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

dyno-might.github.io

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

#131

Post by bluGill »

totetsu wrote: post #52

water filters also have the incompatible proprietary filters problem. I wanted to try filtering some water so I could make coffee that wasn't bitter but every water filter seemed to want me to buy a bunch of plastic to go around a replaceable filter. In the end I settled on pyrolysized cherry wood branches, (activated carbon, or biochar). It seems them carbonated bamboo is also used in tea making. It worked but it ce…

There are standard sizes and housings for water filters. No fridge uses anything standard, but you can find them. you need some sort of plastic (or at least something food safe) around the filter though.

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

#132

Post by EricE »

azmodeus wrote: post #23
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 would be nice if preassembled kits could be purchased from you. I would be happy to pay USD 40 for a good preassembled kit.

Way too low for that - good rule of thumb is 1.5x to 2.5x the cost of materials for labor if someone else is going to do it for you.

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

#133

Post by EricE »

yborg wrote: post #119
chopin wrote: post #19

What I am wondering about: I worked with and designed clean room equipment in the nineties. I remember that HEPA requires a considerable pressure difference which cannot be delivered by an axial fan. You'd need a radial one which can deliver a considerable differential pressure, at cost of throughput (where the axial fan shine). If you strap a HEPA to an axial fan and seal it, the fan runs effectively "empty", i.e. i…

>If you strap a HEPA to an axial fan and seal it, the fan runs effectively "empty", i.e. it displaces only little air which most likely even doesn't pass the filter This. I tried a 3M MERV 12 filter taped to the intake of a cheap $12 box fan and the airflow through the fan went to effectively zero. The fan actually was pulling more air from the front of the fan around the sides of the fanbox than through the filter.…

Radial fans are a lot quieter for the volume of air delivered too.

Wish I could find a room humidifier with a radial fan but all I can find are axial fan designs :p

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

#134

Post by EricE »

neilv wrote: post #102

When I made one of these with a cheap box fan and a good 3M filter that covered one face completely, I ran into the airflow problem. For reasons (cheap fan with the cable and switch going in the center of the rear), I had to have the filter on the outflow side of the fan, and I was getting much more airflow back out the corners of inflow side of the fan than through the filter. I'm frugally-inclined, but I was desper…

Just cut down a furnace filter to fit inside. I’ve been doing that for years with a few Sharp units I can’t get filters for any more (discontinued) and some newer Levoits. If you leave them running all the time on low they are more effective than running them part of the day with the “official” filters.

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

#135

Post by westurner »

ruste wrote: post #117
westurner wrote: post #54

From "Better Box Fan Air Purifier" https://tombuildsstuff.blogspot.com/2013/06/better-box-fan-a... : > Air purifiers can be expensive and you've probably seen articles recommending to just put a 20" x 20" x 1" furnace filter on a cheap 20" box fan and POOF! instant cleaner air for not a lot of money. It really does clean the air pretty cheap. > There's a problem with this though. These fans weren't designed to be run…

> There's a problem with this though. These fans weren't designed to be run with a filter. The filter will restrict air flow which will put a higher strain on the motor causing it to use more electricity and in worse cases could be a fire hazard. The higher the MERV rating (cleaning efficiency) of the filter the more stress it will put on the fan. I'm fairly certain the opposite is true. In fact, most rowing machines…

A. Putting two [larger] filters in a 'V' with cardboard to fill the top and bottom pulls the same amount of air through a larger area of filters

B. pulling the same volume of air through greater surface area results in greater pressure between the filter and fan than one filter directly affixed to the fan

C. The lower air pressure / "suction" due to an obstructed intake causes an electric fan motor to fail more quickly.

D. Increasing the air pressure that the motor is in reduces the failure rate?

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

#136

Post by EricE »

ionwake wrote: post #106

I don't mean to go against the spirit of the thread but does anyone know how these DIY compare to actual commercial products - and can anyone recommend a good air purifier? Thank you ( I will remove this comment if it is offtopic )

Radial fans (also known as squirrel cage blower, or visualize a water wheel from an old fashioned water driven flour mill) will move air more quietly than an axial fan in a box fan. Levoit on Amazon are some great, relatively inexpensive units and when the HEPA filter it comes with needs replacing I use use furnace filters cut down to size. If you want it to last a bit longer, you can use quilt batting as a pre-filter before the furnace filter to catch the big stuff and extend the life of the furnace filter.

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

#137

Post by quercusa »

xwdv wrote: post #38
shared_frog wrote: post #33

Earlier quoted context omitted.

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.

When you can get quotes for satellite launches[0] without calling anybody, it feels like unnecessary friction at best.

[0] https://www.spacex.com/rideshare/

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

#138

Post by lurkertech »

The OP design might see a big jump in effectiveness if they add an air guide one one or both sides of the box fan (just make a simple square cardboard tube with some tape) so that by the time the air reaches the filter, it has laminar flow. This helped enormously in a DIY design I kludged together in Thailand (where box fans are NOT available, so I had to get something to work with regular round desk fans, which everyone already has):

https://slice-of-thai.com/air/

"cannon" design (ugly but effective): https://slice-of-thai.com/air/#p3

This may also explain why the OP heard that the tape "helps" but was surprised when it didn't. The key issue is likely not sealing with tape but rather forming an air guide.

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

#139

Post by headmelted »

joshmlewis wrote: post #105
headmelted wrote: post #26

Earlier quoted context omitted.

This. I no longer have access to a soldering iron and want a bunch of these, not enough that it's worth the cost of buying equipment and the time spent making them. Help us give you money! :-)

You can get good soldering irons for less than $100.

Yeah but I have to buy the soldering iron then spend my time figuring the kit out and doing the job.

I’d be happy to pay OP for their work and everyone wins.

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

#140

Post by neilv »

EricE wrote: post #134
neilv wrote: post #102

When I made one of these with a cheap box fan and a good 3M filter that covered one face completely, I ran into the airflow problem. For reasons (cheap fan with the cable and switch going in the center of the rear), I had to have the filter on the outflow side of the fan, and I was getting much more airflow back out the corners of inflow side of the fan than through the filter. I'm frugally-inclined, but I was desper…

Just cut down a furnace filter to fit inside. I’ve been doing that for years with a few Sharp units I can’t get filters for any more (discontinued) and some newer Levoits. If you leave them running all the time on low they are more effective than running them part of the day with the “official” filters.

Good idea -- that would work for my larger Levoit unit, which takes a pair of flat rectangular filters, though not for the smaller cylindrical unit.

For now, I'm going to try to keep buying the Levoit filters, since I think they have more "layers" than the furnace filters, and I don't have a good sense of what all I should to be filtering in this location. But it's good to have a backup plan.

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