Tunable LED Light Source

Sponsor: Electro Optics Laboratory at Michigan State University

Dr. Prem Chahal

ECE 480 TEAM 13

4-29-15

Isaac Davila

John Foxworth

Haosheng Liu

Cynthia Patrick

Ruben Valencia

Dr. Virginia Ayres - Facilitator

   

Table of Contents

Executive Summary ........................................................................................................................3

Acknowledgements .........................................................................................................................3

Chapter 1 – Introduction and background ......................................................................................3

Chapter 2 – Exploring the solution space and selecting a specific approach .................................6

Chapter 3 – Technical description of work performed .................................................................13

Chapter 4 –Test data with proof of functional design ...................................................................24

Chapter 5 – Final cost, schedule, summary and conclusions .........................................................27

Appendix 1 – Technical roles, responsibilities, and work accomplished .....................................29

Appendix 2 – Literature and website references ...........................................................................32

Appendix 3 – Detailed technical attachments ..............................................................................36

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Executive Summary:

Solar cells play an important role in transforming solar energy into electricity through the photovoltaic effect. As such they have become a crucial element in providing clean renewable energy as more consumers turn away from traditional fossil fuels (Bent, ADD FOOT NOTE). The current method of testing solar cells uses a broadband light source and optical grating to change the wavelength of the light to measure the quantum efficiency of solar cells at local spots. The required components for the current method are housed in a system that is costly, cumbersome, and table top in size. Team 13 will create a cheaper, more user friendly testing device composed of LEDs that can be controlled via a laptop computer to provide at least twenty-five peak wavelength points over a spectral range of 400 nm to 1100 nm illuminating a local spot on a solar cell of area 1 mm2 area while the solar cell is monitored using a voltmeter to determine light-conversion efficiency. The device was requested for use in the Michigan State University Electro Optics Laboratory to introduce students to the potential of solar cells as alternative energy sources. In addition, we explored the potential for technology transfer of our basic design concept.

Acknowledgements:

As a team we would like to thank Dr. Prem Chahal for providing us with the concept for this project allowing us to explore tunable LEDs and the vast applications they can be used for in the ever changing needs of the developing society. Dr. Chahal was very clear and straight-forward with what he wanted from us and always made himself available to us during the entire design process. He provided a great resource for bouncing our solution ideas off of and evaluated all of our prototypes and potential designs allowing us to design the best tunable LED light source for his uses in the Michigan State University Electro-Optics Laboratory. We would also like to thank our university facilitator Dr. Virginia Ayres for always making herself available to us whenever we had questions or concerns over the entire duration of our tunable light source development. Dr. Ayres also provided us with excellent and very helpful commentary on most all of our technical communications including this report.

Chapter 1 – Introduction and background:

Dr. Prem Chahal is the current resident Electro-Magnetics professor at Michigan State University and as such he is responsible for the university’s Electro-Optics laboratory. As solar cells become a more and more prominent means of harvesting electricity due to the rapidly increasing desire for society to decrease its dependence on fossil fuels a sufficiently trained Electrical Engineer should have an understanding of a solar cells operation. With this in mind Dr. Chahal has requested a device composed of LEDs that outputs light over the electromagnetic spectrum of 400 nm – 1100 nm to illuminate an area of 1mm2.

A commercially available testing apparatus consists of a halogen light source and optical grating that must be manually adjusted in order to change the reflection of the light in order to produce

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the varying wavelengths. This testing system requires very high power consumption as well as being cumbersome in size and costing in the tens of thousands. Dr. Chahal has requested this device through the senior design course as a flexible less expensive alternative.

As a team when initially presented with what Dr. Chahal wanted we theorized it would be best to use lasers as the light source since as they can be easily manipulated via a microcontroller and provide a powerful beam the emits at a very narrow exact wavelength band. Further investigation demonstrated that all design specifications could be met using readily available LEDs.

LEDs are relatively low cost, require very minimal power, and can easily be manipulated via a microcontroller and pulse width modulation (PWM). The down side of LEDs is that they emit a band of light at a power output that is not ideal for our use. However by calibrating our device to a specific solar cell provided by Dr. Chahal we can adjust the intensity of the light outputted by the LEDs to accurately output the desired power at a certain wavelength. The calibration method was made automatic by being programmed into the microcontroller and will be discussed in Chapter 3.

In order to gain an understanding of solar cell operation Dr. Chahal wants students to be able to control the wavelength of the light outputted by LEDs and their intensity outputted to observe the relationships between these characteristics and the voltage produced by the solar cell. In order to do this we will design our tunable light source to be controlled via a USB connection to a laptop computer that has a guided user interface (GUI) that will allow the user to input a wavelength and intensity.

To directly observe these relationships as they relate to the sun, the power source for solar cells to produce electricity in the real world, Dr. Chahal requires that the tunable light source mimics the spectral content of the sunlight. To do this accurately requires a minimum of twenty-five peak wavelength points along the spectrum whose intensity can be controlled. The dots along the line of figure one represent these twenty-five peak points. The purpose of recreating the spectral content of sunlight is to observe how much voltage that can theoretically be produced by a specific single solar cell while operating in the real world.

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Figure 1

Through the constraints and requirements presented to us by Dr. Chahal we developed a trade-off triangle where our design could only meet two of the three corners, seen in figure 2. This triangle guided us through our design iterations, meeting different corners in different iterations, until we came to a design that met the requirements we could and was approved by Dr. Chahal.

Figure 2

Our final design meets the requirements of being able to automatically cycle through the spectrum of the sun and is small enough in size to portable for testing outside of the lab while being relatively low cost. Two fully functional prototypes have been created and tested. They provide a complete proof of concept for development of a user friendly testing apparatus that demonstrates how a solar cell behaves.

We believe our design will be a successful alternative to the existing halogen lighting system currently available on the market due to its greatly reduced cost, reduced size, greatly reduced

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power consumption, and ease of use. We prove it is possible to manipulate LEDs in such a way to mimic a specific spectrum.

With the success of this manipulation we determined that our general technology can easily be adjusted to a vast number of convenient and beneficial uses. Jaundice is a disease that occurs in sixty percent of newborns and can lead to a variety of adverse health effects ranging from deafness to death. It is caused by a build up of bilirubin in the blood which can easily be changed to a water soluble form that can be expelled through urination known as lunirubin when it is exposed to blue light. Higher concentrations of bilirubin require a higher frequency of blue light and light skinned infants require a higher intensity of light than darker skin due to the amount of light absorbed through the skin that reaches the blood. By adjusting our design to cover the blue light spectrum of 400 nm – 500 nm we can create a low cost, safe (due to the little heat given off compared to current light treatments), low energy consuming device that can be used to easily customize treatments on a per case basis and can be used in low income countries where Jaundice is presenting itself more and more.

The tunable LED technology that we have developed can also be adapted for uses such as: greenhouse lighting, where different ratios of red to blue light are beneficial during different growth stages, headlights on cars for optimal visualization, or even sensing certain gasses. Gasses in the atmosphere can be found by using a photodetector and an LED light source that provides the wavelength at which known maximum absorption of the gas your monitoring for occurs (measuring LED) and a wavelength that is known to not be absorbed by the gas (reference LED). The difference of the signals measured by the photodetector of the when measuring LED is illuminated and the reference LED is illuminated is proportional to the concentration of the gas you are monitoring for. If multiple gasses are being monitored for you can use our technology to change the measuring LED and reference LED and via a feedback loop with the photodetector calculate the concentration of any specific gas you program the array to measure. Using the microcontroller you can program the array to constantly change in order to measure an unlimited number of gasses (cycling through each gas one at a time) or to constantly measure the concentration of one gas for real time monitoring.

In summary team 13 has successfully met all the design requirements for a tunable LED light source for student testing of solar cells, an important alternative energy possibility. For Electrical Engineers, an understanding of solar cells is vital for a well rounded education. Furthermore the design meets specifications that can enable significant technology transfer for use in the treatment of Jaundice and for greenhouse lighting for improved food production.

Chapter 2 – Exploring the solution space and selecting a specific approach:

Through the Function Analysis System Technique (FAST) Diagram shown in Figure 3 displays the approach team thirteen ambitioned to initiate the Tunable Light Source project. In

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order to deliver a final product the delivered the goals of the system, the team determined that the device needed to deliver the spectrum range of the sun to solar cells. However, the device also required generating a specific amount of energy output by transmitting light. In addition, the device an additional requirement was to tune the light by choosing specific wavelength and intensity.

Figure 3: FAST Diagram of Goals and Deliverables

The prototypes that the team created were based upon two key sub-systems: electrical components, and software. The electrical components involve a microcontroller, LCD display, LEDs ranging from electromagnetic spectrum from 400nm to 1100nm, and a battery supply. The software includes the integrated development environment software. The software controls the operation of the microcontroller along with the light emitting diodes (LEDs).

The goal for the first prototype design was to prove the concept for selecting the appropriate light source. After much research and consideration, the team found that the most feasible light source for the device was the light emitting diode (as shown in Figure 4). LEDs are a very efficient source of light relatively to other light sources. In addition, they do not generate a substantial amount of thermal energy that favors the heating constraint of the final encasing. The LEDs will then be used to create an array to mimic the sun. The sun contains the electromagnetic spectrum ranging from 400nm to 1100 nm. The final product of the LED array will be used to test solar cells in the lab, containing 25 different test points.

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Figure 4: FAST Diagram of LED’s

Along with the proof of the LEDs concept, the team came to the decision to use a microcontroller to control the LEDs via pulse width modulation (PWM). Since diodes are binary components (either off or on), changing the intensity they output light can be challenging. Using PWM, one can switch them on and off very quickly and adjust for how long they stay on each cycle. By adjusting the cycle how they turn on and off, the team was able to make the diodes flicker fast enough to make them appear to be on to the human eye. The microcontroller is also capable of being powered up by a 5 V power source and does not consume a remarkable amount of power to function. Additionally, the microcontroller that was used for proof of concept was the Arduino Uno. Through the FAST diagram of the microcontroller in figure 5 it can be observed the reasons the microcontroller was chosen to control the LEDs output.

Figure 5: FAST Diagram of Microcontroller

In the first prototype, an array of four LEDs in parallel to each controlled by the Arduino Uno microcontroller was created. The LEDs used in this prototype are multicolored LEDs, they were used to represent the wavelength conceptually. The microcontroller was then programmed to control the intensity and apparent wavelength of the LEDs via analog by potentiometers and

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digital via switch buttons. However, our first prototype (shown in figure 6) was partially used to prove the concept that the microcontroller was a practical device for the final design.

Figure 6: Prototype 1

The initial prototype was then shown to the sponsor. After evaluating the prototype Dr. Chahal suggested that the final design should included more testing points for accurate results and also an interface where a computer could communicate with the device to output user-friendly and obtain more data points for a more complete design.

The team concluded that it was necessary to create a different prototype to deliver the goals and requirements that the sponsor had delivered to the team. Taking into consideration that there were more testing points needed for the next prototype, the team’s focus was to deliver more test points. The team created a prototype 2 (shown in figure 7) which divided the spectrum range into 5 different sub-units. The 5 sub-units were split depending on which LED array was inserted to the system. The microcontroller recognized which LED array was inserted via binary I/O pins that were encoded to the microcontroller. The main idea behind dividing the range spectrum into different sub-units was to deliver more testing points per LED array in each spectrum sub-unit range.

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Figure 7: Prototype 2

The second prototype is an alternative design that can be used for a tunable light source. However, when the team presented the second prototype to the sponsor it was found that dividing the spectrum range into five different sub-units of LED arrays was inconvenient for the user. This would indicate that every time the user desired to test a spectrum range that the current LED array sub-unit did not contain, they would have to physically interact with the array by swapping the current array by the desired LED array sub-unit and additionally set the values in the microcontroller via digital or analog method. By being able to physically change the LED array, it raised concern for housing, power output, liability, and consistency of accuracy of the product. Therefore increasing the failure of the system and creating the device difficult to use.

During the creation of the second prototype, the first housing design began to be created. The housing accounted for the lenses that were implemented within the device. The lenses functionality in this device was to refract the light to a common point in order for the light output to become a beam-like shape. However, the distances that was found between the lenses for the light source to accomplish the final goal was far too inconvenient and would make the device less portable. The distances between the LED array, lenses, and output were measured to total distance of 45.12 cm (shown in figure 8). As the distance between the lenses increases, the component becomes more robust, less convenient for use, and costly.

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Figure 8: Total distance for light output using lenses

In summation, the team came to the final decision this project in order to make a reliable final design to prove the concept of the device. From figure 2 found in Chapter 1, the discarded requirement of the project in the trade-off triangle was determined to be power. This was so that the device could effectively occupy minimal space and as well as automation of the 25 different LEDs to prove the concept of the 25 different test points.

The final product design consists of a 25 LED array that will be used to represent the suns’ electromagnetic spectrum. Due to the power requirement being discarded, the product’s size minimized and as well as the cost for the unit. In fact, making a more marketable and user-friendly device. The team’s time management was very adequate for the creation of three different prototypes to find an improved final prototype. The Gantt in figure 9 shows the steps that they took in order to achieve the three different prototypes.

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Figure 9: Gantt chart

Throughout the project the team was given a $500.00 budget to use on the new design expenses. The purchases for the creation of all three prototypes are displayed below in Figure 10, a complete table can be found in appendix 3. A good budget strategy was required to enable the team to create a final prototype, given the fact that there were three different prototypes.

Figure 10

Along with the creation of the final prototype, it is important to account the manufacturing cost per unit. The estimated cost per unit was found to be $256.70 and is demonstrated in figure 11. This is about half of the budget that was given for project expenses. The cost was calculated as a single purchase of products and not in bulk. If purchases were to be done in bulk, the unit’s price will decrease by at least a third of its original cost. Thus, creating a feasible unit for manufacturing.

Figure 11: Per unit cost Tunable Light Source

LEDs,  $46.29   Microcontroller,  $11.22  

Display,  $12.79  

Ba@ery,  $23.00  

Housing,  $150.00  

PotenEometers/Digital  

Bu@ons,  $12  

Remaining  Budet,  $244.70  

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Chapter 3 – Technical description of work performed:

Three different designs were fully prototyped to meet the requirements for this project. Each one provided valuable insight as to what could, and could not be achieved given our limited budget and other restraints. These prototypes also gave us the opportunity to get feedback from our sponsor, Dr. Chahal, to decide what needed to be changed.

PROTOTYPE #1:

The Design

Our first prototype was a conglomeration of different approaches to see what worked and what didn’t. It was meant as a means to test multiple designs at the same time to figure out which methods worked best for both hardware and software. It started with the basics, using an Arduino microcontroller to turn on an LED at various intensities. To start, we needed a circuit that would both power an LED, limit the current through the LED, and be able to interface with a microcontroller to control the intensity using pulse width modulation (PMW).

To achieve this, we implemented a LED, a current limiting resistor, and a switching transistor controlled by the Arduino as shown below.

Figure 12

This design worked well, however, due to the limited number of PWM compatible pins on the Arduino Uno, we were only able to operate 6 different LEDs with this configuration. However, the Arduino Uno did have sufficient I/O pins to satisfy simply turning the LEDs on and off. By making a slight modification to the circuit as follows, we were able to use a single PWM signal to drive every LED.

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Figure 13

The next step was to create an input circuit for the Arduino to change which LEDs were on, and how bright they should be. Two methods were explored to do so. The first was a simple push button switch circuit. When the tact switch is pressed, it will charge the input pin to 5 volts. At first the circuit was simply a switch and 1kΩ resistor in parallel with each other. However we quickly discovered that the input would stay high for approximately 40 milliseconds after the button was released. This was caused by the internal capacitance of the microcontroller. When the button was pressed, it charged that capacitor to 5 volts, but when it was released, the current had nowhere to go, and the cap would slowly discharge due to leakage current. To solve this problem, we implemented a 1kΩ pull down resistor. This resistor allows current to flow to ground, “pulling down” the digital signal from high to low when the tact switch is released. 4 of these switches were used, 2 for selecting color, and 2 for increasing and decreasing intensity. We’ll discuses the code in the next section. The schematic is shown below.

Figure 14

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Second, we used a potentiometer as an intensity control knob. The Arduino has several pins that can be used for analog inputs. Their function is to take an input voltage in the range of 0-5V, and convert it to an integer on a scale from 0-255. For example, if my input voltage was 0V, It would output a 0, if it where 5V (or higher), it would output 255, and if it were 2.5, it would output 126. The circuit for achieving this consisted of just a 10k potentiometer acting as a voltage divider, as shown below.

Figure 15

In addition we decided to implement an LCD screen to display for the user the relative intensity, as well as the color/wavelength selected. To do so, we implemented a Hitachi HD44780 driver compatible LCD screen. Fortunately Arduino’s website contained very well written tutorials on how to wire, and program these LCD screens. The below image is taken from their website.

Figure 16

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As you can see in the image above, the LCD requires 6 I/O pins to operate. It also requires a voltage dividing potentiometer circuit identical to the one we used for our analog input to adjust the contrast of the screen. Again, we’ll discuss the coding for this circuit in the next section.

Building the prototype:

To build the first prototype, we started testing each component for functionality on protoboard. It was here that we discovered the need for pull down resistors. Once we were certain each circuit operated correctly, we began soldering the components onto a Breadboard. The first completed prototyped design is shown in Fig. *, consisting of the three components discussed in the previous section:

A.) The LED driver and user input circuits.

B.) The microcontroller.

C.) The LCD screen.

Figure 17

The LED driver and user input circuit’s Layout (A) is crucial for successful operation. It is therefore shown in detail in figure 18, below where:

A. LEDs

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B. Current limiting resistors C. Switching transistors D. Tuning potentiometers E. Tact switches. F. Contrast adjust (for LCD)

Figure 18

Code The code for this design is attached in the appendix. All functions are commented accordingly as to provide the present and future operators with a clear understanding of how it operates. The goal of the code is to achieve.

Feedback Building our first successful prototype early on provided us with an invaluable opportunity to get feedback from our sponsor and improve our design, as well as to discuss our team’s innovations. Designs that we initiated such as the LCD screen to provide user feedback, as well as two different methods of adjusting the output were well received by Dr. Chahal. However, we also learned that he wanted to have control over each LEDs intensity separately. Since the first prototype design only allowed control of which LEDs were active, and set them all to the same intensity, a redesign was needed to provide a higher level of control. Also, since this design was meant to be a small scale model of what could be accomplished, a 0.1W/mm^2 power design goal had not yet been

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explored. The second iteration should find a way to achieve both goals, while maintaining the features that Dr. Chahal praised.

PROTOTYPE #2:

The Design:

The primary focus of our second prototype was to meet the requirements which our first prototype did not. Specifically, the ability to control each LED individually while also outputting at least 0.1W/mm^2 of luminescent power. LEDs are approximately 10% energy efficient. This means that in order to achieve a 0.1W output, we would need a 1W input for our LEDs. Since a typical LEDs power is in the mW range, we would require approximately 60 LEDs per wavelength.

We considered creating a single LED array, with 60+ LEDs per wavelength for a total of 1,500 LEDs, however we soon discovered that the size of such a design would require large, expensive lenses causing it to be too cumbersome for use in a field environment. Instead, we chose a design with interchangeable LED panels, each with 64 LEDs to meet the power requirement.

Figure 19

The panels were to be interchangeable via a CAT-5 connection. In order to change the wavelength, the user would simply insert the panel of the desired wavelength. In order to

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still implement an LCD screen that would display wavelength and intensity, we had to figure out a way to allow the microcontroller to identify which panel was inserted.

Figure 20

It is for this reason we chose CAT-5 cable as our connection method. CAT-5 cable contains 8 pins; this allows us to provide the panel with a voltage source, ground, and a PWM signal using 3 pins, while utilizing the rest as a binary recognition system. With 5 pins, there are 32 unique binary combinations. By controlling which bit is high and low by connecting the desired pins to either VCC or GND, we created a unique binary signature for each panel. The microcontroller reads these using 5 digital inputs and displays the corresponding wavelength on the LCD.

We also included tuning knobs for the intensity setting as described in the previous prototype. However, to make adjusting the value more users friendly, we implemented a second knob for fine tuning. The first potentiometer had the ability to change the intensity from 0-100% while the second be tuned for a for a ±5% adjustment.

The second prototype was also used to test the functionality of lenses. The layout of the circuit was such that there would be room on the board to place lenses and adjust the distances to optimize the condensing of light. A distance of 20cm was left at the output of the LED panel to do so.

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Building the prototype

Figure 21

The first prototype had two significant components. The first was the LED panels, and the second was the circuit that drives them (i.e. microcontroller, transistors, tuning pots, LCD screen). These two components were to communicate with each other via a CAT5 connection.

The LED panels were constructed by creating 16 groups of 4 LEDs. These LEDs were mounted to a breadboard in a very dense configuration to minimize light dispersion. The circuit layout below was a slight modification to the previous prototypes design to allow for multiple LEDs per current limiting resistor. By wiring them as such, we effectively reduced the number of resistors required by a factor of 4.

Figure 22

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The control circuit consisted of the microcontroller, transistors, LCD panel, and tuning knobs. The tuning knobs were connected to the Arduino via analog input pins, allowing the microcontroller to detect their positions. The amount current being drawn from the LED panel was too great for the arduinos on board regulated power supply to support. To protect our microcontroller, a second power source was added to power the LEDs while the Arduino powered the LCD, and Tuning knobs.

Feedback

While this design did successfully meet the power requirement, it did so at the expense of automation. This design would require users to manually switch LED panels to control wavelength. When the second prototype was presented to Dr. Chahal, he pointed out that he desired a fully automated system that could interface with a computer to run automated testing protocols without further user inputs.

Furthermore, through experimentation on the second prototype we concluded that lenses were not a viable solution for condensing the LEDs light. Testing showed that the losses involved in using lenses to focus light, as well as the space they would require to be set at the proper distances, made this design impractical for our application.

PROTOTYPE #3 (Final Design):

Utilizing the feedback from both previous iterations of design, we began designing the final prototype. This design was to have full control over each individual LEDs intensity, be able to interface with a computer, all while being contained in a compact housing for field use.

In order to achieve full control over each LED, we required one switching transistor for each LED. While this method does provide the level of control desired by our sponsor, it requires a microcontroller with at least 25 PWM outputs. For our prototyping, we upgraded our microcontroller to the ArduinoMega2560. This is the most powerful microcontroller available from Arduino catalog and contains 54 general-purpose I/O pins PWM pins. This allows expansion of our design to contain more data points in the future if required.

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Figure 23

Since the final product was also meant to be portable, we implemented a 5-volt internal battery. This battery was selected to be rechargeable, and provide approximately 10 hours of operation per charge. We would also implement a secondary LCD screen that displays the remaining battery life as a percentage for the users convenience.

We decided to continue to implement the tuning knobs and tact switches from the previous designs since they received such positive feedback. The LCD feedback screen was also included to make the design more user friendly.

The graphical user interface (GUI) was created using a third party developed software called ArduLink. By utilizing the functions found within ArduLinks libraries, we were able to quickly create a user friendly GUI with the ability to control each LEDs intensity. In order to control the LEDs, all one needs to do is connect a computer to the tunable light source via a standard USB connection and run the java script.

Figure 24

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Building the prototype

In order to create a fully functional device, as well as an astatically pleasing design, we created a housing for our circuitry, figure 25 is a 3-D model rendering. This housing was to contain all wires and circuit boards, with user inputs such as knobs, buttons and LCD screens mounted on the outside. A circular opening for the light output of the LEDs would also be made. Ports for both the USB input and charging input were created as well.

Figure 25: A User view, B Output view, C side view

B  

C  

A  

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Chapter 4 –Test data with proof of functional design:

Experimental Test Design

The way we tested our devices was by using a small solar cell, pictured below, that was provided to us by our sponsor. We connected the solar cell to a voltmeter then measured the output voltage.

Figure 26

Prototype 1:

For the first prototype, the distance, light intensity and wavelength were varied to see how the output of the solar cell was affected. In the prototype 1, there are 4 LEDs; each one can output seven different colors and the intensity can vary from 0% to 100%. In order to make the tests more accurate we made sheaths to funnel the light and reduce light leakage. To reduce the light leakage we wrapped the sheaths with black tape. Two sheaths were made to measure at different lengths then they were placed between the LED and the solar cell. When the solar cell detects light, the voltage varied based on the light intensity and wavelength. The measurements were taken at 12mm and 97mm away from the LED. Each distance was tested three times at a different intensity; 50%, 75% and 99.61%.

Results of Tests

In addition to the effect intensity has on voltage the wavelength of the light and the distance from the source to the solar cell also affected the output voltage as shown in figure 27a and figure 27b. The solar cell did not generate the same voltage for every wavelength. For light in the UV region the solar cell generated a higher voltage. Then the voltage started dropping after 500nm. At around 510nm the voltage was at its lowest value. We also measured the voltage for white light but did not list it in the graph above since it is composed of many wavelengths. Thus the measurements from prototype 1 indicated that our design worked but it needed improvement.

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Figure 27a: Prototype 1 Data

Figure 27b: Prototype 1 Data

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The results demonstrated that the higher intensity have greater output voltage than at lower intensity. Also the separation distance from the solar cell to the LED was a big factor. More output voltage was measured the closer the solar cell was to the LEDs.

Final product

For the final product, each wavelength was tested individually. Each wavelength was also tested a three different intensities; 50%, 75% and 100%. A sheath similar to the one used in the testing of the first prototype was used to reduce light leakage and funnel the light towards the solar cell.

Figure 28 shows the wavelength versus the output voltage of 25 different LEDs at an intensity of 50%, 75 % and 100%. From the diamond line to the triangle line, it is demonstrated that the output voltage increases with the intensity. But at this time the output voltage of the total 25 LEDs do not have a general trend drop from low wavelength to high wavelength, which is different with the result of prototype 1. This is due to that in prototype 1 we have 4 of the same LEDs, but in final product there are 25 different LEDs, it may cause that happen. To compare the results with prototype 1, a single LED in final product nearly have the same output voltage as the total 4 LEDs in Prototype 1 in 12mm distance. That means we have a great improvement in our final design.

Figure 28: Final Design Data

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Chapter 5 – Final cost, summary and conclusions:

Team 13 developed three prototypes, one of which became our final design. The first prototype was developed to prove that the functionality of our design. This design proved that we could vary the wavelength and the intensity of our light source.

Our second prototype was a modification of our first. In this design we also had an LCD display and a microcontroller. The only difference was that we used arrays of individual colored LEDs. We wanted to create 25 arrays for each wavelength we needed. This design was meant to meet our power requirements but automation would be given up. The user would have needed to insert each array for a specific wavelength. After demonstrating the second prototype for our sponsor, he determined that he did not want to give up automation for power and directed us to implement and optimize a model similar to the 1st prototype We did not test prototype design 2 further.

Both iterations provided valuable sights. We created our final design as an array with 25 LEDs each with a different wavelength ranging from 400 nm to 1100 nm. We successfully were able to achieve manipulation of the LEDs in the array in order to control the intensity and which wavelength was being outputted at that intensity. With this students in the Electro-Optics laboratory will be able to control the device in such way to mimic the spectral content of sunlight in order to test solar cells.

Team 13 understands the importance of a cost effective design to enable widespread use of the Tunable LED Light Source. In order to produce the three functional prototypes used to come to our overall design we implemented out budget as shown in figure 29. A significant portion of our budget was used on the initial prototypes; therefor figure 30 demonstrates the cost would be for a single unit of our final device to be produced, a total of $256.70.

 

Figure 29: Total budget distribution

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Figure 30: Per unit cost

Overall our project was a successful failure. Due to the small area of the solar cell Dr. Chahal wishes to use in the Electro-Optics lab the voltmeter attached to the solar cell would have a reading in the millivolts range, decreasing the accuracy of the measurement. In order to bring up the voltage reading from the solar cell Dr. Chahal theorized that the energy intensity provided by the light source to be 100 W/m2 resulting in a minimum power requirement of 0.1 W to illuminate the 1 mm2 area given to us. Due to the $500 dollar budget constraint we were unable to achieve this power at all twenty-five peak points. However our final design is easily expandable to meet this power requirement by simply adding additional LEDs, wired in parallel to the current LEDs for each peak point, once additional funding can be secured.

After completing this design we believe we have created an excellent prototype that future senior design students can easily expand to meet his power requirement of 0.1 W on a 1mm2 area, the only major failure that occurred was not meeting this minimum power requirement. This is a failure because the purpose of this device is to allow students to accurately measure the voltage outputted by a solar cell of an area of 1 mm2 and the low voltage decreases the reliability of the voltmeters reading. For this reason our device is not yet ready to be used by students for it will not currently give them accurate results and therefore they will not truly be able to understand the functionality of a solar cell.

We believe that Dr. Chahal plans to use our final prototype to secure enough funding to allow the device to meet the 0.1 W power requirement and have students expand on our final prototype in a future semester. Students who work on this in the future will be able to take our final design and will simply have to alter the hardware of the LED array to either have single LEDs at each peak wavelength point powerful enough or wire together, in parallel, enough LEDs at a certain peak point to overall achieve the power requirement at that point. In addition future students should also adjust the calibration since we calibrated our device at an output power less than the 0.1 W.

LEDs,  $46.29   Microcontroller,  $11.22  

Display,  $12.79  

Ba@ery,  $23.00  

Housing,  $150.00  

PotenEometers/Digital  Bu@ons,  

$12  

Remaining  Budet,  $244.70  

29    

Appendix 1 – Technical roles, responsibilities, and work accomplished:

Back (left to right): Isaac Davila, John Foxworth, Haosheng Liu

Front (left to right): Ruben Valencia, Cynthia Patrick

Isaac Davila:

For this project I had several responsibilities. From the beginning I was responsible for the design of the project. Initially much research had to be done to figure out what we were going to make. I had to compare several models that did the same thing ours needed to do. The models that were on the market today came in various forms. From what was found through research we were able to have a general idea of what the final deign would be. During this phase I researched which parts we were going to use for the project. Once I found the right parts to use then I ordered them through the ECE shops website. These parts were then cataloged in a spreadsheet to make sure we stayed under budget. Then John took the parts and ended up developing three prototypes. Once a design had been developed then I was responsible for the testing phase. During the testing phase, I was responsible for gathering data on the prototypes. Haosheng and I used a small solar cell to measure the light output of our prototypes. For all three prototypes we encounter is issue of light leakage. When we tried to measure the light using the solar cell too much was escaping from the sides. So I figured out a simple way to funnel the light and have less from escaping so more could end up being directed at the solar cell. We made a sheath out of paper then coated the outside with a think layer of black tape. This made the measurements significantly greater then before we used the sheath. For the first prototype data was gathered on seven wavelengths that could be output. The second prototype only had one array we were going to test to confirm that we could achieve the requirement power. For the final design data was gathered on 25 different wavelengths. All the data I

30    

gathered was then tabulated and used to create the visual aids for an easy way to see the results.

John Foxworth:

My primary role in our team was designing and prototyping all electrical hardware and software. Having been a circuitry hobbyist for years prior to attending Michigan State University, my vast hands on experience with prototyping and design made me well suited for this role. To do this I had to research and develop different circuitry solutions to our project goals. From the beginning of the design process I had ideas on what to do, but as the designs became more and more intricate, I needed to learn new skills and design techniques to complete our design.

For the first prototype I focused more on what could be accomplished on a small scale. The requirements of the project were not meant to be met with this design. As a designer I like trying things and experimenting via trial and error. Our three iterations of designs let me hone in on the optimal solution given our design restrictions (i.e. Budget, time). Cumulatively I estimate I spent 15 hours soldering, 30 hours researching ideas and finding the proper components to order online, 20 hours designing, both pen and paper and using software analysis, and 30 hours troubleshooting my designs.

Overall I think my role on our team was well fulfilled. Each of our prototypes functioned as intended, which out team takes tremendous pride in. I’ve heard stories of other teams from previous semesters not finishing a functional design, so for our team to create three is quite the accomplishment.

Other than prototyping and designing, I also was in charge of preparing all our teams presentations. Group members would contribute slides and prepare their speeches, and I would compile them together and provide coaching on presentation skills. Our team received perfect scores on all graded presentations, which we again, take great pride in.

Haosheng Liu:

My primary technical role was to test the design product and get the information from the result. In this project the team was able to use the LEDs to achieve the power output of light in a 1 mm2 area. I create the test cover device for prototype 1 and the final design. To lower the cost, he only uses paper and black tape to create it. The test process need to collect as much light as we can, so the rotate the black tape outside can hold all the light stay inside the cover device. Combine the cover device and the solar cell by put the solar cell at the top of the cover device and use black tape to cover the solar cell’s back. I successfully test the prototype 1 and the final design, find the broken part in the final design and get useful information from the results. I was able to write a guide of how to play with the design.

31    

Also, I worked with team member Isaac to collect the results of test and made them into graphs to show the direct conclusion. Before working on the test part, I worked with team member John and Isaac to determine the power supply of the project. By using the detail of the device properties from John, they were able to choose a power supply of maximum output voltage equal to 5 volts and have at least 10000mAh with a pretty low price.

I then came up with the idea of the website, the design we have a light wavelength from 400nm to 1100nm, it can be shown as the rainbow color, I choose the rainbow color LED picture as the background and make each subpage with one of the rainbow colors which have a great echoed around between the project and the website.

Ruben Valencia:

I understood and complied with the project objectives to deliver the requirements of the customer (sponsor); therefore taking the initiative to learn about optics. Through a considerable amount of research, I found that there were ways to focus a direct light source with a wide aperture field. However, I found that the way each LED was positioned, the temperature, and type of LED (spectrum range) affected the outcome that was expected through theoretical calculations. This indicated that each LED would have to use an individual lens to focus to a common point. In fact, this would not only consume time to figure out but also would increment the price of the device tremendously. Hence, I concluded that using LEDs for the amount of funding would be futile. I also assisted the group with the construction of the encasing of the final product. The encasing of the final product consisted with the measurements of all the components that will be in the interior to make sure that they are close-fitting to each other so that the device components limit to being fragile to any agitated movement given that is a portable device. The encasing would also have to account for buttons, warnings other specifications that would require safety standards. In conclusion, I assisted in the majority of the project whether there was small or substantial amount of input. Nevertheless, my main roles were mentioned above. Another important role that I played in the team was communicating with the sponsor on a daily basis. This allowed the team to become informed more frequently of every change that the sponsor may find more adequate for the device, since it will be used for experiments in the laboratory course he teaches. In addition, the sponsor was very helpful in giving a feedback of how the product should function and the way that it should be operated.

Cynthia Patrick:

My largest contribution to the technical aspect of our team’s tunable light source was exploring the potential for technology transfer. I performed in depth research on what causes Jaundice and how tunable blue light can easily be used to quickly, safely, and

32    

efficiently treat infant Jaundice which has rapidly developed to the point of occurring in sixty percent of newborns. In addition I aided in the exploration of uses in green house lighting and headlight use. Due to the non-ideal behaviors of the LEDs in our tunable light source it was required for us to calibrate it to a specific solar cell in order to obtain the most accurate results since the device is to be used for testing. Dr. Chahahl (our sponsor) provided us with the solar cell we were to use and I helped determine how we were going to calibrate. I determined that we simply had to multiply the output, using our microcontroller to modify intensity, by calibration coefficients. The calibration coefficients were determined be comparing the initial (before calibration) efficiency of the LEDs vs. wavelength to the known of the solar cell we were given. In addition to the calibration coefficients I determined it would be optimal to output the light in a way so that it exactly equaled the 1 mm2 area of the solar we were given. As the area of a solar cell changes so does the amount of voltage it is able tor produce; hence if we output light at an area equivalent to that of the solar cell calibrated there is no need to add additional programing to compensate for a changing area. I assisted in finalizing the housing for our tunable LED light source and suggested having external controls on the device so it could be operated without USB connection to a computer. Finally I helped to assemble our circuitry and our housing together to achieve the finished auto-calibrated tunable LED light source.

Appendix 2 – Literature and website references:

• American Educational Products. 6 Piece Glass Lens Set. 2015. http://www.amazon.com/American-Educational-Piece-Glass- Lens/dp/B00657LW8G

• ATMEL. ATTINY44A-PU - IC, 8BIT MCU. 2015. http://www.amazon.com/ATMEL- ATTINY44A-PU-8BIT-20MHZ-14- PDIP/dp/B00AS6FYC0/ref=sr_1_1?ie=UTF8&qid=1430184113&sr=8- 1&keywords=ATMEL+-+ATTINY44A-PU+- +IC%2C+8BIT+MCU%2C+AVR+Tiny%2C+20MHZ#product-description- iframe

• Bent, Stacey F. "Thin-film coating for solar cell applications." Advanced Coatings & Surface Technology Sept. 2013: 9+. Academic OneFile. Web. 3 Feb. 2015. http://go.galegroup.com.proxy2.cl.msu.edu/ps/i.do?id=GALE%7CA3 48998216&v=2.1&u=msu_main&it=r&p=AONE&sw=w&authCount=1

• Digi-Key. IR 950NM LED. 2015. http://www.digikey.com/product- detail/en/LNA2902L/LNA2902L-ND/970650

33    

• Digi-Key. IR 940NM LED . http://www.digikey.com/product-detail/en/SIR- 563ST3FM/511-1365-ND/638560

• Digi-Key. IR 890NM LED. 2015. http://www.digikey.com/product- detail/en/OP297A/365-1063-ND/498689

• Digi-Key. IR 880NM LED. 2015. http://www.digikey.com/product- detail/en/SFH%20485-2/475-1469-ND/1228123

• Digi-Key. IR 875NM LED. 2015. http://www.digikey.com/product-detail/en/HSDL- 4230/516-1262-ND/637526

• Digi-Key. IR 850NM LED. 2015. http://www.digikey.com/product- detail/en/SFH%204550/475-1200-ND/806365

• Digi-Key. IR 810NM LED. 2015. http://www.digikey.com/product-detail/en/MTE2081- OH5/1125-1158-ND/3973506

• Digi-Key. VISIBLE 770NM LED. 2015. http://www.digikey.com/product- detail/en/MTE1077N1-R/1125-1081-ND/3516637

• Digi-Key. VISIBLE 740NM LED. 2015. http://www.digikey.com/product- search/en?pv40=676&FV=fff40008%2Cfff80028&mnonly=0&newproducts=0 &ColumnSort=0&page=1&quantity=0&ptm=0&fid=0&pageSize=500

• Digi-Key. VISIBLE 660NM LED. 2015. http://www.digikey.com/product- detail/en/MTE6066N5-UR/1125-1075-ND/3516654

• Digi-Key. VISIBLE 635NM LED. 2015. http://www.digikey.com/product- search/en?pv40=1&FV=fff40008%2Cfff80028&mnonly=0&newproducts=0&C olumnSort=0&page=1&quantity=0&ptm=0&fid=0&pageSize=500

• Digi-Key. UV 405NM LED. 2015. http://www.digikey.com/product-detail/en/UV5TZ- 405-30/492-1323-ND/2407233

• Digi-Key. UV 400NM LED. 2015. http://www.digikey.com/product-detail/en/UV5TZ- 400-15/492-1813-ND/3095679

• Edmund Optics. Double-Convex Lens. 2015. http://m.edmundoptics.com/optics/optical-lenses/double-convex-dcx- spherical-singlet-lenses/1-14-9mm-experimental-quality-double-convex-dcx- singlet-lenses/43912

• "Getting on Right Wavelength." Telegram & Gazette Nov 03 2013.ProQuest. Web. 3 Feb. 2015.http://search.proquest.com.proxy1.cl.msu.edu/docview/1447992862?p q-origsite=summon

• "How to Choose a MicroController." Instructables.com. Web. 13 Apr. 2015. <http://www.instructables.com/id/How-to-choose-a-MicroController/>.

• "How to Start Programming a Microcontroller?" C. Web. 19 Feb. 2015. <http://stackoverflow.com/questions/78744/how-to-start-programming-a- microcontroller>.

34    

• Intocircuit. 11200mAh 5V 2A/1A Dual USB Ports External Battery Pack. 2015. http://www.amazon.com/Wirecutters-Pick-Intocircuit%C2%AE-Smartphones- Lightning/dp/B00BB5GR0A/ref=sr_1_fkmr0_1?ie=UTF8&qid=1430183862&sr =8-1-fkmr0&keywords=Wirecutter%27s+Pick+- +iClever%C2%AE+Intocircuit+11200mAh+Power+Castle+Smart+LCD+Displa y+Heavy+Duty+5V+2A%2F1

• Mouser. Knobs & Dials NAT .748 DIA KNOB. 2105. http://www.mouser.com/ProductDetail/Apem/420063A1- 4/?qs=sGAEpiMZZMuiwDVLTMm01Qp0CUy%252bGeRMq9XDm0%2FH5jA %3D

• Mouser. Potentiometers 5/8" SQUARE ST PANEL CTRL. 2015. http://www.mouser.com/ProductDetail/Bourns/91A1A-B24- B15L/?qs=sGAEpiMZZMtC25l1F4XBU5x05J6GJgoy98w91Y%2FUtTA%3D

• Mouser. Standard LEDs - 635nm. 2015. http://www.mouser.com/ProductDetail/Lumex/SSL- LX5093LIT/?qs=sGAEpiMZZMtmwHDZQCdlqVsz6Sp3LtaXkRGP1QPuJRI% 3d

• Mouser. Standard LEDs - 630nm. 2015. http://www.mouser.com/ProductDetail/ROHM-Semiconductor/SLI- 580UT3F/?qs=sGAEpiMZZMtmwHDZQCdlqVFlG8iQtBnfODyEmv6kfaM%3d

• Mouser. Standard LEDs - 620nm. 2015. http://www.mouser.com/ProductDetail/ROHM-Semiconductor/SLI- 343URCT32/?qs=sGAEpiMZZMtmwHDZQCdlqVFlG8iQtBnfs1mb41tMh3U% 3d

• Mouser. Standards LEDs - 611nm. 2015. http://www.mouser.com/ProductDetail/ROHM-Semiconductor/SLI- 580DT3F/?qs=sGAEpiMZZMtmwHDZQCdlqVFlG8iQtBnfUEW%2futx63dE%3 d

• Mouser. Standards LEDs - 605nm. 2015. http://www.mouser.com/ProductDetail/ROHM-Semiconductor/SLI- 343D8C3F/?qs=sGAEpiMZZMtmwHDZQCdlqZSyY0MFufDwjB59JCsFYIA%3 d

• Mouser. Standards LEDs - 588nm. 2015. http://www.mouser.com/ProductDetail/Kingbright/WP7113YT/?qs=sGAEpiMZ ZMtmwHDZQCdlqXYfWhYL4D7CTL%252bm3AzLTCc%3d

• Mouser. Standards LEDs - 585nm. 2015. http://www.mouser.com/ProductDetail/Lumex/SSL- LX3054YT/?qs=sGAEpiMZZMtmwHDZQCdlqVsz6Sp3LtaX5bGqF7%252bep PE%3d

35    

• Mouser. Standards LEDs - 569nm. 2015. http://www.mouser.com/ProductDetail/Lite- On/LTL-307GE/?qs=j0%2fFY5JBh%2fewiHGjiob7SQ%3d%3d

• Mouser. Standards LEDs - 560nm. 2015. http://www.mouser.com/ProductDetail/ROHM-Semiconductor/SLI- 343P8C3F/?qs=sGAEpiMZZMtmwHDZQCdlqZSyY0MFufDwkR3apV3ogPE% 3d

• Mouser. Standards LEDs - 525nm. 2015. http://www.mouser.com/ProductDetail/ROHM- Semiconductor/SLA560EC4T3F/?qs=sGAEpiMZZMtmwHDZQCdlqVFlG8iQt BnfgKs7xpxasyg%3d

• Mouser. Standards LEDs - 518nm. 2015. http://www.mouser.com/ProductDetail/ROHM- Semiconductor/SLA580ECT3F/?qs=sGAEpiMZZMtmwHDZQCdlqVFlG8iQtB nf0hUZ%2fl4xFjs%3d

• Mouser. Standards LEDs - 470nm. 2015. http://www.mouser.com/ProductDetail/ROHM- Semiconductor/SLA580BC4T3F/?qs=sGAEpiMZZMtmwHDZQCdlqVFlG8iQt BnfPMxBippZ1PU%3d

• Mouser. Standards LEDs - 468nm. 2015. http://www.mouser.com/ProductDetail/ROHM- Semiconductor/SLA580BCT3F/?qs=sGAEpiMZZMtmwHDZQCdlqVFlG8iQtB nfbr9Blizc%252be0%3d

• Mouser. Standards LEDs - 430nm. 2015. http://www.mouser.com/ProductDetail/Chicago- Miniature/CMD383UBC/?qs=sGAEpiMZZMtmwHDZQCdlqRwkL44XNf95BM G1qmPe4I%3d

• Medicine Net. N.p., 24 Mar. 2014. Web. 2 Apr. 2015. http://www.medicinenet.com/newborn_jaundice_neonatal_jaundice/article.htm

• Mouser. Standard LEDs - 700nm. 2015. http://www.mouser.com/ProductDetail/Lumex/SSL- LX3054HT/?qs=sGAEpiMZZMtmwHDZQCdlqVsz6Sp3LtaXkyettWHwoQY%3 d

• Mouser. Standard LEDs - 660nm. 2015. http://www.mouser.com/ProductDetail/ROHM-Semiconductor/SLA- 360LT3F/?qs=sGAEpiMZZMtmwHDZQCdlqVFlG8iQtBnfWFCAUyi9FJU%3d

• Sakha, Sedigheh Hossein, Manizheh Gharehbaghi, and Mohammad Rahbani. "The Effect of Clofibrate with Phototherapy in Late Pre-Term Newborns with Non-Hemolytic

36    

Jaundice." Indian journal of medical sciences 63.5 (2009): 174-9. ProQuest. Web. 2 Apr. 2015.

• Science First. Lens Double Convex 100mm Dia X 15cm FL. 2015. http://www.amazon.com/Double-Picture-depicts-multiple- individually/dp/B008DWKVYW/ref=sr_1_1?s=industrial&ie=UTF8&qid=14301 84491&sr=1- 1&keywords=Lens+Double+Convex+100mm+Dia+X+15cm+FL%2C+Picture+ depicts

• Thoppil, Dhanya A. "New Light for Infant Jaundice; LED Bulbs Help India Treat Potentially Fatal Disease Better, Save Energy." Wall Street Journal (Online) Nov 20 2012. ProQuest. Web. 3 Feb. 2015. http://search.proquest.com.proxy1.cl.msu. edu/docview/1171058479?pq-origsite=summon

• Thorlabs. Epoxy-Encased LED, 1070 nm. 2015. https://www.thorlabs.com/thorproduct.cfm?partnumber=LED1070E

• "WHAT IS ARDUINO?" Arduino. Web. 15 Mar. 2015. <http://www.arduino.cc/>. • Zonios, George, Julie Bykowski, and Nikiforos Kollias. "Skin Melanin, Hemoglobin, and

Light Scattering Properties can be Quantitatively Assessed In Vivo Using Diffuse Reflectance Spectroscopy." Journal of Investigative Dermatology 117: 1452-57. H <http://www.nature.com/jid/journal/v117/n6/full/5601313a.html>.

Appendix 3 – Detailed technical attachments:

Budget Distribution:

Total LEDs Lens Microcontroller Display Knobs/Dial Potentiometer Battery IC Chip

$500.00 $218.92 $32.03 $0.00 $0.00 $13.32 $25.20 $22.99 $23.52

Housing Shipping cost

Incidental Fund

$60.00 $55.38 $48.64

Total cost per unit:

Components

Description

LEDs Wavelength Price per unit

37    

1070 nm $20.58

950 nm $0.20

940 nm $0.54

890 nm $0.74

880 nm $0.37

875 nm $0.70

850 nm $0.45

810 nm $2.98

770 nm $2.73

740 nm $2.87

700 nm $0.27

660 nm $0.64

660 nm $1.16

635 nm $3.72

635 nm $0.17

630 nm $0.53

620 nm $0.68

38    

611 nm $0.40

605 nm $0.40

588 nm $0.15

585 nm $0.14

569 nm $0.10

560 nm $0.40

525 nm $1.59

518 nm $1.86

470 nm $1.47

468 nm $1.74

430 nm $2.78

405 nm $1.20

400 nm $1.20

Lens Description

125mm Lens Double Convex $2.15

Microcontroller Atmel ATUC256L3U-Z3UR $11.22

Display LUMEX LCD $12.76

39    

Knobs/Dial $3.33

Potentiometer $5.04

Battery

$22.99

IC Chip

$5.88

Housing Materials $150.00

TOTAL $266.13

Table 1

Projected Cost to meet 0.1 power requirement (Per Unit):

Components          

  Description        

LEDs   Wavelength   Price  per  unit   Quantity   Total  

  1070  nm   $20.58   50   $1,029.00  

  950  nm   $0.20   50   $10.00  

  940  nm   $0.54   50   $27.00  

  890  nm   $0.74   50   $37.00  

  880  nm   $0.37   50   $18.50  

  875  nm   $0.70   50   $35.00  

  850  nm   $0.45   50   $22.45  

  810  nm   $2.98   50   $149.00  

40    

  770  nm   $2.73   50   $136.50  

  740  nm   $2.87   50   $143.50  

  700  nm   $0.27   50   $13.50  

  660  nm   $0.64   50   $32.00  

  660  nm   $1.16   50   $58.00  

  635  nm   $3.72   50   $186.00  

  635  nm   $0.17   50   $8.50  

  630  nm   $0.53   50   $26.50  

  620  nm   $0.68   50   $34.00  

  611  nm   $0.40   50   $20.00  

  605  nm   $0.40   50   $20.00  

  588  nm   $0.15   50   $7.50  

  585  nm   $0.14   50   $7.00  

  569  nm   $0.10   50   $5.00  

  560  nm   $0.40   50   $20.00  

  525  nm   $1.59   50   $79.50  

  518  nm   $1.86   50   $93.00  

  470  nm   $1.47   50   $73.50  

  468  nm   $1.74   50   $87.00  

  430  nm   $2.78   50   $139.00  

  405  nm   $1.20   50   $60.00  

41    

  400  nm   $1.20   50   $60.00  

Lens   Description        

  125mm  Lens  Double  Convex   $2.15   3   $6.45  

         

         

Microcontroller   Atmel  ATUC256L3U-­‐Z3UR   $11.22   1   $11.22  

Display   LUMEX  LCD   $12.76   1   $12.76  

Knobs/Dial     $3.33   4   $13.32  

Potentiometer     $5.04   5   $25.20  

Battery     $22.99   3   $68.97  

IC  Chip     $5.88   4   $23.52  

Housing   3-­‐D  print  out   $200.00   1   $200.00  

      Total   $2,999.39  

Table 2  

 Data for Prototype 1:

Prototype I Prototype I

Constant Distanced=12mm, vs changing Intensity

Constant Distance, d=97mm, vs changing Intensity

Intensity=50% Intensity=50%

42    

Color Wavelength

(nm) Vout (mV)

Color Wavelength

(nm) Vout (mV)

Red 800 403.3 Red 800 299.51

Yellow 580 422 Yellow 580 315.4

Green 520 400.1 Green 520 303.5

Cyan 490 439.33 Cyan 490 331.1

Blue 450 430.7 Blue 450 324.5

Violet 420 440.7 Violet 420 330.6

White N/A 443.1 White N/A 334.1

Intensity=75% Intensity=75%

Color Wavelength (nm)

Vout (mV)

Color Wavelength (nm)

Vout (mV)

Red 800 456.1 Red 800 324.3

Yellow 580 482.1 Yellow 580 347.5

Green 520 454.8 Green 520 328.6

Cyan 490 504.1 Cyan 490 368.3

Blue 450 492.7 Blue 450 360.7

Violet 420 505.3 Violet 420 368.2

White N/A 509.6 White N/A 370.8

43    

Intensity=99.61% (MAX) Intensity=99.61%

(MAX)

Color Wavelength (nm)

Vout (mV)

Color Wavelength (nm)

Vout (mV)

Red 800 489.17 Red 800 341.8

Yellow 580 517.7 Yellow 580 362.1

Green 520 485.3 Green 520 340.1

Cyan 490 538.1 Cyan 490 391.7

Blue 450 523.6 Blue 450 382.9

Violet 420 536.5 Violet 420 391.6

White N/A 538.4 White N/A 393.1

Table 3

 

Final Design Data:

Final Product intensity

=50% Final

Product

intensity

=75% Final

Product

intensity

=100%

wavelength Voltage (mV)

wavelength Voltage (mV)

wavelength Voltage (mV)

400 431.47 400 479.33 400 501.98

44    

405 376.62 405 412.27 405 432.84

430 309.31 430 334.56 430 346.12

468 353.57 468 388.36 468 414.38

470 370.21 470 405.14 470 426.06

518 321.54 518 348.39 518 362.91

525 369.39 525 403.08 525 423.97

560 250.91 560 269.43 560 279.55

569 251.06 569 266.13 569 281.09

588 255.87 588 271.63 588 282.25

605 317.02 605 343.22 605 359.57

611 350.33 611 383.22 611 402.89

620 326.07 620 354.44 620 370.22

635 299.49 635 322.19 635 335.86

660 404.71 660 445.53 660 468.37

700 257.33 700 274.35 700 284.57

740 421.58 740 466.82 740 491.21

770 387.5 770 427.23 770 448.71

45    

810 440.98 810 482.99 810 514.25

850 452.39 850 499.3 850 513.08

875 381.62 875 421.54 875 442.82

890 384.32 890 421.68 890 431.53

940 376.44 940 417.26 940 430.17

950 377.22 950 417.56 950 429.19

1070 355.91 1070 394.04 1070 399.93

Table 4

Code

Prototype 1

#include <LiquidCrystal.h> //needed for LCD display

//Pin Numbers on arduino int RED = 2; //Red LED int BLU = 5; //Blue LED int GRE = 4; //Green LED int Pwm = 3; // Pulse Width Modulation Output //Analog Inputs of potentiometers int colorin= A0; int valin = A1; //Inputs of tact switches //Analog inputs are used even though tact switces are binary //to save digital I/O pins for LCD display, final can be changed int Left = A2; int Right = A3; int Up = A5; int Down = A4; //variables used in calculations, initialized to zero when nessisary

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int potcolor=0; int color =0; int potval=0; int tactcolor=0; int tactval=0; int val; int diff; int diffc; int C=0; boolean Tune = false; //am i fine tuning or not? LiquidCrystal lcd(7, 6, 11, 10, 9, 8); //LCD pin configuration void setup() { //set designate pins as outputs/inputs pinMode(RED, OUTPUT); pinMode(BLU, OUTPUT); pinMode(GRE, OUTPUT); lcd.begin(16, 2); // set up the LCD's number of columns and rows: Serial.begin(9600); // set up Serial library at 9600 bps //TEST serial.println("Hello world!"); // prints hello with ending line break } void loop() { if(Tune == false) { //obtain value of Pot and convert it to a value usable by PWM and color assign potcolor=(analogRead(colorin)/128); potval=(analogRead(valin)/4); //obtain position of tact switches, switch to tune mode if pressed if(digitalRead(Right)==HIGH or digitalRead(Left)==HIGH or digitalRead(Up)==HIGH or digitalRead(Down)==HIGH) Tune=true; //start fine tuning with tacts } if(Tune == true) //fine tuning mode, use tact switces { if(analogRead(Right)>500) { tactcolor= tactcolor+1; delay (200); //otherwise button will register as pressed multiple times instead of once }

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if(analogRead(Left)>500) { tactcolor= tactcolor-1; delay (200); } if(analogRead(Up)>500) { tactval=tactval+1; delay(200); } if(analogRead(Down)>500) { tactval=tactval-1; delay(200); } diff=abs(potval-(analogRead(valin)/4.)); diffc=abs(potcolor-(analogRead(colorin)/128)); if(diff>20 or diffc>2) //analog input has been moved significantly { Tune=false; //back to alalog tuning mode //reset values of tact switch modifiers so only analog is used again tactval=0; tactcolor=0; } } //combine values from analog and digital fine tuning inpits color=potcolor+tactcolor; val=potval+tactval; //In case values fall outside accepted range// if(color>7) color=7; if(color < 0) color=0; if(val>255) val=255; if (val<1) val= 1; //Color assignment// if(color==0) { digitalWrite(RED, LOW); digitalWrite(GRE, LOW); //No Color digitalWrite(BLU, LOW); }

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if(color==1) { digitalWrite(RED, HIGH); digitalWrite(GRE, LOW); //RED digitalWrite(BLU, LOW); } if(color==2) { digitalWrite(RED, HIGH); digitalWrite(GRE, HIGH); //YELLOW digitalWrite(BLU, LOW); } if(color==3) { digitalWrite(RED, LOW); digitalWrite(GRE, HIGH); //GREEN digitalWrite(BLU, LOW); } if(color==4) { digitalWrite(RED, LOW); digitalWrite(GRE, HIGH); //CYAN digitalWrite(BLU, HIGH); } if(color==5) { digitalWrite(RED, LOW); digitalWrite(GRE, LOW); //BLUE digitalWrite(BLU, HIGH); } if(color==6) { digitalWrite(RED, HIGH); digitalWrite(GRE, LOW); //PURPLE digitalWrite(BLU, HIGH); } if(color==7) { digitalWrite(RED, HIGH); digitalWrite(GRE, HIGH); //WHITE digitalWrite(BLU, HIGH);

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} //Set PWM value// analogWrite(Pwm, val); // for testing purposes // if(C<1000) // { // C=C + 1; // delay(10); // } // // if(C==100) // { // Serial.print("color= "); // Serial.println(color); // Serial.print("val= "); // Serial.println(val); // C=0; // } //Print readouts to LCD screen for user viewing lcd.setCursor(0, 0); //set cursor to upper left if(color==1) lcd.print("Red 800nm "); if(color==2) lcd.print("Yellow 580nm "); if(color==3) lcd.print("Green 520nm "); if(color==4) lcd.print("Cyan 490nm "); if(color==5) lcd.print("Blue 450nm "); if(color==6) lcd.print("Violet 420nm "); if(color==7) lcd.print("White "); lcd.setCursor(0, 1); //set cursor to lower left lcd.print(val/2.56); lcd.print("% "); // PWM value as a % }

Prototype 2

#include <LiquidCrystal.h> //needed for LCD display

//Pin Declarations int BIT0 = 2; int BIT1 = 3; int BIT2 = 4; int BIT3 = 5; int BIT4 = 7; int Pwm = 6; int TUNE; //= A5

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int FINE; //= A4 int BRIGHT; //= A3 int Val; int C; //bit recognision register int BIT_REG[5] = {0, 0, 0, 0, 0}; //compare registers for each color int NONE[5] = {0, 0, 0, 0, 0}; int RED[5] = {0, 0, 0, 1, 0}; int YELLOW[5] = {1, 1, 0, 0, 0}; int GREEN[5] = {0, 1, 0, 0, 0}; int BLUE[5] = {1, 0, 0, 0, 0}; //LCD pin configuration LiquidCrystal lcd(13, 12, 11, 10, 9, 8); void setup() { //set designate pins as outputs/inputs pinMode(BIT0, INPUT); pinMode(BIT1, INPUT); pinMode(BIT2, INPUT); pinMode(BIT3, INPUT); pinMode(BIT4, INPUT); lcd.begin(16, 2); // set up the LCD's number of columns and rows: Serial.begin(9600); // set up Serial library at 9600 bps //TEST serial.println("Hello world!"); // prints hello with ending line break } void loop() { //Create Array for color regognition BIT_REG[0]=digitalRead(BIT0); BIT_REG[1]=digitalRead(BIT1); BIT_REG[2]=digitalRead(BIT2); BIT_REG[3]=digitalRead(BIT3); BIT_REG[4]=digitalRead(BIT4);

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lcd.setCursor(0, 0); //set cursor to upper left //determin color of insert if ( (BIT_REG[0]==NONE[0]) && (BIT_REG[1]==NONE[1]) && (BIT_REG[2]==NONE[2]) && (BIT_REG[3]==NONE[3]) && (BIT_REG[4]==NONE[4]) ) lcd.print("No insert found "); if ( (BIT_REG[0]==RED[0]) && (BIT_REG[1]==RED[1]) && (BIT_REG[2]==RED[2]) && (BIT_REG[3]==RED[3]) && (BIT_REG[4]==RED[4]) ) lcd.print("Red 800nm "); if ( (BIT_REG[0]==YELLOW[0]) && (BIT_REG[1]==YELLOW[1]) && (BIT_REG[2]==YELLOW[2]) && (BIT_REG[3]==YELLOW[3]) && (BIT_REG[4]==YELLOW[4]) ) lcd.print("Yellow 580nm "); if ( (BIT_REG[0]==GREEN[0]) && (BIT_REG[1]==GREEN[1]) && (BIT_REG[2]==GREEN[2]) && (BIT_REG[3]==GREEN[3]) && (BIT_REG[4]==GREEN[4]) ) lcd.print("Green 520nm "); if ( (BIT_REG[0]==BLUE[0]) && (BIT_REG[1]==BLUE[1]) && (BIT_REG[2]==BLUE[2]) && (BIT_REG[3]==BLUE[3]) && (BIT_REG[4]==BLUE[4]) ) lcd.print("Blue 450nm "); //set brightness level TUNE=(analogRead(A5)/4); FINE=((analogRead(A4)/64)-8); Val=TUNE+FINE; //to fix errors with limits of PWM if(Val<0) Val=0; if(Val>255) Val=255; analogWrite(Pwm, Val); //set PWM value to pin 6 lcd.setCursor(0, 1); //set cursor to lower left if ( (BIT_REG[0]==NONE[0]) && (BIT_REG[1]==NONE[1]) && (BIT_REG[2]==NONE[2]) && (BIT_REG[3]==NONE[3]) && (BIT_REG[4]==NONE[4]) ) lcd.print(" "); else lcd.print(Val/2.56); lcd.print("% "); // PWM value as a % // for testing purposes //if(C<1000) //{ // C=C + 1; // delay(10); //} // //if(C==100)

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//{ //Serial.print("Val= "); //Serial.println(Val); //Serial.print("TUNE= "); //Serial.println(TUNE); //Serial.print("FINE= "); //Serial.println(FINE); //Serial.print("REG= "); //Serial.print(BIT_REG[0]); //Serial.print(", "); //Serial.print(BIT_REG[1]); //Serial.print(", "); //Serial.print(BIT_REG[2]); //Serial.print(", "); //Serial.print(BIT_REG[3]); //Serial.print(", "); //Serial.println(BIT_REG[4]); //C=0; //} }