weight of the ball would probably upset calibration.  Since you're looking for 0-80 LPM, you could put two in series to get accuracy at the low and high ends.

If you have a bunch of them, you could point a cheap camera at all of them to read out the ball heights with image processing software.  Maybe a super cheap webcam and some image filters.  Make the ball luminescent or glow under an UV lamp to make it stand out more?

Looking on Amazon: $16 for a flow meter, $10 for a cheap USB cam, and a raspberry Pi to look at several of them ($35).
Simon:
sounds really fail safe and medical.....
dietert1:
If i remember right, others have been able to measure heart rate of by-passers using video, so video is a powerful tool.

A flow meter i built 15 years ago for respiration measurements in a university institute was based on a difference pressure sensor and an "airflow resistor" that can be made with a 3-D printer and/or some tissue. Those meters i made had an instrumentation amplifier to read the sensor bridge, a CMOS analog multiplexer to provide 4 different steps of gain and a 12 bit ADC in a MSP430 microcontroller.

Recently i thought a lot about whether such a setup may be enough to control respiration support in a ventilator. In the documents circulating right now they propose monitoring pressure, maybe monitoring flow could be as efficient. Yet again those projects are not electronics, but interdisciplinary.

Regards, Dieter
Simon:

--- Quote from: dietert1 on April 06, 2020, 08:52:09 am ---

A flow meter i built 15 years ago for respiration measurements in a university institute was based on a difference pressure sensor and an "airflow resistor" that can be made with a 3-D printer and/or some tissue. Those meters i made had an instrumentation amplifier to read the sensor bridge, a CMOS analog multiplexer to provide 4 different steps of gain and a 12 bit ADC in a MSP430 microcontroller.

Recently i thought a lot about whether such a setup may be enough to control respiration support in a ventilator. In the documents circulating right now they propose monitoring pressure, maybe monitoring flow could be as efficient. Yet again those projects are not electronics, but interdisciplinary.


--- End quote ---

Which is what I suggested above. The main issue is getting the pump to work in sync with patient. If you don't their lungs won't survive being on any of these contraptions for weeks.
dietert1:
Anyway a medical machine needs some redundancy. In fact the proposals include mechanical safety valves and the like.

At that time the respiration project was some kind of reuse. Our pulse oximeter modules include logging an ECG signal - again for redundancy and also to determine PTT, a parameter in sleep diagnostics. In those meters i mentioned the pressure signal replaced the ECG signal, so with very few changes we arrived at a solution combining pulse oximetry with airflow meter. It's a USB device with isolation.

Regards, Dieter
Navigation
Message Index
Next page
Previous page
There was an error while thanking
Thanking...

Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod