Fan the Fumes

DIY Soldering Fume Extractor

Liam Davies

Issue 35, June 2020

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Clear nasty soldering fumes out of your work area with this handy fume extractor. It’s a great alternative to pricey commercial products and comes with a dimmable LED strip for lighting up the subject circuit board!


Hand soldering is by far one of the most common methods electronics enthusiasts use to construct their circuits. A maker may be reaching for their soldering iron daily to solder their circuit boards, wiring and connectors together. However, melting solder emits a variety of toxic fumes which you don’t want to be breathing in! The lead content in regular solder (60/40) is highly toxic, and as the solder melts, the flux within the solder combines with tin and lead on the surface. The oxides and other surface contaminants in the evaporating flux are what makes the fumes that you see. These solder fumes should be avoided; especially when inhaled over the long-term.

Lead-free solder doesn’t avoid this problem entirely either! There are many warnings by manufacturers of lead-free solder stating that inhaling it can cause irritation to the respiratory tract, leading to flu-like symptoms.


The purpose of a fume extractor - as you might have guessed – is to remove the harmful fumes from your immediate work area. Fume extractors usually consist of a fan, pulling the fumes from the area around the hot iron, and an activated carbon filter that prevents particulates re-entering the air after the extractor expels it.

So, why are we making this project then? Why can’t we just buy a commercial fume extractor? Unfortunately, makers prioritise buying other workbench equipment over a fume extractor. We will buy a new soldering iron, a new lab power supply, or a new multimeter before we even think about purchasing any safety equipment. This project is intended to show that making a basic fume extractor is fundamentally extremely simple and can be done inexpensively or even free if you already have the parts laying around the house! We’re adding some extra goodies to our version to make it even more convenient. Let’s get into it!


The core principle of our fume extractor is remarkably simple – it’s just a standard 120mm desktop computer case fan! What’s great about this is you may not even have to spend extra on finding one – you will have no trouble finding one in an old computer lying around. Or, if you prefer, you can find a specific fan that suits your needs. If you want utter silence while you solder, use a Hydrodynamic Silent case fan from Jaycar – we used one for our project. Alternatively, you could use a fan with integrated LED lighting to spice up your workstation.

Case Fan, available at Jaycar YX2574

It’s worth noting that because we aren’t spending as much as a commercial fume extractor, don’t expect it to work as well as one. Proper fume extractors are purposely designed to intake high volumes and filter it properly. Since ours is just a case fan designed to provide better airflow inside a desktop computer, there’s no way it’s going to be able to match up. High-quality fume extractors can extract about 60-80m3/hr, whilst ours will likely be able to extract only 30m3/hr. Nonetheless, considering we’re building it for the fraction of the price and adding some extra features, it’s pretty good value for money!


You can never get enough lighting on a workbench! Why not add some to our DIY fume extractor? We’re going to be using some cool white LED strips from Jaycar and driving them with the same 12V power supply our fan is using. These strips can be incredibly bright, and thus we’re going to be adding a dimmable driver circuit that will allow the brightness of the LEDs to be changed with the twist of a potentiometer knob.

We can dim these LEDs in several ways, but we’ve chosen to use a MOSFET with its gate controlled by the voltage of a potentiometer. We’ll discuss other ways you could drive these LEDs at the end of this section. Here’s a basic LED driver circuit with a MOSFET and a potentiometer.

Although this circuit will work, the MOSFET introduces a problem of its threshold voltage. That is, the voltage range of which the MOSFET begins to let current flow through its drain and source pins. The IRFZ44N’s datasheet states that its threshold voltage between Gate and Source is 2V-4V. As the voltage on the gate increases from 2V, the amount of current that can flow through the MOSFET increases until it reaches 4V, at which point the load (our LED strips) is essentially fully connected to ground. In other words, we theoretically need to use a voltage range between 2V and 4V to control our LEDs, 2V representing completely off, while 4V represents completely on. Once we go above this value, our MOSFET is saturated and our LEDs don’t get any brighter. The problem here is the voltage range we need to provide to our MOSFET gate is from about 2V to 4V, so the potentiometer needs to be connected in a voltage divider chain to give it the required range. So, when we connect this circuit and we turn the potentiometer knob, our strip will go from completely dark to full brightness over a very small fraction of its rotation – the rest of the potentiometer range is not utilised and will just keep our LEDs at full brightness.

Our brightness curve, if we turn the potentiometer from 0 degrees to its full 300 degrees, might look something like graph blue. Notice how quickly it changes from completely off to completely on? So, how do we make it look more like the other graph red?

We need to create a minimum and maximum voltage for the potentiometer to slide between in order to maximise the linear part of the graph. Thus, we need two resistors in series with the potentiometer so that we can create some extra voltage drop on either end of it. After experimenting with values, we found that a 42-45 resistor on the high side and a 6.8kΩ resistor on the low side works well (for the high side resistor, we used a 47kΩ resistor and a 300kΩ resistor in parallel, which calculates to about 40k).

This reliably turns off the LED strip completely when the potentiometer is all the way to the left and fully illuminates it when it’s fully turned right, with a satisfyingly linear range in the middle.

Alternatively, you could design a circuit to drive the LEDs with PWM control instead. This would make the brightness of the strip perfectly linear because the duty cycle of the PWM signal is directly proportional to the power provided to the LEDs.

Although you could drive it with the pin of an Arduino digital output, be aware that the PWM frequency of most Arduino chips is only 490Hz, which could lead to problems if you’re doing photography or filming projects under its light. To fix this, we need to use high-frequency PWM at or above 25KHz to guarantee no problems.

In Issue 1, we have a guide that shows you how to drive loads with a PWM signal generated from a standard 555 timer.

Changing the values of the resistors and capacitors to modify the frequency and varying the duty cycle using a potentiometer would make for very precise brightness control.

The Fundamental Build:

To get an idea for how our project will work, we’re going to build up a basic breadboard circuit. This circuit is virtually identical to the main build, so you can easily transfer components across the main build.


To begin, we tested our fan-controlling circuit that will operate from the green pushbutton switch we’re using. In this build, we’re using alligator clips to connect the switch’s terminals, which tends to get very cramped after more than two or three clips are connected at once on the switch – make sure to avoid any short-circuiting.

You’ll also need a 12V power supply for this. You can use a 12V power pack, or any lab bench power supply.

The back of the switch has eight pins, all of which are labelled, so make sure you get them right! The two pins opposite each other on the switch (labelled with ‘+’ and ‘-‘) are for control of the switch’s LED, which can be connected to 12V when we want to illuminate it. The other six pins are for connecting and disconnecting parts of our circuit when the switch’s button is depressed. Because this switch has a latching mechanism built in, it works a bit like a clicker ballpoint pen - one press to push it in and connect the contacts, and another to disconnect the contacts.

Parts Required:Jaycar
1 x DPDT LED Illuminated (Push on/ Push off)^SP0749
1 x 120mm Silent Hydrodynamic Bearing Case FanYX2574
1 x Cool White LED StripZD0570
1 x 12VDC Power Supply PlugMP3011
1 x 10K 16mm PotentiometerRP8510
1 x 10kΩ Resistor*RR0596
1 x 47kΩ Resistor*RR0612
1 x 6.8kΩ Resistor*RR0592
1 x 300kΩ Resistor*RR0631
1 x IRFZ44N N-Channnel MOSFET%ZT2466

* Quantity required, may only be sold in packs. A breadboard and prototyping hardware is also required. ^ Ensure that the switch you are purchasing has an LED intended to be powered from 12V, otherwise you may have to connect a resistor in series with it to limit current. # Not the same as described, but can be adapted with some customisation. % We used an IRFZ44N here, but any similar N-Channel MOSFET should work - although you may have to tweak the resistors for the potentiometer to get the most linear brightness curve for the LEDs.

* Note: We had a strange problem with this project, which involved the LEDs remaining slightly illuminated even when the potentiometer was turned all the way to the left. We attributed it to the MOSFET behaving unexpectedly on a breadboard. Thus, during the fundamental and main builds, you may notice a 10kΩ resistor added to both circuits. It eventually was determined to be unnecessary and doesn’t need to be added to your build of the project!

You’ll notice there are two columns of pins, with three rows each. Each column will always be disconnected from the other column, which is known as a “Dual-Pole” switch – meaning that you can control two circuits simultaneously while keeping them isolated! The three rows on the switch are for controlling which connections are closed and which are open. We’ll get into this more in the main build, but basically, this allows us to control which parts of the circuit are connected in each switch state.

For the fundamental build, we’re going to connect an alligator clip coming from ground to the switch marked ‘-’ and to the black wire on the fan cable – you can easily use a Dupont wire for this. Then, connect an alligator clip from 12V to the ‘C’ connection on the switch – this is the voltage we’ll be connecting the switch’s LED and the fan to when the switch is closed. From the ‘NO’ (Normally Closed) tab on the switch, connect an alligator clip to both the ‘+’ connection of the switch and the red wire on the fan.

While this might sound straightforward, the alligator clips tend to slip off the switch’s contacts and short out with others nearby. Take your time! To give the fan a quick test run, simply turn on the 12V power supply and check the fan powers up only when the switch’s button is pressed – the LED on the button should also illuminate.


Now we can get started on making our LED controller circuit. To start, we placed a 10kΩ potentiometer and an IRFZ44N MOSFET into the breadboard. They both should both be faced towards one long side of the breadboard. To make following along easier, we suggest placing them in the same orientation as these pictures.

Grab some jumper wire or some Dupont wires and connect the wiper of the potentiometer to the gate of the MOSFET (that’s the middle pin of the potentiometer to the right-most pin of the MOSFET when looking at the MOSFET from behind). You’ll also need to connect the left-most pin of the MOSFET to ground in order to sink the current we allow to flow through it, in order to light up the LEDs. As discussed in the How It Works section above, we’re adding some resistors with specific values to the outer pins of the potentiometer such that we can get a better voltage range for activating the MOSFET. We used 47kΩ, 300kΩ, and 6.8kΩ resistors in left-to-right order to set this range. You’ll notice the left-most pin has been connected with a 47kΩ and 300kΩ in parallel, which is effectively a resistor with around 41kΩ of resistance. Feel free to adjust these resistors if either your LED strip doesn’t light fully or won’t turn completely off.

Then, just connect a 12V line to your LED strips and the ground (-) connection to the MOSFET drain – the middle pin.

To test your prototype, plug it into 12V and give it a test run.

Note: Our prototype consumed around 200-250mA with the fan running and the LEDs at full brightness, and the MOSFET was running cool enough to not require a heatsink. The MOSFET acts as a resistor in series with our LED load, and so larger strips of LEDs would result in a higher MOSFET temperature and power loss due to heat.

The Main Build:

The main build for our fume extractor is identical “electronically” to the fundamental build. We’ll use the same MOSFET circuit and switching circuit for controlling our fan and LEDs, but we’re adding a custom 3D-printed enclosure to polish up our project! For that reason, the schematic and parts list are identical to the fundamental build, but with some added parts for cleaning up the wires.

ADDITIONAL Parts Required:Jaycar
120mm Fan Finger GuardYX2515
1 x Pack of 5 FiltersTS1581
1 x Panel Mount 2.1mm DC barrel jackPS0522
1 x Pack of 4 Rubber FeetHP0815
1 x Push-on Knob to suit PotentiometerHK7772
4.x 32mm M3 Steel Screws*HP0414
4 x M3 Nuts*HP0426
2.54mm Female Header Strips*HM3230
2.54mm Male Header Strips*HM3212
Mini Smartphone Tripod MountQC8099

* Quantity required, may only be sold in packs. Heatshrink and hook-up wire is also required.


Our circuit board is mainly to be used for routing power connections across the project, and to connect the MOSFET circuit to the potentiometer and LEDs. For that reason, we’re using a bunch of standard 2.54mm male and female headers to allow the different parts of the circuit to be quickly disconnected and reconnected. Also, keep in mind that this circuit is effectively exactly the same as the fundamental build, just with a slightly different layout!

Remember, you can use any piece of prototyping perfboard you have lying around – any piece about 2.5cm by 4cm will do the trick. We’ll start by soldering the headers that will connect to the various parts of the project. You’ll need three sets of 2-wide headers, and one 3-wide header. In the picture shown here, you can see how we’ve positioned them.

In clockwise order from top to bottom, the headers will be connected to:

  • Brightness-controlled output to the LED strips
  • 12V input from the DC jack
  • 12V output to the pushbutton for controlling the extractor fan
  • Potentiometer for MOSFET control

We’ve also shown the layout of the resistors we’re using for the potentiometer. From left to right, we’re using resistors 6.8kΩ, 47kΩ, and 300kΩ. One end of the two resistors can be soldered underneath the board to the rightmost pin header, and the other resistor can be soldered to the leftmost pin header.

After that’s done, go ahead and add the MOSFET to the circuit! The left-most pin of the MOSFET needs to be connected to the middle pin of the 3-wide header. This is the output from the potentiometer, and since it is connected to the gate pin of our MOSFET, this is how our LEDs will be controlled!

Note: As mentioned in the fundamental build, we also added a 10kΩ between the gate of the MOSFET and ground to prevent the MOSFET from floating and turning on the LEDs randomly. This resistor is optional.

From this point, it’s a matter of connecting the other headers to the circuit with hookup or solid-core wire. It’s worth noting that the MOSFET’s header is acting as a current sink, so one side of the LED header needs to be connected to 12V, and the other side to the drain of the MOSFET. How you run wiring for this project is down to preference, but as long as you follow the schematic provided, the circuit should work just fine.

After the circuit board is completed, it’s time to start adding wires to the components we’re connecting to it! We started with the potentiometer.

We soldered three wires onto each of its legs and covered each one with heatshrink, after which we soldered a 3-wide male header onto the other end. Heatshrink needs to be added to both the individual wires and the entire bundle to prevent short-circuiting or undue stress on the cable.

To prepare the 12V barrel jack, we first identified which legs of the jack are connected to which voltage rail. This can be done by simply plugging it into a 12V power pack and using a multimeter to determine which solder tabs are connected to 12V and ground. Then, a red and black wire can be soldered to 12V and ground respectively. Like the potentiometer, we will also add a two-pin male header to provide power to our circuit board. Make sure to add heatshrink!

Alright, we’re getting there! We next need to solder the wires for our LED strip. This is virtually the same process as for the 12V jack – just connect a red and black wire to the 12V and Ground tabs on the LED strip. This wire needs to be long enough to comfortably reach the top of the fume extractor enclosure - we found about 20-25cm works well.

The LED dimming feature of our circuit should now be ready to test. Connect the 12V power pack to the barrel jack and insert all of the headers into the circuit board – with the correct polarity! With the potentiometer turned all the way left, the LED strip should be completely off, and with it turned all the way to the right, it should be completely on.


The pushbutton is another bit of fancy wiring to control the extractor fan. This is pretty much the same wiring as the fundamental build, but without the bulky alligator clips!

As a quick note before we start soldering, make sure to keep your solder connections tidy – not only to prevent short-circuiting or any unwanted connections, but also because the switch’s tabs and the wires connected to them must be able to fit through the 16mm hole when we insert it into the 3D-printed enclosure. To begin, solder a longer red wire to one pole of the switch – it should be labelled as ‘C’ for Common. This red wire will eventually need to be soldered to a two-pin header that connects to the circuit board we made earlier. Then, you’ll need to solder one wire from the ‘NO’ (Normally Open) tab to the ‘+’ tab on the switch. Remember to double-check which connection you are soldering it too! This will connect the normally open connection to the anode of the internal LED behind the switch’s button. Don’t worry, the switch has an internal resistor which means it’s fine to connect it directly to 12V. From this tab marked "+", add another longer red wire. This will run to the positive connection of the fan, which will turn on the fan when the button is latched.

Note: If you prefer, you can instead connect a wire from ‘NC’ (Normally Closed) to the positive anode of the LED and connect a wire from ‘NO’ (Normally Open) directly to the fan. This will invert the behaviour of the button such that the LED will only turn on when the fan is NOT running. This could be useful if you have a dark workstation and you need to quickly find the power button for your fume extractor!

From this point, solder two black wires to the switch's tab marked "-". These wires will be the ground connection of our fan and switch.

To add the headers to our switch, solder the original red wire, and one of the black wires to a two-wide male header – again, remember to add heatshrink!

The other two loose red and black wires – you guessed it – can be soldered to another male header, unless you prefer to directly connect it to the fan’s wires. Simply cut the 3-pin fan connector cable and solder its red and black wires to the output of our switch. The other wire can be terminated with some electrical tape to avoid short-circuiting – we don’t need it right now. We’ll talk about how this wire could be useful at the end of this project!

We didn’t end up cutting the fan’s wires because we would prefer to be able to easily swap it out later with another fan. Luckily, the fan’s connector has the same 2.54mm spacing the male headers have, so we can directly connect the fan header to the fan supply socket.

The header connected to the switch's tabs marked "C" and "-" is our 12V input, which can be plugged into the original circuit board. Before powering up the circuit, do a quick test with a multimeter to ensure there are no short-circuits – especially between 12V and ground. Do a double-check to make sure all the headers on the circuit board are inserted with the correct polarity.

The circuit should now be ready for a test run! Simply plug the 12V power pack into the barrel jack adapter and both the LED strip and the extractor fan should turn on.


After building the electronics for this project, we observed the switch’s LED flickering for a short time after we turned off the fan. This is most likely due to the motor effects of the spinning fan. A little bit of physics here – buckle up!

According to Lenz’s law, a motor's coil will always oppose the change in magnetic flux (i.e. the magnetic fields “flowing” through the motor coils) that caused it, in this case, the voltage we’re applying to it. This is why the fan takes a little while to spin up because it tries to stop the inrush current we provide it.

When the fan reaches its designed rotation speed, the magnetic fields within its motor are built up, and are maintained by the continuous voltage we apply to it. However, when we suddenly disconnect the power to the motor (with the switch), the built-up magnetic fields try to maintain the voltage provided by our circuit. (The inertia of the rotating fan blades may also contribute).

It does this by providing a sudden pulse of EMF (electromotive force) which is able to light up the button in our LED for a short amount of time. In a nutshell, our fan is acting as a generator!

Fortunately, this isn’t much of a problem in this circuit because neither the Back-EMF nor the generator characteristics of our fan are unlikely to damage our LED. However, if we had more sensitive electronics like a driver circuit involving a transistor, it could instantly kill it from the reverse voltage.

To fix this, a “flyback” diode can be used in parallel with the motor – facing the opposite direction to the positive voltage. This causes the Back-EMF emanating from the motor to discharge itself with the diode and avoids a surge of current through anything else.


This project would be just a mess of wires across the workbench if we didn’t add a 3D-printed enclosure! The 3D models we made consist of four parts: the rear base, the faceplate, the lower wiring enclosure, and the mounting for the unit. You can find the 3D print files for this project on our website.

We printed the faceplate and lower wiring enclosure in lime green PLA on our Flashforge Finder, with a build space of just 140mm in every dimension! We purposely designed all parts in the project to fit in this space for those who don’t have access to a printer with a gigantic print bed.

To contrast with the lime-green parts, we printed the rear enclosure and action-camera mount with black plastic. That’s right, we added an action camera mount to the project! We figured many readers would have this fairly common method of attaching cameras to tripods and thus we designed a 3D-printed part that easily attaches to the bottom of the project with two M3 screws. We used a small phone tripod from Jaycar, which includes both a quarter-inch screw thread (for standard camera mounts) and a screw thread to action camera adapter – perfect for our project. You can use any stand which has this mounting method, so a flexible tripod works great too for precisely positioning the fume extractor to aim towards your circuit.

Depending on the tolerance of your 3D printer, you may have to grab a hand drill and enlarge some holes if some parts don’t fit through the designated mounting cutouts.


Let’s put it all together! We recommend starting with the lower enclosure since there are some fairly compact electronics we need to jam into it. To begin, we started with the potentiometer and on/off button. When slotting them into the enclosure, be sure to tighten down on the holding nuts to prevent the potentiometer or button from rotating. You should be able to apply a strong torque to the knob of the potentiometer at one of its limits and, if it’s tightened properly, it shouldn’t rotate at all. This process can be repeated for the DC power jack at the rear of the case. Make sure anything won’t come loose, otherwise you’ll have to disassemble everything in order to re-mount a lost part within the case!

To mount the circuit board, grab some double-sided tape (or any other non-conductive mounting solution) and stick it to the bottom of the lower enclosure. You may need to snap off a chunk of the circuit board to make it fit.

At this point, it’s a good idea to connect the headers from the button, fan, and potentiometer to make sure the headers will fit into the vertical space of the lower enclosure. We also gave it a quick test to see how it would look before it’s all assembled.

To continue with the assembly, screw the 120mm fan and finger guard onto the green front panel with some M3 screws if you haven’t done so already. We used some 25mm screws for this, which didn’t actually reach the rear of the fan, so we had to secure it with some M3 nuts to the front mounting square of the fan.

This is where the assembly gets a little tricky because mounting screws that secure the top black enclosure to the bottom green enclosure are quite hard to reach. To begin, sit the black enclosure on top of the green enclosure and slot two 25mm screws into the rear holes for each side. We only ended up using two screws for this because they become difficult to reach after we insert the fan. Using a pair of pliers, hold a M3 nut and use a small screwdriver to tighten the nuts onto the bottom of the screw. Beware, the nut gets quite hard to reach with pliers once it is held just underneath the ledge of the bottom enclosure!

At this point, you can insert the front panel with the fan attached after ensuring all wires are connected. You may need to leave the screws we just added slightly loose to allow the fan to fit. Once the fan is inserted, it should fit comfortably behind the bottom lip of the enclosure, which should hold it in place. Then, slot two M3 screws into the light bar at the top of the front panel and secure it with nuts.

Now comes the hard part – we need to tighten down the screws we loosened before inserting the fan. We found that a flexible or small screwdriver works best for this. The clearance between the rear enclosure and the fan is so slim, you’ll need to do some fine screwdriver positioning until you can get a hold on the screw.


Now it’s time to wrap the project up! To insert the carbon filter, we first need to trim it to size. Cutting it slightly bigger than the size of the fan itself helps it stay put – about 123-125mm in both dimensions work well. Then, insert each corner individually into the rear of the fume extractor until the whole filter slips inside. Oh, and finally, don’t forget to stick the LED strip onto the front of the project!


Like the fundamental build, testing the final build is just a matter of plugging it in and turning it on. We’ve already tested our build partially throughout putting it together so there shouldn’t be any major issues. If the project doesn’t behave as expected, make sure that you have the internal headers around the right way and the button is wired correctly – a multimeter will make sure that the voltages are in the correct place when required.

We placed the extractor about 15-20cm away from a test soldering project and found it works great! If the solder fumes are visually being wicked away from the subject circuit board and pulled through the fan blades, everything is working as it should be. Keep in mind that having this project on your bench isn’t an excuse for having poor ventilation – you shouldn’t be in an enclosed room with soldering fumes anyway. Remember to replace the carbon filter in the extractor when the airflow begins to be affected by dust and particulates clogging it up.


There’s a huge variety of other features you could add to this project to really make it unique.

To save some energy, why not make the fume extractor only turn on when your soldering iron does? If you’ve made your own soldering station or have easy access to its status through a signal cable, you could automatically enable the fan when it turns on. A handy feature that would make sure you only run the fan when you need it!

What about some other workshop tools and gadgets built into the enclosure? We’ve provided the STLs in the project files which can be modified to add extra accessories. You could add a solder reel holder to the front of the enclosure for quick access to solder, or a small tool rack for holding smaller tools like screwdrivers or side cutters.

If you really want to over-engineer this project, you could add internet connectivity or smart home connection with an ESP8266 WiFi chip to the wiring enclosure, to control both the extractor fan and LEDs. Why? Because “Hey Google, get my workshop ready!” is possibly one of the coolest-sounding voice commands we can think of. We would also not be surprised if it ends up as the world’s first smart-home connected fume extractor. Bear in mind though that the ESP8266 runs on 3.3V instead of 12V, so you’ll need to add some additional voltage regulation and LED control circuitry.

We would love to see what other features you can add to a normally un-assuming piece of makerspace safety gear! Tag us on our social channel, @diyodemag

Liam Davies

Liam Davies

18-year old high school student