HermannSW
Posts: 787
Joined: Fri Jul 22, 2016 9:09 pm

Pi 3B+ case with cooling fan

Tue Oct 09, 2018 3:25 pm

I cannot find the thread I read in this forum recently, but based on the link in that thread I spent 3$ for case with cooling fan 4 weeks ago (free shipping). It arrived today and works great. All I remember from the previous thread is that it should be connected the fan to GND/5V and not to GND/3.3V pins.

I had no case sofar and see the advantage read several times that the Pi is more secured for dangers like shorts.

It is a bit loud with fan active, but OK:
https://www.aliexpress.com/item/For-Ras ... 58854.html

In order to test the effect I made the Pi use more than 97% CPU in total by starting this command in 4 terminals in parallel:

Code: Select all

while (true); do echo foobar; done

After some time with cooling fan turned off this is what I measured:

Code: Select all

$ vcgencmd measure_clock arm
frequency(45)=818000000
$ vcgencmd measure_temp
temp=84.4'C
$

A minute after I turned on the fan I measured this (still <3% idle on all 4 cores, but CPU frequency higher):

Code: Select all

$ vcgencmd measure_clock arm
frequency(45)=1200000000
$ vcgencmd measure_temp
temp=59.6'C
$

So I think I will not turn on the fan permanently, but definitely I will in high CPU usage scenarios. The 3$ are well spent.

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Andyroo
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Location: Side of the hill in Lincolnshire

Re: Pi 3B+ case with cooling fan

Tue Oct 09, 2018 4:17 pm

That’s one heck of a find - you could not post one for that in the U.K. :shock:
Need Pi spray - these things are breeding in my house...

HermannSW
Posts: 787
Joined: Fri Jul 22, 2016 9:09 pm

Re: Pi 3B+ case with cooling fan

Tue Oct 09, 2018 5:46 pm

This seems to be same model from amazon.co.uk. Given that it is available as prime product it should arrive quicker than 4 weeks:
https://www.amazon.co.uk/MakerFun-Raspb ... B07GKV69L5
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Imperf3kt
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Location: Australia

Re: Pi 3B+ case with cooling fan

Tue Oct 09, 2018 10:50 pm

You shouldn't really run a fan directly off the 5v pin on the GPIO header as it can potentially damage your Pi

https://progeny.co.uk/back-emf-suppression/
Stop plugging your fan directly into the GPIO 5v
https://www.electronics-tutorials.ws/power/transient-suppression.html

HermannSW
Posts: 787
Joined: Fri Jul 22, 2016 9:09 pm

Re: Pi 3B+ case with cooling fan

Tue Oct 09, 2018 11:55 pm

How can back-emf be a problem when powering fan with 5V/GND pins and powering Pi with official power supply? Shouldn't the power supply eliminate any problems on the 5V rail?
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Imperf3kt
Posts: 1380
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Location: Australia

Re: Pi 3B+ case with cooling fan

Wed Oct 10, 2018 3:16 am

Because when you turn it off it can cause a voltage spike on the 5v which may damage the Pi.

At least, so I have been told.
Stop plugging your fan directly into the GPIO 5v
https://www.electronics-tutorials.ws/power/transient-suppression.html

fanoush
Posts: 375
Joined: Mon Feb 27, 2012 2:37 pm

Re: Pi 3B+ case with cooling fan

Wed Oct 10, 2018 7:25 am

HermannSW wrote:
Tue Oct 09, 2018 3:25 pm
I think I will not turn on the fan permanently, but definitely I will in high CPU usage scenarios. The 3$ are well spent.
With Pi3B+ thermal design it may also make sense to try aluminium case instead. There is one for ~7USD on ebay and I am quite happy with it. It can get slightly warm to the touch (or even very warm depending on CPU usage) so it works as intended. I only noticed that the part near wifi and sd card make wifi signal a bit worse so I removed that part (which may also help with airflow).
EDIT oh, it is even for much less now however it does not mention pi3B while looking identical.

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