Projects:2016s2-245 RFID in a Light Bulb - Revision history

A1673134: /* Conclusion */

2017-06-05T23:34:01Z

‎Conclusion

A1673134: /* Results */

2017-06-05T23:33:06Z

‎Results

A1673134: /* Theory */

2017-06-05T23:30:03Z

‎Theory

A1674122 at 07:36, 5 June 2017

2017-06-05T07:36:58Z

A1673134: /* Theory */

2017-06-05T04:56:22Z

‎Theory

A1674122 at 11:32, 29 May 2017

2017-05-29T11:32:52Z

A1674122: /* background */

2017-05-29T11:16:58Z

‎background

A1674122 at 11:14, 29 May 2017

2017-05-29T11:14:42Z

A1674122 at 11:10, 29 May 2017

2017-05-29T11:10:35Z

A1674122 at 11:08, 29 May 2017

2017-05-29T11:08:51Z

@@ Line 176: / Line 176: @@
 == '''Conclusion ''' ==
 In this paper, a liquid-based electrostatic energy harvester with electret in low frequency and movement in random directions is designed and investigated. Under various environments of non-periodic ambient motion. The designed electrostatic energy harvester produces a capacitance variation ratio of 41.25, and the maximum power is calculated theoretically of 3.31µw. The output voltage is 40mV when energy harvester is mounted on stepper motor, the output voltage is 500mV with lower speed and the maximum output voltage can achieve 1.9V with high speed hand shaking. in addition, the cellulose acetate barrier layer is presented in this paper to address the discharge issue of electret which affects the performance significantly in liquid-based electret kinetic energy harvester and makes it stably operates. The electret energy harvester can achieve a good performance and show promising future as a sustainable energy generation for portable devices.
 == '''Project management ''' ==

← Older revision		Revision as of 23:33, 5 June 2017
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	Therefore, in another condition, under the random vibration with slower hand-shaking, and try to control the range of vibration, there is a lower output voltage. The reason that the output voltage is inconsistent, because there are many factors so that it cannot be quantized, and be measured.		Therefore, in another condition, under the random vibration with slower hand-shaking, and try to control the range of vibration, there is a lower output voltage. The reason that the output voltage is inconsistent, because there are many factors so that it cannot be quantized, and be measured.
		+
		+	The selected output voltage of LTC3588 is 1.8V and because there is noise in our testing environment which was shown in above figure the recorded result is acceptable. But the fluctuation should not appear in the result. The ideal result should like a straight line. In order to explore with this problem, different resistors were used to connect output to check what will happen in the voltage. After a few group test, the regular variance is that the maximum will not change but the minimum is pulled down deeper. when the voltage is more than 20V the output voltage will have negative part which is obvious wrong. Furthermore, according to datasheet, some resistor is connected to PZ1 and PZ2 pin to limit the current in some application. Because the current which comes from voltage generator is unknow the multimeter is used to test the current of voltage generator.
		+
		+	However, the absolute maximum ratings of Ipz1 and Ipz2 is 0.05A which is less than all of current which comes from voltage generator. Besides above limitation, the absolute maximum continuous current is 0.005A therefore the protective resistor is necessary to connect with input pin. When the current limiting resistor whose value is approximate 800Ω is series to the input pin, the output voltage waveform is a straight line which is 1.84V. whatever the input voltage is the output will be stable and as same as the
		+
		+	The MSP430 microchip is the one which is our propose to drive. The working current and voltage of this chip is 1.8V and 230μA therefore the alternative resistor of this chip is equal to voltage divided by current. The 8KΩ resistor will be used to substitute the microchip. When the 10V peak to peak sine waveform input signal is putted into the PZ1 and PZ2 pin the output voltage is shown in figure 30.
		+
		+
		+	The maximum voltage from output is 1.96V and minimum voltage is 1.04V. the output voltage dropped from half within a 200ms period. the reason of this phenomenon is output resistor was depleting the energy so output voltage will drop and pull up again due to new energy. when the input voltage was increased from 10V to 20V, the minimum voltage increased a little and the duty cycle of voltage increased slightly. The number of variation between maximum and minimum of output voltage from 0.68V to 1.04V. besides the voltage, if we increased the frequency of the input voltage the output will change in same way when we changed the input voltage but it isn’t apparent.

	== '''Conclusion ''' ==		== '''Conclusion ''' ==

@@ Line 119: / Line 119: @@
 [[File:3.PNG|200px|thumb|bottom|Schematic diagram of corona charging]]
 Corona polar method is that the needle electrode which is added with high voltage discharges the corona. A large number of charged ions produced by corona discharge are driven to the anode at high speed under the applied electric field. The sample near the anode will be charged by charged ions and charged by the method. When the surface of the sample when accumulated to a layer of charged ions, the charged ions and the surface of the sample will undergo charge and energy transfer. Under certain conditions, the charge exchange between charged ions and sample surfaces achieves dynamic equilibrium. However, after this method of charging, the surface charge of the electret exhibits a bell-shaped distribution that the central surface potential of the electret is significantly higher than the surrounding surface potential.
 == '''Results ''' ==

@@ Line 2: / Line 2: @@
 == '''project team''' ==
-'''Academic Supevisors'''
+==='''Academic Supevisors'''===
 Dr. Said Al-Sarawi
@@ Line 8: / Line 8: @@
 Dr. Damith Ranasinghe
-'''team members'''
+==='''team members'''===
   ZEYU WANG
   RAN YE
@@ Line 20: / Line 20: @@
 the development of a permanent power source for self-sustainable wireless sensor networks is essential in order to reduce the maintenance costs and increase the operational time of sensor nodes. Accordingly,over the past decade researchers have actively studied various energy harvesters that generate power form sources such as ambient light, heat, motion, electromagnetic waves and other unused sources of energy. One energy harvester driven by ambient vibrations has attracted special attention because it can easily gain energy form sources of movement such as human physical motion. This project states a liquid-based electrostatic energy harvester that converts the mechanical energy of human-motion-induced vibrations to electrical energy.
-'''Aims'''
+==='''Aims'''===
 This paper presents a kinetic energy electrostatic harvester with electret as voltage source and liquid-based structure, which converts the mechanical energy in a low working frequency vibration to electrical energy. Moreover, it addresses the discharge issue of electret to improving charge storage stability of electrets in liquid-based environment. Extending from the theoretical research, the prototype of energy harvester is fabricated in proposed structure and is tested its performance in desirable low frequency range. In addition, the high efficiency circuit is necessary in energy conversion that is as important as the capacitor part.
-'''Motivation and Significance'''
+==='''Motivation and Significance'''===
 Energy harvesting technologies present a developing self-sustainable power source to replace conventional batteries in portable and low consumable application such as autonomous wireless sensor nodes, low power consumption electronic devices, and implantable medical equipment. As an emerging inexhaustible power source, there is significant developing potential in energy harvesting from ambient energy sources. It is different from piezoelectric harvesters and electromagnetic harvesters, which are mostly designed in a resonant mode and are driven in a relatively high frequency range. For instance, the spring structures are used in energy harvester should overcome their natural frequency to excite the system operation. Therefore, it is difficult to use in a low frequency range.  Additionally, the electrets discharge reason limit their usage when it contacts with liquid. The polymer barrier layer is proposed to solve its discharge issue.
@@ Line 89: / Line 89: @@
 In this paper, through different ways to assist develop the energy harvester, the theoretical approach of capacitor, the investigation of each component of material, the charging method of electret, design software and the stepper motor will be stated below.
-'''The theoretical approach of capacitor'''
+==='''The theoretical approach of capacitor'''===
-The energy harvester has many aspects of characteristic perform, and the varying processing of inner capacitor is complex. Therefore, the process is simplified to calculate the consequences. When the capacitor moves by external motions, the permittivity distribution varies within the capacitive structure cause a large capacitance variation, the large capacitance variation is considered as the capacitance ratio which is equal to maximum capacitance over minimum capacitance (C_ratio=C_max/C_min ). The capacitance ratio concept is more than important in energy harvesting because it can be used in analysing varying charge volume, and in generated electrical energy. The energy power of capacitor commonly is E=1/2 CV^2. Because of varying capacitance, the output power of energy harvester is ∆E=1/2 (C_ratio-1) C_max V^2 in discharge process. To assume the operation frequency is 1 Hz, there are 3.31µw output power generated in one cycle.
+The energy harvester has many aspects of characteristic perform, and the varying processing of inner capacitor is complex. Therefore, the process is simplified to calculate the consequences. When the capacitor moves by external motions, the permittivity distribution varies within the capacitor structure cause a large capacitance variation, the large capacitance variation is considered as the capacitance ratio which is equal to maximum capacitance over minimum capacitance (C_ratio=C_max/C_min ). The capacitance ratio concept is more than important in energy harvesting because it can be used in analysing varying charge volume, and in generated electrical energy. The energy power of capacitor commonly is E=1/2 CV^2. Because of varying capacitance, the output power of energy harvester is ∆E=1/2 (C_ratio-1) C_max V^2 in discharge process. To assume the operation frequency is 1 Hz, there are 3.31µw output power generated in one cycle.
-'''The investigation of each component of material'''
+==='''The investigation of each component of material'''===
 The material of components is as well as important in design. Because the different material has different characteristic and different state of art, the material chosen needs to consider the cost and to guarantee the perform of capacitor. There are four kinds of material is chosen in this capacitor, namely, cellulose acetate tape, PTFE and Copper (Cu). The PTFE is material of the cavity, cellulose acetate tape is used as polymer barrier, PTFE is the material for electret, and the Cu is considered as the metal plates to the electrode.
@@ Line 113: / Line 113: @@
 [[File:17.png|200px|thumb|bottom|electrets from the state of the art]]
-'''The charging method of electret'''
+==='''The charging method of electret'''===
 Corona charging method is one of the most widely used method in making electret. It has the advantage that the charging voltages are controllable in corona charging process. In addition, the surface charge electret can be easily obtained in room temperature.
@@ Line 147: / Line 147: @@
 == '''Project management ''' ==
-'''Work Breakdown'''
+==='''Work Breakdown'''===
 The content of project consists of two parts which one is capacitor prototype and another is circuit structure. The key task in first stage is to analyse and device the capacitor prototype and circuit structure. However, the function of circuit is to transfer and store the outcome power of capacitor in circuit. In addition, the energy stored in circuit can be considered as an energy supplier. The output power of capacitor is essential data for circuit design. Therefore, the analysis of capacitor is important fundamental for further studying.
-'''Timeline'''
+==='''Timeline'''===
 The original plan is designed to manage time plan, and control and limit the process of project. However, there is some difference in project execution and original plan, because the new knowledge gap generated or the new challenge occurred. When these difficulties met in process, the original plan might need to be delayed or changed to meet new requirements.
@@ Line 157: / Line 157: @@
 [[File:9.png|200px|thumb|bottom|Gantt chart for time management]]
-'''Task allocation'''
+==='''Task allocation'''===
 The energy harvester is allocated into two parts which one is capacitor and another charge pump. These two parts is importantly equally. I am responsible for capacitor part which need to analyse and design capacitor, to build and test a prototype to compare to presented electromagnetic energy harvester. and my team mate is responsible for charge pump circuit.
-'''Risk management'''
+==='''Risk management'''===
 Most of this process is no especially risk. However, the conducting liquid chosen in this project is DMF. DMF has Health hazard which has invasive ways: inhalation, eat, percutaneous absorption. It has Acute toxicity, DMF is Inhaled 30 ~ 60 PPM, gastrointestinal symptoms, liver meritorious service is abnormal, there are jaundice, uric bravery former increases, proteinuria; Inhaled 10 ~ 20 PPM (sometimes 30 PPM), headache, loss of appetite, nausea, hepatic function and electrocardiogram (ecg) is normal; Inhaled 49 mg/m3 x 5.1 ~ 3 years, god failure syndrome, low blood pressure, liver function change. In addition, its dangerous characteristic: flammable, high heat, open flame or contact with oxidant, has caused the risk of burning explosion. It can react with sulfuric acid, fuming nitric acid fierce, even an explosion. And halide severe reactions can occur (such as carbon tetrachloride). Therefore, it should take the right protective measures. if it leaks few: with sand or other incombustible material adsorption or absorption. It can also use a lot of water to rinse, wash water diluted into the wastewater system. Additionally, eye protection: wear chemical safety goggles; Body protection: wear chemical protective clothing; Hand protection: wear rubber gloves; Other: no smoking on site. Take shower and change clothes after work.
-'''Management Strategy'''
+==='''Management Strategy'''===
 The management strategies used in whole process of project is the project scope management which is used to define, to validate and to control the project, the project time management which is used to plan and manage the project schedule, the risk management which is to protect the safety of facilities and personnel and the project communication management which is vital in group communication and to promote effectively operation of project.

← Older revision		Revision as of 04:56, 5 June 2017
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	Finally, the choice of conductive liquid is gallium (Ga). It is one kind of liquid metal that the melting point is under 29.8℃, the others are mercury that is the only liquid metal under room temperature and pressure and caesium that the melting point is under 28.4℃. even though the melting point of gallium is highest among these metals, the mercury and caesium are both toxic. Therefore, the gallium is the safest choice.		Finally, the choice of conductive liquid is gallium (Ga). It is one kind of liquid metal that the melting point is under 29.8℃, the others are mercury that is the only liquid metal under room temperature and pressure and caesium that the melting point is under 28.4℃. even though the melting point of gallium is highest among these metals, the mercury and caesium are both toxic. Therefore, the gallium is the safest choice.
		+
		+	Linear technology company et al (2010) [5] proposed LTC3588-1 is an ultralow current power supply that is designed for energy harvesting. LTC3588 can interface directly with AC power source, rectify AC voltage waveform and store harvested energy. LTC3588 have lots of features which necessary for my project. The features are shown as follow:
		+	1. 950nA input quiescent current
		+	2. 450nA input quiescent current in UVLO
		+	3. The lowest operating voltage is 2.7V and highest operating voltage is 20V (even if the input voltage is higher than 20V)
		+	4. Low-loss full-wave bridge rectifier
		+	5. The limitation of output currents up to 100mA
		+	6. Four choices output voltage of 1.8V, 2.5V, 3.3V, 3.6V
		+	7. High efficiency hysteretic buck DC/DC
		+	8. Input protective shunt up to 25mA pull-down at Vin>=20V
		+	9. Small size 10-lead MSE packages
		+	1.1 Pin functions
		+	PZ1 and PZ2 (Pin1 Pin2): these two pins are input connection for electrostatic energy harvester element or another AC source.
		+	CAP (Pin3): it is an internal rail referenced to Vin, which will serve buck PMOS switch as gate drive. One 1uf capacitor should be connected between CAP and Vin. CAP pin should not be used as the external system rail.
		+	VIN (Pin4): rectified input voltage comes out from this pin. A capacitor be suggested to connect this pin as an energy reservoir and a supply for the buck regulator meanwhile the Vin voltage is clamped to 20V.
		+	SW (Pin5): it is switch pin for the buck switching regulator. A 10uh inductor is recommended to connect from SW to Vout.
		+	Vout (Pin6): A sense pin which is used to monitor the output voltage
		+	Vin2 (Pin7): internal low voltage rail to serve as gate drive for buck NMOS switch. The voltage that come from Vin2 is regarded as a logic high rail for output voltage. A 4.7UF capacitor should be putted between Vin2 and GND.
		+	D1 and D2 (Pin8 Pin9): output voltage selection Bit.
		+	GND (exposed pad pin 11): ground.

	== '''Theory ''' ==		== '''Theory ''' ==

@@ Line 1: / Line 1: @@
 == '''project team''' ==
@@ Line 39: / Line 38: @@
 In this capacitor, the electret and the covered film are considered as insulating layer. Through changing the liquid state, the inside structure of capacitor is changed when there is an external vibration. When the liquid occasionally contacts with the top insulating layer, the capacitance becomes large due to the air gap is eliminated. To be detailed, the inside structure of capacitor is changed from series capacitance to parallel capacitance. The value of capacitance is expressed as:
 [[File:7.PNG|200px|thumb|]]
-Capacitance initial is the minimum capacitance, capacitance excited is the maximum capacitance. ε1 is the permittivity of PTFE electret, ε2 is the permittivity of air, ε3 is the permittivity of Cellulose Acetate tape. The d1 is the thickness of PTFE, d2 is the thickness of air gap, d3 is the height of liquid, d4 is the thickness of Cellulose Acetate tape. S is the overlay area of the top and bottom plates, Sliquid is the contact area of the conducting liquid and the insulating layer.
+Capacitance initial is the minimum capacitance, capacitance excited is the maximum capacitance. ε1 is the permittivity of PTFE electret, ε2 is the permittivity of air, ε_3 is the permittivity of Cellulose Acetate tape. The d1 is the thickness of PTFE, d2 is the thickness of air gap, d3 is the height of liquid, d4 is the thickness of Cellulose Acetate tape. S is the overlay area of the top and bottom plates, Sliquid is the contact area of the conducting liquid and the insulating layer.
 As this formula expressed, the electrical energy generation is determined by the capacitance ratio, the maximum capacitance and the electret voltage.
@@ Line 77: / Line 76: @@
 The material of components is as well as important in design. Because the different material has different characteristic and different state of art, the material chosen needs to consider the cost and to guarantee the perform of capacitor. There are four kinds of material is chosen in this capacitor, namely, cellulose acetate tape, PTFE and Copper (Cu). The PTFE is material of the cavity, cellulose acetate tape is used as polymer barrier, PTFE is the material for electret, and the Cu is considered as the metal plates to the electrode.
 PTFE commonly referred to as non-stick coating or easy to clean material. This material has the acid alkali resistance of various organic solvent resistance characteristics, almost insoluble in all solvents. At the same time, PTFE has the characteristics of high temperature resistance, low coefficient of friction of it, so can make lubrication, also become the ideal of easy to clean the pipe inner coating.
@@ Line 88: / Line 85: @@
 Therefore, cellulose acetate constitutes as the polymer barrier layer to significantly improve charge storage stability of electrets when conducting liquid directly contacts with electret interface.
 Gallium (Ga) is a kind of liquid metal and non- toxic, which is considered as an ideal conductive material but the melting point of gallium is 29.8℃. thinking of the safety, gallium is chosen as the conductive material instead of mercury.
@@ Line 96: / Line 90: @@
 [[File:4.PNG|200px|thumb|bottom|gallium (Ga)]]
-CYPOT is one of the most well-known electrets and the most used electrets in electret-based electrostatic energy harvester. Of course, there are many electrets can be used in the capacitor. To comprehensively consider the deposition method and the equipment which can be provided in available in laboratory, the maximum thickness, dielectric strength, permittivity and standard surface charge density. As shown in Table properties of some electrets. CYPOT is the optimum option in designed capacitor.
 [[File:17.png|200px|thumb|bottom|electrets from the state of the art]]

@@ Line 93: / Line 93: @@
 Gallium (Ga) is a kind of liquid metal and non- toxic, which is considered as an ideal conductive material but the melting point of gallium is 29.8℃. thinking of the safety, gallium is chosen as the conductive material instead of mercury.
 CYPOT is one of the most well-known electrets and the most used electrets in electret-based electrostatic energy harvester. Of course, there are many electrets can be used in the capacitor. To comprehensively consider the deposition method and the equipment which can be provided in available in laboratory, the maximum thickness, dielectric strength, permittivity and standard surface charge density. As shown in Table properties of some electrets. CYPOT is the optimum option in designed capacitor.
@@ Line 100: / Line 102: @@
 Corona charging method is one of the most widely used method in making electret. It has the advantage that the charging voltages are controllable in corona charging process. In addition, the surface charge electret can be easily obtained in room temperature.
 Corona polar method is that the needle electrode which is added with high voltage discharges the corona. A large number of charged ions produced by corona discharge are driven to the anode at high speed under the applied electric field. The sample near the anode will be charged by charged ions and charged by the method. When the surface of the sample when accumulated to a layer of charged ions, the charged ions and the surface of the sample will undergo charge and energy transfer. Under certain conditions, the charge exchange between charged ions and sample surfaces achieves dynamic equilibrium. However, after this method of charging, the surface charge of the electret exhibits a bell-shaped distribution that the central surface potential of the electret is significantly higher than the surrounding surface potential.
@@ Line 107: / Line 111: @@
 When there is no barrier layer for electret, the output voltage of energy harvester is extremely instable, it can achieve maximum voltage which is 5V from time to time. And due to the discharge issue of electret, it is apparent that the attenuation of output voltage starting to test. the electret can operate just for a while. Even though the output voltage is good, this method cannot be adopted. Therefore, the discharge issue is an obstacle that the energy harvester is in practice.
 Therefore, the cellulose acetate tape is put on the electret as the insulating layer to protect the electret from discharging. Firstly, the energy harvester is mounted on the stepper motor to test it under 10 Hz which is the highest frequency of our requirement. Under the opened-circuit, the energy harvester is directly connected with oscilloscope. The energy harvester moves in tilting direction. The maximum forward output voltage, which is shown, is 40mV, ant the maximum output backward voltage is -40mV. Ideally, the maximum forward output voltage should equal to the maximum backward output voltage. However,