Hacker News Reader

Comment by adammunich | Hacker News Reader

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.

View on HN

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.

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.

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.

Reply on news.ycombinator.com