Question 12v Fan Running Off USB

THRobinson

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I have a WD MyCloud EX2 NAS that has a cruddy little 35mm fan that cools nothing and stalls frequently. If it were a 40mm I'd get a Noctua but even then the NAS is programmed to turn the fan on when the drives hit something like 55'C.

For now I have a 120mm USB Fan sitting on top... dropped the average temp from around 40'C down to 25'C.

Found a nice 3D Print online for a new lid that holds an 80mm fan. I have an Arctic F8 12v fan I bought years back and never used sitting here. I was thinking of cutting the 3-pin connector off and adding a USB connector instead. since the back of the WD MyCloud has 2 powered USB ports.

Would that be OK? I mean... probably run half speed but shouldn't harm anything, right? I assume a 5v fan running on a 12v port would damage the fan, but the other way around should be ok?
 

THRobinson

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Haha... that thing cost 3x what the fan does! :D

Saw those on eBay much cheaper but still pricey enough that if I were to spend that money, I'd buy the Noctua NF-A8 5v which comes with the USB adapter.

If I need to spend money that's my plan. I'd like to just use up what I got on hand though.

I wonder how much slower it will run. I have that 120mm sitting on top, so I'm sure it's pulling in a lot of air from the gaps at the sides, and it has a speed select switch, right now set to medium and it's doing well. Maybe a half-speed 80mm with a sealed fit will do just as well.
 

Paperdoc

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It's called a "USB Fan" because it is DESIGNED to run at full speed on 5 VDC. You try that with a 12 VDC normal fan and you will get VERY slow operation and much less air flow. In fact, you may get NO operation - a 12 VDC fan may stall at 5 VDC supply.

This Noctua 80 mm fan is designed for 5 VDC operation.

https://noctua.at/en/products/fan/nf-a8-5v

It's a 3-pin fan (no PWM needed) - speed could be controlled by voltage but your drive unit probably does not try to do that - and can deliver about half the air flow of a 120 mm Noctua of similar design - that's ALL the airflow of a normal 80 mm fan. It draws 0.15 A current (a USB2 port normally can supply 5 VDC at up to 0.50 A).
 

THRobinson

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It's called a "USB Fan" because it is DESIGNED to run at full speed on 5 VDC.
Well... you can get fans designed to work at 5v that aren't USB fans... I think they're called USB fans because of the USB plug. :D

Probably end up with the Noctua 80mm, looks like no dif between the 3pin and 4pin models for this application. Both come with USB adapters. Whichever of the two is cheapest when I buy from Amazon next wins I guess.

The AC INFINITY fans are about the same price, but also come with speed control and a wire grill. I'm using a 120mm now and they're very good.

Had this Arctic 80mm for like 8yrs now... I'll find a use for it some day.
 

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