Vehicle Interlock System Project

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MOUNT KENYA UNIVERSITY
PROJECT TITLE: VEHICLE INTERLOCK SYSTEM
BY
HAROLD OCHIENG
REG. NO. BTCES/2017/81425
A RESEARCH PROJECT SUBMITTED TO THE DEPARTMENT OF
ELECTRICAL AND ELECTRONIC ENGINEERING IN PARTIAL
FULFILLMENT OF THE AWARD OF A BACHELOR OF
TECHNOLOGY IN COMPUTER AND ELECTRONIC SYSTEM OF
MOUNT KENYA UNIVERSITY
(MAY 12TH
2021)

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DECLARATION
I hereby declare that this project entitled Vehicle Interlock System Using Alcohol Sensor is
based on my original work and except for citations and quotations which have been duly
acknowledged. I, Harold Ochieng Otieno did this work on my own through research. I also
declare that this work has not been previously and concurrently been submitted for any degree
award in Mount Kenya University.
Signature ……………….............................................
Name ………………………………………………...
ID No ………………………………………………...
Date ………………………………………………….
SUPERVISOR
I the undersigned do hereby certify that this is a true report for the project undertaken by the
above-named student under my supervision and that it has been submitted to Mount Kenya
University with my approval.
Signature ………………...........................................
Date ………………………………………………...

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ABSTRACT
Vehicle Interlock System is a prototype developed to prevent drivers under influence of alcohol
from driving vehicles. This prototype has a Grove gas alcohol sensor as the input of the system,
a 16×2 Liquid Crystal Display that shows the state of the breath’s alcohol level, a buzzer that
produces an alarm when a breath sample is to be taken and when there is alcohol present in
their breath, Light Emitting Diode which shows whether it is safe to drive or not and lastly the
Direct Current Motor which acts as the vehicle’s engine. Liquid Crystal Display, Light
Emitting Diode, Direct Current Motor and Buzzer are the system’s outputs.
The objective of this project is to design a prototype circuit that prevents drivers from driving
under the influence of alcohol reducing the number of road fatalities caused by them while
driving.
Currently it is used in the United States of America, Canada and some European countries
while in Kenya what is being used is alcohol blows where they are being administered manua lly
by traffic police officers.
The vehicle interlock system has been of great help in countries where they have already been
implemented. In Kenya at an affordable budget it can be used and after certain period of test
runs, a decline in number of road fatalities will be expected.

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TABLE OF CONTENTS
DECLARATION .................................................................................................................... 2
ABSTRACT............................................................................................................................ 3
TABLE OF FIGURES................................................................................................................ 6
ABBREVIATIONS..................................................................................................................... 7
1.0 CHAPTER ONE................................................................................................................... 9
1.1 INTRODUCTION............................................................................................................. 9
1.2 PROBLEM STATEMENT.............................................................................................. 11
1.3 OBJECTIVES................................................................................................................. 12
1.3.1 Main Objectives ........................................................................................................ 12
1.3.2 Specific Objectives .................................................................................................... 12
1.4 JUSTIFICATION............................................................................................................ 13
1.4.1 BLOCK DIAGRAM.................................................................................................. 14
1.4.2 FLOW CHART......................................................................................................... 15
2.0 CHAPTER TWO ................................................................................................................ 16
2.1 LITERATURE REVIEW................................................................................................ 16
2.1.1 History of the ignition interlock devices..................................................................... 16
2.1.2 Anti-Cheat and Anti-Tampering Designs .................................................................. 17
2.1.3 Effectiveness of the Ignition Interlock Devices........................................................... 18
3.0 CHAPTER THREE: RESEARCH METHODOLOGY....................................................... 20
3.1 SYSTEM DESIGN .......................................................................................................... 20
Arduino Uno...................................................................................................................... 20
MQ3 (Grove Gas) Sensor................................................................................................... 22
16×2 Liquid Crystal Display.............................................................................................. 23
DC Motor.......................................................................................................................... 24
Buzzer ............................................................................................................................... 25
LED Light......................................................................................................................... 25
Mathematical Calculations ................................................................................................ 27

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CHAPTER FOUR: SYSTEM IMPLEMENTATION AND TESTING..................................... 28
4.1 CIRCUIT DIAGRAM......................................................................................................... 28
4.2 SYSTEM DESCRIPTION............................................................................................... 29
4.3 SYSTEM TESTING........................................................................................................ 30
CHAPTER FIVE...................................................................................................................... 33
5.1 LIMITATIONS................................................................................................................... 33
5.2 CONCLUSION ................................................................................................................... 34
5.3 RECOMMENDATION....................................................................................................... 35
REFERENCES......................................................................................................................... 37
APPENDIX............................................................................................................................... 39

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TABLE OF FIGURES
FIGURE 1. BLOCK DIAGRAM ....................................................................................................................................14
FIGURE 2: VEHICLE INTERLOCKSYSTEM FLOW CHART .......................................................................15
FIGURE 3 : ARDUINO S ENSOR (COMPONENTS101, 2018)............................................................................20
FIGURE 4: MQ3 ALCOHOL SENSOR (WIECKOPZ, 2015)...............................................................................22
FIGURE 5:16×2 LCD DISPLAY (COMPONENTS101, 2018)..............................................................................23
FIGURE 6: DC MOTOR (MILLET, 2021)..................................................................................................................24
FIGURE 7: BUZZER (COMPONENTS101, 2017)..................................................................................................25
FIGURE 8: LED (COMPONENTS101, 2018)...........................................................................................................25
FIGURE 9: SYSTEM DES IGN.......................................................................................................................................27
FIGURE 10: CIRCUIT DIAGRAM...............................................................................................................................28
FIGURE 11: BREADBOARD CIRCUIT DESIGN (HAROLD, 2021) ....................................................................29
FIGURE 12: SYSTEM TEST COMPLETE................................................................................................................31
FIGURE 13: BREATH ALCOHOL CONTENT AND ENGINE STATUS ........................................................31

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ABBREVIATIONS
LCD- Liquid Crystal Display
DC- Direct Current
AC- Alternating Current
LED- Light Emitting Diode
USA- United States of America
DUI- Driving Under Influence
MQ3- Grove Gas Sensor
NHTSA- National Highway Traffic Safety Administration
CDC- Centre of Disease Control
NTSA- National Transport Safety Authority
BAC- Blood Alcohol Content
IID- Ignition Interlock Device
PWM- Pulse Width Modulation
USB- Universal Serial Bus
ICSP- In Circuit Serial Programming
SPI- Serial Peripheral Interface
SS- Slave Select
MOSI- Master Out Slave In
MISO- Master in Slave Out
SCK- Serial Clock
AREF- Analog Reference
SDA- Serial Data
SCA- Serial Communication

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TWI- Top Wire Interface
MOS- Metal Oxide Semiconductor
VCC- Voltage Common Collector
GND- Ground
DO- Digital Output
AO- Analog Output
PCO- Programmed Control Output
VEE- Voltage Emitter
RX- Receiver
TX- Transmitter

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1.0 CHAPTER ONE
1.1 INTRODUCTION
Driving under influence (DUI) of alcohol is seriously a major problem in the past and currently
still a major problem. According to National Highway Traffic Safety Administration
(NHTSA), 10511 people die in alcohol-related accidents in 2018. However, the Centres of
Disease Control (CDC) has identified that 30 people die every day in the United States in
alcohol related car accidents. For the mathematicians out there, that’s 50 deaths every minute.
Drunk driving is a serious epidemic and must be treated as such (Covington, 2021).
By 9th October 2020, 2689 people had been killed in road accidents between January and
September compared to the loss of 2655 lives in the same period in 2019. According to the
statistics released by the National Police Service and the National Transport Safety Authority
(NTSA) in Nairobi, motorcyclist and pillion passenger deaths increased by 44.94% and 19.44%
respectively. The road safety enforcers have blamed increased road fatalities bon speeding and
drunk driving (XinhuaNet, 2020).
Road accidents are on the rise with a minimum of five people dying daily on Kenyan roads.
According to the Traffic Act, section 44(1), anyone who when attempting to drive or driving,
when in charge of a car on a road or a public place, is found to be under the influence drugs or
drinks to the extent that they do not have proper control of the car, shall be charged with an
offense and liable to pay a fine that is not less than 100,000 shillings or face imprisonment for
two years or even subject to both penalties. Tests in Kenya used to determine whether a driver
is drunk are alcohol blows and urine tests. While many people have taken drunk driving
accidents for granted, they have accounted for a large percentage of fatalities and serious
accidents on the Kenyan roads (Mwaniki, 2021).
Therefore, the best solution to this problem is the vehicle interlock system device. A vehicle
interlock system device is essentially a breathalyser installed into a vehicle’s ignition system
which will act as a DUI protection device. A driver must provide a breath sample into the grove
gas alcohol sensor (MQ3) of the vehicle interlock system. The system will then measure the
blood alcohol content (BAC)and compare it to the pre-set limit which for this instance is
1.5mg/L (1.5 milligram of alcohol in 1 litre of blood). If the BAC records registers over the

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pre-set limit, then the vehicle’s ignition system will not be started and when the BAC records
below the pre-set limit then the vehicle ignition system will start.
The first performance based interlocks were developed by Borg-Warner Corp (now
BorgWarner, Inc.), in 1969. In 1981, Jeffrey Feit, a student in New Jersey, placed in a state-
wide innovation contest with a primitive schematic of a breathalyser based interlock device. In
1983, Hans Doran, a student in Limerick, presented a working prototype at the Young Scientist
competition in Dublin. Alcohol sensing devices became the standard through the 1980s. they
employed semiconductor (non-specific) alcohol sensors. Semiconductor type (Taguchi)
interlocks were sturdy and got the field moving, but did not hold calibration very well, were
sensitive to altitude variation, and reacted positively to non-alcohol sources.
Commercialization and more widespread adoption of the device was delayed pending
improvement of systems for preventing circumvention. A 2019 EU regulation, applicable to
new cars from July 2022 makes compulsory the alcohol interlock installation facilitation for
all motor vehicle categories. (Wikipedia, 2015)
The vehicle interlock system ensures no driver will operate their vehicles under influence of
alcohol. Once the vehicle is started, the system will start and request the breath sample of the
driver for detecting alcohol content in it. If it is present, the ignition system of the vehicle will
not be able to start. If the driver’s breath sample is clean the vehicle ignition will start.
The vehicle interlock system is an advancement of the alcohol blows in that the whole system
is inbuilt and no third persons is required for operation. The MQ3 alcohol sensor is the input,
Arduino Uno microcontroller for processing, a 16×2 LCD display to show the level of alcohol
content in driver’s breath and a DC motor switch that acts as the vehicle engine.
Successful implementation of the system will ensure reduced fatalities in the current and near
future times. Future manufacture and assembling of vehicles with the vehicle interlock system
in it will make the drivers and passengers safe while driving.

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1.2 PROBLEM STATEMENT
Driving under influence has led to high rates of life loss through road accidents. The high death
rate leads to high level of trauma globally among people due to fear of occurrence of accident
in traffic while they are travelling. In these situations, the significant absence of such system
will jeopardize the safety of the general public as driving under the influence of alcohol is
increasing annually. This brings an increase to the number of material losses, injuries and
fatalities from accidents caused by DUI of alcohol. As such, initiatives must be taken to conduct
a research that can produce a reliable and cost-effective system that will resolve the
aforementioned problems, providing the same key features as the system in United States,
Canada and Europe but cheaper to produce, or in other words a low-cost design with all the
same features and functionalities.

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1.3 OBJECTIVES
1.3.1 Main Objectives
The main objective of this project is to design a prototype circuit that prevents drivers from
driving under the influence of alcohol, reducing the number of road fatalities caused by them
while driving.
1.3.2 Specific Objectives
1. To design a vehicle interlock system using alcohol sensor and Arduino.
2. To simulate the vehicle interlock system using an alcohol sensor so as it’s fully
operational.
3. To analyse the provided breath sample alcohol content and compare it to the pre-set
limit.
4. To develop an alarm system that activates when the blood alcohol content is above the
pre-set limit.

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1.4 JUSTIFICATION
Vehicle interlock system is designed in a way that for every vehicle’s engine ignition, the
driver has to provide his/her breathe sample to check for alcohol content level for
confirmation that one is not a driver under influence. The system is timely such that driving
under influence accidents have been so high lately that such a solution will be of great impact
and help.
Such a system has advantages that include; maintenance of legal driving status, it is highly
affordable, prediction of future DUI offences, it benefits both the DUI offenders and their
family, it saves a lot of lives and finally helps reduce recidivism rates
This system is composed of MQ3 Alcohol sensor, a 9 Volt battery power supply, Arduino
Uno ATmega328 microcontroller, LEDs, Buzzer, 16×2 LCD display and DC Motor.
All these are combined to form a circuit that is used as a prototype for the vehicle interlock
system. Its solution is to reduce the number of DUI accidents caused in traffic. It prevents
DUI offenders from access and driving of their vehicles. Vehicle interlock system may help
in reduce the high level of trauma among people since it will provide a sense of trust and
relief that they will be safe throughout their journey.

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1.4.1 BLOCK DIAGRAM
×××
1. Power Supply- it provides power used to run the system’s components.
2. MQ3 Sensor- it acts as the input of the system by sensing alcohol content in one’s breath
3. Arduino Uno R3- a microcontroller that reads analogue and digital input signals from
different sensors and produces an output as instructed by the code uploaded in it.
4. 16×2 LCD Display- it displays text characters programmed for the system.
5. DC Motor- it acts as the system’s vehicle engine. It shows whether the car is running or
not.
6. LED- shows the driver that the breath sample is from alcohol or not.
7. Buzzer- acts as an alarm to alert the driver to provide their breath sample and when
alcohol content is present in their breath.
ARDUINO
UNO
MQ3
SENSOR
16*2 LCD DISPLAY
RELAY DC MOTOR
LEDs
BUZZER
POWER SUPPLY
Figure 1. Block Diagram

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1.4.2 FLOW CHART
The order of events of the Vehicle Interlock System is shown in the flow chart.
PROVIDE
ANOTHER BREATH
SAMPLE
Figure 2: Vehicle Interlock System Flow Chart
START
PROVIDE BREATH
SAMPLE
RESULTS
VEHICLE IGNITION
STARTS
10 SECONDS TIME
DELAY
AFTER 1 HOUR
RESULT
S
BUZZER ALARM
ON
RED LED LIGHTS
END
PASS FAIL
PASS FAIL
ENGINE
STOP
10 MINUTES
DELAY

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2.0 CHAPTER TWO
2.1 LITERATURE REVIEW
Examination of risks posed by Driving under the Influence (DUI) and review studies of the
level of blood alcohol content on the risk of crashing while driving. From this review, we can
reinforce the relevancy and significance of this project. From this point, we look upon the brief
history of alcohol blows or breathalyser and breathalyser ignition lock devices (IID). We also
review a few researches on the effectiveness of the IIDS. The aspects to be reviewed are
histories of the ignition interlock devices, anti-cheat and anti-tampering designs, effectiveness
of the ignition interlock devices.
2.1.1 History of the ignition interlock devices.
The study of alcohol as an academic experiment can be traced back to the 1700s when J.J.
Plenc proposed the chemical identification of poisons. However, the first ever practical
roadside breath-testing device, called the drunk-o-meter was pioneered by Professor Rolla H.
Harger in 1938. His version collected the driver’s breath sample into a balloon in the device.
The sample was pumped in an acidified potassium permanganate solution, and if alcohol
existed in the sample of breath, the solution changed color, and the more the color changed,
the more alcohol was in the breath. However, this device invented by Professor Rolla H. Harger
was impractical as it requires re-calibration every time it is moved around.
It was not until 1954, when Professor F. Borkenstein invented the breathalyzer; a substantial
improvement to its predecessor by Professor Rolla H. Harger as this version is highly portable
thus making it more practical. However, the device was merely a testing device and had no
prevention properties towards DUI. All this would change in the 1970s, when a drunk driver
killed both Craig D. La Londe‟s father and 3-year-old. Craig D. La Londe, a self-made
businessman pioneered the breathalyzer ignition interlock that wouldn't let a motorized vehicle
start until the operator took a mandatory breath alcohol test, if failed the vehicle won't start.
Professor Rolla H. Harger, Professor F. Borkenstein and Craig D. La Londe designs were not
ideal form mass production and implementation as they were flawed.
Craig D. La Londe’s design was too simple and had no fail-safes to the devices which meant
the vehicle driver simply has to ask another individual to provide a clean breath sample to the
device to start the car’s ignition. The system could not be cheated.

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Professor Rolla H. Harger design was not feasible to be implemented and was more of an
academic research instead of targeting implementation of the device. His design sets
precedence for modern breathalyser device as it was not attached to the vehicle’s ignition
system as a control device. From this it is shown that Professor Harger disregards the issue of
feasibility and treats it more as an academic experiment.
These researchers gave a clearer objective regarding scope of study of this project. Now there
are some considerations to be done for it to properly conduct the design and development phase
of the project. They include: It must be decided on the mechanism of the whole process of
testing breath sample and enabling or disabling the ignition system and ways of which an
individual can cheat the system. How effective are the ignition interlock devices in curbing the
DUI problem?
2.1.2 Anti-Cheat and Anti-Tampering Designs
There are potential ways of cheating the design as it way to simple and straightforward in
addition to not having cheat prevention features. Craig D. La Londe’s design is just an interlock
ignition device which acts to request for a one-time breath sample before the vehicle’s ignition
is started. This provides an ample opportunity for the user to cheat for example requesting a
clean breath sample from another individual before starting up the vehicle thereby rendering
the device useless.
One way to curb this device exploitation is using a technique where it requires the users to take
rolling re-tests after the engine has been running for a certain period of time. If the user were
not to take the test within a given period of time, or fails the rolling re-tests, the car’s alarm
will sound and the emergency signal lights will be activated. This will continue on until the
driver found a safe spot to pull his car over and shut off the engine. This will therefore mitigate
the problem of requesting for a clean breath sample from another individual prior to starting
up your car. The purpose behind the alarm blaring and the emergency signal lights is to alert
other nearby drivers to stay away from the potentially drunk driver and the authorities to pull
the vehicle over for inspection. However, the design of their breathalyzer ignition interlock is
not ideal or optimum in a way that it distracts the driver’s attention from the road in order for
them to perform the rolling re-tests. This will be one aspect looked to improve upon in the
future works. Furthermore, there will also be a problem of a passenger providing the clean
breath sample for the driver which we will look to resolve in our research for the ideal low-
cost prototype in future works.

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A feature acting as anti-tampering deterrence is the log reading feature which records all the
recent activities in a log for reference by the authorities in case tampering or failed rolling re-
tests by the charged DUI offenders. This feature acts as a hindrance for any potential cheating
of the system. Here, I look towards integrating these anti-cheat and anti-tampering features in
the device and also looking towards resolving these flaws.
2.1.3 Effectiveness of the Ignition Interlock Devices.
According to Coben JH and Larkin GL (1999) in their paper “Effectiveness of ignition
interlock devices (IID) in reducing drunken driving recidivism”, five of the six studies show
that IIDs were effective in reducing DWI and DUI recidivism while the interlock was installed
in the vehicle. In these five studies, demonstrating a significant effect, participants in the IID
program were 15 percent to 69 percent less likely than controls to be re-arrested for DUI. The
only reported randomized, controlled trial demonstrated a 65 percent reduction in re-arrests for
DWI in the interlock group, compared with the control group. (Coben & Larkin, 1999)
They concluded that IID programs appear to be effective in reducing DUI rearrests during the
time period when the interlock is installed in the car and that future studies should attempt to
control the exposure and determine if certain sub groups are most benefited by interlock
programs.
According to Andrew Fulkerson (2003) in his paper, “The Ignition Interlock System - An
Evidentiary Tool Becomes a Sentencing Element”, the device has been proven in empirical
studies to reduce recidivism for repeat DUI offenders, young drivers, and persons with very
high BAC levels. Andrew Fulkerson (2003) added that those reductions are substantial and
statistically significant and the interlock is effective in preventing future violations even when
the particular offenders have difficulty in controlling their own behavior. Andrew Fulkerson
(2003) further concludes that the interlock does not rely upon motivation or cooperation by the
offender and operates to prevent the offending behavior by intervening between the offender
and the vehicle. According to him in his paper, it only stops the person from drinking and
driving in the vehicle equipped with an interlock and thus, controls the “intersecting risk
behaviors” of drinking and driving. (Fulkerson, 2003)
Therefore, according to the studies made by Andrew Fulkerson (2003) and Coben and Larkin
GL (1999), IID is indeed an effective tool in combating the DUI cases thus making this project
much more relevant as it is proven to be an effective tool and mechanism.

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Modern ignition interlock devices use an alcohol-specific fuel cell for a sensor. A fuel cell
sensor is an electromechanical device in which alcohol undergoes a chemical oxidation
reaction at a catalytic electrode surface (platinum) to generate an electric current. This current
is then measured and converted to an alcohol equivalent reading.
Many countries are requiring the ignition interlock as a condition for drivers convicted of
driving under influence of alcohol especially repeat offenders. Most US states now permit
judges to order the installation of an ignition interlock device as a condition of probation; for
repeat offenders, and for first offenders in some states in some states, installation may be
mandated by law (Wikipedia, 2015).
Ignition interlock devices implementation has managed interlock issues and monitor DUI
offenders who are required to install them. Despite the laws and program, only about one-fifth
of those arrested for DUI and DWI have IID installed in their vehicles.
Ignition Interlock device has been adopted in following countries. In Australia it is used in the
states of Victoria, South Australia, Western Australia, Tasmania and New South Wales.
Queensland, the Northern Territory and the ACT are also looking into their use.
Other countries that are undergoing ignition interlock device installations include Austria,
Belgium, Canada, Finland, France, Netherlands, New Zealand, Sweden and United States of
America.

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3.0 CHAPTER THREE: RESEARCH METHODOLOGY
3.1 SYSTEM DESIGN
The components that make up the system design are as follows:
Component Function
Arduino Uno Microcontroller board
MQ3 Sensor Alcohol sensor
Buzzer Alarm
16×2 LCD Text Display
LED Signal light
DC Motor Engine
The specifications of the system’s components are given below:
Arduino Uno
Arduino Uno is a microcontroller board based on 8-bit ATmega328P microcontroller. Along
with ATmega328P, it consists other components such as crystal oscillator, serial
communication, voltage regulator, etc. to support the microcontroller. Arduino Uno has 14
digital input/output pins (out of which 6 can be used as PWM outputs), 6 analogue input pins,
a USB connection, A Power barrel jack, an ICSP header and a reset button.
Figure 3 : Arduino Sensor (Components101, 2018)
The 14 digital input/output pins can be used as input or output pins by using pinMode (),
digitalRead () and digitalWrite () functions in Arduino programming. Each pin operates at 5V
and can provide or receive a maximum of 40mA current, and has an internal pull-up resistor of
20-50 KOhms which are disconnected by default. Out of these 14 pins, some pins have specific
functions as listed below:

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1. Serial Pins 0 (Rx) and 1 (Tx): Rx and Tx pins are used to receive and transmit TTL
serial data. They are connected with the corresponding ATmega328P USB to TTL
serial chip.
2. External Interrupt Pins 2 and 3: These pins can be configured to trigger an interrupt
on a low value, a rising or falling edge, or a change in value.
3. PWM Pins 3, 5, 6, 9 and 11: These pins provide an 8-bit PWM output by using
analogWrite () function.
4. SPI Pins 10 (SS), 11 (MOSI), 12 (MISO) and 13 (SCK): These pins are used for SPI
communication.
5. In-built LED Pin 13: This pin is connected with a built-in LED, when pin 13 is HIGH
– LED is on and when pin 13 is LOW, it’s off.
Along with 14 Digital pins, there are 6 analog input pins, each of which provides 10 bits of
resolution, i.e. 1024 different values. They measure from 0 to 5 volts but this limit can be
increased by using AREF pin with analog Reference () function.
Analog pin 4 (SDA) and pin 5 (SCA) also used for TWI communication using Wire library.
Arduino Uno has a couple of other pins as explained below:
1. AREF: Used to provide reference voltage for analog inputs with analogReference ()
function.
2. Reset Pin: Making this pin LOW, resets the microcontroller.
The main reason as to why Arduino Uno was selected as this project's microcontroller board is
the flexibility of the board to two different external power supplies namely USB to computer
or from AC/DC source or battery. This is a feature that is extremely useful for demonstration
purposes of the project.
Programming on the Arduino Uno board will require using the Arduino IDE software. To
upload the source code onto the Arduino Uno board requires a Universal Serial Bus (USB)
connection to the computer containing the Arduino IDE software and the source code intended
to be uploaded to it.

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MQ3 (Grove Gas) Sensor
MQ3 is one of the most commonly used sensors in the MQ sensor series. It is a MOS type of
sensor. Metal oxide sensors are also known as Chemiresistors, because sensing is based on the
change of resistance of the sensing material when exposed to alcohol. So by placing it in a
simple voltage divider network, alcohol concentrations can be detected.
Figure 4: MQ3 Alcohol Sensor (Wieckopz, 2015)
For MQ-3 Sensor Module
Pin description:
1. VCC- This pin powers the module, typically the operating voltage is +5V
2. GND- Used to connect the module to system ground
3. DO- You can also use this sensor to get digital output from this pin, by setting a
threshold value using the potentiometer
4. AO- This pin outputs 0-5V analog voltage based on the intensity of the gas
The resistance of the MQ-3varies with different types of gases at different concentration levels.
Therefore, when using this component, calibration is a necessity to determine its proper alarm
point. Due to the fact that the sensor is a semiconductor device, it is highly affected by
temperature and humidity.
With that being mentioned since the extensive testing of those two variables are beyond the
scope of this project, it will be assumed that the temperature and humidity is nearly constant
during any calibration processes. The sensor is also highly time dependent. While the resistance
of the sensor reaches a fairly consistent steady-state value when exposed to ethanol gas
concentrations, it still takes about a minute, on average, for that value to be attained.
MQ3 sensor calibration is that it needs a driver circuit for it to operate form the 5V input
voltage. It operates as both a potentiometer that forms an adjustable voltage divider and a
voltage divider that is used to measure voltage. High alcohol content in the air provides high
output voltage while low alcohol content in the air provides low output voltage.

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The proposed semiconductor breath alcohol detector is cheaper in cost and is as effective as
other types of breath alcohol detector. Furthermore, the MQ-3 alcohol sensor can be easily
interfaced to a microcontroller as the output yield is in voltages. Power dissipation does not
influence the MQ-3 alcohol sensor as the semiconductor sensor model has very low power
dissipation although it works with presence of heat because it only needs low voltage value in
the range of 3.3 V to 5 V as its input. The sensitivity of the sensor is also relatively high
compared to the other models researched. Although the MQ-3 alcohol sensor is capable of
detecting other substances and misinterprets it as alcohol, the sensitivity towards alcohol is
much higher and this makes it a very reliable alcohol detecting device.
16×2 Liquid Crystal Display
LCD modules are very commonly used in most embedded projects, the reason being its cheap
price, availability and programmer friendly. Most of us would have come across these displays
in our day to day life, either at PCO’s or calculators.
Figure 5:16×2 LCD DISPLAY (Components101, 2018)
The appearance and the pinouts have already been visualized above now let us get a bit
technical. 16×2 LCD is named so because; it has 16 Columns and 2 Rows. There are a lot of
combinations available like, 8×1, 8×2, 10×2, 16×1, etc. but the most used one is the 16×2 LCD.
So, it will have (16×2=32) 32 characters in total and each character will be made of 5×8 Pixel
Dots.
The 16×2 LCD pinout is shown below:
1. Pin1 (Ground/Source Pin): This is a GND pin of display, used to connect the GND
terminal of the microcontroller unit or power source.
2. Pin2 (VCC/Source Pin): This is the voltage supply pin of the display, used to connect
the supply pin of the power source.
3. Pin3 (V0/VEE/Control Pin): This pin regulates the difference of the display, used to
connect a changeable POT that can supply 0 to 5V.

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4. Pin4 (RegisterSelect/Control Pin): This pin toggles among command or data register,
used to connect a microcontroller unit pin and obtains either 0 or 1(0 = data mode, and
1 = command mode).
5. Pin5 (Read/Write/Control Pin): This pin toggles the display among the read or writes
operation, and it is connected to a microcontroller unit pin to get either 0 or 1 (0 = Write
Operation, and 1 = Read Operation).
6. Pin 6 (Enable/Control Pin): This pin should be held high to execute Read/Write
process, and it is connected to the microcontroller unit & constantly held high.
7. Pins 7-14 (Data Pins): These pins are used to send data to the display. These pins are
connected in two-wire modes like 4-wire mode and 8-wire mode. In 4-wire mode, only
four pins are connected to the microcontroller unit like 0 to 3, whereas in 8-wire mode,
8-pins are connected to microcontroller unit like 0 to 7.
8. Pin15 (+ve pin of the LED): This pin is connected to +5V
9. Pin 16 (-ve pin of the LED): This pin is connected to GND.
DC Motor
An electric motor is an electrical machine which converts electrical energy into mechanical
energy. DC motors operate on Faraday’s principle of electromagnetism which states that a
current-carrying conductor experiences a force when placed in a magnetic field. According to
Fleming’s “Left-hand rule for electric motors,” the motion of this conductor is always in a
direction perpendicular to the current and the magnetic field.
Mathematically, we can express this force as F = B×I×L (where F is force, B is the magnetic
field, I stand for current, and L is the length of the conductor).
Figure 6: DC Motor (Millet, 2021)

25
Buzzer
This is a small yet efficient component to add sound features to our project/systems. It is very
small and compact 2-pin structure hence can be easily used on breadboard. There are two
types are buzzers that are commonly available. The one shown here is a simple buzzer which
when powered will make a continuous beeeeeeppp.... sound, the other type is called a
readymade buzzer which will look bulkier than this and will produce a beep beep beep sound
due to the internal oscillating circuit present inside it.
Figure 7: Buzzer (Components101, 2017)
This buzzer can be used by simply powering it using a DC power supply ranging from 4V to
9V. A simple 9V battery can also be used, but it is recommended to use a regulated +5V or
+6V DC supply. The buzzer is normally associated with a switching circuit to turn ON or
turn OFF the buzzer at required time and require interval.
LED Light
An LED is a two-lead semiconductor light source, which emits lights when activated. When
an appropriate voltage is applied to the LED terminal, then the electrons are able to
recombine with the electron holes within the device and release energy in the form of
photons. This effect is known as electroluminescence. The color of the LED is determined by
the energy band gap of the semiconductor.
Figure 8: LED (Components101, 2018)

26
For this system:
The Arduino Uno board is used for uploading the prototype code used for running the system
The 16×2 LCD is used to display the system's text when the prototype is running. It also
displays the amount of blood alcohol content in someone's breath.
MQ3 sensor is an alcohol sensor that detects the alcohol content in someone's breath and
sends a signal to the Arduino Uno board.
Buzzer is used to produce an alarm when one is supposed to provide a breath sample. It also
alerts one when the blood alcohol content in one's breath is higher than the intended limit.
LED is used to show when one's breath sample is free from alcohol content or not.
DC motor is used to symbolize the vehicle's engine and when alcohol content is present in
their system or not, it doesn't run or runs consecutively.

27
Below is the system design after all the components are soldered together:
Figure 9: System Design
Mathematical Calculations
AdcValue= 0
V= (AdcValue/10) × (5.0/1024.0)
BAC(mg/L) = 0.67×V
For AdcValue of 5V, which equals 5000mV;
V = (5000/10) × (5.0/1024.0) = 2.4414
BAC= 2.4414 × 0.67= 1.63mg/L which is above the preset limit. Vehicle ignition fails.
For AdcValue of 2.5V, which equals 2500mV;
V = (2500/10) × (5.0/1024.0) = 1.2207
BAC= 1.2207 × 0.67= 0.81mg/L which is below the preset limit. Vehicle ignition starts.

28
CHAPTER FOUR: SYSTEM IMPLEMENTATION AND TESTING
4.1 CIRCUIT DIAGRAM
The vehicle interlock system has to have a circuit diagram that makes it work as it is
intended. All the components are shown in the circuit below:
Figure 10: Circuit Diagram

29
Figure 11: Breadboard Circuit Design (Harold, 2021)
The system has undergone various changes hence the circuit diagram can be modified in
many different ways.
4.2 SYSTEM DESCRIPTION
For this project, there is a precedent system; therefore, I employed the “feasibility studies”
technique which basically is a study of existing systems and the possibilities of replacing them,
which can then provide an outline of requirements details. This gives the author the initial idea
on the core functionalities of the system.
This involves examining and analyzing the problem identified which, are the accidents caused
by DUI and also examining the features and functionalities existing similar system in the USA
to design and develop a breathalyzer ignition interlock system with improved features and
functionalities to those of its western counterpart to be implemented in Malaysia. From the
initial stage of the system requirement gathering where “feasibility studies” technique is
employed, we have a guideline of the core functionalities that the system will have. The initial
list of core functionalities identified as follows:
1. Measure and test for the blood alcohol content in someone's breath
2. Set a preset in the system Arduino code for blood alcohol content limit.

30
3. Enable vehicle ignition system if measured or tested BAC is lower than the pre-
programmed BAC. (vehicle ignition system will be in disabled mode – default settings
and will only be enabled if test is passed, therefore if test fails, nothing will happen)
The second stage of system requirement gathering will be the enhancement and refining of
these initial features, be it improving existing or adding new functionalities to the breathalyzer
ignition interlock system. This is where the system development methodology of prototyping
plays an important role. After iterations upon iterations of the system are complete, tests are
being run in all different kind of scenarios exploring every weakness of the system and possible
loopholes which can be exploited.
4.3 SYSTEM TESTING
A breadboard is used in testing the system, it is used to help one connect components to
complete basic circuits. It is a thin plastic board used to hold electronic components for
developing prototypes of electronic circuits as they can be reused.
A multimeter is used to test the current, voltage and resistance of the circuit components.
Ethanol is used here because all alcohol which is consumed is fundamentally ethanol. The
ability of ethanol to volatilize in the lungs makes it a good candidate to be detected with
breathing devices such as this Vehicle Interlock System. This test approximates a person’s
BAC because the concentration of alcohol vapor in the lungs is directly relate3d to its
concentration in blood. (Wordpress, 2020)
The blood-to-breath ratio can vary between 1500:1 and 3000:1. The ratio varies among
individuals according to age, gender, genetic makeup and state of intoxication, within a given
individual at different times and among measuring devices. The 2100:1 ratio is used as a
standard conversion factor in determining BAC from the Vehicle Interlock System.
(Wordpress, 2020)
A simulation test was used to run the Vehicle interlock system using ethanol. The fundamental
of the circuitry is divided into 3 sub-circuits which are the voltage regulator circuit, the Arduino
Uno microcontroller board which houses the ATmega328 microcontroller and the MQ-3
alcohol sensor. The MQ-3 alcohol sensor is connected to the Arduino Uno microcontroller
board which controls the whole system.
When the system is switched on, the sensor takes time to stabilize its readings. The system
starts by visualizing the texts of system startup. A beep voice sounds to notify the user to

31
provide the breath sample. The breath sample is analyzed and if it above the preset limit, the
system produces an alert and the vehicle engine (dc motor) stops. When the alcohol content in
the breath sample is low, the vehicle engine (dc motor) starts running.
Figure 12: System Test Complete
The operation of the prototype is shown in the table below:
Breathe Alcohol Content(mg/L) STATUS
0.0 PASS, ENGINE START
1.5 FAIL, ENIGINE STOP
1.6 FAIL, ENGINE STOP
Figure 13: Breath Alcohol Content and Engine Status
The Vehicle Interlock System functions under a pre-set value for it to work as intended. The
blood alcohol content is calculated in milligrams of alcohol in a liter of blood. As shown in the
table, blood alcohol content limit for the vehicle interlock system is 1.5mg/L.
BAC values of 0mg/L to 1.4mg/L is considered safe by the system prototype thus allowing the
start of the vehicle ignition. The LCD displays pass and engine start as the motor runs.

32
BAC values of 1.5mg/L and above is considered not safe by the vehicle interlock system
prototype thus ensuring that the vehicle ignition does not start. The LCD displays fail and
engine lock which means the DC Motor does not run.

33
CHAPTER FIVE
5.1 LIMITATIONS
There are certain limitations that I faced during the design of this system prototype. These are
shown below:
 The system inability to prevent one from cheating by providing a clean breath sample
from another person for example a passenger.
 Frequent logs recording. The system will be effective when the driver can provide
breath samples over a span of time for example after every hour. The limitation is that
it will distract the driver during the process and might cause an accident.
 One might tamper with the system and this might cause errors.
 Driver might provide another breath sample and when it records high, the car might
come to a sudden stop. In a case where he is on a highway, sudden stop of the car
might cause fatalities.
 Lack of adequate finance to expand the scope of the project.

34
5.2 CONCLUSION
Before the inception of this project, a clear goals and objectives was defined in that a vehicle
interlock system device with comparable features and functionalities from its western
counterpart will be designed and developed. Additionally, it will also address a few design
issues in the current breathalyzer ignition interlock device in the market. Furthermore, the issue
of cost prevents western counterpart of the breathalyzer ignition system to be implemented,
exposed and fully-utilized in Kenya thus making a vehicle interlock system device with
comparable features and functionalities an attractive and relevant option.

35
5.3 RECOMMENDATION
In regards to the potential expansion and future works of this project, there is a lot of area which
we could explore especially in regards towards preventing cheating of the system and
tampering of the device.
In regards to anti-cheating, one prevalent way to cheat the device is to request for a clean breath
sample from another individual before starting up the car. Proposed future expansion and works
to alleviate this issue involve, security facial recognition software to authenticate that it is the
registered driver of the vehicle taking the test. Another possible solution will be a fingerprint
scan while taking the breathalyzer test, to prevent a different individual from the registered
driver from operating the vehicle. Another more advance proposal will be a simple DNA test,
from the breath sample obtain to authenticate that it is the right person whom should be taking
the breathalyzer test. For problems of anti-tampering, one proposed solution is to make all
breathalyzer ignition interlock device installed in vehicle’s to be connected to a central
headquarter, wirelessly, thus there will be a live monitoring of all devices and any attempts of
tampering will be notified to the authorities immediately.
There will be some design flaws in the current vehicle interlock system which we will also
look to resolve as part of our objective to design and develop the ideal low-cost vehicle ignition
lock device. The identified flaws in the current design which we look to resolve are:
 A flow control sensor that acts as anti-cheating device.
 A design of a vehicle interlock system that won't distract the driver when running retests
when they are driving.
 Preventing a passenger from providing a clean breath sample.
 Removal of power source will result in log recording function disabled, thus
circumventing the supposed “anti-tampering” feature.
 Design of vehicle interlock system that when it detects a high alcohol content breath, it
slows down the vehicle to a preset speed limit instead of bringing the vehicle to a sudden
stop.
 Design of a vehicle interlock system that it MQ3 sensor detects only alcohol content in
someone's breath and no other products like perfumes that might be misread as alcohol.
 Facial recognition software and fast DNA test that authenticates that the one providing
the breath sample is the one driving too.

36
 A pressure sensor under the driver seat that sends a signal to the vehicle ignition lock
device to start once the driver sits resets whenever he/she leaves their seat and engage
retest once they return.

37
REFERENCES
1. C. & L., 1999. NationalLibrary of Medicine- Effectivenessof ignition interlock devicesin
reducing drunkdriving recidivism. [Online]
Available at:https://pubmed.ncbi.nlm.nih.gov/9921390/
[Accessed8May 2021].
2. Components101,2017. Active PassiveBuzzer. [Online]
Available at:https://www.components101.com/misc/buzzer-pinout-working-datasheet
3. Components101,2018. 5mm Round LED. [Online]
Available at:https://ww.components101.com/diodes/5mm-round-led
4. Components101,2018. Arduino Uno. [Online]
Available at:https://www.components101.com/microcontrollers/arduino-uno
5. Components101,2018. LCD. [Online]
Available at:https://www.elprocus.com/lcd-16*2-pin-configuration-and-its-working/
6. Covington,T.,2021. DrunkDriving Statistics2021. [Online]
Available at:https://www.thezebra.com/resources/research/drunk-driving-statistics/
[Accessed17 May 2021].
7. Fulkerson,A.,2003. The IgnitionInterlockSystem:AnElementaryTool BecomesA
SentencingElement.p.27.
8. Harold,2021. circuito.io. [Online]
Available at:https://www.circuito.io/
9. Millet,2021. BrushlessvsBrushed DC Motor. [Online]
Available at:https://www.monolithicpower.com/en/brushless-vs-bushed-dc-motors
10. Mwaniki,J.,2021. Arrested for DrunkDriving in Kenya:WhatDUILaw says,Penalties.
[Online]
Available at:https://www.kenyayote.com/arrested-for-drunk-driving-in-kenya-what-dui-

38
law-says-penalties/
[Accessed17 May 2021].
11. Wieckopz,2015. SimpleBAC Detector Device. [Online]
Available at:https://www.instructables.com/Simple-BAC-Detector-Device
12. Wikipedia,2015. Wikipedia Ignition InterlockDevice. [Online]
Available at:https://en.m.wikipedia.org/wiki/Ignition_interlock_device
[Accessed10 December2020].
13. Wordpress,D.U., 2020. The AlcoholPharmacology Education Partnership. [Online]
Available at:https://sites.duke.edu/apep/module-4-alcohol-and-the-breathlyser-
test/content-ethanol-in-the-blood-equilibrates-with-ethanol-in-the-alveolar-air/
14. Wordpress,D.U., 2020. The BreathalyzerAssumesA Specific Blood-to-Breath-Ratio To
CalculateThe BAC. [Online]
Available at:https://sites.duke.edu/apep/.module-4-alcohol-and-the-breathlyzer-assumes-
a-specific-blood-to-breath-ratio-to-calculate-the-bac/
15. XinhuaNet,2020. Road AccidentsClaim2689 lives in Kenya in 9 months.. [Online]
Available at:http://www.xinhuanet.com/english/2020-10/09/c-139429002.htm

39
APPENDIX
#include <LiquidCrystal.h>
#include <DCMotor.h>
#include <LED.h>
const int rs=12, en=11, d4=2, d5=3, d6=4, d7=6;
const int RLED=1;
const int WLED=13;
const int sensor_AOUTPin=A3;
const int sensor_DOUTPin=7;
int dcmotorPin=5;
int buzzer=8;
LiquidCrystal lcd (rs, en, d4, d5, d6, d7);
#define sensor A3
#define RLED 1
#define WLED 13
#define motor 5
void setup ()
{
pinMode (sensor, INPUT);
pinMode (motor, OUTPUT);
pinMode (RLED, OUTPUT);
pinMode (WLED, OUTPUT);

40
pinMode (buzzer, OUTPUT);
delay (10000);
lcd.begin(16,2);
lcd.print("ENGINEERING");
lcd.setCursor(0,1);
lcd.print("PROJECT");
delay (2000);
lcd.begin(16,2);
lcd.print("VEHICLE IGNITION");
lcd.setCursor(0,1);
lcd.print ("LOCK SYSTEM");
delay (2000);
lcd. begin (16,2);
lcd.print("PROVIDE");
lcd. setCursor (0,1);
lcd.print ("BREATH SAMPLE...");
delay (5000);
digitalWrite (buzzer, HIGH);
delay (2000);
digitalWrite (buzzer, LOW);
lcd.begin(16,2);
lcd.print ("ANALYZING...");
delay (10000);

41
lcd.clear();
}
void loop ()
{
float adcValue=0;
for (int i=0; i<10; i++)
{
adcValue+= analogRead(sensor);
delay (10);
}
float v= (adcValue/10) × (5.0/1024.0);
float mgL= 0.67 × v;
lcd.setCursor(0,0);
lcd.print("BAC: ");
lcd.print(mgL,4);
lcd.print(" mg/L ");
lcd.setCursor(0,1);
if(mgL > 1.5)
{
lcd.print("Fail,EngineLock");
digitalWrite (RLED, HIGH);
digitalWrite (WLED, LOW);

42
digitalWrite (buzzer, HIGH);
digitalWrite (motor, LOW);
}
else
{
lcd.print ("Pass, EngineStart");
digitalWrite (RLED, LOW);
digitalWrite (WLED, HIGH);
digitalWrite (buzzer, LOW);
digitalWrite (motor, HIGH);
}
delay (100);
}

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