Wireless TPS SensorsDetailed Design Review

February 12, 2008

Jesse PentzerJohn SochackiBrandy HolmesChris JohnsonLucas Wells

2

Outline• Introduction• PCB• Sensor Node Software• Receiver Node Software• X-Jet Packaging• VAST Packaging• Timeline• Budget

PIC XBee

Amplifier

LDO Regulator

LDO Regulator

LDO Regulator

CJCs

Pressure Sensor

Pressure

CJC CJC CJC

XBee

LDO

LDO

LD

O

Amp

RTD

Newest Revision Air-wires will be resolved through testing

Final ConceptP

ow

er

Flo

wS

ignal F

low

Thermocouples

RTD Network

Pressure Sensor

Cold Junction

Correction Chip

Amplification

PICMicro-

processorXBee

Transmit 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

Pressure Sensor

Cold Junction Correction

ChipAmplification

XBee

UART

UART

I2C

Analog

Analog Analog Wireless

7.4V 7.4V

5V

5V

5V 5V

5V

3.3V

Receiver

Final Concept

Final ConceptP

ower

Flo

wS

igna

l Flo

w

Receiving Node

Reciever

XBee Pro

Reciever

Rabbit 4000 Microprocessor

Data Acquisition

12 Volt Battery

Battery Protection

and Regulation

Xbee Pro/ Rabbit 4000

Board

Final Concept

Software Flow Sensor Node• Poll of Sensors

– I2C (pressure sensor)– A/D (RTD temp. sensor)– SPI (3 thermocouple temp. sensor)

• Communication– USART (XBEE transceiver)

• Data Structure Union with Array

– Redundant Send

Error Reduction• Program Lockups

– Conditional Locked Loops– Watchdog Timer (WDT)

• Data Reliability– Redundant Data

• Use PIC EEPROM to store old sensor data

– Data Comparison

Error Reduction Cont’d• Code Protection

• Power Problems– Brown-Out Reset (BOR)

Rabbit RCM 4510W

Receiver Node Data Flow

X-bee Receives

DataRabbit 4000

Serial Communications

RS-232

Data Added to Data

Structure

Data Taken from Data

Structure and Sent to Serial

Port

Serial Port Sends Data Stream to Laptop’s

Serial Port

Laptop Receives Data from

Rabbit

Data Read from Serial

Port by LabVIEW

LabVIEW Sends Data to

File and Graphs Data

LabVIEW Interface

• Communications Parameters

• Thermal Coupler graph

• Pressure graph• RTD graph• Data Storage in File

Configure Serial Port

Set Termination Character

Read Data for buffer

Write data to serial port

Set XON and XOFF

Characters

Set I/O Buffer Size

Write Data to File

Display Data on Graph

LabVIEW Logic Diagram

Communication Parameters(user input)

Close Session

16

X-Jet Preparation

• Using an aluminum sheet metal box to house electronics.

• Discs of TPS material allow thermocouples to measure temperature along a centerline through block.

• Static tube allows pressure measurement inside X-Jet

17

X-Jet Preparation - Progress

18

• Assumptions:– TPS properties constant– 1-D heat transfer along

centerline of TPS

010 **21*

**2 TFoTk

qxFoT

Thermal X-Jet Model

Heat Flux Node:

Interior Node:

nnnn TFoTTFoT **21* 11

Convection Node:

1010910 ***

1***

* Tk

xhFo

k

TxhFoTTFoT

2**

*

xc

tkFo

p

19

Thermal X-Jet Model – Current Results

0 50 100 150 200 250 300 350 400 450 5000

50

100

150

200

250

300

350

Time

Te

mp

era

ture

T_2

T_4

T_6

T_8

T_10

Heat Flux at q=10000 W/m^2

20

• Four sensor nodes and the receiver node will be flown.

• Pressurized capsule allows the balloon’s internal pressure to be measured.

• Capsules made of extruded polystyrene insulation foam.

VAST Flight

VAST Flight: Progress

22

2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

Jan 20-Jan 26

Jan 27-Feb 2

Feb 3-Feb 9

Feb 10-Feb 16

Feb 17-Feb 23

Feb 24-Mar 1

Mar 2-Mar 8

Mar 9-Mar 15

Mar 16-Mar 22

Mar 23-Mar 29

Mar 30-Apr 5

Apr 6-Apr 12

Apr 13-Apr 19

Apr 20-Apr 26

Apr 27-May 3

May 4-May 10

Detailed Design Review

Snap Shot Day X-Jet

VAST Launch

Design Report

Review

Expo (25th)

Everything Due

(6th)

JohnReceive &

Make Boards

Test

LucasWork on Transmit

& Receive

Finish ADC

Finish I 2C

Finish Transmit

Finish Receive

Error Checking

Brandy Model & Design

Testing Revise Revise

Jesse Machine Shop

Assemble 1st Plug

Test

Machine &

Assemble Plug 2

Comparison Test

Assemble Box WRT

PCB

Machine &

Assemble plug 3

ChrisSerial Port

InterfaceRevise

Assemble & Test Boards

Revise & Order Boards

Last Minutes

Repairs and

UpdatesConstruction

Detailed Com Scheme

Xbee 2 Xbee Com

Repairs & Updates

Technical PresentationConstruction Assimilate Data

Test and Revise Design Report

Timeline

23

• Beginning Budget $10,943• Shop and UI Fee $1,360• Travel Allocation $7,343• Beginning Spending Budget $2,240• Current Spending Left $957

Budget Status

Closing• PCB and Programming are our biggest

challenges at this time

• We are within budget

• Still on track to meet all goals