Possible stupid question about SpeedFan and FanMate...

Mats · Post by **Mats** » Wed Dec 07, 2005 9:54 am

In short:

When FanMate at min (5 V), fan starts at 35 % in SpeedFan.
When FanMate at max (11 V), fan starts at 38 % in SpeedFan.

I expected something like the opposite?

Fan: Zalman CNPS7000A-AlCu

datapappan · Post by **datapappan** » Wed Dec 07, 2005 5:32 pm

No Q:s are stupid.

What is your real Q? In order to answer you have to explain more. I'm guessing you are controling the fan via SpeedFan, and also have the fan hooked up to a FanMate.

So what are the figures from SpeedFan? Usually you set up a minimum speed, which in turn translates in to a voltage on your MB:s fan header. Thus 34%=4,08V and 38%=4.56V.

OK I'm stumped here, please expand on your question, and I'll be back.

/ datapappan

Elixer · Post by **Elixer** » Wed Dec 07, 2005 6:27 pm

The zalman fanmate does weird things when it's fed less than 12V. It's not just a potentiometer, and has non-linear behavior. In my experience when its fed 5V it behaves opposite of what one would expect. On minimum at 5V it gives ~4.5V and at max it gives ~3V. Perhaps this explains what's happening to you.

dddibley · Post by **dddibley** » Wed Dec 07, 2005 9:34 pm

I'm testing with SpeedFan and figured it starts up as a percentage of the fan input voltage, regardless of what that voltage was. Doesn't mean the fan's turning at the same rate.. right ?

ddd

tjpark1111 · Post by **tjpark1111** » Wed Dec 07, 2005 9:38 pm

i have a question about fanmate/speedfan. Is it true that if I connect my fans to my mobo and control them with speedfan, it makes more buzzing noises and is more inconsistent than using a hardware fan controller like the fanmate?

dddibley · Post by **dddibley** » Wed Dec 07, 2005 9:51 pm

My CPU fan on SpeedFan whines at 100, 90, 80, 70. It's relatively quiet at 95, 85,75,65, Go figure. I use a rheostat on the pair of 120mm case fans and find the same thing, but not as much. Each fan is different. Depends mostly on fan quality I suspect.

ddd

Mats · Post by **Mats** » Thu Dec 08, 2005 8:00 am

Ok, for those who didn't understand...

The FanMate is set to min, and SpeedFan is set to 35%. The fan rotates slowly.

If I change the FanMate to max, the fan stops!!!

and if I lower the FanMate after that, the fan starts again.

Question: Isn't that strange?

I've tested it lots of times now, happens every time.

The experience from Elixer sounds like the same, but it's still strange. I don't know much about pulse width modulation,
but I'm thinking that the combination of using SpeedFan and FanMate makes a less optimal power output, which may be individual for different fans.
Just speculating. Will try another fan now.

Mats · Post by **Mats** » Thu Dec 08, 2005 8:24 am

Did a test with my AMD Opteron cooler. The fan starts at 47% no matter how the FanMate is set.

I know there are some settings in SpeedFan that can be adjusted, I haven't tried then all though.

Aleksi · Post by **Aleksi** » Thu Dec 08, 2005 8:30 am

Hi Mats,

I'm guessing it might have something to do with the minimun operating voltage of the fan mate and how it reacts when it doesn't get that. IIRC, the fan mate uses a LM7805 (5V regulator) with a trimmer to lift the ground reference point, so that the output is between 5-10,5V (The regulator input voltage has to be higher than 5V (6-6,5V ?) because it "eats" some of the voltage, at 12V it's ~10,5V.)

So even though it seems you're feeding the fan mate more voltage it actually might send less voltage to the fan. I'll play around with the figures and throw an theoretical example about the functionality of the LM7805 that isn't based on any measured or calculated figures ( disclaimer,

)

So at 12V * 0,35 = 4,2V (below the minimum operating voltage) for the fan mate the output could still be dropped by about 1V to 3,2V. Now, you start to decrease the input voltage and there most likely is a point where something inside the fan mate stops operating and just passes the voltage through. So maybe (wild speculative example) at 11V * 0,35 = 3,85 the voltage is suddenly let through and the fan actually gets 3,85V instead of the 3,2V at a "higher" setting.

I've seen this behaviour with LM7805, but never properly checked because it's outside the intended operating spec. AFAIK, it's more or less random.

Mats · Post by **Mats** » Thu Dec 08, 2005 8:44 am

Hej Aleksi!

That sounds interesting, and the best explanation I've heard so far, thanks!

I tried an Yate Loon D12SH-12, it also starts at the same number (49%) no matter how the FanMate is set.

Aleksi · Post by **Aleksi** » Thu Dec 08, 2005 8:59 am

tack tack och lycka till!

That's pretty much all the swedish I remember...

Apparently you don't a have digital multimer so you could check the real output voltage of the fan mate?

Motherboards fan headers can be pretty interesting. I'm currently fighting with my NF-7, it can't detect the Nexus RPM signal (tried all speeds and settings) but can detect the RPM from a Globe. Odd, AFAIK the tacho circuits in those fans should be quite similar, atleast I think the circuit at the motherboard is pretty standard (5V pull-up resistor).

The wonders of modern technology, go figure...

Schroinx · Post by **Schroinx** » Thu Dec 08, 2005 2:45 pm

[quote="Aleksi"]tack tack och lycka till!
quote]

hei dere

Please correct me if Im wrong here, but I belive that the mobo fan headers does not regulate by voltage, but by PWM duty cycle instead as this is so much easier to do with a chip, wheras voltageregulation would require a few more components. Since the fanmate contains electronic components as the 7805 voltage regulator it does not behave linearly with a low dc signal or a PWM signal and so you have your weird behavior. In case the fanmate has a capacitor in line, this should, depending on size of the capasitor and the PWM frequency flatten the ripple and make it behave almost as if it got dc.

Anyhow why would anyone connect a fanmate when using speedfan or the other way around?

Mats · Post by **Mats** » Thu Dec 08, 2005 3:24 pm

Schroinx wrote:Anyhow why would anyone connect a fanmate when using speedfan...

Good question...

Well, the reason why I did it was that I had a FanMate just lying here, so I might as well use it so I don't have to listen to the fan at 12 V before SpeedFan starts up. Not that important really.

Schroinx wrote:...or the other way around?

That's more obvious. I can go lower with SpeedFan than with FanMate.

Hmm, it all just sounds stupid right now. I'd better shut up!

Aleksi · Post by **Aleksi** » Thu Dec 08, 2005 10:49 pm

Hi Schroinx and Mats,

Schroinx, yep you're right. I guess most motherboards use PWM to control the fans, that's what I was pointing at with my calculations (35% in speedfan would be a PWM output with a 35% duty cycle) (this depends on your speedfan options, disclaimer

).

AFAIK, If you're using PWM to control a 7805 it doesn't matter if it stays above 7805 operating voltage, for example at 60% duty cycle (motherboards use the 12V line on the fan). But if you go below the operating voltage then it doesn't matter if it's linear DC voltage or a PWM signal, it acts funny with both. Maybe funnier with PWM at really low voltage.

I personally use fan mates with speedfan to set a top speed, because I've had to deal with some motherboards that only control fans properly within a setting of few percentage. This depends I guess on both the motherboard, speedfan options and the fan in guestion. And it's always nice not to have the fan spinning at 12V when you start the computer.

Tack och adjö!