USB Fan question

ceraf · Post by **ceraf** » Wed Apr 25, 2007 2:05 pm

This is more of an electrical question, but i don't know where to put this...here it goes:

I'm thinking of making a laptop cooler, using the USB port as the source. What's the maximum current I can draw safely from one port?

qviri · Post by **qviri** » Wed Apr 25, 2007 2:25 pm

USB spec officially allows 500 mA at 5 V, so this is the minimum you will be able to get for sure. Many ports, but not all, are wired to safely deliver more, but the value depends on the particular laptop.

angelkiller · Post by **angelkiller** » Wed Apr 25, 2007 4:10 pm

I could be completely wrong, but doesn't Windows shut off current if too much is drawn? (eg short circuit)

Stefx · Post by **Stefx** » Wed Apr 25, 2007 5:53 pm

angelkiller wrote:I could be completely wrong, but doesn't Windows shut off current if too much is drawn? (eg short circuit)

Yes. I had a warning once that too much current was being drawn and it deactivated that port

Willy Higinbotham · Post by **Willy Higinbotham** » Thu Apr 26, 2007 4:31 am

I know this may sound stupid, but get an el-cheapo power supply and connect the fans directly to it.

This is something that I've been considering to make my own laptop cooler. Since I use my laptop on a desk, mobility is not a concern for me.

ceraf · Post by **ceraf** » Sat Apr 28, 2007 2:00 pm

kay, here's what i came up with...i cheaped out on materials, but at least it's not very noticeable in class...besides the slight fan noise.

I'd like to be able to swap out fans with different connectors, hence the mass of wires. Could be a lot simpler.

Because of the height of the fan grill, i had to raise the laptop a bit.

I don't feel much airflow, probably because of the low clearance between the laptop and the fan.

angelkiller · Post by **angelkiller** » Sat Apr 28, 2007 4:26 pm

It's in a notebook!

Great idea! Really like this. Simple and very effective. 80mm fan? What about a larger one? Like 120mm. Or 200mm!

Actually, I might consider one of those. Nice work.

Can you tell a difference in temperatures?

ceraf · Post by **ceraf** » Sat Apr 28, 2007 5:56 pm

actually, windows xp on my laptop hard drive is currently dead, so I haven't had the chance to measure temps yet. I'll post temp differences when I can.