Simple Air Purifier: 4090 Graphics Card Fan + Phicomm Wujin A1 Filter

Following the acquisition of a 3D printer, and mindful of its potential respiratory health implications, I embarked on a DIY air purifier project. Existing online designs proved somewhat cumbersome, prompting the pursuit of a minimalist aesthetic—a purifier seamlessly integrating its fan within the filter, avoiding any unsightly protrusions. Thus began my DIY journey.

Guided by the principles of cost-effective DIY, I opted for a FiberHome Wujin A1 filter (activated carbon + HEPA, readily available online for under $40) paired with a 4090 reference card fan (positive rotation) (two for $20 including postage via secondhand marketplaces). At maximum speed, the filter's periphery effortlessly adheres to a paper napkin!!

Xiaomi filters were eschewed due to their higher cost and the questionable quality of third-party alternatives. FiberHome's legacy filters, however, remain surprisingly accessible, boasting affordability and robust quality;

The 4090 graphics card fan was selected for its exceptional dynamic balance, commendable airflow and pressure, low noise profile, Nidec 12-pole motor, suitability for the filter's central outlet, and remarkably low price point of just $10 apiece.

The files encompass a top cover and a bottom cover. The bottom cover seals the base intake to prevent air leakage; the top cover facilitates outflow. To minimize noise impact, the framework utilizes only two legs; however, the fan's superior dynamic balance ensures vibration remains imperceptible during operation. The top cover features a small, flat opening (for fan cable routing) and one or two screw holes (to secure the adapter board).

Required additional components:

6 x M2x5 screws;

0.5mm-8pin ribbon cable adapter board;

12V PWM fan speed controller;

Assorted wires;

Soldering iron;

A 12V DC 5.5mm power adapter (a DC 5.5mm router power supply, 12V1A, is suitable);

A DC 5.5mm connector (optional, depending on your preferred power delivery method and interface);

A 4-pin fan extension cable (optional, direct soldering is also feasible)

Installation Guide:

1. As illustrated, route the fan's cable through the small, flat opening and secure it using four screws. Cease tightening when slight resistance is felt to avoid cross-threading.

2. Secure the fan cable to the adapter board, then affix the adapter board to the cover using screws.

3. Connect the adapter board's pins 2 or 3 (P1/P2) to the positive terminal, pins 5 or 7 (P4/P6) to the negative terminal, pin 4 (P3) to PWM, and leave pin 6 (P5), designated FG (likely for closed-loop speed control), unconnected.

Postscript:

The fan cable is actually 6-pin, but with an 8-pin width. A readily available 6-pin ribbon cable adapter may be used by trimming the two small tabs from the cable;

Considering the varying shrinkage rates of different materials and potential minor dimensional discrepancies between filter batches, the bottom cover is designed 0.2mm smaller than the filter's central hole. A napkin folded two or three times and inserted into the bottom cover's side wall provides secure retention;

The top cover's metal framework, extended by 1-2mm due to the fan cable, provides a secure and non-restrictive fit;

Given the diverse range of PWM controllers, no holes are provided on the cover. Users may add additional components or drill holes as needed; use screws no longer than 5mm.