Accelerometer - ADXL345 AN-1023 Fall Detection

Accelerometer - ADXL345 AN-1023 Fall Detection - AN-1023...

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AN-1023 APPLICATION NOTE One Technology Way • P. O. Box 9106 • Norwood, MA 02062-9106, U.S.A. • Tel: 781.329.4700 • Fax: 781.461.3113 • Fall Detection Application by Using 3-Axis Accelerometer ADXL345 by Ning Jia Rev. 0 | Page 1 of 28 INTRODUCTION Senior citizens often suffer accidental falls due to their dimi- nished self-care and self-protection ability. These accidents may possibly have serious consequences if no aid is given in time. Statistics show that the majority of serious consequences are not the direct result of the falls, but rather are due to a delay in assistance and treatment after a fall. In the event of a fall, the danger of post-fall consequences can be greatly reduced if relief personnel can be alerted in time. In light of this, there has been increased development of devices for detection and prediction of fall situations. In recent years, technological advancements in MEMS accelerometer sensors have made it possible to design a fall detector based on a 3-axis accelerometer sensor. These fall detectors operate on the principle of detecting changes in body position when moving by tracking acceleration changes in three orthogonal directions of an individual wearing a sensor. The data is then analyzed algorithmically to determine whether the individual’s body is falling. If an individual falls, the device works with a GPS module and a wireless transmitter module to determine the position and issues an alert for assistance. The core part of the fall detector is therefore the detection principle and the algorithm to judge the existence of an emergency fall situation. The ADXL345 is the latest 3-axis, digital output accelerometer from Analog Devices, Inc., and is well-suited for fall detector applications. This application note, based on the principle research of fall detection for an individual body, proposes a new solution for detection of such fall situations using the ADXL345. ADXL345 MEMS ACCELEROMETER Micro Electronic Mechanical Systems (MEMS) is a semiconductor technology that builds micromechanical structures and elec- trical circuits into a single silicon chip. The MEMS accelerometer is a sensor based on this technology to achieve acceleration sensing on single-axis, dual-axis, or tri-axis conditions. Depending on the application, the accelerometer may offer different ranges of detection from several g to tens of g of digital or analog output, and may have multiple interrupt modes. These features offer the user more convenient and flexible solutions. The ADXL345 is the latest MEMS 3-axis accelerometer with digital output from Analog Devices. It features a selectable ±2 g , ±4 g , ±8 g , or ±16 g measurement range; up to 13-bit resolution; fixed 4 m g /LSB sensitivity; 3 mm × 5 mm × 1 mm ultrasmall package; 40 μA to 145 μA ultralow power consumption; standard I 2 C and SPI digital interface; 32-level FIFO storage; various built-in motion status detection options; and a flexible interrupt system. These features greatly simplify the algorithm for fall
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Accelerometer - ADXL345 AN-1023 Fall Detection - AN-1023...

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