USB-powered fan


16 posts
by chrispiduc » Tue Jul 17, 2012 7:10 am
Hi all,

I'm sure most of you are going to roll your eyes because fans are not necessary for the pi, but I didn't intentionally start out with it in mind, OK? ;-)

Yeah, mine has got aluminium heatsinks stuck with thermal tape as well... 15 years of overclocking Intel/AMD CPU's has got me into bad habits ;-)

I was clearing out the garage at the weekend and had a lot of old computer stuff, which included various USB leads. I figured "what the heck" and stripped one back just to see what was actually inside.
Beyond the protective weave and foil, there are four wires - two for data, the red and black for power.
Rummaging around I found an old hard-drive cooler and remove one of it's fans - which was smaller than my pi case and therefore I figured might be mountable. It's rated at 12V, though I guessed it'd take much less due to it's size (USB is 5V I think, so assuming there was enough juice to start, it would - just not at 100% speed). That also had red and black wires.
I broke out the soldering iron and some insulation tape - then twisted and soldered the wires together (blue-black, red-red obviously) and just removed the USB data wires as best as I could.
Plugged the USB lead into my powered USB hub and bingo - I have airflow :-)
Just need to get the dremel out, make a hole in my case, and secure the fan now.

It was an interesting experiment :-)

I'm sure others have found a better way of getting power (GPIO pins presumably), but I amused myself for 25 minutes :D
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by Lob0426 » Fri Jul 20, 2012 6:47 am
We can never discount the Amusement factor. :lol:
Remember the USB's on the RasPI only can put out 140ma. Check your fan to make sure it is using less than that. Or it will not be running all of the time, only when the fuse hase cooled. :cry:

I am fighting the upstream also and have heat sinks on my SoC, LAN9512 and RG2.
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by chrispiduc » Sun Jul 22, 2012 8:40 am
Running it off a quality powered hub so no issues with power (yet?).

I can also confirm that splicing two USB leads together and then powering a fan works fine. That's presumably 10v, and has enabled me to use a monster (compared to the size of the pi) fan to run completely off the USB hub.

I'm running everything from the hub (wired keyboard/mouse and 2.5inch HDD) and using ethernet - without overvolting (and using the small fan* I mentioned previously) I am stable at 933Mhz CPU, 475Mhz RAM, and 288Mhz GPU. Played Quake 3 for about 25 minutes yesterday without any issues whatsoever.

Now I'm not sure if I'm just really, really lucky with the amount of play within my pi, but I am sure pre heatsinks and fan it was stable at 900/440/260. I'm afraid there isn't a more empirical test - I'd be worried about removing the heatsinks now :( However, there does appear to be some gains in stability from an improved cooling solution (though I wouldn't expect any improvement beyond this - though if someone wants to try a water cooling solution please post :lol:).


*The hard drive cooler I mentioned was like this one: http://www.amazon.co.uk/Inch-Hard-Disk-Drive-Cooling/dp/B000VJEBAA/ref=tag_dpp_lp_edpp_img_ex/275-9924333-8916355. I am sure that better fans can be bought individually though.
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by itimpi » Sun Jul 22, 2012 10:33 am
chrispiduc wrote:I can also confirm that splicing two USB leads together and then powering a fan works fine. That's presumably 10v, and has enabled me to use a monster (compared to the size of the pi) fan to run completely off the USB hub.

No - this does not increase the voltage - it increases the maximum current available from 500mA to 1A.
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by chrispiduc » Sun Jul 22, 2012 10:11 pm
Thank you for the clarification itempi - as is probably obvious, I am interested in learning more about electronics with the pi, knowing nothing about the area at the moment (with PCs you can buy kit off the shelf - there isn't anything AFAIK for the Pi yet, hence why I've posted the above :-) )

Cheers again,

chrispiduc
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by redhawk » Sun Jul 22, 2012 10:30 pm
Talking of USB fans I have my PI sitting on a netbook cooling fan I bought from Poundland.
It's not particlar powerful (runs off the PI's USB) but sufficent for cooling down the RAM and CPU.

Richard S.
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by AndrewS » Tue Jul 24, 2012 11:02 am
chrispiduc wrote:with PCs you can buy kit off the shelf - there isn't anything AFAIK for the Pi yet, hence why I've posted the above :-)

There's no off-the-shelf "cooling kits" available for the RPi, because the general consensus is that the RPi doesn't need to be cooled, and the fan/heatsink/etc. threads are just red herrings. But I wouldn't be surprised if something pops up on ebay... :|

There are plenty of RaspberryPi-specific accessories though :) e.g.
http://elinux.org/RPi_Expansion_Boards
http://elinux.org/RPi_Cases
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by khh » Thu Jul 26, 2012 12:28 am
itimpi wrote:
chrispiduc wrote:I can also confirm that splicing two USB leads together and then powering a fan works fine. That's presumably 10v, and has enabled me to use a monster (compared to the size of the pi) fan to run completely off the USB hub.

No - this does not increase the voltage - it increases the maximum current available from 500mA to 1A.

That depends on how you do it. A If you serial connect them you get 10 V, 500 mA and if you paralell connect them you get 5 V, 1000 mA.
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by AndrewS » Thu Jul 26, 2012 1:49 pm
khh wrote:That depends on how you do it. A If you serial connect them you get 10 V, 500 mA and if you paralell connect them you get 5 V, 1000 mA.

That works with batteries, but it doesn't work with USB leads :!: If you try "serial connecting" USB power leads, you'll be directly connecting the +5V line to the GND line (i.e. creating a short), which will blow a fuse somewhere (on the RPi it would blow the polyfuses, which then need a long time to cool down again).
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by khh » Thu Jul 26, 2012 3:00 pm
AndrewS wrote:
khh wrote:That depends on how you do it. A If you serial connect them you get 10 V, 500 mA and if you paralell connect them you get 5 V, 1000 mA.

That works with batteries, but it doesn't work with USB leads :!: If you try "serial connecting" USB power leads, you'll be directly connecting the +5V line to the GND line (i.e. creating a short), which will blow a fuse somewhere (on the RPi it would blow the polyfuses, which then need a long time to cool down again).

Ah, yes, it wouldn't work if they shared ground. Which they do. Sorry, should have thought of that.
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by AndrewS » Sun Jul 29, 2012 11:27 am
AndrewS wrote:
chrispiduc wrote:with PCs you can buy kit off the shelf - there isn't anything AFAIK for the Pi yet, hence why I've posted the above :-)

There's no off-the-shelf "cooling kits" available for the RPi, because the general consensus is that the RPi doesn't need to be cooled, and the fan/heatsink/etc. threads are just red herrings. But I wouldn't be surprised if something pops up on ebay... :|

Well that didn't take long ;) viewtopic.php?f=60&t=12561
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by Lob0426 » Sun Jul 29, 2012 3:58 pm
AndrewS wrote:
AndrewS wrote:
chrispiduc wrote:with PCs you can buy kit off the shelf - there isn't anything AFAIK for the Pi yet, hence why I've posted the above :-)

There's no off-the-shelf "cooling kits" available for the RPi, because the general consensus is that the RPi doesn't need to be cooled, and the fan/heatsink/etc. threads are just red herrings. But I wouldn't be surprised if something pops up on ebay... :|

Well that didn't take long ;) viewtopic.php?f=60&t=12561

I still want to know why you believe all of the RasPi "cooling" threads are red herrings. Not one of them has ended in an attemp to sell any equipment. Not one of them has made any false claims as to life span or damage to a RasPi. None of them have been anything but mostly intelligent discussion about adding cooling to a RasPi. For those threads to be red herrings they would have to allude to grievous damage to the RasPi if it was NOT cooled and most likely would lead into a sales pitch. Did not happen, even in that thread you just linked.

I hate too take you to task over it, but this is at least the second time that you have claimed red herring. :roll: Need some evidence or discussion that your claims are true please?
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by AndrewS » Sun Jul 29, 2012 5:25 pm
Lob0426 wrote:I still want to know why you believe all of the RasPi "cooling" threads are red herrings.

I hate too take you to task over it, but this is at least the second time that you have claimed red herring. :roll: Need some evidence or discussion that your claims are true please?


Based on what JamesH/Dom/Gert (who all work for Broadcom) have said previously...
e.g. viewtopic.php?p=108595#p108595

If you want to fit fans / heatsinks / whatever that's up to you, but in the volumes that the RPi is being produced, don't you think they'd come pre-fitted if they were really necessary :?:
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by Lob0426 » Sun Jul 29, 2012 6:14 pm
A red herring is a figurative expression in which a clue or piece of information is or is intended to be misleading, or distracting from the actual question.
Red herring may refer to:
Red herring (fallacy), the informal fallacy of presenting an argument that may in itself be valid, but does not address the issue in question.

There is no need for cooling under the foundations intended use of a Raspberry Pi. Most discussions were for RasPii used outside of the foundations intended use e.g. High temperature, Overclocking, vehicle mounts and extended use, etc.

No information in those discussions was false. The discussion was about cooling the RasPi. It was mentioned in most if not all those threads that many considered cooling unneeded, so not misleading. The Topic was cooling so was not distracting from the actual question. It may be considered that the argument is invalid except that was the topic, whether it was invalid or not.

The reason I have brought this up is to promote open discussion. Whether cooling is needed or not really is up to each person. If they ask a question and honest discussion is carried through, then there is no need for labeling. If the discussion had lead to false information being presented then there would need to be a correction in the thread. As I said before I have seen nothing but honest discussion in these threads and no false information presented. If false information was presented in any of them I would have been the first to cry foul!
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by AndrewS » Sun Jul 29, 2012 6:53 pm
Lob0426 wrote:Red herring (fallacy), the informal fallacy of presenting an argument that may in itself be valid, but does not address the issue in question.
....
The reason I have brought this up is to promote open discussion. Whether cooling is needed or not really is up to each person. If they ask a question and honest discussion is carried through, then there is no need for labeling. If the discussion had lead to false information being presented then there would need to be a correction in the thread. As I said before I have seen nothing but honest discussion in these threads and no false information presented. If false information was presented in any of them I would have been the first to cry foul!

Apologies if I've been giving off the wrong impression. Myself and Lob0426 usually get on well in these discussions ;) viewtopic.php?p=108518#p108518
When I was calling cooling a red herring, I wasn't implying that anyone was providing false information.

The (possibly wrong) impression that I get from most of these "cooling discussions" is of people who are used to sticking super-duper CPU coolers/case fans/etc. on their "gaming rig" PCs, getting 'scared' that the RPi doesn't have any active cooling, and so fitting heatsinks "out of instinct" :?
But I'll try to steer clear of these discussions in future...
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by Lob0426 » Mon Jul 30, 2012 4:29 am
Alright @AndrewS I am through busting your chops now.

Just wanted get that cleared up. Someone might think that we are just trying to get them to buy stuff they really do not need. The Foundation says The Raspberry Pi runs just fine without adding any additional cooling. Some of us are just hard headed ex/future Overclockers that think different!

Edit: It was 92F (33.33C) here today. Forgot to leave the windows in the Corvette down a little. It said 148F (64.44C) inside. This is the average Temperature here at this time of year. Might have been a bit hot If I had a RasPi as a car computer in there. RasPi fine, SD card melted (not really). 8-) ;) I have seen as low as -34F (-36.4C) here and as hot as 106F (41C). Have you ever had the hydraulic clutch in your toyota go down but won't come back up, thats cold. :shock: The temperatures vary wildly sometimes as we are at 4250ft (1295.4M) above sea level here. I have seen snow on the Fourth of July and had 100F temperatures two days later. :?
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