if you can't wait to get a fan-addon for the Beaglebone AI : here is the link to order the pcb right away: https://aisler.net/p/SWHBYGQV
it takes the recommended Fan and allows to control it with pwm from a Pin on the Beaglebone (compatible with AI, Black, Green, Blue and Industrial Beaglebones)
it also provides an easier to reach debug header(has to be soldered the other way round as in the picture(don't know how to flip it in Kicad3Dviewer) and a debug cutout for the BBAI
Here is the BOM:
Bill of Materials
|Through Hole Resistor, 10 kohm, MCMF0W4 Series, 125 mW, ± 1%, Axial Leaded, 200 V||MULTICOMP||1|
|MOSFET Transistor, N Channel, 47 A, 55 V, 0.022 ohm, 10 V, 4 V||INFINEON||1|
|F251R-05LLC - Axial Fan, 5 V, DC, 25 mm, 10 mm, 1.412 cu.ft/min, 0.04 m³/min||NIDEC||1|
|706 - Development Kit Accessory, Stacking Header Set, Female, For BeagleBone Proto Cape||ADAFRUIT||1|
|M2.5 12 PRSTMC Z100 - Machine Screw, M2.5, 12 mm, Steel, Bright Zinc, Pan Head Pozidriv||TR FASTENINGS||1|
|Board-To-Board Connector, Vertical, 2.54 mm, 3 Contacts, Header, 2211S Series, Through Hole, 1 Rows||MULTICOMP||1|
|Board-To-Board Connector, 2.54 mm, 2 Contacts, Header, 2211S Series, Through Hole, 1 Rows||MULTICOMP||1|
|Board-To-Board Connector, 2.54 mm, 6 Contacts, Header, 2211S Series, Through Hole, 1 Rows||MULTICOMP||1|
|Board-To-Board Connector, 2.54 mm, 6 Contacts, Receptacle, BG095 Series, Through Hole, 1 Rows||GCT||1|
This is also to be released alongside a future element14 presents episode , and I see the need for people to use it so please try out this prototype at your own risk.
The first 0 batch has not yet arrived in my workshop so I can't promise it works perfectly right now.
The fan can be mounted in 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 (RECOMMENDED VERSION)
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.
On the BBAI I suggest leaving the Fan on full on either in software or by setting the jumper to on.
Message was edited by: Clemens Mayer Added some clarifications from the comments.