Running fans at 7 volts?

[torreyk]

I want to put an extra fan in my case and was wondering what wirs i need to connect to run it at 7 volts. Its a Thermaltake fan with a 3 pin connector that sounds like a freightrain when its running at 12v. I have a 3-4 pin adapter I can use with this fan. Thanks for any advice.

 

[Budman]

for 7 volts you connect the 2 wires on the ends,the yellow & red wire.

 

[torreyk]

Thanks for the info man

 

[Gene396]

Budman, you got it wrong. The red wire is 12 volts, bkack is ground and yellow is 7 volts. If you connect between red and yellow you only get five volts!! Also many fans do not have a yellow wire; it is blue instead.

Suggestion why don't you put a rheostat in 12 volt line and vary the voltage to your needs? Afterward you can put a resistor of that value in red line.

 

[Budman]

Originally posted by: Gene396
Budman, you got it wrong. The red wire is 12 volts, bkack is ground and yellow is 7 volts. If you connect between red and yellow you only get five volts!! Also many fans do not have a yellow wire; it is blue instead.

Suggestion why don't you put a rheostat in 12 volt line and vary the voltage to your needs? Afterward you can put a resistor of that value in red line.

Gene You're the one who's wrong, By pitting the +12V rail against the +5V rail, you can achieve +7 volts.

look here.

Educate yourself here.

 

[ChefJoe]

That would be so nice to have a 7 volt rail.... best way I figured out to do that is to rewire one of those 3 to 4 pin adapters around on only one end, then everything down the line from that can be plugged in and get 7 volts automatically. only trick is you have to make sure all the adapters are consistant (I've seen em use different "ground" lines at times).

 

[Gene396]

Budman, you are correct. My apologies to you. I keep hearing the "7 volt trick" until I forgot and began to believe there is a 7 volt line; when I know better. The power supply puts out 2 voltages; 12 and 5 plus the same negative. If you use the yellow and black you get 5 volts. By using the yellow as ground the system recognizies that the red is 7 volts higher than the yellow.(12-5=7 or 7 volt trick) Remember that some fans do not have a yellow, but is blue instead.

I do suggest that you put a rheostat in 12 volt line so that you can get other voltages to fan. That way you can "dial" in the speed and cooling to your liking.

 

[cdsonic]

Go to Here and then click on the step by step tab and in there the is Article with pictures to show you how to make what you want.

 

[Lizardman]

haha gene 7volt rail you make me laugh.