[TriEmbed] laptop fan motor control question

[Shane Trent]

Not ALL brushless DC fans can be speed controlled via PWM, but the
presence of a tach lead is a good indicator that a fan can use PWM.
Sometime early last year I grabbed a fan at random from my parts bin (junk
drawer) to test a PWM output for a LEGO robot and thought the output
channel was not working (it was either on or off, no speed control). But it
turned out that BLDC fan just was not compatible with PWM.

On Tue, Feb 2, 2021 at 2:17 PM Carl Nobile via TriEmbed <
triembed at triembed.org> wrote:

> Jon, that all sounds very logical, and had I thought about it a little
> longer I would have realized that it wasn't a brushed motor, so I will
> withdraw my comment.
>
> All brushless DC motors are actually AC synchronous motors with
> electronics between the power and the motor that converts the DC into AC.
> It looks like Pete's motor is 5V DC, not 12V DC, however.
>
> On Tue, Feb 2, 2021 at 2:01 PM Jon Wolfe via TriEmbed <
> triembed at triembed.org> wrote:
>
>> yes, besides the electrical, and also audible noise, a brushed motor
>> would wear out its brushes. any motor that's intended to be on most or much
>> of the time, and have a long maintenance free service life, is going to be
>> brushless. Most fans used in pcs are going to be brushless running off 12v.
>> You can pwm the power supply to do speed control, its done all the time.
>>
>> On February 2, 2021 1:43:45 PM John Vaughters via TriEmbed <
>> triembed at triembed.org> wrote:
>>
>> Computer fans are almost always brush-less, actually never seen a brushed
>>> one. Because the electrical noise is too high. She 3 pin motors are simply
>>> two power pins plus one tachometer pin, which you generally only want to
>>> determine if the fan is failing. I could be wrong about this part, but I
>>> expect that they are single voltage and reducing the voltage may or may not
>>> affect the speed much and possibly could damage the fan over long use.
>>> However, I seem to remember some schemes to make 3 wire fans speed
>>> controlled. it's worth a look online I suppose.
>>>
>>> John Vaughters
>>>
>>>
>>>
>>>
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>
> --
>
> -------------------------------------------------------------------------------
> Carl J. Nobile (Software Engineer)
> carl.nobile at gmail.com
>
> -------------------------------------------------------------------------------
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-- 
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*Shane D Trent*
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