Re: screen flicker: probably not X related

On Monday 28 February 2005 03:31 pm, Rick Miles wrote:

> I do not understand what you mean "AC driven electromagnets". While I have
> AC into power supply (so maybe PS fan is AC) the three other fans the fan
> on the nvidia card draws power off card which is DC and the two cooling
> fans draw power off mobo which is DC
>

The brushless DC motors that drive these fans are actually a synchronous AC 
motor. The rotating part inside the motor has a permanent magnet in it. The 
stationary coils are fed with AC that is generated by a small oscillator 
located inside the motor assembly.

The multi speed fans are similar in their construction, except the oscillator 
circuit is a bit different.

The oscillator circuit draws it's power from the DC supply as you have said, 
however the function of this circuit is to convert the DC into AC to produce 
alternating magnetic poles in the motor stator coils and thus make the 
rotating permanent magnet move.

Pip