GNMS
Safety and Reliability
Analysis
Eric Ellett
Daniel Grum
Larry Price
Jason Rice
Abstract
The GNMS (GNMS's Not Microsoft Surface)
Touch Surface is a multi-touch enabled table
designed specifically for touch-based
gaming. The surface utilizes Frustrated Total
Internal Reflection [FTIR] technology to
create an engrossing computing experience
for a fraction of the cost of similar products.
Block Diagram
Definition of Criticality Levels
• Low
o Low critical failures mean that the user will be inconvenienced in his
or her use of the product or certain peripheral features will not work.
The main functionality of the product, that of providing an
immersive touch interface, will not however be impeded.
o   10-6 is the target failure range for this type of failure.
• Medium
o Product is rendered inoperable in its main functionality.
o   10-7 is the target failure range for this type of failure.
• High
o Product is rendered inoperable and the user is exposed to risk of
injury.
o   10-9 is the target failure range for this type of failure.
Parts Chosen for Analysis
• AT32UC3B164
o Microcontroller that controls everything on our PCB.
o Contains complicated integrated circuits such as ATD convertors,
PWM, and 28 input/output pins.
• LM3671
o Step-Down DC power convertor that converts 5.0V down to 3.3V.
o Has complicated integrated circuitry inside a very small package.
• MAX232ECWE
o Allows us to send our serial communication out to our motherboard.
o Has complicated integrated circuitry.
• TIP120
o Controls both of our 200mm cooling fans.
o Handles 12.0V and around 40mA of current.
AT32UC3B164 FMECA Analysis
Failure Failure Mode
No.
1.
No
communication
is possible
between the
microcontroller
and motherboard
Possible Causes
Microcontroller has
failed completely or
the UART
subsection of the
microcontroller has
failed
2.
Fans no longer
respond to
temperature
changes and are
always off
Microcontroller has
failed completely or
the PWM or ATD
subsection has failed
3.
Projector can no
longer be
controlled by
buttons
Microcontroller has
completely failed or
the PWM subsection
has failed
Failure Effects
Method of
Detection
Buttons for
Hook up a
volume will no logic analyzer
longer work and to PA27 and
temperature data see if any data
can not be read is sent.
from
microcontroller
Overheating of
After 5-10
all the
minutes of
components of
running the
the product
fans should be
which may cause running due to
product failure. heat buildup.
In extreme cases Also directly
may cause harm measuring
to the user due to PWM output
burns.
with
oscilloscope.
The user will no
longer be able to
access any
projector
controls
View the
projector
control LED
under an IR
camera
Criticality
Remarks
Low
The only thing that this
will prevent the user to
do will be to use the
extra functionality that
PCB/Motherboard
connections allow.
High
Our projector has
reached heat of around
60-70 degrees Celsius
in testing which can
cause shorter product
life and if left to
continue heat buildup
may cause harm if
anyone was to open the
product up and come
into contact with the
overheating parts
Low
AT32UC3B164 FMECA Analysis
Failure Failure Mode
No.
4.
Fans Always on
despite low
temperatures
Possible Causes
Failure Effects
ATD convertor no
longer working
Fans will be
continually on
thus decreasing
their life.
Method of
Detection
Send 10mA to
both
temperature
sensors to see
if the fans turn
off.
Criticality
Low
5.
None of the
buttons work
Microcontroller has
failed completely or
the GPIO subsection
has failed
User will be
unable to control
either the
volume of the
project or any of
the temperature
settings.
If buttons do
Low
not respond
direct
measuring via
a voltmeter of
the output pins
may be the
only viable
means of
detecting this.
6.
Projector can no
longer be
controlled by
buttons
Microcontroller has
completely failed or
the PWM subsection
has failed or the
GPIO subsection
has failed
The user will no
longer be able to
access any
projector
controls
View the
projector
control LED
under an IR
camera
Low
Remarks
No functionality
affected except for the
fact that the fans may
produce unnecessary
noise and that their
lifetime may be
shortened.
AT32UC3B164 Reliability
Analysis
• Equation Used: λp =(C1* πT+C2*πe)*πL*πQ
• Result: λp=3.72 Failures/10^6 hours
Parameter name Description
Value
Comments
C1
Die complexity
.56
MOS microprocessor with 32 bits
πT
Temperature coeff.
.6
Assume worst case temperature of 70
degrees Celsius
C2
Number of pins constant
.018
πe
Environmental Constant
2.0
πL
Learning factor
1.0
Assumed that number of functional
pins meant number of GPIOS and not
total pin count
Assumed that our product would
operate in a Ground, Fixed
environment in a temperature
controlled building.
Has been in production more than
two years (5 to be exact)
πQ
Quality factor
10
Just going off of the document,
don’t‘ really know how to estimate
this
LM3671 FMECA Analysis
Failure Failure Mode
No.
7.
Low voltage
across the input
to the circuit and
ground coupled
with high current
use
Possible
Causes
Either the
bulk
capacitors
have shorted
or the
LM3671 has
failed thus
causing a
short
between the
5.0V input
and ground
Higher than 3.3V LM3671 has
on the 3.3V rail failed in such
a way that
allows for
higher
voltage to be
put on to the
3.3V rail (up
to 5.0V)
Failure Effects
Method of Criticality
Remarks
Detection
Nothing on the PCB will The product
Medium
NOTE: This error has
work and the power
turns off and
been produced by
supply will turn off due wont turn
accident in lab many
to the short causing the
back on until
times. Thus far the
whole system to turn off. the PCB is
other PCB components
Thus far no PCB
disconnected
have been unharmed
components have been
from power or
affected except for the
a short is
LM3671
recorded from
the 5.0V input
to GND
8.
After a short period of
time at the higher voltage
several components such
as the microprocessor
will fail. All peripherals
depending on the
microprocessor will also
fail. The fans will no
longer be turning causing
the product to overheat
Voltmeter
High
detects higher
than 3.3V on
the 3.3V rail
after device
failure on the
PCB
Any failure that takes
out our cooling system
is of high concern due
to the build up of heat
that will shorten the
lifetime of the product
and may cause injury
to the user
LM3671 Reliability Analysis
• Equation Used: λp =(C1* πT+C2*πe)*πL*πQ
• Result: λp=5.92 Failures/10^7 hours
Parameter name Description
Value
Comments
C1
Die complexity
.02
Modeled as Linear CMOS chip with
101 to 300 transistors
πT
Temperature coeff.
2.8
Assume worst case temperature of 80
degrees Celsius
C2
Number of pins constant
.0016
πe
Environmental Constant
2.0
Assumed that our product would
operate in a Ground, Fixed
environment in a temperature
controlled building.
πL
Learning factor
1.0
Has been in production more than
two years
πQ
Quality factor
10
Just going off of the document, don’t
really know how to estimate this
MAX232ECWE FMECA Analysis
Failure Failure Mode
No.
9.
No
communication
happens between
the PCB and
motherboard but
all other PCB
functions are
working
Possible Causes
MAX232ECWE
has failed or any
of the capacitors
that are part of
the
MAX232ECWE
circuit have
shorted or
become open
circuits
Failure Effects
Method of
Criticality
Detection
None of the
Measure via a
Low
commands such as logic analyzer
volume up and
the information
volume down will coming from
work and the
the
motherboard cannot microcontroller
get any information to the
from the PCB
MAX232ECW
E and the
information
coming from
the MAX232
and see if they
match
Remarks
Everything except for
the volume up and
volume down
commands will still
work if this chip were
to fail so this is a very
low criticality error
MAX232ECWE Reliability
Analysis
• Equation Used: λp =(C1* πT+C2*πe)*πL*πQ
• Result: λp=9.52 Failures/10^7 hours
Parameter name Description
Value
Comments
C1
Die complexity
.14
No gate or transistor count given,
approximated as 8 bit microprocessor
πT
Temperature coeff.
.6
Assume worst case average
temperature of 70 degrees Celsius
C2
Number of pins constant
.0056
16 Pins total
πe
Environmental Constant
2.0
πL
Learning factor
1.0
Assumed that our product would
operate in a Ground, Fixed
environment in a temperature
controlled building.
Has been in production more than
two years (9 to be exact)
πQ
Quality factor
10
Just going off of the document,
don’t‘ really know how to estimate
this
TIP120 FMECA Analysis
Failure
No.
Failure Mode
Possible Causes
Failure
Effects
Method of
Detection
Criticality
Remarks
10.
TIP 120
Overheating or
becomes an open static discharge
circuit
have damaged
the TIP120
The fans will
no longer work
causing heat to
build up in the
case.
Check the signal
High
coming from the
microcontroller
PWM that controls
the fans. If this
signal is in proper
configuration but the
fans are not working
then something is
wrong with the
TIP120
Our projector has
reached heat of around
60-70 degrees Celsius
in testing which can
cause shorter product
life and if left to
continue heat buildup
may cause harm if
anyone was to open the
product up and come
into contact with the
overheating parts
11.
TIP 120
becomes a short
circuit
Fans will
continually be
on
Measure the
resistance between
the 12.0V input and
GND for the fans
and see what the
resistance is
No functionality
affected except for the
fact that the fans may
produce unnecessary
noise and that their
lifetime may be
shortened.
Overheating or
static discharge
have damaged
the TIP120
Low
TIP120 Reliability Analysis
• Equation Used: λp = λb*πT*πA*πR*πS*πQ*πE
• Result: λp=2.915304 Failures/10^7 hours
Parameter name Description
Value
Comments
λb
Base Failure Rate
.00074
No gate or transistor count given,
approximated as 8 bit microprocessor
πT
Temperature coeff.
2.5
Assume worst case temperature of 70
degrees Celsius
πA
Application Factor
.7
Switching Application
πR
Power Rating Factor
4.69
πS
Voltage Stress Factor
1.0
Has been in production more than
two years (9 to be exact)
πQ
Quality factor
8.0
Assumed that our product has plastic
covering
πe
Environment Factor
6.0
Assumed that our product would
operate in a Ground, Fixed
environment in a temperature
controlled building.
?