Optical Tape Measure
May04-30
Design Report
Faculty Advisors: Degang J. Chen
Aleksandar Dogandzic
Team Members: Nick Freese
Bruce Fu
Jason Thompson
Eugene Zimmer
Client: Senior Design
November 23, 2011
Table of Contents
List of Figures ............................................................................................................... iii
List of Tables .................................................................................................................iv
List of Definitions .......................................................................................................... v
Section 1- Introductory Materials ................................................................................ 1
1.1 Abstract ............................................................................................................. 1
1.2 Acknowledgement ............................................................................................. 1
1.3 Problem Statement ........................................................................................... 1
1.4 Operating Environment ..................................................................................... 2
1.5 Intended Users and Uses ................................................................................. 2
1.6 Assumptions ..................................................................................................... 2
1.7 Limitations ......................................................................................................... 2
1.8 Expected End Product and Other Deliverables ................................................. 3
Section 2- End-product Design ................................................................................... 3
2.1 Approach Used ................................................................................................. 3
2.1.1 Design Objectives ...................................................................................... 3
2.1.2 Functional Requirements ........................................................................... 3
2.1.3 Design Constraints .................................................................................... 4
2.1.4 Technical Approach Considerations .......................................................... 4
2.1.5 Technical Approach Results ...................................................................... 6
2.1.6 Testing Approach Considerations .............................................................. 6
2.1.7 Recommendations Regarding Project Continuation or Modification .......... 6
2.2 Detailed Design................................................................................................. 7
2.2.1 Design Overview ........................................................................................ 7
2.2.2 Timer Module ............................................................................................. 8
2.2.3 Transmitter Module .................................................................................. 10
2.2.4 Receiver Module ...................................................................................... 11
2.2.5 Microcontroller with LCD .......................................................................... 13
Section 3- Resources and Schedules ....................................................................... 14
3.1 Resource Requirements ................................................................................. 15
3.1.1 Personnel Time Requirements ................................................................ 15
3.1.2 Other Resource Requirements ................................................................ 16
3.1.3 Financial Requirements ........................................................................... 17
3.2 Schedules ....................................................................................................... 19
3.2.1 Project Schedule ...................................................................................... 19
3.2.2 Deliverables Schedule ............................................................................. 20
Section 4- Closure Materials ..................................................................................... 21
4.1 Project Team Information ................................................................................ 21
4.1.1 Client Information ..................................................................................... 21
4.1.2 Faculty Advisors Information.................................................................... 22
4.1.3 Student Team Information ....................................................................... 22
4.2 Closing Summary............................................................................................ 22
Section 5- References .............................................................................................. 24
Section 6- Appendices .............................................................................................. 25
Appendix A: TDC-GP1 Data Sheet ....................................................................... 25
i
Appendix B: G4176-01 Datasheet ........................................................................ 27
Appendix C: S8334 Datasheet .............................................................................. 29
Appendix D: AD230-T05 ....................................................................................... 31
Appendix E: Optical Tape Measure Testing Form ................................................ 35
ii
List of Figures
Figure 1: Time of Flight Block Diagram .......................................................................... 7
Figure 2: TDC-GP1 ........................................................................................................ 8
Figure 3: Microprocessor TDC-GP1 Interface ................................................................ 9
Figure 4: IXLDO2SI Chip .............................................................................................. 11
Figure 5: First Semester Schedule ............................................................................... 19
Figure 6: Second Semester Schedule .......................................................................... 20
Figure 7: Deliverables Schedule .................................................................................. 21
iii
List of Tables
Table 1: Photodiode Constraints .................................................................................. 13
Table 2: Original Personnel Time Requirements .......................................................... 15
Table 3: Revised Personnel Time Requirements ......................................................... 16
Table 4: Original Other Resource Requirements ......................................................... 16
Table 5: Revised Other Resource Requirements ......................................................... 17
Table 6: Original Financial Resources.......................................................................... 18
Table 7: Revised Financial Resources ......................................................................... 18
iv
List of Definitions
Beam pulse – a short burst of light emitted by a laser.
Class 2 laser – a classification of laser where short exposure is not harmful to
the human eye
GPS mapping – a navigational system using satellite signals to fix the location
of a receiver on or above the earth’s surface.
Incident – falling upon or striking a surface
Interference – confusion of a received signal due to the presence of noise or
signals from two or more transmitters on a single frequency.
I/O – Input/output
Laser – light amplification by stimulated emission of radiation.
LED – a semiconductor diode that converts applied voltage to light and is
used in digital displays.
LCD – Liquid crystal display
Modulated beam – the strength of the laser is rapidly varied to produce a
signal that changes over time.
Optical – of, relating to, or utilizing light especially instead of other forms of
energy.
PIC – Peripheral Interface Controller from Microchip
Range finding – Process of determining the distance to a desired object.
Reflection – The return of light or sound waves from a surface.
TDC – Time to digital converter
Time of flight – the time it takes light to travel from the sensor to the target
and return.
µP – Microprocessor, a controller that is capable of receiving inputs and
producing outputs based on its internal logic.
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Section 1- Introductory Materials
To begin this design report, the problem that the team has been working on over the
course of the semester needs to be defined in detail. Thus, this section will outline what
exactly the problem that the optical tape measure shall solve and what was considered
in the design.
1.1 Abstract
Inexpensive ultrasonic tape measures are available that can only measure
perpendicular distances to fairly large, flat surfaces. Complex environments
make it nearly impossible to determine which surface corresponds to the
measured distance. Determining the distance between any two designated spots
and producing a model of a measured object are impossible with current
ultrasonic tape measures.
The team is designing and implementing an optical tape measure that will
measure the distance to any visible spot within its range. The point to which the
distance is to be measured will be designated by a laser pointer. Designating an
appropriate set of measurements will produce a model of a measured object.
Distances up to 100 feet in length will have an accuracy of ± 0.5%.
1.2 Acknowledgement
There are no acknowledgements at this time in the project.
1.3 Problem Statement
Current ultrasonic tape measures are available that will measure a perpendicular
distance up to fifty feet from the device. Pointing these devices to particular
objects can become impossible in complex environments. A tape measure is
needed that will measure the distance to any visible spot within its range. The
small yet durable device will be able to measure the distance between any two
distinct points and create a model with an appropriate set of measurements.
This mobile device needs to measure distances up to 100 feet in length with
0.5% tolerance.
An optical tape measure will be designed to solve these problems. A laser will
be used to designate the exact point of measurement. The device will run off of
small batteries and be able to fit in the palm of the user’s hand. Several
measurements shall be averaged in the device’s memory to increase the
accuracy of the measurement. The average measured distance from the device
to a designated object will be shown on the digital LED display.
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1.4 Operating Environment
Wide arrays of operating environments exist for tape measures. The device will
be exposed to many possible indoor and outdoor conditions. Precipitation and
temperature changes are present in the countless environments where tape
measures are used. Windy and dusty conditions should not significantly affect
the reliability of the tape measure. The device may also be exposed to physical
abuse such as dropping.
1.5 Intended Users and Uses
Several users currently use tape measures. The intended users include high
school graduates that regularly use tape measures. A slight tutorial is needed to
understand the multiple uses of the optical tape measure. A list of some more
specific users may include construction workers, surveyors, and architects.
The intended uses cover a large variety of applications. Measurements can be
taken from any visible point that sufficiently reflects an incident laser pulse.
Applications may include general measurement, forestry, surveying, utility
mapping, GPS mapping, mining, traffic engineering, accident investigation, ship
docking, recreational sports, and industry.
1.6 Assumptions
The following is a list of assumptions regarding the design of the product:
Users will know how to use a tape measure.
Users will be physically able to use a tape measure.
The object points to be measured are stationary.
The reflecting surface will be sufficiently reflective.
The reflecting surface will be nearly perpendicular to the incident pulse.
Batteries will provide enough power for the device to operate.
All required resources will be available when needed.
All team members will be able to contribute enough time to complete the
project.
Updates shall occur as the process continues.
1.7 Limitations
The following is a list of limitations imposed on the design of the product:
Device must measure up to 100 feet.
Accuracy must be within ± 0.5%.
Dimensions must not exceed 6”x 8” x 3”.
Cost of the prototype must be less than $355.
Device must be easily portable.
Device shall not weigh over 1 lb.
The weather shall not significantly affect the accuracy of the device.
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Updates shall occur as the process continues.
1.8 Expected End Product and Other Deliverables
The following is a description of the expected end product and the list of provided
deliverables:
A small, durable, lightweight optical tape measure. This will be the actual
device that will obtain and calculate the measurements.
A user’s manual. This will describe to the user how to operate the device.
A maintenance manual. This will describe to the user how to properly
care for the device.
Test results. These will be the results from the prototype testing.
Section 2- End-product Design
In order for the team to be successful with this project they will first need to determine
technical, security, intellectual, and safety considerations. The functional requirements
of the end-product will also be outlined in this section. Early identification of risks and
how they will be handled will also ensure a successful project.
2.1 Approach Used
The following sections of the design report will cover the technical constraints
and approaches that the team has considered and chosen for the design of the
optical tape measure. Testing considerations and recommendations for the
project continuation are also included. All of these sections are necessary for the
project to be successful.
2.1.1 Design Objectives
The following list includes the team objectives for the design:
The device shall operate with the simple push of a button.
The device shall measure the distance from the back end of the device to
an object point.
The device shall be easy to aim in order to easily determine the object
point.
The device shall have an accuracy of ± 0.5%.
2.1.2 Functional Requirements
The following list includes the functional requirements specifications:
The device shall measure distances up to 100 feet.
The device shall have an accuracy of ± 0.5%.
The recorded measurements shall be displayed on an LCD screen on the
device.
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The device shall capture the distance from the device to any point within
the measurable distance.
2.1.3 Design Constraints
The constraints list describes the restrictions on the end product design:
The size of the tape measure shall be small enough to fit in the palm of
the user’s hand.
The dimensions shall be 6”x 8” x 3”.
A couple of small batteries need to be able to supply enough power for the
device to operate.
The surface of the object being measured needs to reflect the incoming
laser enough for the device to maintain its accuracy.
The cost of all the components used in the prototype shall not exceed
$355.
The lasers used in the device must be of class 2 to ensure that they are
not harmful to the eye under limited exposure.
The device should be easier to use than a regular tape measure.
The device needs to compensate for possible ambient light interference
and any inclement weather conditions.
2.1.4 Technical Approach Considerations
The technology considerations list describes the available technologies which
were considered for the implementation of the final design.
Pulse-type time of flight systems. In this technology the laser emits very
brief, very intense pulse of light. The instrument measures the amount of
time the pulse takes to reach the target and return, then converts the time
into a distance.
Advantages
Several pulses can be averaged to increase accuracy.
The device would be capable of being self-contained.
Commercial optical tape measures use this method.
Sufficient information is available to aid in design.
The necessary parts for implementation are easier to locate.
Farther distances can be measured.
Disadvantages
An extremely fast timing device is required to time the travel time of a
pulse.
Ambient light interference can be problematic.
The photo detector, the laser driver, and the laser diode are expensive.
Modulated beam systems. The measurement is done by rapidly changing
the strength of the laser to produce a signal. The time delay is calculated
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by comparing the output laser with the delayed signal returning form the
target.
Advantages
No need for an extremely fast timing device.
The lack of fast devices would lessen the cost of some parts.
Disadvantages
Laser must be modulated at a high frequency to obtain an accurate
measurement.
Not as accurate when measuring long distances.
The team was unable to find an accurate enough phase detector.
A feedback loop of the modulated signal would be required for
comparison thus making an additional photo detector necessary.
Laser beam’s intensity vs. visibility. The visibility of a laser beam at some
distance away from the emitter is related to the intensity of the laser beam.
The intensity of the laser can be varied until the laser is no longer visible
on the object. Comparing this value with a set of known values the
distance to the object can be derived.
Advantages
A timing device would not be required.
A phase comparison device would not be required.
The overall design would be less complicated.
The cost of the design would be lessened.
Disadvantages
The desired accuracy would be difficult to obtain.
Controlling the output laser power would be difficult.
The team was unable to locate any parts that would make this design
possible.
Triangulation. Two or more lasers separated by a fixed distance would be
aimed at the object point and the angles of the aimed lasers would be
captured. Trigonometry would then be used to calculate the distance to
the object point.
Advantages
A timing device would not be required.
A phase comparison device would not be required.
No photo detector would be required.
The overall design would be less complicated.
The cost of the design would be lessened.
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Disadvantages
The use of multiple lasers would make a hand-held device impossible.
The accuracy of the measurement would be lessened due to human
error in aiming.
An accurate angle would be difficult to measure.
Setup of the device would be cumbersome.
Multiple measurements would be difficult to obtain quickly.
2.1.5 Technical Approach Results
The final technical approach which was selected was the pulse-type time of flight
system. This approach was chosen because of the high accuracy that can be
obtained at large distances. This approach was also chosen because of the
abundance of information that the team was able to collect on this technology
due to the fact that this is the industry standard for range finding.
2.1.6 Testing Approach Considerations
The prototype shall be tested and debugged to make sure all parts of the system
are being controlled properly. The laser device will initially be tested in low light
environments. The device’s measurements shall be recorded and checked for
accuracy at multiple distances from a known object. Later tests shall be done
under abnormal environmental conditions. These tests shall check the device’s
accuracy under several different weather conditions. Accuracy shall be recorded
for each condition and checked against the accuracy of the ideal test.
The longevity of the device shall be checked by submitting the prototype to
numerous trials. The prototype shall be judged a success if it is still functioning
after 1000 trials.
The results of these tests shall be checked against the accuracy and distance
constraints. If these constraints are met then the design shall be judged as a
success. The team has created a test form in order to capture all aspects of
each test. Appendix E: shows this testing form.
2.1.7 Recommendations Regarding Project Continuation or Modification
Currently, the team feels that it would be best to continue the project as it was
originally intended to be carried with minor changes to certain design constraints.
The first of the constraints to be changed is the computer modeling of a room.
The team feels that the time required to design a software package and
computer interface would constrict the time available for hardware design. The
second constraint to be changed is the limiting of the implementation budget to
$150. The team has found through more in depth research that parts such as
photo detectors, laser drivers, and laser diodes cost more than what was
originally thought. The team proposes that the implementation budget be
increased to $355. This would adequately cover the expenses that are required.
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2.2 Detailed Design
The following sections will outline the design of the optical tape measure in detail.
All of the components that the team is currently looking at using in the design will
be presented along with the details of their operation, operation cost, and
possible sources of each component.
2.2.1 Design Overview
In order to design an accurate optical tape measure using the time of flight
method, the team decided that there are four main modules needed. These
modules are a timer, a laser transmitter, an optical receiver, and a microcontroller
with a liquid crystal display (LCD). Figure 1 below shows a general block
diagram which shows how the modules shall interact with each other.
Button
LCD Microcontroller Transmitter
Start
Timer Receiver
Stop
Figure 1: Time of Flight Block Diagram
The above block diagram of the optical tape measure operation procedure is
further explained below in a step by step listing of the procedures.
Step 1: The user aims the device at the object to be measured.
Step 2: The user presses the activation button signaling the microcontroller to
begin operation.
Step 3: The microcontroller sends a start signal to the timer and a trigger signal
to the transmitter at the same time.
Step 4: The timer begins to count while the transmitter sends a laser pulse at the
object to be measured.
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Step 5: The laser pulse is reflected by the object to be measured and returns to
the device.
Step 6: The receiver detects the returned laser pulse and sends a stop signal to
the timer.
Step 7: The timer stops counting and sends the final measured time to the
microcontroller.
Step 8: The microcontroller takes the measured time of flight and calculates the
corresponding distance based on the speed of light.
Step 9: The microcontroller outputs the calculated distance to the LCD for the
user to view.
2.2.2 Timer Module
A more detailed explanation of what makes up the timer module will now be
discussed. This is the most essential component of the entire design in that it
determines the ultimate accuracy that the device shall have. This accuracy is
particularly difficult because of the fact that the device is required to time a light
beam which is traveling at the extremely high speed of 3 108 m / s meters per
second. At 100 feet the total round trip time of flight for a pulse traveling at the
speed of light would only be
0.3048m 1s
1 ft 3 108 m 203.2ns .
2 100 ft
In order to maintain an accuracy of ± 0.5% at 100 feet, the device needs to
measure the distance to within half a foot or 0.1524 meters of the actual
distance. This distance requires that the time resolution would have to be less
than
0.1524m
508s .
3 108 m / s
With this requirement in mind the team began searching for a semiconductor
timing device. The results of this search produced the TDC-GP1. This device
shown below in Figure 2 is a time to digital converter with a single channel
resolution of 125 picoseconds and a double channel resolution of 250
picoseconds.
Figure 2: TDC-GP1
8
This resolution would easily satisfy the error requirements outlined in the project
plan. It would also cut down on the extra circuitry that would be needed because
of the fact that the device outputs an eight bit digital signal. This makes the
interfacing with the microcontroller a lot easier because the microcontroller
requires a digital input. If the timer output had an analog signal, an analog to
digital converter would have been needed to convert the timer output. With this
device a direct interface is possible. A typical interface of the device with a
microprocessor is shown below in Figure 3. The data terminals in the picture are
the outputs from the timer containing the measured time of flight. For a more
detailed explanation of all of the terminal pins please refer to Appendix A for the
TDC-GP1 data sheet.
Figure 3: Microprocessor TDC-GP1 Interface
The next constraint that the device needed to meet was the fact that the entire
design needs to operate off of commercial batteries. The TDC-GP1 also meets
this constraint in that a 2.7 volt to a 5 volt supply is needed to power the device.
This voltage is low enough that a 9 volt battery would supply the necessary
voltage.
The timer module is also what determines the minimum and maximum distances
that can be measured. The memory registers in the TDC-GP1 can only store so
much information before it runs out of space and a certain initial amount of time
is needed before the first stop pulse can be read. Specifically, the TDC GP1 has
a minimum time interval of 3 nanoseconds and a maximum time interval of 7.6
microseconds. The minimum time interval equates to
9
3 108 m / s
3 10 9 s
.45 meters.
2
The maximum time interval equates to
3 108 m / s
7.6 10 6 s
1140 meters.
2
Please note that the division of two is due to the fact that a light pulse will have to
travel the distance from the object twice (there and back) during the measured
time interval.
These metric units converted to feet are 1.476 feet and 3,740.16 feet
respectively. This means that the minimum distance that the team’s design can
measure shall be 1.5 feet and a maximum of 100 feet is, also, easily within the
devices capabilities.
For a more detailed explanation of the TDC-GP1’s capabilities including multiple
stop pins and ALU capabilities, please refer to the data sheet in Appendix A: .
2.2.3 Transmitter Module
The transmitter module includes a laser diode along with a laser driver to pulse
the laser. In choosing the laser diode driver numerous guidelines had to be
followed. The cost, performance, voltage specifications, and size were of the
most eminent concerns. Models from an array of different companies were
analyzed with the above mentioned parameters in mind.
The driver needed to be capable of generating a pulse that had a width in the
nanosecond range and possess extremely sharp and fast rise and fall times.
These rise and fall times need to be in the picoseconds range because of the
undesirable time that would be added to the timers count from the delay in the
rise of the pulse. This error, however, would be systematic and the team feels
that it should be able to compensate for it in the microcontroller.
A second concern was voltage. The driver needed to be low voltage in order to
enable the battery operation and small size of the tape measure. The voltage
range needs to stay within a few volts up to about 10 volts.
These vague constraints proved to be very limiting and the IXLDO2SI was the
one chip that best satisfied the initial constraints. A more detailed look of the chip
is now given.
IXLDO2SI Features:
Less than 1.5nsec minimum pulse width
10
600 ps rise and fall times
5.5V max supply voltage
10 mA max output current
The IXLDO2SI pictured below in Figure 4 can be purchased alone or with
accompanying circuitry making the addition of the laser diode and the supply
voltage the only necessary additions.
Figure 4: IXLDO2SI Chip
The search for a laser that will be compatible with this driver is still under way.
The laser that the driver company suggests and sells is not an affordable option.
The group is looking for a similar laser from an alternative company that will
possess the characteristics needed. The biggest obstacle to overcome is the
speed of the pulse. The laser diode shall withstand very short bursts of energy
from the laser diode driver. The laser diode will also need to emit light in the
wavelength range of 700-900 nanometers, in order to match that of the design
photodiode detector.
2.2.4 Receiver Module
The laser diode shall have a spectral wavelength of 700nm - 900nm. It travels a
maximum of 100ft from the device to the object. The photo-detector will detect
the laser’s short pulse signal in the range of the spectral response. The device
receives the pulse signal and will immediately output a signal to stop the timer.
The amplitude of the output signal is based on the received light intensity and
wavelengths. The stop signal will not be sent until the detector receives a light
intensity above its threshold.
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To achieve the function of the photo-detector for the system, three photodiodes
have been chosen based on the four constraints listed in Table 1. A discussion
for each constraint has been provided in the paragraphs below. The final
selection will be made based on these constraints.
Rise time/ Response time
Based on the nature of light, laser beams travel at an approximate rate of
9.84 10 8 ft / sec . The problem statement requires the device to measure
distances up to 100 feet in length with a 0.5% tolerance. The device must
achieve a minimum accuracy of 0.5 feet so the instrumental delay must not
exceed
0.5 ft
9.84 108 ft / s 508 ps
if the triggering point is set to half of the rise time. Thus, the maximum rise time
of the output signal needs to be less than
508 ps 2 1.016ns .
If the rise time exceeds this limit, the delay in sending a stop signal to the timer
may be too large to maintain the desired accuracy.
Also, a longer rise time will add undesirable counts to the TDC time due to the
fact that the TDC will not turn off until the stop signal is sent by the photo
detector. The team has determined that this error is systematic. This systematic
error can then be compensated for in the microcontroller.
Spectral response range
The photodiode shall respond to light intensity and a range of light wavelengths.
A narrow spectral response range should be chosen and it must contain the 850
nanometers wavelength of the laser signal. This narrow range can filter out the
ambient light and as a result decrease the noise level.
Peak response wavelength
The peak response wavelength should be chosen close to 850 nanometers to
correspond to the laser’s wavelength. This constraint enables the device to
respond the best to the laser’s light rather than with the interfering light
wavelengths.
Price
Due to the nature of this project, the team has set a goal to keep the photodiode
price below $150. This goal was created to keep the total cost of the project to a
minimum as the photodiode is the most expensive component.
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Table 1: Photodiode Constraints
Part Rise Spectral Peak Price Supplier
Number Time Response Response
Range Wavelength
G4176-01 0.05 ns 450nm-870nm 850nm $161 Hamamatsu
Corporation USA
S8334 1 ns 400nm-900nm 840nm $90 Hamamatsu
Corporation USA
AD230- 0.55ns 320nm-1080nm 700nm $64 Pacific Sensor
TO5
2.2.5 Microcontroller with LCD
The microcontroller is what makes each module function together in displaying a
distance on the LCD. The tasks of the microcontroller start when the user
initiates a measurement by pressing the button. The microcontroller then
initiates the transmitter and starts the timer at the same time. The microcontroller
then waits for the digital output from the TDC. Upon receiving the time in
seconds from the TDC, the microcontroller converts the time to a distance in feet
using this simple distance equation
1 ft
time s 3 10 8 m / s ft .
0.3048 m
Before selecting a programmable microcontroller, the basic needs of the
microcontroller needed to be determined. The team’s microcontroller needs
input/output (I/O) pins to communicate with the other devices. One input pin from
the measurement button will be needed to start the program. One output pin is
needed to simultaneously start the timer and the transmitter. Eight input pins
are needed to receive the digital time measurement from the TDC. The
microcontroller will need 8-10 output pins to control the LCD. The microcontroller
will need to have enough memory to store a program and a few measurements.
After knowing the basic needs of the microcontroller, the process of selecting a
microcontroller began. Both Motorola and peripheral interface controller (PIC)
microcontrollers were researched online. Both of these chips provided the needs
of the optical tape measure. Interfacing with these chips include different
programmers to burn the program onto the chip. The senior design lab provides
a parallel port PIC Programmer to program the PICMicro. With the availability of
this programmer, a PIC chip was the way to go.
There are several PICMicro chips available from www.microchip.com. Most of
these chips cost well under $10. The group decided on the PIC16F873A chip
because of the availability of a header file for the PIC16F87 family. This
particular chip includes 22 I/O pins. This amount should be enough to control the
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other modules in the optical tape measure design. The PIC16F873A cost is
currently at $3.98. There is a vast amount of PIC information and code available
online.
The program of the optical tape measure is being created with the accuracy of
the distance measurement in mind. Several measurements are going to be
taken when the user presses the button. These measurements are going to be
averaged in the registers of the PICMicro before displaying the distance in feet
on the LCD. Systematic error shall also be addressed in the program to adjust
for timing issues in the rise and fall time of the devices. This constant adjustment
shall be determined after several tests have been run. The team has developed
pseudo code for the optical tape measure.
1. Program starts with user press of the button.
2. Initialize the register settings.
a. count = 0
b. sum = 0
3. While count < 1000
4. Start the timer and the transmitter
5. Add TDC output to sum
a. sum = sum + TDCout
6. Increase count
a. count = count + 1
7. End loop
sum 1 ft
8. Send count sytematic _ error 3 10 m / s 0.3048m to the LCD.
8
The PIC microcontroller is the brain of the optical tape measure. It ties all the
modules together to create a working product. The program must work
flawlessly and provide great accuracy. This is the final attempt at accuracy
before providing the distance measurement to the user.
Section 3- Resources and Schedules
The next section of this report will cover the resources and schedules of the project.
Planning the schedule for the year, as well as, planning the resources that will be
required is necessary for the team to be successful in its objectives. A comparison will
be made from the original resources and schedules in the project plan and the revised
resources and schedules based on the work performed thus far on the project to see
how well the project was originally planned and to better prepare the group for future
work.
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3.1 Resource Requirements
These three sections contain information regarding the required resources for the
project. There are three types of resources listed below; personnel
requirements, other resource requirements, and financial requirements. Each
section contains the original estimate and then an updated estimated based on
the work done so far. A description is then added afterward to explain the
differences between the two values.
3.1.1 Personnel Time Requirements
The following two tables list the original estimate of the time required by the team
to complete the tasks necessary for the project in Table 2 and in Table 3 the
actual amount of time which was needed or that will be needed based on the
team’s progress thus far.
Table 2: Original Personnel Time Requirements
Original Personnel Time Requirements
Name Definition/ Product Prototype Product Documentation Total
Research Design Implementing Testing
Nick
Freese 22 35 20 18 12 107
Jason
Thompson 16 34 21 21 13 105
Bruce
Fu 23 37 17 16 10 103
Eugene
Zimmer 19 35 18 20 10 102
Totals 80 141 76 75 45 417
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Table 3: Revised Personnel Time Requirements
Revised Personnel Time Requirements
Name Definition/ Product Prototype Product Documentation Total
Research Design Implementing Testing
Nick
Freese 24 30 20 18 12 104
Jason
Thompson 22 27 21 21 13 104
Bruce
Fu 21 29 17 16 10 93
Eugene
Zimmer 18 26 18 20 10 92
Totals 84 112 76 75 45 393
Comparing these two tables reveals that the team required a little bit more time
defining and researching the problem and quite a bit less time designing the
product than what was originally planned. These two differences are due to the
fact that the team did a lot more research on what could be done and how to do it
during the research and definition phase. This additional research made it easier
for the team to decide upon the parts necessary for the design and where to find
them than what was previously expected.
3.1.2 Other Resource Requirements
The following two tables list the originally predicted other resource requirements
in Table 4 followed by the updated resource requirements based on the current
status of the project in Table 5.
Table 4: Original Other Resource Requirements
Original Other Resource Requirements
Item Team Hours Other Hours Cost
Project Poster 10 0 $50.00
Document Printing 10 0 Donated
Design 72 Unavailable $150.00
Implementation
Computer Software 30 0 Donated
Totals 122 Unavailable $200.00
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Table 5: Revised Other Resource Requirements
Revised Other Resource Requirements
Item Team Hours Other Hours Cost
Poster printing 0 3 $40.00
Laminating and cut 2 2 $21.00
Foam board 1 0 $4.00
Project plan binding 1 1 $4.00
Document printing 5 0 Donated
Microcontroller 10 0 $20.00
Pulsed laser diode 5 0 $60.00
Laser driver 10 0 $70.00
Time to digital 3 0 $39.00
converter (TDC)
Photo detector 20 0 $150.00
Liquid crystal display 5 0 $15.00
(LCD)
Miscellaneous circuit 5 0 Donated
components
Computer software 10 0 Donated
Totals 77 6 $423.00
Comparing these two tables reveals that the number of team hours expected to
be taken up by the other resource requirements has gone down significantly
while the estimated cost for the other resource requirements has gone up. The
difference in hours is due to both the fact that the poster didn’t take as long as
expected and because the amount of research that the team has done so far has
enabled the team to spend less time trying to figure out how each component
works. The cost has gone up because the team failed to realize the cost and
specifications required in both the laser driver and the photo detector. A very fast
rise time is required by both the laser driver and the photo detector to ensure that
the laser pulse is a sharp edge and that the stop signal sent to the TDC is fast to
maintain the desired accuracy. The overall cost of the poster went up around ten
dollars because the team decided to laminate the poster in order for it to look
more attractive. The team had not originally intended to do this.
3.1.3 Financial Requirements
The following two tables present the originally predicted financial resources in
Table 6 and then the revised financial resources based on the current status of
the project in Table 7.
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Table 6: Original Financial Resources
Original Financial Resources
Item Without Labor With Labor
Project Poster $50.00 $50.00
Document Printing Donated Donated
Design Implementation $150.00 $150.00
Labor at $10.50 per hour
Freese, Nick $1123.50
Zimmer, Eugene $1071.00
Thompson, Jason $1102.50
Fu, Bruce $1081.50
Subtotal $4378.50
Total $200.00 $4578.50
Table 7: Revised Financial Resources
Revised Financial Resources
Item Without Labor With Labor
Poster printing $40.00 $40.00
Laminating and cut $21.00 $21.00
Foam board $4.00 $4.00
Project plan binding $4.00 $4.00
Document printing Donated Donated
Microcontroller $20.00 $20.00
Liquid crystal display $15.00 $15.00
Pulsed laser diode $60.00 $60.00
Laser driver $70.00 $70.00
Time to digital converter $39.00 $39.00
Photo detector $150.00 $150.00
Misc. circuit components Donated Donated
Labor at $10.50 per hour
Freese, Nick $1092.00
Zimmer, Eugene $966.00
Thompson, Jason $1092.00
Fu, Bruce $967.50
Subtotal $4117.50
Total $408.00 $4525.50
Comparing these two charts shows that the price without labor has gone up while
the price including labor has gone down. The reasons for the price without labor
going up were discussed in the previous section. The cost of the laser driver and
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the photo detector were unexpectedly high and the cost of lamination was added
to the poster in order to improve its overall appearance. The price with labor
went down due to the fact that the team expects to spend fewer hours on the
project because of the detailed research that has been performed up to this
point.
3.2 Schedules
Due to the complexity of the design process it is essential that the team outline
its projected schedule well before the main bulk of the work is to be done. This
way the group will have a complete understanding of everything that needs to be
done and thus does not procrastinate and end up with an incomplete project.
3.2.1 Project Schedule
The schedule presented in Figure 5 contains both the original schedule from the
project plan and then the actual schedule that was performed for the first
semester. The blue bars are the originally planned scheduled tasks and the red
bars underneath are the actual work done on each task so far. The second
semester schedule is presented below the first in Figure 6. Please note that the
second semester schedule is, as of right now, unchanged from the project plan
so the team decided to omit the red revised schedule underneath the original
tasks.
Figure 5: First Semester Schedule
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Figure 6: Second Semester Schedule
Comparing the original schedule and the updated one show that the team is
currently slightly ahead of schedule as far as the project definition, research, and
designing are concerned. The updated schedule also shows that the team has
been a little behind in the writing of this report and the creation of the poster.
This delay is due to the fact that the team has run into outside obligations for
other classes and hasn’t had time to begin these documents any earlier. The
team has left the second semester schedule as it was originally planned. This is
because the team feels that they will have everything prepared by the beginning
of next semester to proceed as planned.
3.2.2 Deliverables Schedule
The team has to be aware of when the deliverables for the project are due. For
this purpose a deliverable schedule was created. Figure 7 below shows the
deliverables schedule as it was originally planned in the blue bars and then
underneath each original task is a red bar representing the revised deliverable
schedule. Please not that the second semester deliverables are as of right now
will remain the same. For this reason the team has omitted the revised red bars
underneath the second semester deliverables.
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Figure 7: Deliverables Schedule
Section 4- Closure Materials
This section will summarize everything that was contained in this project plan along with
all contact information for the faculty advisors and the team members.
4.1 Project Team Information
Listed below is the contact information that may be needed during the project.
The first subsection contains the data for the project client, the second
subsection contains the data for the two faculty advisors, and the third subsection
contains the data for the student team members.
4.1.1 Client Information
The client for this project will be the Iowa State University Senior Design
program. The two contacts listed below are the individuals in charge of this
program.
Professor John W. Lamont
324 Town Engineering
Ames, IA 50011
Phone Number: (515) 294-3600
Fax Number: (515) 294-6760
Email Address: jwlamont@iastate.edu
Professor Ralph E. Patterson, III
326 Town Engineering
Ames, IA 50011
Phone Number: (515) 294-2428
Fax Number: (515) 294-6760
Email Address: repiii@iastate.edu
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4.1.2 Faculty Advisors Information
Degang Chen
329 Durham
Ames, IA 50011
Phone Number: (515) 294-6277
Fax Number: (515) 294-8432
Email Address: djchen@iastate.edu
Aleksandar Dogandzic
3119 Coover
Ames, IA 50011
Phone Number: (515) 294-0500
Fax Number: (515) 294-8432
Email Address: ald@iastate.edu
4.1.3 Student Team Information
Jason Thompson
905 Dickinson #112
Ames, IA 50014
Phone Number: (515) 292-0195
Email Address: tommyt@iastate.edu
Eugene Zimmer
2300 Mortenson Parkway #14
Ames, IA 50010
Phone Number: (515) 460-5779
Email Address: zimmerec@iastate.edu
Bruce Fu
4529 Webster ST
Ames, IA 50014
Phone Number: (515) 441-0620
Email Address: largeyam@iastate.edu
Nick Freese
1007 Lincoln Way #6
Ames, IA 50010
Phone Number: (319) 929-1300
Email Address: nfreese@iastate.edu
4.2 Closing Summary
As the world advances and technologies become smaller and faster the old way
of accomplishing simple tasks has become obsolete. Not that long ago everyone
used the regular tape measure to which everyone is all accustomed. Now,
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however, there are several more options available to someone wanting to make
a measurement. Ultrasonic devices have been created that have enabled a user
to simply push a button to obtain a distance measurement to a desired object,
but even these devices have their drawbacks. Ultrasonic tape measures are
difficult to aim and are only accurate up to 50 feet. Thus this project will attempt
to amend these difficulties by creating an optical device capable of measure
distances up to 100 feet with the same type of accuracy that the ultrasonic
devices have at 50 feet. The creation of an optical tape measure will also allow
for the designation of the aiming point, thus making this measurement option a
lot faster and a more reliable way of obtaining measurements.
23
Section 5- References
Common optical sensing techniques for displacement sensors, Acuity Laser
Measurement. 2003, http://www.acuityresearch.com/products/lasers-methods.shtml
DEI/IXYS Integrated Circuits. http://www.directedenergy.com/Products/ics.htm
Electro-Optic Devices, Inc. http://www.eodevices.com
How a laser rangefinder works, Laser Technology Inc.
http://www.lasertech.com/pulselaser.html
How lasers work, HowStuffWorks.inc,
http://science.howstuffworks.com/laser.htm
Laseroptronix and our electro optical products and measuring systems. Laseroptronix
http://www.laseroptronix.se
Merriam Webster Online. http://www.m-w.com/home.htm
Microchip. http://www.microchip.com/1010/index.htm
Pacific Silicon Sensor Inc. http://www.pacific-sensor.com
Pic Microcontroller Projects. http://www.rentron.com/pic.htm
Senior Design Homepage. http://seniord.ee.iastate.edu/
Standard Classifications for Lasers, University of Kansas Academic Computing
Services, http://www.epanorama.net/documents/lights/laserclass.html
The Optical Tape Measure by American Visionwear. American Visionwear, LLC.
http://www.opticaltapemeasure.com
Transducers LLC Direct. http://www.transducersdirect.com/
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Section 6- Appendices
Appendix A: TDC-GP1 Data Sheet
25
26
Appendix B: G4176-01 Datasheet
27
28
Appendix C: S8334 Datasheet
29
30
Appendix D: AD230-T05
31
32
33
34
Appendix E: Optical Tape Measure Testing Form
Optical Tape Measure Testing Form
Who:
Date and Time:
Where:
Testing purpose:
Reference angle: 0 15 30 45 60 75 90
Surface type:
Ambient light intensity:
Trial # Device Distance (ft) Actual Measured Distance % Error (actual-
(ft) device)/actual
1
2
3
4
5
6
7
8
9
10
Testing notes:
35