Fan Startup Mod

krusty · Post by **krusty** » Thu Aug 10, 2006 8:55 pm

First off,

Thanks MikeC. Great Website.

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My 140mm PS fan would run very quiet at 5v, but would not startup at 5v.

Added a startup capacitor

http://finance.ph.groups.yahoo.com/grou ... =1&m=f&o=0

Now starts and runs very quiet at 4.52v

Adding a startup capacitor helps for those fans that have startup problems, but run quietly at lower voltages.

Obviously, use at your own risk!

140mm fan

http://www.newegg.com/Product/Product.a ... 6835129249
Cut out the LED's and wired a 250 ohm potentiometer

Avalanche · Post by **Avalanche** » Fri Aug 11, 2006 9:22 am

From fan spec sheet on Newegg:

Noise Level 19.6dBA (Condition: background noise lower than 17.0dBA)

How can you have a 'condition' on a sound power measurement? Do you think AeroCool is simply specifying the conditions they made the measurements in?

breunor · Post by **breunor** » Fri Aug 11, 2006 9:29 am

I think they are stating the background noise when they measured the sound output of the fan, which is pretty cool. Someone here posted the math on how the fan noise+background noise=recorded noise.

cAPSLOCK · Post by **cAPSLOCK** » Fri Aug 11, 2006 1:01 pm

I would like to see how you did it, but Yahoo! wants me to sign up or some BS. No way.

Le_Gritche · Post by **Le_Gritche** » Fri Aug 11, 2006 2:05 pm

krusty wrote: Added a startup capacitor

http://finance.ph.groups.yahoo.com/grou ... =1&m=f&o=0

Now starts and runs very quiet at 4.52v

I can't access that link, a yahoo account is needed. Could you host the picture on www.imageshack.us ?
What are the specs of the capacitor (and how did you choose them) ?

Can you tell what happen when you shut the computer off ? Does the capacitor unloads its load through the potentiometer, or does that get fed back to the PSU through the fan connector ?

cmthomson · Post by **cmthomson** » Fri Aug 11, 2006 4:10 pm

He used a 3300 uF 35V capacitor across a 250-ohm pot, inline with the fan 12V line. The capacitor charges when power is turned on, drawing extra current through the fan. Once the cap is charged, the current drops and the fan slows down. When power is removed, the cap discharges through the pot.

Simple and elegant.

krusty · Post by **krusty** » Fri Aug 11, 2006 4:31 pm

http://img163.imageshack.us/img163/1598 ... modao6.gif

I think the 250 ohm pot in parallel with the cap will discharge it safely
when powered off, so I think it's safe. Been thru many power cycles.

However:

Disclaimer:
USE AT YOUR OWN RISK

DrCR · Post by **DrCR** » Wed Aug 16, 2006 1:15 pm

Clickable Thumbnail / Backup Linkage for posterity:

Fan Startup Mod

Fan Startup Mod

Re: Fan Startup Mod

Fan Startup Mod at imageshack