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Keeping Robo-Tank Cool
#1
Hi, thought I would start a thread about heating issues, feel free to post your ideas and results. Thanks to those for pushing me to get this done, I should have done something long ago as many have asked about it but I kept putting it off. One reason is I didn't want to alter the size of the case and didn't really see a way around it but lucky for me a 40mm x 40mm x 10mm fits inside the case nicely so I'm going that route for now but definitely open to ideas.

These tests are based on the following conditions, I will post results for Pi 4 as well.
  • 74° F ambient temperature
  • Raspberry Pi 3
  • OS lite (no desktop - no display)
  • Noctua NF-A4x10 FLX 12v Fan
There's a DB18B20 temp sensor soldered to the board sitting between the Pi and controller board used to monitor temperature of case.

I'm using the following command in the Pi terminal to get the temperature of the Raspberry Pi.

Code:
/opt/vc/bin/vcgencmd measure_temp


Results without cooling
  • Case temperature = 105.1° F
  • Pi temperature     = 128.6° F
Results with cooling - Lid 1
  • Case temperature =  83.5° F
  • Pi temperature     = 101.4° F
Results with cooling - Lid 2
  • Case temperature =  80.9° F
  • Pi temperature     =  99.6° F

I strongly feel a different fan will do better than the Noctua. I bought that thing years ago and was very disappointed when I powered it up, my thought was no wonder it's quiet it moves very little air. I wasn't able to use it for a light so it went in a box until now. The nice thing is it comes with screws, that made mounting this a breeze.

When the fan was turned off it heated back up to max within 10 minutes so best to run 24/7. On next set of boards I'll be adding a 2 pin socket to plug in the fan.

This is where the case temp sensor sits.

   

This is Lid 1, it just has a vent and holds the fan.

   

This is Lid 2, I added some guides to direct the air towards the Pi. The guide sits about 2-4mm about the board so lots of air can still escape but did help some.

   

This is basically where the fan and guide sits, you can also see the case temp sensor. I put the fan there so it can also cool 4 of the DC port mosfets.

   

These are the legs, 7mm tall but will likely drop to 5mm if it doesn't affect the numbers. The circle on lid is where the screw comes through, if it pushes out of that block it's too long, one leg is over the Pi so could be deadly, other 3 doesn't matter. You could also get nice rubber feet at hardware store so it doesn't slide.

   

All sealed up. I will be tapering the holes for screws so they should be flush and look better.

   

I'm going to further refine the lid and try to improve, I'm sure it can be brought down more. I'm going to try a lid on the guides to get more air to Pi but add an escape so some air can still get to the DC ports. Then I'll work on tips to go under and over Pi better.

Here's some Amazon affiliate links for fans.

This is the one I'm using.

https://www.amazon.com/gp/product/B009NQLT0M/ref=as_li_qf_asin_il_tl?ie=UTF8&tag=5302020-20&creative=9325&linkCode=as2&creativeASIN=B009NQLT0M&linkId=00c3ad51d70e25876c84939bcc135e4c

This one might do a better job, runs at 6,200 RPM vs the Noctua at 4,500 RPM but need to hunt down screws.

https://www.amazon.com/gp/product/B07MCZKT18/ref=as_li_qf_asin_il_tl?ie=UTF8&tag=5302020-20&creative=9325&linkCode=as2&creativeASIN=B07MCZKT18&linkId=d43b1544c5b141e8772656f452213c09

You can probably find some high speed types at local computer shop too, just needs to be 40mm x 40mm x 10mm. 

I won't post files just yet as I only have lid for Pi 3 older controller version but it won't be too long.
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#2
Hi Rob, Looks good so far, but could you push it a little further, e.g 80° F ambient temperature? It would also be good if the case could accomodate a heat sink for the Pi's chip.

As I've mentioned before, I prefer a single source to simplify the logistics; please consider adding the heat sink, feet and screws as a package as optional items.
José
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#3
Still working on it, making some revisions now, not sure how low it will go. Heat sink would be nice but problem is there's no space between Pi and board, to get more space a taller 40 pin header is needed and I haven't seen anything like that, they're all a standard size. You can get one to stack which would double the spacing but it's more connections that can corrode. Those headers are the weakest point over time. If I could find a header a few mm taller a heat sink would fit. Before I go down that path I'm going to see how low I can bring it with just the fan, I think if the air get to where it needs to go it should drop more. That header is what's blocking the air from getting under the Pi to the chips.
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#4
Well I added a lid to cage in the fan but that didn't help as much as I hoped. First attempt was just a lid which had no effect so I added a wall so air only comes out one section, it did drop a little.

Results with cooling - Lid 3
  • Case temperature =  79.6° F
  • Pi temperature     =  96.6° F
The fan housing can be printed as one piece and the lid could have slots it pushes into keeping things simple. Might try opening other end a little to see if helps but I think it's near its limit. 

Then I started wondering what temps do people get with heat sinks and went searching but couldn't really find much. 

Officially Raspberry Pi says a heat sink isn't required. 

https://www.raspberrypi.org/documentatio...ance-temps

Apparently the max temp is 185° F and the Pi starts to throttle down at 180° F to keep it from over heating although that link didn't mention it.

In my current conditions the fan did bring it down nearly 30° which isn't too bad. In a few months it'll be 80+ here so I can see what it gets to then. 

One thing I forgot to mention is the lid stays 100% cool so it wouldn't warp.

The Pi 4 definitely runs hotter and is the bigger issue, I'm going to switch to it and see what I get.

Overall it's a balancing act for me, at this time I think I have to go with the internal fan and no heat sink for a few reasons. I did look around for taller headers but all seem to be 3.5mm or 8.5mm. 

First I'm stuck printing cases for whatever I go with. Bottom line heat sink means tall case which could increase print time by up to an hour over the extra needed for the lid. I'm already always waiting on the printer. I feel the fan is needed as the lid can warp and that is definitely solved. Then packaging, the box I use just has enough height to stack the power bar and controller with space for padding above and below, any taller and I lose the top or bottom padding, as crazy as it might sound I would feel 10mm. The next standard size larger box means higher shipping and extra packing as it's more than I need.

I've used those header extensions on my old controller to stack an Arduino and Ethernet board on both sides of a board. The pins on extensions are thinner than standard header pins meaning poor contact. Many times I had to tell people to bend the tip of the pin so it would make contact plus an extra 40 points to corrode. I could use just the extension and solder the long legs in board and have it hover to the necessary height but the pins are flimsy so good chance plugging in the Pi will collapse the pins, if you aren't careful it's almost certain to happen. Either way it also means I need to cut 40 pins for every board I assemble as they will stick out of the board too much. Overall it's ugly and won't work, ok for one off but not production.

Going the fan route all it requires is redesigning the lid and only adds about 30 minutes printing time and does have definite benefits. Easy for anyone to install the fan and doesn't require any extra labor on my side which is what allows me to keep prices low. So yeah it's not as easy as it might seem. I'm kind of impressed the actual Pi temp dropped considering the fan moves little air, my original tests I didn't check it, when I realized that I was worried only the case temp dropped but it's a definite improvement. 

   
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#5
hi robo it looks quite interesting or even if you have to try a radial fan on hand.  I don't know who could produce more air


Attached Files Image(s)
   
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#6
(03-10-2021, 05:28 AM)loksik.lubos Wrote: hi robo it looks quite interesting or even if you have to try a radial fan on hand.  I don't know who could produce more air

Thanks, I searched for one like that but couldn't find the correct size, most of those are 20mm thick which is too much.
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#7
(03-10-2021, 06:52 PM)Rob F Wrote:
(03-10-2021, 05:28 AM)loksik.lubos Wrote: hi robo it looks quite interesting or even if you have to try a radial fan on hand.  I don't know who could produce more air

Thanks, I searched for one like that but couldn't find the correct size, most of those are 20mm thick which is too much.

I guess I didn't search good enough, found some 40x40x10. Going to order, should have on Friday and they even come with mounting screws.  K05164 They could be a little noisy as they spin at 7000 RPM but they could be slowed down.

https://www.amazon.com/gp/product/B07MS1DBZ7/ref=as_li_qf_asin_il_tl?ie=UTF8&tag=5302020-20&creative=9325&linkCode=as2&creativeASIN=B07MS1DBZ7&linkId=e3591c8e8f8e9f9a9279c4b1ad972d0e
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#8
I got those fans, the output can't be compared to the Noctua, it's much better but you guessed it, it's a lot noisier. If controller sat in a cabinet the noise would be fine but I wouldn't want to sleep next to it. Quieter than what's on my printers but still loud.

I haven't made a lid yet but just holding above the Pi the temp dropped to 90° F. 

Now I don't know what to do, I much prefer the Noctua but this style definitely does a better job. Of course the mounting holes are different size and spacing so it's one or the other.
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#9
My vote goes for the noisier but better fans; I'd rather suffer some noise than have an RPi fail due to overheating. If you make the extra cooling feature optional, people can make up their own minds. Besides, this is version 1. I bet there will be better fans in the future.

Thanks,
José
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#10
(03-15-2021, 03:26 AM)JFReyes Wrote: Môj hlas je pre hlučnejších, ale lepších fanúšikov; Radšej budem trpieť hlukom, ako by som mal zlyhať RPi kvôli prehriatiu. Ak nastavíte voliteľnú funkciu dodatočného chladenia, ľudia si môžu urobiť vlastný názor. Okrem toho je to verzia 1. Stavím sa, že v budúcnosti budú lepší fanúšikovia.

Vďaka,

anti-vibration mounts


https://www.amazon.ca/Noctua-NA-SAV4-sil...B071W6KYCG
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#11
I think at 30c you'll have the coolest Pi in town haha. I've been running my Pi over 6 months at 50c+ 24/7 and it's fine so now being under 40 is hugh IMO.

The noise from the fan is air moving, not really from vibrations.
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#12
Hi Rob:

Any news on this endeavor? Please let us know...

Thanks,
José
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#13
Hi Jose, the last few nights I've been thinking about posting, either way I'm not happy that's why I've been putting it off.

Caged fan is great as no vent is needed on bottom of case or legs so it's tempting however due to the noise I've decided to go with the Noctua. I had the caged running for a couple days but even I couldn't stand the noise and I can foresee lots of people agreeing. If I drop the voltage the noise drops but in the end the Noctua is still quieter and moves the same air at that point.

With that said if you don't mind the noise I can certainly print you a case to fit it. The lid only needs 4 holes to mount the fan so it's no problem at all. I'll probably offer a file for this type of lid anyways in case people want that extra few degrees but I'll advertising for the Noctua.
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