Air purifier (BlueAir 411 filter) by madewhatnow

Last crawled date: 3 years, 2 months ago

This is an air purifier, built around readily available commercial parts and printable on most 3D printers with a 220 mm build plate. Depending on your ambitions, it can be a 'dumb' device with a simple on/off switch, become somewhat smart with an Arduino and fan speed control, or go fully smart, with inbuilt particle and environmental sensors and possibly linked into a smart home or a online dashboard.
Testing the unit showed that it rapidly increased air quality in small to medium sized rooms, even in extremely bad air (250+ AQI outdoors), as observed recently across the US west coast. In all but the worst conditions it will reduce AQI quickly to acceptable levels indoors.
At minimum, the bottom plate and the top unit have to be printed. The filter itself is stable enough to support the assembly short term. Long term, I would recommend adding the inner frame (2 helical assemblies) and the guard, to avoid injuries.
If you want to get fancy when 3D printing the guard: print it in two colours by swapping out the filament, and print the flat ring in black, contrasting with the white fins on top.
The BlueAir 411 units come with a cloth prefilter sock. It fits this design as well, and will help keeping hair and larger dust off the filter itself, and can be washed and reused. Highly recommended!
Updates:
2020-10-02: Uploaded basic control code on Github
2020-09-17: Noise optimisation
Added a fan guard with fewer struts to cut down on wind noises.
Parts:
4 M3 screws (8 mm or longer) and nuts, various cables.
The Blue Air 411 replacement filters are readily available (both branded and off-brand for usually 10-25$/filter, and with much shorter lead times than the whole unit.
The washable prefilter socks are available in multiple colours.
While any 140 mm fan (up to 38mm thickness) can be used, I would recommend a 12 V 4-wire fan optimized for higher backpressures (e.g. for cooling a radiator in a watercooled system. A high-quality and quiet solution is the Noctua A14 iPPC 3000rpm, which can move up to 180 cfm with reasonably high back pressure.
If noise is not a concern, the Bgears b-Blaster 140x38mm is an absolute beast of a fan. It makes appropriate turbine noises at over 5000 rpm, but moves an impressive 300 cfm of air against even higher static pressures. You will not enjoy having this run in the background, though. If you plan to implement adjustable speed controls, or only care about maximum filtering ability, it can be an acceptable choice. Make sure your power supply can deliver at least 3 A (or more) of power, and watch your fingers if the guard is not installed. That fan uses about 30W of power compared to 6W on the Noctua, which is beyond the specifications of most breadbords. Wire things up accordingly and use suitable wires. I would go with the Noctua, though.
A basic power supply with 2 A or more will easily do the job with the Noctua fan.
For the b-Blaster, something stronger is highly recommended, but any 12 V 3 A+ unit will do.
For the minimal installation, I'd otherwise only recommend a power switch.
For a smarter version, the Arduino Nano Every is an inexpensive little board that can run directly off 12V: single or triple pack, and works well with a potentiometer to adjust fan speed. Perhaps get a pretty cap for it as well?
And if you want to make keep track of of particle levels in the air, or want to make the air purifier increase fan speed when particle numbers in the air go up, this is the sensor you need. Please support Adafruit! If they run out, Amazon got you covered as well. The top unit already has a cut-out for this sensor, that allow it to monitor the air outside the filter housing.
If there is interest, I can also upload designs for other filter designs (e.g. Medify Air or others), with higher MERV/HEPA ratings.
(Amazon links are affiliate links, to help with coffee & printing filament).