1 Capstone Design Project Silent Alarm System Students: Su Huang & Fenghua Chen Advisor: Professor James Hedrick March 03, 2007

2 Current Safety Alert System Emergency phone booths Surveillance cameras Wired together (underground) Connect to Campus Safety

3 Disadvantages of Current System Slow notification of incident Surveillance cameras have blind spots Fixed in numbers and locations

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

5 Keychain (student) Central Station (Campus Safety) Signal Schematic Diagram Sub. Substation Key Chain (Student, faculty, etc)

6 The Big Picture

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

8 Design Specifications Transmit Frequency: 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

9 Hardware Components Microcontroller (C8051) Parallax RF Transceiver Parallax Education Board Keychain Key Chain 433MHz Transceiver by All Spectrum Electronics

10 Block Diagram Transmitter Station Receiver Station

11 Communication Protocol Transmitter Check for button press Synchronization Start character Message End character Back to checking

12 Communication Protocol (cont) Receiver Wait for start character Getting message Wait for stop character Send alarm Back to wait

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

14 Results Spectrum Analyzer Antenna noise Receiver Sensitivity: -106 ~ -118 dBm

15 Results Oscilloscope Message Data (no transmission) Noise only

16 State Diagram (Receiver#2)

17 LR Receiver and LS Decoder Linx Technologies ®

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

19 Results Oscilloscope Message Received

20 Results Xmtrwide With Noise

21 Disadvantages Wireless signal strength problem False Alarms Solutions are: fine, lock, save ID on keychain Device Failure Inaccurate position detection

22 Future Thoughts Open Shortest Path First More accurate position detection (i.e. GPS) Vibration (feedback to user) Individual ID for each transmitter

23 Acknowledgements Advisor: Professor Hedrick Nelson Rosario

24 Questions?