"A E" wrote in message
...
Andre wrote:


Silicon diodes in series allow small increments and an easier way to
select
the required speed.

Interesting idea - thanks

Except it does nothing more than a resistor, and a 0.6V drop at a supply
of 5V gives you 12%
increments, hardly small.
I'd stick with a resistor, or go the PWM way, that's the right way to do
it.


I don't think PWM is the right way to drive an electronic brushless motor,
unless the pwm waveform is converted to a dc level with a capacitor. PWM is
a great way to drive a brush motor, I don't think it would have a desirable
effect on a brushless one, it may even damage the circuitry in the fan.

Your claim that a diode does nothing more than a resistor is not true. It
provides a (approx) 0.6V drop without reducing the available current
significantly, not the same as a resistor at all. A resistor will have a far
greater effect on startup torque and running torque than a diode.

Anyway, the best way to control one of these brushless motors IMO is a LM317
or similar
regulator with a pot so the OP can set the exact speed he wants. Not the
simplest way but a sure way of getting the speed right.

Dave