Rheostats on fan headers?

[AD]

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]

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.

[AD]

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]

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

[AD]

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]

The LM317 takes the heat instead of the rheostat. It's more effecient and protects your PSU.

[Richard]

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]

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