User manual

ECE 477 Final Report Spring 2004

This result is not surprising, considering we assumed a low quality capacitor and high

stress and temperature. However, actual values may be within a power of 10.

Using this value, MTTF = 1/ λ

= 77,519 hours. This is a lousy value. Before accepting

this, I would want to go back and measure temperature and stress levels in an actual circuit,

because this capacitor is scheduled to blow in under 8 years of use. In a commercial product,

this is utterly unacceptable. Steps would be taken to make sure this component was kept cool

and was a high quality component, and the circuit might be redesigned (maybe splitting the load

among parallel capacitors). But for development, this will have to do. And it must be taken into

account that factors used in estimation are very conservative, and temperature estimates may not

reflect actual running temperatures.

FMECA

For our evaluation, the two levels of criticality are Low (below 10

days MTTF) and

Notable (greater than 10

days MTTF). Nothing really deserves a higher rating than that,

because there is little to no risk of physical injury. The worst risk is the LCD screen going out

and someone getting mad and throwing it at someone, which is beyond our responsibility if we

round out the corners. The failure divisions are noted below. Please note that, although we do

have 2 microprocessors and 2 RF units, they are almost nearly identical, and are lumped

together. Only a single example of each will be included. Also, the power supplies of both the

base and mobile units have been lumped together.

Abbreviation Unit

RF RF Module

PS Power Supply

MC Microcontroller

LED LEDs

LCD LCD Screen and Logic Converters

COM RS-232 Communication

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