How PC Fans Work - PCB Heaven A very common type of PC fan. These fans introduced the "tacho" for the first time. The first two wires are the power supply of the fan. The third wire, comes directly from the output of the Hall sensor output generates 2 pulses per one revolution of a fan. (#0033) 4-Wire Computer Fan Tutorial - YouTube Click to view6:25Used 4-wire fan for these two projects: 4-Wire Computer Fan Tutorial Eric Wasatonic. Loading PC fan BLDC driver circuit reverse engineered - Duration:Author: Eric WasatonicViews: 186K Motherboard (CPU) 3 Pin Fan Connector · AllPinouts Fans and on-board fan headers are backwards compatible. Proper fan connector placement is shown in the figures below: Fan has a 3-pin power connector; desktop board has a 4-pin fan header: Note: when using a 3-pin power connector with a 4-pin fan header, the fan will always be on; there is no fan control. PC Fan Controller Circuit - Electronics Hub Working of PC Fan Controller Circuit. In a normal PC or notebook PC, most of the heat generated is by the processor. This heat must be removed efficiently and quietly. A PC Fan along with a heat sink is an excellent active cooling system for computers. Most modern motherboards include a provision for on board CPU fan control. PC Fan Controller circuit – Circuit Wiring Diagrams PC Fan Controller Circuit Diagram. Place the temperature sensor in the warm air of the fan. When the PC is connected the speed rotation of the fan will be pretty high because of C1 but will decrease at a minimum value. Measure with a thermometer the air temperature close to the sensor.