Experiments on a $50 DIY air purifier that takes 30s to assemble • Hacker News Board

Re: Experiments on a $50 DIY air purifier that takes 30s to assemble

#31

Post by hajimemash » Thu, Dec 17, 2020, 10:28 AM UTC

xnyan wrote: post #12

Havoc wrote: post #10

Earlier quoted context omitted.

Not really. To remove smells ozone generators are used. That stuff is really dangerous though

This is not correct. Activated carbon is very effective and in wide use for odor removal.

This is correct, but this is incorrect.

Re: Experiments on a $50 DIY air purifier that takes 30s to assemble

#32

Post by infofarmer » Thu, Dec 17, 2020, 10:33 AM UTC

Smart Air is a whole company built around a super cheap HEPA-on-a-fan, started by foreigners in China. They still sell their old DIY1.1 model for $35 shipped (in Mainland). I own and love their filters, although I miss the «smart» features of their competitors.

https://smartairfilters.com/en/about/our-story/

Re: Experiments on a $50 DIY air purifier that takes 30s to assemble

#33

Post by shared_frog » Thu, Dec 17, 2020, 10:46 AM UTC

ahaucnx wrote: post #21

We have open source, open hardware build instructions for a very reliable Air quality sensor that can be used to measure PM2.5 and also CO2. https://www.airgradient.com/diy/ We have tested it extensively and it is very accurate for the fraction of the costs of commercial sensors. You can build it for less than USD 20 and send the data to our cloud server or any other backend. We also measure CO2 because if you have p…

I appreciate your DIY instructions, but I really dislike how your website goes through the effort of hiding what you actually sell and also how much it costs. I don't want to "contact you" to get that information. We've been long enough in the 21st century that it has become an adult, and still I keep running into this archaic nonsense.

For example, you mention your "sensor package" in the FAQ and that's it. Your DIY instructions mention the "AirGradient PCB", _but there is no place where I can buy it_. For the love of god, put a 'buy' button on your website.

Re: Experiments on a $50 DIY air purifier that takes 30s to assemble

#34

Post by jsingleton » Thu, Dec 17, 2020, 10:47 AM UTC

ahaucnx wrote: post #21

We have open source, open hardware build instructions for a very reliable Air quality sensor that can be used to measure PM2.5 and also CO2. https://www.airgradient.com/diy/ We have tested it extensively and it is very accurate for the fraction of the costs of commercial sensors. You can build it for less than USD 20 and send the data to our cloud server or any other backend. We also measure CO2 because if you have p…

It looks like you're using a Plantower PMS5003. I have one of those hooked up to a Raspberry Pi and it works well but I also built a few of these with ESPs: https://sensor.community/en/sensors/airrohr/

They support the PMS but I used the default SDS011. They both seem reasonable for relative values but I'm not sure about the accuracy without proper calibration. They don't appear to give similar readings to my Plume Flow 2: https://plumelabs.com/en/flow/

Re: Experiments on a $50 DIY air purifier that takes 30s to assemble

#35

Post by jsingleton » Thu, Dec 17, 2020, 10:50 AM UTC

There is some interesting info on building a cheap ~$20 purifier here: https://airpollutionguide.net/

I haven't tried as cheap HEPA filters appear to be harder to get hold of in the UK. Maybe due to different heating systems.

Clearing the Air: The Beginning and the End of Air Pollution by Tim Smedley is an excellent book if you are interested in this area.

Re: Experiments on a $50 DIY air purifier that takes 30s to assemble

#36

Post by Semaphor » Thu, Dec 17, 2020, 11:03 AM UTC

shared_frog wrote: post #33

ahaucnx wrote: post #21

We have open source, open hardware build instructions for a very reliable Air quality sensor that can be used to measure PM2.5 and also CO2. https://www.airgradient.com/diy/ We have tested it extensively and it is very accurate for the fraction of the costs of commercial sensors. You can build it for less than USD 20 and send the data to our cloud server or any other backend. We also measure CO2 because if you have p…

I appreciate your DIY instructions, but I really dislike how your website goes through the effort of hiding what you actually sell and also how much it costs. I don't want to "contact you" to get that information. We've been long enough in the 21st century that it has become an adult, and still I keep running into this archaic nonsense. For example, you mention your "sensor package" in the FAQ and that's it. Your DIY…

The PCB is not sold by them, they have the Gerber files for download, and you can upload them here [0] to have it made and shipped to you.

It seems what they are selling are consulting services with possible parts depending on the results, if you don’t want to do everything yourself.

[0]: https://jlcpcb.com

Re: Experiments on a $50 DIY air purifier that takes 30s to assemble

#37

Post by heavyset_go » Thu, Dec 17, 2020, 11:04 AM UTC

artvark11 wrote: post #3

Are diy filters effective at removing smells or only removing the measurable particles?

I lit a candle in a room where I had one running, and the filter darkened pretty quickly. It seemed to have caught some of the smoke particles, which can be pretty small at under a micron.

Re: Experiments on a $50 DIY air purifier that takes 30s to assemble

#38

Post by xwdv » Thu, Dec 17, 2020, 11:06 AM UTC

shared_frog wrote: post #33

ahaucnx wrote: post #21

We have open source, open hardware build instructions for a very reliable Air quality sensor that can be used to measure PM2.5 and also CO2. https://www.airgradient.com/diy/ We have tested it extensively and it is very accurate for the fraction of the costs of commercial sensors. You can build it for less than USD 20 and send the data to our cloud server or any other backend. We also measure CO2 because if you have p…

I appreciate your DIY instructions, but I really dislike how your website goes through the effort of hiding what you actually sell and also how much it costs. I don't want to "contact you" to get that information. We've been long enough in the 21st century that it has become an adult, and still I keep running into this archaic nonsense. For example, you mention your "sensor package" in the FAQ and that's it. Your DIY…

They want to change what they charge from time to time so putting a price up front will force them to leave money on the table. Not gonna happen. Contact them instead.

Re: Experiments on a $50 DIY air purifier that takes 30s to assemble

#39

Post by mkskm » Thu, Dec 17, 2020, 11:07 AM UTC

jansan wrote: post #22

This is certainly done with COVID-19 in mind. Is there any source that shows how effective HEPA filters are for filtering SARS-CoV-2, given that its average size is just 130nm, which is twenty times smaller than PM2.5.

The respiratory aerosols containing viruses such as COVID are typically ~3 um. See section 10.4 on this page:

https://tinyurl.com/FAQ-aerosols

Re: Experiments on a $50 DIY air purifier that takes 30s to assemble

#40

Post by archi42 » Thu, Dec 17, 2020, 11:12 AM UTC

WalterBright wrote: post #16

Another way to do it is to bubble the air through water. As a kid, we did an experiment where a cigarette was "smoked" by attaching a tube to the cigarette filter, the tube exited at the bottom of a flask filled with water, and a pump would suck the air from the top of the flask. It didn't take long before the water would turn black. Quite a turnoff for wannabee smokers, which was the obvious point of the experiment.…

That's essentially a Shisha you built there, so smoking that way is a thing ;) The tobacco is different, as is the heat source, but I can confirm that the water still turns rather unpleasant.