Transcript Technical Presentation PowerPoint

Wireless System for TPS
Sensors
Presented By:
Tye Reid and Greg Swanson
Outline
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Introduction
Motivation
Project Challenges
Prototype
Prototype Specs
Calibration
Testing
Results
Conclusion
Introduction
Forward Bay Cover
• Goal – to design and
Backshell
build a wireless
system to transmit
data gathered from
sensors embedded Pressure Vessel
into the TPS of
atmospheric entry
probes.
Thermal Protection
System (TPS)
Motivation
• Reduction in Complexity (eliminates
harnesses, wire routes, and wire holders)
• Easier and Safer Implementation (routing
through safety barriers isn’t needed)
• Improved assembly efficiency
• Weight Savings
Project Challenges
• Transmission through RF nontransparent material
• Transmission through high interference
environment
• Thermal protection of wires and circuits
• Size requirements associated with space
flight
Prototype
• Zigbee RF transmitters chosen for their
low power/bandwidth design
• Thermocouple voltage to temperature
conversion chips for embedded
thermocouple sensor readings
• Optimized PCB layout to minimize EMI
• Different antennas for signal strength
testing
Prototype Specs
Transmission Type
Radio Frequency
Data Rate
4 Hz
Data Transfer
Real Time
Power Source
2 AA
System Life Power
8 days constant transmission
Temperature Resolution
+/- 1% readout
Temperature Range
0 – 1128 degrees Celsius
Transmitter Size
3 ¼” x 2 ¾” x ¾”
Weight
3.2 oz
Calibration
• +/- 1.2% Temperature Error
• Error sources
– Thermocouple voltage to
temperature conversion
chip has a +/- 3 degree C
error
– Thermal Differences
between the thermocouple
to circuit connection and
conversion Chip
1.4
1.2
1
% Error
– Program rounds off
decimals and converts to
degrees F
% Error for Range of Temperatures
0.8
0.6
0.4
0.2
0
-0.2 0
500
1000
Temperature (F)
1500
2000
Testing
• X-Jet at NASA Ames
– Testing for transmission out
of x-jet chamber
– Antenna testing
– Distance tests
– Precision and Accuracy tests
Results
• Clear
transmissions out
of test
environment
• Temperature data
matched rough
analytical analysis
• Repeatable Data
• Small PCB
antenna worked
just as well as
larger antenna
Conclusions
• Zigbee RF technology demonstrates a
solution to wiring problems
• Integrated sleep mode design would allow
for 8 years of operation off of 2 AA batteries
• Initial prototype weighs 0.2 lb reducing
sensor system weight by 50%
• Miniaturization and further development is
recommended
• Next step will be to implement sensors on a
probe flight such as the RISE program
balloon