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How to reduce PWM fan noise?
PWM noise, as well as inductive kick, can be reduced or eliminated by slowing the slew rate of the PWM drive signal to the fan. Even a small reduction in slew rate results in a significant reduction of the PWM noise.
How do you stop a DC motor from making noise?
Capacitors are usually the most effective way to suppress motor noise, and as such we recommend you always solder at least one capacitor across your motor terminals. Typically you will want to use anywhere from one to three 0.1 µF ceramic capacitors, soldered as close to the motor casing as possible.
What causes the most acoustic noise in a PWM fan?
The most dominant source of acoustic fan noise is tur- bulent airflow, which is caused by fan operation at full speed. Employing fan speed control (where the fan is operated primarily at lower than full speed) minimizes this noise. The second most dominant acoustic noise is due to BDC fan’s torque characteristic.
How does PWM work on a PC fan?
In low power applications (including low power PC fans without speed control), commutation is done with a simple hall-effect circuit that detects the position of the spinning fan rotor and flips a switch (the transistor) to change the magnetic field. Many of these fans are two phase and do not have a PWM control option.
How can I reduce noise from my PWM fan?
PWM noise, as well as inductive kick, can be reduced or eliminated by slowing the slew rate of the PWM drive signal to the fan. Even a small reduction in slew rate results in a significant reduction of the PWM noise.
Is it OK to lower PWM to 31hz?
SAS is correct – lowering the PWM to 31Hz works great. Tested using a 12v fan. Before lowering the PWM, the sound from the fan was a loud “WHEEEEEeeeeeeeee” sound at any speed other than full speed. Low speed made the sound worse. After lowering the PWM frequency, the noise is inaudible at higher speeds.