Instrumented Football HelmetReliability & Safety

Failure Rate Calculation

Choose 3-5 components:• PIC18F45K20 Microcontroller• Matchport Wireless Adapter• TPS75733 LDO• LTC3440 Buck/Boost• 5169UBBP01 Lithium Ion Battery

Failure Rate Calculation

Failure Rate Calculation

Parameter Description Value

C1 Die complexity failure rate (MOS) 0.14

πT Temperate coefficient 0.60

C2 Package failure rate 0.2144

πE Environment factor 4.0

πQ Quality factor 10.0

πL Learning factor 2.0

λp 18.832

PIC18F45K20 Microcontroller

FMECA

Functional Blocks• Power Supply• Microcontroller Power• Microcontroller• Matchport Power• Matchport• Accelerometers

Power Supply

Power SupplyFailure

no. Failure mode Possible cause Failure effects Method of detection Criticality

A1Output = 0V

Failure of any component or an external short

Rest of helmet does not function Observation Low

A2 Output > 4.2 V Failure of U25 or U19 and D12

Possible damage to rest of circuitry Observation Low

A4 Battery Charge Voltage out of spec

Failure of U19 Damage to battery, possibly a fire Observation High

A5 Output out of Tolerance U23, C21, C22 Unpredictable

operation Observation Low

Microcontroller Power

Microcontroller PowerFailure

no. Failure mode Possible cause Failure effects Method of detection Criticality

B15V Ouput = 0V U26, L1, D8

Accelerometers stop functioning, no alerts

sentObservation Medium

B2 5V Ouput out of Tolerance C9, C10, L1

Stored data is inaccurate and

unpredictable alarmsObservation Medium

B3 3.3 V Ouput = 0V U28 or external short System does not work Observation Low

B4 3.3V Ouput > 3.3V U28 Damage to SD card, possibly fire Observation High

B5 3.3V Ouput out of Tolerance C14, C16, L3 Some data not stored Observation Low

B60.5V, 4.5V Output out of Tolerance R1, R2, R3

Incorrect accelerometer

measurements storedObservation Low

Microcontroller

MicrocontrollerFailure

no. Failure mode Possible cause Failure effects Method of detection Criticality

C1 TestAcc1-3 continuously 1

Software, short/open-circuit in micro

Accelerometers constantly in self-test

modeObservation Low

C2 SD_CS continuously 1, 0

Software, SPI peripheral fail

No data saved/read from SD card Observation Low

C3 MP_CP1-4 continuously 1

Software, short in micro

Matchport may continuously send

false alertsObservation Low

C4 MP_CP1-4 continuously 0

Software, open-circuit in micro

Matchport will never send alerts Observation Medium

Matchport Power

Matchport PowerFailure

no. Failure mode Possible cause Failure effects Method of detection Criticality

D1 Ouput = 0V U28 or external short

Matchport stops functioning Observation Medium

D2 Ouput > 3.3V U28 Damage to Matchport, possibly fire Observation Medium

D3 Ouput out of Tolerance C14, C16, L3 Unpredictable Matchport

operation Observation Medium

Matchport

MatchportFailure

no. Failure mode Possible cause Failure effects Method of detection Criticality

E1No wireless connection

Damage to Matchport, improperly configured

No wireless device found for connection Observation Medium

E2

No data over serial connection

Damage to Matchport, improperly setup web server, software

Data changed/requested

on wireless connection are not

set/sent

Observation Low

Acclerometers

AccelerometersFailure

no. Failure mode Possible cause Failure effects Method of detection Criticality

F1 Status output continuously high

U5 failureSoftware will enter infinite loop during startup

Observation Low

F2 Status output continuously low U5 failure Accelerometer self-

test will not work Observation Low

F3 X,Y,Z out continuously high

AccX, AccY, AccZ failure

Warnings for high-geforce impacts are sent

Observation using self-test Low

F4 X,Y,Z out continuously low

AccX, AccY, AccZ failure

Warnings for high-geforce impacts are sent

Observation using self-test Low

F5 X,Y,Z out continuously middle (~2.5V)

AccX, AccY, AccZ failure

No warnings for high-geforce impacts are sent

Observation using self-test Medium