In a 3-wire fan, the extra (third) wire is the ‘tachometer’ signal (Tacho) wire that indicates how fast the fan is running. The simplest PC fan requires just two wires – one wire provides power (12V), and the next wire is ground (0V). 3-pin connectors are usually used for the smaller chassis fans with lower power consumption, while 4-pin connectors are usually used by CPU fans with higher power consumption. Note that Chassis and CPU fans may use either 3-pin or 4-pin power connectors. Each of these wires serves a specific purpose. 4-wire fans explainedĪ 4-wire CPU (motherboard) fan is a standard brushless dc (BLDC) fan, but has four wires extending from the casing. Before we go ahead, we need to learn the technical aspects of a 4-wire fan. And while this post is primarily focused on its speed control, the cognition took on can be utilized later in certain power electronics projects. But first, I will put my attention entirely on the 4-wire fan. Now I’ve got the key part down, time to scale my basic idea up. Most surprisingly, that’s exactly what my first pick was! After breaking the security seal and opening the box, I quickly found one 4-wire Intel CPU fan on top. Naturally the first step was to open the carton to see the contents. Within a week the packet reached my doorstep. Since the computer hardware store had them on clearance, I managed to add all of them to my shopping cart! I reached the end of a lengthy search as I chanced upon a couple of useful PC CPU fans and PC Case fans.

For a while now, I’ve had need of one ‘over-the-top’ instrument cooling fan suitable for heavy use.

Case fan controller