lms final report

8/3/2019 LMS Final Report

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Final Design Report Light Measurement

System LEDs Team Brown

Kevin Wilkins

MatE 340/360

Dr. Savage, Dr. London

12/05/2010


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Introduction

This report is a final design review of a light measurement system (LMS) designed to measure the

chromaticity values of Thor Labs Light Emitting Diodes (LEDs).

Application

We will be examining the light produced by LEDs for use in electronic displays and compare the collected

data to light produced by the phosphors in cathode ray tube (CRT) displays. The system will be able to

provide the data necessary to examine if LEDs are a viable replacement for CRT displays. We are

creating a light measurement system that will serve as a mount for three Thor Labs LEDs (Red, Green

and Blue). The LMS must measure the chromaticity values of each LED.

Users Needs

The end user for the LMS needs a prototype produced for proof of concept. It will be made from

aluminum A356 casting and ABS rapid prototyping. This system needs to simultaneously house three

Thor labs LEDs (red green and blue), be stable, easy to use, accurate, precise (0.04 repeatability, 0.10

reproducibility), and must be produced in a timeline of 10 weeks and for under $500 dollars. The system

must be compatible with SMA fittings for 200m fiber optic cables. The sample holder portion of the

system needs to be able to be remotely located from the detection unit (spectrometer), as the LMS

sample holder will potentially be used on the customers manufacturing floor for quality control. The light

detection equipment will likely be in a separate room to keep the sensitive equipment away from debris

and vibrations. The LEDs need to be easily removable so numerous samples can be measured quickly to

ensure a uniform product. The users needs have been organized in a Quality Function Deployment

matrix (QFD), Table I. Weighting factors have been applied to reflect the importance of each requirement

of the system to the user. The needs have been condensed into several categories.


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Table I: QFD matrix displaying the relative importance of each objective

Attributes Measurable Objective Weighting Factor

CostCost to produce


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Conceptual Design Solutions

In the conceptual design stages of development, we took into account that when the LEDs are operated

at the specified power settings from Thor Labs, they produce light at a higher intensity than the

spectrometer can measure. Each of the LEDs produces a different intensity of light at full power. We

created and examined several designs that incorporated different mechanisms to reduce the light

transmission to measurable levels. The first is an aperture controlled output design, incorporating simple

apertures (one for each LED) to get consistent light intensity from each sample, illustrated in Figure 2.

Figure 2: Aperture controlled output conceptual design sketch. This is a side view, demonstrating two

rotating wheels, one for an LED mount and one for aperture selection

This design involves two rotating wheels, one housing the three LEDs and the other with three apertures.

There are a higher number of parts in this design than the following design, which would increase the

expense reducing and ease of use. Having an aperture wheel in this design creates an additional

potential source of attenuation. This system would require that the user precisely position both wheels for

the system to be in proper alignment.

The second design we considered was a resistance controlled output design, Figure 3.


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Figure 3: Resistance controlled output conceptual design sketch. The rotating LED holder shown at leftwould contain resistors in series with the LEDs.

This design has fewer parts and can be made in a smaller footprint than the aperture design. This design

uses only the ABS sample holder, reducing the volume of ABS used. The lens holder assembly can be

moved closer to the LEDs as long as sufficient focal length is maintained. This concept involves using

resistors to equalize the power output of the LEDs to a measurable intensity. The two conceptual designs

are compared in a decision matrix, Table II.

Table II: Decision matrix comparing the two initial conceptual designs for the light measurement system.The numerical values are the averages from all group members

Attributes Weighting Factor Aperture Design Resistor DesignCost 1.75 8 9

Ergonomics 1 7.29 8.57

Manufacturability 0.25 7.43 8.57

Operation 2.5 9.14 9.43

Safety 1 7.29 7.86

Schedule 1.5 8.29 8.57

Stability 2 7.14 8

Total 75.5 85

.


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We determined from the decision matrix that the resistance controlled output design was superior, as it

requires fewer parts and is easier to achieve proper alignment. The design was further refined after

reviewing the detailed design specifications compiled from the performance objectives and the selected

equipment to be used in the LMS.

Design Specifications

The following is a list of equipment that will be used in the LMS. Having detailed design specifications

allows for a detailed design that will fulfill the users needs.

Power Supply

Elenco XP752

0-4 V

0-50 mA

LED sample holder

House 3 Thor Labs LEDs Red LED630E (639 nm center, 17nm FWHM),

Green LED528E (525 nm center, 35nm FWHM), Blue LED465E (465 nm center, 25nm FWHM)

LEDs must be removable

Must be able to be set to one specific position for each led and hold that position

Must hold LEDs in proper lateral and angular alignment (locate at center axis of lens assembly)

Must allow for easy connection of LEDs to power source

uPrint ABS rapid prototype, 0.01 design resolution

Must be smaller that 4x4x4

Base

A356 cast aluminum

ZCast mold

Max dimension: 6x6x4

Max volume of mold: 900 cm

3

Max volume of part and gating: 300 cm

3

Must accept ABS LED holder and Thor Labs lens holder to hold in specified positions


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Lens

0.5 diameterplano convex lens

Thor labs 0.5 lens holder with SMA fitting

Fiber Optics

200m diameter

SMA fitting on each end

About 2-3 feet in length

Detection

Ocean Optics USB4000 spectrometer w/ SMA input, .3 10 nm Resolution

Ocean Optics Spectra Suite software

Spectral AnalysisMicrosoft excel data sheet with chromaticity calculation formulas

Detailed Design Solution

After further refinement of the resistance controlled design, we opted to modify the settings on the

variable power supply rather than using resistors. It achieves the same result of resistance controlled

output, and allows for fewer parts. The design was further condensed, allowing for less material usage.

The power source settings must be modified according to standard operating procedure in order to

control the light being received by the spectrometer. A technician operating the system will be able tofollow the instructions to get repeatable and reproducible results. Having a setting controlled design

allowed us to minimize cost and create a superior, more stable product.

Solidworks Model

From the conceptual design and the detailed design specifications, we produced several part models in

Solidworks. Individual part drawings with dimensions are included in the Appendix A-D. Figure 4 shows

the exploded assembly drawing of the LMS. Figure 5 illustrates the assembled LMS, showing alignment

of the components.


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Figure 4: Exploded assembly drawing, indicating the individual parts of the LMS

Figure 5: Assembled LMS, with section cut illustrating how the components integrate together to createthe system


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There were several features added to the final design to meet the design specifications. The sample

holder is composed of the LED wedge and LED inserts. The wedge shape allows for a reduction in both

ABS and aluminum material from the original circular design. The wedge locates the LEDs in proper

lateral alignment to transmit light along the center of the lens holder assembly. The three individual LEDs

are located the same distance from the axis pin, allowing for the same lateral alignment for each LED

during testing. The LED inserts stabilize the LEDs by sandwiching the LED between both ABS parts

preventing angular misalignment. The inserts are easily removable so a technician could exchange

samples in under a minute as per customer specifications. A dowel pin was incorporated into the design

allowing for consistent positional settings for each LED. The lens holder assembly is located into proper

position by the v shaped groove in the base. The lens holder assembly is held in place by two cable ties

that are inserted through the square holes in the casting. The ties are cinched down onto the lens holder

assembly to prevent misalignment from the moment the fiber optic cable exerts on the lens holder

assembly.

Fabrication and Assembly

The Solidworks model of the base was modified to create a mold for ZCast 501 rapid prototyping. A

pouring cup, sprue and risers were added to the model, allowing for a mold to be modeled. The ZCast

501 powder is the most expensive component and it is important to take account of the volume of powder

used to create the mold. The volume of the mold is 1081 cm3. The volume of A356 aluminum used in the

part including the sprue, pouring cup and risers is 137.20 cm3

with a mass of .370 kilograms. Figure 6

shows the ZCast 501 rapid prototype mold. Figure 7 and Figure 8 show the mold prepared for casting,

and the casting process, respectively.

Figure 6: ZCast 501 rapid prototyped mold. The mold was produced in two sections to allow removal ofcasting sand from the mold cavity to avoid contamination


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Figure 7: ZCast 501 mold prepared for casting. Additional sand with oil based binder is placed around theparting line to avoid spilling of molten A356

Figure 8: Molten A356 is poured into mold until it overflows from risers


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Metallurgical Analysis of Casting

The casting incorporated a pouring cup, sprue and risers, Figure 9. The risers helped to reduce porosity

in the final product, and assisted in achieving a full fill. The risers allowed the part to draw in extra

material during shrinkage that occurred upon cooling. The risers and sprue were removed using basic

machining processes including a band saw and dremel tool. The risers and sprue were kept for

metallurgical analysis.

Figure 9: The casting after removal from the mold. Samples for metallurgical analysis were taken from the

sprue before and after heat treatment.

To produce the base, molten A356 aluminum at 740C was poured into the mold and allowed to solidify

by cooling for several hours. It is important to note that the casting was not equilibrium cooled, which

created thermal stresses in the part. In order to achieve superior mechanical properties (higher hardness

and strength), the part received a T6 heat treatment as per customer specifications. The time and

temperatures for each step of the heat treatment process and contained in Table III. In order to examine

the microstructure of the as cast aluminum, samples were taken from the sprue for hardness testing and

metallography before and after the heat treatment.

Sprue

Pouring

Cup

Risers


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Table III: T6 heat treatment specification for A356.1

Alloy Temper

Type of

casting

Solution heat treatment Aging treatment

Temperature Time, h Temperature Time, h

A356.0 T6 Sand 540 C 12 155 C 3-5

The sample was solutionized for 12 hours, a sufficient period of time to dissolve the silicon solid solution

that was precipitated out of the aluminum solid solution. The magnesium that provides the ability to

precipitation strengthening must also be dissolved into solution and allowed to diffuse into a

homogeneous solid solution. The temperature must be raised to a temperature near but just below the

eutectic temperature for the Al-Si system, and held at temperature for a sufficient period of time to allow

diffusion to occur to create the homogeneous solid solution. The sample must then be quenched to create

a supersaturated solid solution, a prerequisite for precipitation strengthening. The ASTM standards

specify that the sample be quenched in 65C-100C water to prevent thermal stress and quench cracks,

however due to lack of facilities and the fact that the base is a prototype that is not intended for extended

use, the sample was quenched in room temperature water. The base does not require optimal

mechanical properties or durability as testing will extend for only a one week period. Due to the thick

geometry of the part, there was not any significant relaxation from the residual stresses created during

casting that would change dimensions and geometry. A change in geometry would have been of concern,

however the design was robust enough to not exhibit any change. Other groups developing similar

systems have expressed that there were significant changes to geometry as a result of having thin,

unsupported sections and complex geometries. The release of residual stresses during the heat

treatment process had no significant effects on our casting.

Aside from the change in quenching temperature, the T6 heat treatment was performed according to

ASTM specifications, with the aging treatment held for three hours. Both the mold and the pouring

cup/sprue were given the same heat treatment. Additional samples for hardness testing and

metallography were taken from the sprue after completing the heat treatment. One important note is that

the testing conducted on the samples taken from the sprue may exhibit minor differences in

microstructure and hardness, as the sprue and risers were designed to contain the majority of the

porosity from the casting. To avoid using samples with porosity, the samples were taken from the end of

the sprue that meets with the casting. Metallurgical analysis was conducted to determine if the T6

condition was achieved, and to examine the effect of the heat treatment on the microstructure.


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Metallography

To examine the microstructure of the base in as cast and heat treated conditions, the as cast and heat

treated samples from the sprue were mounted in epoxy, ground and polished to 1m. The samples were

examined under an optical microscope and we determined that no etchant was necessary to examine the

important features of the microstructures, Figure 10.

Figure 10: Micrographs of as cast and heat treated A356 aluminum. Samples taken from sprue, mounted

and polished. No etchant used. Micrographs taken at 500x.

From the micrographs, we can see the significant changes between the as cast sample and the heat

treated sample. In the as cast sample, we can see the proeutectic (Al) grains that formed first upon

cooling, and the eutectic (Al) and (Si) between the proeutectic (Al) grains. The eutectic constituents form

a semi-lamellar structure. This is because the sample was allowed to cool faster than equilibrium

conditions. Under equilibrium conditions the sample would have been given sufficient time and energy to

diffuse into a well defined lamellar structure. A356 aluminum should exhibit approximately equal amounts

of proeutectic (Al) and the eutectic constituents, as determined from the Al-Si phase diagram, however

because the sample was not equilibrium cooled, there is a larger amount of proeutectic (Al). The sample

was not given enough time at a high enough temperature to allow the silicon to fully diffuse. We can see

that silicon was precipitated out of the proeutectuc (Al) due to the reducing solubility of silicon in

aluminum with a reduction in temperature. This is exhibited as darker splotches within the light grey (Al)

grains. These silicon precipitates do not strengthen the part. We can see an unidentified silicon

compound that formed as a separate phase. There is not much information available on this compound

from the sources referenced. A method of composition analysis such as Energy Dispersive Spectroscopy

(EDS) would give info into its composition; however this method requires equipment outside the scope of

this project.


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We can see significant changes in the microstructure in the heat treated sample, the most noticeable

being the spherodization of the (Si) solid solution. The solutionizing step of the heat treatment process

gives the sample enough thermal energy to allow the (Si) to diffuse into spheroids which are a lower

energy state, and thus preferred by the alloy. We can see that the spheroids are much larger than the

lamellae, as several lamellae combine to form one spheroid. The precipitation strengthening Mg2Si

precipitates are not visible in optical light microscopy, so we must verify their presence with an alternate

metallurgical method. A transmission electron microscope (TEM) could be utilized to see the effect of the

strain fields produced in the sample by the precipitates; however a TEM was unavailable to this project.

The presence of the precipitates can be verified from hardness testing data.

Hardness Testing

In order to observe the effect of the heat treatment on the mechanical properties, namely hardness and

strength, hardness tests were performed on the as cast and heat treated samples taken from the sprue.

Samples were prepared with parallel faces In accordance with ASTM hardness testing procedurestandards. These samples were not mounted, as the mounting medium would interfere with the hardness

data. Five individual Rockwell hardness tests were performed on each sample; the data was averaged

and is contained in Table IV. The two samples required different scales, as the large difference in

hardness measurements between the two samples is too great to be measured on the same Rockwell

scale. For comparison, the Rockwell hardness data has been converted to the Brinell scale, better

representing the disparity in the data.

Table IV: Averaged hardness data with standard deviations. Rockwell hardness data was converted to

Brinell hardness for easier comparison

As Cast (HRE Scale) Aged T6 (HRB Scale)

Measured Average 55.8 62.38

5.12 3.19

Brinell conversion (500kg) ~ 52 HB ~98 HB

~denotes approximate ( 2 HB)

The standard deviation of the Rockwell data has been included; the max standard deviation is roughly 5%

of the average, indicating that the testing technique produced consistent data. We can compare the

hardness data to data from CES EduPack2

to determine if the T6 condition was satisfied. CES gives an

approximate upper limit for the A356 T6 Hardness range at 107 HV. The Hardness data for the heat


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treated sample can be converted to approximately 111 HV 5 HV which gives an error of approximately

4%. With such a small error, we can determine that the sample reached T6 condition. There are several

possible reasons for the % error in the data. The hardness measurements were converted to Brinell and

Vickers scales using a conversion chart, this provides only an approximation. CES provides a range of

approximations, comparing two approximations will give some error. Also the calibration of the hardness

tester (accuracy) is unknown.

The drastic increase in hardness verified the presence of Mg2Si precipitates. The increase in hardness

indicates in increase in strength. Since strength cannot be measured using the testing methods available

for this project, we can observe an increase in strength from the increase in hardness, as the two

properties are related. Hardness and strength are both a measure of the resistance to dislocation

movement through a sample. An increase in hardness indicates an increased resistance to dislocation

movement, which will also increase strength by approximately the same percentage.

Fabrication and Assembly for Fiber Optics and Lens Components

The fiber optic cables used in the LMS were fabricated from individual 3M components. The fiber is

200m and was installed into the furcation tubing, using epoxy to secure the fiber in the t ubing. The SMA

fittings were also secured using epoxy. After the epoxy set for several days, the protruding fiber was

cleaved off at the surface. The ends were then polished and inspected. An acceptable fiber was produced

to transmit the amount of light required for the system.

The lens components were assembled using two Thor Labs lens holder tubes, a 0.5in plano-convex lens,

SMA fitting and three 0.5in retaining rings. The positioning for the lens was calculated, and further fine

tuned through experimentation. Because the system uses a several components that are sensitive to

positioning, it is necessary for us to conduct a light attenuation analysis on the LMS.

Attenuation Analysis

The power output of each of the three LEDs (Red, Green, and Blue) has been measured in preliminary

testing. The power values were taken using a Thor Labs optical power meter with variable wavelength

settings, allowing accurate measurements of each wavelength that is important for the LMS. The power

values were measured as output from the LEDs alone, through the lens and SMA fitting, and through the

entire system. Testing was done in this manner to isolate each component of the system, all of which may

contribute power loss to the entire system, and we must consider each component individually to

understand where the loss is coming from. Preliminary testing data in contained in Table V


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Table V Testing of red LED to isolate attenuation from the lens holder assembly

Power from

LED

Power through lens

holder assembly

Power through

entire system

Loss from lens

holder assembly

Total loss

2.875 mW 720 W 5.654 W 6.01 dB 27.06 dB

To fully understand light loss in the system, we must examine the attenuation of the fiber optic cable. In

order to accurately measure attenuation from the fiber optic cable, we used the Ocean Optics LS1 power

source. This source produces stable light that can be accurately measured. The light from the power

source was measured using the Thor Labs optical power meter at each of the wavelength specified by

the LEDs. The measurements were not taken directly from the LEDs as it is difficult to isolate light

produced by the LEDs and transmit that light accurately without using a lens setup, introducing other

sources of loss. Taking measurements from the LS1 directly, and through the fiber optic cable allowed us

to achieve more accurate measurements. The difference between the power input and output through the

fiber optic cable are the measurements of concern. The data is organized in Table VI, includingattenuation calculations in decibels (dB).

Table VI Fiber optic cable attenuation at red, green, and blue wavelengths

Wavelength (nm) LS1 Power Output Fiber Optic Power Output Attenuation (dB)

465 2.500 mW 531.7 W 6.72

525 1.865 W 381.4 W 6.89

639 949.0 W 191.9 W 6.94

We can see that with longer wavelengths, attenuation increases; however it is a relatively small amount

that will be insignificant in our testing.

Next, the output of each LED was taken through the entire system to determine the intensity of light being

transmitted to the spectrometer. From this data we can analyze if the power is high enough to get an

acceptable signal to noise ratio. The data taken is organized in Table VII, including photons per second

calculations. The spectrometer requires 8600 photons to make one count and the ideal amount of counts

is 65000, providing a high signal to noise ratio. If there are more than 65000 counts, the spectrometer

becomes oversaturated and will not provide useful data. By the numbers listed above, it will take

5.59 108

photons to get accurate measurements.

Table VII Power readings using the LEDs at manufacturer recommended settings

LED Power (through system) Power (Photons/sec)

Red 8.424 W 2.34 10

Green 529.9 nW 1.47 10

Blue 1.899 W 5.275 1012


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From the data contained in Table III, we can see that there are more than enough photons transmitted to

the spectrometer to produce the data needed to do chromaticity calculations. The integration time must

be set in the range of milliseconds to capture the data without oversaturation.

Analysis

The fiber optic cable had attenuation in the 6-7 dB range for all of the wavelengths we are measuring. In a

preliminary test of attenuation for the entire system, we found that there was a total of about 27 dB of

attenuation; about 6 dB came from the led and lens holder assembly. With about 7 dB from the fiber optic

cable, there is a loss of about 14 dB from the interface between the SMA fitting on the lens holder and the

fiber optic cable. This could be from an incorrect focal distance or lateral or angular misalignment.

Another source of attenuation is from the Plano-convex lens, which causes chromatic aberration. The

focal length is slightly different for each wavelength.

Although there are a number of sources of loss in the system, adequate power is produced for accuratemeasurement of light.

Testing Methodology

Testing the LEDs for chromaticity values will be kept consistent by following standard operating

procedure (SOP). The SOP utilized for this system in contained in the appendix. Through preliminary

testing, we found that the light intensity was drastically different between each LED. The procedure to

allow for consistent testing is outlined in the SOP. There were several sources of misalignment in the

system, sources that could be resolved with a redesign. There was an error in the design for the base

mold, necessitating extensive machining in order to have proper alignment of the lens holder assembly.

The mold was redesigned for precise alignment, however a second casting was outside the budget for

this project. The tolerances between the LED wedge and the LED inserts that were intended to stabilize

the LEDs from angular misalignment were inadequate, requiring the addition of spacers. The alignment

issues could be fixed with proper tolerancing. Following the SOP, repeatability and reproducibility data

was acquired. The repeatability data was taken by testing each LED five times in a one hour period. The

reproducibility data was taken over a five day period, with different operators assembling the system and

testing each of the three led five separate times. All of the captured data was exported into the excel data

sheet referenced in the SOP. The excel data sheet performs chromaticity calculations on the data.


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Results and Color Analysis

The chromaticity data was compiled and analyzed in a repeatability study, Figure ##, and a reproducibility

study, Figure ##. Statistical analysis was used to verify the precision of the system. To determine if the

repeatability and reproducibility meet customer specifications, we examined the two sigma statistic. The

values listed in Figure 11 tell us that with 95% confidence that the true chromaticity coordinate is within 2

standard deviations. This is compared to customer specification and we were able to determine that the

repeatability and reproducibility for all chromaticity data was within customer specifications

Figure 11: Repeatability data (left) and reproducibility data (right)

It is important to note that the red x coordinate 2 in the repeatability study differs by an order of

magnitude from the rest of the data. This is likely due to the fact that the red LED was the first sample

tested, and the power supply may have been given insufficient time to warm up and stabilize. The red

LED also had the highest intensity, requiring a drastic reduction in operating voltage to avoid over

saturating the spectrometer. We determined that the LEDs produce different chromaticity data when

operated at different voltages, and since the RED led required a large change in operating voltage, it also

exhibits the highest error. It would be ideal to devise an alternate method of reducing the intensity of light

transmitted to the spectrometer, such as a neutral density filter. This would allow us to more accurately


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measure the chromaticity values by operating the LED at the Thor LABs specified voltage. The green

LED had a 2 x coordinate that differed from the rest of the data by an order of magnitude as well. This is

likely due to the fact that the green LED was the lowest intensity and required a modification of integration

time to capture usable data. The Green LED was also the loosest fitting of the three LEDs and could have

suffered from a small degree of lateral an angular misalignment, producing variability in the data.

The accuracy of the chromaticity data is more difficult to determine. Thor Labs did not provide

chromaticity specifications for the LEDs, so the data was compared to another group (Team Purple)###

that produced a LMS for the same Thor Labs LEDs. A two sample t-test was performed to compare the

data, the p values for comparison are contained in figure ##. The LEDs were also compared to the

chromaticity coordinates of the CRT standard(##). The chromaticity data and statistical comparison

between both groups and the CRT phosphors are charted in Figure 12.

Figure 12: Two sample t-test data between both LED groups (left) and chromaticity chart (right)

From the two sample t-test, we determined that only the red y coordinate and the blue x coordinate were

statistically similar. This indicates that either the chromaticity value of the LEDs tested by each group


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differed significantly, or that the SOP for each group differed significantly. The source of error could be

determined by testing the LEDs used by the other group in our LMS.

All chromaticity values for the Thor Labs LEDs differed significantly from the CRT phosphors, indicating

that LEDs are not a suitable replacement for CRT phosphors.

Conclusions

From the statistical analysis of the data, we were able to determine that the LMS produced chromaticity

data with precision within customer specifications. The Thor Labs LEDs tested in this system are not a

suitable substitute to match the chromaticity values of CRT phosphors.

Project Plan

To keep track of the tasks that were required in order to ensure completion of the LMS in the allotted

timeframe of 10 weeks, a work breakdown structure (WBS) Gantt chart was utilized to ensure that

sufficient progress was made. The Gantt chart is included in the appendix. This WBS was used to

estimate the time required for all tasks from inception of the project to completion. We were able to

estimate that 180 total man hours were spent on the project. This number could be reduced by allocating

fewer people to each task, as there were members of the group that were observing some of the

fabrication processes for learning experience.

Cost Analysis

With the cost of engineering labor at $100 per hour and 180 man hours spent, we estimated the total cost

of labor at $18,000. This value far exceeds the cost of materials and processing used to create the LMS.

The materials cost breakdown is shown in figure 13. The full bill of materials in included in the appendix.


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Figure 13: Cost of LMS, numbers on pie chart are in US dollars

The total materials cost was $320.67, significantly below the requirement of $500. The cost could be

significantly reduced by a redesign of the Z Cast mold. The volume of the mold was 1080 cm3

which was

above the specified volume of 900 cm3. The mold we utilized was up to two inches in thickness

surrounding the part; however it only needed to surround the features by a minimum thickness of .5 in


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References

1Strengthening by Heat Treatment Heat treatment of Aluminum Alloys, 2002 ASM Handbook,

Robert E Kennedy Library. 3 Dec 2010

2CES EduPack 2010 software, Granta Design Limited. Cambridge, UK. 3 Dec 2010.

3Abbaschian Reza Abbaschian and Robert E Reed-Hill, Physical Metallurgy Principles 4

thed.

Stamford. Congage Learning. 2009.

lms final report

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