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Comment by adammunich | Hacker News Reader

I have been building something very similar to this! We have someone working on the controller PCB right now, and I am waiting for a few parts to arrive Friday so I can finish the proof of concept. Once the bugs are hammered out we will publish the design and build instructions on civilpedia.

I can say for sure, the solenoid valves specified here in this paper are too small to work well enough. This problem has slowed our progress down by a week.

If anyone has questions please ask them here.

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If I run a high-tech manufacturing facility that has some extra capacity these days, whose ventilator design should I start producing? It seems so many are springing up.

Whatever you can get parts for, I suppose.

We chose parts you can get from Home Depot and Amazon/Ebay only, except for the PCB, which you will be able to make with hand-soldered components.

Also: make sure you choose a design where it is not possible to over-pressure the lungs. Even so much as 1.5PSI can damage them permanently. As well, the design must never allow the pressure to drop below about 300 pascals (above STP), or the patient will eventually suffocate due to alveoli collapsing.

300 pascals? That's darn near a vacuum. Did you mean not to let it drop more than 300 Pa below ambient?

It cannot go under STP + 300 pascals, must always be positive pressure.

If anyone's wondering, atmospheric pressure is 101 300Pa, so 300 Pa is extremely low.

Does your design also rely on pressurized medical air for operation?

It sounds like this one is using an ESP32 microcontroller (described as 32 bit, arduino-compatible, WiFi+Bluetooth ). What microcontroller are you using?

Is your design open source?

Can you expand on the solenoid difficulties you experienced?

Thanks!

Edit: typo

It can operate from any air source, we're using a free piston hydroponics compressor which is available from eBay/amazon vendors for $100. I have used these compressors for years with no reliability issues.

We will be using an Arduino uno because they are so easily available, no wifi or bluetooth, last thing I'd want people to deal with is bluetooth bugs in a situation like this...

The solenoids I have tried (many) are too restrictive for air flow, and after some minutes I felt suffocated when using them. Most solenoid valves don't have orfices greater than 2.5mm, and we found even 4mm was not enough.

It will be open source, yes.

Make sure you are using a medical grade (oil and particulate free) compressor, because aerosolized machine oil and micro metals are super bad for people to breathe in.

The free piston compressors don't use oil as far as I have been able to tell. I believe they are diaphragm pumps.

Cheap compressors (even labeled oil free) will still have residue machine oil on internal surfaces from the manufacturing process. Chinese manufacturers usually surface coat metal to prevent rusting during shipping.

It might not be enough to bother you or I, but if someone is respiratory compromised to the point they are on a vent, they really need medical grade oxygen.

OK we can recommend a filter if the compressor is of unknown quality.

I have tested our design with supplemental air from a Phillips EverFlo and it still works well.

That was one of my first reactions reading about this design as well, that WiFi is likely a liability in this case (not to mention espressif's security track record is not the best) despite the potential ease of provisioning. I would prefer either a microcontroller with ethernet or acting as a USB network device. Then it would still be as easy as plugging into the device with a laptop and navigating to a web page to configure the ventilator, although one couldn't easily do it from a smartphone or tablet.

Is a less-complicated (and more easily verified) PCB too difficult to design? Arduino may be easy to use for proto, but not going to be simple to verify. Plus, you are now slave to their supply chain, for a need that may be much simpler than what the Arduino board offers.

The Arduino Uno MCU is fairly widely available: https://octopart.com/search?currency=USD&q=Atmega328p&specs=...

although there are others MCU's with even better availability (e.g. the SAMD21, which also has plenty of dev boards and it seems like Microchip has extensive stock on hand, for example https://www.microchipdirect.com/product/ATSAMD21J17A-MUT?pro... ). One can take any of the devboards a a reference design.

Of course, I read the original comment as relying on the entire Arduino Uno board, which is both expensive and restrictive to your supply chain. Individual components, such as MCUs could more easily be selected to avoid those two issues.

As an aside, your adammunich.com website just displays a "Please click the allow button to show you're not a robot" message. With no Allow button anywhere.

With variations on it (but same problem) with each page load.

Capture fail, or joke website?

Worse, I'm getting a pop-up requesting I allow notifications. No, thank you. It seems that if I don't allow notifications, I can't view the site - and I'll keep getting the pop-up. This is one of the more intrusive and off putting experiences I've had on the first time load of a site.

Edit: After clicking "Block notifications" about 10 times, and being redirected to a different "redfundchicken" address each time, I finally end on skyprize22.live, an obvious scam site.

I believe adammunich.com redirects to a scam site.

Happy to help on EE side. PCB, firmware, verification, etc. https://www.linkedin.com/in/thenatefisher/

I have a bare PCB and PCBA CM that is still running. Let me know if that can help in any way.

We can reprogram our lines to make any type of PCBs and assemble them (we have inventory of most standard components).

Hey you appear to have been shadow banned back in 2017 for no reason I can see. I think you can email the support address to fix it?

Yes, that was a mistake at our end and fixed now.

All: if you see a banned user that shouldn't be banned, please let us know at hn@ycombinator.com. We try not to get this wrong, but we (and/or software) sometimes do. It's a big contribution to your fellow users to let us know so we can fix it.

Awesome work! What is civilpedia?

https://civilpedia.org

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