Archived from groups: alt.comp.periphs.mainboard.asus (
More info?)
In article <urlt41l7upmano34p11sf364mj7ev06coc@4ax.com>,
miller.90@spamlessosu.edu wrote:
> I'd like to put a Thermalright XP 120 cooler on my new A8N-SLI, and
> I'd like to mate that with an ultraquiet Panaflo 120 fan.
> Unfortunately, this fan doesn't seem to have RPM monitoring, and I
> presume that the A8N-SLI wouldn't POST correctly without that
> capability.
> Can anyone give me a recommendation for an EXTREMELY quiet 120mm fan
> that DOES have RPM monitoring? (Money's no real object to get the
> quietest fan for this use.)
>
> Thanks,
>
> Ron
There are Panaflo fans mentioned on this page. But there are no
fans with the BX tachometer option offered in the 120mm catagory.
There is a 92mm fan with the BX option, but no 120mm.
http://dkc3.digikey.com/PDF/T051/1364.pdf
If you needed a ready-made cable assembly, to go with the cable-less
Panaflo fans, this company in Canada sells the proper cable for
$1.49 a piece.
http://www.bigfootcomputers.com/Merchant2/merchant.mv?Screen=CTGY&Store_Code=Bigfoot&Category_Code=700.1
Panasonic data on the fans is here:
http://www.motor.panasonic.co.jp/www-ctlg/ctlgj/qAJA1000_JP.html
Looking on Silentpcreview.com , the fans they used with the XP-120
all looked to be tacho-free fans. Perhaps reading all the reviews of
the XP-120 available on the web, will dig up a good candidate.
Another problem you might run into, is the minimum fan speed needed
to register with the Asus fan monitor. I don't know what the lower
RPM limit is on your motherboard, but on some of my older Asus boards
it is 1800 RPMs. A Zalman 7000 runs at about 2200 RPMs at 12V, and
registers nicely. If you are going for extremely low RPM settings,
like 600-700 RPMs, even if you find a fan that has a good working
RPM output, the BIOS or Asus Probe might not recognize it.
The best solution in this case, is not available commercially.
(At least I haven't been able to find one.) It is possible to
implement an optical tachometer, using a phototransistor or
photodiode. I have successfully used this approach on my
central air conditioner unit (outdoors), to measure the
RPMs of the A.C. fan, and verify the RPMs seen versus the
ratings stamped on the motor. (The motor in my A.C. is damaged.)
Using a Darlington pair (sensitive) version of a phototransistor,
I can hold the Darlington phototransistor about two inches away
from the spinning fan blade, and pick up an optically commutated
signal. My multimeter has a frequency input, and it managed to
detect the output of the phototransistor. The source of
illumination in this case, was a hand held flashlight. Light
bounces off the tips of the fan blades and is detected by the
transistor.
The beauty of the optical tachometer in this case, is you get
seven pulses per revolution when the fan has seven blades on it.
A standard brushless DC fan produces two pulses per revolution.
Thus, the optical approach will have a higher "apparent" RPM
reading, by a factor of 3.5 . That means a 600RPM fan will
measure 2100RPM in the BIOS.
I found a very nice device on Digikey, that would take most of
the guesswork out of detecting a spinning fan blade:
http://www.sharp.co.jp/products/device/lineup/data/pdf/datasheet/gp2a200l_j.pdf
On Digikey, it can be seen here - GP2A200LCS - $4.66 each:
http://www.digikey.com/scripts/DkSearch/dksus.dll?Detail?Ref=37469&Row=116221&Site=US
http://dkc3.digikey.com/PDF/T051/1432.pdf (catalog page)
This is how you would use it. The +12V and one GND signal go
to the fan, to power it. You can either pick up the power
here, or you could use the +12V and GND pins on the three
pin fan header. The Sharp module is powered from a +5V and
a GND wire on the disk drive connector. Then, all that remains
to be done, is connecting the Vo terminal of the Sharp module,
to the tacho pin on the motherboard fan header.
Disk drive power 12V ------------ +12V on fan
connector GND ------------ GND on fan
GND ------------ GND on GP2A200LCS
+5V ------------ Vcc on GP2A200LCS
GP2A200LCS Vo pin
----> to tacho pin
on mobo fan
header
The GP2A200LCS has an open collector output, while the motherboard
has a pullup resistor intended for an open collector drive. Vo
on the Sharp module is rated for 30 volts, while the motherboard
uses anywhere from 5V to 12V on the tachometer (sensing) pin.
The Sharp module can handle up to 50mA of current in its output
transistor, while a fan header places no more than 10mA on the
tachometer (sensing) pin.
Should be a slam-dunk to connect together, using wires scavenged
from a disk drive "Y" power cable, a fan wire off an old fan,
and the Sharp module.
To use the Sharp module, hold it 5 to 15mm from the tip of the
rotating fan blade. Don't glue it into place on the body of
the plastic fan, until you've verified the sensitivity. Once you
find the right angle of incidence, you fan make a permanent
mounting for it.
The Sharp module uses synchronous detection. What that means,
is the Sharp module has a LED inside it, that blinks at extremely
high speed. The light receiver channel "listens" for light at
that exact frequency, which means the light receiver will ignore
the 60Hz hum from room lighting. The only limitation to the
module, is if you shine so much ambient light on it, that the
phototransistor inside the Sharp module saturates. That would
not damage anything, but it would cause the RPM pulses to stop.
In terms of response time, the maximum "flash" rate would be
500 times per second, or roughly 71 rotations per second or
4260 real rotations per minute, which should be good enough
for your ~2000 RPM seven blade fans. At 4260 real RPM, the
BIOS would read 14900 RPM, due to the increased pulse rate.
Now you can select whatever Panaflo fan you want from Digikey
catalog page 1364, plus pick up a few of those Sharp detectors
from page 1432.
The Sharp module has a bypass capacitor inside, that filters
the power provided by the +5V and GND wires. If the Sharp
module shows any signs of instability, the datasheet says
to place a 0.33 uF (microfarad) capacitor across the supply.
You could use a 399-1866-1-ND $1.06 for this. It would go
from the VCC to the GND pin on the GP2A200LCS module.
http://www.digikey.com/scripts/DkSearch/dksus.dll?KeywordSearch
http://dkc3.digikey.com/PDF/T051/0955.pdf
You could also use a sloppier tolerance Z5U like 399-1885-1-ND
for $0.65 each.
Have fun,
Paul
68u419s54qelovaup01dppfpv28pr7007@4ax.com...
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