I'm trying to control a 12V PC fan using a PWM signal from my Arduino, and mostly this is working okay using a fairly 'naive' pwm-driven transistor setup.
This has a couple of problems though. First of all, the fan runs a little noisier than usual, and secondly the tacho signal back from the fan is incorrect, which I think is due to the loss of power every time the PWM signal is low.
I have read (although I can't find the info now) that smoothing the PWM signal should help with these issues.
Is this the correct layout for a simple low-pass filter? I'm not sure about the correct values for R1 and C1. Is a low-pass filter even what I really need?