ECE477 Team 6: The Soviet Challenge FMECA worksheet presentation

Criticality measures Low High General annoyance – screen stops working, buttons don’t work λ < 10-6 High Parts get dangerously hot, catch fire, and/or explode λ < 10-9

Schematic

Battery Pack – “A”

Battery Pack – “A” Failure No. Failure Mode Possible Causes Failure Effects Method of Detection Criticality Remarks A1 Header Output 1 = 0V Battery Disconnected, Battery dead, Protection circuit failure Device is inoperable Observation Low   A2 Header Output 2 = 0V U19 (DS2781) failure, R74 damaged, Battery dead Unable to track battery life via uC, in the cases of U19, R74 failure A3 Battery Shorted out Traces in battery circuit short out, wiring from battery terminals short out Battery discharges VERY rapidly (Protection circuit keeps from exploding) High A4 Header output 1 > 8.4V Protection circuit failure Battery becomes overcharged, can lead to overheating, possibly explosion

3.3V Regulator – “B”

3.3V Regulator – “B” Failure No. Failure Mode Possible Causes Failure Effects Method of Detection Criticality Remarks B1 PWR_3.3 < 3.3V U20 (LTC1174-3.3) failure Circuit becomes underpowered, device is inoperable Observation Low   B2 PWR_3.3 > 3.3V U20 damaged Other components in circuit could be damaged by overvoltage High B3 PWR_ON+ > 14.4V Short in SW4 between PWR_ON+ and PWR_OFF+, along with a failure of U18 (MAX846A) Damage to U20, can lead to B2 happening

Battery Recharger – “C”

Battery Recharger – “C” Failure No. Failure Mode Possible Causes Failure Effects Method of Detection Criticality Remarks C1 PWR_OFF+ <8.4V Wall Wart disconnected, R76, R75 or, R70 short Battery won’t charge completely Observation Low   C2 PWR_OFF+ >8.4V U18 (MAX846A) Damaged, short in recharger, R76, R75, or R70 damaged Battery runs the risk of being overcharged if protection circuit has failed High C3 Conn Jack Pwr input >21V Power surge from outlet U18 damaged

Compact Flash Circuit – “D”

Compact Flash Circuit – “D” Failure No. Failure Mode Possible Causes Failure Effects Method of Detection Criticality Remarks D1 No transmission from CompactFlash card CF card disconnected or loose, PWR disconnected, software TetriNET will not be playable online. Observation Low  

Microcontroller Circuit – “E”

Microcontroller Circuit – “E” Failure No. Failure Mode Possible Causes Failure Effects Method of Detection Criticality Remarks E1 Continual resetting Y1, C26, C27 – problem with the crystal circuit, software Device will be inoperable Observation Low   E2 Timer overflow A game of TetriNET lasts longer than 6.362915 days Code will have erratic effects

Button Circuit – “F”

Button Circuit – “F” Failure No. Failure Mode Possible Causes Failure Effects Method of Detection Criticality Remarks F1 Buttons don’t register inputs BTN_SEL not changing, U17 (ATF16LV8C) damaged, button wiring loose Device cannot be properly operated Observation Low  

LCD Circuit – “G”

LCD Circuit – “G” Failure No. Failure Mode Possible Causes Failure Effects Method of Detection Criticality Remarks G1 Displays nothing U4/U5 (LCD headers) connectors damaged or loose, ezLCD-001 damaged Device cannot be used Observation Low   G2 Displays gibberish Software error, ezLCD-001 damaged, header connections not secure Device unstable or unusable

Reprogramming Circuit – “H”

Reprogramming Circuit – “H” Failure No. Failure Mode Possible Causes Failure Effects Method of Detection Criticality Remarks H1 Circuit cannot be reprogrammed U9/U10 (ISP/JTAG headers) damaged or loose Cannot reprogram microcontroller Observation Low