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