These are the old notes from the olde web site , left here for reference only.
on project Gamma - Cooling
It is pretty clear that
there are two alternatives for cooling this beast, forced air or water. Let's look
at them separately.
Forced air is the "traditional" approach. Each
EB104 board gets mounted on a heat spreader, made of copper, to quickly get
the heat off the parts. CCI sells a suitable spreader for $24. I looked into just buying pieces of copper from McMaster Carr, but it appears to be much
more expensive to do that. Once you have a heat spreader, then you need a
heat sink. CCI sells a 6.5" x 12" x 1.6" heat sink (their #99 ) for $22. This sink is 54 square inches per inch of surface area, and has a thermal dissapation
factor of .79 . It weighs 3.6 lbs. I spoke with them on the phone, and they
claimed that this sink was sufficient with forced air at an unspecified volume/rate
to cool an EB104.
I'm concerned that there isn't much in the way of
thermal discussion on the CCI website, and the person that I spoke with on the
phone didn't seem too technical. Insufficient heat disappation would be a
great way to ruin this project...
Aavid is one the leading manufacturers of heat sinks. They make a sink (#61785, extruded profile) that is
10.78" x 3.77" x whatever length you want. Thermal resistance at
18" length is .31 , and its surface area in square inches per inch is 92.1 . However, it weighs
16 lb/ft which might be an issue :-)
The Aavid #62725 sink, also extruded
profile, is 9.75" x 2.28" by length, and weighs 7.1 lbs/ft. Budgetary price from Arrow
is $107 for an 8' bar - part number 627251F0000. At 18" length its thermal
resistance is .29 . You can see its thermal properties here.
From the graph in the lower left of the page, it appears that with a 100 CFM fan in a channel 3" high by 10" wide
(assuming that we box in just this one sink) we get 2.438 meters/second of
airflow, which would drop the sink temperature to less than 25 degrees C above ambient. If
you believe that the ambient air is in the range of 40 degrees C, that gives you
a 65 degree C heat sink, which is fine.
On to the question of the mechanicals. I think we need a commercial enclosure
so that everyone can easily repeat the mechanical design. One option is the Basic Kit 19" rack
mount enclosure from Techmar . They quoted me $165 for an 8.5" usable height by 24" depth by 16.75"
usable width rack mount all aluminum chassis. It is available with perforated bottom,
top, or sides.
Mouser carries BUD aluminum
rack mount chassis. The 8.5" high by 22" deep ones are $83 quantity one without top or
bottom. The top/bottom is $33 each, so the total equivilant cost (to the Techmar) is $149. That
doesn't include handles. Internal chassis shelves of various widths are
Another enclosure option
is Protocase . They make "custom" cases - you pick a style (U shape or rack
mount seem to make the most sense for us), specify cutout locations and the number and locations
of captive connectors, and they make up the enclosure for you. They quoted me prices of around
$240 for a suitable (24" x 17" x 8" U shape with 10 cutouts and 10
captive fasteners) enclosure. The big benefit here is that we get the mounting holes for
the display, buttons, connectors, etc. cut to our specs - and thus we get a very professional look.