Help make a high speed fan near silent(sometimes)

[zbarnes]

I am looking for two 120mm fans to cool my dual '77 Bonne heatercore.

I have a nifty fan control thing for the thermaltake volcano cpu fan that fits in an empty floppy drive bay:

http://www.newegg.com/app/Showimage...-106-038-07.jpg (the thing on the right)

You guys think I could use it to make a rheostat for 2 12v fans, probably using a transistor? (I have some electrical circuits knowledge, but plain english is my favorite way of learning)

My second question:

Model- Delta AFB1212VHE
Dimensions- 120 X 120 X 38mm
Rated Voltage- 12 VDC
Operating Voltage Range- 4.0-13.2 VDC
Rated Current- 0.6 Amp
Rated Input Power- 7.2 Watt
Speed- 3200 RPM
Max Air Flow- 129.96 CFM
Max Air Pressure- 0.420 IN H2O
Noise- 48 dB-A

I know probably no one knows, but can anyone educatedly guess if these fans could be set so low on the voltage using a homemade rheostat that the noise would drop to the 20's dbA(albiet 30's probably more practical)? Would it still keep my computer from burning up at that low of a speed?

I want to have some super high air flow when things are hot, but then at night keep my computer running near silent.

Maybe this is more trouble than just getting some panaflo m1a's, but I can get those deltas $4 shipped! Would the performance be good, or no?

Any ideas?

[noxqzs]

It would be much simpler to put a potentiometer, within the circuit. With this, you could manually adjust the speed of the fan, by limiting current rather than voltage.

This can be bought at any local electronics store, such as a RadioShack and such for a couple of dollars.

basically find a potentiometer rated at 7 or more Watts, and wire it into the positive lead in series. by adjusting the POT, you will adjust resistance in circuit. the higher resistence, the lower the current, resulting in a slower/quieter fan.

[zbarnes]

Ok, so I should use something to vary the current?

I have a better chance at having a quiet fan than if I go with varying the voltage?

How do most variable speed fans do it? Do they use a potentiometer in line with the power?

[Sneaky]

current = voltage (same thing)


you proabaly want a vantec nexus 205

such as this (black): http://www.newegg.com/app/ViewProductDesc.asp?description=13-999-504&depa=0

or this (silver): http://www.newegg.com/app/ViewProductDesc.asp?description=13-999-505&depa=0

[noxqzs]

some variable fans, have thermocouples. the resistance of these devices is affected by temperature.

varying voltage or current depends on application, but in yours, its the simpler and more efficient route.

and Sneaky Voltage does not equal Current. THEY ARE NOT THE SAME THING.

Voltage = Current x Resistance.

[1Time]

zbarnes,
Wecome to the forums! I recommend using a Zalman fanmate. BestByte has them here (http://www.bestbyteinc.com/prodinfo.asp?number=FSC-ZAL-FM1&variation=&aitem=10&mitem=26).

[zbarnes]

Ya, sorry sneaky... R=V/I, they can't be the same. I should know that though, I am a computer engineer major.

I was kind looking to just make one little knob for my external radiator setup, which is why I was going to reuse that thing I have ^.

Since fans has a range of voltage that they can operate on, would varying the current by resistence be fool-proof? I don't know what would affect performance or sound....

I don't really want to buy a front case panel thing(or anything, really), I have a door that covers the front part of my case.

That zalman fan mate is what I am trying to do, but I don't have 5v fans, only 12v.

[magick_man]

the fanmate doesnt run 5 v fans only
it will run any 12v fan that you plug into it
but it will only give you the ability to vary the output voltage to the fan from 5 - 11 volts

~Magick_Man~

[zbarnes]

In that link from best-byte:

"3. Do not use FAN MATE 1 with a fan having a start up voltage of more than 5V.
Please check the start up voltage in the specifications of the fan. "

I thought it meant the delta 12v I'm going to use would be a no. I see.

I'd have to snip both ends off though, since I won't be powering through the mobo and the fans are only two pin. I'm thinking I might as well make one of these:

http://www.ocforums.com/showthread.php?t=351815&page=1&pp=30

Only problem is that I don't know how those delta's will respond.... Will they be quiet if I lower the current majorly? I don't know