TCSP – Reliability and Safety

Reliability Analysis Major component chosen for analysis:Major component chosen for analysis: Switching Regulators (LM2679SD-5.0, LM2679SD- 3.3)Switching Regulators (LM2679SD-5.0, LM2679SD- 3.3) Hottest running componentsHottest running components Microcontroller (MCS12A64CFUE)Microcontroller (MCS12A64CFUE) Most complex componentMost complex component Quad 2 to 1 Multiplexer (SN74CBT3257)Quad 2 to 1 Multiplexer (SN74CBT3257) Failure leads to crashingFailure leads to crashing Linear Amplifiers for thermopiles (AD8626)Linear Amplifiers for thermopiles (AD8626) Failure would cause unstable flight, possibly crashingFailure would cause unstable flight, possibly crashing

FMECA Criticality Levels High – Could cause personal injuryHigh – Could cause personal injury Medium – Inhibits ability to fly autonomouslyMedium – Inhibits ability to fly autonomously Low – Inhibits ability to take photos or other inconveniencesLow – Inhibits ability to take photos or other inconveniences

FMECA Block A - Microcontroller

Failure No. Failure ModePossible CausesFailure EffectsMethod of Detection CriticalityRemarks A1Microcontroller outputs no data Out of spec supply voltage, U1 failure, clock failure, PLL failure, software bug, bypass caps shorted No display on LCD, does not work in autonomous mode ObservationMedium- High This failure would be elevated to high criticality if a shorting component caused excess heat dissipation A2Some pins are always 0 or 1 Over-voltage on pin could have burned up the driver, software bug Erratic system behavior, excessive heating of the microcontroller ObservationMedium- High This failure would be elevated to high criticality if a shorting component caused excess heat dissipation

FMECA Block B - Regulators

Failure No. Failure ModePossible CausesFailure EffectsMethod of Detection CriticalityRemarks B1V out,5 = 0V or V out,3.3 = 0V Failure of U6 or U7, Shorted capacitor in Block B, no feedback, external short System shows no operation ObservationHighIf a short is causing the lack of output, excessive heat is being generated which could injury the user B2V out,5 > 5V or V out,3.3 > 3.3V Failure of U6 or U7Could damage any of the ICs on the board, system probably non- functional ObservationHighPossibility of injurious heat dissipation B3V out,5 or V out,3.3 not regulated enough Failure of a capacitor in Block B that becomes and open circuit Erratic microcontroller failure, perhaps repeated resetting ObservationMediumUnlikely to cause harm, but results in non-flyable plane B4V sense > 5VR20 fails and causes a short Microcontroller reports unreasonable battery voltage ObservationLow - Medium Probably just a nuisance which would fry a port pin, but could also cause the entire microcontroller to fail.

FMECA Block C – Radio and Servos

Failure No. Failure ModePossible CausesFailure EffectsMethod of Detection CriticalityRemarks C1Autopilot / Manual multiplexer signal incorrect U18 failure, or failure of any of the resistors or capacitors directly before it Plane does not properly switch between manual and autopilot ObservationHighIf this failure arose during a flight, the plane could crash, possibly injuring a person C2Inputs do not propagate through multiplexer U13 or R40 failureServo motors do not respond to manual input or autopilot ObservationHighThis would cause the plane to crash, possibly injuring someone C3Multiplexer always output either manual or autopilot values S pin of U13 shorted to Vcc or ground Cannot switch operating modes ObservationHighCould cause injury if the drive motor powered up unexpectedly on the ground

FMECA Block D – Thermopile Amplifiers

Failure No. Failure ModePossible CausesFailure EffectsMethod of Detection CriticalityRemarks D1Vref = 0VU14 failure, could also have its input or output shorted to ground Thermopiles do not sense sky properly, unstable flight ObservationHighCould cause injury if crash induced D2Vref > 2.5VU14 failureThermopiles do not sense ground as well, jittery flight ObservationHigh - Medium Could lead to crashing D3Amplifier output is very small Failure of U9 or U10, Failure of any of the resistors in Block D such that they become shorts Plane cannot stabilize ObservationHighWould lead to crashing in autopilot mode, and possibly injure the operator D4Thermopile values read in are erratic Connection to thermopiles could be faulty Jittery flightObservationMediumCould lead to crashing

FMECA Block E – GPS and MicroSD

Failure No. Failure ModePossible CausesFailure EffectsMethod of Detection CriticalityRemarks E1Unable to communicate with MicroSD card Failure of U2, U3, or U4; Any resistor in the SD circuit becomes open; SD card corrupt; software System unable to read MicroSD card, displays error message Observation and BIST MediumNo risk of injury, but the plane cannot operate autonomously E2Unable to communicate with GPS receiver Failure of U15, U16, or U17; resistor in GPS circuit becoming open; faulty cable; software bug System unable to get a GPS lock, waits indefinitely and will not allow autonomous flight Observation and BIST MediumNo risk of injury, but the plane cannot operate autonomously

FMECA Block F – Camera and LCD

Failure No. Failure ModePossible CausesFailure EffectsMethod of Detection CriticalityRemarks F1LCD_TX signal always idle Failure of U12, short or open circuit of any of the capacitors or resistors connected to U12 LCD is always blank ObservationLowThis is a nuisance, but the plane will operate properly F2Camera shutter trigger always open Failure of U11, software malfunction Camera never takes photos ObservationLowThe plane will fly, but no photos will be taken

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