How to get 7v
 

My 120mm fan for my rad is really loud running at 12v. I just wanted to know how to get 7v off of an IDE power lead. I know there is 5v and 12v on the IDE power leads, but how do you aquire 7v? thanks for your help.

It's been a while since I did this mod, but if I remember it goes like this - connect the red wire (positive) from the fan to the yellow wire (+12V) from the molex/ide connector, and the black wire from the fan (ground) to the red wire (+5V) from the molex connector. That'll give you a difference of 12-5 = 7V for the fan. I found some of my 120mm fans wouldn't quite spin up at 7V, so I'm using a rheostat instead to cut the voltage down to about 8V for them, which seems to work. Try it and see though - if it works, your fans will be a hell of a lot quieter :)

Hopefully this pic might help as well:

Hmm, didn't seem to like the attachment... let's try again :)

Thanks for your help. I was also considering getting rheostats and making a baybus because i have other fans i would like to control as well. Where can you go to pickup rheostats? Im guessing radio shack. Also are there diffrent ones, should i just but ones rated for 12v. Are there any tutorials on making bay busses. thanks for the help.

We covered that just last week, in another thread. I'm sure that if you run a search you'll find it.

The rheobus is very easy to find, with Google.

Heheh I remember that thread BigBen and was going to post a link here........but never could find it again :)

BTW Red to 12+ and Black to 5+ shoudl yeild nothing because you dont have a closed electrical circuit. You have to have the Red line connected to a (+) and the black one to a ( - ).

I hope your not going to correct me on that one Bigben :)

Found it

+12 to +5 will work, because there is a potential difference. Think of the +5 line as the ground, and you'll see that the the +12 line is 7 volts above it.

it does indeed work, i've tried it. if your fan won't spin up at 7v just put it on a simple spdt switch to switch between 12 and 7v. all you have to do is run the 12v directly to the fan, then a 5v to one side of the swith and ground to the other, and the wire out the middle of the switch to the black wire of the fan. flipping this back and forth will change between 12 and 7. i have a similar switch in my case to go between 12 and 5. My 120 has no trouble starting up even with 5v but i guess each fan would be different.

troy.

Interesting............

I have both my 120mm H1A panflows running at 5 volts, and my L1A running at 7 volts, perfectly fine for me.