Specifications

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5.1.2 Gas Detection Sensor
This hardware and associated hardware will provide the main function of this
project. As such, the gas detection sensor has several main requirements that
will need to be verified. It must detect a low enough concentration of alcohol so
as to be appropriate for an intoxicated human. In addition, in must be sensitive
enough to differentiate between various alcohol levels within the range of legal
BAC (blood alcohol content) ranges, able to be detected by a microprocessor’s
analog to digital convertor. In addition, it must be able to be reset in an
automated and relatively simple manner, in order to allow for additional readings.
The size must also be reasonable, as it must fit in a small space within the size-
restricted portable unit. The price must also be reasonable since the component
will need to be replaced after a certain number of uses due to the degeneration
(due to time and use) of all types of gas sensors.
5.1.3 Enclosure
The enclosure for the portable unit must be as compact as possible. Specifically,
it should be around the size of 4x5” at a maximum. The specifics of this may
change, depending on optimizations or special needs of other components within
the device. It must also be durable enough to withstand repeated use by a
possibly intoxicated individual, and able to possess a reasonable amount of
resistance to basic environmental factors.
It must also possess an opening for sensor input airflow, as well as an exit
aperture for air to flow out. In addition, an opening will have to be made for a
display, as well as one or more LEDs to indicate various statuses and alerts. It
should also be aesthetically non-offensive, such that the user would not leave the
device in his car simply because of the appearance of the unit. If this happened,
it would defeat the portable nature of this project.
5.1.4 Display
The display must be able to display, at a minimum, the BAC content detected. It
must have a backlight to allow for nighttime usage. In addition, it must be easily
legible during both the day and the night. The power requirements should also be
as low as possible, in order to extend battery life. In addition, it should be able to
be easily interfaced to the microcontroller.
Additionally, it should be easily controllable. Whether this means building a driver
circuit to control and drive the display, or having the display have a built-in control
solution, it should not require a large amount of supporting circuitry which would
require a large amount of physical space on the PCB.