Re: smart fans
On Sunday 22 August 2021 12:46:14 Polyna-Maude Racicot-Summerside wrote:
> On 2021-08-22 10:02 a.m., Emanuel Berg wrote:
> > tomas wrote:
> >> I disagree. The thing poses [1] as a DC motor (2 pins power,
> >> one tacho). I don't think you get too much control over RPM
> >
> > That's what you get with the 4th wire/pin? A sensor to
> > read RPM?
>
> Opposite
> 3 wire = 2 wire to drive motor + 1 wire to get speed
> 4 wire = 2 wire to drive, 1 to get speed, 1 to modify speed
>
I as a CET, am totally unimpressed with the miss-information being thrown
about in this thread. A total lack of how its actually done in real
hardware.
1. Any si diode, passing a few microamps of fwd current, is in fact an
excellent, does not need to be calibrated, thermometer capable of 1
degree C accuracy. There are several million candidates buried in
todays cpu's.
2, even a 2 wire fan can be controlled by using this voltage to determine
the on time of a small transistor. Often down to 1% speed at room tmps,
so other than the cost of the time at die bondout time, its free. The 1%
minimum is actually used to help distribute the motors lubricant.
3, boiled down, the temp measured by this diode can be scaled to control
the fan to maintain the device being monitored at a fixed maximum temp,
and its done on 2 or 3 of the gates on the cpu die intended to be used
to replace a bad gate in you cpu. Intelligently done at test and bondout
time, it might add 10 seconds to the time needed to verify the rest of
the chip.
> > "What you can't measure, you can't control"
Better, if you can measure it, you can control a 2 wite motor.
Cheers, Gene Heskett
--
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
If we desire respect for the law, we must first make the law respectable.
- Louis D. Brandeis
Genes Web page <http://geneslinuxbox.net:6309/gene>
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