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University of Portland School of Engineering Phone 503 943 73145000 N. Willamette Blvd. Fax 503 943 7316Portland, OR 97203-5798

Design

Project POV globe: Persistence of Vision LED Display

EE 480: Senior Design Fall 2013Team Klickitat

Team Members:

Rose Harber (Fall Team Lead)

Chris Scott (Spring Team Lead)

Michael Burton

Maldeep Kang

Industry Representative:

Zubin Bagai

Faculty Advisor:

Dr. Peter Osterberg

Clients:

Sam & Emily Leach

Table of Contents

Design Document Rev. 1.0 Team Klickitat

Introduction......................................................................................................................................4Design..............................................................................................................................................5

Architecture..................................................................................................................................5Operating Modes...........................................................................................................................5Primary Simulation Mode.............................................................................................................50-15 V DC Power Supply..............................................................................................................6Hall Effect Sensor.........................................................................................................................6Analog DC Motor.........................................................................................................................7Microcontroller.............................................................................................................................7MOSIS Integrated Circuit (IC)......................................................................................................7Current Drivers.............................................................................................................................7LED Ring.....................................................................................................................................7Software Component.....................................................................................................................8Display Mode...............................................................................................................................8Pseudo-Code.................................................................................................................................9User Interface Component.............................................................................................................9MOSIS CHIP..............................................................................................................................10Timing Diagrams........................................................................................................................13MOSIS Chip Layout...................................................................................................................14Macro Model (MOSIS Chip Backup)..........................................................................................15

Mechanical Component...................................................................................................................15The Motor Base...........................................................................................................................15LED Ring...................................................................................................................................17Circuitry Platter...........................................................................................................................18Plexiglas Box..............................................................................................................................19

System Test Plan (Mechanical)........................................................................................................19DC Motor...................................................................................................................................19LED Ring...................................................................................................................................20Circuitry Platter...........................................................................................................................20Plexiglas Box..............................................................................................................................20

System Test Plan (Electrical)...........................................................................................................20Hall Sensor Test..........................................................................................................................20Voltage Regulator Test................................................................................................................21Shift Register and Buffer Test......................................................................................................21

UNIVERSITY OF PORTLAND SHILEY SCHOOL OF ENGINEERING CONTACT: ROSE HARBER


MOSIS Chip Test (Simulated).....................................................................................................21MOSIS Chip Test (Physical).......................................................................................................21Battery Test.................................................................................................................................21

Milestones.......................................................................................................................................22Project Proposal..........................................................................................................................22Functional Specifications v0.9, v.95, v.1.0...................................................................................23Website Launched.......................................................................................................................23Design Document v0.9, v0.95, v1.0.............................................................................................23Final Budget................................................................................................................................23MOSIS EDF File Completed.......................................................................................................23Microcontroller Programming Completed....................................................................................23Macro Model Completed.............................................................................................................23Testing and Debugging Completed with Macro Model................................................................23MOSIS Chips Received...............................................................................................................23Testing and Debugging with MOSIS chips completed.................................................................23Final Project v0.9, v0.95, v1.0.....................................................................................................23Founder’s Day Presentation.........................................................................................................24Post Mortem Presentation............................................................................................................24

Final Budget....................................................................................................................................24Risks...............................................................................................................................................25

MOSIS IC does not operate as intended.......................................................................................26Motor does not spin the apparatus fast enough.............................................................................26Not being able to deliver enough power to LEDs for desired brightness.......................................26Balance of the LED ring..............................................................................................................27

Facilities..........................................................................................................................................27Conclusions....................................................................................................................................27Glossary..........................................................................................................................................28Bibliography...................................................................................................................................28

IntroductionThe Persistence of Vision Globe (POV) is a spherical LED display based on the persistence of vision effect exhibited by the human eye. This effect is demonstrated with an array of LEDs



along a circular ring that is rotated around a vertical axis at an angular velocity exceeding the refresh rate of the eye, approximately 1/10th of a second. Each LED along the ring is turned on and off at desired positions to create an image. Using Hall sensor data, the Arduino microcontroller calculates the angular velocity and sends serial data to shift registers, implemented on MOSIS chips, to turn on individual LEDs along the rotating ring. The +15V DC power supply powering the DC analog motor is distinct and separate from the +5V DC battery pack supplying power to the Arduino microcontroller, LEDs, and MOSIS chip set. This design is used to avoid the problem of delivering power through a wire to a spinning apparatus. The Persistence of Vision Globe design, from Team Klickatat, is shown in Figure 1. This project follows the “sense-process-display” format by: sensing a magnetic field, processing the proper image mapping with the calculated angular velocity, and displaying the desired image.

The major design challenges posed by this project include building a light and rigid moving assembly to spin at high angular velocities required to achieve the persistence of vision effect. If it is unbalanced, off-axis rotation could result in damage. Another challenge is using a Hall sensor to calculate the angular velocity and modify the display update speed from the Arduino microcontroller in real time. These difficulties can be overcome with thorough documentation of design plans and careful testing.

Figure 1. Physical Design

This design specification provides a view of the high-level architecture by explaining the components of the major systems and the functionality of those major systems. The testing plans are discussed along with the development plan, milestones, assumptions and risks associated with the building process. An understanding of digital and analog electronic design is a skill that is assumed of the document reader.



DesignThe following sections describe an overview of how each component is interfaced, and the details for each individual component.

Architecture

Figure 1. POV Globe high-level system block diagram.

The system functionally contains three major conceptual components: sense, process, and display. A block diagram of the top level system is shown in Figure 2. Each major component is comprised of smaller components, which are described below. The system in greater detail is depicted in Figure 3.

Operating ModesThe POV Globe has one operating mode. To enter this operating mode, the user simply has to plug the apparatus into power and the LED ring will begin to spin. While spinning, an image will appear in the LEDs.

Primary Simulation ModeThe POV Globe will have one mode of operation, called Display Mode, in which angular velocity and position of the LED Ring is detected. The angular velocity and position data will then be used to illuminate the LEDs in a particular pattern, displaying an image for the observer. For example, once the POV Globe is connected to a power source, it will begin spinning. As data is shifted to the LEDs, an image will begin to appear in the illuminated rotating ring of LEDs. The proper operation of this mode is the primary concern of this project.



Figure 2. System Block Diagram.

Each component seen in Figure 3 is described below:

0-15 V DC Power SupplyThis power supply will provide up to 15 V DC to the motor in order to spin the apparatus. All other components will run off of a separate 5 V battery power supply attached to the spinning base of the apparatus. The chosen motor has a maximum DC voltage of 12V, therefore the DC voltage of the power supply will not exceed 12V.

Hall Effect SensorA Hall Effect sensor is a transducer that varies its output voltage in response to the presence and strength of a magnetic field. The sensor is excited by a stationary magnet mounted along the wall of the Plexiglas encasing. In the presence of the stationary magnet’s magnetic field, the Hall sensor will return an analog voltage signal to the Arduino microcontroller. This analog signal is then converted to a digital signal and used to calculate the position and angular velocity of the rotating LED ring.



Analog DC MotorThe analog DC motor is responsible for rotating the LED ring in order to create a stroboscopic effect and is powered by an external 0-15V power supply. This power supply is mounted to the base of the device is distinct from the battery power supply powering the circuitry on the spinning platter. The LED ring and spinning platter are mounted to the shaft of the motor and spin with the armature of the motor. In order for the human eye to observe the stroboscopic effect, the motor must rotate with a minimum angular velocity of 1,500RPM. The motor employed is able to provide a maximum of 2,000 RPM and, as long as the weight of the LED ring and platter does not surpass 2 pounds, the torque rating of the motor will be sufficient to drive the apparatus load.

MicrocontrollerThe microcontroller used in this project is the Arduino Nano, referred to hereafter as Arduino in this document. It converts the analog input of the Hall sensor (part of the sense block) into an easy-to-process digital format (using an onboard ADC). It uses the digital conversion of the analog data as an interrupt to the Arduino code that is sent serially to the MOSIS shift registers to augment the code timing delays in accordance with the calculated angular velocity. This indicates which LEDs are to be illuminated by outputting several signals (serial data and clock signal) to the MOSIS chip, the other part of the process block of the system shown in Figure 3. The Arduino outputs two distinct clock signals to the MOSIS chip to control the two sets of shift registers. The faster of the two clocks is run at 33.5 kHz.

MOSIS Integrated Circuit (IC)There are two identical custom-designed MOSIS chips used in this system. The purpose of these chips is to load serial data from the Arduino into the implemented shift registers and load the output of each flip flop into another set of shift registers, which will be sent to the current drivers. Two chips are required due to limitations of available pin count of a single MOSIS chip. The presence of these memory arrays allow the program data from the Arduino to be “shifted” into the LED image data shift register at each clock tick. Additionally, inclusion of the MOSIS chips allows the Arduino to continue to compute information without having to continuously output the current LED data. The LED count would also be limited by the pin-out of the Arduino if this approach were taken.

Current Drivers The purpose of the internal and external buffers is to increase the amount of current delivered to the LEDs. The non-inverting high-current buffers send signals directly to the LED anodes. Since it requires a fairly large (~20 mA) of current to make an LED emit enough light to become visible, these drivers may source or sink as much as 60 mA, providing enough current to illuminate a single LED.

LED Ring This is the primary portion of the Display block of the system. The ring itself, when rotated at above the minimum angular velocity, will appear spherical to the observer. It consists of 62 LEDs arranged along a rigid semi-circle shape.

Software ComponentThe code programmed onto the Arduino Microcontroller is a major component of the Process block of the system. This component, depending on settings, computes which LEDs need to



be illuminated in order to display a coherent image. The ring is represented as a two-dimensional array of LEDs within the program. The software flow chart is modeled in Figure 4.

Figure 3. The Arduino Microcontroller Software flow chart.

The main components shown are described in detail below.

Display ModeWhen the device is running in Display Mode, the program waits for the rising edge of each clock to advance serial data from the Arduino into the serial array line and load the outputs from the serial array line into the inputs of the memory array line. The Hall sensor’s output signal acts as a program interrupt in the Arduino code to calculate the angular velocity of the spinning apparatus. After storing the position and angular velocity data from the Hall sensor, that information is used to determine the correct time to illuminate the specific LEDs in the written pattern. After the frame is calculated and stored in the MOSIS chip shift registers, it is sent to the LED ring for display.

Pseudo-CodeThe program used to run the Persistence of Vision Globe runs within the Arduino. The Arduino uses a sensor signal to modify the speed of display signals sent to the MOSIS chip shift registers. The pseudo-code flow is depicted in Figure 5.



Figure 5: Arduino Microcontroller Pseudocode Modeling

User Interface Component The user interface for the persistence of vision display is a graphical user interface (GUI) program designed in Excel that allows a user to draw out desired display images in a grid format. The user can click on individual or groups of cells in the Excel spreadsheet to highlight those cells and to indicate that an LED will be turned on in that location. A preliminary design of this GUI program, named Satellite, is shown below in Figure 6.

The GUI program assembles the necessary Arduino program to display the user drawn image. The Arduino code is then uploaded to the Arduino on the Persistence of Vision Globe, which then exhibits the desired image.


Hall sensor falling signal initiates the interrupt function.

Calculate the time between rotations of the spinning apparatus and update the delay time for the display program.

Convert the image data to a serial output for the MOSIS chip at appropriate speed.


Figure 6: GUI program for image manipulation and Arduino Microcontroller code generation

MOSIS CHIPThe MOSIS chip plays an important role in serial data communication between the Arduino microcontroller and the mounted LEDs.

The MOSIS chip implements the necessary shift registers, a cascade of flip flops, specifically designed for this device. The output of each flip flop is connected to the input of the next flip flop, resulting in a “shifting in” of the data present at the input and “shifting out” the last bit in the array at each clock tick. There will be two identical MOSIS chips, due to the limited pin-count of one chip. Each output pin on the MOSIS chip drives one LED on the LED ring. Therefore the two MOSIS chips allow for 64 useable output pins.

Additionally, the custom MOSIS chips contain the necessary logic to drive the LEDs with enough current to illuminate them. The LED ring consists of a singular non-conductive ring with 31 LEDs mounted along each edge, for a total of 62 LEDs. Each LED is programmed to light up depending on its position and the angular velocity at a particular moment in time.

The MOSIS chip design features multiple rows of cascaded flip flops, which store the bits that control the illumination of the LEDs on the LED ring, necessitating control signals and peripheral logic to guide operation of these components. As seen in Figures 7 and 8, there are two clock sources. One clock times the loading of the serial data into the first line of D-Flip



Flops. D-Flip Flops (D-FF) are logical gate devices that use a clock tick to capture the value seen at the input and pass it to the output port. The output of the D-FF is set and held until the rising edge of the next clock tick. The second clock times the save/latch function for the secondary row of D-FFs sourcing the data from the output pins of the first. This arrangement of D-FFs is a finite state machine with a large number of states controlled by the serial data input and synchronous due to the clock control. The system does not a have an asynchronous set or reset. This allows for the display of the final desired LED array segment without transitional flickering.

Figure 7: B2Logic MOSIS chip schematic



Figure 8: B2Logic Design (Closer View)

Timing Diagrams



B2 Logic test scripts are written in order to verify the functionality of the MOSIS chip design. Figure 9 below demonstrates the functionality of Team Klickatat’s MOSIS chip design. The propagation of data from “Serial in” to the outputs is seen as both clocks are activated. The data is shifted into the top eight flip-flops and propagated through on the rising edge of the second clock. Figure 9 visually demonstrates the functionality of the MOSIS chip design.

Figure 9: B2Logic Timing Diagram

MOSIS Chip Layout



Upon testing and verifying the functionality of the MOSIS chip as a B2Logic.blt file, the circuit is converted into a physical layout for fabrication on silicon. Figure 10 showcases the fabrication layout depicted in the layout design program L-Edit by Tanner Research.

Figure 10: Tanner LEdit MOSIS Chip Layout

Macro Model (MOSIS Chip Backup)

Without the current presence of the MOSIS chip, a suitable macro system is created to model its functionality and verify conceptual correctness until the arrival of the fabricated MOSIS



chip in spring. For the macro model, eight M74HC595B 8 bit shift register ICs are used. Each IC contains an 8-bit serial in, parallel out shift register that feeds an 8-bit D-type storage register with separate clocks provided for both the shift register and the storage register.

The macro model provides a backup to the designed MOSIS chip set system.

Mechanical ComponentThe mechanical components of the POV globe consist of four distinct portions of the apparatus: the LED ring, the motor base, the circuitry mounting platter, and the Plexiglas box. Each portion is designed to conform to the initial plans for the POV globe and updated in accordance with experimental results.

The Motor BaseThe motor base is made of a platform of 10’’ x 10’’ plywood that is ¾’’ thick. The cradle box for the motor is made from 1 ½’’x 2 ½’’ planks cut to 3 ¾’’. These components are shown in Figure 11.

Figure 11: Base platform and cradle box components

These are attached together in a square using 2’’ wood screws to form the cradle box for the motor installation. The widest part of the motor is 2 ¼’’ which allows for a perfect fit into the interior portion of the cradle box. Figure 12 shows the top view of the base assembly with measurement details as well as the top view of the DC motor.



Figure 12: Base Design Top View and Motor Top View

This box is then installed into the center of the 10’’ x 10’’ plywood platform with angle braces. The motor is installed into the cradle box using 1’’ wood screws that fit the width of the predrilled holes in the motor mounting plate. The motor is installed so the screws are placed at the midpoint of each interior wall. This allows for airflow to remove heat generated by the motor and a consequence of the motor’s mounting plate construction. In addition, a small hole is drilled in the bottom of the cradle box to allow the DC power leads from the motor to be connected to the DC power supply. The final assembly is depicted in Figure 13. This assembly design is subject to augmentation dependent upon experimental results. Both the indirect and direct drive systems for the POV globe are under experimental consideration.

Figure 13: Base Construction



LED RingThe LED Ring is constructed from a section of preformed circular plastic in the diameter and shape needed to make the LED ring correctly. The section removed is 1’’ in width and has a diameter of 12’’. Bracing rods through the ring will allow for added strength and management of the potential flex in the plastic ring. The thickness of the ring will be 0.09’’ plus or minus an error factor depending on the manufacturer seen in Figure 14.

Figure 14: LED Ring Measurements

It is important that the LED spacing on the ring be uniform given the diameter chosen for the ring. In order to create dense image formation, a spacing of 0.5’’ is chosen given the ring size. Using the formula C=πd, the circumference of the ring is found to be 37.6991’’. With a spacing of 0.5’’ and 31 LEDs per side, a circumference space of 15.5’’ is needed to mount the LEDs leaving 3.349’’ on each side of empty space. Splitting this space equally amongst the top and bottom of the LED array gives a spacing of 1.6745’’ on the top and bottom of each side of the ring. This spacing not only allows for a more uniform LED array grid, but also less warping of the image due to the LEDs mounted near the top of the ring. The measurements and spacing diagram is viewable in Figure 15. The measurements depicted in figure 15 are subject to augmentation based upon the materials available for construction and experimental results with a variety of construction materials and sizes.



Figure 15: LED ring spacing and Circumference measurements

Circuitry PlatterThe circuitry platter holds all the electronic circuitry needed to operate the LEDs correctly as well as its own 5V DC power supply. The most important part of the circuitry platter is that all the components are secure and relatively balanced. In order to reduce the current drawn by the DC motor, the mass of the entire apparatus (LED ring and Circuitry Platter) must be minimized and not exceed 2lbs. A 3’’ radius platter, made from a very light material, is used and all the circuitry is secured to the bottom using an affixture plan to be determined through testing. A platter layout and measurement schematic appears in Figure 16.

Figure 16: Circuitry Platter Schematic and layout



Plexiglas BoxThe Plexiglas box employed in the design is used to accomplish three goals. The first is to make the device safe for viewing and protect viewers from any mechanical failure. The second is to provide a mounting surface for the permanent magnet used by the Hall Sensor to determine angular velocity and position. The third is to provide a mounting surface for the top bearing assembly that stabilizes the top portion of the ring. The bearing assembly functions by fitting around the central bracing rod and providing a nearly frictionless guide for the central axis of rotation. The Plexiglas box design is shown in Figure 17.

Figure 17: Plexiglas Box

System Test Plan (Mechanical)To ensure the proper functionality of each of the mechanical components, they all must be put through extensive testing and augmented according to the outcomes of those tests to assure the best possible design.

DC Motor1. The DC Motor will be connected to the DC power supply module provided in Shiley 306.2. The voltage will be increased from 0 to 12 Volts without the motor loaded with weight

and the current draw will be monitored with a Digital Multi Meter (DMM).3. Using weights attached to the armature of the motor, this process will be repeated.Expectation: Through experimental trials, the maximum weight limit will be found within the power supply parameters provided (maximum 15V/ 3 Amp supply). The outcome of this test will give further parameters to the apparatus build and dictate the DC motor’s suitability for the task.

LED Ring1. After the assembly is fabricated, the LED ring will be mounted to the armature of the DC

motor.



2. The motor will be brought up to speed by ramping up the voltage and the LED ring operation will be observed.

Expectation: The LED ring will spin without flex or wobble on a singular axis of rotation aligned to the armature of the motor.

Circuitry Platter1. After the assembly is fabricated, the circuitry platter will be mounted to the armature of

the DC Motor .2. The motor will be brought up to speed by ramping up the voltage and the LED ring

operation will be observed.3. The experiment will be repeated with the addition of the LED ring to make sure their

expected operations do not change the expected operation of one another.Expectation: The circuitry platter will spin without wobble, loss of components, or negation of the functionality of the circuitry on the platter. The addition of the LED ring will not change the expected functionality of the circuitry platter.

Plexiglas Box1. After the assembly is fabricated, the Plexiglas box will be placed over the apparatus,

aligning the central bracing through the bracing bearing system.2. The motor will be brought up to speed by ramping up the voltage and the operation of the

bearing system and the Plexiglas box will be observed.Expectation: The Plexiglas box will align the axis of rotation of the POV globe perpendicular to the base surface and will provide a nearly frictionless contact.

System Test Plan (Electrical)Tests are needed to ensure proper functionality of the device during the design and build processes. The components can be individually tested before they are integrated into the completed product.

Hall Sensor Test1. The Hall sensor will be wired up according to manufacturer specification.2. Connect the sensor’s output to an Arduino pin so that the output voltage value can be monitored through a serial connection between the Arduino and a computer displaying the serial monitor.3. Using a magnet, change the magnetic field intensity in front of the sensor while observing the sensor output signal.Expectation: The output voltage of the sensor should drop from a high level to a value near zero when a strong magnetic field is present directly in front of the Hall sensor.4. Connect the Hall sensor to an interrupt assigned pin on the Arduino microcontroller.5. Use an Arduino program that utilizes the falling edge of the signal input as a trigger for the interrupt assigned pin.



6. Keep track of the Arduino’s use of its interrupt function when the sensor changes output values due to the changing magnetic field when a magnet is brought near.Expectation: The Arduino should run its interrupt function when it senses the falling edge of the Hall sensor’s output signal.

Voltage Regulator Test1. Wire up a 5V voltage regulator according to manufacturer specification.2. Use a voltmeter to measure the output voltage.Expectation: The output voltage of the regulator should be near 5V.

Shift Register and Buffer Test1. Wire up a shift register IC according to manufacturer specification.2. Connect the outputs of the shift register to the inputs of the buffer IC.3. Connect LEDs with current limiting resistors to the buffer outputs.4. Use serial data and clock signals from an Arduino to attempt to load and push high and low signals to the LEDs.Expectation: The LEDs should turn on and off when the appropriate serial data and clocks are manipulated. The shift register should act as an expansion of output pins from the Arduino. No IC or LED should become hot or burn during the test.

MOSIS Chip Test (Simulated)1. Create a circuit schematic of the MOSIS chip in B2Logic.BLT.2. Build a test vector file that simulates the serial loading from the Arduino.3. Simulate the MOSIS circuit with the test vector file.4. Observe the output trace of the circuit after the simulation completes.Expectation: The output trace should show changing clock and serial input signals along with a change in output values once the desired data array is loaded. All signals should either be high or low with no uncertain values.

MOSIS Chip Test (Physical)1. Run the Persistence of Vision Globe with the macro model shift registers in place. Observe the LED output.2. Replace the shift registers in the Persistence of Vision Globe with the MOSIS chips.3. Run the display with the same image and compare the LED output with the macro model’s output.Expectation: The display should not display any differently with the MOSIS chips.

Battery Test1. Charge the battery with the DC power source.2. Use a digital voltmeter to test the voltage of the battery when it has completed charging.3. Plug the battery into the rotating assembly to power the persistence of vision display.4. Run the persistence of vision display until power runs low.



Expectation: The battery should supply approximately 7.4 Volts with 2200mA. The Persistence of Vision Globe should be able to run for more than 40 minutes without recharging the battery.

MilestonesTable 1 lists the milestones necessary for the completion of the project.

Table 1. Milestone Chart

Line Description Completion Date 1 Project Proposal 30 Aug 20132 Functional Specifications v0.9 20 Sep 2013

3 Functional Specification v0.95 27 Sep 20134

56789

September Program ReviewWebsite Officially LaunchedFunctional Specifications v1.0 ApprovalComponent Selection CompletedProject Business AssessmentInitial MOSIS EDF file completed

28 Sep 201301 Oct 201304 Oct 201308 Oct 201312 Oct 201331 Oct 2013

10 Design Document v0.9 01 Nov 201311 Design Document v0.95 08 Nov 2013 12 Design Document v1.0 15 Nov 201313 Final Budget 15 Nov 201314 MOSIS EDF File Completed 15 Nov 201315 Microcontroller Programming Completed 31 Jan 20141617

Macro Model CompletedTesting and Debugging Completed with Macro Model

15 Feb 201406 Mar 2014

1819

20

MOSIS Chips receivedTesting and Debugging with MOSIS chips completedFinal Report v0.9

13 Mar 201421 Mar 2014

21 Mar 201421 Final Report v0.95 28 Mar 201422 Final Report v1.0 04 Apr 201423 Founder’s Day Presentation 08 Apr 201424 Post Mortem Presentation 17 Apr 2014

Project Proposal Submit project idea along with initial specifications to EE/CS faculty.

Functional Specifications v0.9, v.95, v.1.0 Edited drafts of the Functional Specification and Requirements are submitted to Dr. Osterberg for approval and revision.



Website Launched The website will be launched and give the public an insight into the project’s documents and specifications. This website will be accessible and help the members communicate more efficiently.

Design Document v0.9, v0.95, v1.0The design document will be submitted to Dr. Osterberg several times for revision.

Final BudgetThe final budget includes the costs related to the materials needed and other projected costs to be reported to the EE/CS faculty.

MOSIS EDF File CompletedThe EDF file, which will outline the MOSIS chips’ functional logic layout created in B2 Logic, will be submitted to Dr. Osterberg who will further inspect the design and then translate the EDF file to a CIF file for MOSIS fabrication.

Microcontroller Programming Completed The Arduino Microcontroller programming, responsible for sending serial data to the MOSIS chips and managing LED lights, will be completed. Coding will be documented and commented for clarity.

Macro Model CompletedThe Macro Model will be fully constructed to allow for initial testing and adjustments to the initial design.

Testing and Debugging Completed with Macro ModelTesting and debugging of the entire system will be required to ensure the functionality of the apparatus. The requirements must be tested extensively in order to show full operation of the POV globe.

MOSIS Chips ReceivedThe MOSIS chips are received from manufacturer.

Testing and Debugging with MOSIS chips completedThe MOSIS chips are placed into the Macro model taking the place of the shift register ICs. All adjustments and augmentations to the design are made to accommodate the addition of the MOSIS chips.

Final Project v0.9, v0.95, v1.0The final report documenting the entire project must be submitted to Dr. Osterberg for approval.

Founder’s Day PresentationThe team will give a presentation of the project highlighting various features of the design, various uses of the device, and potential other features of the project. At this presentation, the team will show a demonstration of the POV globe.



Post Mortem Presentation Following the Founder’s Day presentation, the team will give a presentation to peers and the EE/CS faculty about the project’s success and potential areas of improvement.

Final BudgetLine Material description # of parts Rate Amount

$/unit $Subtotal

1 LEDs 70 0.19 13.302 5V voltage regulators 5 0.45 2.253 Buffers 8 2.49 19.924 Hall effect sensor 5 1.15 5.755 Magnet 2 0.49 0.986 8-bit shift registers 8 0.60 4.807 Resistors 100 0.05 5.008 Capacitors 20 0.13 2.609 Microcontroller 1 25.00 25.0010 USB mini B cable 1 2.49 2.4911 Battery 1 25.00 25.0012 Battery charger 1 7.00 7.0013 Barrel jack adapter 2 0.45 0.9014 Ribbon cable 1 10.00 10.0015 Proto boards 2 14.95 29.9016 Motor 1 30.00 30.0017 Motor power source 1 0.00 0.0018 MOSIS chip 2 0.00 0.0019 Frame/base 1 0.00 0.0020 Plexiglass enclosure 1 0.00 0.0021 Paint 1.00 10.00 10.0022 Miscellaneous components 50.00

Total 244.89

1 Light emitting diodes will be mounted on the rotating ring.2 Voltage regulators will ensure that ICs do not burn out.3 Buffers will drive the current necessary to light the LEDs.

4A Hall effect sensor will detect a change in magnetic field as the rotating ring passes by a magnet to help determine speed of rotation.

5 A magnet will be needed to interact with the Hall effect sensor.6 8-bit shift register ICs will convert serial data from the microcontroller to output values of



individual output pins for lighting LEDs. (For macro model)7 Resistors limit the current through the LEDs to prevent them from burning out.8 Decoupling capacitors reduce noise seen by each IC from the power line.9 An Arduino Nano microcontroller processes and sends serial data to be displayed.10 The USB cable will be used to program the microcontroller.11 A rechargeable battery will power the moving assembly.12 A battery charger will be needed to recharge the battery.13 Barrel jack adaptors will allow the battery to be plugged in easily.14 Ribbon cable will keep the wires to the LEDs along the ring in order.15 Proto boards will secure the microcontroller and ICs to the spinning assembly.16 The motor will be mounted beneath the LED ring in order to rotate it.17 DC power supplies to power the motor will be supplied by the school.18 MOSIS chips will implement shift registers on the final model.

19The frame and base will form the foundation to secure the motor and the ring assembly to hold LEDs and ICs.

20A clear Plexiglas enclosure will allow for easy visibility without the danger of contacting the moving assembly.

21 Paint will be used on the final model.22 Miscellaneous parts include any replacements or new parts that need to be ordered.

RisksTable 2 details the anticipated risks to the timely completion and delivery of the project’s final product.

Table 2. Project Risks and Contingencies

Risk Severity

Likelihood

MOSIS IC does not operate as intended. Low Low

Motor does not spin the apparatus fast enough to enable persistence of vision by human eye

High Moderate

Not being able to deliver enough power to LEDs for desired brightness High Moderate

Balance of the LED ring High Low

MOSIS IC does not operate as intendedIn order for the LEDs to light up in a specified pattern, the shift registers, implemented by MOSIS chips, must deliver the correct data to the LEDs. For this to happen, the MOSIS chips must be designed in such a way that they produce expected output without error. Flaws in the



MOSIS chip design will result in skewed and unexpected output being delivered to the ring of LEDs. In order to mitigate these risks, Team Klickitat will test and debug errors by performing extensive digital simulations prior to submitting the design for fabrication.

Should the MOSIS chip return from the foundry with problems, they will be detected through visual inspection of the POV globe during operation. However, there are alternatives to the custom MOSIS chips. One such alternative is a pre-made shift register IC that can be purchased online. These ICs will be used to create the Macro Model system prior to receiving the MOSIS chips. Should the MOSIS chip function incorrectly, the back-up plan of action will be to replace the MOSIS chips with a functioning shift register IC, which will be sufficient to pass along data to the ring of LEDs. If using the shift register ICs becomes too cumbersome, Team Klickitat will directly use the microcontroller to drive the illumination of the LED ring.

Motor does not spin the apparatus fast enoughIn order to create a persistence of vision globe, it is important that the motor is powerful enough to spin the weight of the platform fast enough to create the persistence of vision effect to the human eye. The weight of the rotating disk is estimated to be around 1 pound. In order for the human eye to experience POV, the LED ring must spin at a rate of 1500 RPM (25RPS). This means that we will need to source a motor with high torque and able to produce 1500RPM. Many of these motors require a 12V input to produce these necessary results.

There are two primary issues surrounding sourcing an appropriate motor. The first is that we will not be able to find a motor from an online retailer inexpensive enough to fit our budgetary constraints. Many of the motors we have been looking at online run from $25 - $30, but require the purchase of greater than 50 units. Others, that are able to be purchased individually, are too expensive to afford. The second issue surrounding the motor is that it will not be physically able to spin the apparatus at a quick enough rate. Should this problem occur, we will need to downsize the overall circumference of the LED ring so as to minimize weight of the apparatus and stress on the motor.

Not being able to deliver enough power to LEDs for desired brightness

The globe will only be an effective POV device if the LEDs are bright enough to provide contrast in an illuminated room. In order for the LEDs to be an effective display, there has to be enough current supplied via the battery pack. The LEDs will draw a high amount of current over an extended period of time, thus, the battery pack will have to be able to supply this current.

Surpassing this obstacle will be a matter of finding a sufficient battery pack and reducing ambient light in operation. Additionally, we must use power-efficient LEDs.

Balance of the LED ringThe POV effect will only be seen if the LED ring spins on an even stable plane. In order for this to happen, the axis of rotation of the LED ring must not only be perpendicular to the flat rotating disk, but also parallel with the shaft of the motor to prevent any off axis spinning. The balance of weight throughout the apparatus will be essential to even rotation of the ring.



Should one side be heavier than the other due to the weight of the battery pack or Arduino Microcontroller, the apparatus will not function correctly.

In order to balance the weight of the apparatus evenly, small counter weights will be used to counteract any inequality in weight. A level and right angled device will be used to visually inspect the balanced weight of the device.

FacilitiesThe Senior Design Lab in Shiley Room 306 will be available for electronics testing and construction as well as soldering as needed. Several major design pieces, including the protective Plexiglas box around the apparatus, the circular spinning platter, grommet for securing platter to motor shaft, motor housing and base, and LED ring will have to be designed and manufactured by team members or ordered through the machine shop. The computers in the computer lab in Shiley 208 are equipped with the necessary B2 logic software to design and simulate the logic gates and create the EDF files necessary for MOSIS construction. The Electronics Lab and technicians in Shiley 110 will be a great resource in the MOSIS IC mounting and integration as well as building assistance for the overall apparatus.

ConclusionsThe POV Globe project is fully realized within the design schematics presented in the design document. Each portion of the architecture is chosen according to its functionality. With the full schematics for mechanical builds, Arduino code, and a newly designed GUI to make the programming of the Arduino easier to automate, the implementation of the device from the plans is very straightforward. In addition to the schematics presented, the finished MOSIS chip design allows for a timely completion of the device with guaranteed functionality. The testing plan set in place will allow for experimental evidence to be used to augment the design of the device for optimum functionality. The most prominent challenge of the system is to manage the power needs of the LED circuitry as well as make the mechanical system function as designed, especially the DC Motor. The successful fabrication of this device is guaranteed through the extensive planning of the design.

GlossaryHall Effect Sensor: A transducer component that varies its output voltage in direct relation to a change in magnetic field strength. This component will be used to detect the speed and position of the spinning ring apparatus.

IC: Integrated Circuit. A complex circuit patterned and manufactured on a semiconductor substrate.



LED: Light Emitting Diode. A semiconductor light source that acts as a one-way current valve allowing holes and electrons to recombine over a predetermined band gap to emit energy in the form of photons.

MOSIS: The MOSIS educational program is a service which provides the fabrication of ICs free of charge for educational purposes.

POV: Persistence of Vision is an effect in which the human eye experiences the stroboscopic effect (See Introduction)

D-FF: D-Flip Flop is a logical gate device used to capture input data and shift it to an output port at a determined clock cycle event.

BibliographyFederal Communications Commission. "What We Do." FCC, n.d. Web. 14 Sept. 2013.

<http://www.fcc.gov/what-we-do>.

US Commercial Service, "RoHS: Restriction of the Use of Certain Hazardous Substances." Export.gov, 16 May 2013. Web. 14 Sept. 2013. <http://export.gov/europeanunion/weeerohs/rohsinformation/index.asp>.


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