Tuesday, June 16, 2009

1U Power Supply and Case Cooling

With the first version, the standard ATX power supply was one of the biggest consumers of space. So for this version, I went for a 1U form factor power supply.
Dimensions around around 200mm x 100mm x 40mm. Sizes vary a little, but these are pretty standard.

The first start up of the power supply brought home an important point - the inbuilt 40mm fans, running at around 9000 rpm are ridiculously noisy. Even brought some inquisitive people into the work room enquiring "whats that noise !!! ??? "

So firstly - the standard fans are out !!

Going back to the original thoughts on the design...

There was to be some 80mm or 100mm fans installed underneath the power supply, sucking air out of the case and exhausting out through the underside of the overall box. To do this means that I needed to excavate some large holes into the power supply case.
So I got out all of the noisey tools I had (drills and sheet metal nibbler), and commenced lining up, marking and cutting. The results were some fairly rough cuts - but generally somewhere near the mark (I probably could have done just as well with a tin opener - if I could get the leverage :-))

I also set to and cut out the same kinds of holes in the bottom sheet of the overall case - again, rather crude attempts at metal work... Anyway - that is where the work stopped for the weekend...
Over the following week or so, I slowly become more and more convinced that this really was not the best way of doing things...
It doesnt seem right to have to butcher the case of the power supply, opening up the potentially dangerous innards for unsuspecting fingers to touch...
And also, venting the exhaust from the case out through the bottom - didnt sit comfortably.
So I went for a re-design.

With the redesign, the main goals were to use the larger 80mm fans, not have to cut up the 1U power supply case, and not to exhaust the air out through the bottom of the case. The result was the following

Basically the 80mm fan gets mounted at an angle, around 40 degrees. It blows air out through the power supply. The intake air gets drawn in across the top of the mother board. Of course this will require some thinking on how to build a duct to push the air through the power supply - but should be do-able :-)
Another advantage with this design, if someone spends big dollars on a quiet 1U power supply, then potentially the existing 40mm fans may already be quiet, and hence dont need replacing. The airflow in that case still remains the same.
Viewing from the back of the case

Air will either be sucked into the case from the back, below where the hotter air exits, or maybe through some holes in the base of the case. TBD.
This cold intake air gets pulled past the hard disk to provide a bit of cooling, and then flows around the edge of the mother board and across the top - helping general cooling. Then it gets pushed out through the power supply.

So translating this design into something concrete. Firstly the mounted power supply.

For the 80mm fan, I made a simply angle bracket, and mounted the fan using standard rubber mounting feet at the top. For the bottom edge, will probably just insert some cut-off rubber mounting feet.

Which all fits together as follows

Many more things to be done to finish these bits off...
Need to work out the ducting, both for pushing air out through the power supply, and for bringing in the fresh air, either from the back and/or through holes in the bottom of the case. Also need to patch up the nice holes cut in the power supply case :-)

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