Keeping Robo-Tank Cool

[Rob F]

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.