How to build a fume extractor for your electronics workbench using an old PC power supply.
Fume Extractor from a PC Power Supply
If you are an electronics hobbyist like myself, you should know that one of the "dangers of the profession" are the toxic fumes from soldering components on a board. It helps to have a well ventilated area and even using a fan to blow the smoke away from you. In some occasions however, having a "fume extractor" can help. Commercial versions like this one from Amazon.com are about $60 as of this writing but you can build one yourself as I'll explain in this article. The bonus in this build is that it doubles as a soldering work light!
My fume extractor
Figure 1 shows my final implementation. It uses two main components I already owned: a halogen desk lamp and an old (broken) PC power supply. The idea is quite simple. Since this PC supply was broken, I removed all the insides from the box and left only the 12V fan. This fan works as the fume extractor for this project as it is designed to "suck" air into the supply when in normal operation.
As depicted in Figure 2, I took advantage of the fact that these halogen lamps already have a pretty hefty step-down transformer inside which I used to power the fan through the cable shown on the left. You will also have to add a bridge rectifier inside the base to convert the transformer's AC output into DC. It's my understanding that most of these lamps run on AC voltage so you should verify this before proceeding with any modifications. make sure also that the resulting voltage doesn't exceed the fan's capabilities. It's ok in my experience to drive these 12V fans at 15 to 16V (they will spin faster which is actually an advantage for this application) but pushing it beyond this might damage the fan and will likely reduce their life span. For convenience, I also added a switch in series with the fan so I could turn on the lamp and fan independently.
To provide a path for the fumes, I had to drill "exhaust holes" in the back of the PC supply box as shown in Figure 3. As a finishing touch, I spray-painted the box in black to match the lamp. The box was attached to the lamp with black plastic zip-ties.
Once you remove all the power-supply circuitry from the box, you are left with plenty of room to add a smoke filter. This is typically a carbon filter supposed to capture some of the bad chemicals in the soldering fumes. I did some research online and found that some of the filters used in Aquariums can also be used for this purpose. Fortunately, these come in different sizes and I was able to find one that fit my box almost perfectly (see Figure 4). Filters like this can be found at most pet stores. Later I also found this product in Amazon.com that seems was design specifically for this purpose, so it may be even better.
This setup has been working quite well in my workbench for over a year now. There are definitely many ways to do this and you may also consider repurposing the fan in a broken space heater for a similar purpose. Just keep working safely, and stay away from the smoke!
Comments, questions, suggestions? You can reach me at: contact (at sign) paulorenato (dot) com