Person Fall Detection Through Energy Harvesting

Piezo Harvester Based Automatic Fall Detector SystemNeed for Automatic Fall DetectorsFalls are widespread domestic accidents among elderlySerious physical and psychological effectsStatistics show that the majority of serious consequences are not the direct result of falling, but rather are due to a delay in assistance and treatment.Post-fall consequences can be greatly reduced if relief personnel can be alerted in time.

Features of Our systemComfortable and Non-Obtrusive device

Can be worn for long durations- User friendly

Detects falls with greater sensitivity

False alarms are minimized

Power supply module designRequires a 5V and a 3.3V supplies 5V to power ADXL345 chip 3.3V to power ATmega32 ChipBoth are derived using 9V battery5V is obtained using 7805 regulator3.3V is obtained using LM317

Modules IntegratedThe iMEMS Accelerometer(ADXL345)MCU (ATmega328)Audio BuzzerPiezoelectric Energy Source (Demo Grid)

Programmer and programming softwareProgrammer is chosen to be Arduino Uno Cheapest programmer Communication-USB Freeware AVR GCC C compilerProgramming Software Arduino IDE

Configuring ADXL345(ADXL345 Features A brief Recap)3-axis accelerometer with digital outputSelectable measurement range 2-g,4-g,8-g or 16-gResolution up to 13 bitsFixed sensitivity 4mg/LSBProgrammable interrupt pins INT1 and INT2 with 8 interrupt functions (simplifies algorithm)

Configuring ADXL345(Interface build up and Interrupt enabling)Setting up 4-wire SPI communicationWriting appropriate control words into registers to enable interrupts which can detect Free fall Activity Inactivity

Configuring ADXL345(4-wire SPI communication)The device that controls the system is called master (Atmega32)Any peripheral device that communicates with MCU is slave (ADXL345)4-wire SPI operates as full duplex synchronous linkSCLK should be supplied by masterConfiguring ADXL345(Data and control lines of SPI)Out of 4 lines 2 are data lines(MOSI,MISO) 1 is a control line(CS) 1 is clock(SCLK)

Proteus Simulation of SPI

Configuring ADXL345(I2C Communication)

Configuring ADXL345Setting up SPI(4-wire)Pin to pin connection for setting up SPIAfter physical connection, SPI is enabled in ADXL345 by writing 0x08 in DATA_FORMAT

Configuring ADXL345(Setting up I2C)CS is tied to 5V Supports standard 100KHz and fast 400KHz data transfer modesWith ALT ADDRESS pin high, 7 bit I2C address is 0x1D,followed by R/W bitWith ALT ADDRESS pin low, 7 bit I2C address is 0x53,followed by R/W bit

Configuring ADXL345(Writing Appropriate control worlds)List of registers to be modified to configure accelerometer to detect fall:1.THRESH_ACT (Activity Threshold)2.THRESH_INACT(Inactivity Threshold)3.TIME_INACT(Inactivity Time)4.ACT_INACT_CTL (Activity control register)5.THRESH_FF (Free fall Threshold)6.TIME_FF (Free fall Time)7.INT_ENABLE8.INT_MAP9.INT_SOURCE

Configuring ADXL345(Writing Appropriate control worlds)

Fall Detection Algorithm(Acceleration Change Characteristics While Falling)Acceleration change characteristics for different types of motions

Fall Detection Algorithm(Acceleration Change Characteristics While Falling)Acceleration change characteristics for accidental fall

Fall Detection Algorithm(Acceleration Change Characteristics While Falling)Four critical characteristics that has to be met for an event to be asserted as fall1.Start of fall Weightlessness (FREE_FALL_INTERRUPT)2.Impact Large shock (ACTIVITY INTERRUPT)3.Aftermath Motionless(INACTIVITY INTERRUPT)4.Comparing before and after Change in orientation (Difference between Sampling data) Algorithm Flowchart

Problem that impeded project progressMismatch of rail-to-rail swings between ADXL345 and ATmega32 ATmega32 and ADXL345 are biased with 5V power supply designed using 9V battery and IC7805(5V regulator)Further,ADXL345 chip has on board 3.3V regulator This Caused rail-to-rail mismatch which took long time to spot

Energy Harvesting ModulePZT patches arent available for developing in-sole energy harvesting moduleAs proof of concept , using the available piezo crystals, 1ft*1ft array is developed.It has total of about 16 piezo crystals In each row, the sensors are in series and each row itself is connected in parallel with other rows

Energy Harvesting Module

Piezo Harvester Testing

Overall AFD System