Desktop Air Purifier (Fume Extractor)

Intro: Desktop Air Purifier (Fume Extractor)

This desktop air purifier / soldering fan is a great project - it integrates some electronics, woodworking and general tinkering. Not to mention it's a great desk accessory, perfect for removing any odors in the air, or for when soldering.

The unit is compact and lightweight and you could bring it with you anywhere - place it on your desk at the office, use it in your car, or anywhere the air needs a little freshening up! Not to mention, if you turn the air purifier around, then you have your very own desktop fan, pretty cool.

STEP 1: What You'll Need

Parts:

• 2 computer fans (90 mm, 24 volt)
• 12 volt ac/dc power supply
• voltage booster
• 10 K ohm potentiometer
• 3000 ohm resistors
• charcoal filter
• mdf
• wood for knob

Method:

Well, let's start with the basic parts. I have two 90 mm 24 volt computer fans, I picked mine up really cheap from a used sale at the local university, however you can always order them online.

I'm using a 12 volt DC power supply, however since they're 24 volt fans, and I want to be able to utilize that extra capacity, I'm going to connect them with a voltage booster.

STEP 2: Voltage Range

To control the speed of the 24 volt fans you will need a voltage booster. On the voltage booster de-solder the potentiometer and extend the lines while adding two 3k ohm resistors in line with a 10k ohm potentiometer/switch. Solder the incoming negative power line to the switch and the fans in parallel with the voltage booster. Set the maximum voltage by adjusting the potentiometer on the booster and the range through the 10k ohm switch. Confirm the desired values with a multimeter.

If you wanted to avoid the booster and the extra work, then you could just directly hook up the fans to a 12 volt power supply and use a switch.

STEP 3: Cutting Up the Box - Xcarve

So now it's simply a matter of enclosing all these parts in a neat little package.

I decided to use MDF for the box, and here you can see I'm using the Xcarve which is a CNC machine to cut out the parts. I have an svg file ready to use if someone else wants to do this too.

STEP 4: Cutting Up the Box - Saw & Drill

Of course if you don't have an X-carve, then you can cut the pieces out with a saw and I have a set of templates that you can print out and glue on top of the pieces to get all the holes right. In that case I prefer to glue on the paper with a glue stick, and then use either the drill or the drill press to cut the holes.

For the two large holes, I use a 3 1/4 inch hole saw.

STEP 5: Assembling the Box

Once you have all the pieces cut out for the box it's time to connect them. I prefer to put on some yellow glue on the edges, as well as some hot glue. The hot glue works as a clamp as the yellow glue sets up and dries.

I'm putting in a couple of these small support pieces in the corners to provide a little extra strength. Now as a filter I ordered a charcoal filter meant for a range fan. I'm just fitting it in the box and then I'm notching out the space for the little support pieces in the corners. I'm also doubling up with two pieces of filter and then just continuing to put the box together. I'm also gluing together some thicker support pieces which I will glue in to the box which the backing will screw in to.

STEP 6: Finishing the Box

OK, so now I have the basic box complete, which means all the sides together, except the back with the fan holes which will screw in later. So to finish, I'm starting with a coat of shellac, then sanding. Then a coat of primer. I'm also adding spackle to any areas that have imperfections. Then painting the pieces white with a flat paint and finishing with a water based polyurethane.

STEP 7: Trimming Wires, Soldering, Filter

So the box is finished, now let's go back to the contents of the box. And here I'm just going to trim up some of the wires and soldering some of them in place. Here we have the power connecting to the switch part of the potentiometer.

I'm inserting the filter into the box. I have these thin pieces of MDF I cut up to keep the filter in place inside the box, and I'm simply hot gluing those to the support pieces to keep everything neat and tight.

STEP 8: Securing the Fans

Next I'm screwing the fans into the back piece, and the holes fit perfectly. To clean up some of the wires, I'm twisting them around each other so they stay together and then securing to the fan with a plastic zip tie, just because I don't want the wires to be all over the place.

STEP 9: Connecting

Time to connect everything in place. So I'm connecting the wire I twisted from the fan into the booster and securing it in place. At various stages I confirm that everything works and that nothing has shorted or come loose. Then I bring the parts into the box, and especially the potentiometer twist knob which goes in the side of the box. I put a nut on the outside and then I secure it.

The power cord goes in the back, right below the fans, it's a pretty tight fit. Then I'm hot gluing around it to secure it in place. Also securing the booster with some hot glue, as well as some wires to the side of the box, because I don't want them to interfere with the fans.

And then it's time to close the back, fit the fans in, and I'm screwing the back in place with some small screws that goes into those support pieces I glued in place.

STEP 10: Knob

Ok, now to make that knob on the side a little more comfortable to turn, I decided to make a bigger knob. Here's a piece of walnut on the lathe. Then I'm just drilling a hole in it, so it can fit around the metal knob. And I'm epoxying the large knob on top of the small knob. OK, now that just has to dry and we're ready.

STEP 11: Conclusion - Watch the Video

This is a really fun project, and works perfectly no matter whether you're using it to clean up the air, for soldering, or as a personal fan. For a much better perspective and to download the svg & pdf files, make sure to check out the video.

Comments

[Raamah]

Thank you for the inspiration to build my own air purifier for using while soldering. I managed to build a very basic one using spare parts and 12v computer fans I had lying around, some cardboard and an air purifier filter which was the only part I purchased. I used elastic bands to hold the filter sandwiched between two pieces of cardboard and plenty of hot glue to hold everything together and seal gaps. It works really well!

[r19108]

I want to build a simple air purifier. However, I don't have the knowledge/experience to work with electronics on scale like this project. I'm thinking of building a simple purifier out of a cardboard box. Will place a small(not sure how much CFM I should take) exhaust fan on top and place HEPA/Carbon filters on one/either sides. Will use tape to close all gaps and replace HEPA filter. Some questions:

1)Is there a chance of implosion if the fan is too powerful?

2)Will the output of the system be equal to the CFM of the fan? I think it shouldn't be any lower as then pressure will keep lowering in the system, causing an implosion.

3)Is there any way to tell proper CFM with HEPA filters? I will use 12"x15" HEPA filters.

4)How will air re-entering the system affect CADR (number of times air circulates in the room)

Thanks.

[bosko90]

Great work! You gave me the idea for my fume extractor. (the color is the same by chance, because I had an old spray from the previous car). I made a a small, but this has proved to be worse, because it does not capture all the smoke. I should use a more powerful fan with higher CFM.
Here is my build:

[terrace_dr]

Here is a link to a video of my build.
https://youtu.be/NVRnpxDBWog

[andrew.larson.14289]

Could I stack multiple fans behind them to boost suction? I have 12 48V fans I want to use

[Yonatan24]

Probably not... I believe that there is some law in physics that explains that

[terrace_dr]

can you please give me a guide better than your hand covered and not so good pictorial description of the electronic wiring. I understand it is a simple circuit but I don't know what you mean when you say put three 3000ohm resisters in line with the potentiometer. Also It looks like you have only two wires connected from the trim pot on the booster to the board. Are there not three connections from that trim pot to the board? Also I am using an independent switch because I can not find a potentiometer/switch. So can you give me some guidance on how to wire it with and independent switch?
I really think if you are going to do electronics no matter how simple, you should be giving a schismatic to show the understand of the components and their relationship to the project. Otherwise, building any type of circuit and teaching it to the public is useless!

[terrace_dr]

Where are the templets for hole locations and size of box??

[Myosotis]

Hi!

Very good project, I just can't understand where you put the resistors, may I ask some kind of diagram?

[stillash]

This is awesome and looks amazing! Any chance there is a circuit diagram?

[poundchannel]

Great job! I recently decided to make something like this, and this is my favorite design by far. Since I also have an X-Carve, where can I get the SVG file?

[darbinorvar]

Thanks, I have the easel file link in the description of the video, as well as all the svg files.

[definingsound]

I'm torn between making this 'able, or the one with the active charcoal filter seat cushion. Or I could make my own 'able for the "polite light", a random 10-60 seconds after a button is pressed the "fart alert" light can turn on in the vicinity of the office that needs a few minutes of avoidance.

[rogerhyam1]

Why not run the fans the other way and include a ioniser to clump up the particulates so they are more likely to get caught by the filter?

[0xffff]

Ozone, as a layer in high atmosphere has positive impact: it stops sun's nocive UV light.

At ground level, it's an harmful pollutant. Specially present during hot weather (reaction between volatile organic compounds and nitrogen oxyde).

You can notice, although very common 10-15 years ago, air ionisers have almost totally disapeared today

[randalosgood]

You don't need an ionizer. Most serious furnace filters these days automatically ionize as particles enter the filter and are caught as they exit. Just clean occasionally. However, I don't know if they make them that small!

[chris.milne.771]

Ionizers have been shown to be bad for your lungs as well as making particles stick to everything in the room, and filtering works better pulling air through the filter first than blowing it into the filter for several reasons.

[Yonatan24]

I've heard that Ionizers turn air into O3 (A.K.A methane), which is good for you in small quantities but it can dissolve plastic plastic into air

[Flyboyron]

It's ozone, not methane. And it's produced by every lightning storm, as well.

[pmk222]

I could be wrong (it has been known to happen), but i believe that there have been several scientific studies that have shown negative ions have health benefits. though you shouldn't use and ion generator in non-ventilated areas, they work similarly to ozone genorators and thus produce small amounts of ozone and that can build up causing health issues.