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Old March 16th 05, 05:18 AM
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Default How to Undervolt a Fan Inside a Small Device?

I would like to know the way to reduce the speed of a fan inside a
small device in order to cut down the noise from the fan. If I
understand this correctly, I am supposed to do this by undervolting the
fan from 12-volt it is now to something like 6-volt using some kind of
"inline resistor" or someting. I can soldering wires together. But I
really don't know much about resistor and such. I am hoping someone can
give me the "exact" information about the way to do this.

The small device is a LinkSys gigabit switch that has a very noisy 40mm
fan in it. I have replaced it with a slightly quieter Papst 60mm fan.
My intention is to oversize the fan and then reduce the fan speed; then
I will be able to maintain the same air flow as the 40mm fan but with
less noise. Now, I have the oversized fan mounted inside the gigabit
switch. And I can feel that its air flow is definitely stronger than
the 40mm fan. This means I can go ahead to reduce its speed without
worrying about the possibility of not getting enough air flow. I need
to figure out how to reduce its speed.

My questions a

- I am under the impression that I should use something
called an "inline resistor". Is it the right product?

- Because the gigabit switch has very limit space
inside, the "inline resistor" must be small enough
to fit inside. Will it be small enough?

- The fan is rated as 12V and 0.6 watt with two wires.
What type of "inline resistor" should I use? I am
under the impression that inline resistor is rated
by "ohms". Can someone give me a RadioShack
product-number or something like that?

- Which wire should I solder the inline resistor to the
fan? Red-wire or the blue-wire of the fan?

- Does this matter which way I orient the inline resistor?

Thanks in advance for any information.

Jay Chan