120mm 12v connect 7v then to motherboard?

grandpatzer · Post by **grandpatzer** » Tue Feb 16, 2010 11:52 am

is there any danger connect a 12v fan to a 7v or 5v adapter then connecting it to one of the motheroboard fan plugs(cpu, sys, gpu)

mentawl · Post by **mentawl** » Tue Feb 16, 2010 12:05 pm

In that case, you'd only want to connect the yellow sense wire to the motherboard. The only voltage droppers you want to connect directly to a 3-pin motherboard connecter are ones that use resistors to drop the voltage rather than shunting the voltage using the 4 pins on a molex plug.

washu · Post by **washu** » Tue Feb 16, 2010 12:27 pm

I've found that with a 7 volt molex mod that the sensor no longer works because the "ground" of the fan is actually +5V.

Using just +5V seems to work just fine.

grandpatzer · Post by **grandpatzer** » Tue Feb 16, 2010 6:44 pm

1. my motherboard does seem to have fan voltage control, my understanding now is putting a 7v or 5.5v resistor on the fan the connect to motherboard i 100% safe/harmless?

2. will I loose the rpm function of the motherboard when connecting resistor?

3. my understanding from washu post is that 5v resistor will still give voltage regulation from motherboard if I did not misunderstand?

4. My assumption would further be that fans that need 5v will be off when low temperature and get juice from motherboard once temperature rises?

Vicotnik · Post by **Vicotnik** » Tue Feb 16, 2010 8:14 pm

There's no such thing as a 5v resistor.

Explain what you are trying to do instead. You have a fan connected to the motherboard and you want to lower it's speed? Do you want the speed to be fixed or variable? If variable, do you want it to be automatic or manually controlled?

edit: Also, please do not spam the forum. You have started a number of threads now, all related to the same question. Slow down a bit, we'll help you.

grandpatzer · Post by **grandpatzer** » Wed Feb 17, 2010 1:55 pm

What I want to do is place the resistor between the motherboard and the fan.

I meant the 12v--->5.5v resistor:

http://www.inet.se/artikel/6308177/mots ... 5-5v-3-pin

My goal is to have the 800rpm Slip Stream at 1-550rpm.

Vicotnik · Post by **Vicotnik** » Wed Feb 17, 2010 4:25 pm

That would work. But there are also other ways.

More talk related to this subject here
- viewtopic.php?t=57475

grandpatzer · Post by **grandpatzer** » Wed Feb 17, 2010 4:35 pm

thank you for reply.

my main goal beside silence is to not fry/damage the mobo/psu.
incase there is any risk of putting a 5.5v or 7v resistor between the fan and mobo please tell me.

mentawl · Post by **mentawl** » Wed Feb 17, 2010 5:40 pm

Nah, you'll be fine putting a resistor-based adapter between the motherboard and the fan. I've been running 3 fans like that for several months now.

Tephras · Post by **Tephras** » Wed Feb 17, 2010 5:40 pm

The main purpose of the adapter you linked to is to use it as you intend to do, between a fan and the motherboard, it will not cause any damage.

dun · Post by **dun** » Wed Feb 24, 2010 3:44 pm

I've used several of the previously mentioned resistors, and connected fans directly to the motherboard, this has never caused any problems, and works like a charm. They also work great if you want to undervolt your fans to lower than 5v, by attaching them between a fan and a 5v connector, but not all fans start reliably on such a low voltage.