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Published byTheresa Harrington Modified over 9 years ago
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1 Capstone Design Project Silent Alarm System Students: Su Huang & Fenghua Chen Advisor: Professor James Hedrick March 03, 2007
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2 Current Safety Alert System Emergency phone booths Surveillance cameras Wired together (underground) Connect to Campus Safety
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3 Disadvantages of Current System Slow notification of incident Surveillance cameras have blind spots Fixed in numbers and locations
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4 What is a Silent Alarm System? A personal safety alert system Mobile device Wireless transmission Easy, silent activation Instant alert to Campus Safety Better location tracking
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5 Keychain (student) Central Station (Campus Safety) Signal Schematic Diagram Sub. Substation Key Chain (Student, faculty, etc)
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6 The Big Picture www.google.com
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7 The Project Idea by Nelson Rosario Originally based on Parallax Education Board Migration to C8051 MCU platform Develop a communication platform for software engineers Develop basic communication protocol Built a standalone prototype on a PCB board
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8 Design Specifications Transmit Frequency: 433.92 MHz Transmit Range: 500ft Transmitter Output Power: -4 ~ 8 (dBm) Receiver Output Power: -4 ~ 4 (dBm) Baud Rate: 9600 bps Receiver Sensitivity: -106 ~ -118 (dBm) Meet all FCC and Public Safety regulations
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9 Hardware Components Microcontroller (C8051) Parallax RF Transceiver Parallax Education Board Keychain Key Chain 433MHz Transceiver by All Spectrum Electronics
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10 Block Diagram Transmitter Station Receiver Station
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11 Communication Protocol Transmitter Check for button press Synchronization Start character Message End character Back to checking
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12 Communication Protocol (cont) Receiver Wait for start character Getting message Wait for stop character Send alarm Back to wait
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13 Communication Protocol (cont) Start signal: character “!” Message: can take up to as much as 25 ASCII characters Test message: string “IRE” End signal: character “@”
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14 Results Spectrum Analyzer Antenna noise Receiver Sensitivity: -106 ~ -118 dBm
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15 Results Oscilloscope Message Data (no transmission) Noise only
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16 State Diagram (Receiver#2)
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17 LR Receiver and LS Decoder Linx Technologies ®
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18 Progress Report A prototype is built Signal/noise measurements using Spectrum Analyzer Improving protocol to be more flexible and noise resistant Building filter circuit
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19 Results Oscilloscope Message Received !,I,R,E,@
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20 Results Xmtrwide With Noise
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21 Disadvantages Wireless signal strength problem False Alarms Solutions are: fine, lock, save ID on keychain Device Failure Inaccurate position detection
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22 Future Thoughts Open Shortest Path First More accurate position detection (i.e. GPS) Vibration (feedback to user) Individual ID for each transmitter
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23 Acknowledgements Advisor: Professor Hedrick Nelson Rosario
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24 Questions?
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