S.N.A.K.E.: A Dynamically Reconfigurable Artificial Sensate Skin ...

Figure 5-1: Stress concentration points in node microcontrollers
because the pin leads can absorb some of the stress and because they are so small that even
sharp bending angles don’t stress the soldered connections enough to break them. This
effect is shown on Figure 5-1. There are several ways around this problem, some of which
will be mentioned in the Conclusions chapter.
5.1.2 Connections
The second mechanical aspect to evaluate was the mechanical terminations used. We men-
tioned before that mechanical terminations were critical to maintain good network stability,
yet there were two problems with the ones chosen in the design: header hole size and con-
nection flap size.
Something that was not foreseen at the design stage of the project is that header holes were
so small that they actually caused connections to easily crack when the node was bent. This
generated numerous connection flaws which sometimes prevented the correct operation of
the I 2 C network in the Skin Patches.
The other thing that was not well though when the design was made is that since headers
were placed on a flap that protrudes from the body of the Skin Nodes, whenever a Skin
Patch experienced some bending, all the bending happened mainly at the flaps and not
at the node body. This was actually a good thing to relieve some of the stress that could
concentrate on the microcontroller pins, however it was detrimental to the performance of
the strain gages. This is shown on Figure 5-2. Because of this, even if the patch is bent,
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