Hardware Reference
In-Depth Information
Electronics
For the electronic aspects of a device, determining the core functionality, interface, and
components is an important first step in the design process. Knowing the parts that will
compose a device gives a general sense of the required form and shapes the specifics of the
electronic circuit. For example, in the speakers, the decision to use three AAA batteries as
the power source placed constraints on the size and shape of the speakers and on the design
of amplification circuit. Component selection is also crucial for mass-produced devices, of
course, but many additional constraints apply when designing devices for personal fabrica-
tion. The components have to be available to individuals and possible to assemble without
expensive machines or processes. Often, there are limited possibilities available, especially
for key components. The radio, mouse, and cellphone all have, at their core, an electron-
ic part that performs much of the basic functioning of the device (receiving radio signals,
interpreting the mouse movements, or communicating with the cellular network). For all
three, I've had problems finding or maintaining a supply of these core components: the ra-
dio receiver and mouse chip that I used have since become unavailable and the cellphone
module may become obsolete as cellular networks are upgraded.
This experience points out the essential role that industry can play in DIY: the compon-
ents it makes available shape the devices that individuals can make for themselves. (There
are efforts to produce open source or DIY implementations of core technologies like mi-
crocontrollers and cellular baseband modules but, in general, these don't yet seem to offer
a feasible alternative to commercial components.) For these reasons, the personal fabrica-
tion or DIY process is perhaps better viewed as an individual's ability to assemble the
available technologies into a desired product rather than the ability to make everything
oneself, from scratch.
The limitations on component selection need to be considered when designing the cir-
cuit. For example, with the cellphone, I had to carefully balance the functional require-
ments against the overall size of the circuit board to yield a usable device. This imposed
severe limitations on the functionality: the screen (an LED matrix) shows only eight char-
acters at a time and there's no headphone jack, loudspeaker, removable storage, or many
other common features. Even so, the phone can send and receive calls and text messages,
keep time, and function as an alarm clock, which is enough functionality for me to have
used it as my main phone for the past year. Cramming in more functionality may have
made the device too big or fragile to actually use.
Being selective about the functions I needed (and being able to choose them for my-
self) allowed me to find a compromise that worked for me. In addition, because I faced
similar constraints on component selection as many other hobbyists, I ended up using
components for which I could download open source libraries. I was also often able to
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