the box
 

When the motherboard had arrived, I could start looking for a suitable case. What I had in mind at first, was one of those cheap alu toolboxes, available in most DIY-stores.( the ones that look like miniature rockband flightcases) But no size was right, mostly way too big. So I decided to build from scratch, which also promised more fun.

Another advantage was I could build the box from very thin (0.5millimeter) aluminium, so the whole chassis would become a fairly good heat exchanger. Stiffness and strength came from glueing the thin panels to the alu angle iron which forms the corners. Some careful measuring, cutting and glueing were needed to make sure the "lid" fitted exactly and the box stayed firmly closed, but could still be opened easily. The frontpanel came from some copper sheet leftover I had lying around in my workshop. The little penguin, though which the case light shines, was simply drilled through the copper. The case light consists of two yellow led lights I was given by a friend. He also gave me the correct resistor and an explanation how to solder it all together. The led lights are powered from a 12V socket on the mobo, that would normally have been used for powering a case fan. The two led lights were too weak by themselves and "lost" their light into the innards of the case. I solved this by adding a reflector box around the leds, made from the thin and shiny alu sheet. That worked. A warm glow now enlightens the penguin :-)

I did not add the light and the penguin just for eye candy. Remember, this computer is completely silent, so without the light, it would have been difficult to know whether it's running or not.

a switch  ..

Although one of the most humble parts of this computer, it is this little red button visitors seem to find the most charming aspect of the Puppy Box. Originally I had planned to have no switch on the machine at all, choosing On/Off with a wall plug switch. But this board didn't accept such treatment. So I added the simple button. I was lucky again: pushing the button briefly, it acts like a reset button, restarting the system. Holding it down a little longer, it shuts off the machine.

the backplane mistake  

While building I was worrying too much about the strength of the case. So I decided not to cut out the big rectangular hole that is needed to fit the loose backplane cover that comes with the motherboard. Instead I copied the contours of every opening in that cover onto the back of the box and started drilling, grinding and filing. Hours later, every little port on the back of the mobo had its opening... I can now proudly say my box has a "fixed backplane", but I would never ever do this way again! 

Ventilation 

Now this is important: as there are no fans, we have to make sure a constant aiflow can be established inside the box. To achieve this, the puppy box has to be standing upright. It has no bottom panel and, as it stangs somewhat elevated from the desk (on two wooden sticks), fresh cooling air can be easily drawn in from the bottom.. It is drawn in, because it replaces the hot air that is rising out of the box through the vent holes. So the box acts like a small chimney. This is also called "stack effect" Organising the components and their cables inside the box in a clean, streamlined way, leaving a clear path for the air to flow, is also part of this passive cooling strategy. A rather nice side effect of not having fans, is that the box remains remarkebly free of dust inside, despite being rather open at top and bottom. I guess this is due to the absence of the eletrostatic charge that is caused by the forced air stream in a fan-cooled computer.

I decided to paint the box, as I did not like the ambiance of the naked alu. Theoretically it would have been better not to paint, as the three layers of paint (1 primer, 2 finish) definitely lower the heat transfer capacity of the box.

The copper  was sanded and polished till I ran out of patience, then varnished.

Final conclusion about the case: I enjoyed building it. Mostly. But if time and/or money are in short supply, it would be wiser to buy/find an existing box, even if its size isn't perfect. I spent much more on the materials than a readymade (tool-)box would have cost.

welcome

the box

motherboard

passive cooling

power supply

ide compact flash

contact

some links... 

puppy linux

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