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# computer fans - Very basic question from a beginner...!

#### Danzig Herzog

Apr 24, 2015
4
Hi all,
I have 2 identical small computer fans which I want to run from the mains, and they need wiring to an adapter, and I wanted to know which one would be right.
On the back of the fan, it says it is 12V, 0.30A. To power 1 of them, I'm assuming that I would get an adapter that was the same Amperage of 0.30, and a variable voltage up to 12V. (I'd like to be able vary the fan speed with the voltage.)
Is this assumption correct? If the adapter exceeded 0.30A, could it damage the fan?

I also assumed that if I wanted to wire up both fans in a parallel circuit, I would use an adapter with 0.60A, and 12V. Is this assumption correct?
Many thank, would be grateful for any answers to this basic question!

#### BobK

Jan 5, 2010
7,682
The current capability does not matter as long as it is greater that needed by the device being powered. An electronic device will draw only the current it needs when provided the correct voltage.

Bob

#### Danzig Herzog

Apr 24, 2015
4
Hey Bob, Many thanks!
I connected both the fans up in a parallel circuit, from a 0.60A adapter. Now I have a head scratching problem that 1 of the fans is rotating at nearly half the speed of the other.. Im totally stumped. Any ideas?

#### davenn

Moderator
Sep 5, 2009
14,296
you sure their ratings are identical ?
are you sure you have them in parallel and not series?
if the total current of the fans is indeed 0.6A then you should really be using a 1A plugpack

Dave

#### Kiwi

Jan 28, 2013
474
As previously advised, you need an adapter that is capable of delivering more current than is required by the fans. Running your adapter at full load is not a good idea. I would go with Dave's suggested 1A plugpack.

Assuming that you have the fans wired in parallel, here are a few reasons for the differences in fan speed you are having;
A faulty fan causing it to run slow,
Poor quality fans with a wide variation in performance,
Adapter voltage falling due to running at 100%,

#### Danzig Herzog

Apr 24, 2015
4
Thanks for the answers, very informative! The fans are identical, and it seems very unlikely for the quality to be poor, as they are well reviewed.

I shall do some more tests to find out. I have a spare 2.25A 12V plugpack lying around.. Would this one be a good choice, or would a 1A be more ideal? Or would there be no difference whatsoever?

#### davenn

Moderator
Sep 5, 2009
14,296
I have a spare 2.25A 12V plugpack lying around.. Would this one be a good choice,

yes

or would a 1A be more ideal? Or would there be no difference whatsoever?

for this application ... no difference whatsoever

Dave

#### Danzig Herzog

Apr 24, 2015
4
Hey, this worked perfectly, many thanks for all your advice!

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