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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4 Schematic

Preliminary Layout - Autorouter 5 Li-Ion Battery Locking Mechanism - Servo

General Layout Considerations Keep RS232 close to USB port microSD card should be accessible USB port accessible to outside of box Compass 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 pins Separate circuit into blocks No analog signals present (only digital) Trace size for power and gnd: >30mil 6

7 Inductor close to switching inputs (short traces) High Frequency Signal Decoupling capacitors located close to input pins and gnd Reduces supply ripple Provides instantaneous current Ground plane underneath switching regulator Minimize noise Trace Size: 8 mil Large Inductor placement Vias placed underneath thermal pad Thermal performance Power Supply Considerations

8 Power Supply Layout

9 Microcontroller Considerations Decoupling capacitors (0.1u) placed close to supply pins Trace length; less than 0.25in 0.01uF cap in parallel with decoupling caps to filter high freq noise No external oscillator (Internal 16Mhz Oscillator) Locate near center of board Surround components around it No special trace width required

Questions? 10