I've built a ventilation box which utilizes a blower motor from an old Subaru Impreza 1996, which I was gifted from a friendly mechanic.
The flow volume is amazing, but it's a bit too noisy and too powerful. The motor draws about 20A peak on start, and then operates at 7A at 12V.
But when using PWM, the motor basically sounds like a screaming alien, no matter if the duty cycle is 90% or 10%. I'm using Arduino to send a pwm signal and an IRF3205 MOSFET.
I've tried a low frequency (using delay and delayMicroseconds, 10-1000 Hz), and high frequency (using 32bit and 8bit prescaler of Atmega328). It only changed the pitch of the sound, but it was still very audible. The least noisy was at the low frequency, but then the motor was unstable.
Should I use a capacitor or an inductor? (or both). I haven't worked with inductors before. And I imagine the capacitor won't do much good...
digitalWrite(pin11, LOW); delayMicroseconds(50); digitalWrite(pin11, HIGH); delayMicroseconds(100);