This typical for using fans on the 633?


New member
I know when using the RPM sensors it kinda pulses for each reading of the sensor. I don't have sensor wires hooked up to my panaflos. Anyways when I bring the fan power down to like 60 % it's kidna like it's pulsing again.

The way I can only discribe it as uhmmm it kinda seems like the power to the fans is a digital signal ya know? 1-0-1-0-1-0 each 1 is when it pulses, the higher the power I give it the less it's noticeable when at full power there find...

When I plug the fans into the little fan bus Lian-Li installs on there cases, and I can control the speed of the fans it doesn't do that pulsing thing. It's a like an anolog signal. Nice smooth flow. Is this just the nature of how this Intelligent display controls the fan speed? I'm gonna go pick up some rubber gromets and see if maybe that disguises the noise.

Thanks for anymore help.
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CF Tech

If you can count the pulses then it is probably the RPM reporting that is turning the fan on for 1/8 second per 1/2 second in an attempt to read the speed. If you do not have the tach line connected, then it is not doing any good to attempt to read the RPM.

Using 633_Wintest, uncheck all the "RPM" boxes, and make sure none of the fans are set to display automatically to the LCD (as would be set with Command 21). Then the power output will be smooth.

Let me know if that does it.


New member
I did some testing with a multi meter and such. No I don't have an rpm sensor.... I did this with all my fans.... if you plug in set the speed to 100% then stop the fan with your hand, then decrease the fan speed to 99% or less... Feel that pulsing? Hold up to your ear.. Hear that pulsing? With some of my fans it's nothing at all.. But my Panaflo U1A's make a little tick.

Measure with a multimeter at about 9 volts where it's the worst and where I like to run my panaflo's at. I get a diffrence of about .15 volts.

At 100% and 0% voltages are 100% stable not diffrence at all. If I set the fan power to 1-99% the voltages aren't stable... Ranging anywhere from .02 to .15 voltage diffrence.

It might not bother other folks, but I built my computer around extreme quietness. My computer is water cooled, with an enermax whisper, and panaflo's. My harddrive is the loudest thing. Anyways the best I can describe the noise is it's kind of the tone of a harddrive access. Cept it's constant about 10 ticks a second.. To fast to count for me.

Maybe you can research this? Maybe a revision is in the future. And poor ole me can get a newer one? ;) :p

Right now I just have the fans plugged into the fan bus on my lian li, but I hate having to take the bezel to adjust my fan speeds. Plus it only has 3 settings. As with the 633 I have a 100 settings! :)


Are you sure that pulsing does happen at 100% when the fan is stopped? Some of the better brand fans detect when the fan has been forced to stop, and then tries to restart the fan every 1/2sec or so. This could be the pulses your talking about?

A multimeter isnt going to show what the 633 is doing correctly. The 633 uses PWM to slow the fan, not linear voltage control like the common rheostat fanbus setup.
The 633 supplies varying length pulses of 12V to the fan which a multimeter wont measure.

The only thing that should make the fan pulse is the measuring of the RPM, as said. So turn the RPM speed checks off, and all should be ok.
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CF Tech

The 633 uses a "PWM" (Pulse Width Modulation) to slow the fan down. What that means is that the fan is either "on" or "off", but the 633 switches between on and off quickly and then varies the ratio of on time to off time according to the power setting.

A simplified (10 step) version would look like this:

00000000000000000000 = 0%
10000000001000000000 = 10 %
11000000001100000000 = 20%
11100000001110000000 = 30%
. . .
11111111001111111100 = 80%
11111111101111111110 = 90%
11111111111111111111 = 100%

On the 633, that cycle repeats 18 times each second.

Choosing the frequency is always the big question on designing a PWM control. In a motor, it can get very complicated. Too high of a frequency can make the motor heat up too much. Too low can make the rotation rough.

I am pretty sure what you are hearing is mechanical noise from the fan's bearings as the torque from the fan's motor alternates between positive and negative every PWM cycle. We have some 92mm Delta FFB0912EHE fans here, and you can hear a slight ticking with then at certain power settings. Other fans are silent at all power settings except for the "wind noise".

Since it is a mechanical noise, you might try playing around with the mounting--different mounting methods may help dampen the sound.

Some of the reason for slowing down the fans is longevity, but mostly it is for noise. So the question is: Is the fan quieter overall at 50% power than at 100%?


New member
Ok thanks that really cleared things up. I'm gonna play around with some mounting methods to see if I can get it to stop. My Sunon fan, and my adda fans, you can't hear it at all unless you plant your ear right up to it. Like you said though I'm gonna put some rubber gromets inbetween where they mount and see how that does it. If not it's no biggie to use the front fan bus on my lian-li to control the front fans. Then I could just hook up my 120mm to it, I doubt you'd hear it with that thing.

Also would it be possible to control lights with it? I have a coupla cold cathodes on the way. I don't think I'd be able to run anything in between but at 100% it would be on, 0% off.

Thanks for all the help.

CF Tech

How noticeable is the noise with the worst fan? Can you give us a part number, and maybe a link to purchase one? Perhaps we can get one in and see how it is.

The "PWR" on a fan connector is alway connected to +12v. The "GND" is disconnected (if the fan is off) or connected to ground (if the fan is on).

It should be OK to drive 12v accessories up to 1A, but we have not tested it an would not guarantee it. You would need to make sure that no part of the accessory is "grounded", since it would just power though that path.


New member

It's probably not as bad as your thinking, when anyone thinks of noise on how I think of noise, it's usually nothing to them. But I'm not sure how your ears are on noise it may or may not bug you. All I know is I can hear something and I know what its coming from, to me when I'm acheiving almost total silence a ticking kinda like a rapid clock will bug me, or be another project for me to get that sound to stop.

Thanks again for all the help