Wireless TPS Sensors

Chris Johnson

Jesse Pentzer

Brandy Holmes

John Sochacki

Lucus Wells

Slide #2Outline

Background Needs/Specs Designs

Design 1 Design 2 Design 3

Trade Study Sensors Budget Schedule Challenges Conclusion Acknowledgments

Slide #3Background

The re-entry environment is extremely difficult to model.

NASA Ames desires a wireless sensor system that can be integrated into the Thermal Protection System (TPS) of entry vehicles.

Complications with adding extra wiring and the risk involved in adding sensors to the mission.

A wireless sensor system would remove wiring complexities, reduce mass, and reduce risk associated with cable cutting.

With a greater understanding of the environment encountered during atmospheric re-entry the TPS of future missions could be made safer and more efficient.

Slide #4Needs/Specifications

Need Specification Target Value Unit

Multi-Nodal Wireless Architecture 1) Number of Nodes Architecture can Support 10

Multiple Sensors per Node 2) Number of Sensors per Node 5

Multiple Sensor Types per Node 3) Minimum Number of Different Sensors Per Node >= 2

Integration with Rise Balloon 4) Maximum Size 4 x 5 x 0.5 inches

  5) Maximum Weight 16 ounces

6) Sensor Pressure 0 to 14 psi

  7) Minimum Sensor Temperature -60 °C

X-Jet Testing 8) Maximum Sensor Temperature 1000 °C

9) Wireless Signal Range 10 meters

  10) A to D Resolution 10 bits

  11) Maximum Electronics Temperature 125 °C

Slide #5Design One

Sensor Node 1

Sensor Node 2

Sensor Node 3

Receive Node

Sensor

Sensor

Sensor

Sensor

Sensor

Sensor

Sensor

Sensor

Sensor

Wire

Wire

Wire

WireWire

Wire

Wire

Wire

Wire

RF Wireless Link

RF Wireless Link

RF Wireless Link

Design #1 & #3

Po

we

r F

low

Sig

na

l F

low

Thermocouples

RTD Network

Pressure Sensor

Cold Junction

Correction Chip

Amplification

PICMicro-

processorBuffer XBee

Sensor Node

Li Ion 7.4V

Battery

Battery Protection

Circuit

5V LDO Regulator

5V LDO Regulator

5V LDO Regulator

3.3V LDO Regulator

PIC Micro-processor

RTD Network

Buffer Pressure Sensor

Cold Junction Correction

ChipAmplification

XBee

UART

UART

I2C

Analog

Analog Analog UART Wireless

7.4V 7.4V

5V

5V

5V 5V

5V

5V

3.3V

Receiver

Slide #6Design One

Design #1, #2, & #3

Pow

er

Flo

wS

igna

l Flo

w

Receiving Node

Transmitter

XBee Pro

Reciever

Rabbit Micro-processor

Data Acquisition

Li Ion 7.4V

Battery

Battery ProtectionCircuitry 3.3V LDO

Voltage Regulator

3.3V LDO Voltage

RegulatorXBee

Rabbit Microprocessor

Slide #7Design Two

Design #1, #2, & #3

Po

we

r F

low

Sig

na

l F

low

Receiving Node

Transmitter

XBee Pro

Reciever

Rabbit Micro-processor

Data Acquisition

Li Ion 7.4V

Battery

Battery ProtectionCircuitry 3.3V LDO

Voltage Regulator

3.3V LDO Voltage

RegulatorXBee

Rabbit Microprocessor

Sensor Node 1

Sensor Node 2

Sensor Node 3

Sensor

Sensor

Sensor

Sensor

Sensor

Sensor

Sensor

Sensor

Sensor

Wire

Wire

Wire

WireWire

Wire

Wire

Wire

Wire

Wire

Wire

Wire

Transmit Node

Receive Node

RF Wireless Link

Slide #8Design Two

Design #2 & #3

Sig

na

l F

low

Po

we

r F

low

Analog

7.4V 5V

UART

Pressure Sensor

RTD Network

UART

PICMicro-

processor

Cold Junction Correction

Chip

Li Ion 7.4V

Battery

5V LDO Regulator

PIC Micro-processor

Battery Protection

Circuit

Thermocouples

I2C

Analog

5V

5V5V LDO

Regulator7.4VPressure Sensor

5V

Buffer

Amplification

Analog

RTD Network

Sensor Node

Cold Junction Correction Chip

5V LDO Regulator

5V5V Amplification

Transmit Node

Design #2 & #3

Po

we

r F

low

Sig

na

l F

low

3.3V LDO Regulator

Rabbit Micro-controller

UART or I2C

Wireless

UART of I2C

UART

3.3V

UART

5V LDO Regulator

7.4V

Transmit Node

XBeeLi Ion 7.4V

Battery

XBee

Receiver

5V

5V LDO Regulator

Rabbit Micro-controller

7.4V

Battery Protection

Circuit

5V

UART

Sensor Node

Slide #9Design Three

Sensor Node 1

Sensor Node 2

Sensor Node 3

Sensor

Sensor

Sensor

Sensor

Sensor

Sensor

Sensor

Sensor

Sensor

Wire

Wire

Wire

WireWire

Wire

Wire

Wire

Wire

Wire

Wire

Wire

Transmit Node

Receive Node

RF Wireless Link

Sensor Node

Sensor Sensor

Sensor

RF Wireless Link

Design #1, #2, & #3

Po

we

r F

low

Sig

na

l F

low

Receiving Node

Transmitter

XBee Pro

Reciever

Rabbit Micro-processor

Data Acquisition

Li Ion 7.4V

Battery

Battery ProtectionCircuitry 3.3V LDO

Voltage Regulator

3.3V LDO Voltage

RegulatorXBee

Rabbit Microprocessor

Slide #10Design Three

Design #2 & #3

Sig

na

l F

low

Po

we

r F

low

Analog

7.4V 5V

UART

Pressure Sensor

RTD Network

UART

PICMicro-

processor

Cold Junction Correction

Chip

Li Ion 7.4V

Battery

5V LDO Regulator

PIC Micro-processor

Battery Protection

Circuit

Thermocouples

I2C

Analog

5V

5V5V LDO

Regulator7.4VPressure Sensor

5V

Buffer

Amplification

Analog

RTD Network

Sensor Node

Cold Junction Correction Chip

5V LDO Regulator

5V5V Amplification

Transmit Node

Design #1 & #3

Po

we

r F

low

Sig

na

l F

low

Thermocouples

RTD Network

Pressure Sensor

Cold Junction

Correction Chip

Amplification

PICMicro-

processorBuffer XBee

Sensor Node

Li Ion 7.4V

Battery

Battery Protection

Circuit

5V LDO Regulator

5V LDO Regulator

5V LDO Regulator

3.3V LDO Regulator

PIC Micro-processor

RTD Network

Buffer Pressure Sensor

Cold Junction Correction

ChipAmplification

XBee

UART

UART

I2C

Analog

Analog Analog UART Wireless

7.4V 7.4V

5V

5V

5V 5V

5V

5V

3.3V

Receiver

Slide #11Design Three

Design #2 & #3

Pow

er

Flo

wS

igna

l Flo

w

3.3V LDO Regulator

Rabbit Micro-controller

UART or I2C

Wireless

UART of I2C

UART

3.3V

UART

5V LDO Regulator

7.4V

Transmit Node

XBeeLi Ion 7.4V

Battery

XBee

Receiver

5V

5V LDO Regulator

Rabbit Micro-controller

7.4V

Battery Protection

Circuit

5V

UART

Sensor Node

Slide #12Trade Study

Value of Designs (1-3)

Item Design 1 Design 2 Design 3 Comments

Low Cost 1 3 2 all will meet budget

Small Size 3 1 2 node size minimized

Low Weight 3 1 2 low impact on VAST balloon

Low Software Complexity 2 3 1

Low Hardware Complexity 3 1 2

Low Power Consumption 1 3 2

Meets additional Priorities 2 3 1 priorities besides #1's

Low Packaging Complexity 3 2 1 protective packaging only

High Usability 2 1 3 includes versatility

Feasibility 3 2 1

Summation 23 20 17 This total would suggest that the completely wireless option has the most benefits

Slide #13Sensors

Omega Type K Thermocouples with Glass Braid Insulation Range: -270 to 1372 °C Uncertainty: Greater of 2.2 °C or 0.75% Cost: $33 for five thermocouples with one meter leads

Honeywell ASDX-DO Series Pressure Sensors

Range: 0 to 30 psi absolute Uncertainty: 2.0% Full Scale Temperature Range: -20 to 105 °C Cost: $33.27 Each

Omega Thin Film Resistance Thermal Detectors Range: -70 to 500 °C Uncertainty: Dependent on Calibration Equation Cost: $47.50 for pack of five

Slide #14Budget

• Common Cost to all designs: $679.16 • Design One

• 9 PCB’s• 9 Batteries• 9 X-Bee chips

• Total Cost: $1333.91 • Design Two

• 11 PCB’s• 3 Batteries• 3 X-Bee’s 

• Total Cost: $1137.41 • Design Three

• 11 PCB’s• 5 Batteries• 5 X-Bee’s

• Total Cost: $1222.91

• Thermal Exposure’s Budget: $2240

Slide #15Schedule

Slide #16Challenges

Code Complexity RF Opaque Materials Design Packaging for

Harsh Landing Conditions

Thermal Protection of Circuit

Slide #17Conclusions

Thermal Exposure’s Favorite? Design One!!!

Why? Versatility Simplicity of Code Simplicity of Design Small Size and Weight

Slide #18Acknowledgments

Faculty Advisors David Atkinson Steve Beyerlein

Mentors Greg Swanson Tye Reid Justin Schlee

NASA Ames David Hash Johnny Fu Ed Martinez

Slide #19

Questions?