Specifications

level of breath alcohol is over a state-mandated tolerance level, usually between

0.02% to 0.04% blood alcohol concentration, the interlock system prevents the

engine from being started, usually by means of disabling the fuel pump. It is done

this way because with some automobiles, including manual transmission cars, it

is possible to manually catalyze the air-fuel reaction inside the engine and start

the car. By disabling the fuel pump, no fuel can be delivered to the engine, and

as such, prevents it from being started by any other means.

In the case of a successful initial blood alcohol measurement, the fuel pump relay

is enabled, allowing the vehicle to be started. However, since it is possible that

the driver could have coerced another, more sober individual to take the breath

alcohol test in their place, a well designed interlock system will require additional

samples to be taken at random time intervals over the duration of vehicle

operation. If the resample is not provided within a set period of timeout, or the

resample does not meet the state or municipally mandated threshold for

allowable intoxication, the interlock system will log the event for future recovery

by law enforcement, warn the driver of the impending alert, then initiate an alarm

system of sorts by flashing the lights, honking the horn or creating other

disturbing noises, until either the ignition has been terminated, or a qualifying

sample has been provided to the automobile control unit.

A common misconception is that the automobile control unit will disable the

engine during the operation of the vehicle if a resample test has not been

passed. This presents not only an unnecessary danger to the operator of the

motor vehicle, but also opens the device manufacturer to potential liability in the

case of an incident caused by a disabled motor vehicle in motion. Therefore, a

well designed ignition interlock device will be limited to only being able to

interrupt the starter circuit for the vehicle, and prevent the vehicle from being

started.

Most state and municipal requirements for ignition interlock systems set an

interval of time after which the device must be brought into a manufacturer

certified service center for calibration and logged data gathering. This interval

usually falls into a period between 30 to 90 days. As such, it is a requirement of

any such system that an accurate log of events be recorded by the device, and

made available for later retrieval. Just as well, the device must have a defined

means of calibration and testing of the alcohol sensor unit for the purposes of

system service and accurate measurement.

2.8 Enclosure

Although the design and the construction of our enclosure for our Voog

Breathalyzer unit may not be emphasized with important by our senior design

course. It is the group’s wish to create a marketable product. It is our goal to

design and produce a product that will be appealing and easy to use even