Reliability and Safety Analysis
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Reliability and Safety Analysis Team 4: Shicheng Guo , Kyle Haver, Ethan Price, Wesley Tso
description
Reliability and Safety Analysis. Team 4: Shicheng Guo , Kyle Haver , Ethan Price, Wesley Tso. Overview. Device that automatically roasts coffee beans based on a roast level selected by user via GUI. Device uses base popcorn popper, as well as a variety of sensors, to achieve automation. - PowerPoint PPT Presentation
Transcript of Reliability and Safety Analysis
Reliability and Safety Analysis
Team 4: Shicheng Guo, Kyle Haver,
Ethan Price, Wesley Tso
Device that automatically roasts coffee beans
based on a roast level selected by user via GUI.
Device uses base popcorn popper, as well as a variety of sensors, to achieve automation.
Safety is a major concern due to high power usage and heat generated by device being the main possible causes of critical failures.
Overview
An ability to achieve different levels of roasting based on
user input. An ability to detect the temperature of the beans. An ability to monitor the color of the beans An ability to interact with the user via GUI An ability to shut off the device if unusual conditions
(dangerously high temperatures, unusual color in roasting area, or timeout) are detected.
PSSCs
Components listed in order of “closeness” to power and
heat of device. AC Relay (ST24D12): controls heating coil. DC Relay (LCA717S): controls cooling fans and rotates
beans. Microprocessor (ATMEGA8A-AU): controls overall
operation, including the relays and safety checks. Voltage Regulator (LM7805CT): regulates power to
microprocessor, therefore indirectly affecting relays. Transformer (273-1512): supplies power to
microprocessor circuit, including voltage regulator, relays, voltage regulator, and microprocessor.
Components Chosen
λp = λb * πQ * πE Failures/10^6 hours.
λp = 1.6 Failures/10^6 hours.
AC Relay
Parameter name
Description
Value Comments
λb Base Failure Rate 0.40 Solid state without time relay
πQ Quality Factor 4.0 Commercial spec.
πE Environment Factor 1.0 For use in homes, which are not mobile have temperatures are within human tolerances.
λp = λb * πQ * πE Failures/10^6 hours.
λp = 1.6 Failures/10^6 hours.
DC Relay
Parameter name
Description
Value Comments
λb Base Failure Rate 0.40 Solid state without time relay
πQ Quality Factor 4.0 Commercial spec.
πE Environment Factor 1.0 For use in homes, which are not mobile have temperatures are within human tolerances.
λp = (C1 * π T + C2 * π E) * xQ * xL Failures/10^6
hours.
λp = 0.2818 Failures/10^6 hours.
MicroprocessorParameter name Description
Value Comments
C1 Die Complexity Failure Rate 0.14 8 bit Microprocessor.
πT Temperature Factor 0.96 No mention of junction temperature in datasheet; used 85C maximum temperature for overall device.
C2 Package Failure Rate .013 DIP with under 36 pins, soldered.
πE Environmental Factor 0.5 For use in homes, which are not mobile have temperatures are within human tolerances.
xQ Quality Factor 2.0 Basic quality compliance.
xL Learning Factor 1.0 Has been in production for > 2 years.
λp = λb * πT * πS * πC * πQ * πE Failures/10^6
hours.
λp = 0.02448 Failures/10^6 hours.
Voltage Regulator
Parameter name
Description
Value Comments
λb Base Failure Rate 0.0020 Default value for all voltage regulators.
πT Temperature Factor 5.1 Max junction temperature of 125C.
πS Electrical Stress Factor 1.0 Default value for all voltage regulators.
πC Contact Construction Factor 1.0 Metallurgically Bonded contacts
πQ Quality Factor 2.4 Lowest quality factor for discrete semiconductors.
πE Environment Factor 1.0 For use in homes, which are not mobile have temperatures are within human tolerances.
λp = λb * πQ * πE Failures/10^6 hours.
λp = 0.057 Failures/10^6 hours.
Transformer
Parameter name
Description
Value Comments
λb Base Failure Rate 0.019 No operating temperature found, as this is a generic transformer from Radio Shack with no data sheet. Used conservatice 100C max rating with second weakest insulation class.
πQ Quality Factor 30 Is a power transformer, commercial spec.
πE Environment Factor 1.0 For use in homes, which are not mobile have temperatures are within human tolerances.
Sensors (Microphone, Camera, Thermometer) Rotary Encoder LED Display
Other Components
Most prone to critical failures are the relays. Possible design alternatives:
Have two relays ORed together for each current relay. For AC Relay, OR for off functionality. For DC relay, OR for on functionality.
Spend way more money on higher grade relays. Neither are very appealing.
Summary
AC Relay Data Sheet:
http://www.teledynerelays.com/pdf/industrial/st.pdf
DC Relay Data Sheet: http://www.clare.com/home/pdfs.nsf/www/LCA717.pdf/$file/LCA717.pdf
Microprocessor Web Link: http://www.atmel.com/devices/atmega168a.aspx
Voltage Regulator Data Sheet: http://www.fairchildsemi.com/ds/LM/LM7805.pdf
Transformer Web Link: http://www.radioshack.com/product/index.jsp?productId=2102703
Links
