Help with parts for breathing ventilator design needed


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.

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!

This module should be able to do all you’re looking for.

I checked with Nellcor and approximate cost is $160

You should be aware that the FDA (assuming you’ll want to use it in the USA) will have a lot to say as to whether you’ll ever be able to put a such a device on a person. You’ll have to prove that it is both effective and safe. And look into a sizable liability policy.

First of thanks for the reply.

I’m not going to sell them. The blueprint and code will be open sourced.

I just want to make a product which is easy to assemble and the parts are readily available so any hospital who is in need can use this as an temporary solution instead of having to chose who dies like is now the case in Italy.

If I read it correctly it measures SpO2.
This is not what should be measured.
The ventilator has to deliver a certain volume and pressure of air with a higher concentration of oxygen then normal air.
The heart rate monitor is a side thing just because it’s just a couple of euros extra.

Do you have tips on sensors which do this?


You wrote that you wanted heart rate monitoring and alarms. This module will give you both.

I don’t know anything about the regulations in the EU but I imagine that they are going to require medical-grade components like we do here in the US.

Here is a link to the service manual for a typical ventilator:


You may be able to get some ideas.

So you just woke up this morning and decided you build a breathing ventilator,to help out,but need someone to find you the parts ,I wish you luck getting it done ,enjoy

Thanks, I’ll look into it.

Pretty much yeah. But I’ve build several businesses over the years and it wouldn’t be the first time we’ve created solutions in days where enterprises took more then 6 months.
But anyway thanks a lot for taking time to look into it.

Good luck ,I hope you do get some made,they sure are needed

What about firmware? That’s where most of the magic is.

Check in with these people. They may be able to advise you.

To keep the firmware simple I choose a Raspberry Pi, with this all the algo’s can be build in Python and maybe some sensors can just be done with a Pihat, other sensors might need an Arduino uno in between. Although I haven’t done that before I’ve looked into some tutorials and it seems they really nailed it so it’s pretty simple to code. However I also have C experience if it’s needed (Really hope it isn’t needed though haha).

Thanks for the links, will contact them. I also found this site
which has a lot of information which helped me. I believe it had some info about the margins for the sensors in order for it to be certified.

Will update when I know more.

I sincerely wish you luck but I also hope you will understand the obstacles you’re going to have to overcome to get this as a viable device. I was a Biomedical Equipment Tech for 35+ years and serviced ventilators as part of my job. Your design is basically an automatic Ambu-Bag.