Transcript 4/4/2012

Team 9 - Scribacious Rabble
Safety and Reliability Analysis
Mitchell Erdbruegger (presenting)
Paul Rosswurm
William Hess
Ben Kobin
Project Description

Adaptation of the board game SCRABBLE®

Maintains the traditional physical tile interface...

augmented by ..

Sensing tile location and value

Automatically calculating and displaying scores

Maintaining player profiles

Validating words in the event of a 'challenge'

Exposing game stats over an external interface
PSSCs
 An ability to sense the presence and identity of a tile
placed on the board.
 An ability to record game specific metrics for a set of
player profiles.
 An ability to use a standard dictionary to allow a player
to challenge the validity of the last word played.
 An ability to display game relevant information to each
player and allow one user to input game settings.
 An ability to communicate game statistics over an
external interface.
Block Diagram
Chosen Parts
• Micro-Controller (PIC24EP256GU810)

λP = (C1* πT + C2 * πE) * πQ * πL

λP = ( 0.28 * 1.5 + 0.068 * 2.0) * 10 * 1.0

λP = 5.56

MTTF: 20.5 Years
• Low Drop-Out Linear Regulator (LM1117)

λp = λb*πT*πS*πC*πQ*πE

λp = .0020 * 5.1 * 1.0 * 1.0 * 6.0 * 8.0

λP = 0.4896

MTTF: 233 Years
Chosen Parts
• 8-Bit Shift Register (74HC164D)
 λP = (C1* πT + C2 * πE) * πQ * πL
 λP = ( 0.005 * 1.5 + 0.0062 * 2.0) * 10 * 1.0
 λP = 0.199
 MTTF: 573.25 Years
• Opto-Isolator (LTV-826S)
 λp = λb*πT*πQ*πE
 λp = 0.017 * 6.6 * 2.0 * 8.0
 λP = 1.7952
 MTTF: 63.5 Years
• Others Considered
•
LCD Driver (Sitronix ST7565P)
•
Capacitive Grid
Criticality Levels
• Low
• < 10-5 Failures
• No Harm to Users
• Possibly render product unusable
FMECA
Power Supply and LCD Circuits
Failure
No.
PS1
PS2
L1
L2
Failure Mode
VOut = 0
Possible Causes
Failure of the
LM1117, Shorted
Decoup Caps
No Power to
the rest of the
system, Entire
product useless
Failure of the
LM1117
Could
potentially
cause
irreparable
damage to ICs
No backlight on
the LCD
VOut > 3.3V
Output LCD
Contr Always 0
No power going
to LCDs
Failure Effects
LM1117 Failure
(PS1), Shorted
Decoup Cap, Burned
out contr. (Possibly
PS2)
LM1117 Failure
(PS1), Shorted
Decoup Cap
Method of
Detection
Observation
(Use of voltmeter
to check
input/output
voltage)
Observation
(Voltmeter on
output)
Observation
(Oscilloscope
readout)
Nothing can be Observation (Volt
ouput to LCDs
meter)
Product rendered
essentially useless
Criticality
Remarks
Low
Low
Low
Low
Possibly fixed
with zener diode to
protect rest of
circuit
Power Supply
FMECA
Micro-Controller
Failure
No.
M1
M2
Failure Mode
USB D- and D+
always 0 or 1
Micro Pins at
constant signal (0
or 1)
MCLR always 0
M3
MCLR always 1
M4
Possible Causes
Failure Effects
Software bug, broken
usb module (possibly
cause by PS2),
Connected USB
device pulling low or
high
Burned out pins (too
much current or
voltage placed on
pin), software
Failure to
communicate
player statistics to
PC via USB
Peripherals
malfunctioning
Method of
Detection
Observation
(Oscilloscope)
Low
Observation(Volt
meter/
oscilloscope)
Broken reset
Micro useless due
button, burned out
to always sin
pin, shorted decoup reset
caps
Observation
(voltmeter)
Broken reset button,
burned out pin
Observation
(voltmeter)
Mirco cannot
recover without
turning off power
(for debug
purposes only)
Criticality
Low
Low
Low
Remarks
Micro and Reset
FMECA
SD Card, Push Buttons, Column Inputs, Row Select
Failure
No.
SD1
PB1
C1
RS1
Failure Mode
Possible Causes
No Read/Write
Functionality to
SD
Damaged SD Card,
Shorted Decoup
Caps, LM1117
Failure, SPI
malfunction
PB Inputs always
low
Failed pull up
resistor, Shorted
decoup caps,
LM1117 Failure
Failed opto-isolator,
Input from
Failed buffer,
column alsways 0 Burned out micro
or 1
pin
Output to row
always 0 or 1
Burned out pin on
micro, burned out
shift register, shorted
decoup caps,
LM1117 failure,
Software, burned out
buffer
Failure Effects
Method of
Detection
Cannot read or
Observation (Plug
store player data
into PC and check
if data written,
Attempt to read
player data via
USB)
No user input can Observation (Volt
be obtained, game meter)
rendered useless
Cannot sense tiles
properly
Inability to sense
tiles on board
Criticality
Low
Low
Observation
(Oscilloscope.Volt
meter)
Low
Observation(
Voltmeter/
Oscilloscope)
Low
Remarks
Column Inputs
Row Selection
QUESTIONS/COMMENTS?