This project will focus on using Arduino to build a smart fan controller. Fan controllers are an effective way to limit or boost the rotation speed of the cooling fans in a desktop computer. While doing something that is CPU and GPU intensive, it may be preferable to have more airflow through the computer case. Quite the opposite is true when there is little load on the CPU and GPU. Silence is golden when performance is not necessary. Typically, case fans are noisy and are connected directly to the 12 Volt power supply. This means the fans are on full strength whether it is needed or not. By limiting the effective voltage in certain situations, one can reduce the noise produced by the fans without affecting performance when needed. The primary objective here is to set a temperature threshold and have the case fans ramp up as needed to keep the case and components cool. To implement a reasonable system where the fans do not kick on and off, proportional-integral-derivative (PID) will be implemented. This feedback mechanism should make sure the fans stay quiet while providing adequate cooling in the computer case. The case fans in any desktop computer are controlled in one of two ways: either they are connected directly to a 12 volt branch of the power supply or they are controlled by the motherboard. Typically, at least the CPU heat-sink’s fan is controlled by the motherboard. The heat-sink’s fan is critical and is excluded from this project. The case fans move air through the chassis, providing cool air across all of the components. The RPM of each case fan is directly related to the voltage applied to the pins cased in their Molex connector. By regulating this voltage, the RPM of each fan can be controlled. By regulating the RPM of the fans, the noise can be reduced when needed. Head past the break for all the details.