Specifications

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3. Hardware Design
While software will be a major component of our project, hardware must also be
considered. Through the design process, there was a focus on ensuring a solid
platform such that any software written could reliably run on the hardware,
without the hardware becoming the proverbial “weak link.” As such, several
considerations such as reliability, price, size, and reduction of complexity are
considered.
3.1 System Design Summary
Given the size and usability requirements, simplifying the device is a priority. At
the same time, however, the device needs to offer a significant level of
functionality while being reliable. Hardware reliability is a great concern since this
device will be the element which determines whether the user is able to operate
their vehicle. A failed unit would mean that the user’s ability to use the device and
their vehicle would be compromised. Given the extent to which most people
depend on their personal vehicles for daily transportation, such a failure could
prove significantly inconvenient to the user.
As such, simplification of the circuit is a priority, as mentioned. In order to
achieve this, a centralized form of control must be used. An analog type of
function is possible. Using several comparator circuits, certain inputs could
trigger LEDs and other alert mechanisms, and operate the vehicle disabling
circuitry. However, such a circuit is not only more complex to design and operate,
but is also more difficult to troubleshoot in case of a component failure. It also
greatly limits scalability, in case the design needs to be revised and/or expanded
in the future.
Given such limitations to analog circuitry, a more centralized, digital solution was
considered. This solution is the commonly used microcontroller. Several options
to a centralized digital controller were considered, as detailed in the System
Logic section, but a microcontroller was the final choice, for the reasons detailed
both there and in this section. In addition, such components are generally
significantly more compact than their analog counterparts, especially when
arranged in a useable circuit.
Another consideration was reducing cost, especially if the device was to be
manufactured in production quantities. While most analog components are low
priced, especially in quantity, the additional cost to tool to handle so many
components, along with the additional engineering necessary even on an
ongoing (support) basis made it an unattractive option. Using a microcontroller
and other digital circuitry would allow for a significant reduction in overall
complexity, reliability, and cost.