Transcript Safety and Reliability Analysis

ECE 477 Group 3
The Gauntlet
George Hadley
Kelli Hacker
Sean Ma
Jacob Champion
Critical Safety and Reliability
Issues
Battery undervoltage – possible explosion
causing injury to the user
 GPS malfunction during “emergency
mode” – does not lead user back to a safe
point, possibility of becoming more lost
 Sensor malfunction – loss of functionality

Components Most Likely to Fail

Complexity
PIC24 microcontroller
 VS1011E MP3 decoder


Heat
LTC3440 Buck-boost dc/dc converter
 MCP73811 Linear charge manager

FMECA Analysis - Power
Failure
No.
A1
Failure Mode
Possible Causes
Power rail = 0 V
Short, disconnect in
power supply circuit
A2
Power rail > 3.3
V
Buck-boost failure,
short to battery
A3
Battery
undervoltage
A4
Battery
overvoltage
Analog comparator
fails, excessive noise
on buck-boost
output, charger fails
Charger fails and
short circuits
Power Subsystem
Failure Effects
Method of
Detection
Nothing turns on
Observation
or operates
Criticality
Low
Damage to
components
throughout
circuit, loss of
functionalilty
Possible battery
explosion
Observation
Low
Observation
High
Possible battery
explosion
Observation
High
Remarks
FMECA Analysis Microcontroller
Failure
No.
B1
Failure Mode
Microcontroller
receives < 3.3 V
Microcontroller Subsystem
Possible Causes
Failure Effects
Method of
Detection
Bypass capacitor
Microcontroller
Observation
shorts
will not operate,
no functionality
Criticality
Low
B2
External
oscillator fails
Failure of individual
components
No audio output,
errors more likely
in LCD
communication
Observation
Low
B3
Microcontroller
stuck in loop
Loss of
communication with
sensors
Loss of
functionality
Observation
Low
Remarks
FMECA Analysis - Audio
Failure
No.
C1
C2
Failure Mode
Possible Causes
MP3 decoder
receives < 3.3 V
Bypass capacitor
shorts
MP3 decoder
chip stops
working
Decoder receives
ESD, output
capacitors short
Audio Subsystem
Failure Effects
Method of
Detection
Audio does not
Observation
operate
Audio does not
operate
Observation
Criticality
Low
Low
Remarks
Mitigating Safety and Reliability
Concerns
Battery undervoltage – analog comparator
used, can change resistor values for
greater safety margin
 Add code to jump out of polling loop and
mitigate loss of sensor information

Questions?