RE: COVID-19 Printable PAPR (Powered Air Purifying Respirator)
RE: COVID-19 Printable PAPR (Powered Air Purifying Respirator)
@guy-k2
Have you considered using something like an up voltage converter to take a 5 Volt USB battery source and turn it into 12 Volts. The benefit would be you can use a standard backup smartphone battery pack which a lot of people already have. Is there a reason not to do this?
RE: COVID-19 Printable PAPR (Powered Air Purifying Respirator)
Hi Guy, I have been trying to send you a private message since signing up on the forum a number of weeks ago, but for whatever reason it seems to be denying me access to write a message. So a public one will have to suffice. I saw you write somewhere that you have a limited development budget. I for one would like to assist. I originally had plans to do some development myself, but everything happens so slowly here (I'm located in New Zealand) compared to what you are achieving. My Digikey order for fans and parts took two weeks for delivery, and the Prusa printer I wanted to buy is out of stock locally, and I'm now I'm waiting on a back order... You're doing a lot of what I was hoping to do anyway, so is there a way I can send you some funds instead? You're doing great work!
Getting lithium ion battery packs into New Zealand is slow and painful, so I did build a 5V to 12V boost circuit in order to be able to run the fan from a ubiquitous USB power bank which are available here. Then I saw that this seems to be a fairly common and available off the shelf - USB connector on one end and 2.1mm DC jack on the other!
Here in New Zealand the spread of the virus appears (at this point) to be well under control, and I don't even know anyone with COVID-19. This gives a surreal feeling, when one knows that elsewhere on the planet things are in contrast pretty dire. Let me know what you need. Maybe others will offer support too as you are the man! 👍
RE: COVID-19 Printable PAPR (Powered Air Purifying Respirator)
Thanks. Thatt is a reasonable price for a boost convertor. I just ordered a pack to try.
Meanwhile, some in the bunnyscience discord are trying to find a 5 volt fan and filter combination that will give sufficient flow. They really want to go with 5 volt power and fan to decrease cost/PAPR. That goal has been elusive due to the 5 volt fans having such a low ability to work against flow resistance. We need to get 20 to 30 L/min flow against about 2.5 cm H2O resistance. They may find a combo yet.
Meanwhile 12 volt fans with sufficient power and plentiful but 12 volt battery packs are less so. USB power packs with 5 volt output and step up should work, if they provide the 2 to 3 watts required.
RE: COVID-19 Printable PAPR (Powered Air Purifying Respirator)
@guy-k2
Have you considered using something like an up voltage converter to take a 5 Volt USB battery source and turn it into 12 Volts. The benefit would be you can use a standard backup smartphone battery pack which a lot of people already have. Is there a reason not to do this?
I know you replied to Guy, but as I had the same idea as you I thought I would reply. Yes, using a USB power bank and a boost converter works. It's even possible to buy something off the shelf. Something like https://www.jaycar.co.nz/universal-usb-12v-step-up-power-cable/p/PP1978
The nice part is that no change is required to the respirator - just swap out the 12V battery pack and use the power bank and boost converter in its place, with the same style DC jack. As a bonus, many USB power banks give an indication of state of charge, so you can get an idea of how much run-time you have left. Plus these power banks seem to be very common (bonus!).
RE: COVID-19 Printable PAPR (Powered Air Purifying Respirator)
@MartinV thanks for the offer of support. I can still absorb what I'm spending, but it is very much appreciated. Maybe I should set up a mechanism for support, but that hasn't been top of my priorities.
This isn't going to be the last time we see this or other viral emergencies. Even as it ebbs in some places, there is risk of reemergence so long as we lack immunity. Getting a lower cost PAPR available is still going to be useful.
RE: COVID-19 Printable PAPR (Powered Air Purifying Respirator)
Looks like just over a week for those booster to arrive. Reading through the reviews makes me a bit leery of them blowing. Last thing I want is the booster to fail during actual use. The failures might simply be the users pulling too much power or not adjusting them correctly. They seem to blow if input voltage is not at least 2 volts lower than output setting.
RE: COVID-19 Printable PAPR (Powered Air Purifying Respirator)
@guy-k2
Going by the pictures, those boost circuits have the absolute bare minimum number of components necessary in order to produce a switch-mode boost converter with adjustable output voltage. For example there is no input protection (what if the supply is connected back to front?), nor is there filtering to address electromagnetic interference. While I haven't tried this particular boost circuit I have tried other similar (cheap, simple) buck/boost converters and they do tend to be optimistic in their performance claims. On the other hand it only needs to provide a couple of hundred mA so I'd hope it could do that. Definitely down the cheap and nasty end though IMO. Compare this to the prototype boost converter I built the other day based on a modular DC-DC converter, Digikey part 1470-4807-ND. That single part alone (which is rated for medical use) costs more than ten times what one of those boards from Amazon cost. It's a tough call to decide what is "good enough" for an emergency respirator, but I'd say if you have any doubts about trusting the boost converter then it's worth going for a higher spec model. I think the idea and technology is sound - just the choice of implementation needs investigation.
RE: COVID-19 Printable PAPR (Powered Air Purifying Respirator)
Reliability is a factor. The Bunny PAPR is a life protective piece of equipment. Having the power system being prone to failure would be a potential disaster. None the less, I'll test out those units and see how they are like.
5 volt USB battery packs are easier to find and cheaper. I can see their appeal for cost control.
Personally, I'm happier and a lot more confident knowing my 12 volt battery pack does not have additional parts to fail.
RE: COVID-19 Printable PAPR (Powered Air Purifying Respirator)
For linking and search convenience, new links
www.bunnypapr.com
www.bunnyscience.com
Should be a bit easier to pass along.
RE: COVID-19 Printable PAPR (Powered Air Purifying Respirator)
Testing an elliptical based flutter valve piece. If elliptical mount pre-flattens the glove finger sufficiently, this could eliminate need for valve deflector.
RE: COVID-19 Printable PAPR (Powered Air Purifying Respirator)
Unfortunately, both of my Prusas are busy with production run prints. I have to wait for one to finish before I can test prototypes.
This is the problem with doing both prototyping and production prints. Production runs grind prototyping to a halt.
Bunnies must be patient, but their ears are twitching.
Updated files on PrusaPrinters and Thingiverse for new flutter valves and fan mounts
Updated files on PrusaPrinters and Thingiverse for new flutter valves and fan mounts
Fan mounting bands B5 revamped to better distribute mechanical stresses.
Flutter valve B5 changed to elliptical base shape and no longer needs deflector piece. Align flat of glove finger with long axis of valve's ellipse for proper operation.
You can see how the glove fingers now flop over without need for a deflector
Added Fan Director
Added optional fan director that mounts between fan and fan flange. Directs fan airflow downward to improve CO2 clearance.
RE: COVID-19 Printable PAPR (Powered Air Purifying Respirator)
Debating whether the fan deflector should be considered optional. Whereas the PAPR has functioned well without it, the deflector made a very noticeable change in how many flights of stairs I can climb comfortably. Without it, I can do two flights and feel a slight increase in respiratory drive due to CO2 increase. With the fan deflector, I can do multiple flights. That little change in airflow pattern clears out CO2 from bag's breathing zone more efficiently.
Maybe it should be standard part instead of optional.
Pivoting Fan Mount Loop
If anyone wants to play along with a pivoting version of the loop, here is a prelim STL. Pull the locking lever of pivot outward to release lock. Fan mount will then pivot BACK towards rear of loop by about 90 degrees. Depending on your printer's tolerances, you may need to gently break pivot free with first rotation attempt. Do so before attaching fan mount. Still deciding whether flatter stowage is worth the added complexity.
RE: COVID-19 Printable PAPR (Powered Air Purifying Respirator)
Transparent Bags
The McGyver Improvised PPE Team found an alternative, clear bag that does not need an optical window added. It is made of OPP and is even more clear than the windows I have been adding.
These https://www.clearbags.com/18-x-24-round-bottom-basket-bag-100-pieces-rb1824.html
Pivoted Loop
Pivoted loop is now in STL files as loop pivoted slope 46 b6
Pull release lever outward to let fan mount pivot BACK towards expiratory ports. Pivoting should rarely be needed during normal usage, but allows for more compact stowage and shipping.
Does NOT pivot forward.
RE: COVID-19 Printable PAPR (Powered Air Purifying Respirator)
Transparency of clearbags.com OPP bag is really nice. Super convenient not needing to add view window. Only downside is requiring a blade to fenestrate openings in bag, but I've been using a blade on the polyethylene bags to get a full opening anyways.
