Team Ram-Rod Helios Conceptual Design Review. Aaron Gardiner Tyler Murphy Vivian Phinney Farheen Rizvi Ali Toltz

Transcription

1 Team Ram-Rod Helios Conceptual Design Review Aaron Gardiner Tyler Murphy Vivian Phinney Farheen Rizvi Ali Toltz March 23, 2006

2 Mission Overview Helios will be developed in order to test the effectiveness of two different brands of sunscreen (same SPF) when exposed to ultraviolet radiation. Helios intends to discover the relationship between altitude and light intensity. Helios will use pressure data from a barometric switch to determine ascent and decent rates

3 Functional Block Diagram 9v. Power Supply Ultraviolet Filter UG11 Fused Silica Switch 4 Barometric Switch Internal Temp. Sensor External Temp. Cable 12v. Power Supply Switch 1 27v. Power Supply Sunscreen Ultraviolet Filter OG515 Photodiode Mirror Camera Humidity Sensor Epoxy Board Amplifier Circuit HOBO U Timer 1 Spring Activated Bi-Stable Mechanism HOBO 2 Optical Interrupter Circuit Switch 2 Switch 3 Heater Foam Core 555 timer 2 Experiment Picture Protection Measurements Memory

4 Subsystem Interaction Balloon Satellite Structure C And DH Power Experiment Module Electronics house satellite components HOBOs + circuitry + experiment motor + circuitry + baroswitch rotating disk + filters optical interrupter w/ type-d flip-flop + transimpedance amplifier circuit Window for experiment + voltage divider (Baroswitch) circuit Support bi-stable Mechanism for camera

5 Expected Results Baro Switch Will measure data for use in calculating assent and decent rates. Amplifier circuit Will convert current from photo diodes DC voltage. Camera Will take pictures of the Earth and the balloon during flight. HOBO Data Loggers Will record voltages from amp. circuit and the baro switch during the duration of the flight.

6 Experiment Helios Sunlight falls on fused silica and sunscreen system Absorption occurs Light falls on UG11 UV filter Photons from the filtered light are detected by photodiodes Model of Experiment

7 Experiment Helios Contd. Photodiode produces varying current proportional to the amount of photons detected Varying current sent to amplifier circuit affects DC voltage output This voltage is then sent to the HOBO data logger Model of Experiment

8 Filter Selection UG11 Filter Wavelength of UV light: nm Allows Red Leak to pass through use another filter to discard its affect on the amount of light falling on the photodiode UG11 Filter Performance under Light Exposure 1 OG515 filter UG11 filter

9 Photodiode Selection S blue enhanced photodiode Range: 1.2 Amps/Watt 1.8 Amps/Watt Performance of S Photodiode under light 1

10 Rotating disk: Rotating Motor 4-Speed Crank Axle Gearbox Low speed and high torque Two brands of sunscreen Red leak OG515 filter Only allows red leak to pass Subtract its affect from results Black (aluminum) No light passes through No signal sent to HOBO Indicator of one complete rotation Easier to calibrate data Fused Silica Blank All light should pass through Accounts for any light absorption by fused silica Model of Experiment Rotating Disk Model

11 Optical Interrupter Circuit Motor will be running open looped, so optical interrupter circuit will be used to determine the rotation frequency of the epoxy board Optical interrupter circuit consists of an LED that interacts with a phototransistor We will add a Type-D flip flop chip to force the output to consistently alternate between logical high and logical low each rotation 5.0 PCB Photointeroptic slot 74HCT273 Octal D-Type Flip-Flop Instead of remaining on logical low and outputting an extremely short logical high when it reaches the hole in epoxy board By knowing the frequency of the rotation, we can later determine what output corresponds to a particular sample on the Epoxy Board

12 Transimpedance Amplifier Circuits Transimpedance Amplifier Circuit will convert current to voltage, employing the concept of Zero Bias R feedback R feedback will convert V out back into current, but of opposite sign of I Input One benefit of this is almost complete elimination of leakage current. P.D. - + A Our Amplifier Circuit V out V out is fed to the HOBO data logger as a slowly varying DC voltage

13 Barometric Switch Wiper OFF a contact - infinite resistance, therefore sends an output of 0 V Wiper ON a contact - low resistance, therefore sends an output of approximately 9 V Bellows expands as pressure changes Wiper arm moves as change in pressure expands the bellow The wiper arm hits contacts which are laid out in a serpentine pattern

14 Barometric Switch Voltage Divider U HOBO has constraint on maximum input voltage of 2.5V HOBO should recognize the logical high and logical low output of the Barometric Switch as 2.5V and 0V We determined value of the resistors that would provide a ¾ voltage drop before V out : Circuit V out = R2 R1+R2 * V IN 2.25v = 10k 10k + 27k * 9v

15 Barometric Switch Contd. Each contact on Baro Switch corresponds to a pressure calibration chart with values for pressure These charts are unique to each Baro Switch Utilize the Ideal Gas Law to calculate the air density D = P / (T*R) where R is the gas constant for air = 287 (J/kg*K) According to the Hydrostatic Equation, the change in pressure with the change in height is equal to the average density of the air times the gravitational constant dp/dz = - density * gravity

16 Bi-Stable Mechanism Will control the release of the mirror mechanism. Will be constructed with a mouse trap connected to the mirror and a solenoid. The solenoid will be used to release the trap at the correct time to take photos of the balloon.

17 Mass and Dimensions Mass Component Dimensions mm. g. Cost $ Component Dimensions mm. Mass g. Cost $ Canon Elph Lt Camera Provided by instructor Light sensors circuit board Timing Circuit x Provided by instructor Baroswitch Provided by Dr. Harder LASP HOBO H Provided by instructor Foam core Provided by instructor HOBO U12 & Software $190 Glue N/A N/ A N/A 15 Provided by instructor Alkaline battery x Provided by instructor Tape N/A N/ A N/A 20 Provided by instructor Battery Holder 9v battery x3 9v battery connector Heater UV filter N/A N/A N/A Provided by instructor Provided by instructor Provided by instructor Provided by instructor Provided by Dr. Harder LASP Aluminum tube (OD,ID,L) Wire Mirror Miscellaneous Hardware 5.59 N/A 5.0 N/A N/ A N/ A N/A 50.0 N/A Sample Plates Provided by Dr. Harder LASP Mass Budget g Mounting Plate $5.00 Cost Budget $254 Motors Free provided by ITLL Light sensors Provided by Dr. Harder LASP

18 Structure Diagram

19 References 1) Data is from SIMS (Spectral Irradiance Monitor) SOLSPEC instrument with the resolution filtered to 1 nm

20 Appendix I: Feedback Resistor Determine from plot 1 wavelength at maximum filter transmission (320 nm, 80%) Full Width Half Maximum (FWHM) of UG11 filter Determine from plot 2 Irradiance (watts/m 2 nm) Consider 80% Irradiance reaching photodiode due to absorption by UG11 filter Not looking at direct sun Irradiance intensity is 100 times less Actual Irradiance = 0.008*Irradiance Plot 1: UG11 filter performance under exposure Plot 2: Solar Irradiance 1

21 Appendix I: Feedback Resistor Determine area of photodiode (4.1 mm diameter) Calculate number of watt falling on the photodiodes from area and FWHM Compute amount of current produced per watt from plot 3 Calculate the value of resistor (in Ω) from V = IR Plot 3: S Photodiode Performance under light

22 Appendix II: Red Leak Plot 4 presents the performance of the OG515 filter when exposed to light. Filter allows all wavelengths greater than 500 nm to pass through blocks UV subtract affects of light on the photodiodes other than those of UV Plot 4: OG515 red leak filter performance under light 1