I purchased an inexpensive snap-together acrylic case for my Raspberry Pi from a seller on eBay. Overall I was happy with the case, but although this case has holes for passive air circulation I noticed that after running the Pi in the case that some of the chips were running a bit warm (even with heat sinks installed). Since this Pi will be running a web server 24/7, I decided to design a new top which accommodates a small (quiet and low air flow) cooling fan.
NOTE: When installing and setting up the software I referenced the following 2 instructables:
I primarily referenced the first instructable, but I used nginx rather than Apache server software and I referenced the second instructable for the nginx installation and setup.
NOTE: Since I made this project, I have found several cases that are available on eBay for the new Raspberry Pi2 and B+ that include a small fan. The Pi2 uses a 900 MHz ARMv7 quad core whereas the older Pi uses 700 MHz ARMv6 single core
Step 1: The Original Case
This picture shows the original case. It can be snapped together (no glue or fasteners are needed) in a few minutes.
Step 2: LibreCAD Design of a New Case Top
LibreCAD is a free (and very capable) 2D CAD application that runs on either Windows, Mac OS X and Linux (so it is possible to run LibreCAD on the Raspberry Pi to redesign its own case). I used a caliper to take measurement from the original top. I did not include the I/O access slots from the original case since I will not need these for my application of this Pi. I also did no include the hinge tabs from the original case. The new top is just be held in place by gravity and it can easily be removed if needed.
I have attached the dxf file for the new top. This file can be used as input to a laser cutter. I don't have my own laser cutter but I have a friend who has one (a 60W CO2 laser cutter). He used 1/8 inch thick (~3 mm) acrylic (scrap) material to cut the new top.
NOTE: LibreCAD can be downloaded here: http://librecad.org/cms/home.html
NOTE: In LibreCAD, the smaller holes must be places on a different layer than the outline cut so that the laser cutter CAM software can order these cuts correctly (the smaller holes must be cut first before the outline is cut).
Step 3: Fan Power Supply
The fan I used is a ~1.5 inch fan (~38 mm) from a broken power supply. It is a 12V fan, but I decided to run it at a lower voltage because I wanted it to be quiet and the lower air flow (at the lower voltage) still delivers adequate cooling. I used an old Nokia 5.7V phone charger to power the fan (although it would also have been possible to use the Pi's internal 5V supply).