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P14372 Actively Stabilized Hand-Held Laser Pointer. Kaitlin Peranski Spencer Wasilewski Kyle Jensen Kyle Lasher Jeremy Berke Chris Caporale. Agenda. Problem Definition Review Executive Summary System Review Detailed Design Review Detailed Risk Assessment Test Plans
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P14372 Actively Stabilized Hand-Held Laser Pointer Kaitlin Peranski Spencer Wasilewski Kyle Jensen Kyle Lasher Jeremy Berke Chris Caporale
Agenda • Problem Definition Review • Executive Summary • System Review • Detailed Design Review • Detailed Risk Assessment • Test Plans • Bill of Materials • Cost Analysis • Project Plan for MSD II
Problem Definition • There are many people today who use laser for various applications: to aid in presentations, medical imaging, and defense. Under many use scenarios they are negatively affected by unwanted vibrations; one such example is a nervous presenter using a laser pointer. New Scale Technologies (NST) has developed a module that steers a laser beam using piezoelectrics and mirrors. Currently they cannot actively detect and compensate for hand vibrations. To reduce this gap, a handheld and user friendly unit is to be developed utilizing the NST module. Concerns for development include: response time, operating temperature and duration, and unwanted motion attenuation.
Customer Needs Engineering Requirements
Executive Summary • Target Frequency Range: 1-20 Hz • Cost Analysis: Total < $350 • Test Bench Design: < $100 • Response Time Analysis: • Required = 12.5 ms • Capability = 10 ms (worst case) • Power Consumption: 1.4Watts • Heat Generation: Surface temperature of 95o F • Comparison of Gyroscopes and Accelerometers: Beyond 80 cm, gyroscopes are more accurate • Housing: Aluminum, 139X42X32 mm
Concept Selection Concept 1 Concept 2 Battery Accelerometer Integrator/Low Pass Filter Processor Communication to NST • Battery • Gyroscope • Low Pass Filter • Processor • Communication to NST Module
Required Response Time • Highest hand jitter frequency = 20 Hz • Sample rate = 4*frequency = 80 Hz = .0125 sec • Required time = .0125 sec or 12.5 ms to accurately reduce vibrations
Response Time Breakdown • NST • Data Acquisition • Software Interpretation and Control • Communication to NST
Response Time Measurements Zoomed to Zero (Delay) Total Time
Total Response Time • NST ~ 2 ms (worst case scenario) • Data Acquisition ~ 2 ms • Software Interpretation and Control ~ 2-5 ms • Communication to NST ~ .2 ms • Total Time = 9.9 to 10 ms • Gives 2.5 ms of overhead
Agenda • Detailed Design Review • Schematic Drawings • Control Algorithm • Thermal Resistance Analysis • Device Housing/Layout • Test Bench Design
Gyroscope • InvenSense ITG-3200 • Sample Rate: 8kHz • Operating Current: 6.5mA • Operating Voltage: 3.3V • Full Scale Range: 2000°/s • Fast Mode 400kHz I2C Interface • Simple breakout board with mounting holes
Battery • UnionFortune 063450 Cells • 1000mAh LiPo • 2 cells in parallel for 2000mAh total • Battery life close to 4 hours • -25°C to 60°C Operating Temperature • Nominal Voltage: 3.7V • Maximum Current: 1A (wire limited)
Processor • SparkFunArduinoFio v3 • 8MHz Clock • 16 Digital I/Os • 6 Analog I/Os • 150mA Current Draw • Built in 3.3v regulator and LiPo charger • Built in switch • I2C, SPI, USB compatible
Sample Input (f = 1 Hz) Green is input, Red is output
Control Algorithm Poll Gyro For Data (I2C) Acc = 0 Subtract Gyro Data From Accumulator Wait Acc > 15? Re-Center NST Module Acc < -15? Compute Encoder Counts Send to NST Module
Simulated Jump (Bound Crossing) Delay = .1s
Simulated Jump (Bound Crossing) Delay = .5 s
Thermal Resistance Analysis • Surface temperature of housing • Assuming hand insulating half the surface and =68°F
Thermal Resistance Analysis • Assuming TC1=TC2=TC
Thermal Resistance Conclusions • Top surface = 96 • Bottom surface (surface with hand) = 97 • Temperature at surface of chip = 117