University of Portland
School of Engineering
5000 N. Willamette Blvd.
Portland, OR 97203-5798
Phone 503 943 7314
Fax 503 943 7316
Design
Project POV globe: Persistence of Vision
LED Display
EE 480: Senior Design
Team 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
Fall 2013
Design Document
Team Klickitat
Rev. 1.0
Page 2
Table of Contents
Introduction .................................................................................................................................................. 4
Design........................................................................................................................................................... 5
Architecture ............................................................................................................................................. 5
Operating Modes ..................................................................................................................................... 5
Primary Simulation Mode....................................................................................................................... 5
0-15 V DC Power Supply ....................................................................................................................... 6
Hall Effect Sensor.................................................................................................................................... 6
Analog DC Motor.................................................................................................................................... 7
Microcontroller ........................................................................................................................................ 7
MOSIS Integrated Circuit (IC) ............................................................................................................... 7
Current Drivers ........................................................................................................................................ 7
LED Ring ................................................................................................................................................. 7
Software Component............................................................................................................................... 8
Display Mode .......................................................................................................................................... 8
Pseudo-Code ............................................................................................................................................ 9
User Interface Component ...................................................................................................................... 9
MOSIS CHIP ......................................................................................................................................... 10
Timing Diagrams................................................................................................................................... 13
MOSIS Chip Layout ............................................................................................................................. 14
Macro Model (MOSIS Chip Backup) .................................................................................................. 15
Mechanical Component............................................................................................................................. 15
The Motor Base ..................................................................................................................................... 15
LED Ring ............................................................................................................................................... 17
Circuitry Platter ..................................................................................................................................... 18
Plexiglas Box ......................................................................................................................................... 19
System Test Plan (Mechanical)................................................................................................................. 19
DC Motor ............................................................................................................................................... 19
LED Ring ............................................................................................................................................... 20
Circuitry Platter ..................................................................................................................................... 20
Plexiglas Box ......................................................................................................................................... 20
System Test Plan (Electrical) .................................................................................................................... 20
Hall Sensor Test..................................................................................................................................... 20
Voltage Regulator Test.......................................................................................................................... 21
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Shift Register and Buffer Test .............................................................................................................. 21
MOSIS Chip Test (Simulated).............................................................................................................. 21
MOSIS Chip Test (Physical) ................................................................................................................ 21
Battery Test ............................................................................................................................................ 21
Milestones .................................................................................................................................................. 22
Project Proposal ..................................................................................................................................... 22
Functional Specifications v0.9, v.95, v.1.0 .......................................................................................... 23
Website Launched ................................................................................................................................. 23
Design Document v0.9, v0.95, v1.0 ..................................................................................................... 23
Final Budget........................................................................................................................................... 23
MOSIS EDF File Completed................................................................................................................ 23
Microcontroller Programming Completed........................................................................................... 23
Macro Model Completed ...................................................................................................................... 23
Testing and Debugging Completed with Macro Model ...................................................................... 23
MOSIS Chips Received ........................................................................................................................ 23
Testing and Debugging with MOSIS chips completed ....................................................................... 23
Final Project v0.9, v0.95, v1.0 .............................................................................................................. 23
Founder’s Day Presentation .................................................................................................................. 24
Post Mortem Presentation ..................................................................................................................... 24
Final Budget ............................................................................................................................................... 24
Risks ........................................................................................................................................................... 25
MOSIS IC does not operate as intended .............................................................................................. 26
Motor does not spin the apparatus fast enough .................................................................................... 26
Not being able to deliver enough power to LEDs for desired brightness ........................................... 26
Balance of the LED ring ....................................................................................................................... 27
Facilities ..................................................................................................................................................... 27
Conclusions ................................................................................................................................................ 27
Glossary...................................................................................................................................................... 28
Bibliography............................................................................................................................................... 28
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CONTACT: ROSE HARBER
Design Document
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Rev. 1.0
Page 4
Introduction
The 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
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associated with the building process. An understanding of digital and analog electronic design
is a skill that is assumed of the document reader.
Design
The 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 Modes
The 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 Mode
The 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.
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Figure 2. System Block Diagram.
Each component seen in Figure 3 is described below:
0-15 V DC Power Supply
This 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 Sensor
A 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.
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Analog DC Motor
The 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.
Microcontroller
The 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 pinout 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.
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Software Component
The 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 twodimensional 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 Mode
When 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.
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Pseudo-Code
The 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.
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 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.
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Figure 6: GUI program for image manipulation and Arduino Microcontroller code generation
MOSIS CHIP
The 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 pincount 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
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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
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Figure 8: B2Logic Design (Closer View)
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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
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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
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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 Component
The 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 Base
The 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.
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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
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LED Ring
The 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.
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Figure 15: LED ring spacing and Circumference measurements
Circuitry Platter
The 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
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Plexiglas Box
The 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 Motor
1. 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.
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LED Ring
1. 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 Platter
1. 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 Box
1. 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 Test
1. 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.
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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 Test
1. 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 Test
1. 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 Test
1. Charge the battery with the DC power source.
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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.
Milestones
Table 1 lists the milestones necessary for the completion of the project.
Table 1. Milestone Chart
Line
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
Description
Project Proposal
Functional Specifications v0.9
Functional Specification v0.95
September Program Review
Website Officially Launched
Functional Specifications v1.0 Approval
Component Selection Completed
Project Business Assessment
Initial MOSIS EDF file completed
Design Document v0.9
Design Document v0.95
Design Document v1.0
Final Budget
MOSIS EDF File Completed
Microcontroller Programming Completed
Macro Model Completed
Testing and Debugging Completed with
Macro Model
MOSIS Chips received
Testing and Debugging with MOSIS
chips completed
Final Report v0.9
Final Report v0.95
Final Report v1.0
Founder’s Day Presentation
Post Mortem Presentation
Completion Date
30 Aug 2013
20 Sep 2013
27 Sep 2013
28 Sep 2013
01 Oct 2013
04 Oct 2013
08 Oct 2013
12 Oct 2013
31 Oct 2013
01 Nov 2013
08 Nov 2013
15 Nov 2013
15 Nov 2013
15 Nov 2013
31 Jan 2014
15 Feb 2014
06 Mar 2014
13 Mar 2014
21 Mar 2014
21 Mar 2014
28 Mar 2014
04 Apr 2014
08 Apr 2014
17 Apr 2014
Project Proposal
Submit project idea along with initial specifications to EE/CS faculty.
UNIVERSITY OF PORTLAND
SHILEY SCHOOL OF ENGINEERING
CONTACT: ROSE HARBER
Design Document
Team Klickitat
Rev. 1.0
Page 23
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, v1.0
The design document will be submitted to Dr. Osterberg several times for revision.
Final Budget
The 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 Completed
The 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 Completed
The Macro Model will be fully constructed to allow for initial testing and adjustments to the
initial design.
Testing and Debugging Completed with Macro Model
Testing 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 Received
The MOSIS chips are received from manufacturer.
Testing and Debugging with MOSIS chips completed
The 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, v1.0
The final report documenting the entire project must be submitted to Dr. Osterberg for
approval.
UNIVERSITY OF PORTLAND
SHILEY SCHOOL OF ENGINEERING
CONTACT: ROSE HARBER
Design Document
Team Klickitat
Rev. 1.0
Page 24
Founder’s Day Presentation
The 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 Budget
Line
Material description
# of parts
Rate
$/unit
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
LEDs
5V voltage regulators
Buffers
Hall effect sensor
Magnet
8-bit shift registers
Resistors
Capacitors
Microcontroller
USB mini B cable
Battery
Battery charger
Barrel jack adapter
Ribbon cable
Proto boards
Motor
Motor power source
MOSIS chip
Frame/base
Plexiglass enclosure
Paint
Miscellaneous components
70
5
8
5
2
8
100
20
1
1
1
1
2
1
2
1
1
2
1
1
1.00
Total
1
2
0.19
0.45
2.49
1.15
0.49
0.60
0.05
0.13
25.00
2.49
25.00
7.00
0.45
10.00
14.95
30.00
0.00
0.00
0.00
0.00
10.00
Amount
$
Subtotal
13.30
2.25
19.92
5.75
0.98
4.80
5.00
2.60
25.00
2.49
25.00
7.00
0.90
10.00
29.90
30.00
0.00
0.00
0.00
0.00
10.00
50.00
244.89
Light emitting diodes will be mounted on the rotating ring.
Voltage regulators will ensure that ICs do not burn out.
UNIVERSITY OF PORTLAND
SHILEY SCHOOL OF ENGINEERING
CONTACT: ROSE HARBER
Design Document
Team Klickitat
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
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19
20
21
22
Rev. 1.0
Page 25
Buffers will drive the current necessary to light the LEDs.
A Hall effect sensor will detect a change in magnetic field as the rotating ring passes by a magnet
to help determine speed of rotation.
A magnet will be needed to interact with the Hall effect sensor.
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)
Resistors limit the current through the LEDs to prevent them from burning out.
Decoupling capacitors reduce noise seen by each IC from the power line.
An Arduino Nano microcontroller processes and sends serial data to be displayed.
The USB cable will be used to program the microcontroller.
A rechargeable battery will power the moving assembly.
A battery charger will be needed to recharge the battery.
Barrel jack adaptors will allow the battery to be plugged in easily.
Ribbon cable will keep the wires to the LEDs along the ring in order.
Proto boards will secure the microcontroller and ICs to the spinning assembly.
The motor will be mounted beneath the LED ring in order to rotate it.
DC power supplies to power the motor will be supplied by the school.
MOSIS chips will implement shift registers on the final model.
The frame and base will form the foundation to secure the motor and the ring assembly to hold
LEDs and ICs.
A clear Plexiglas enclosure will allow for easy visibility without the danger of contacting the
moving assembly.
Paint will be used on the final model.
Miscellaneous parts include any replacements or new parts that need to be ordered.
Risks
Table 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
UNIVERSITY OF PORTLAND
SHILEY SCHOOL OF ENGINEERING
CONTACT: ROSE HARBER
Design Document
Team Klickitat
Rev. 1.0
Page 26
MOSIS IC does not operate as intended
In 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 enough
In 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.
UNIVERSITY OF PORTLAND
SHILEY SCHOOL OF ENGINEERING
CONTACT: ROSE HARBER
Design Document
Team Klickitat
Rev. 1.0
Page 27
Balance of the LED ring
The 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.
Facilities
The 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.
Conclusions
The 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.
UNIVERSITY OF PORTLAND
SHILEY SCHOOL OF ENGINEERING
CONTACT: ROSE HARBER
Design Document
Team Klickitat
Rev. 1.0
Page 28
Glossary
Hall 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.
Bibliography
Federal 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>.
UNIVERSITY OF PORTLAND
SHILEY SCHOOL OF ENGINEERING
CONTACT: ROSE HARBER