Body sensor networks are rising popular in healthcare, sports, military and security. However, the power supply from conventional batteries is a key for the development of body condition monitoring. Power harvesting from human movements to wearable or implantable devices is a guaranteed alternative. This paper presents an energy harvesting from shoe by converting foot-strike energy into electric power. An energy harvester using airflow to harness human motion energy from footsteps is used for a portable health monitor. An air bladder-turbine is designed to convert the footstep of human motion into electrical energy. The bladders are embedded in shoes to induce airflow from foot-strikes. The turbine is employed to generate electrical energy from airflow. A prototype was developed and tested to generate energy to monitor health with the use footsteps from a person. The harvested energy was then regulated and stored in a power management circuit energy was then regulated and stored in a power management circuit.
Keywords – Power generation circuit, Arduino.
I.INTRODUCTION
Wearable and portable devices, including smart watches, activity trackers and wearable cameras, are increasingly popular to enhance the convenience and quality of our lives, but the batteries for these devices require frequent recharging or replacement, which creates other types of inconvenience. There are massive energy sources from the human body, such as exhalation, arm motion, body heat and footfalls, in which the energy is readily harnessed; otherwise the energy is wasted. Energy harvesting from human motion to power these devices can be a potential solution to make these devices autonomous.
Power harvesting from human motion has been explored for decades. However, due to the low frequency and random excitation of human motion, the energy collected is generally insufficient for general electronic devices. Recently, more work has been conducted to further address the issues and to increase the power density of harvesters. Pillatsch et al. presented a rotating piezoelectric energy harvester for upper motion of the body. Frequency up-conversion, used to increase the excitation frequency and to enhance the output power, was achieved by magnetic plucking of a piezoelectric beam using a rotating magnet ascend on a pendulum structure. Xu and Kim demonstrated a bi-stable piezoelectric harvester for low-g and low-frequency applications. A buckled beam with bi-stability was fabricated using the residual stress generated during the fabrication process. The device has a broad operating bandwidth and a low excitation requirement, which is suitable for harvesting energy from human motion. More details about the advances in this field are summarized in several review papers.
Among all energy sources from human motion, footstep motion has the highest potential energy, but the low motion frequency and the limited vertical deformation of shoes make energy harvesting from footsteps more demanding. Different mechanisms have been investigated to address these issues, such as gear trains or frequency up-conversion to increase the excitation frequency, a rotary arm or a trapezoid-shaped slider to generate rotation from shoe distortion. However, these devices still have the issues of complication, high weight and high cost.
In this paper, an air bladder-turbine energy harvester is presented for footstep energy harvesting. It has the advantages of light weight, simple structure, and potentially low cost. The design and optimization process of the turbine is discussed in the paper. A framework was tested with footsteps from a 65 kg person. The power collected from footstep motion was regulated and stored in a commercial power management circuit and eventually used to power a fitness tracker in a smart sneaker
.
II.EXISTING MODEL
The main objective of power generation through footsteps using piezoelectric material is that we can obtained while walking on footpaths, stairs, plate forms and these can be install specially in the highly populated areas. The power was obtained with the help of the piezoelectric material which converts mechanical energy into electrical energy.
III.PROPOSED MODEL
The paper presents a power harvester from shoe converting foot-strike energy into power that can be used in portable devices. An air-pumped turbine system is developed and the low frequency of human motion that impede harvesting energy from this source. The air pump is used to change the vertical foot-strike movement into airflow. The generated airflow from air bladder passes through the miniaturized wind turbine whose transduction is realized by an electromagnetic generator. Energy is withdraw from the generator with a higher frequency than that footsteps, raising the output power of the device. The turbine casing is specifically designed to enable the device to operate continuously with airflow in both directions. Health is an important factor on consideration due to high level stress in working areas. So in addition to the power generation from heel-strike temperature and heartbeat of the human can be detected using temperature senor and heart beat sensor.
The proposed model consist of
• Arduino
• Temperature Sensor
• Heart beat Sensor
• Mems Sensor
• 16X2 LCD
• Foot step power generation model
Fig.1 BLOCK DIAGRAM
IV.FOOTSTEP ENERGY HARVESTER
The power supply from conventional batteries is a key bottleneck for the development of body condition monitoring. Energy from human locomotion to power wearable or implantable devices is better alternative. This paper confer energy harvester from airflow to tack human motion energy from footsteps. An air bladder-turbine is designed to convert the footstep motion into electrical energy. The bladders are embedded in shoes to induce airflow from foot-strikes. The turbine is engaged to generate electrical energy.
V.DESIGN AND OPERATING PRINCIPLE
The schematic of the airflow energy harvester consists of an air bladder, a miniaturized ducted air turbine, a DC generator and a power management circuit. The air bladder is embedded in the shoe cushion. When a foot strike is applied on the air bladder, it converts the linear deformation of shoes into airflow. The direction of airflow is regulated by two check valves so that the airflow direction in the whole system is unidirectional all the time. The generated airflow actuates the turbine, and the electrical energy is produced by a DC generator attached to the turbine rotor. The harvested energy is then managed and store in a super capacitor by an off-the-shelf circuit for sensing applications.
Fig.2 Schematic diagram of the footstep motion energy harvester using airflow turbine.
VI.WORKING OF CIRCUIT
LM35 Temperature Sensor
The LM35 series are precision integrated-circuit LM35 temperature sensors, whose output voltage is linearly proportional to the Celsius (Centigrade) temperature. The LM35 sensor thus has an advantage over linear temperature sensors calibrated in ° Kelvin, as the user is not required to subtract a large constant voltage from its output to obtain convenient Centigrade scaling. The LM35 sensor does not require any external calibration or trimming to provide typical accuracies of ±¼°C at room temperature and ±¾°Cover a full -55 to +150°C temperature range. Low cost is assured by trimming and calibration at the wafer level. The LM35’s low output impedance, linear output, and precise inherent calibration make interfacing to readout or control circuitry especially easy.
Fig 3.LM35
It can be used with single power supplies, or with plus and minus supplies. As it draws only 60 µA from its supply, it has very low self-heating, less than 0.1°C in still air.
Table 1.Parameter of Temperature Sensor
PARAMETERS VALUE
Supply Voltage 4V
Quiescent Current 56 uA
Temperature(minimum) -40,-55,0 Deg Celsius
Temperature(maximum) 100,110,150 Deg Celsius
The LM35 is rated to operate over a – 55° to +150°C temperature range, while the LM35C sensor is rated for a -40° to +110°C range (-10° with improved accuracy). The LM35 series is available packaged in hermetic TO-46 transistor packages, while the LM35C, LM35CA, and LM35D are also available in the plastic TO- 92 transistor package. The LM35D sensor is also available in an 8-lead surface mount small outline package and a plastic TO-220 package.
VII.HEARTBEAT SENSOR
The sensor consists of a super bright red LED and light detector. The LED needs to be super bright as the maximum light must pass spread in finger and detected by detector. Now, when the heart pumps a pulse of blood through the blood vessels, the finger becomes slightly more opaque and so less light reached the detector.
With each heart pulse the detector signal varies. This variation is converted to electrical pulse. This signal is amplified through an amplifier which outputs analog voltage between 0 to +5V logic level signal. It works on the principle of light modulation by blood flow through finger at each pulse.
Table 2.Parameters of Heart Beat Sensor
PARAMETER
VALUE
Operating Voltage
+5 V DC Regulated
Operating Current
100 mA
Output Data Level 5V TTL Level
Heart Beat Detection Analog Out
Light Source 660 nm super red LED
Detector Photo Diode
VIII.LCD 16×2
It is called Liquid Crystal Display. There is a use of 16×2 characters LCD. This will be connected to microcontroller. The job of LCD will be to display all the system generated messages coming from the controller. LCD will provide interactive user interface.
IX.CONCLUSION
Proposed Infant Monitoring System is an inexpensive and simple to use, which can be used without an external power source. We have analyzed a portable health monitoring system for monitoring the temperature and heartbeat of humans. Any abnormalities in health conditions are specified through LCD. The hardware is implemented and the output is studied.