2 fan headers to 1 fan? Possible?

[lastig21]

Instead of a rheostat, would this be possible?

As you can tell, I know nothing about currents. What I would like to do is set some resistors in the line of the digital doc fan headers. At one temp I could run the 120mm fan at half speed, at another temp a seperate power feed would kick on to bring the fan to full speed. This would mean 2 fan headers (6 volts each) running into one fan. Could I do this or would I fry something in my pc? Can anyone tell me how to do this or point me to a site that does?

 

[FlowerMan]

If the 120mm is not spinning, the 92mm will have a hard time pushing anything. I suggest you simply shroud the 120mm fan about 1-2" away from the rad and keep it sucking air from the rad. This should decrease some of the noise. You can also connect a rheostat or LM317 setup to that 120mm fan to control its RPM at any given moment.

 

[lastig21]

I was afraid of that. Anyone else have any more input? Would the 120mm be affected with the 92mm spinning underneat it?

 

[lastig21]

Also, anyone have a link to an easy (yet decent looking) single fan rheostat?

 

[FlowerMan]

Have you shrouded the fan? That'd be the first step. Adding a 92mm would not help, IMO. You can get a 3-5W Rheostat from Radio Shack and hook it up to the positive lead of the fan. Just play around with it, you'll figure it out.

 

[lastig21]

edited to set as topic

 

[RazeOrc]

If you stack fans and have the one from behind blow you'll create a lot of turbulance which means all the air is not going to travel in a straight path through the radiator which means a lot of lost airflow, a better idea would to simply muffel ur sound using a duct to the rear of your computer or repositioning your radiator. Otherwise you may even consider using 2 smaller fans with equal CFM but lower noise.

 

[FlowerMan]

<< Instead of a rheostat, would this be possible?

As you can tell, I know nothing about currents. What I would like to do is set some resistors in the line of the digital doc fan headers. At one temp I could run the 120mm fan at half speed, at another temp a seperate power feed would kick on to bring the fan to full speed. This would mean 2 fan headers (6 volts each) running into one fan. Could I do this or would I fry something in my pc? Can anyone tell me how to do this or point me to a site that does? >>



Does the Digidoc allow for variations of the RPM of a fan? I dont think so, but if it does, just setup it up to do so at the desired temps. There is no way to set the fans to automatically adjust their voltage without expensive equipment or ungodly amounts of calibration and electronics knowledge.

Ok, just read your message again and it makes a little more sense to me. You want to have 2 power sources for a fan, but only have one source when the system is idle (read: low temp). I suppose that would be possible if you could get the DD5 to supply 6 volts to those 2 power sources. Be aware that some fans will not start up at 6V.

 

[lastig21]

The digital doc does not allow for fan speed variation.

Ok, just read your message again and it makes a little more sense to me. You want to have 2 power sources for - that is correct

I didn't think about 6 volts not starting the fan. Hmmmm

7 and 5 maybe?

 

[FlowerMan]

They might start at 7V. Some do, some dont. Check out my post at the Hard|Forums.