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A fume extractor uses an activated carbon filter and fan to remove the smoke, and noxious fumes, created from soldering. The average price of a small hobby version is about $100, this one will run you about $10. This fume extractor will not be as effective as a larger one, but it is better than nothing, and extremely portable. Remember, always work in a well-ventilated area.

Parts you need:

(1) 7812 – Voltage regulator
(1) Candy tin
(1) Switch
(1) 40 mm case fan
(2) 9-Volt batteries
(2) “Cheap” 9V battery connectors (see step 2 & 3)
(2) Pieces of screen
(1) Piece of activated carbon filter
Some heat shrink tubing
A few inches of Wire
Rosin core solder
Miscellaneous screws and washers
Paint (optional)

Tools you need:

Soldering iron
Dremel with cutoff wheel
Drill & small drill-bits
Fine tip marker
Various Screwdrivers
Wire cutters
Safety glasses

Step 1 : Build the circuit


I decided that that a quick mock-up might be a good idea. I am glad I did. At first, I thought that running the case fan off of just (1) 9-Volt would provide adequate power. In the end I decided that 12 volts “sucked” better, and in this case it’s a good thing.

The final circuit uses a simple switch, (2) 9 volt batteries, a 40mm case fan, and a 7812 voltage regulator. The 7812 takes voltage from the (2) 9-Volts that are wired in series and steps the voltage down from 18-Volts to 12-Volts, which is what the fan requires.

Step 2 : Solder components
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Notice the battery connectors; they are the flexible vinyl version, not the hard plastic type. This allows them to easily fit in the case.
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This is a very simple circuit. Solder it according to the diagram, making sure to attach the component leads to the 7812 properly. Don’t forget to use heat shrink tubing on the connections, this is in a metal box…..metal conducts electricity!

Step 3 : Make sure it all fits
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Everything can be stuffed into the tin, but make sure you use the cheap kind of 9 volt connectors. The cheap ones are the kind made of vinyl, not rigid plastic. The difference in thickness is minimal, but it is enough to stop you from putting both 9 volts in the case.Step 4 : Cut & Mark the openings (Wear Safety Glasses!)
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I used a marker and a paper template for the fan openings. The openings are 35mm square. I marked the opening for the switch at the same time. Then I cut all the openings with a Dremel tool and cutoff wheel (Wear safety glasses!). Next I marked and drilled the (2) holes for the switch screws and (1) hole for the regulator.
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After you cut the first fan hole, close the box and use the 35 mm square paper template to align the second hole. Just “eyeball” the placement. In reality it isn’t that crucial to have them exact. There is room for error.

Step 5 : Paint
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I decided to paint the tin this time, unlike my plain RuntyBoost. I chose a nice red Krylon paint. I hot glued a scrap piece of wood to the inside, so I could hold it while I spray painted it. Two quick coats and I think it looks good. Krylon paint is fairly toxic and flammable, so paint it outside and away from everything!

Step 6 : Attach the regulator and switch
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First screw in the 7812 using some washers and a screw to space it from the side of the tin. I used a #6-32 screw and (1) washers to keep it from the edge, but you can use anything that fits. The screws and washer will also act as a heat sink. Finally, screw in the switch

Step 7 : Add the screens and filter


Here you can see the screen-filter-fan-screen sandwich. The screens are 50 mm square & the filter is 40mm square. You can buy replacement filters for the commercial extractors at a reasonable price. Next, just hot glue, or epoxy, the corners of the screens down, and sandwich the filter and fan in-between. Compression will ultimately hold it all together.

Step 8 : Admire your work
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All done! I am happy with how it came out, but it definitely needs some graphics to spruce it up. Any suggestions?
Step 9 : Test
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I have run mine continuously for hours and have had no heat buildup from the 7812 and the fan is still running strong. It seems to work quite well, although it is no replacement for a large fume extractor, it will come in handy for small projects. Remember, follow all safety guidelines when soldering, and work in a well-ventilated room, even if you have a fume extractor.

  • MC

    Good demonstration of how to use a 7812, but 1/3 of the battery power is being turned into heat in the 7812. This raises a number of questions. Would the fan run acceptably on just 9 volts? (No battery power wasted.) Would it be damaged if you gave it 18 volts? (Quite possibly, but we don’t really know, and if not, it would run nice and fast.) Of course, a high-efficiency switching regulator would be too complicated for this type of project. But let’s keep thinking…

    Of course, it’s quite possible the designer tried these things and concluded that the design published here really is the best.


    forgo the 7812 and use 2AA & one 9V
    1.5V x 2 + 9V =12V

  • Marc de Vinck


    9 Volt was not strong enough, I tried it.
    18 Volts seemed too much (but I really don’t know)

  • Marc de Vinck


    True, or I could use photo batteries that are 12v, but I wanted to make a little project using the 7812. I ran mine for hours and had almost no heat, and the fan still runs strong.

  • knotlinks

    beautiful project, and extremely useful. Much nicer than the comp fan I have hooked up to a computer psu.

  • Marc de Vinck


    Thanks! There will more in the future.

    If you happen to make one….Please send me a picture!

  • jproach

    The price of a hobby fume extractor is much cheaper than $100, can move a lot more air, and wouldn’t require one to replace batteries (example:

    but anyway I think this is a very nice presentable package, good for small jobs.

    • Marc de Vinck


      That one is really cheap!

      But the “average” price is still about $100.

  • Adam P

    I scoured the web trying to find a site that explained how to determine what battery power I needed to run a case fan, so I am thrilled to find yours and I have a few questions for you.

    1) About how long will the fan run on the 2 9volt batteries?

    2) Will rechargeable batteries work just as well?

    3) I know it is long, but please bear with me!

    My “project” is I want to create a smart fan…that can sense the temperature and turn on when the temperature drops below the desired temp, and turn off when the temp exceeds the set temp…much like a household thermostat. There are 2 wrinkles to my plan:

    1) Rather than connect the “thermostat” to the house, I want to connect it to a fan, much like the one you have here. This hurdle seems small enough to me. If I used a thermostat or something similar, the electronics and the existing brains would act as my switch and it can manage power to my fan (provided I dont have power conversion problems which you may wish to warn me of).

    2) Any ordinary household thermostat wont do, because the temperatures I want to register are between 100 and 800 degrees farenheit and most household thermostats only register 90~100 degrees F. To overcome this, I considered taking a thermostat from an oven, since it is designed to handle the higher temperatures, and still in many ways acts like a household thermostat in that it can manage the provision of electricity to maintain temperature.

    Do you have any thoughts or suggestions on this? I’m really interested, but I know nothing about engineering and electronics, etc. I just want to find a cheap way to manage the temperature of my BBQ grill by managing airflow. Similar systems online sell for $200+ and I’m hoping to build my own for much less. Can it be done?

    Thanks for your patience and ideas!

  • Marc de Vinck


    For your purpose, I would run it from (1) 9 volt. I needed more “juice” to get the airflow through the filter, which you don’t need. That will eliminate the need for the 7812 or a switching regulator. Check Google for thermostat circuits, temperature circuits, etc….there are a lot online.

    Rechargeable batteries have a lower nominal voltage. Figure out the circuit prior to making a battery decision. Since space will not be an issue (Heat will!) I would suggest using other types of batteries.

    Good luck, and if you make one…..send us a link so we care share it with our readers.

  • Lincoln

    What’s a good/cheap/easy source for the Activated Carbon filters and the screen?


  • Marc de Vinck


    The screen can be purchased at any craft store (I paid about $2 for enough to make about 50) or Home Depot. Better yet, salvage from anything with a screen or perforated metal.The filter can be found online, (Amazon, any electronics supply stores) look for replacement filters. You can get them really cheap, and 1 filter is enough to make 6 -10 mini fume extractors.

  • Eli

    How about taking apart a 9v and using two extra cells out of it so you get 12v. Just keep the extra 4 for the next time you change the batteries.

  • Anonymous

    Why not run it on a car battery?

    Seriously though, great how-to!

  • Marc de Vinck


    Great idea! – Now try it out and send me an email w/link to pictures!


    Car battery? That would be a good idea for a bench version. It certainly would last a long time!

  • Maltedfalcon

    Cant you just use a 12v wall wart?

    • Marc de Vinck

      You sure can, but the portability is really handy.

  • BigIg

    I Have a bunch of 120mm case fans, I imagine that, although it would be bigger, it would probably work better. Now to find a box that fits it nicely.

    Sure, I’ll be loosing the portability factor, since I’ll probably rub it off a AC-DC adapter anyway, but I’m not worried about portablity, I just need to stop soldering without one of these things!

    • Marc de Vinck

      I’m glad this inspired you to add some safety to your lab.

      I think 1 of your fans would be enough, maybe 2?…..mine is tiny and it works great. If you make one, which I hope you do, send me a link to some pictures!

  • Sil3ntP8nd8

    How long will the batteries will actually last?

    How about USB powered? Id rather have it be USB powered since i work next to my computer and have the option of using a battery or not. thanks

    • Marc de Vinck


      You can calculate the time (roughly) if you know the maH of the batteries and the specs of the fan. (you lose a lot due to heat of the 7812) All I can say is mine lasts a long time!

      I would look for a 5 Volt fan and goggle “usb wires”. You should be able to hook it up fairly easily. The main problem will be a 5 Volt fan may not be strong enough to suck the smoke through the carbon filter. That is why I went with the 12 volt system.

  • le Cauchemar

    Nice Project.
    What about changing the filter?
    Do I have to? After what time?

    • Marc de Vinck

      Thanks! Yes, you do have to change the filter. Luckily, you get about 4 “mini” filters cut from a standard filter size. They end up being really cheap. I change mine when the airflow slows or is “looks” dirty.

  • benoitespinola

    By putting a 12V adapter and a couple of entries (so you can choose the tin’s orientation, you can save a lot of space inside the tin and put a second fan so you have 3 options : none of the fans runing, just one or both… What do you think on this?

    To get it portable you can also make a tinny box where you put your two 9V batteries and your 7812…

    Or you can integrate the 7812 in the main tin so you are shure you always get 12V for the fans….

    • Marc de Vinck


      That’s a great idea!

      My main goal was to make it portable and cheap. Adding a power adapter and second fan increases the cost (a bit) and makes it less portable. However, having a choice of 1-2 fans and different orientations is GREAT!

  • Joel Smith

    I’m having trouble finding the appropriate filter locally. Any tips on sources or links to suppliers?

  • Joel Smith

    I built the project as originally described here and it’s working great. I found activated carbon filters in the aquarium section of the local pet store, and they seem to do the job.

    I think I’m going to try building a bigger version with a VHS tape case and a bigger fan, and will use the 12V adapter instead of batteries since I already have the portable version now. Has anyone tried a larger version?

    • Marc de Vinck


      That’s great! I would love to see some pictures!!!

      Thanks for the tip on where to get the filters.

    • Robert

      It’s based on a 120mm 12v fan and a RadioShack project box. See my comment below for a picture. I’ll taking more pictures and doing a build write-up on my blog at some point.

      • Marc de Vinck

        @ Robert

        This is great, thanks for posting the pics. Send me an email when you have them all up so I can blog it! Thanks!

  • cessna928

    I was wondering, what speed difference an LED would make if I added it in series and would I likely have to add an additional resister to keep it from burning out? I’m sure it probably depends on the particular led, but still I thought I’d ask.

  • Chris

    Well there is a fun project! Just so everyone knows you could add 4 LED s in series parallel to the fan or you could put another fan on the outside in stead, also in parallel. Or you could find a 5 volt fan and just wire it the same except the 7812 is a 7805 and the fan is now a 5V fan. also do you guys know how to post an article on the MAKE blog that would be nice to know.

    • Marc de Vinck

      Thanks for the ideas. I like adding LED’s. I am going to have to try that out.

  • Daniel

    Hi, first of all, nice project! Really like the idea.

    I’ve got a question though, I’m not that well versed in electronics and most fans I’ve inspected come with a 3rd (signal) wire, which I assume is used to report the RPM of the fan to the motherboard. Anyway, my question is this:
    Should I rather just cut off that cable and isolate it, or should I just connect it to ground?

    Thanks for any help.

    • Marc de Vinck


      Try using just the (+) & (-) to be sure you have it right…..then cut the 3rd wire. One last thing, send me some pictures when you are done! I would to share them with our readers.

  • Robert

    I just finished building a larger fume extractor having been inspired by this how to.

    There is a photo of it here:

    I’ll be posting more photos at a later date.

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