EE490 Product Design

Solar Sailor - Interactive Educational Game (IEG)March 2011

Victor Arosemena, Taylor DeIaco, William McNally, Joe Rodriguez, Anthony Santistevan, Loren Schwappach, Jeremy Struebing and Noemi R. Wikstrom

Supervising Professor: Dr. Kathy KasleyDepartment of Computer and Electrical Engineering

Colorado Technical UniversityColorado Springs, CO

Abstract – The objective of this project is to design an Interactive Educational Game (IEG) that will simulate the frictionless environment of space and orbital mechanics. As part of the course requirements the team will generate a list of performance criteria from a system description in the form of a Requirements Document. This paper will focus on the evaluation of the design in terms of performance, costs and trade-offs.

I. INTRODUCTION

HIS project is part of the course requirements for the product design series EE490 and EE491. The Creative

Solutions Capstone Design team has decided to engineer and donate an educational, interactive, astronomy game whose purpose is to teach children from the ages six and above about the solar system and orbital mechanics.

T

BACKGROUND INFORMATION

The Imagination Celebration is a non-profit organization whose mission is to provide educational and artistic opportunities for children of all ages. The Colorado Springs Imagination Celebration center is located inside the Colorado Springs Citadel Mall. The Kennedy Center Imagination Celebration is an independent foundation dedicated to bringing arts to life in the Pikes Peak region. The center makes programs accessible regardless of economic barriers, disabilities or geographic distances. [1] The purpose of an interactive educational game is to help children learn about orbital mechanics and the solar system. The game is a simulator which will provide a safe environment to test real world phenomena. [2]

Figure 1: Photo of the Imagination Center located at the Citadel Mall, Colorado Springs. (Provided by Creative Solutions Team)

AcronymsAcronym Definition

AFS Air Flow System

ARS Air Return System

CFM Cubic Feet per Minute

CPSC Consumer Product Safety Commission

IEG Interactive Educational Game

LCD Liquid Crystal Display

LED Light-Emitting Diode

MCU Microcontroller

RF Radio Frequency

RPM Revolutions Per Minute

SS Solar Sailor

SSE Solar Sailor Explorer

STEAM Science, Technology, Engineering, Art, and Mathematics

UI User Interface

Table 1: Acronyms and Definition of Terms.

1

EE490 Product Design

Product Overview

The Solar Sailor (SS) interactive game will be a large enclosed system, contained within a table approximately 2 ft. and 6 inches high, 4 ft. and 10 inches wide, and 4 ft. and 6 inches long (the actual design may be slightly larger due to material constraints). The top level of the table will contain an illuminated planet rotating at various speeds (simulating various planetary orbital speeds) via a mechanical arm circularly around an illuminated sun at the SS center. The system will be covered by a transparent Lexan cover. An air propelled rover (spaceship) will be navigated by the user over a table similar to air hockey game (demonstrating frictionless space). The player will be given a mission to visit each of the eight planetary bodies in our solar system. The player will then proceed to navigate the air propelled space ship using a limited amount of fuel (represented by time) to the planet. If the spaceship reaches the planet, then the planet will flash/illuminate and an LCD will display planetary facts, the distance covered, and amount of fuel used. Thereafter the LCD will provide the player with their next planetary mission after positioning the spaceship back at home base. If the player fails to reach the planet (runs out of fuel) the LCD will inform the user of the mission failure and reset the system for the next attempt.

Product Users

The SS shall be appropriate for play by children from the ages of seven and up who possess a basic 2nd grade level English reading proficiency. Children under the age of eight years old should be supervised by an adult at all times while using the SS. The SS players will also need to have a basic level of hand/eye coordination in order to successfully use the SS joystick.

Product Use Constraints

The SS shall require AC power and should be located within 3 feet of a 110 volts electric receptacle. The game shall be contained within a large table with a locked removable side opening for service and repair. To ensure the safety of the users, no individual is allowed to touch the internal components of the system without a thorough understanding of the electrical and mechanical components of the design.

Engineering Constraints

The complete cost for the project shall not exceed the amount of $800.00 USD. The design shall be light enough for transportation, no more than 200 pounds. The design shall be as robust and reliable as possible, since no maintenance will be provided by the Creative Solutions team after the completion of the project. The life expectancy of all

components of the design shall be greater than 3 years without maintenance. The table surface shall be able to withstand a minimum of 200 pounds of pressure.

Assumptions

Product assumptions for the SS system include: Users are a minimum of 3 feet in height. The SS will be contained within the Imagination Celebration at the Citadel Mall in a conditioned indoor environment with standard temperature, humidity, and air quality. The SS will be provided a local conditioned 120VAC power source. The SS will sits on a flat, level floor.

Project Requirement Objectives

The primary objectives for the Solar Sailor include:

Demonstrate the concept of frictionless space. Provide an interactive learning tool for engaging

astronomical information. Exhibit the mechanics involved in space vehicle

thrust. Teach children the importance of fuel conservation in

space exploration. Present the physics of planetary motion around a

solar body.

High Level Block Diagram

IEG has several design components. The mechanical component includes the planet driver, the Spaceship and the Air table design. The software component includes the Spaceship communication segment, the LCD display interface and the Game Control protocol. The electrical component includes power consideration in the design, Spaceship circuitry, sensors and LCD connections and power.

The Figure 2 below is a representation of the IEG components for this design.

Figure 2: High Level Block Diagram for the IEG design.

2

EE490 Product Design

For each component in the SS design two members of the team were assigned to provide the description, functionality, parts and relevant information about their section. The table below lists the required tasks and the team members assigned to complete them. Reference the Schedule Section for more details.

Component Tasks Team MemberAir Flow System (AFS)

DesignRequirementsParts ListsTest Plan

Loren SchwappachVictor Arosemena

Gear Motor and Rotating Arm

DesignRequirementsParts ListsTest Plan

Noemi WikstromJeremy Struebing

Shuttle DesignRequirementsParts ListsTest Plan

Joe RodriguezAnthony Santistevan

Microcontroller &Software

DesignRequirementsParts ListsTest Plan

William McNally Taylor DeIaco

Sensor ResearchPart ListsTest Plan

Taylor DeIacoWilliam McNally

Parts Lists Compile the Parts List

Loren Schwappach

Spec Doc Write the Product Specification Document

Loren Schwappach

Test Plan Write the Test Plan

Victor Arosemena

IEEE Report Data Collection and formatting

Noemi Wikstrom

Man Hours Data Collection and formatting

Noemi Wikstrom

Presentation Data Collection and Formatting

Taylor DeIaco

Table 2: List of assigned tasks and components of the design.

Hardware Interface

The Solar Sailor will have several hardware components that will directly interact with the MCU. The microcontroller unit will provide commands to turn on and off and directives to adjust the speed and sensors to indicate when the spaceship has reached its destination (home base or planet). Each sensor has a specific purpose in the overall design mainly to define the states that will enable and reset the condition of the main controller.

Other components in the design will be autonomous of the main controller and their interface is secondary to the state of

the game. The figure below provides a representation of the main controller interface in the Solar Sailor Design. The figure below is a representation of the system Hardware Interface.

Figure 3: Solar Sailor (Power & Communication) Block Diagram (See Appendix)

Software Interface

The heart of the Solar Sailor is the microprocessor kernel. At this state in the design process there is an option for using one of two microprocessors to make up the kernel of the system. The first possibility is the Analog Devices ADuC7026 Precision Analog Microcontroller. The soul of the controller is the 16-bit/32-bit ARM7TDMI RISC processor, which will provide all the functionality needed to control all aspects of the Solar Sailor. The analog components of this controller features 12-bit precision for all analog to digital (ADC) and digital to analog (DAC) conversions. The controller provides up to 16 input ADC channels or 12 input ADC channels and four DAC output channels. [5]

The second microprocessor under consideration is the Atmel ATMega24, the big brother to the ATiny24 which will be the microprocessor on the puck receiving the transmitted signal from the main processor. Experimentation is scheduled as one of the first design validation steps upon the receipt of the hardware that will be ordered upon the approval of the initial design concept.

Regardless of the actual processor chosen, the requirements of the design are consistent. The software control as shown in figure 4 will be the operation of the communication between the controller kernel and the entire game system.

3

EE490 Product Design

Figure 4: Software Interface of components of the Solar Sailor. (See Appendix)

Figure 5: Debounce schematic

The input into the system will be received from the user interface. Each input signal will be passed through a second-order low pass filter to eliminate signal bounce from being introduced into the processor kernel. All processes instantiated by the microprocessor will be interrupt driven. They will be separated into two operations, game mode and non-game mode. As shown in figure 1, the first operation after the initial power up routines is to ensure that the puck is in its home position. If the puck is not in the home position will automatically launch the puck return system. Once system has determined that the puck is home the system will enter an idle state waiting from input from the user. Standard messages will be displayed to the LCD interface upon entering the game mode.

Once a game mode instance has been initiated and the welcoming text has been presented, the mission statistics will be displayed. This state will allow the user to select from all the possible missions available. Revision one of the Solar Sailor will incorporate the planet characteristics of solar system that Earth is a member of, later revisions will have the opportunity of modifying these parameters to simulate other solar systems around the universe.

Once the user accepts the displayed mission, the mission parameters will be loaded into the instantiation of the game class. The communication channels between the processor kernel and the puck, and the processor and the planet will be initiated. The blower motor will be enabled and the game will wait for the planet rotation to come up to speed.

Once the system has been successfully initiated the system will relinquish control to the user input device. The user will have the ability to engage one of four contacts within the joy stick input device. Each switch of the joy stick will correspond with one of the possible motor control states. The control states are defined as JOY_STICK_FORWARD the puck will be accelerated in the orientation of the cone of the Sailor, by delivering a positive referenced ON signal to the forward/reverse propulsion unit. The JOY_STICK_BACK state will result in a negative referenced ON signal to the forward/reverse propulsion system. The JOY_STICK_LEFT state will result in a negative referenced ON signal being sent to rotational propulsion system delivering a counter clock-wise acceleration to the puck. The JOY_STICK_RIGHT state will result in a positive referenced ON signal being delivered to the rotational propulsion system delivering a clock-wise acceleration to the puck.

Upon the release of any joy stick movement the propulsion systems will terminate and the calculated fuel, or propulsion time remaining, will be updated for the interactive statistics provided to the user via the LCD display. The system will monitor the fuel level through iterations of the propulsion sequence until exhausted. If the fuel is exhausted before the mission is accomplished the system will exit game mode and initiate the puck return sequence. If the planet is encountered the system will initiate GAME_LEVEL_SUCCESS mode and the next level of difficulty will be presented to the user for their acceptance.

At any time during any game mode there has been no user input detected for more than 45 seconds, game mode will terminate shutting down the blower system. After 15 minutes of no user input the system will enter sleep mode. Parts required for the MCU and Software design:

4 – Switch, PB, SPST, On/Off, Red1 – LCD Display Parallel1 – Joystick1 – ARV Dragon (Software)1 – Amp 20 – Position, 2-Row Straight Breakaway Header Connector

4

EE490 Product Design

1 – AMP 40 –Position, 2-Row Straight Breakaway Header Connector1 ARES 40-Pin ZIF Socket1 – Precision Analog Microcontroller 12 Analog I/O ARM7TDMI MCU1 – Low Voltage Octal Bidirectional Transceiver16 – 47 Ω +/- 10% resistor20 - .2µF 100V 5% Capacitor8 - 10KΩ resistor +/- 5%5 – Op-Amp2 - Adapter for standard 80 pin TQFP SMD Parts2 - 20-pin SSOP Adapter2 - Versa Strip Phenolic Prototype Board1 - Stand-off Hex M/F .875" 6-32BR100 - Phillips Machine Screw 6-32-1/2100 - Washer Flat #6100 - Washer Lock Internal Teeth #6 Zinc100 - Nut Hex 6-32 Zinc2 - ATtiny24 PDIP2 - ATmega16 PDIP

Air Flow System

The Solar Sailor primary Air Flow System (AFS) shall utilize an air-hockey-like table design. The primary air chamber shall be approximately four feet in length by four feet in width by two inches in height and will be built using standard .75 inch thick hardwood (pressboard) for strength, stability, and noise/vibration isolation.

Standard four foot (sometimes a three foot is used) by eight foot air hockey tables normally operate at approximately 300-350 Cubic Feet per Minute (CFM) of air flow. There is no direct correlation between CFM and air pressure [27] However, top-of-the-line tables such as tournament play tables are rated at approximately 350-400 CFM. The best rated air-hockey tables use commercial grade blowers, although most tables operate using several high CFM fans [28].To ensure an adequate amount of air is delivered to the Solar Sailor Shuttle it was determined by the Air Flow System team that a high output centrifugal blower capable of producing a minimum 400 CFM is required. With the Solar Sailor primary air chamber less than 2.56 Cubic Feet (CF) in size (4’x4’x.16’=2.56 CF) the air chamber shall receive more than enough in-chamber air flow needed to ensure appropriate levitation of the Solar Sailor Shuttle.

The blower chosen for the Solar Sailor primary AFS is the Fasco model B45267 centrifugal blower. The Fasco B45267, Figure 6, is the lowest cost 460 CFM centrifugal blower that the Creative Design AFS team could find on the market and operates at a nominal 115 VAC, at 60 Hertz (Hz), and 2.9 Amps. [29] The AFS team compared the prices of over six dozen various centrifugal blowers before finally selection of the Fasco B45267 blower occurred.

Figure 6: Fasco model B45267 [22]

The Fasco B45267 weighs approximately nine pounds, is a two speed centrifugal blower capable of operating at 1600 or 1400 Revolutions per Minute (RPM). A noise rating for the Fasco B45267 found not be found, however most of the blowers reviewed operate between 52 and 65 dB.

Noise reduction techniques will be looked into during the project construction/testing timeframe if it is determined that the noise is significant; however reduction techniques will impact Shuttle air lift. A standard 6 feet, 18AWG computer power cable will be used to connect the Fasco blower to a standard 6 outlet 115VAC power strip.

As possible alternatives for the Fasco model B45267 centrifugal blower the AFS team looked into using either the Vortex 6” 449 CFM centrifugal fan or the A.O. Smith 9412 General Purpose Blower Motor capable of 460 CFM. The Vortex 449 CFM centrifugal fan was twice the cost of the Fasco B45267 as was the A.O. Smith (however one retailer had a closely priced model), and the A.O. Smith was a single speed blower restricting the ability of the AFS team to achieve optimum air flow on a constrained budget.

The primary AFS chamber shall have a six inch by six inch square in the middle of the primary AFS chamber separating the primary AFS from the rotating arm assembly high torque mini gear motor operating at 3-12VDC. This separation shall ensure flexibility in the design and configuration of the gear motor and rotating arm assembly. The separation shall also ensure essential power and communication between the gear motor and microcontroller is achieved.

The total size of the Solar Sailor AFS chamber layer is approximately 4.5’ length by 4.5’ width. Subtracting the primary AFS and separation wall leave approximately five inches which will be utilized by the AFS Air Return System (ARS) chamber. The ARS chamber will encompass two sides of the Solar Sailor project and will be utilized for returning the Shuttle to an initial/start position at mission time-out/reset/mission completion.

It was determined by the Air Flow System team that a high output fan system utilizing two high CFM fans capable of producing a minimum of 250 CFM shall produce enough directed air flow to sufficiently accomplish the task of repositioning the Shuttle. With the Solar Sailor ARS air chamber less than .693 Cubic Feet (CF) in size (4’x5”x5”=.693 CF) the air chamber shall receive more than

5

EE490 Product Design

enough in-chamber directed air flow required to ensure appropriate repositioning of the Solar Sailor Shuttle.

To accomplish the task of the ARS the AFS team reviewed over fifty compact DC fan designs, however the vast majority of the designs analyzed were either too large and too costly, or were unable to produce enough air flow necessary to meet the ARS objective. Luckily a small 120 mm x 120 mm x 38 mm (4.72 x 4.72 x 1.5 inch) 205 CFM fan was discovered. The ARS team chose to utilize two of the ultra-high performance Mechatronics model MD1238X fans. The Mechatronics MD1238X, Figure 7, is the most cost effective high CFM fan the ARS design team could find. The Mechatronics MD1238X achieves 205 CFM of air by revolving at 4,500 RPM using 12 VDC at 2.5 Amps [30]. The Mechatronics MD1238X weighs approximately 411g (411g is approximatelly.906lbs) and produces 62 dBA of noise. For comparison a normal conversation is typically rated at 60-70 dB, and city traffic (inside car) typically produces 85dB of noise. [31]. However this noise will be significantly diminished by the .75” hardboard and the AFS team will research ways to reduce this noise if it is determined to be significant during product construction/testing.

Figure 7: Mechatronix MD1238X Fan. [23]

As possible alternatives for the Mechatronics MD1238X fan the AFS team looked into using four COMPAQ model PSD1212PMBX, 12VDC fans capable of 105 CFM each. The other big consideration was whether to use two FFB model 1212EHE 12VDC fans rated at 190 CFM. However, the COMPAQ fans were above budget constraints and would create too much system noise and the FFB fans were twice the cost of the Mechatronics MD1238X. In order to control the Fasco B45267, 110VAC, 2.9A, centrifugal blower and Mechatronics MD1238X, 12VDC, 2.5A, fan with the microcontroller the AFS team reviewed several Single-Pole Single-Throw (SPST) relays.A relay is essentially a large mechanical switch that can be toggled off or on by energizing a coil. There are two parts to most relays, the contact and the coil. The contact part of the relay is the path in which the primary devices power travels and is either open or closed [32]. In order to control the Fasco B45267 and Mechatronics MD1238X the contact needed to be able to support at least 110VAC @ 2.9A and 12VDC at 2.5A. For safety concerns the AFS design team researched relays capable of handling at least a maximum load of 200VAC @5A and 28VDC @5A.

The coil is the second half of the relay and is basically a small electromagnet used to open/close the switch. Several relays were looked at during this part of the research phase however most relays looked at were costly and could not meet the requirements above. The microcontroller research team specified that the microcontroller would be sending a 3VDC or 5VD signal at a range from 40 – 400 mA to control the relay (using one or more pins).

In order to meet these requirements the AFS team found two inexpensive, quality, relays from suppliers (Digikey and Sparkfun) recommended by the part procurement official. The two primary relays identified by the AFS team were the Tyco T9A Series and the Panasonic DK Series shown by Figures 8 and 9 below.

Figure 8: Tyco T9A Series Relay [24]

Figure 9: Panasonic DK Series Relay [25]

The Panasonic DK1A-L2-3V-F relay (Digikey part number 255-2053-ND) has a contact rating of 10A and a maximum switching voltage of 250 VAC, 125 VDC [33]. The Panasonic DK1A-L2-3V-F relay coil requires 3VDC at 66.7mA for switching the SPST relay on and off, however the relay is four times the price of the Tyco T9A series (Sparkfun SKU: COM-00101) relay. The Tyco relay has a contact rating of 30A and a maximum switching voltage of 240 VAC, 20A @ 28VDC [34].

The Tyco relay coil requires 5VDC at 200mA for switching the SPST relay on and off and was highly recommended on several microcontroller sites. The AFS team met with the microcontroller design team and determined that the best option was to purchase 4 of the Tyco T9A relays in order to allow control of the motor arm assemble, 110VAC centrifugal blower and two 12VDC fans.

In order to provide power to the two 12 VDC fans operating at 2.5A and provide essential power for the primary microcontroller the AFS team reviewed power supplies capable of delivering all of the required output voltages, in a single package, and as cost effectively as possible. The AFS

6

EE490 Product Design

design team reasoned that a 250W computer power supply should perfectly fit the requirement.

After looking over numerous 250W power supplies the AFS design team discovered the Diablotek DA Series PSDA250 250W ATX Power Supply. The Diablotek 250W power supply accepts an input voltage of 115 VAC, 60Hz at 8A and provides Outputs of +3.3 VDC at 14A, +5 VDC at 14A, +12VDC at 10A, +12VDC at .5A, -12VDC at .5A, and +5VDC at 2A and costs around ten dollars.

The AFS design team determined that the Diablotek 250W power supply was the best option for providing the regulated DC power to all of the Solar Sailor system components.

Figure 10: Diabloteck 250W Power Supply [26]

Building of the AFS chambers will commence as soon as resources become available in order to capitalize on time and resource availability. Testing of the AFS systems will commence once the centrifugal blower, fans, and power supply are received. The 250W power supply will be the first major component tested to ensure it can produce proper out power conditions. Testing of the power supply will occur on the campus of Colorado Technical University (CTU) using CTU equipment. The relays will be the next items tested (after the microcontroller) first with a minimal contact voltage to ensure that the microcontroller is capable of providing the proper coil voltage and current for switching the DC fans on/off. Next the DC fans will be tested without the relay (one at a time) to ensure they work prior to testing after connecting the DC fans to the relays. Finally, the centrifugal blower assembly will be tested after connecting it to the standard 18AWG power cable.

A diagram of the AFS Power, communication, and air flow systems created by the AFS team is illustrated below by Figures 11 and 12.

Figure 11: Solar Sailor AFS Power, Communication, and Air Flow Block Diagram

Figure 12: Graphical representation of the Side View Solar Sailor Air Table using Visio. (See Appendix)

Air Flow System parts required for assembly:

1 - Fasco B45267 Centrifugal Blower (460 CFM)2 - Mechatronics MD1238 Fans (205 CFM each)4 – PWR Relays SPST-NO 10A 3VD1 - Diablotek DA Series 250W ATX Power Supply1 – 18 AWG Power Cable1 – 6 Outlet 110VAC Powerstrip3 - 4.5'L x 4.5'W x.75"H Hardwood boards4 - 4.5'W x 10"L x .75"H Hardwood boards4 - 4.5'W x 5"L x .75"H Hardwood boards2 - 4.5'W x 5"L x .75"H Hardwood boards4 - 1'L x 2"W x .75"H Hardwood boards2 – 18 fl. oz. bottles of Gorilla Glue (Wood)4 – 3M containers of Silicon Sealant

Spaceship Component

The Solar Flyer (Shuttle) is the physical representation of the interactive element of the system design. The item will be created from scratch using plastic resin molding techniques. Creating the play piece from scratch will allow for having direct input to the amount of mass introduced to the air table.

7

EE490 Product Design

This will make it easier to accurately simulate zero friction environment provided by the air table. The plastic resin molding process also produces a robust product that will be able to withstand the stresses of accidental collisions. The molding process will first require creating a clay positive of the spaceship. This spaceship will then be hollow molded to provide area inside the fuselage for installing the needed components. The base will be 2.5" in diameter and 1" tall. This will also be hollow molded, and will allow for electrical component storage. The fan rotors will also be cast using the plastic resin molding. The fan rotors will be 1" diameter for the fore and aft directional motors, and 1.5" diameter for the forward and reverse thrust motor in the rear. Casting these rotors will allow for adjustments to cfm to be made in relation to the power of the fan motors by adding blades or increasing and decreasing the blade angle as needed.

Figure 13: Graphic Representation of the top view of the spaceship component [12]

The spaceship will be controlled by an amplitude modulated radio frequency (RF) serial data stream from the joy stick controller by way of the main microcontroller. This signal will be input to the spaceship at the 433MHz Receiver. This receiver was chosen due to the low availability of small form low power RF receivers. The serial data stream is then decoded by the ATTiny microprocessor. Individual control signals are then sent to the Inverting Buffer IC, and subsequently used as biasing for the transistor arrays that will directly drive the motors

Figure 14: Graphic Representation of the side view of the spaceship component [13].

A circuit diagram is provided below in Figure 9.

Figure 15: Circuit Diagram, Spaceship Component [14][15] (See Appendix)

Power is provided to the mobile spaceship by way of solar cells. The fan motors are connected to a regulated 3.3V solar circuit. The max provided current of this circuit is estimated to be 80mA. This value will depend on the quality of lighting available in the environment. A safe estimate for the available current was determined to be at one half the rated output of the solar cell. The max draw of the motor circuit at any given time is 50mA [15]. The control signal flow is separated to a regulated 5V solar power supply circuit. This is done to ensure that the higher current draw of the motors will not interfere with receiving commands from the MCU. The max current provided by this circuit is estimated at 33mA, and the max current draw is estimated at 12mA [18].

The spaceship will be controlled by three small fans. Two fans will be place fore and aft of the spaceship perpendicular to the fuselage as shown in Figure 8. The two motors will be wired into the circuit inversely; if one motor is running forward, the second will be running in reverse. When the fore motor is running forward and the aft is running reverse, the spaceship will achieve a clockwise rotation. If the signal is reversed, the fore motor will be running in reverse and the aft motor will run forward, and the ship will achieve a counterclockwise rotation. These actions will allow the spaceship to point towards a desired direction. The third fan in the rear is the thrust fan. This will allow the spaceship

8

EE490 Product Design

forward and reverse movement in whichever direction it is respectively pointed.

Figure 16: Behavioral Flowchart of the Spaceship (See Appendix)

Control signals received from the MCU will follow this table:

Directional Motor ArrayInput1 Enable1 Motor

X H StandbyH L ClockwiseL L Counter-Clockwise

Thrust Motor ArrayInput 2 Enable 2 Motor

X H StandbyH L ForwardL L Reverse

Table 4: Truth Table, Motor Control Circuit [14]

The spaceship will also have a permanent magnet that will activate the proximity sensor located at home base and the Planet Driver. The magnet will be mounted on the starboard side of the spaceship in order to simulate a spaceship in orbit. The operator will need to align the magnet with the sensor and capture device to ensure a successful orbit.

Spaceship Parts required for assembly:

3 – Small Pager Motor.2 - 37 x 33mm Monocrystalline Solar Cell1 - Receiver AM Mini Hybrid 433MHZ4 - Transistor Array NPN and PNP DUAL 30V2 - Capacitor 1000uF 25V 2 - Capacitor .1uF 25V1 - L4931 5V Voltage Regulator1 - TO-92 3.3V Voltage Regulator1 - 74HC240 Enable line Invertor

1 - ATTINY24-20PU-ND 14 Pin Microcontroller1 - 1KΩ Resistor1 liter - Plastic Resin Molding Materials500g - Molding Clay2 - 2N3904 NPN Transistor

Planet Driver Component

One of the components of the Solar Sailor design is the Planet Driver. The purpose of the Planet Driver is to introduce the concept of orbits and planet trajectory in our solar system. The orbit represented in the design is a circular orbit with an eccentricity of zero. [6] The Planet Driver assembly will be controlled by the MCU which will turn the motor on/off and drive the speed of rotation using a DC gear motor. The gear motor will be capable of 8 gear speeds sufficient to model effective orbital speeds of eight planetary bodies. An LED will be displayed inside the model sun and on the planet sphere. A magnetic sensor inside the planetary sphere will allow detection of the player’s air propelled spaceship and it will transmit a signal to the microcontroller once the Solar Sailor shuttle has triggered the proximity in the planetary object. The proximity sensor will activate the transmitter inside the planet to communicate with the microcontroller. The planetary LED will flash and the LCD will inform the user once mission success is detected. A DC motor will be placed in the center of the play field under a 4” diameter hemisphere which will represent the sun. The motor’s axle will be connected to a fixed shaft in the z-direction protruding about 4 inches above the 4” diameter hemisphere (Sun). A 17 inch shaft will be connected to the main rod in the y-direction. A 2 inch plastic sphere will be attached to the secondary shaft representing the planet. The motor will move the shaft and planet around the sun with an orbit circumference of 2πr = 9.42 feet.

Figure 17: Graphical Representation of Planet Driver Component model on Autodesk Inventor

Using the circumference of 9.42 feet we can calculate the required motor velocities scaled to the Planet Driver. Assuming that one revolution equates to 10 seconds and 60 seconds equate to 1 minute. At maximum speed the motor rotates at 6 rpm.

We can use the planets (Earth days) rotations around the Sun, as the model to represent the Planet Driver revolutions. For

9

EE490 Product Design

example, Mercury has the smallest orbit, it take approximately 88 days to complete a rotation [6]. Equating Mercury’s orbital rotation at 6 rpm, we can scale the rest of the planet’s orbital speeds. The table below lists the calculated planet’s orbital speeds scaled for the planet driver.

Planet rpmMercury 6

Venus 5Earth 4Mars 3

Jupiter 0.5Saturn 0.25Uranus 0.125Neptune 0.025

Table 3: Planet Driver revolutions per minute for each planet

The sphere (planet) connected to the rotating shaft will contain a flashing LED. The LED will light up when the spaceship reach the planet. To be able to detect the spaceship the planet will also serve as a sensor. Inside the sphere a 3.6 x 5.0 x 1.0 mm [7] proximity sensor will detect the changes in the magnetic field when the spaceship has reached the planet.

The 2-Axis Magnetic sensor uses the strength and the direction of the magnetic field to measure in a range of plus or minus 2 Gauss. The sensor will transmit the signal to microcontroller and the component will stop and the game reset.

To provide power to the sensor inside the planet and the flashing LED a 37 x 33mm Mono-crystalline Solar Cell will be also attached to the planet. The sensor operates at 2.4 – 3.6 volts and the LED operated at 1.6 – 2.1 volts, the solar cell will provide 6.1 volts at 23m amps. The reason to use Solar Cells instead of consuming power from the main power supply was to eliminate wires coming out of the shafts and hence avoiding the wear and tear due to friction.

Figure 18: Proximity Sensor. HMC6042- 2-Axis Magnetic Sensor Circuit. [7]

The Planet Driver component will use a DC Motor: High Torque Mini DC Gear Motor 3-12V, 5-25 rpm. The nominal operating voltage is 6 volts with an operating voltage range of 3 – 12 volts and an operating life 8000 hours.[8] The diameter of the spindle is 7 mm and the motor is 40 mm long and 48

mm in diameter. The power will be provided by the power supply unit of the Solar Sailor Table.

The motor speed will be control using pulse-width modulation. The average value of voltage (and current) fed to the load is controlled by switching between supply and load on and off at a determined pace. [9] The speed control will be controlled by the microcontroller.

Figure 19: DC Motor: High Torque Mini DC Gear Motor. [8]

The following block diagram represents the behavior of the Planet Driver component.

Figure 20: Solar Sailor Rotating Arm Assembly.

Planet Driver Parts required for assembly:

1 - 4” diameter Plastic Hemisphere1 - 2” diameter Plastic Sphere1 - Proximity Sensor. HMC6042- 2-Axis Magnetic Sensor 1 - 37 x 33mm Mono-crystalline Solar Cell1 – TWS-434 Transmitter1 – 17 inch metal rod1 – 12 inch metal rod1 – 7 mm Universal Hub1 – LED

10

EE490 Product Design

In the process of the planet driver design some parts were eliminated or replaced. The original idea was to run wires from a PVC pipe to supply power for the components inside the planet. The problem that we encountered was the realization than when wires are constantly twisted, there is a chance for them to break creating a safety hazard. The solution is to use solar cells embeded in the planet to provide power for the electrical components inside the plant. The other issue with the design was the use of PVC pipe, which is not aesthetically pleasing. The solution was to use, thin metallic rods, which are very resistant and lighter than the PVC. An added benefit of the lighter metallic rods are in the load for the motor. The spheres use in the design, were chosen due to durability and cost, the spheres are made of plastic as opposed to metal or glass. Although there were several alternatives for the gear motor, the team decided to use the High Torque Mini DC Gear motor [8] depicted in Figure 8 due to its comparable price and efficiency.

Safety

Safety is our number one priority. Our target audience includes children 7 years and up. The design team evaluated each component of the Solar Sailor to ensure the quality of the design. The Solar Sailor design is intended for children from the age of seven years old and therefore should, by regulation, be free of sharp glass and metal edges. [35] The table structure shall be able to withstand a minimum of 200 pounds of pressure from the top Lexan surface to the side panels. The paint use for the design shall be complaint with the United States Consumer Product Safety Commission (CPSC). [35] The external structure of the IEG shall be flame retardant/ flame resistant for any fabric products. The Solar Sailor is designed as an enclosed system, with all electrical and mechanical components inside the table and only accessible by a locked panel. All small components that could be swallowed or to become lodged in a child’s windpipe are also enclosed inside the table. The Solar Sailor shall not produce noise levels greater than 50 decibels to avoid damage or hearing loss. [36] The Solar Sailor shall not have loose wires, strings or cords that could cause strangulation, electrical shock, burns or to accidentally falls. The Solar Sailor shall adhere to the CPSC regulations and meet mandatory standards for surface temperatures, electrical construction and prominent warning labels. [35] Children under the age of eight years old should use the Solar Sailor system only under adult supervision. To ensure the safety of the users, no individual is allowed to touch the internal components of the system without a thorough understanding of the electrical and mechanical components of the design.

Design Trade Offs

In the quest to deliver the best product possible, the team evaluated various design alternatives. The following section explains briefly the three major designs considered.

The first design idea was to design a pinball machine with a ball launcher (Gravity crash). Using magnets placed under the playfield and a metal ball launched in to the board. The mission was to reach each planet and gather planetary facts in the journey. The idea behind the game was to launch the ball after the player has answered correctly an astronomy question, the ball then would be released and moved to the next target. The goal of the game was for the ball to reach the intended target meanwhile the level of difficulty increase on each level.

A problem encounter with this design was the ball return mechanism. A solution suggested was to use the board inside the pinball machine as a return mechanism. After the highest target has been reached the board will tilt continuing the game and making the ball return to home base. The game required the user to have knowledge of science facts and did not serve the interactive learning experience required. In addition the playfield for the design was limited and the team decided to explore other alternatives.

The Second design purpose was to demonstrate principles of physical science and engineering through an interactive simulation. Users would propel a ball into a playing field comprised of a center point ‘sun’ and an orbiting mass, the ‘planet’. The design focus was to simulate the gravity pull of the sun and the gravity wells creative by the sun magnetic field. To simulate the time-space gravity fields the team suggested the use of a latex material. The various gravity “space-time” maps were to be simulated by varying the depths on the space time fabric according to the planet mass. The Planetary Gravity Simulator design consisted of a 6 feet by 6 feet rotating table. The player would launch a metal ball to the play field, depending on the speed and the distance reached by the metal ball, the ball will be affected by the gravitational pull of the sun or reach the planet’s orbit. The next figure is a representation of the Planetary Gravity Simulator.

11

EE490 Product Design

Figure 21: Drawing of the Planetary Gravity Simulator

The Planetary Gravity Simulator included a main controller to interface with different hardware components in the design. The main controller also controls the LCD displays and the start/reset. The design required sensors to detect the ball position in the play field.

The figure below is the MCU behavior flowchart of the MCU interface.

Figure 22 : Main Control Unit Interface (See Appendix)

One of the major constraints of the design was the rotation of the table. The team at that point decided to redesign the Interactive Educational Game.

The third idea was the Solar System Explorer; a large enclosed system, contained within a 3 ft. high, 4 ft. wide, and 8 ft. long table. The top level of the table contained a scaled model of our solar system. On the top level of the SSE a magnetically driven spaceship would navigate through the solar system by the player. The player would have been given a mission (alternating between our outer and inner planets) to visit each of the eight planetary bodies in our solar system. Each mission statement provided to the player according to the difficulty level chosen by the player. The player would have then proceeded to navigate a magnetically directed spaceship through the model solar system avoiding obstacles and incorrect planets in order to reach the planetary destination. If the spaceship reached the correct planet, the planet will light up. An LCD would have display planetary facts and then provided the player with their next planetary mission. If the player navigated to an incorrect planet, the LCD would have provided information about the current planet and then re-directed the player to the next planetary mission. The SSE

spaceship designed contained a magnet attached under it. The spaceship was designed to be controlled by a mobilized magnet underneath the model solar system. The magnet was designed to be mounted on a rover robot, with special wheels that could move freely in any direction throughout the solar system to provide the player with a more cosmic navigational experience.

Figure 23: Drawing of the Solar Explorer Design

CONCLUSION

The Creative Solutions Capstone Design Team decided to engineer and donate an educational, interactive, astronomy game to the Kennedy Imagination Center in our community. The purpose of the IEG is to teach children from the ages seven and above about the solar system and orbital mechanics. The team explored various alternatives discussed in this report. After carefully evaluating the designs tradeoffs the team decided to schedule the construction the Solar Sailor Design starting the next quarter. The most important requirement of the Solar Design is safety. All safety requirements shall be met, abiding to the CPSC regulations. All components shall be tested in accordance to our test plan before the product is released to the costumer. A risk management assessment will be included in the Final Report next quarter. As we proceed to the next phase of our design there are several lessons taken from this experience. Clear communication is a major factor in the success of any project. As a team we have learned that all changes due to the evolution of the project have to be properly identified and recorded. A solution proposed by a member of a previous

12

EE490 Product Design

Product Design team is to use the drop box software that will enable the team members to revise, change and comment on current documents. The use of the drop box software will eliminate the duplication of work. In addition, the team will implement the use of an engineering notebook to track changes, ideas and also have an accurate record of the hours worked. The weekly meetings were very successful and help us identify the strength or each of our team members. Next quarter, we will utilize the time of our weekly meetings to review changes in the design and also evaluate the impact that each change will have in the overall project. The test plan procedures are still in their infancy, a closer look to the requirements and safety concerns are to be addressed to ensure the quality and safety of the product. The schedule for next quarter has been created and a task list will be distributed after the next team meeting over the school break. One of the major constraints of this project has been time. Most of the time spent was in research, administration, and changes in the design concepts. The amount of dedication and effort to accomplish the final design cannot be measured in numbers. However, the man-hours at the completion of this report are approximately 1100 hours combined.

13

EE490 Product Design

REFERENCES

[1] n.d. The Kennedy Center. Imagination Celebration. Information Pamphlet. 1515 N Academy Blvd. Suite 200, Colorado Springs, CO 80909.

[2] Novak, J. (2005) Game Development Essentials. 2nd Edition. Cengage Learning. Information published at http://theinteractivelearningcenter.com/

[3] Halliday, D. (2001) Physics Volume I. New York New York: John Wiley & Sons.

[4] Serway, R. (2004) Physics for Scientists and Engineers. Sixth edition. Brooks/Cole.

[5] Thomas, R. (2006) The Analysis and Design of Linear Circuits. . Hoboken, NJ: John Wiley & Sons

[6] McGraw-Hill Science & Technology Dictionary, Circular Object. Retrieved from http://www.answers.com/topic/circular-orbit on March 10, 2011

[7] Honeywell Datasheet. HMC6042 2-Axis Mag Sensor Circuit .Honeywell 12001 Highway 55 Plymouth, MN 55441 Tel: 800-323-8295 www.honeywell.com/magneticsensors

[8] http://www.solarbotics.net/starting/200111_dcmotor/200111_dcmotor2.html

[9] DC Motor: High Torque Mini DC Gear Motor 3-12V, 5-25 rpm for Hobby / Robots (Batteryspace.com)

[10] Pulse-width modulation. Stemmler, H. (August 1964). "Geregelter Drehstrom-Umkehrantrieb mit gesteuertem Umrichter nach dem Unterschwingungsverfahren". BBC Mitteilungen (Brown Boveri et Cie) 51 (8/9): 555–577. Retrieved from http://en.wikipedia.org/wiki/Pulse-width_modulation

[11] Culbertson, F. (2001). Diagrams, Space Shuttle. NASA. http://history.nasa.gov/SP-4225/diagrams/shuttle/shuttle-diagram-1.htm. Retrieved 16 March 2011.

[12] Schaffran, M. (2003) Inverter Buffered H-Bridges. Solarbotics.net. Information published at http:// http://www.solarbotics.net/library/circuits/driver_buf_h.html/ Retrieved 16 March 2011.

[13] Seale, E. (2003) The "Miller" Solar Engine. Solarbotics.net. Information published at http://www.solarbotics.net/library/circuits/se_t1_mse.html. Retrieved 16 March 2011.

[14] Solarbotics. Tiny Pager Motor. http://www.solarbotics.com/products/tpm2/. Retrieved 16 March 2011

[15] STS01DTP06. (2006). Datasheet, Dual NPN-PNP complementary Bipolar Transistor. STMicroelectronics. http://www.st.com/stonline/books/pdf/docs/11404.pdf. Retrieved 16 March 2011

[16] L4931ABxx, L4931Cxx. (2008) Datasheet, Very Low Drop Voltage Regulators With Inhibit. STMicroelectronics. http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/DATASHEET/CD00000971.pdf. Retrieved 16 March 2011.

[17] 74HC240; 74HCT240. (2007). Datasheet, Octal Buffer/Line Driver; 3-State; Inverting. NXP B.V.

http://www.nxp.com/documents/data_sheet/74HC_HCT240.pdf. Retrieved 16 March 2011

[18] L4931ABxx...[19] AM-HRR30-XXX. (2004). Datasheet, Miniature AM

Super-Regen Receiver. RFSolutions Ltd. http://www.rfsolutions.co.uk/acatalog/DS014-1.pdf. Retrieved 16 March 2011.

[20] ATtiny20. (2010). Datasheet, 8-bit AVR Microcontroller with 2K Bytes In-System Programmable Flash. Atmel Corporation. http://www.atmel.com/dyn/resources/prod_documents/8235S.pdf. Retrieved 16 March 2011.

[21] Fasco model B45267 centrifugal blower. Retrieved on 14 March 2010 from the Electric Motor Warehouse website: http://www.electricmotorwarehouse.com/fasco/fasco_blower.htm

[22] Mechatronics MD1238X fan. Retrieved on 14 March 2010 from the Cooler Guys website: http://www.coolerguys.com/840556021698.html

[23] Tyco T9A Series relay. Retrieved on 15 March 2010 from the Sparkfun website: http://www.sparkfun.com/products/101

[24] Panasonic DK Series relay. Retrieved on 16 March 2010 from the Digikey website: http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=255-2053-ND

[25] Diablotek 250W Power Supply. Retrieved on 16 March 2010 from the NewEgg website: http://www.newegg.com/Product/Product.aspx?Item=N82E16817822006&nm_mc=OTC-Froogle&cm_mmc=OTC-Froogle-_-Power+Supplies-_-Diablotek-_-17822006

[26] http://wrw51.wordpress.com/2008/02/21/understanding-compressed-air-cfm-psi-force-flow/

[27] http://www.ehow.com/how-does_5347986_air-hockey-tables-work.html

[28] http://www.fasco.com/pdf/CentrifugalBlowers_2008.pdf[29] http://www.mechatronics.com/pdf/MD1238.pdf[30] http://www.gcaudio.com/resources/howtos/loudness.html[31] http://www.sparkfun.com/tutorials/119[32]http://pewa.panasonic.com/assets/pcsd/catalog/dk-catalog.pdf[33]http://www.sparkfun.com/datasheets/Components/T9A_DS.pdf[34]http://www.newegg.com/Product/Product.aspx?

Item=N82E16817822006&nm_mc=OTC-Froogle&cm_mmc=OTC-Froogle-_-Power+Supplies-_-Diablotek-_-17822006

[35] (n.d) Document #281. For Kids’ sake: Think Toy Safety from the Consumer Product Safety Commission, Office of Information and Public Affairs, 4330 East West Highway, Bethesda, MD 20814

[36] (2010) EPA Identifies Noise Levels Affecting Health and Welfare. Retrieved from: epa.gov/history/topics/noise on March 16, 2011.

14