variable capacitance
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Micromachines ◽  
2022 ◽  
Vol 13 (1) ◽  
pp. 133
Author(s):  
Hua-Ju Shih ◽  
Kuo-Ching Chen

Energy harvesters are devices that accumulate ambient vibrational energy from the environment, and for the time being, variable capacitance is the most widely used mechanism. Various designs were proposed to increase the power of such devices, and in particular, the interdigitated electrode (IDE) pattern is the mainstream. Nevertheless, most IDE designs focus merely on the parallel-type vibrations of electrodes. In this study, the performance of a novel harvester, which combined circular membrane and interdigitated ring electrodes (IRE), was investigated. This design allows the device to collect energy from the rotational structure motions of electrodes through the vibrating membrane. Besides, the circular structure provides a dense capacitive arrangement that is higher than that of the arrangement obtained using regular rectangular chips. The IRE diagram is composed of many capacitive rings, each of which harvests vibrated energy simultaneously. Three gaps (1, 10, and 100 μm) of the ring are investigated for the first four vibrational modes of the membrane to understand the effect of energy output. It is found that the energy outputs are approximately the same for the three gaps; however, rings with a wider gap are easier to manufacture in MEMS.


2022 ◽  
Author(s):  
Seyed Hossein Daneshvar ◽  
Mehmet Rasit Yuce ◽  
Jean-Michel Redouté

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
M.M.P.M Fernando ◽  
D.D.A Gamini ◽  
J.A.L Naveendra

Electricity is the primary source of power in most countries including Sri Lanka, and saving or minimising the waste of it has become crucial in facing the world power crisis. Electrical power is wasted in various ways including reactive power waste due to induction and capacitance of appliances, and standby power loss. These two contribute most to the waste. This paper focuses on reducing the reactive power waste of inductive electrical appliances commonly used in home and office by increasing the power factor. An attempt was made to reduce the power waste of inductive electrical appliances by connecting a capacitor bank with a variable capacitance in parallel with the appliance. Optimal capacitance and the power factor are determined using the capacitor bank. Results indicate about 30 percent of power saving could be achieved for fluorescent tube lamps using a power factor correction. A maximum power factor of 0.93 is achieved at the capacitance value of 2.99 F. It is not possible, by this method, to increase the power factor of more capacitive equipment such as CFL bulbs and ceiling fans. In this case, power minimisation could be tried connecting inductors in parallel with the equipment. Power factor and power consumption of home electrical appliances were measured for advising the general public of high power consuming equipment, especially in stand-by mode. To attain a further reduction of power waste it is proposed to measure inductance, capacitance and resistance of appliances using Hendry, Farad and Ohm meter. Total impedance can then be calculated and the power waste could be minimised using appropriate capacitors and/or inductors. Keywords: reactive power, power factor, power waste, reactive power waste, power minimisation


2021 ◽  
Vol 3 (4) ◽  
Author(s):  
Dileep Dwivedi ◽  
Manoj Kumar ◽  
Vandana Niranjan

AbstractThis paper presents a low-power, wide tuning range CMOS voltage-controlled oscillator with MCML (MOS current mode logic) differential delay cell. Voltage controlled oscillator (VCO) circuit is designed in TSMC 0.25 μm CMOS process. To achieve the broad frequency range concept of variable capacitance is employed in the proposed VCO circuit. Source/drain tuning voltage (Vtune) and body bias voltage (Vb) of I-MOS varactor are used to achieve variable capacitance at different I-MOS varactor widths (W). The dual control voltage of I-MOS varactor results in a tuning range from 0.528 GHz to 2.014 GHz. VCO's figure of merit (FoM) is 152.13 dBc/Hz with phase noise of −93.77 dBc/Hz at 1 MHz offset from the oscillation frequency. The proposed VCO dissipates maximum power of 3.127 mW.


Author(s):  
Seyed Hossein Daneshvar ◽  
Mohammad Maymandi-Nejad ◽  
Mehmet Rasit Yuce ◽  
Jean-Michel Redoute

2020 ◽  
Vol 10 (6) ◽  
pp. 6695-6705

The model of this work represents electrophysiological occurrences with a combination of some phospholipids such as POPC and galactocerebroside lipid bilayers as variable capacitors. The quantum effects of different thicknesses in the mixed membranes of GalC/POPC, Galc/ POPE, and Galc/DPPC have also explicitly been investigated. It is shown that quantum effects can appear in a small region of free spaces within the membrane thickness due to the number and type of lipid's layers. In the presence of external factors such as protein transmembrane and myelin proteins as a resistance, the forces can influence the state of the membrane, which results in a variable capacitance behavior. This allows introducing a capacitive susceptibility which can be resonating with the self-induction of helical coils in myelin proteins, the resonance of which is the main reason for various biological pulses.


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