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University of Louisiana at Lafayette Senior Design Project
Citation preview
Members: John DeBlanc Elias Ellsworth Peter Bankole Luis Chinchilla
Mentors:
Nick PughMark Fenstermaker
Satellite Communications BuoySenior Design II
Fall 2008
Outline
•Introduction
•Purpose
•Functional Specifications
•High Level Block Diagram
•Introduction to Buoy System Model
•Satellite Access Scheme
•Data Budget
•Sensor Subsystem
•Link Budget
•Communications Subsystem
•Power Budget
•Power Subsystem
•Onboard Computer
•Mechanical Subsystem
•Summary
•Acknowledgments
Introduction
•This design project will develop a satellite communications buoy.
•This buoy will communicate with a Low Earth Orbiting (LEO) CubeSat; namely, the C.A.P.E. II
•This project will combine the desirable features of satellite communications and low power requirements for future buoys and other remote applications.
Purpose
•Gather environmental data and then upload it to the C.A.P.E. II.
•Demonstrate the usefulness of CubeSats in the area of data collection and forwarding.
•Create a new arena for opportunities and applications within the CubeSat community.
•Open doors for future University of Louisiana at Lafayette senior design teams that could develop other terrestrial applications with satellite link functionality.
Functional Specifications
BuoyBuoy
Compatible Compatible
w/ Naval Academy Buoyw/ Naval Academy Buoy
On-board GPS ReceiverOn-board GPS Receiver
Memory > 100 MegabitsMemory > 100 Megabits
Data Interface (I2C)Data Interface (I2C)
Low Cost Low Cost
4) Sunlight
1) Environmental Data
2) Location
3) Time
5) Satellite Commands
Inputs
1) 145MHz and/or 435MHz Transmission Frequency
2) Sufficient Transmission Power To CloseLink With CAPE2
3) Transmit Location, Time, and Environmental Data
Outputs
Power SystemSolar/Batteries
Environment
Large Body Of WaterPotentially Harsh Weather
High Level Block Diagram
Sensors
GPS
PIC
External
Memory
Solar Cells Batteries
Power System
TNC Radio
TX TX
RX RX
Mechanical
PVC Structure
Buoy System Model
Data Budget
How much data is collected?
Comm. Budget
How much signal is needed?
Power Budget
How much poweris required?
SatelliteSatellite
Satellite Access Scheme
Beacon Buoy
“Aloha?”
Beacon "aloha" every 4 minutes.
If acknowledged by satellite,
upload weather data.
Wait 24 hours until next
satellite contact attempt.
• The buoy will measure 8 environmental variables plus GPS location and time
• If the buoy measures these variables 24 times a day, we collect about 1.4kilobytes
Data Budget
• Anemometer
• Compass
• Water Temp
• Humidity
Sensors
• Wind Vane
• Air Temp
• Pressure
• Salinity
• The wind speed would be detected using 3 cups anemometer assembly and a 0H090U Hall Effect Transistor
• The 3 cups anemometer assembly as a magnet in its center. The magnets would be used to detect the rotations of the cups.
Calculation v(m/s) = 2*pi*f ( r ) r = radius from center of shaft to center of cups. r = 0.053mm v = velocity in meters/sec
Anemometer
•The wind vane includes a 5k Dual Wiper Potentiometer which uses a 540 degree format and analog input range – 0 to 5V
• It would also include a tail and a pointer that would point in the direction of the wind. The Tail and the pointer will help rotate the potentiometer to the direction of the wind.
• A 3 Axis digital Compass (TTL) is used to orient the wind direction to its true north
Wind Vane
• Features: - Azimuth - Inclination (Pitch and Roll)
- 3 Axis magnetic sensors from Honeywell
- 3 Axis Accelerometers(G) from ST Microelectronics
- 24 bit differential Analog to Digital Converter from Analog Devices
- Four sentence formats for data parsing
- Tera Terminal software for COM
- Multiple baud rate(4800, 9600, 14400, 192000, 38400, 57600, 115200)
- Built in Temperature Sensor (-40C to 85C) for compass board
(0S500-T) 3 Axis Compass (TTL)
• A DS1621 DIP Temperature Sensor
is used to determine the air temperature sensor. It ranges from -55C to 125C and it uses I2C communication bus to communicate with a data handling system
• The DS1621 is placed inside a non- conducting epoxy for the water temperature Sensor
Air / Water Temperature Sensor
• The humidity of the air would be detected using dry and wet bulb thermometers
• The humidity is calculated based on a comparison between the wet bulb temperature and the dry bulb temperature. This method is used for some psychrometers.
Humidity Sensor
•The MPX4115AP Pressure Sensor would be used to measure air pressure. It ranges from 15 to 115kpa
• A 0.17 ID, 0.25 OD POLYETH TUBE would used as an atmospheric vent
Pressure Sensor
•Requires two electrodes mounted inside PVC
• Uses IRF7831 MOSFET Switch to turn on sensors
• MAX4372 Op. Amplifier for voltage
• Output: 0 to 5v range for ADC conversion
• The salinity would be determined by finding a relationship between the voltages and salinity through a graph. A mathematical formula would be derived from the graph because the voltages are proportional to the salinity
Salinity Sensor
Link Budget
Communications – Link Testing
¼ Wave Antenna – 6W TX Power
Naval Academy LEO PCSAT
Antenna Polarization
Low power 3V Radio
Handheld Radio
Picopacket TNC-X
Communications - Radio
Power Budget
•How did we go about designing the Power Subsystem?
Total System Power Units Amount
Total Onboard Computer Power PER DAY Watt-hours 0.3685176
Total Communication Power PER DAY Watt-hours 3.7863978
Total GPS Power PER DAY Watt-Hours 0.48
Total Sensor Power PER DAY Watt-Hours 0.1277
General System Power PER DAY Watt-hours 4.7626154
Power – Power Subsystem
•Batteries vs. Solar Panels + Batteries:
•Batteries have a limited lifetime.
•Solar panels will provide a longer lifetime to batteries to satisfy the buoy’s power needs.
•Sealed Lead Acid Battery
•Poor weight-to-energy density
•Inexpensive
•Low-self discharge
•Multiple Solar Panels
•Collect as much sunlight as possible
Power – Experiments
•Peak Power Point
•Use solar panels efficiently
•Different Peak Power Points
•Generic vs. Atlantic
•Which one is better?
Generic Atlantic
Power – Experiments
Generic Atlantic
Typical Voltage Volts 14.75
Typical Current Amps 0.09499
Typical Power Watts 1.40110
Time In Sun Per Day Hours 3.3
Power Per Day / Panel 1 (Direct Sunlight) AH 0.313467
Power Per Day / Panel 1 (Direct Sunlight) WH 4.62363825
Indirect Sunlight Percentage % 20.00%
Power Per Day / Panel 2 (Indirect Sunlight) AH 0.0626934
Power Per Day / Panel 2 (Indirect Sunlight) WH 0.92472765
Indirect Sunlight Percentage % 20.00%
Power Per Day / Panel 3 (Indirect Sunlight) AH 0.0626934
Power Per Day / Panel 3 (Indirect Sunlight) WH 0.92472765
Indirect Sunlight Percentage % 10.00%
Power Per Day / Panel 4 (Indirect Sunlight) AH 0.0313467
Power Per Day / Panel 4 (Indirect Sunlight) WH 0.462363825
Total Power Generated Per Day (Amp-hours) AH 0.362054385
Total Power Generated Per Day (Watt-hours) WH 5.340302179
Typical Voltage Volts 12.65
Typical Current Amps 0.06235
Typical Power Watts 0.78873
Time In Sun Per Day Hours 3.3
Power Per Day / Panel 1 (Direct Sunlight) AH 0.205755
Power Per Day / Panel 1 (Direct Sunlight) WH 2.60280075
Indirect Sunlight Percentage % 20.00%
Power Per Day / Panel 2 (Indirect Sunlight) AH 0.041151
Power Per Day / Panel 2 (Indirect Sunlight) WH 0.52056015
Indirect Sunlight Percentage % 20.00%
Power Per Day / Panel 3 (Indirect Sunlight) AH 0.041151
Power Per Day / Panel 3 (Indirect Sunlight) WH 0.52056015
Indirect Sunlight Percentage % 10.00%
Power Per Day / Panel 4 (Indirect Sunlight) AH 0.0205755
Power Per Day / Panel 4 (Indirect Sunlight) WH 0.260280075
Total Power Generated Per Day (Amp-hours) AH 0.237647025
Total Power Generated Per Day (Watt-hours) WH 3.006234866
Power – Regulating Power
Step-down voltage : 12 V to 5 VLinear Regulator vs. Switching Regulators:
-Linear:- Take the difference between input and output voltages.
-Difference voltage is converted into thermal energy Wasted as heat-Efficiencies: 14% to 40%
-Switching:-Takes small amounts of energy from input voltage and moves it to output.
-Relatively small energy loss.-Efficiencies: 70% to 85%
-Conclusion:-Switching Regulator Efficiency > Linear Regulator Efficiency.
Power – System Features
-Controlled Solar Charging
-Prevent solar panels from overcharging batteries
-Using a MOSFET as a switch between solar panels and batteries
-Microcontroller will open / close switch depending on battery charge
-Control Other Subsystem’s Power
- Some components will not be used all the time.
- Use of MOSFETs as switches to selectively power buoy components
-Watchdog Timer
-Resets the Microcontroller
-Momentarily cuts the power to the Microcontroller and Subsystems
-Reset a latch up condition
DG
Solar Panel
S
Battery
Power – Final Calculations
Total System Power Units Amount
General System Power PER DAY Watt-hours 4.7626154
Solar Power Harnessed PER DAY Watt-hours 5.340302179
Surplus Power From Sun Watt-hours 0.577686779
•Despite conservative assumptions about sunshine per day and
system inefficiencies this power system design exceeds the buoy's
power requirements.
Onboard Computer
Coordinating the Subsystems
Sensors
Power
Comm
Satellite CommunicationsWeather Buoy
The Buoy State Machine
WaitShort
GetData
Aloha
DataTx
WaitLong
Finished TX
Data Gathering State
Fetch current data from the environmental sensors and GPS
- struct ENVIRONS* GetEnvirons();Pressure(kPa), Humidity(%), Air Temperature(degrees),
Water Temperature(degrees), Salinity(mg/L), Wind Speed(mph), and Wind Direction(N,S,W,E,NE,NW,SE,SW)
-struct GPS* GetGPS();Time, Longitude, and Latitude
Store Data On I2C EEPROM
Aloha State
Attempt to contact satellite
Acknowledged Not Acknowledged
WaitShortData
TxAcknowledged
Data Tx State
Upload environmental data to satellite
[Buoy Address],[Date],[Time],[Latitude],[Longitude],A[Air Temperature],W[Water Temperature],H[Humidity],WS[Wind Speed],WD[Wind Direction],S[Salinity]
03,101809,053021.32,2501.23.N,9002.18.W,A088,W084,H060,WS015,WDNW,S32
WaitLong
Finished TX
Wait Short State
Waiting between data gathering and alohas
60 Minutes 4 Minutes
Aloha4 Minutes PassedGetData
60 Minutes Passed
Wait Long State
Waiting while accumulating a 24 hour data set
60 Minutes
GetData
60 Minutes Passed WaitShort
24 Hours Passed
24 Hours
Power Management State
Disable Solar Charging
EnableSolar Charging
Low Power Mode
Cease ActivityUntil Voltage >= 12.4
100% Charge 80% Charge 30% Charge
Regulate System Voltage
Mechanical - Construction
Bending PVC for Solar Panel MountsFinal Result
Mechanical
Antenna
Solar Panels
3 ft Discus
Aluminum Struts
Payload
Mechanical - Stability Test
Insert VideoHere
Sensors Physical Mount
Summary
FuncSpecs
FunctionalBlock
Diagram
SatAccessScheme
BuoySystemModel
+ -DesignChoices
DataBudget
LinkBudget
PowerBudget
Onboard Computer
CommSubsystem
PowerSubsystem
SensorsSubsystem
Mechanical
Acknowledgements
•Special Thanks to:
•Nick Pugh
•Mark Fenstermaker
•Fenstermaker and Associates
•Dr. Zhongqi Pan
Questions?
Appendix
•Satellite Data Transmission
•Salinity Testing Schematic
•Power Subsystem Schematic
•Sensors Subsystem Schematic
•Main Board Schematic
•Angle of Incidence
•Buoy System Model Spreadsheet
•Communication Subsystem Schematic
•TNC - X Schematic