Wayne Westerman, PhD Profile picture
STEM Dad, Dancer, Inventor, Farm Boy, Fence Builder, Wind Surfer

Oct 3, 2022, 19 tweets

Here’s another sweet spot for DIY Air Purifiers: super quiet 40dB kid magnet, sweet hum note, pulsing nighttime glow, ~ 200 CADR airflow matching medium HEPAs, just 25 Watts and ~$120 in parts. #CorsiRosenthalBox #WomenInSTEM #COVIDisAirborne

Kudos @CRBoxKits, @robwiss, @Mw_ottawa for pioneering PC fan #CorsiRosenthalBox builds. @kprather, @JimRosenthal4, @CorsIAQ maybe your freshman engineering class can formally characterize the airflow? Can also stand upright with 10 fans (5 each tall side) for 400-500 CADR?

Once 5-fan top assembled, kids can build the filter box with double-sided carpet tape easier than duct-taped CR box fan w/shroud. For now I use foam board for the top plate which is fun for kids to punch, though a precision mill/drill plastic top plate would assemble faster

Compare to Winix 5500-2 $160 that's rated as a best value HEPA. First 4 levels are quiet then level 5 whines up like a meat grinder to 55dB for 230CADR. Our teachers have them but I never see them on level 5 so not moving much in an 800 sq ft classroom winixamerica.com/product/5500-2/

Five 120mm PC fans fit snugly in a line atop dual 24”x16x2” MERV13 furnace filters. This application requires high static pressure fans (> 2 mmH₂O) e.g. Antec Fusion / Prizm $50-80 in 5-pack with LED controller. antec.com/product/coolin… Cheaper chassis fans won't work

e.g. would be sweet if these pre-assembled Asiahorse triplets worked but like most chassis fans they don't hold enough static pressure to push through MERV13.

These spartan pre-assembled 120mm triplet fans amazon.com/dp/B081WV1FHK?… push even stronger filter flow than Antec. They also come with an AC adapter & much simple wiring but buzz noticeably louder and not so pretty.

Stay tuned for detailed build instructions, Amazon shopping list and foam board template.

Bill of Materials all available outside Amazon, but here's a list: amazon.com/ideas/amzn1.ac…

Template for cutting and drilling top plate. Make sure to print actual size! Use compass tip to punch centers and drill holes. Spin the template around 2nd center and will be ready to punch 3rd fan. Repeat until 5 fans punched. icloud.com/iclouddrive/08…

Make sure all fans are oriented with wires coming out at same angle so that the RGB light show will be synchronized. Consolidate wiring into a bundle with ties or tape

For fans to blow out (and suck into filters as normal for CR boxes), they will need to be mounted with the ‘back’ of fan facing out. Antec Prizm has rgb rings on front and back so front ring will make filter glow at night

Antec Fusion only has light ring on front, so to be visible from top will end up with reverse flow pushing into the box and out the filters. Don’t think this hurts anything except fan blades may accumulate more dust

Unless too plate is made out of something more rigid than foam board, will need to seal edges between fans and top plate with silicone

Building box with double sided carpet tape. Cord will go through little notch at bottom of one side

Screwing grills and fans into foam board top plate. Screw alignment can be tricky depending on how precisely the holes are punched/drilled.

Test top assembly ensuring all fan power and light cables have good connection. Cycle the rgb mode to rainbow etc now with black button as Antec fans don’t come with remote. Connected AC->Molex->SATA->black box end connectors

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