the most problematic thing about PWM controller circuit is the switching ON/OFF noise on the fan itself.....it is so annoying not that it is loud

go low frequency and you will hear a low "woshh" sound....

go high frequency and it will sound like mosquito flying pass your ear.....

either way 5/12V or voltage regulators are the best option for me.......

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Added on April 9, 2007, 11:12 pmas for me, i would either hunt for a good fan which can take varying voltages with minimal motor noise or comes with the fan speed control feature.....

so far, i've tested that only SUNON 92mm has got the nicest range all the way from low voltage to 5k rpm, i mean that the step rpm is smallest that i've ever tested

anyway as i said earlier, PWM is a good controller assuming that you can take the buzzing sound from the motor itself.....if you cant then i suggest that you dont waste your time on it......

This post has been edited by AllnGap: Apr 9 2007, 11:12 PM