BB AI cooling Addon board available

I've been running the BBAI with the  Fan mentioned in the post for about 1hour with a PRU  load , a simple python script and a tidl example(image classification) executing. temperatures are stying low (can touch heatsink easily)

Running latest kernel and firmware image.

the Fan seems to be sufficient

Edit: updated loads, temps unchanged low! very good result

Hi mayermakes, Nice work you did there.
I need to clear one thing - Is it right that fan needs to be mounted on this add-on board? Will it be possible to mount other add on boards as the height of the fan is 10mm. Also, if another add-on board is placed on it fan might not get proper airflow.
But everything falls in place if we were able to mount it on the bottom surface of this board. We just need extended pin headers i.e Height of heatsink + height of fan.

Hi,

you are right in your observations!

The fan can be mounted several ways:

1. on top of this pcb utilizing the original heatsink:(RECOMMENDED VERSION)

                     addon boards on top of the BBAI-Cooler need to provide a cutout or longer header pins for correct airflow.

2. on the bottom of the pcb;

                     A: normal header pins: the heatsink on the BBAI has to be removed so the Fan will fit inbetween the processor and the pcb(NOT RECOMMENDED , might be jiggly, less thermal mass)

                     B: longer header pins : the heatsink can stay where it is, no other changes needed

1. Will work, but troublesome for another add-on board & Fan air flow will choke. Solution Use Extended long pin headers.
2     A. Don't remove it, Fan alone will not be of much help. It will again throttle down. Solution Heatsink is must.
       B. Will Work perfectly, you can add market available BB capes without any cutout or DIY engineering. Solution Just find or make extended long pin headers which goes directly from this addon board to BB AI kit. Also DIY board with proper cut out and long pin headers in between these two boards will work.

---------------------------------------------

C. Use multiple headers.. twice or thrice.

the headers shown in the rendering are already long legged ones.
I ordered the Adafruit BB header kit, we will see if these are long enough.

"but troublesome for another add-on board"

This has been a problem for me as well as now a cape (on top of the fan cape) needs long pins so that it will not restrict air flow to the fan. i would

venture a guess that most capes do not (YET) have pins that are long enough. And, all of a sudden this thing is growing taller by leaps and bounds.

By the rendered picture above the fan cape is clearly made for the BeagleBone Black and the serial interface pins on the fan cape would probably

need to be trimmed off which is easy enough to do. Finally, the idea of using PWM to turn the power on and off on a brushless DC fan motor is not

a good one. The fan motor has an IC in it to control the motor and you are continually removing and applying power to it which is certainly not the

way it was designed to operate.

Hi,

the addon board depicted was designed to be compatible with the BBAI and the BBBlack.

For the BBAI there is a cutout to get access to its small debug header, for the BBBlack there are the pin sockets depicted-(but they need to be soldered facing down(can't render that correctly with my 3d-model yet)).

those DO NOT need to be trimmed when using the board with a BBAI, the socket just does not interface with anything on the BBAI(there is enough clearance)

The DC Fan is driven with the exact circuit 90% of 3d printers use with similar fans to control their speed. The Mosfet is overkill for the purpose but I haven't found a better fit that is available in tht yet.

Nevertheless there is of course a Risk at high pwm frequencies of burning out the internal cap or overwhelming the IC, so I suggest  limiting the use of PWM to a lower frequency or implement a Bang-Bang cycle for temp control in software instead of constant PID loops.
dc brushless fans usually die from worn out bearings or other physical damage, I never had a fan die from controlling it via pwm. If that was a common problem it would not be as commonly used as it is.

Capes that do not have stacking headers add  about 2mm of clearance with the plastic parts of the pins up from the BB headers, so they might provide enough clearance for sufficient airflow.. we will see once the PCBS arrive at my workshop.

I think its always a good idea to power and control fan and other resources via external power sources.

sure it is, you can also do this in this design.

the pin header behind the mosfet can act as external power input for the fan.

Hi in the meantime I have assembled and tested the first 0 batch of my BB-AI-Cooler addon board. and it works fine. I use it in a project to be seen on element14presents where the board is enclosed in a tight case with a lot of other electronics and only two thumb size holes to transport the air. the 25mm fan is nearly silent(depending on the load it starts a high pitched sound sometimes) the temperatures are reasonable at Kernel R119 and even with PRU cores DSP EVE, serial com to an MCU and Opencv-python running on the main arm core at once it still performs within its limits.
So I can confirm the 25mm fan beaglebone recommended is sufficient but I prfer to mount in on my addonboard to allow for a bigger volume of air to be flown over the heatsink compared to mounting it directly onto the heatsink.

I Could not test the pwm/banBangcontrols for the fan because I was not able to get the GPIOs working with anything other than PRU,but this issue may be shortly resolve as Device tree overlays get released.