RevGeo Multipurpose Puzzle Box

Dan Chambers, Jeff King, Josh Marchi, Paul Rosenberger,

ECE 477 Group 11

The “Reverse Geocache” Box is a locked box that will only open after one or more pre-determined GPS locations have been visited directing the user to next location by an LCD display. The route is stored on a microSD card located inside the box which is programmed on a PC. A RFID backdoor will allow for access to box without finishing puzzle.

Abstract

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Schematic

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Preliminary Layout - Autorouter

Li-Ion Battery

Locking Mechanism -

Servo

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General Layout Considerations

Keep RS232 close to USB portmicroSD card should be accessibleUSB port accessible to outside of boxCompass should not be placed closed to

any EMI producing components as it relies on the earths magnetic field for its accuracy

Headers for most micro pinsSeparate circuit into blocksNo analog signals present (only digital)Trace size for power and gnd: >30mil

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Inductor close to switching inputs (short traces)High Frequency Signal

Decoupling capacitors located close to input pins and gndReduces supply rippleProvides instantaneous current

Ground plane underneath switching regulatorMinimize noise

Trace Size: 8 mil Large Inductor placementVias placed underneath thermal pad

Thermal performance

Power Supply Considerations

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Power Supply Layout

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Microcontroller ConsiderationsDecoupling capacitors (0.1u) placed close to

supply pinsTrace length; less than 0.25in0.01uF cap in parallel with decoupling caps to

filter high freq noise No external oscillator (Internal 16Mhz

Oscillator)Locate near center of boardSurround components around itNo special trace width required

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Questions?