Final Report
MARE Windshield Wiper System
ECE4007 Senior Design Project
Section L02, Group 4
Michael Whitfield
Eric Williams
Anthony Harris
Renaud Moussounda
Submitted
December 11, 2007
TABLE OF CONTENTS
Executive Summary ...................................................................................................................... ii
1. Introduction ............................................................................................................................. 1
1.1. Objective ............................................................................................................................ 1
1.2. Motivation.......................................................................................................................... 1
1.3. Background ........................................................................................................................ 2
2. Product Description and Goals .............................................................................................. 3
3. Technical Specifications ......................................................................................................... 4
4. Design Approach and Details ................................................................................................. 4
4.1. Design Approach ............................................................................................................... 4
4.2. Codes and Standards ........................................................................................................ 13
4.3. Constraints, Alternatives, Tradeoffs ................................................................................ 14
5. Schedule, Tasks, and Milestones.......................................................................................... 14
6. Project Demonstration.......................................................................................................... 18
7. Marketing and Cost Analysis ............................................................................................... 18
7.1. Marketing Analysis .......................................................................................................... 18
7.2. Cost Analysis ................................................................................................................... 21
8. Summary ................................................................................................................................ 23
9. References .............................................................................................................................. 24
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EXECUTIVE SUMMARY
The Michael, Anthony, Renaud, and Eric (MARE) automated windshield wiper system is
used to detect rainfall and activate an automobile windshield wipers without driver interaction.
The system was developed to mitigate driving distractions and allow drivers to focus on their
primary task of driving. The distraction eliminated with the development of this product is the
manual adjustment of windshield wipers when driving in precipitation. The few seconds that a
driver takes their attention off the road to adjust a knob while driving in poor weather conditions
could potentially lead to car accidents. The system uses a combination of impedance and
infrared sensors to detect rain and its intensity. The system contains a microcontroller that takes
in the input signals from the sensors and controls the operation of the windshield wipers based on
those input signals. The prototype demonstration shows the basic operation of the system in
standard conditions. The system responded successfully to rain simulations within the specified
amount of time. The IR sensor was not sensitive enough to control speed reliably, however, the
impedance sensors were able to compensate. Additional work worth consideration is a voice
activation feature, a more sensitive IR sensor, and a stable power supply circuitry. The prototype
cost to develop the system including labor and materials is $29,070. The manufacturing cost of
the system is $222 to produce per unit and would retail at $292, netting a profit of 22.9 percent.
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MARE Windshield Wiper System
1. INTRODUCTION
The team developed an autonomous windshield wiper system for automobiles using IR and
impedance sensors, a microcontroller, and signal conditioning circuitry. The sensors send an
input signal to the microcontroller that controls the wiper motor through interfacing with the
automobile wiper control circuitry. The motivation of the project centered on developing a
reliable automatic windshield wiper system that is commercially available to a large market of
automobile owners. Research was done on similar products in the market and articles from
academic sources for the foundation of our design approach.
1.1.
Objective
The project aims to develop an automatic windshield wiper system that automates the
process of the driver’s manual response to rain on the windshield. Car manufacturers will be the
primary customers for system integration into their future automobile lines, and the secondary
customers will be individual automobile owners, using the system as an after-market product.
Motivation
The National Highway and Transportation Safety Association reports that twenty-six
percent of all car accidents are caused by distractions due to talking on cell phones, eating while
driving, and other similar distractions that take a driver’s focus off the road [1]. The distraction
considered in this project is the adjustment of wiper speed based on the intensity of precipitation
falling. By eliminating the need for drivers to adjust wiper speed while driving, the number of
accidents caused by distraction can be slightly reduced.
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Similar systems are currently installed in some luxury vehicles [1], but such systems have
not reached the massive economy vehicle market. The low-cost solution proposed by the design
will most importantly satisfy the safety and performance requirements needed for the driver at a
more reasonable price. The windshield wiper system will manage to do this by combining the
performance of an inexpensive infrared sensor and impedance sensors. The project
demonstration will determine how our system performs against existing systems, and the cost
analysis will compare against the cost of existing products.
1.2.
Background
There are products similar to the MARE system that are currently on the market. Existing
comparable products on the market include the Rain Tracker system by Opto-Electronic Design,
Inc. [2] and the TRW rain sensor [3]. Both the TRW rain sensor and the Rain Tracker detect rain
through IR sensors that are located behind the rear view mirror and interpret changes in light
patterns that are caused by the precipitation on the windshield [2].
The improvement of existing windshield wiper systems is still an area of interest for
researchers. In 2001, researchers presented a report at an IEEE conference that concentrated on
the design and implementation of a rain sensing system [4]. In 2005, they proposed a windshield
wiper system that used small cameras installed in cars’ windshield to detect rain [5].
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2. PRODUCT DESCRIPTION AND GOALS
The product goals are given by the following criteria:

Detect rainfall on windshield

Detect intensity of rainfall

Activate windshield wipers automatically once rainfall is detected

Avoid adverse effects of extraneous and environmental factors

Meet or exceed the response time of the driver

Make adaptable to all vehicles

Develop high reliability (less than five percent intensity detection errors)

Create with ease of installation
The primary goal of MARE is to automatically detect rainfall and activate the windshield
wipers without driver interaction. This system should respond to rainfall in a similar manner as
if the driver were manually controlling his or her windshield wipers. In the project proposal, the
team included a voice-activation feature as a project goal. During prototype development it
became evident to the team that the inclusion of the speech recognition feature would require
more development hours than available, thus adversely affecting the project deadline; therefore,
this feature was not included in the prototype. The automated windshield wiper system consists
of the following:

sensors that detect rain and its intensity

a microcontroller that outputs a control signal to the motor control circuitry

signal-conditioning circuitry to interface with all the components in system
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3. TECHNICAL SPECIFICATIONS
The project focused on building a working prototype. As a result, the technical specifications
were derived from the need to have a reliable and adaptable system. Table 1 below summarizes
the most important specifications met. While power and weight specifications are important,
they were not crucial to the design of the prototype.
Table 1 Technical Design Specifications
Objectives
Reliability
Adaptability
Characteristics
Desired Specifications
Actual Specifications
System Failure Rate
0- 5 %
1%
System Response Time
0- 500 ms
250 ms
Operational Temperature
-40 to 84 °C
0- 30 °C
Voltage Range
0-12 V
0-12 V
The prototype successfully exceeds the detection failure rate. The actual low failure rate was
implemented in software by rejecting small disturbances in sensor output voltages. The system
response time criterion was met mainly by running the microcontroller at higher frequencies (816 MHz). Unfortunately, the system was only tested at room temperature (25°C); therefore, there
is no data on how the system performs in freezing or extremely hot conditions.
4. DESIGN APPROACH AND DETAILS
4.1.
Design Approach
4.1.1. High-level Functional Blocks
The design of the system consists of producing a high level functional diagram as shown in
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Figure 1. The system is able to detect the presence of rain droplets, process that data coming
from the sensors, and enable and control the motor.
Data
Processing
Rain
Detection
Motor
Control
Figure 1 High-level Functional Block Diagram
The rain detection box contains a series of rain sensors. The data processing unit encloses
the microcontroller, and the motor control module is composed of the wiper motor and its control
circuit. After establishing the functional diagram, a high level system block diagram was drawn.
The second diagram represents a more detailed version of the functional diagram. Figure 2
depicts the contents of each unit.
Rain Detection
Impedance
Sensor
Input
Signal
Module
Data Processing
Microcontroller
Output
Signal
Module
IR
Sensor
User
Interface
Motor
Motor
Controller
Motor Control
Figure 2 High-level System Block Diagram
The rain detection unit uses two types of sensors whose outputs are normalized by an input
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signal module. The data processing is performed by a microcontroller, and its results are fed into
an output signal module which is the input to the motor control box. The two signal modules
were needed for interfacing between all the units.
4.1.2.
Rain Detection Unit
4.1.2.1. Impedance Sensors
The system detects rain by using two sorts of sensors. One of them is the impedance grid
sensor shown in Error! Reference source not found.. The grid is made of two comb-like
copper plates separated by a minimum distance of
1
8
in. The sensor is glued to the windshield
glass with the help of a strong adhesive material. The thin configuration of the plates allows the
wiper to slide over without peeling them off. When the plates are dry, the resistance between the
two plates is very high, but when water is between the plates, current can flow between the
plates, thus decreasing the resistance. This operation allows this design to be used as a rain
sensor. The sensor becomes
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Figure 3 Impedance Grid Sensor with Water Varying Electrical Conduction
operational when one plate is connected to a power source, and the other plate is taken as the
sensor output.
A common design challenge consists of finding the sensitivity that minimizes the detection
failure rate. In other words, the separation between the plates is strongly related to the sensors’
sensitivity and its detection rate [4]. Increasing the distance between the plates decreases the
failure rate but it also decreases the sensitivity of the sensor which is inversely related to the
system response time. Another design issue with the impedance grid sensor is the fact that it can
act as an antenna and produce a floating voltage which can trigger a false detection. A solution
to the problem consists of reducing the sensor’s size and grounding the output signal
appropriately. Two other issues of concern are copper oxidation (rust) and physical deformation
caused by the frictional motion of the wipers over the grid sensor. The grid sensor in figure 3 is
effective at detecting rain, but it does a poor job relaying how much water is on the windshield
glass at any point in time. Since the system should be fully automatic, there is a need to develop
a way to measure the average distribution of water falling on the glass in order to control the
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wiper’s speed. A modified version of the impedance sensor was designed to provide better
intensity measurements. The new design consists of spacing isolated vertical plates from a
single power plate as shown in Figure 4. Measuring the voltage at these different plates provides
a more accurate way of determining the rate of rainfall. The sensing device can be mounted
anywhere on the windshield where there is no contact with the wipers. This upgraded version of
rain sensor suffers from the same issues as its predecessor, but it provides more functionality.
Figure 4 Three-channel Rain Sensor for Speed Control
4.1.2.2. Optical Sensors
The optical sensors are used to bounce beams of light through the windshield, and look for
disturbances in the beams caused by raindrops at the outside surface of the windshield. The rain
sensor has an emitter that emits pulses of light, coupled into the windshield with a lens. These
beams travel through the windshield at about 45 degrees [2]. Through research it was anticipated
that the infra-red beams were to be totally reflected by the outside surface of the windshield into
the receiver [2]. However, when testing the analog IR sensor supplied by Optek Inc., it was
determined that the infra-red beams were not totally reflected by the windshield, but that the
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infra-red beams were approximately 30% reflected by the outside surface of the windshield.
Troubleshooting this issue included using different types of glass to reflect the IR beams and
comparing that output with the results of reflecting the IR beams off a white sheet of paper. In
conclusion, it was determined that the light beams from the IR sensors were not totally reflected
by any type of glass and therefore the design approach was modified. Although the glass did not
reflect 100 percent of the light emitted, there was enough light reflected by the glass to detect the
change in reflectivity due to a raindrop. The downfall is that the rain threshold for the sensor
was lowered and it was not as easy to determine when moisture was present. If rain drops are
present on the outside surface of the windshield, some of the beams escape and this reduces the
intensity of the beams. The detector will measure this reduction in intensity and communicate
that to the rest of the system that actuates the windshield wipers. Figure 5 on page 10 shows a
diagram of the operation.
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Figure 5 Diagrams of IR Sensor
4.1.2.3. Input Signal Module
The input signal module’s first function is to normalize all sensor signals so that the
microcontroller can safely interface with the rain detection unit by limiting the amount of
incoming current. Figure 6 depicts the circuit implementing the module. In addition, it hosts the
user-controlled sensitivity circuits. Each sensor is dedicated a separate part within the input
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signal module. Figure 6 shows the internal circuit corresponding to the impedance grid sensor.
All other sensors have a similar input circuit.
Figure 6 Input Circuit for Impedance Grid Sensor
The sensitivity is controlled by a potentiometer that can be manually tuned by a user. The
protective resistor below the potentiometer makes sure that the overall system remains stable and
functional regardless of users’ settings. The capacitor introduces a low-pass filter that helps
stabilize the sensor output so that the microcontroller makes more accurate readings. The input
circuit also solves the floating voltage problem discussed earlier by providing a ground between
the sensor and the microcontroller.
4.1.3.
Data Processing Unit
4.1.3.1. Microcontroller and Control Logic
The data processing unit is composed of a microcontroller and an output signal module.
The AVR Atmega8 microcontroller was finally selected over the initial TI MSP430 because of
its higher output power and number of analog-to-digital channels. The communication between
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the computer programmer and the microcontroller is done via serial peripheral interface bus
(SPI). The program executed by the microcontroller is shown in Figure 7.
Figure 7 Summary of System Control Logic
Once the system is enabled, the system initialization block checks if the sensors are
operational, sets the corresponding input and output pins, and determines if the power is high
enough to keep the microcontroller running. After performing all the necessary checks, the
program reads voltages from the impedance grid sensor and IR sensor in a sequential order. If
water is detected, the microcontroller sends a signal to a power relay so that the wiper motor is
activated at its lowest speed. Afterward, the microcontroller reads the speed control sensor and
determines the appropriate motor speed by powering other relays. The additional relays affects
change the amount of power going to the motor. The loop continues as long as all the sensors
detect water on the windshield. The C code implementing the control logiv discussed above is in
Appendix A.
4.1.3.2. Output Signal Module
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The output signal module is the bridge between the design system and the existing
automobile windshield wiper system. Figure 8 depicts how the microcontroller is connected to
the relays driving the motor control board.
Figure 8 Relays and Microcontroller Connections
The control process for the project stops after the output signal module because the motor control
unit is foreign to the system. However, for installation purposes, the user should be able to
integrate the design product to an existing automobile. Therefore, only general interfacing
information is required to be provided to the user. However, in order to demonstrate the overall
project, a motor and a control module circuit were acquired and tested.
4.2.
Codes and Standards
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The team adhered to the codes and standards focused on interfacing the system with the
automobile controls. The sensor and the microcontroller are governed by universal standards
such as the NEC, the National Electric Code [7]. The microcontroller will also abide by the SPI
protocol in order to load in a program from the PC. In automobiles, information from one sensor
and/or data from one system can be communicated with other systems using multiplex wiring to
reduce the number of sensors and the amount of wire used in a vehicle [7]. Two predominant
protocols have emerged as standards, but several other protocols exist that are specific to
manufacturers' applications. The Society of Automotive Engineers (SAE) has established SAE
J1850 as the standard for multiplexing and data communications in U.S. automobiles [8].
However, data communications for trucks and On-Board Diagnostics II (OBDII) are based on
the Controller Area Network (CAN) protocol developed by Robert Bosch GmbH [9].
The SAE Vehicle Network for Multiplexing and Data Communications (Multiplex)
Committee has defined three classes of vehicle networks: Classes A, B and C [8]. Class A is for
low-speed applications such as body lighting [8]. Class B is for data transfer between nodes to
eliminate redundant sensors and other system elements [8]. Class C is for high-speed
communications and data rates typically associated with real-time control systems [8]. The
project will be considered as a class C application.
4.3.
Constraints, Alternatives, Tradeoffs
The design was constrained by patent infringement of similar products on the market such as
the Rain Tracker system which uses a similar optical approach to detect rain. However, time and
funds were the primary constraints that limited the scope and quality of the overall project.
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One alternative design for rain detection was to replace the entire rain detection unit by a
video camera. The stream of images could have been processed and analyzed to determine the
state of the windshield. However, the approach was discarded from the beginning because of
financial reasons and limited expertise on image processing algorithms. Moreover, having a
camera behind a windshield glass for rain detection might not be an attractive feature for many
customers.
There is a design tradeoff between the amount of windshield surface covered by the rain
sensors and the ability of the system to detect actual raindrops [4]. If the sensors were able to
monitor the entire windshield surface, the system would be more reliable, but the windshield
would be cluttered and it would be hard to see through the glass. In order to maximize the
detection rate and maintain visibility, the sensors were placed near the driver's side.
5. SCHEDULE, TASKS, AND MILESTONES
The Gantt chart in Figure 9 shows the building blocks and milestones of the project and the
completion dates that actually occurred. A full-size version of the Gantt chart is provided in
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Figure 9 Project Gantt Chart
Appendix B . Tasks were added and subtracted to the Gantt chart throughout the project
development. The team made adjustments to the schedule at the very outset of the project. The
degree of difficulty of the tasks is proportional to the task length in the chart. Much time and
resources were focused on assembling the components of each of the sub-systems, developing
and debugging the microcontroller code, building the system apparatus and integrating the subsystems. At the onset of the project, the team met to discuss the responsibility of each team
member. Renaud Moussounda handled all the software applications of the project (principally
programming the microcontroller) as well as designed the impedance sensors. He also designed
and maintained the project website. Eric Williams worked on the infrared sensor, and
investigated a comparable product on the market. Michael Whitfield handled administrative
responsibilities including weekly status reports to project advisors and preliminary technical
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writing of the proposal. Michael was also responsible for determining whether the voiceactivation feature was feasible. Anthony Harris developed the prototype apparatus, and
researched how the system interfaces with the existing windshield wiper controls. The Gantt
chart reflects the duration and completion dates of these aspects of the project.
6. PROJECT DEMONSTRATION
The project demonstration for the MARE windshield wiper system prototype tests for the
successful detection of rain, tests for the intensity of that rain, and activates one of four speeds of
the windshield wiper. The system activates within 500 milliseconds as originally specified under
the voltage requirements. The prototype achieves all the product goals and specifications set out
by the proposal, however, the temperature range specification was not able to be tested. The
prototype was tested in a room temperature environment so additional testing need be performed
to determine whether the system has the same functionality at the extreme temperatures of the
technical specifications. Figure 10 shows a photograph of the actual prototype of the project. As
can be seen from the figure roughly 3 ft of plexiglass, mounted in a wooden frame, serves as the
automobile windshield. The plexiglass is angled at about 37 degrees to mimic automobile
windshields. Mounted below the plexiglass are the wiper linkage kit as well as the wiper pulse
motor controls and wiper motor. The IR sensors are located at position ‘A’ on the figure and the
impedance sensors are located at position ‘B.’ The system controls are housed behind the
plexiglass including the microcontroller and all input/output signal modules. To start the system,
the user would first connect the power leads to the breadboard with a DC power supply. System
should be supplied with a voltage greater than 5 volts. User should be sure to connect the
positive terminal of the voltage source to the red post of the breadboard #1 and the negative
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terminal to the black post. Once the system is powered up, the user will also need to connect 12
V and GND to breadboard #2 which is connected to the relays that control the wiper motor
housed below the plexiglass. After these connections are made, the user will turn on the system
by switching on the power switch on breadboard #1. Rain will be simulated using a spray bottle;
the user will spray water on the glass near any one of the sensors and the system will react within
500 milliseconds. The speeds of the windshield wiper will vary depending on the amount of
water sprayed onto the plexiglass.
Breadboard #2
Breadboard #1
Figure 10.a Microncontroller and Relays
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B
A
B
Figure 10.b Project Prototype
7. MARKETING AND COST ANALYSIS
7.1.
Marketing Analysis
The MARE windshield wiper system unique blend of dual sensor technologies enables
redundancy in moisture detection. The impedance sensors and IR sensor work in conjunction to
provide optimal wiper actuation. Competitor wiper systems, such as the TRW Rain tracker,
implement a single sensor topology for rain detection. While this topology lowers the product
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price, the system is bound by single point failure. If the IR sensor malfunctions, the tracker
system is inoperable. The dual sensor topology of MARE allows the system to maintain
operability in the event that either sensor, IR or Impedance, malfunction. Herein lays the
competitive advantage of the MARE system. The team believes that this competitive advantage
justifies the slightly higher price of the MARE system over its competitors.
The marketing strategy for MARE focuses on its appeal to two primary clientele: luxury
automobile owners and elderly drivers. Luxury automobile owners would enjoy the accentuation
of their driving experience; elderly drivers the ease of use of the system. The team will make use
of product demonstrations at AARP (American Association of Retired Persons) Conventions and
Automobile shows to market to the primary target consumers. This approach mitigates the
costly advertising scheme and passes on those savings to the consumer in the form of a lower
product price.
7.2.
Cost Analysis
Prototype Cost Analysis
The prototype analysis demonstrates the costs associated with constructing the MARE
system. The analysis considers the labor costs, parts & materials cost, and production cost of the
complete system. The labor costs were broken down into three separate categories:
Administrative (Project Meetings, Design Presentations, Status Reports, Progress Reports, and
Written Proposals); Design (Sensor Design, Apparatus Construction, C-Code, and Project
Testing); and Research (Wiper Motor Investigation; Wiper linkage acquisition; Sensor
investigation; etc). The team created an excel spread sheet that tracks each of these headings for
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each group member. Figure 1 displays an example spreadsheet of project hour figures. The
complete excel sheet with accurate labor figures can be found in Appendix C.
Figure 11 Project Hours Chart
The team spent a total of 490 hours on constructing the project prototype. At an hourly rate of
$30.00/hr the pure labor cost amounts to $14,700. With the addition of employee fringe benefits
and medical the accrued labor cost totals $18,375. A complete account of these figures can be
seen in Appendix C.
The materials associated with the design of the MARE system consist of materials purchased
that were used in the prototype and materials purchased that were not implemented in the design.
Both costs are provided to show the cost of materials for the prototype and the complete cost of
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materials purchased. The complete cost of materials used in the prototype design totaled
$334.13. The complete cost of materials purchased for the prototype design totaled $379.75.
The latter figure was used in conjunction with the prototype labor cost to determine the complete
prototype cost. With material and labor overhead accounted for the complete prototype cost
totals $29,070. The complete figures can be seen in Appendix C.
Product Analysis
The mass production cost of the MARE will be significantly lower than the prototype cost.
Primarily because materials used to construct the prototype (i.e. wiper motor, wood frame, wiper
linkage kit, and plexi-glass windshield) would be provided in the car assembly; the team need
only implement the sensors and electronics that function the MARE system. Consequently, the
team believes that the mass production material cost of each system to be roughly $60.00/unit.
Each unit will require no more than an hour for assembly and testing. Based on 10,000 units
sold per year at a price of $292/unit the team expects a 23.9% profit margin. Table 2displays the
overall figures and expected profit. The team expects to make $70.00 per unit sold. As better
methods of production are realized the team expects the cost of production to steadily decrease
consequently reducing the product price.
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Table 2 MARE Windshield Wiper System Expected Profit Expectations
Labor cost and Price Expectation
Based on:
10,000
Parts Cost
60
Assembly Labor
10
Testing Labor
10
Total Labor
20
Fringe Benefits, % of Labor
8
Subtotal
85
Overhead, % of Material, Labor & Fringe
47
Subtotal, Input Costs
132
Sales & Marketing Expense
73
Warranty & Support Expense
15
Amortized Development Costs
3
Subtotal, All Costs
222
Profit
70
Selling Price
$292
Total Revenue
$300,000
Total Profit
$48,093
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8. SUMMARY AND CONCLUSIONS
In conclusion, the automated windshield wiper system was designed, developed, and
demonstrated to detect rain and actuate the automobile windshield wipers based on the intensity
of that rain. The demonstration is able to simulate the operation of the system as if installed in
an automobile. The team was able to successfully complete the project and satisfactorily meet
the proposal goal of automating the driver’s response to rain within the specified amount of time
of 500 milliseconds. Though the MARE system functioned as desired, in retrospect the team
would have selected different design approaches. After noticing that more accuracy was
required from the IR sensor to adequately detect the intensity of rain the team would have
selected a more applicable IR sensor. In addition, the team would schedule project milestones
differently taking into consideration parts of the project that were most significant and
consequently required the most effort to complete. The initial goals and objectives were to
expand upon existing automatic windshield wiper technologies to make a more reliable yet
economically priced system. As shown by the project demonstration and the cost analysis, these
goals and objectives were met. Recommendations for future versions of the product include
using more sophisticated IR sensors, including a voice recognition feature, and raising all the
power windows in the vehicle when rain is detected. Although the project met our goals, another
production cycle should be initiated to improve the reliability of the system and include the
features mentioned in the future versions.
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REFERENCES
[1] NHTSA Data Sheet, 2001, Available HTTP: http://www-nrd.nhtsa.dot.gov/departments/nrd12/809-716/pages/longdesc.htm
[2] “The Rain Tracker Makes Driving More Enjoyable,” [Online Document], Available HTTP:
http://www.raintracker.com/ProductInfo.htm
[3] “TRW Automotive Electronics: Rain Sensor,” 2007, [Online Document], Available HTTP:
http://www.trw.com/images/rain_sensor.pdf
[4] M. Ucar, H. Ertunc, and O. Turkoglu, “The Design and Implementation of Rain Sensitive
Triggering System for Windshield Wiper Motor,” In IEEE IEMDC, 2001, pp. 329-336.
[5] H. Kurihata, T. Takahashi, I. Ide, Y. Mekada, H. Murase, Y. Tamatsu, and T. Miyahara,
“Rainy Weather Recognition from in-Vehicle Camera Images for Driver Assistance ,” In
IEEE Intelligent Vehicles Symposium, 2005, pp. 205-210
[6] HM Data Sheet, 2007, Available HTTP:
http://www.tranzistoare.ro/datasheets/2300/499674_DS.pdf
[7] National Fire Protection Association, 2007, [Online Document], Available HTTP:
http://www.nfpa.org/
[8] “SAE Standards Development,” Sep 2007, [Online Document], Available HTTP:
http://www.sae.org/standardsdev/
[9] “CAN Specification”, 1991, [Online Document], Available HTTP:
http://esd.cs.ucr.edu/webres/can20.pdf
[10] G. Muller, “Windshield Wiper System with Rain Detector,” U.S. patent no. 5015931, issued
June 11, 1991
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Appendix A—Microcontroller Code
/*
Georgia Institute of Technology
ECE 4884/4007
Group: 4
Project: Automatic Windshield Wiper System
File: code.c
Version: 2.0
Date: 12/07/07
*/
#include <avr/io.h>
#include <util/delay.h>
// define A/D channels
#define
#define
#define
#define
#define
IMP_SENSOR 0
HIGH_SENSOR 1
MED_SENSOR 2
LOW_SENSOR 3
IR_SENSOR 4
//define common threshold
#define THRESHOLD 127
#define IR_THRESHOLD 70
//define functions
void ioinit(void);
uint8_t read_adc(uint8_t channel);
void park_enable(void);
void intermittent_enable(void);
void low_enable(void);
void medium_enable(void);
void high_enable(void);
void delay_ms(uint16_t ms);
int main(void)
{
ioinit();
int temp = 0;
int zero_rotation = 4;
int low_rotation = 3;
int speed_loop;
park_enable();
while (1)
{
if (read_adc(IMP_SENSOR) >= THRESHOLD || read_adc(IR_SENSOR) <
IR_THRESHOLD)
{
if (!temp) {
intermittent_enable();
}
if(read_adc(IMP_SENSOR) >= THRESHOLD || read_adc(IR_SENSOR) <
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IR_THRESHOLD)
{
speed_loop = 1;
while (speed_loop)
{
if(read_adc(HIGH_SENSOR) >= THRESHOLD)
{
high_enable();
low_rotation = 4;
zero_rotation = 3;
temp = 0;
}
else
{
if(read_adc(MED_SENSOR) >= THRESHOLD)
{
medium_enable();
low_rotation = 3;
zero_rotation = 2;
temp = 0;
}
else
{
if (read_adc(LOW_SENSOR) >= THRESHOLD)
{
if (temp)
{
speed_loop = 0;
park_enable();
}
else
{
low_enable();
if (low_rotation < 0)
{
intermittent_enable();
if (zero_rotation < 0)
{
temp = 1;
}
zero_rotation--;
}
low_rotation--;
}
}
else
{
if (temp)
{
park_enable();
speed_loop = 0;
}
else
{
intermittent_enable();
if (zero_rotation < 0)
{
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temp = 1;
}
zero_rotation--;
}
}
}
}
}
}
else
{
speed_loop = 0;
}
}
else
{
park_enable();
}
}
}
void ioinit (void)
{
DDRD = 0 | _BV(PD7) | _BV(PD6) | _BV(PD5);
ADMUX = 0 | _BV(ADLAR);
ADCSRA = _BV(ADEN);
//ENABLE ADC
}
uint8_t read_adc(uint8_t channel)
{
uint8_t value;
switch (channel)
{
case 0 : ADMUX = 0 | _BV(ADLAR);
break; //ADC0 impedance sensor line
case 1 : ADMUX = _BV(MUX0) | _BV(ADLAR);
break; //ADC1 high
case 2 : ADMUX = _BV(MUX1) | _BV(ADLAR);
break; //ADC2 med
case 3 : ADMUX = _BV(MUX1) | _BV(MUX0) | _BV(ADLAR);
break; //ADC3 low
case 4 : ADMUX = _BV(MUX2) | _BV(ADLAR);
break; //ADC4 IR sensor
default : ADMUX = 0 | _BV(ADLAR);
/* in case where this fails, try ADMUX=(1 << ADLAR)|(0 << MUX3)|(0 <<
MUX2)|(0 << MUX1)|(0 << MUX0); */
}
ADCSRA |= _BV(ADSC); //START CONVERSION
while(!(ADCSRA & _BV(ADIF)));
value = ADCH;
ADCSRA |= _BV(ADIF);
return value;
}
void delay_ms(uint16_t ms)
{
while(ms)
{
_delay_ms(1);
ms--;
}
}
void park_enable(void)
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{
PORTD = 0x00;
delay_ms(200);
}
void intermittent_enable(void)
{
PORTD = 0 | _BV(PD6)| _BV(PD7);
delay_ms(500);
PORTD = 0 | _BV(PD6);
uint8_t count = 10;
while(count > 0)
{
if (read_adc(MED_SENSOR) >= THRESHOLD)
{
medium_enable(); break;
}
else
{
count--;
delay_ms(500);
}
}
}
void low_enable(void)
{
PORTD = 0 | _BV(PD6)| _BV(PD7);
delay_ms(2000);
}
void medium_enable(void)
{
PORTD = _BV(PD5)| _BV(PD6)| _BV(PD7);
delay_ms(2000);
}
void high_enable(void)
{
PORTD = 0 | _BV(PD7);
delay_ms(2000);
}
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29
Appendix B—Project Gantt Chart
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30
Appendix C - Project Hourly Summary; Project Cost Figures
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31
Example of Cost and Price Calculations
Fringe Benefits
25%
of
labor
Overhead
55%
of materials, labor & fringe
Sales & Marketing Expense
25%
of selling price
5%
of selling price
Warranty & Support Expense
Development Cost (Non-recurring Cost)
What it costs the company to develop the product
Parts
$379.75
Labor
$14,700
Fringe Benefits, % of Labor
3,675
Subtotal
18,755
Overhead, % of Matl, Labor & Fringe
10,315
Total
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ECE4007L02: Group 4
$29,070
32
Determination of Selling Price
What the customer pays the company for the finished product
Based on:
10,000
Parts Cost
60
Assembly Labor
10
Testing Labor
10
Total Labor
20
Fringe Benefits, % of Labor
5
Subtotal
85
Overhead, % of Matl, Labor & Fringe
47
Subtotal, Input Costs
132
Sales & Marketing Expense
73
Warranty & Support Expense
15
Amortized Development Costs
3
Subtotal, All Costs
Profit
Selling Price
Total Revenue
Total Profit
MARE Windshield Wiper System
ECE4007L02: Group 4
units
222
70
23.9%
$292
$2,920,000
$697,430
33