Speed controlled fume extractor

thingiverse

Here's a fume extractor case designed specifically for a 120mm fan. The case supports fans with four wires, but you can also use three-wire fans. The only difference is that three-wire fans lack the PWM control line, resulting in no speed control. I found it beneficial to limit the speed of a fan rated at 1.5A. The control schematic for this project can be found on circuitdigest.com/electronic-circuits/555-timer-pwm-generator-circuit/. If I were to modify the circuit, I would add a capacitor between the pin 3 output and ground. I'm using a 20k potentiometer that I salvaged from an old device and a knob found on thingiverse.com/thing:2232447. The PWM frequency of this circuit was over 100khz if my memory serves me right. Unfortunately, I damaged a previous prototype case, so these renders will have to suffice until I can reprint the final version. The circuit was built onto a small piece of perf board using the legs of a ceramic capacitor as jumpers. Please ensure that all connections are made before trimming any component leads. I used 12v switches with LED indicators, which are commonly available on eBay. You can also find 555 timers in quantity for a few dollars. To minimize noise, avoid using giant rectifier diodes like I did and opt for fast-switching diodes instead. Schottky diodes would be an excellent choice if you have them. The hole in the case is 7 mm with a corresponding hole next to it for the potentiometer index nub. The picture of the board should provide a clear reference point for its size. I left enough space for a connector if desired, and instead ran a pair of wires out the side to connect to my lab supply. If you have any questions or need further clarification, please don't hesitate to ask.