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costs. We also ended up paying more for components because we
needed to add connectors so people can add or remove different
sensor modules. We decided to make a modular product with
higher costs anyway, because over the course of the product's
lifetime, it will give us flexibility and it will be less wasteful to
replace or upgrade one part, rather than the whole product.
It's much harder to test modular hardware. For every PCB you
manufacture, you need to make a test jig, as well as another set
of PCBs and software to run tests on your production PCBs. Our
testing process involved four times more work because we chose
to make four separate reconfigurable modules.
Testing a module on its own won't always cover errors that could
happen when the module is in place and interacting with other
components. For example, it won't determine that the module
generates too much electromagnetic interference (which depends
a lot on the spatial layout of components and traces) once the as-
sembly is put together.
The connector was tested separately. Problems that might come
up after assembly, however, include the interaction between the
parts, noise, and other issues related to the components as an ag-
gregate.
We had to make hard decisions about whether to put complexity
in hardware or software. This isn't an issue with modularity per
se, but it is an issue with hackability. It's not enough for a hack-
able product simply to work—it has to explain to its owners how
it works. Thus we had to make both our hardware and our soft-
ware accessible and understandable to our users. For example,
we have an IR emitter-receiver pair that detects deformation in a
silicone film that our users can poke to turn our lamp on and off.
The hardware is dead simple, and that's great! It's easy for
people to see how it works, and it's easy to connect something
else if you want; it's just an analog sensor. But the tradeoff is that
to get our product working in different lighting conditions, we
had to put some fancy calibration in the software that makes it
harder to understand exactly how the silicone “eye” works al-
gorithmically. We made some choices about which parts of our
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