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Senior Design ii


Title: Senior Design ii Author: Leon Guo Last modified by: Ashish Created Date: 2/2/2010 11:45:07 PM Document presentation format: On-screen Show (4:3) – PowerPoint PPT presentation

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Title: Senior Design ii

Senior Design ii
  • Breathalyzer Interlock system
  • By Xi Guo Ashish Thomas Brandon Gilzean
    Clinton Thomas

Project Description
  • A system to designed to deter individuals from
    operating a motor vehicle while under the
    influence of alcohol.
  • Highly accurate and portable alcohol sensing unit
    allows the operator to monitor their level of
    intoxication while away from the motor vehicle
  • Integrated automobile control unit prevents the
    vehicle from operating without a successful
    initial reading, then conducts rolling retests to
    verify driver sobriety during vehicle operation
  • Logs of activity maintained by automobile unit
    for retrieval during calibration by law

Motivation and Goals
  • Original concept was personal alcohol measurement
    device powered by a smartphone (iPhone, Android,
  • Platform and Business considerations lead to the
    determination to make a standalone device
  • Evaluation of work quantity lead to the marriage
    of alcohol detection device with automobile
    interlock unit
  • Goal is to develop a system that can meet
    National Highway Safety and Transportation Agency
    certification for alcohol detection interlock

Trade Study Breathalyzers
  • Personal breathalyzers utilize silicon dioxide
    based ethanol sensors, reducing both cost and
  • Unique air channel design that folds into the
    case enclosure. This will be modeled or acquired
    for Voog
  • Simple means of communication using speaker and
    2-Digit 7-Segment display
  • Small and lightweight, powered by
    non-rechargeable AA alkaline batteries

Trade Study Ignition Interlock
  • Smart Start Model 20-20 evaluated as the most
    effective and complete solution currently
  • Typical Interlocks utilize a zero-tolerance
    policy, meaning interlock engages between
    0.02-0.04 BAC
  • No available model in the market can completely
    prevent spoofing, only deter and catch for later

Project Overview
  • Hand-Held Unit
  • Handles user interaction and processes sensory
  • Powered by onboard Li-ion battery
  • Wireless Communication with automobile control
  • Control Box
  • Requests validation from handheld unit
  • Establishes vehicle state, logs input data

System Logic Displays
  • Introduction to System Logic
  • FPGA vs. Microcontroller
  • Microcontroller PIC18F, Texas Instrument MSP430
  • Display Seven-Segment Display, Dot-Matrix
    Display, Liquid Crystal Display

Introduction System Logic
  • The system level design for both the handheld
    breathalyzer unit, as well as the automobile
    control unit, calls for the use of programmable
  • This is necessary for the successful
    interpretation of output signals from the
    sensors, translating user input into device
    functionality, displaying information related to
    the current state of the device, as well as
    communication with other devices in the system.

Field-Programmable Gate Array
  • Integrated-circuit designed to be programmed
    after it has been manufactured
  • Advantages
  • Using languages such as VHDL and Verilog you can
    create complex logic structures.
  • FPGA is extremely flexible (implement processors,
    multipliers, network protocols)
  • Disadvantages
  • More complex to program than microcontroller
  • Power Consumption

  • Small computer on a singleintegrated
    circuit consisting internally of a relatively
    simple CPU, clock, timers, I/O ports, and memory.
  • Advantages
  • Using languages such as C/C Assembly
  • Low cost
  • Disadvantages
  • Have to design a microcontroller into a circuit
    and build it
  • Paying for functionality that is not being used

  • Memory Data storage, Computationetc
  • Communication RS232, USBetc
  • Wireless Capabilities Ability to transmit and
    receive data

Microcontroller (PIC18F)
  • PIC18F
  • 10-bit Analog-to-Digital Converter
  • Two Capture/Compare/PWM (CCP) modules.
  • 3-wire SPI (supports all 4 SPI modes)
  • I2C Master and Slave mode
  • Low power
  • USB V2.0 Compliant
  • Memory 32 Kbytes

Microcontroller (MSP430)
  • Texas Instrument MSP430F2274
  • Low voltage power supply requirements (1.8 VDC
    3.6 VDC)
  • Universal Serial Interface, configurable as
    either I2C, SPI, or UART for RS232 serial
  • Available Analog-to-Digital converters with
    10/12/16 bits of resolution
  • Assembly or C/C
  • Memory 32Kbytes Flash, 1Kbytes RAM

Microcontroller (MSP430)
Display Human Interface
  • Seven-Segment Display
  • Arabic numerals 0 to 9
  • General use
  • Dot-Matrix Display
  • Simple display limited resolution
  • Liquid Crystal Display
  • Great for character resolution
  • Refresh Rate

LCD Display - LCD0821
  • RS-232/TTL and I2C protocols
  • Communication speeds, up to 57.6 kbps for RS-232
    and 400 kbps for I2C
  • extreme environments of -20C to 70C

  • Alcohol Gas Sensor
  • Semi-Conductor (MQ-3) vs. Fuel Cell (002-MS3)
  • Differential Pressure Sensor
  • Silicon Microstructures (SM-5852)

Alcohol Sensor
  • Operating Condition and Requirements
  • Maximum Operating Temperature 90C
  • Recommend Operation Temperature lt70C
  • Shunt Resistor value 220-300ohm

Alcohol Sensor Output
  • Testing Condition
  • Room Temperature
  • 0.5ml gas sample
  • 0.160 BAC

Region of Interestlt0.04 BAC (User will not be
able to start the vehicle)
Alcohol Sensor Calibration
  • Sensor Output will be calibrated against known
    values using Lifeloc Dry Gas Calibration Kit
  • Typically, dry gas alcohol calibration requires a
    5-6 compensation value to approximate breath
  • Values will be measured using a
    laboratory-formulated alcohol standard of
    particular concentration, representing BAC values
    of 0.02 to 0.10

Differential Pressure Sensor
  • Object To detect sufficient breath sample has
    been provided.
  • Option A Tungsten Hot wire Anemometer
  • Electrical Resistance varies with the change in
    temperature due to breath sample
  • Cons Cant detect the quantity of breath sample
    obtained. Expensive. Not available as discrete
  • Option B SI-Micro Pressure Sensor
  • Pressure detection range 0.15-3 Psi (Human
    breath sample (1.5 to 2.5 Psi)
  • Cons Difficult to obtain from chosen
    manufacturer,difficult to mount.

Differential Pressure Sensor
Power Supply
  • How to power
  • Ability to hardwire into vehicles electrical
    system (in-car unit)
  • Recharge on-board battery with same circuit board
    (portable unit)
  • Utilize external wall wart to recharge battery,
    or cigarette lighter connection (portable unit).
    So 12V primary input.
  • Various power needs of components in both units
    will require a power supply with multiple

Power Requirements
Component Max Current Draw (mA) Recommended Voltage (VDC) Power Consumption (W)
Display 105 5 0.525
Microcontroller (wireless on) 95 3.3 0.3135
Sensor 650 5 3.25
Charging IC 600 9 5.4
Speaker 60 5 0.3
LEDs, etc 100 9 0.9
Total 1610 -- 10.69
Power Requirements (contd)
  • While maximum draw possible is 1.6A, it is at
    various voltages and not all will be drawing at
    the same time for a significant period of time
  • Multiple voltages are needed for multiple
    components. Therefore, will utilize voltage
    regulation to generate multiple output voltages
    from singular 12VDC input

Power Distribution Scheme
Portable Unit
Control Unit
Implementing Power Scheme
  • For our application, voltage dividers do not
    offer voltage stabilization, and are fairly
    inefficient. They also lack any sort of basic
    power protection (short circuit, overcurrent,
    overvoltage, thermal overload, etc.).
  • Zener diodes allow a stable output voltage but
    again, lack more robust power event protection.
  • Use LDO voltage regulator ICs. Switching
    regulators were considered, but due to their
    buggy reputations, were not used. They also take
    up slightly more space on the PCB land
    configuration due to a need for a larger
    (compared to LDO) supporting circuit. Heatsinking
    will be used as needed. 9VDC, 5VDC, and 3.3VDC
    are needed.

  • Portable unit needed to be portable, but also not
    impractical to use by having to replace
    disposable batteries. Since highest regulator to
    be served by battery is 5V, a 7.4V battery should
  • Load and current draw expectations made
    conventional alkalines impractical.
  • Due to size, energy density, as well as
    flexibility in recharging, lithium ion
    rechargeable batteries were chosen.

Expected Battery Runtime?
31.875 minutes
7.4V 850 mAh Li-Ion Battery with Integral
Protection PCB. gt1C safe discharge rate.
Charging the Battery
  • However, a charging circuit is now required.
    Lithium ion batteries require more care in
    charging, as improper charging can result in a
    fire or explosion not desirable for any user,
    especially an inebriated user
  • Circuit to right. Will be a two cell battery
    (3.7V2 7.4V)

Reprinted with Permission of
Charging the Battery (contd)
  • However, the area required on the PCB for this
    configuration is too great it also is not
    intelligent. It cannot automatically detect a
    severely discharged or overchargedbattery and
    cannot switch charging modes to compensate.
  • Use Texas Instruments BQ24005. A complete,
    integrated charging IC for use with two cell
    LiIon and LiPoly batteries
  • Heat issues are addressed by soldering a thermal
    pad on the bottom of IC to a copper pad in the
    PCB the PCB becomes a heatsink.

Jumper Portable Unit Config Base Unit Config
J1 Closed Open
J2 Open Closed
J3 Closed Open
To allow usage of same board for both fixed and
portable power application, a set of three
jumpers can be adjusted to allow for either
Physical Implementation
  • Since small size, reliability, and quality are
    all primary concerns of our overall project, we
    decided to use a PCB.
  • PCB Requirements
  • Compact 2 in. x 3 in. (6 in.2 total area). This
    is slightly smaller than an average credit card.
  • Must accommodate microcontroller board within
    PCB area
  • Design so a single board can be used for both
    portable and base/control units
  • Design for optimal power flow, and minimize
    capacitive, inductive, and other crosstalk
    effects from traces, especially between analog
    and digital I/O lines.

Physical Implementation (contd)
  • Design considerations
  • 32 mil for width of power traces
  • 15 mil for width of signal traces
  • 25 mil minimum for signal trace spacing
  • Mostly dedicated ground plane for robust ground
  • Two layer to save on cost.
  • All outputs should have standard 0.1 in. spacing
    (2.54 mm) to accommodate standard pin headers.
    This will mostly avoid the need to solder
    components directly to the board, easing
    debugging and future changes.
  • Wide traces to small pads on the charging IC
    should be necked near pad interface

(No Transcript)
PCB Manufacturer Choice
  • Used (Sunstone Circuits)
  • Used PCB123 PCB layout and schematic editor
  • With silkscreen on top only, 1 oz copper
    thickness, soldermask, and our 6 sq. in., the per
    board price is 32.48 for 8 boards. (32.48 8
  • Lead time of three business days when order is
    submitted before 12 PM PST

Enclosure Hand-held Control box
  • Requirements (Hand-held unit)
  • Dimensions 4.5x2.5x1.5in
  • Physically Appealing
  • Resources, Materials and Skill sets
  • Photoshop Software
  • SolidWorks and/or AutoCAD Software
  • Industrial Engineering Rapid Prototyping lab
  • Fabrication material

Enclosure Contingency Plan
  • Pactec Enclosures
  • PPT 3468

Signal Acquisition
  • Alcohol Concentration will be determined using a
    Peak Measurement method
  • Output measured over small load resistor (220
    390 ohms)
  • Voltage is converted into discrete 10-bit integer
    representation by ADC with internal 1.5V
  • Output represents the maximum alcohol
    concentration detected by the sensor in
  • Airflow pressure will be queried from the
    differential sensor utilizing I2C, returned from
    the sensors onboard DSP.

BAC Measurement
  • Micrograms of alcohol is converted to BAC using
    the Blood/Breath Partition Ratio, 23001 US,
    21001 UK
  • Assumption is made that test is post-absorbitive,
    meaning the alcohol is fully absorbed and in
    bodily equilibrium
  • Approximate values are as follows1.0 BAC 1cg
    ETOH/mL blood 9.43 mg ETOH/g blood1ppm 1 ug
    ETOH/g blood 1.06 ug ETOH/mL blood1.06g blood
    1mL blood188.6 ug/mL 377.2 ug/mL is blood
    concentration for 0.02-0.0482 ng/mL 164 ng/mL
    will be range of BrAC
  • Assumptions of flow rate will be evaluated during
    assembly and calibration to determine breath
    sample quantity

Software Development
  • Software will be written using IAR Embedded
  • Kickstart version for MSP430 provided by TI
    limits program size to 4K. Full version does not
    have this limit, but costs lots of
  • Software will be written in C, with inline
    assembly for MSP430 where needed

Software gt Hardware always
  • What happens when you find out after purchasing
    your hardware that it cannot achieve all the
    functionality you believed it could?
  • MSP430F2274 provides a universal serial UART for
    I2C, SPI, RS232, etc., which just so happens to
    be used by the CC2500 transceiver
  • Communications with peripheral devices and
    sensors will be accomplished through an I2C
    serial bus
  • Luckily for us, the right combination of
    configurable GPIO pins and software can save our
    project, utilizing a technique called

What is Bit-Banging?
  • A technique used for serial communications
    utilizing software instead of dedicated hardware
  • Software sets and samples the state of pins on
    the microcontroller, responsible for timing,
    signal levels, synchronization, etc.
  • Can reduce costs in a design by implementing
    features that are not designed directly into the
    hardware (or make up for a lack of foresight)
  • Considered a hack, takes more CPU time and
    resource, signal is usually much uglier than
    dedicated hardware would provide

Inter-Integrated Circuit (I2C)
  • Daisy-chained serial peripheral bus designed for
    simple slave-to-master device communications
  • Only requires two lines, SCL (clock) and SDA
  • Each device is given an address on the bus,
    configured by software
  • Communications initiated with START and STOP
  • First byte is the address of the device the
    master will communicate with, then the desired
    direction of communication (write/read), followed
    by an ACK from the slave device

Inter-Integrated Circuit (I2C)
  • Each byte is followed by a START message until
    desired end of transmission, which is indicated
    with a STOP message

System Diagram
Software State Transition
  • Hand Held Unit (Passive Device)
  • Wait State Processing input from user
  • Processing State Receiving and processing
    sensor data
  • Display State/Transfer Display to LCD,
  • Control Box Unit (Active Device)
  • Wait State Receive wireless transmission
  • Functional States Enable, disable, and alert
  • Idle State Counting down to the rolling retest.

Transition State Diagram
  • Hand Held Unit
    Control Box Unit

Block Diagrams
Control Box Unit
Hand Held Unit
Interlock and Demo Setup
  • The interlock will prevent the vehicle from
    starting if the users BAC is deemed to be too
  • Will do this by routing the fuel pumps power
    through a relay this will prevent starting
    whether the starter or clutch (bump start) is
    used to start the car
  • Signal from microcontroller will control the
    relay, which will switch the higher amperage fuel
    pump power. Protection diode will be used across
  • For our demonstration, will use an RC car, as no
    actual vehicle is available for demo purposes

Interlock and Demo Setup (contd)
12V Constant (Car or RC Battery)
Fuse (15 A)
Fuel Pump (or RC car motor)
Work Distribution
X. Guo Thomas B. Gilzean C. Thomas
Case Enclosure Power Delivery Control Software Utiliity Software
Sensor Selection Charging Circuit Communications (wireless) Communications (peripheral)
Layout and Design PCB Layout and Design Regression Testing PCB Layout and Design

Project Status
Project to date
Hardware Design
Testing and Calibration
Received FundingCEI
April 28th, 2010Final Presentation
Software Design
Final Documentation
Part Acquisition
PCB Design
Project Budget 1000
Item Cost Spent
PCB 32.48 (8) 260
Differential Pressure Sensor 0.00
RC Car 40 40
Battery Charger 45 45
Enclosures 15 15
12V Relay 3 (2) 6
Alcohol Sensor 24.15(2) 25
Voltage Regulator 1.50 (10) 15
Speakers and Buzzers 10 (2) 20
Dry Alcohol Standard Test 325 0.00
Total 750.84 425.84