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Rheostats on fan headers?

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AD

Registered
Joined
Feb 9, 2001
Has anyone installed a rheostat inline with a Mobo fan header so you can still retain the rpm monitoring function? Are there any risks to the mobo? Thanks -ad
 

Colin

Arctic Silver Senior
Joined
Dec 19, 2000
Go to the Shack and get an LM317 voltage regulator. The circuit is on the back of the package. Much better solution than a rheostat.
 
OP
A

AD

Registered
Joined
Feb 9, 2001
How about this....if I have a fan bus setup with rheostats, could I just attach the third wire from each fan to a the rpm pin on the mobo fan headers? Then I would adjustable and monitored rpms right? Would this work?
 

Hoot

Inactive Moderator
Joined
Feb 13, 2001
Location
Twin Cities
I agree with Colin. 3 terminal regulators are a breeze to impliment, but if you want to use the rheostat and maintain RPM monitoring, only break the + wire of the three and leave the ground and RPM alone. Insert the rheostat in the + lead and you're all set.

Hoot
 
OP
A

AD

Registered
Joined
Feb 9, 2001
that's what I meant, but you said it more clearly. Im looking at that LM317 voltage regulator circuit and I dont understand how it will allow me to adjust the fan speed. It shows a variable resistor going to ground. How is this different or better than just putting the potentiometer on the + line? Could you explain please?
 

Colin

Arctic Silver Senior
Joined
Dec 19, 2000
The LM317 takes the heat instead of the rheostat. It's more effecient and protects your PSU.
 

Richard

Senior Member
Joined
Jan 15, 2001
Assuming an average 120 mm fan...

If I am to use an LM 317T voltage regulator. What rating potentiometer do I need? Does it matter, since the LM317 is acting as the buffer?



Colin (Mar 01, 2001 10:19 p.m.):
The LM317 takes the heat instead of the rheostat. It's more effecient and protects your PSU.
 

Hoot

Inactive Moderator
Joined
Feb 13, 2001
Location
Twin Cities
You can use a conventional 1/4W carbon based pot or even a 1/8W trim pot. The current through it it very minimal.

Hoot