Modular Air Purifier And Dryer

Air Purifier

It wanted a simple air purifier for my print room that would look good and do the job. I could buy one, but then I'd be paying typically $40 or more, plus the cost of refills. And I don't like how most of them look.

Building on some experience I had reverse engineering the Apple Studio curvature, I thought I'd play around with similar curves for this unit. Throw in a little Japanese and Star Wars inspiration, and here you are. 

This build uses off the shelf components. The only hardware you should need is a 120mm fan, a barrel jack panel mount, and a Levoit Core Mini compatible filter. Oh, and a power supply to run the fan. 

All parts are printable on a Prusa Mini. 

Build

BOM

• 1x Fan Housing
• 1x Fan Retainer
• 1x Filter Housing
• 1x Levoit Core Mini compatible HEPA filter
• 1x Panel Mount 5.5x2.1mm Female Barrel Adapter
• 1x 120mm case fan

Instructions

1. Print the three parts. This will take a while, these are relatively large parts. Everything prints well with PLA, I recommend at least 2 walls and 15% infill. I ran my air filter with 15% lightening and it came out pretty, but fragile. A little infill would go a long way.Everything prints well with PLA, I recommend at least 2 walls and 15% infill. I ran my air filter with 15% lightening and it came out pretty, but fragile. A little infill would go a long way.
2. Figure out the rotation direction of your fan. You want the airflow to go towards the floor, so make sure your fan is oriented correctly and your wiring is correct before you solder anything.
3. There is a hole in the Fan Housing to let the fan power cord pass through into the lower chamber. 
4. From there, you'll see the mount point for the Barrel Adapter. Make sure you have the Barrel Adapter nut on inside the Fan Housing, then push the wire through the mount point.
5. Solder on the Barrel Adapter. Double check your wiring!
6. Push the Barrel Adapter into the slot. Thread the nut on from the other side. Yes, I know, the nut is a pain. Fortunately you only have to do it once.
7. Place the fan retainer on top of the fan.
8. Put the HEPA filter into the Filter Housing
9. Slot the two pieces together. Start with the corners 45 degree offset, then twist to tighten. 

Congratulations!

Notes

Yes, I know, most commercial versions use PPM sensors to adapt their speed, but I don't really need that at this point. Someday, or if there's popular demand, I'll eventually get a suite of sensors and a fan PWM board to build this out into a smart fan/sensor platform. The dream is to have it on an ESP to make it accessible to Home Assistant, Google Home, or Apple Home. One day.

Use a fan that you're comfortable with the noise at full speed. There is no speed controller, so this thing will run flat out all the time. Great for a print room, bad for your kitchen. However, I think a great secondary adder would be to use a smart outlet to control the on/off function and embed that into your smart home setup.

Noctua fans have low flow. Quiet, yes, but they struggle to pull air through the filter. 

There is no sensor on the filter, so check it occasionally. Filters are consumables!

Air Dryer

I live in a humid climate. I have a couple closets that rarely get opened but are really humid. Thought I'd take a stab at a desiccant air drier to see if it will help. I do not recommend this for living spaces! It won't do much and you'll just end up wasting filament and time. It will look pretty though…

The Dryer uses all of the same off-the-shelf components for the Fan Housing as the Air Filter. The only thing different is the need for desiccant. You'll need a good bit of it to fill the space. I don't have an exact measurement yet, but it's pretty substantial. This is a little faster to print because the Dryer module is shorter than the Air Filter module. 

Build

BOM

• 1x Fan Housing
• 1x Fan Retainer
• 1x Desiccant Chamber
• 4x Desiccant Chamber Screw
• 1x Panel Mount 5.5x2.1mm Female Barrel Adapter
• A bunch of regenerable desiccant
• 1x 120mm case fan
• (Optional) 1x Desiccant Chamber Funnel

Instructions

1. Print the parts. Everything prints well with PLA, I recommend at least 2 walls and 15% infill. If you print the funnel, use vase mode and make sure you don't have top or bottom infill. The Desiccant Chamber does have some severe overhangs, but it's not critical if they don't work well. Just trim off whatever your printer didn't handle and you'll be fine. It's hidden anyway.
2. Figure out the rotation direction of your fan. You want the airflow to go towards the floor, so make sure your fan is oriented correctly and your wiring is correct before you solder anything.
3. There is a hole in the Fan Housing to let the fan power cord pass through into the lower chamber. 
4. From there, you'll see the mount point for the Barrel Adapter. Make sure you have the Barrel Adapter nut on inside the Fan Housing, then push the wire through the mount point.
5. Solder on the Barrel Adapter. Double check your wiring!
6. Push the Barrel Adapter into the slot. Thread the nut on from the other side. Yes, I know, the nut is a pain. Fortunately you only have to do it once.
7. Place the fan retainer on top of the fan.
8. Use the funnel (or freehand it, maybe you're better than me) to fill the Desiccant Chamber with desiccant. I found that I only needed to fill from one corner and shuffle the desiccant around with some shaking. If you do it this way I recommend installing 3 of the 4 screws before you start this step.
9. Install the (remaining) Desiccant Chamber Screws. Make sure the screw heads are below the top level of the chamber, since this face meets the Fan Housing face.
10. Slot the two pieces together. Start with the corners 45 degree offset, then twist to tighten. 

Congratulations!

Notes

As noted above, the Desiccant Chamber has some steep overhangs. If this part works and becomes popular I'll modify to reduce some of the overhangs. I might also modify to make a larger chamber so it lasts longer.

A Noctua fan works just fine for this application. Pulling air through the desiccant is not a high enough pressure loss to make the Noctua nonfunctional.