I've decided to investigate controlling the RGB LEDs embedded in aesthetics-based PC accessories. I'm not interested in using them for my PC, but as research for a yet to be determined future electronics project. I wanted something that is a standardized commodity with a large range of variety in the ecosystem and have some usefulness beyond just looking shiny. I settled on 120mm PC cooling fans.

There are many common sizes for cooling fans, but I've found 120mm to be the most common for aftermarket cooling. They're larger than average for CPU cooling, but not too large especially for heat-pipe based cooling towers. But they're typically installed for general cooling in tower cases, whose cooling vents are cut for 120mm fans. Covering both popular use cases mean more options.

Looking around on my NewEgg, I find that fans sold individually typically have two separate connectors. One for LED and one for fan control. To the rest of the computer, these fans look like two separate peripherals: the LED and the fan. They just happened to coexist in the same device. The fan control connector sometimes just have two wires for +12V and ground. Some have a third tachometer wire for reporting speed, and some have a fourth wire for built-in PWM control. Here's an example of a CPU cooler the Vetroo V5 whose fan has two connectors: a 4-pin CPU cooler fan control connector and a JRAINBOW RGB LED plug. These should be simple and straightforward to interface.

More challenging are fans that use an intermediate hub. The hub has a connector for power and for JRAINBOW, consolidating those signals into a proprietary connector. I started contemplating this particular Rosewill RGBF-S12001 three-pack of fans which use such a design. I think I can decipher roles of each wire so I could bypass the hub and control each fan directly. This multipack also had a remote control for direct control of the hub without a computer. This is appealing to me, because independent control meant I didn't need a PC involved as I probed how it worked. If I should make a fatal mistake (say, accidentally short-circuited something) it should only kill the hub or the fan and not an entire computer.

As I scrolled down, though, Newegg showed me several other items under "similar products". I saw an even more discounted three-pack of fans: the Asiahorse Magic-i 120 V2. Three fans for fourteen bucks, well within my impulse buy range. I'll buy the pack and see what it does.