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How to power a fan without a PSU?

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August 7, 2007 9:42:27 AM

The question might seem weird, but I'd like to power up a fan, with a 3 Pin Molex connection. This fan will not be used inside a computer, so is there any power supply thing that you can plug in the wall on one side, and that has a 3 pin molex connection on the other side?

Otherwise, is it possible to DIY a power supply just for this regular fan?

Thanks for any help, I didn't find anything when searching the forums...

More about : power fan psu

a b ) Power supply
August 7, 2007 9:54:41 AM

A 12v dc power supply is what you would need, be it a battery or an AC/DC mains adapter and some creative connecting.
August 7, 2007 10:10:51 AM

Why? You can get a small AC fan for less than you'll spend for the dc power supply...
Related resources
August 7, 2007 10:19:06 AM

My PC is in an isolation box. I want to get a second iso box, but they are very expensive, so I'm looking into a DIY solution. The first idea that came was to use 80mm or 120mm fan for ventilation. But you're right, a small ac fan might be ideal. Any link or manufacturer on the top of your head? Thanks!

Edit: I'm looking for a quiet fan... the Noiseblocker one linked above is at 18dB/A only.
August 8, 2007 4:01:21 PM

If you want to move a lot of air quietly, look for a squirrel-cage fan.

Regards,

Altazi
August 8, 2007 7:13:20 PM

Gabor,
I did a DIY solution for my Home theater system. Check out Coolerguys.com under their home theater/cabinet cooling section. They have an 110v AC to 12v DC converter. I'm using it to power 3 Scythe S-Flex 120mm fans. I used the chrome grill guards on each side of the fan and bolted them to the back of my cabinet. I used a dremmel to make the round fan holes. They also have AC power fans too. I had picked up 2 of them before I started but then decided I wanted more cooling and quieter fans. My AV cabinet is split into 2 sides, and each side has one shelf. I hole drilled 2 1/2 inch air ports in the bottom and used black desk grommets to mask the holes. I ended up using 5 fans total. The 3 Scythes are on the back of the cabinet (very quite too) and I used the 2 AC fans (moderate noise) and mounted them via screws underneath 2 of the shelves which I also dremmel out round wholes to match the fans. I have a Cable Co. supplied DVR (called a Moxi) which is very loud as it is always on and it produces a lot of heat. I had to leave the cabinet door open to let air into it. It was louder that way before the fans, now I can close the cabinet doors and can barely hear the DVR and the fans.
August 8, 2007 7:37:33 PM

Some of the small chargers (Transformers) for Telephones, Answering Machines, Tools, Flashlights etc. have 12v output.

Solar Power is another solution.

The conversion of Watts to Amps is governed by the equation Amps = Watts/Volts
For example 12 watts/12 volts = 1 amp
a b ) Power supply
August 8, 2007 8:02:18 PM

You might try to google " muffin fans ". I have one of the "old" 120 mm 120 Volt fans (same size as 12 V version, but more power). Mine is 14W and blows 110 cfm - Real, not like case fan adverts. Also noise, but newer model may be quieter.
August 8, 2007 10:33:35 PM

a separate supply box is probably the most convienient and simplest way to run the fans off a different supply.

you could convert and old 12VDC wall socket charger or supply (from an old printer or something) and hook up some 4-pin molex connections to it.

if you wanted to be fancy, you could fit a jack socket for the plug of the 12VDC wall socket, to your case (bearing in mind not the short any connections to your case).

that way you could just unplug the jack just like the mains plug if you needed to move your PC.

but make sure you get/find/buy a 12VDC supply that can cope with x amount of fans, otherwise: pop!

some calculation is in order.

I have an idea.....
February 6, 2009 7:21:08 PM

Hi all,

I found this old post through a Google search and wanted to ask a follow up for anyone that might be able to assist. Basically, I took an old DC supply that used to power a pair of cheap pc speakers. Its 12V 500ma. I took a pc fan out of an older system I had which I believe is 12v .14a (140ma). Is there an issue of too much power here? I plugged it in and it seems to work fine but I don't want to cause a fire or for this to overheat.

Thanks in advance,
Bill
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