solar telematics system reliability and safety analysis craig lechlitner brian kelley clayton...

SOLAR TELEMATICS SYSTEM

Reliability and Safety Analysis

Craig Lechlitner

Brian KelleyClayton Dickemann

Dan Ehrman

Block Diagram

C A N

UA

RT

1

UA

RT

2

S P I

U A R T3D a t a R d y

G P I O

A / D C o n v .

Comm. Controller

P I C 3 2 M X7 9 5 F 5 1 2 H

3 . 3 V

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phic

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Tou

ch/V

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F la s h S P I

Par

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Bac

klig

ht E

NB

ackl

ight

PW

M

Tou

ch C

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Spe

aker

PW

MV

olum

e C

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D a t a R d y

Graphics Controller

P I C 2 4 F J 2 5 6 D A 2 1 0

16 R

GB

/CLK

4-W

ire T

ouch

Scr

een

B a c k lig h t

7 in . L C D To u c h s c re e n

2 0 0 m A

4-W

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ouch

SP

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CS

TouchCntrl.

TS C 2 0 0 0

UA

RT

US

B

M C P 2 2 0 0

UA

RT

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B

U 4

M C P 2 2 0 0

UA

RT

RS

232

M A X3 2 3 2

Par

alle

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2MB 10ns SRAM

I S 6 1 W V 1 0 2 4 1 6 B L L

V in

C TX/ C R X

CA

NH

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NL

CANTrnscv.

M A X3 0 5 1

1234

M in iU S B1234

M in iU S B

123456789

D B 9

12

To C A R

2 0 0 m A

Graphics/AudioController

A u d io P W M A u d io

Vol

ume

SP

IS

PI

CS

Low-Pass FilterAmplifierVolume Control

M C P 6 0 2 / M C P 4 2 4 1 / L M 4 9 5 0

SP

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2 GB Flash Memory

S D C a rd

3

1234

E x t . B u t t o n I n p u t s (8 )

8

4

40 2

4

41

3

2

22

2

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2

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U A R T

GPS

L S 2 0 0 3 1

2

L S 1

S P E A K E R8

1 2 -1 6 V3 . 3 V

2 0 0 m A (9 . 9 V )

200m

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N20

0mA

DIM

P o we r S u p p lie s

PSSCs

1. An ability to track vehicle location using GPS.

2. An ability to receive and send CAN messages from and to other systems in the car.

3. An ability to display graphics on the LCD display.

4. An ability to respond to user input from a touchscreen.

5. An ability to store and load data to and from non-volatile memory.

Components Chosen for Analysis• Graphics Controller (PIC24FJ256DA210)• Communications Microcontroller (PIC32MX795F512H)• SRAM (IS61WV102416BLL)• 3.3v Switch Mode Regulator (LM3407)

PIC24 graphics microcontroller• High complexity (100 pin, 16 bit)• Controls LCD, touch input, audio, SRAM, SD card. Interfaces with

PIC32

λp = 3.76 failures per 106 hours

MTTF = 266,000 hours = 30.4 years

Parameter Description Value Comments

C1 Die complexity 0.28 16 bit microprocessor

πT Temperature coefficient 0.60 70 C Die Temperature (estimate)

C2 Pin count 0.052 100 pin, Nonhermetic SMT

πE Environmental constant 4.0 Ground Mobile

πQ Learning factor 1.0 In production for >2 years

πL Quality factor 10.0 Commercial Product

PIC32 communications microcontroller

• High complexity (64 pin, 32 bit)• Communicates with other systems on CAN bus, GPS, sends

telemetry data.

λp = 4.64 failures per 106 hours

MTTF = 216,000 hours = 25 years


C1 Die complexity 0.56 32 bit microprocessor






SRAM• 16 MBit• Holds frame buffers for LCD.• Interfaces with PIC24.

• λp = 15.84 failures per 106 hours• MTTF = 63,000 hours = 7.2 years


C1 Die complexity 2.48 16MBit,Estimate (table only goes to 1MBit)




λ cyc Cycling induced Failure Rate

0.0 NOT Flotex or Textured-Poly EEPROM



LM2673 Switch mode regulator• Possible high temperature• Powers everything except backlight and audio amplifier• 12-15v unregulated input• 3.3v, 3Amax regulated output

• λp = 0.376 failures per 106 hours• MTTF = 2,660,000 hours = 304 years


C1 Die complexity .04 Estimate 101 to 1000 MOS transistors (Linear model






Definition of Criticality levels• High - Possibility of injury to user• Medium - Renders device useless, major repairs needed• Low – Majority of device still works, easily repairable

FMCEA chartFailure mode Possible causes Effect Detection method Criticality

Power supply becomes unregulated (Vout > 3.3v)

Failure of U5 Possible damage to most ICs, excessive heat build up, smoke and fire

Observation (smell of burning electronics), probe 3.3v line

High

3.3v Power supply becomes shorted

Failure of U5, D5, C19, etc

Only backlight works, possible heat build up, smoke and fire

Observation (visual, smell of burning electronics), probe 3.3v line

High

Device fails to power up Blown fuse due to temporary short circuit

or reverse polarity on VIN

Nothing works Observation (visual) Low

Pin on either PIC24 or PIC32 becomes constant 1 or 0

Software, poor soldering, failure of peripheral.

Specific function stops working

Observation Low - Medium

Failure to communicate with other systems on CAN bus.

Failure of U10 (PIC32), or U13 (MAX 3051), software in this or another system.

Cannot control headlights, wiper, vehicle direction. Cannot display battery or solar array stats, etc.

Self check Low, can still display vehicle speed/position, vehicle will still drive.

Data in SRAM becomes corrupted/unreadable

Failure of U3 (SRAM), U1 (PIC24)

Erratic data sent to LCD Observation (visual), use logic analyzer

Low - Medium

Questions?

solar telematics system reliability and safety analysis craig lechlitner brian kelley clayton...

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