Beaglebone Ai Heating Issues

Hi ipv1 ,

I  looked into this and this is a known issue:

BeagleBone AI - Frequently Asked Questions (FAQ)

They recommend adding a larger heat sink and cooling via fan.   

Hi ipv1 ,

I  looked into this and this is a known issue:

BeagleBone AI - Frequently Asked Questions (FAQ)

They recommend adding a larger heat sink and cooling via fan.   

Further more the message of '95degC' shows that the BeagleBone AI is not running the latest kernel, make sure it's updated via the custom script:

• sudo apt-get update
• sudo apt-get upgrade -y
• sudo apt-get dist-upgrade -y
• cd /opt/scripts
• git pull
• sudo tools/update_kernel.sh

My investigations showed much the same. My questions are:

1. How was this not caught during testing ? Some minor overheating might be missed but shutting down as described on many of the comments makes it obvious that there is a serious problem.

2. This is happening when you are only running the OS on the ARM Cortex-A15 cores.  What happens to the temperature when you start using some mixture or all of the ARM Cortex-M4s cores,

      DSPs, EVEs and PRUs too?

3. If it needs a bigger heat sink and fan just running the OS why doesn't it HAVE a bigger heat sink and fan (see 2.).

After reading the earlier comments in this discussion and checking for other comments on the web I hopped over to Ebay and bought a couple of 25mm fans. The heat sink on the AI is 25mm and

it looks like there are threaded holes to attach the fan with. I'm not sure how you mount a larger heat sink  other than a adhesive thermal pad or thermal epoxy. There is an adhesive thermal pad

between the heat sink and SoC but I'm not a big fan of thermal pads and in this case I would much rather have a heat sink that uses mount points on the PCB and a wafer thin layer of quality thermal

paste.

It also looks like it could use some serious thermal management on the OS side. I'll give them the benefit of the doubt and hope that somebody is looking into this.

Mainly active cooling helps to reduce the temperatures when it's under load.

There may be some work that can be done with cpufreq under linux to help thermal throttling, though this is at least possible to manage the board to reduce the speed down to 500mhz from the 1.5Ghz.

The heat issue was found during testing.  See section 3.1 from the following:

https://github.com/beagleboard/beaglebone-ai/wiki/System-Reference-Manual

"You may find it helpful to connect a fan to BeagleBone AI. This one has been used by Alpha testers."

There is also a link for the Heatsink.

Christopher,

Yes I know when active cooling is needed. But since they will be under load to do real work then active cooling and software thermal

management will always be needed. And again, so far this is not even close to running it under full load. There are two dual core

Cortex-M4s, two 64 bit DSPs, four EVEs, and four (or 2 dual core?) PSUs that from what I've read aren't even being used and it

still gets so hot that it shuts down.

Jon,

If it was found during testing, why wasn't it fixed? As shipped many appear to not work at all without active cooling so this is not a minor

issue. The heat sink in the link is .25" taller and has more fins (greater surface area is good) but has no mount points for a fan and no

way to mount it other than adhesive thermal pad or thermal epoxy. Given the scope of the problem I've seen under the relatively light

loads reported so far I don't see how this is anywhere near enough to fix it.

Why it wasn't fixed? Ask Jason Kridner.

I would like to get the FAN Cape he is using in this vid:

https://www.youtube.com/watch?v=v3_hNBJbqME

Given what I've seen so far if i thought I'd get a reasonable explanation from Jason i would.

Cripes, that's a big fan. It does resemble what I think will be necessary to fully fix the problem. I just wonder where the

air will come from/go to when a HAT is on top of it since the fan is almost as tall as the GPIO headers. Long pins on the

HAT no doubt. And with a fan that big you are talking about fairly substantial power required to run it. Maybe use one of

the AI's PWM channels to help keep it in check?

Hi Christopher,

As I understand (I really don't know for sure but it seems to make sense) as you say, without the active cooling, it would throttle more, especially if it detects no cooling is attached. It's likely some heat management will be needed to run all cores and accelerators/EVE/DSP etc. at full load, and the software image could eventually detect when a fan cape is attached, to allow everything to run at a sustained top speed. But, since they knew that people would also want to run it immediately (i.e. without needing additional heat management), there is a small heatsink already mounted, and with threads to attach to a custom solution if required.

The software could detect the heatsink cape easily, since they still use that EEPROM thing I think? (I've never owned a BBB cape, so never checked if the software tries to read it at startup).

Anyway the thread is 3mm, and seems to be on a 20mm square, so is kind-of compatible with 25mm fans since they have their holes on a 20mm square too (although some of those have slightly smaller than M3 holes - so either a custom bracket could be used, or force the screw through the fan anyway, or use glue or tape, since the fan is lightweight).

I'm not 100% sure what I'm going to do, but most likely I'm going to sandwich mine between two sheets of acrylic, and have the fan attached to the top acrylic.. or wait for the fan cape, but it's hard to wait : )

A 40 or 50mm fan will fit between the headers, so that could be an option.. or try a flat heat pipe+heatsink, I'm thinking if there was an alu plate screwed on then the flat heat pipe could fit between it and the existing heatsink, and then going off to a heatsink on top of the acrylic.. that way there's no large heatsink pressing on the board.

The trick is to find that Cape Fan.  I have not been able to locate it.

From the SRM link I provided earlier, the suggested fan is one that screws to the top of the heat sink; X15FANKIT.  The Cape version seems like a cleaner option tough but certainly would draw some juice.

As I understand, the fan cape still isn't released (just from grapevine so I could be wrong). It does look nice, in that video.

The X15FANKIT fan has 2.8mm holes (going by the part name in the photo of the fan), maybe they just suggest forcing the M3 screws through.

I've been searching at home to look for a suitable fan, but only came up with a 25mm fan (also with 2.8mm holes, but M3 could be threaded through it I reckon) and a 50mm fan, and 50mm is too big to fit between the connectors. Maybe this 5V 40mm fan5V 40mm fan could be suitable (i.e. if the BB-AI has some acrylic sheet or something mounted on top), it has 80mA current consumption.