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Slowing down a fan

Hi I have posted previously about a modified PC case that my nephew is currently building. It incorporates a 12V car radiator fan into the base.

We have got it running off an old PC power supply, but as was previously mentioned, it is quite loud and a bit too powerful. Now we need to be able to slow it down a bit. The specs on the fan say it runs on 12V and max current is around 11A (11.2A I think?)

How is the best way to do this? I thought about a resistor, but would it have to be a huge one to take the 11A current? What size resisters would I need? What would be the best way to do this? I tried doing the 7v trick by running it between the 12v & 5v lines but the power supply just shuts down.The fan itself won't be running all the time. It will just be switched on when extra cooling is required.

Any help would be much appreciated. Grenge

Reply to
Grenge
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Have you tried running it from 5V only, or is that not sufficient?

Reply to
rowan194

If you are determined to continue with this overkill, find out what current the fan draws at say 9v and provide a suitable supply. There are many other fans available that will move the air for much less current and less noise.

--

Cheers ......... Rheilly P

Where theres a will, I want to be in it.
Reply to
Rheilly Phoull

There's a DC motor speed controller kit that was done by Silicon Chip magazine that will do the job for you. I think DSE and Jaycar sell it, so all you need to do is build it and put it between your fan and the

12v power supply.
Reply to
dale-google

PWM DC speed controller. maybe something like this.

in914 x2 +12 | +-------->|--+----------------------+ 1n4001 | | | | | +--[10K]-|

Reply to
jasen

What sort of fly trail is that???

Reply to
two bob

A shcematic one

Reply to
atec77

near enough to be readable as one though ... in the trade I am in a mudmap...

Reply to
atec77

A shcematic one

****Looks like a fly flew through your flue,it certainly is NOT a SCHEMATIC.

Brian Goldsmith.

Reply to
Brian Goldsmith.

"atec77" wrote

near enough to be readable as one though ... in the trade I am in a mudmap...

**** And obviously thick enough not to see the reference to your "shcematic".
Reply to
Brian Goldsmith.

Or not caring

as a personal foible I often refer to mud maps as such now just to remind you when all else fails a spelling comment proves you as an ass and certainly won't win any discussion.. on the net at least.

Reply to
atec77

Somewhere back in history in tech, that schematic would be a "FAIL" mark. I had a boss who used to "create" things like that, and wondered why no one could get their job done.

Pablo Piccaso, watch out!

Reply to
two bob

For the people too stupid to spend 10 seconds cutting and pastings into a text editor with a fixed font size I've done the hard work for you:

formatting link

Reply to
rowan194

I have no problems reading it :)

Reply to
atec77

If it's not looking a bit like a schematic try setting your news reader to use a fixed pitch font (like courier) or pasting the above into notepad. You'll have to guess where the earth connection goes as I left that bit off.

--

Bye.
   Jasen
Reply to
jasen

Get a smaller Fan....

It would not be drawing 11Amp by the time you had a resistor in series....

11A at 12V gives 1.1 Ohm - so a 2 Ohm resistor in series would dissipate around : 12/3.2 = 3.75A

3.75^2 x 2 = 30W - you would get away with 2 x 1 Ohm 10 Watt resistors in series and place them in the airflow from the Fan which should keep them cool enough (You may even get away with a single 10Watt 2.2 Ohm resistor if it is fan cooled).

Go down to your nearest Jaycar and buy a number of different value 10 Watt Resistors and see what speed/Noise you get from the fan with different Resistors in series - be daring Experiment a little - a 10 Watt Resistor will actually handle 20-30 Watts for a few Hours - or if fan cooled indefinately.

Bear in mind though that a Radiator Fan may not be the quietest Fan available.

Regards Richard Freeman

Reply to
Richard Freeman

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