Re: ATM DC cooling fans wiring question

[Leftfieldstar@aol.com]

 To all,

 A few months back there was much discussion about controlling fan speed and 
what circuits would work. I launched into a series of breadboarding projects 
to get a sense of what circuits worked best with brushless DC motors.
 The use of a MOSFET proved to be the simplest approach driven by a pulse 
width modulated circuit. The cookbook PWM circuits you will find thru 
websearches all switch at too slow of a rate to smoothly vary the power to 
the fan motor. However, if you raise the PWM rate to ~40 to 50 Khz switching 
rate, you can easily vary the speed of the motor without any of the noise 
artifacts and stumbling encountered at the typically slower switching rates 
that most of these circuits found in cookbooks use. The basic circuit also 
makes an ideal power controller for use as a heater for dew prevention on 
your diagonal.
 Anybody wanting further assistance, contact me off list.

It's a rainy day in Maine,
Dominic DiLeo