The 4-Wire PWM controllers can read the speed of the fan and send a signal to the MOSFET controlling the fan's coils. At minimum this must be resolved by implementing a flyback diode. However, since fans store charge in a magnetic field, every time the fan is cycled off, the coils release a surge of current that can damage the internal and external circuits. This type of controller can also be used to manipulate other electronics such as LEDs, efficiently lowering or raising the brightness. 2-Wire PWM (Power Switching)Īny 2-Wire fan can be be crudely controlled by a 2-Wire PWM controller that cycles the power to the fan on and off to adjust the output fan speed.

PWM adjusts the fan speeds up or down, depending on the duty cycle of the input signal. The simplest method of lowering the fan speed involves reducing the voltage delivered, but this results in power loss and is limited on the range of speed control.ĭirect current fans, both 2-Wire and 4-Wire, can be driven by Pulse Width Modulation (PWM). There comes the time when it is necessary to control the speed of DC fans to reduce the power consumption and prevent the fans from being excessively loud.

Pwm fan control