Objectives

Our main motivation for creating the Breathalyzer Door Lock stemmed from the fraternity house that the creators live in. In general, intoxicated people are usually more careless and destructive than those not under the influence. In our particular house, the kitchen and library are two rooms that are occasionally left in disorder by an intoxicated and careless brother after a weekend night at the bars. In the case of the kitchen, the initial reaction to this problem by our house officers was to simply lock the room at night. However, this caused an outcry from sober students who simply wanted a midnight snack or a cup of coffee. So, we decided to fabricate a device that would allow sober housemates to use the facility while keeping the drunk ones out. Our breathalyzer door lock system unlocks the door it is installed on for users with little or no alcohol on their breath, and keeps the door locked if alcohol is sensed on the users breath.

BEFORE AFTER

The specific door that we designed this system to be compatible with is in fact the door to our kitchen. While unlocked, the door is normally operated by way of a handle with a thumb lever that acts the same as a normal doorknob. While locked, the thumb lever simply does not retract the tab in the doorjamb, so the door remains closed. So, our system simply needs a small solenoid that can be mounted into the doorframe that is capable of pushing the tab. This does not require a great deal of force, and there are no complications from other mechanisms such as deadbolts. The user simply blows into some piping which inflates a small balloon. The air pressure is sensed by a differential pressure sensor, and a gas sensor determines the amount of alcohol present on the breath of the user.

Features

v Only allow individuals with a low BAC (Blood Alcohol Concentration) through the door

v Operation is simple and involves only blowing into a tube and awaiting results

v Administrative access is available in the form of a keypad

Ø Allows for the addition and deletion of codes for VIP access.

Ø Allows lockdown so that the kitchen may be closed to everyone regardless of sobriety.

High Level Design

This Diagram shows the two different methods for opening the door