fans run after shut down?

T

Teknokid

[H]ard|Gawd
Joined
Feb 17, 2007
Messages
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is there a way of modding the psu to continue powering fans after shut down. all my fans go through 2 fan controllers so it needs power through the molex's. could you add a switch to link the green and black leads so the molex's power up thus turning the fans on?
thanks
 
I know the purple wire from the PSU is always powered with 5v. I'm not sure if this helps or not...
 
That's the 5V standby line, and it's usually not rated for more than a few dozen milliamps. And each fan will want somewhere in the region of 250-350mA. So using the standby line is a no-go. To be honest, you'll have to somehow rig a separate power supply to power those fans.

Can you tell us why you want to do this?
 
i just want to cool the internals down after shut down. i heard linking green and black powers the molex's...
 
It will power the molexes, but it'll also power everything else :) It actually will turn your computer back on.
 
Whats the point in cooling the case down after shutdown? Its not hurting anything by cooling off slower.
 
For the life of me I can't remember where, but there was actually a fan controller with a special feature to do exactly that. It'd run the fans for several minutes after a shutdown to keep temps down. It was only like $10 or something like that. I googled for a couple minutes but couldn't find it again.
 
I was thinking along the lines of a wall wart too...would be pretty easy to pull off.
 
I saw this exact thing at microcenter. kept your fans on for like a couple of minutes after the computer shuts off. This isn't it but it would work.
 
There's really no good reason to cool down your components after you turn off the computer. Even with all the fans off, nothing will be getting hotter, since nothing is generating any heat when the computer is off. And all those components were actually quite happy being warm. If anything, letting them cool down gradually is probably better than trying to cool them to room temperature ASAP, because you have a slower, more gradual, more even temperature change.
 
Mohonri said:
There's really no good reason to cool down your components after you turn off the computer. Even with all the fans off, nothing will be getting hotter, since nothing is generating any heat when the computer is off. And all those components were actually quite happy being warm. If anything, letting them cool down gradually is probably better than trying to cool them to room temperature ASAP, because you have a slower, more gradual, more even temperature change.
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+1

Thermal shockand and related "chip crawl" are big killers. Perhaps even more of an issue than esd in many situations...
 
Would an big inline cap be able to hold enough current to keep the fan running for another 5/10 minutes?
 
c.d.e said:
Would an big inline cap be able to hold enough current to keep the fan running for another 5/10 minutes?
Click to expand...
No. And if it were, the fan would start off at full speed, then tail off. The capacity of a capacitor is C = I/(dv/dt). If you have just one fan running at 250mA (typical). If you wanted the voltage to drop only 2V (from 12V to 10V) over the course of a minute, the capacitor would have to be = .25/(2V/60s) = 7.5 Farads. That's an enormous capacitor (the biggest on digikey is .12F), and you won't be able to find anything with a reasonable price for that.
 
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