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Maintaining constant pressure inside a volume

okaythanksbud

Sep 26, 2023
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Sep 26, 2023
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I want to create something that would basically function like a CPAP machine, so it seems like the main question to ask is how id maintain a constant pressure inside a volume. Unfortunately it seems like documentation/videos regarding pneumatic circuits/components used in such circuits is next to non existent but what I understand so far is I will need:

something to increase pressure in the volume (air pump)
something to decrease pressure in the volume (solenoidal valve? maybe another air pump?)
something to measure pressure in the volume (pressure sensor)
some microcontroller

Ideally id like this to function at 4mmH2O-40mmH2O, and it would be nice if it could operate with a <=12V supply

So far I've found these:
Pump:
https://www.amazon.com/Air-Pump-Ele...t=&hvlocphy=9022885&hvtargid=pla-694734263031

Valve:???

Pressure sensor:
https://www.digikey.com/en/products...nfsNkhOrJZ1gKQAXUIAHAC5QQAZX0AnAJYA7AOYgAvo6A (seems like most of these would suffice)


My worry is that the pump I use will not be able to keep up with inhalations or exhalations--I need whatever components I use to be able to produce a decent flow rate to move air around fast enough to: repressurize moderately quickly upon inhalation, and depressurize quick enough upon exhalation. Ive never made anything that automates air flow so Im unsure if this would be feasible, especially given the low pressure requirements. I am unsure how powerful these components tend to be so I am unsure if what I want is feasible. I figured I'd ask people who have more experience what they think, if this would be a feasible project and maybe anything else that would be important to consider.

Thanks for any help.
 

kellys_eye

Jun 25, 2010
6,514
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Jun 25, 2010
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6,514
fast enough to: repressurize moderately quickly upon inhalation, and depressurize quick enough upon exhalation. Ive never made anything that automates air flow so Im unsure if this would be feasible
It's called an air compressor (with receiver i.e. storage).

The pump runs whenever it's required to in order to keep the air storage tank full and you regulate the discharge using a pressure regulator/valve. Sensors at the input/output of whatever it is you're feeding the air supply to will be able to maintain a steady flow 'through' it.
 

danadak

Feb 19, 2021
783
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Feb 19, 2021
Messages
783
Not unusual these days to use dual core processors in medical equipment,
to improve safety for patients. And take advantage of the SOC offerings,
example of whats onboard chip, in many cases multiples of whats shown :

1695814112898.png


Regards, Dana.
 

Alec_t

Jul 7, 2015
3,596
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Jul 7, 2015
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3,596
Even at 40mm H2O pressure, the pressure transducers in the link would be operating at only ~10% of their full-scale range (if my maths is correct). I wonder how linear they are and what their accuracy would be at 4mm pressure? How accurately do you realistically need the 'constant' pressure to be?
 
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