Introduction: DIY Mini Soldering Fume Extractor

About: Enjoy building and tinkering with a particular passion for electronics.

Soldering is fun! Breathing nasty fumes isn't. This guide will show you how to build a "mini" but powerful soldering fume extractor. Featuring a 32 CFM dual fan assembly and a small footprint, it packs away easily for storage or makes a great addition to a portable soldering station. The fan's small form factor and power are due to its previous life as a cooling component in compact servers, where "failure is not an option" is the standard.

The design includes an optional fan-speed adjustment control knob. Fan speed is controlled via a Pulse Width Modulation (PWM) input built into the fan. Pulse width modulation works by turning the voltage on and off very quickly, just like an LED dimming circuit, thereby reducing or increasing the fan speed.

This design shown uses brass but other material options are included to meet your particular needs.

The mini fume extractor consists of the following main components:
- 12V dual in-line fan assembly
- Fan shroud with activated carbon filter
- Mini tripod and base assembly
- ON/OFF Switch

Optional components:
- PWM control circuit board
- Fan speed control knob
- Resistors, used only if your PWM circuit board has an adjustable duty cycle, in which case it should be fixed to 50%
- Housing for electronics

Files provided include:
- Bill of Materials (BOM) for an aluminum, brass and plastic version
- Schematic detailing the wiring
- Metalwork PDF drawing for the fan shroud, electronics housing and tripod base
- Wiring color code for the fan
- Artwork PDF for the enclosure labels
- Vector files (.svg) that can be edited for customization

Total cost ranges from about $25-45, depending on the material you choose to work with. Cost can be further reduced by omitting the speed control option. There are 3 materials to choose from, they include: aluminum, brass or plastic. There is an added material cost when working with metal as well as a greater tool requirement. Choosing plastic cuts down on cost and time while remaining durable.

Video Demo

Tool Requirements PDF

Step 1: Choose Your Material Type

Select material of choice and aquire all the items from the appropriate Bill of Materials (BOM).
Acquiring all items before cutting your metal will ensure everything will fit.

Bill of Materials PDF

Step 2: Fabrication

- Print the 2 metalwork PDF files on regular paper (applies for plastic as well), do so at a 100% scale (1-to-1 ratio). See link below for PDF's.
- Cut out all the pieces and glue the paper outlines onto the material you will be working with. Spray glue works best when adhering paper cut-outs to the material.
- Use a center punch to mark the holes that will be drilled out, these are denoted by the plus sign on the drawings.
- Drill out the holes with the closest sized drill bit you have.
- Cut the metal. Wear safety glasses! If you're cutting plastic simply use scissors, easy!
- Bend the material. The bend order is denoted by red numbers in the PDF document. The bend order is only important if working with metal.
- It's time to assemble the shroud. If you use:
BRASS you can solder the tabs with your 50W soldering iron. Follow the same guidelines you would for regular soldering, that is first clean with 91% isopropyl alcohol, smear area to be soldered with flux, and pre-tin the joints before soldering. You can hold the pieces together with binder clips while soldering.
ANY OTHER METAL can be joined together using rivets or screw and nut assemblies.
PLASTIC can be taped together using clear packing tape. Epoxy can also be used, the pieces can be held together with binder clips while it dries.

Fabrication Notes:
- Hint: build a preliminary model out of paper first, to ensure everything will fit properly.
- Brass is the only metal that can be soldered together.
- If working with any other metal don't forget to include extra holes along the seams for assembling the parts together with rivets (or screws).
- If using a fan with different dimensions edit the vector files accordingly.
- If working with plastic, you can forego the screw hole tabs in the fan shroud. The electronic housing enclosure won't be required at all.

Mechanical Drawings Folder (PDF's and vector files)

Step 3: Electronics

- Print out schematic to follow along.

Your fan assembly might have come with different wiring colors than those indicated in the schematic, however if you pry the 2 fans apart, in between the two fans you will see the wire colors from the schematic. To do so, pry along the corners with 2 thin but rigid flathead screwdrivers or similar tool. Make the connections as follows:

12V --> 12V (red/orange)
GND --> GND (black/grey)
PWM --> PWM (green)

- Wire up and solder into place the ON/OFF switch.

Electronic Notes
- Hint: highlight the schematic connections as you actually make them to verify your work.
- Hint: wire everything on a Proto-board first.
- Potentiometer Primer: a potentiometer or "pot" for short, is a variable resistor that is adjusted with a knob. A pot will have 3 pins. Pin 1, Pin 2 and Pin 3. The pot will always have its maximum resistance value across Pins 1 & 3. Adjusting the pot will vary the resistance across Pins 1 & 2 and Pins 2 & 3, as the resistance goes up across Pins 1 & 2 it will go down across Pins 2 & 3 and vice versa. Take one apart to see how it works.
- The PWM module might need to be modified if the PWM circuit didn't come with a finger sized control knob. If it came with a multi-turn pot (one that requires 5 or more turns usually with a mini flathead screwdriver) it will need to be replaced with a larger single turn pot that is easy to adjust. To determine the value of your replacement pot measure the resistance of the PWM control pot (across Pins 1 & 3), unsolder it and replace it with a pot of the equivalent value. If the PWM module also came with a duty cycle pot (this determines how long the voltage is ON and OFF), set this to 50% (that is, it's ON 50% of the time and OFF 50% of the time, measure this on an oscilloscope). Now measure the resistance across the duty cycle Pot's Pins 1 & 2 and 2 & 3, remove the pot (only if it doesn't fit in the housing) and solder equivalent resistances in place (one resistor across Pins 1 & 2 and a 2nd resistor (if needed) across Pins 2 & 3) since there's no need to adjust the duty cycle. If the pot fits in the housing you simply set the duty cycle to 50% and glue down the adjustment screw.
- If the components are too tall to fit in the enclosure then unsolder and remove those components so the circuit board can fit into your metal housing (or make the housing bigger). I had to remove the power connector and input and output pin headers.
- On the PWM circuit I used, I measured a 300mV peak-to-peak voltage PWM output signal at 25kHz.

Schematics PDF
Fan Data Sheet PDF
Short video showing PWM circuit working
Short Video showing Duty Cycle adjustment

Step 4: Test and Construction

- Before you close everything up, test it.
- Test the ON/OFF switch
- Test the fan speed control knob. Once the fan is working properly stick the circuit to the top of the fan with double-sided foam tape or simply envelop in heat shrink. Attach the potentiometer to the enclosure. Screw the enclosure onto the fan. Use double-sided tape to adhere the decals to your enclosure. Attach the shroud to the fan. (If you're building the plastic version, cover the circuit with large heat shrink (or electrical tape) before taping it down).
- Finally cut down your activated carbon filter to size and insert into the shroud opening. Although not needed an extra hole was included in the shroud to facilitate insertion and removal of the filter. A plastic car trim rivet is used to seal the hole during regular operation. Note: it is important to use an activated (or active) carbon filter due to its superb absorption capability. Activated carbon because of its structure has an increased surface area relative to its size, it is able to attract and retain large amounts of particulates. This is especially important in this application due to the small filter size we are using.

Testing Notes
- The fan is very powerful and will scuttle it's way across your workbench unless it's held down. (I used a cell phone sticky pad to adhere it to my workbench).

Step 5: Tripod Assembly

The tripod consists of several parts:
- mini camera tripod
- plastic nut that screws onto your particular tripod (I found a wing nut and had to cut the wings off)
- metal base that attaches the tripod to the fan assembly
- epoxy or liquid metal putty used to adhere the plastic nut to the metal

- Screw the plastic nut onto the tripod. I covered the plastic nut with heat shrink.
- With your metal base cut out and bent and the holes drilled out, epoxy it onto the plastic nut.
- Screw the assembly onto the fan chassis using four #4's screws.

Tripod Assembly Notes:
- If you've been working with plastic, you can make your metal base out of an aluminum soda can.
- I did try to forgo the metal base by gluing the plastic nut directly onto the fan base and although I tried several glues and epoxies none would stick to the fan material.

Step 6: Usage Review

After using this for some projects it is everything I needed, compact and powerful enough for small projects. It is rather loud it but can only really be used at full speed or it doesn't fully trap the maximum amount of fumes. However if you'll be soldering all day, day after day then a regular large fan would be a better choice.

Congratulations! Happy soldering!