FOOTSTEP POWER GENERATION BY PIEZOELECTRIC TRANSDUCER NAME ENROLLMENT NO SIMRAN SINHA 510615078 RISHA 510615025 NIKHIL PRIYADARSH 510615022 AVIK DEY 510615021 SHAMIK BOSE 510615023 SOURADEEP SAHA 510615024 ARNAB JANA 510615089

HISTORY The word “Piezo” is basically meant for pressure. The piezoelectric effect was discovered by Jacques and Pierre curie in 1880.They found that pressure applied to a quartz crystal creates an electric charge in the crystal and termed this phenomenon as direct piezoelectric effect(electricity from applied stress). Later they also verified an electric field applied to the crystal leads to a deformation of the material; inverse piezoelectric effect. In the subsequent century, research has been performed into the development of materials with improved piezoelectric properties ,enabling commercial utilization of the piezoelectric phenomenon.

PIEZOELECTRIC TRANSDUCER AS ALTERNATE ENERGY SOURCE At present, electricity has become a lifeline for human population. Its demand is increasing day by day. Modern technology needs a huge amount of electrical power for its various operations. Electricity production is the single largest source of pollution in the whole world. At one hand, rising concern about the gap between demand and supply of electricity for masses has highlighted the exploration of alternate sources of energy and its sustainable use. Accordingly, it is an objective of the present invention to provide a method of electrical power generation from this ever increasing human population that does not negatively impact the environment. This technology is based on a principle called the piezoelectric effect, in which certain materials have the ability to build up an electrical charge from having pressure and strain applied to them.

Harvesting of energy which means energy is already available, but is going to waste if not utilized. Embedded piezoelectric material can provide the magic of converting pressure exerted by the moving people into electric current. We have only about 25 years of oil reserves and 75 –100 years of coal reserves. Resort to measure beginning of coal in thermal electric stations to serve the population would result in global elemental change in leading to worldwide drought and decertification. So, we have to think something new. We have to think of non-renewable source of energy. In this new way of power generation can be done as there is no power from the mains and there is less pollutions from this source of energy

PIEZOELECTRIC TRANSDUCER WORKING A transducer can be anything which converts one form of energy to another. Piezoelectric material is one kind of transducers. We squeeze this material or we apply force or pressure on this material it converts it into electric voltage and this voltage is function of the force or pressure applied to it. The material which behaves in such a way is also known as piezoelectric sensor.

Piezoelectric transducer consists of quartz crystal which is made from silicon and oxygen arranged in crystalline structure (SiO2). Generally, unit cell (basic repeating unit) of all crystal is symmetrical but in piezoelectric quartz crystal it is not. Piezoelectric crystals are electrically neutral. The atoms inside them may not be symmetrically arranged but their electrical charges are balanced means positive charges cancel out negative charge. The quartz crystal has unique property of generating electrical polarity when mechanical stress applied on it along certain plane. Basically, there are two types of stress. One is compressive stress and other is tensile stress. When there is unstressed quartz no charges induce on it. In case of compressive stress, positive charges are induced in one side and negative charges are induced in opposite side. The crystal size gets thinner and longer due to compressive stress. In case of tensile stress, charges are induced in reverse as compare to compressive stress and quartz crystal gets shorter and fatter.

Piezoelectric transducer is based on principle of piezoelectric effect Piezoelectric transducer is based on principle of piezoelectric effect. The word piezoelectric is derived from Greek word piezen, which means to squeeze or press. Piezoelectric effect states that when mechanical stress or forces are applied on quartz crystal, produce electrical charges on quartz crystal surface.

Theory The rate of charge produced will be proportional to rate of change of mechanical stress applied on it. Higher will be stress higher will be voltage. One of the unique characteristics of piezoelectric effect is that it is reversible means when voltage is applied to them ,they tends to change dimension along certain plane i.e. quartz crystal structure is placed into electric field, it will deform quartz crystal by amount proportional to strength of electric field. If same structure is placed into an electric field with direction of field reversed, the deformation will be opposite. Quartz crystal becomes longer due to electric field applied.

Quartz crystal becomes shorter due to electric field applied in reversed direction. It is self generating transducer. It does not require electric voltage source for operation. The electric voltage produced by piezoelectric transducer is linearly varies to applied stress or force. Piezoelectric transducer has high sensitivity.

EQUIVALENT CIRCUIT A piezoelectric transducer has very high DC output impedance and can be modeled as a proportional voltage source and filter network. The voltage V at the source is directly proportional to the applied force, pressure, or strain. The output signal is then related to this mechanical force as if it had passed through the equivalent circuit. A detailed model includes the effects of the sensor's mechanical construction and other non-idealities. The inductance Lm is due to the seismic mass and inertia of the sensor itself. Ce is inversely proportional to the mechanical elasticity of the sensor. C0 represents the static capacitance of the transducer, resulting from an inertial mass of infinite size. Ri is the insulation leakage resistance of the transducer element. If the sensor is connected to a load resistance, this also acts in parallel with the insulation resistance, both increasing the high-pass cutoff frequency.

Piezo Sensor Array Construction: The array consists of 8 parallel branches each branch containing two piezoelectric transducers connected in series. The lab report of one branch(2 piezos in series) gives an output of approximately 5V terminal voltage and a short circuit current of 25uA

Output Voltage Waveform Equivalent Circuit

The foot-board has 16 piezoelectric transducers fit on the base. The upper surface of the foot-board has 16 screws fit downward facing the piezo sensors. When someone steps on the board all the piezo sensors come in Contact with the screws at once, thus a uniform pressure is applied In all the piezos.

REGULATOR CIRCUIT In maintain is the polarity for the output generated to be always positive (+ VE), the regulator circuit and multiplier circuit are needed as shown in the figure. Both circuit function as cut the negative charge and as result the voltage produced is stable. The negative voltage is not required because the circuit function is for direct current (DC) mode. The regulator circuit and multiplier circuit also used as to obtain a stable output voltage. If the output voltage is not stable, the main goal to store the generated voltage to battery may not be function is properly because the circuit will not going to operate during the unstable voltage. The output on the regulator circuit and multiplier will be connected directly to the rechargeable battery as temporary storage and 2.4 Volts rechargeable battery is used for it.

This battery used is to store the voltage as temporary as to support the main storage need to stabilize the voltage to supply. With the charge stored in the battery; 2.4 Volts will be used to charge a main battery as rechargeable batteries 12 Volts. To charge the battery, the converter circuit is used to increase the voltage from the 2.4 Volts up to 12 Volts. Regulator circuit

APPLICATIONS: POWER GENERATING SIDEWALK: Charging pads under the cross walk collect energy from the vibrations. Then, piezoelectric charging panels channel energy to lithium ion batteries which can be used further. GYMS AND WORKPLACES: At workplaces, piezoelectric crystals can be laid in the chairs for storing energy. Vibrations caused from machines in the gyms can also be used for power generations through piezoelectric sensors. Power generating sidewalk

MOBILE KEYPADS AND KEYBOARDS: Crystals can be laid down under keys of mobile unit and keyboard. For every key pressed vibrations are created. These vibrations can be used for charging purposes. POWER GENERATING BOOTS OR SHOES: We can use piezoelectric sensors in the shoes which can produce energy which can be stored in the battery. FLOOR MATS: Series of crystals can be laid down below the floor mats, tiles and carpets of the dance club or big railway stations. When mob uses the dance floor or the railway station, an enormous voltage is generated. These energy can be used. Piezoelectric sensors in shoe Piezoelectricity in dance floor

ADVANTAGES AND DISADVANTAGES: Unaffected by external electric field. They cannot be used for truly static measurements. Pollution free. Can pick up stray voltages in connecting wires. Low maintenance. Crystal is prone to crack if overstressed Easy replacement of equipment. May get affected by long use at high temperature.

We can use this method in IIEST, Shibpur also for power generation We can use this method in IIEST, Shibpur also for power generation. We can install piezoelectric sensors on the floors, on the playgrounds. This can give rise of huge amount of non-renewable energy which can further use in the college as electricity. Hope one day we can do that.

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