How to Undervolt a Fan Inside a Small Device?

I only see one single two-pins connection on the circuit board of that
small gigabit switch. This means this option is not available.

Moreover, I believe 5-volt may be too low, and the fan "may" have a
problem to start spinning according to what I read in other newsgroup
about undervolting a fan to keep a PC quiet.

Jay Chan

Thanks for the detailed reply that you have spent the time to prepare.
I appreciate your help.

I especially appreciate the fact that you have gone through the trouble
to find a picture of the 120 ohm resistor. Now, I have an idea of what
I should be looking for.

Also thanks for telling me the details on the way to attach it to the
wiring.

I will buy a range of inline resistors plus the 68 ohm resistor that
you have suggested, and several alligator clips.

Jay Chan

I use a Zalman Noiseless Resistor Cable from
http://www.quietpc.com/uk/casefansacc.php#rc56 and it has made my PC quiet.

Mike

Glad to hear that you have good result with using that Zalman resistor
cable.

I came across the exact same item last night when I was looking around
for a solution. But I was not exactly sure how I could use this
3-wires item into my 2-wires configuration. Moreover, I didn't know
whether the resistor was the right item for my 60mm fan. Therefore, I
figured I should ask first before spending the money. Now that I have
received some helpful info here. I have a feeling that the Zalman
resistor cable could work. I just needed to cut out the plugs and only
used the resistor. But if I needed to cut out the plugs, I might as
well order the resistor alone from elsewhere. Having said that I
should add that that Zalman resistor cable should be useful for people
who need to reduce the noise of a case fan without soldering.

By the way, what's the ohm rating of that Zalman resistor cable, how
many watt, and what size fan do you use the cable for? I am just
curious.

Jay Chan

wrote:

I only see one single two-pins connection on the circuit board of
that small gigabit switch. This means this option is not available.

Moreover, I believe 5-volt may be too low, and the fan "may" have a
problem to start spinning according to what I read in other
newsgroup about undervolting a fan to keep a PC quiet.

Without quotes and attributions your messages make no sense. See
my sig below for a means of sane use of google.

--
"If you want to post a followup via groups.google.com, don't use
the broken "Reply" link at the bottom of the article. Click on
"show options" at the top of the article, then click on the
"Reply" at the bottom of the article headers." - Keith Thompson

On 16 Mar 2005 09:53:19 -0800, wrote:

Thanks for the detailed reply that you have spent the time to prepare.
I appreciate your help.

I especially appreciate the fact that you have gone through the trouble
to find a picture of the 120 ohm resistor. Now, I have an idea of what
I should be looking for.

The optimal type would have that semi-barbell shape, but
usually are not cut (leads) and formed (bent leads) yet,
which is no problem either way, the leads are quite easy to
cut and bend. Often the resistors will not be solid green
like the one I linked but colored based on type and striped
to indicate the value. For example the Zalman resistor Mike
linked wasn't a great picture but appears to be striped:
Green, Blue, Black, Gold, which is a 56 Ohm 5% tolerance
resistor. Don't worry about tolerance, this is not a
precision application requiring any particular tolernace
part.

Generally speaking, the faster the fan is at default (12V),
the lower the value of the resistor to use to reduce it's
speed. This initially seems contrary to reason but is due
to the lower resistance of the fan's windings & circuit. I
expect 68 ohms to not be a large enough value but I do not
have any of that particular model of fan to experiment with.



Also thanks for telling me the details on the way to attach it to the
wiring.

I will buy a range of inline resistors plus the 68 ohm resistor that
you have suggested, and several alligator clips.

The heatshrink tubing is very handy too, maybe 3/32 (+-
1/32)" is the right size tubing depending on the fan's
wiring gauge.

Without quotes and attributions your messages make no sense. See
my sig below for a means of sane use of google.

--
"If you want to post a followup via groups.google.com, don't use
the broken "Reply" link at the bottom of the article. Click on
"show options" at the top of the article, then click on the
"Reply" at the bottom of the article headers." - Keith Thompson

How does it look now? Does it show up the right way?

Jay Chan

... For example the Zalman resistor Mike
linked wasn't a great picture but appears to be striped:
Green, Blue, Black, Gold, which is a 56 Ohm 5% tolerance
resistor.
Generally speaking, the faster the fan is at default (12V),
the lower the value of the resistor to use to reduce it's
speed. This initially seems contrary to reason but is due
to the lower resistance of the fan's windings & circuit. I
expect 68 ohms to not be a large enough value but I do not
have any of that particular model of fan to experiment with.

If I understand this correctly, you are say these:

- We could have gone down to 56 ohm for maximum reduction of fan speed
and (hopefully) noise. But we may run the risk of the fan fails to
start spinning.

- In order to reduce the chance of fan failure to start spinning while
still cutting down noise, we may want to choose a 68 ohm resistor
instread of a 56 ohm version.

This makes sense to me. Thanks.

The heatshrink tubing is very handy too, maybe 3/32 (+-
1/32)" is the right size tubing depending on the fan's
wiring gauge.

Yes, I have already had a pack of heatshrink tubing left over from my
previous project of re-wiring some phone-cables in my basement.
Therefore, I don't need to buy any more of this. Your reminder will be
helpful for people who may jump into the middle of this thread without
seeing prior discussion of using heatshrink tubing though.

Have a happy St. Patrick Day!

Jay Chan

wrote in message
ups.com...
... For example the Zalman resistor Mike
linked wasn't a great picture but appears to be striped:
Green, Blue, Black, Gold, which is a 56 Ohm 5% tolerance
resistor.
Generally speaking, the faster the fan is at default (12V),
the lower the value of the resistor to use to reduce it's
speed. This initially seems contrary to reason but is due
to the lower resistance of the fan's windings & circuit. I
expect 68 ohms to not be a large enough value but I do not
have any of that particular model of fan to experiment with.

If I understand this correctly, you are say these:

- We could have gone down to 56 ohm for maximum reduction of fan speed
and (hopefully) noise. But we may run the risk of the fan fails to
start spinning.

You've got it backwards. Lower value resistor means faster spinning fan.
Having no resistor is the same a 0 ohms.

- In order to reduce the chance of fan failure to start spinning while
still cutting down noise, we may want to choose a 68 ohm resistor
instread of a 56 ohm version.

Adding a 68 ohm resistor will slow the fan more than the 56 ohms.

wrote:

Without quotes and attributions your messages make no sense. See
my sig below for a means of sane use of google.
*
* --
* "If you want to post a followup via groups.google.com, don't
use
* the broken "Reply" link at the bottom of the article. Click
on
* "show options" at the top of the article, then click on the
* "Reply" at the bottom of the article headers." - Keith
Thompson

How does it look now? Does it show up the right way?
*
* Jay Chan

That looks fine. Very good. Now you just need to learn to snip
the useless portions that are not germane to the reply. In this
case it would be all the lines preceded by * above.

--
"If you want to post a followup via groups.google.com, don't use
the broken "Reply" link at the bottom of the article. Click on
"show options" at the top of the article, then click on the
"Reply" at the bottom of the article headers." - Keith Thompson