Huxley 12cm outer-edge fan mount

by drdpj, published

Huxley 12cm outer-edge fan mount by drdpj Oct 20, 2012


Printed indieflow's design but no dice with the fan I had! These grip a 12cm cooling fan on the outside edges if it has solid straight through screw holes (such as the cheap brushless fans from maplin).

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To add a little, I looked up a heatsink very similar to yours, That would have a thermal resistance of 6,5°C/W
The TO-220 package (from the lm7812 datasheet) has a 5°C/W, that would then add up to a 11,5°C/W instead of the 65°C/W junction to air.

This time setting ambient to 50°C, probably the highest it would ever see, that would leave you at 78,175°C with a 350mA load. So yeah, heatsinks are fucking magic :P.

I'd say that you'd probably want to have that sink on there. Assuming worst case here. Running the highest current 120mm fan that I could find in my stash, it ran 350ma at 12v/2600 rpm. With the huxley, that has a 19v PSU so the linear reg would need to drop 7 volts. 7v * 0,35A = 2.45W

Looking at the datasheet of an LM7812 (I happened to read up on the one from fairchild) the thermal resistance, junction to air is 65°C/W

With a generously low ambient of 25°C the junction temperature would end up at 2.45*65+25 = 184,25°C way way over the 125°C max.

Changing the fan to a 200mA fan, would leave us at 116°C, just 9°C short of the absolute max rating.

tl:dr; Keep that sink on ;)

great! prints are now so much better!

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Print the long and short files, affix as shown in the photo. I would recommend running the juice from a reprappro huxley with melzi (19V) through a 12V regulator (L78S12 or equivalent). Wire into the fan socket on the melzi board and you can then control it automatically during printing using settings in slic3r or skeinforge. Tools are obviously only required if you'd messing with regulators!

After a bit of use, I recommend sticking a big heatsink on the voltage regulator (2nd picture). This not only stops the fan slowing down as things heat up but also makes it look a bit more badass. If a fan can look badass, which it probably can't.


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P373 on Jun 19, 2013 said:

great! prints are now so much better!

smartroad on Dec 2, 2012 said:

Turn the regulator upside down and have its tab in the air flow. That would probably cool it without having to add a heatsink :)

drdpj on Dec 11, 2012 said:

You're right. I think I just wanted the excuse to pimp my fan :D