SLAA351A April   2007  – November 2018 MSP430F2232 , MSP430F2232 , MSP430F2234 , MSP430F2234 , MSP430F2252 , MSP430F2252 , MSP430F2254 , MSP430F2254 , MSP430F2272 , MSP430F2272 , MSP430F2274 , MSP430F2274

 

  1.   A Simple Glass-Breakage Detector Using an MSP430™ MCU
    1.     Trademarks
    2. 1 Introduction
    3. 2 Hardware Description
      1. 2.1 Device Specifications
      2. 2.2 Power Supply
      3. 2.3 Microphone
      4. 2.4 LED and Buzzer Alert
      5. 2.5 Interface to CC1100 or CC2500 Devices
      6. 2.6 Operational Amplifiers (OAs)
      7. 2.7 Internal Very-Low-Power Oscillator (VLO)
      8. 2.8 JTAG Interface
      9. 2.9 Current Consumption
    4. 3 Software Description
      1. 3.1 Initialization Routine
      2. 3.2 Timer_A
      3. 3.3 ADC10
      4. 3.4 Signal Analysis
        1. 3.4.1 First Stage of Processing
          1. 3.4.1.1 Signal Averaging, Peak Detection, and Zero Crossings
          2. 3.4.1.2 High-Pass Filtering
        2. 3.4.2 Second Stage of Processing
          1. 3.4.2.1 Frequency Composition Ratio
          2. 3.4.2.2 Peak and Zero-Crossing Count
          3. 3.4.2.3 Glass-Breakage Detect
    5. 4 Hardware Schematic
    6. 5 Test Setup
    7. 6 References
  2.   Revision History

2.4 LED and Buzzer Alert

Glass-breakage detection is indicated by a buzzer or an LED. The buzzer used in this application is the Panasonic EFB-RL37C20. This buzzer can generate sound level outputs up to 106 dB at a frequency of 3.7 kHz. For high sound levels, a large voltage must be supplied to this buzzer. To obtain this high voltage, a DC/DC boost converter is used. The low-power TPS61040, which can provide an output voltage of 28 V when sourced by a 3-V voltage supply, is used. The current consumption during its operation is approximately 15 mA. This TPS61040 supports an enable signal that is controlled in software by port pin P3.7 of the MSP430 MCU to turn on only during a glass breakage. The buzzer circuit can also be disabled using the onboard jumper (JP3) that physically disconnects the power to the buzzer, so that indications can be given using only the LED.