Help with parts for breathing ventilator design needed

@dicecko wrote:

Hi,

I’m new to this so please forgive for anything trivial.

I’ve made a design for a ventilator which hospitals could use in case they run out because of the Corona-virus.

To keep costs down I’ve used a SBC (probably a Raspberry Pi) to act as controller for the parts.
However I’ve only used a RP 3B+ and an Orange Pi Zero as servers and didn’t connect any sensors to it.
So I’m hoping someone here could help me, so I can continue quickly and don’t have to research everything myself, since time is of the essence.

I’ve simplified the design to the basic parts which connect to the SBC.

air system1663×700 21.3 KB

The flow works like this:

• The Nema 17 stepper motor pushes a syringe or air pump back and forth to move the air.

• We begin by settings the valves so we can suck in oxygen by pulling the plunger of the syringe back.

• Next we switch the bottom valve so we suck air instead of oxygen and do this till we have the correct mixture.

• Then we switch the top valve and push the plunger forward so we push the air into the patient.

• Just before the patient we have a chamber with a pressure sensor (barometer) and an oxygen sensor to keep control over the pressure in the lungs and how much oxygen is going in and out.

Then we have 2 alarms and a heart rate sensor for monitoring the patient and system.

• We have a heart rate sensor to monitor the heart rate.

• The first alarms beeps at the heart rate and has to give a loud alarm at a system failure

• The second alarm has a backup battery and only turns on when there is a power failure and the system completely shuts down.

So please help me with:

1. Which sensors are good quality and are accurate (say within 1% pressure and oxygen), the best option would be to be able to use them directly on the SBC without using a Arduino Uno in between.
2. What heart rate monitor is easy to use.
3. What alarms to use.
4. For the Nema 17 I read that I need a separate A4988 stepper motor controller. Is this the best and easiest choice?

This already would help me tremendously! However any extra information on how to do the actual implementation would be welcome.

Thanks in advance!

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