Today, we will talk about hardware, but… really hard. Not electronics. This time, it will
be about the case around a prototype.
For years, I was looking for the perfect solution: how to enclose a prototype to fit nicely
in a box. The most common solution is to use a commercially available case.
NB: all the images below can be enlarged by clicking.
Adapting the circuit to the box
At one point, I designed the PCB to fit in a comercially available box. Here is an
example:
Click image to enlarge.
The board inside of its case:
Click image to enlarge.
Advantages:
- A comercially available box is extremely cheap (the above costs about 2~300 yens only, say 2 euros).
- There is a wide variety of box types in various materials and shapes, waterproof or not.
Drawbacks:
- The choice is limited, and you will end up with unused room. Anyway you will never find the
case that fits your needs, and it will end up as a low quality and / or ugly compromise.
- You still have to do nice holes (a window if there is an LCD, holes for leds, buttons, etc…)
and doing it cleanly is extremly difficult, even for a plain round hole.
- This kind of design is the opposite of what should be done. Usually, one designs a circuit,
chooses a battery, etc… and the last requirement is the box.
In any case, by choosing a commercially available box, you end up with a design that looks like
those kits distributed together with electronic monthly magazines, quite far from a professional
design.
Alternative method. Using a CNC machine
As a prototype designer, I always felt unsatisfied to deliver a naked board or a board inside
of a poor designed box. Especially here in Japan, perfection in a prototype is something that
many customers appreciate greatly.
Therefore I made a heavy investment: a CNC machine.
Today I would like to introduce one particular design, how it looks before and after doing
a custom case.
Before
Here is a picture showing how the prototype looked before. The prototype was made by
one of my business partners using our small prototyping board Soroban.
The prototype is a programmable blood pressure system. It was originally fit in 2 boxes.
One for the control unit (containing the Soroban board with a specific extension),
and one for the air pump.
Click image to enlarge.
Designing a case
Designing a specific case takes some time, but as I will show, it is worth the effort.
Here is a first picture of the base. You can notice I use insert nuts for screws, which is
stronger in case of repeatedly opening the box.
Click image to enlarge.
Note that since you can easily make any shape, there is no trouble to nicely fit the
air plug and the battery charger.
Click image to enlarge.
A closeup of the air plug in place.
Click image to enlarge.
A closeup of the battery charger plug.
Click image to enlarge.
Fitting the pump into the case.
Click image to enlarge.
Now fitting the cover, and we get a nice blood pressure measurement device
Click image to enlarge.
Pascal