SLAA351A April 2007 – November 2018 MSP430F2232 , MSP430F2232 , MSP430F2234 , MSP430F2234 , MSP430F2252 , MSP430F2252 , MSP430F2254 , MSP430F2254 , MSP430F2272 , MSP430F2272 , MSP430F2274 , MSP430F2274
This application report describes a simple glass-breakage detector using the MSP430F2274 ultra-low-power microcontroller (MCU). The algorithm is based on the spectral analysis of a typical glass-breakage signal. The input signal spectrum, limited to a frequency of 20 kHz, is processed for a valid glass breakage. Various signal characteristics such as peak content, number of zero crossings, and frequency composition are analyzed. Real-time signal processing is achieved by implementing and using a low-order bireciprocal lattice wave digital filter (LWDF). A glass-breakage alert is indicated by an onboard buzzer and an LED. The entire setup is designed to operate at low power, allowing long battery life.
Related schematics and code source can be downloaded from www.ti.com/lit/zip/slaa351.
For more information, see A Simple Glass-Breakage Detector Reference Design and
A Robust Glass-Breakage Detector Reference Design.
MSP430 is a trademark of Texas Instruments.
All other trademarks are the property of their respective owners.
A glass-breakage detector can help ensure safety in buildings and homes. It is a simple mechanism to detect illegal entry through glass windows and doors. The detector analyzes acoustic signals produced during a glass breakage.
The frequency spectrum of the sounds produced during a glass breakage varies with the type of glass used in these doors and windows. This calls for a variety of solutions tailored to types of glass used. In this application report, typical glass-breakage sounds have been used as a tool to design the alert mechanism. These acoustic signals are analyzed after being captured by an onboard microphone. The steps that follow this capture are explained in detail in this report.
The MSP430F2274 is the microcontroller chosen to do this analysis.[2] Although the processor can operate up to 16 MHz, an active-mode frequency of 12 MHz is used.[1] Furthermore, the CPU operating frequency is changed between 8 MHz and 12 MHz to reduce power consumption. The required peripherals are enabled every 2 ms, only when the input signal needs to be captured, to ensure optimal power management. An optional anti-aliasing filter (AAF) in hardware is activated to ensure the signal spectrum is restricted to 20 kHz. The total power consumption of the system is approximately 80 µA with the AAF enabled and approximately 50 µA with the AAF disabled.
The entire hardware setup, software flow, and test setup are discussed in this report. The following sections provide a complete description of the hardware, software, and test setup. The complete details of this reference design are provided in A Simple Glass-Breakage Detector Reference Design.
This section describes the glass-breakage detector board using the MSP430F2274 MCU.
