Capacitance is the ability of a body to store an electrical charge

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Why different values of an unknown capacitor while calculating through formula and measuring with LCR meter?

I made a capacitive sensor which is concentric cylindrical where both the cylinders(electrodes of capacitive sensor) are actually non-inductive winding. When I calculated its value with only air as ...
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2answers
28 views

Combining decoupling capacitors for sensitive power requirements in LPDDR

I've been looking through a bunch of designs I found online on LPDDR2 interfacing. What's always confused me is the parallel decoupling capacitors. Why have so many vs just combining that to what you ...
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1answer
57 views

How MOSFET gate capacitances (Cgs, Cgd) are calculated?

I have read somewhere that the gate capacitance (Cgs, Cgd) of a MOS is calculated as below: Strong inversion: Cgs=(2/3)Cox.W.L + Cov Non-saturated: Cgs=Cgd=(1/2)Cox.W.L + Cov where Cov is ...
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57 views

how to determine the exact value of the capacitor for a particular package using the datasheet [closed]

how to determine the exact value of the capacitor for a particular package ? In normal case datasheet of the capacitor generally gives capacitor values withing wide ranges like 120 pF to 300 nF for a ...
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21 views

How to measure fast transient capacitance response

I would like to measure a fast transient capacitance response of a diode when switching from forward to reverse bias. There are commercial instruments available to do this, such as the Boonton 72 or ...
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2answers
148 views

What will increase output volume (dB) on a Piezo Transducer?

I need to achieve 110dB at 25khz from a Piezo Transducer. According to the datasheet, the resonant frequency of the Piezo is 25khz and at 10 vrms it will produce 110dB. I will be using an ...
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0answers
11 views

Duble use crystal speaker for capacitive touch sensing

I like to use a piezo crystal speaker to double as a capacitive proximity / touch sensor while not used for audio. The small speaker is directly driven by MCU digital pins. To accomplish this, I ...
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38 views

Supercap as dashcam memory backup

I'm working on a raspberry pi dashcam and have a few questions about using a supercap to provide ~10seconds of runtime to ensure the current file is correctly written to disc in case of power failure. ...
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2answers
106 views

What happens to current in a RC-battery circuit when you move plates with a square signal?

I use an RC circuit connected in series with a battery. I change the gap between plates of my air capacitor (2 paralleles plates, one fixe, the other one moving with an actuator) so as to change my ...
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22 views

How to extract complex permittivity from a CV measurement?

I can choose from the following measurements: Z, theta (impedance and phase angle) R + jX (resistance and reactance) Cp-Gp (parallel capacitance and conductance) Cs-Rs (series capacitance and ...
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29 views

Diffusion Capacitance: Forward Bias

Please see attached image. I'm struggling to understand how the book went from line 2 to line 3; it doesnt seem obvious how they did the differential. Thanks
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46 views

How were values of Vc(0+) and i(1.5ms) found?

I get that by applying source transformation, we get a (0.1*200=20 V) source but shouldn't 0.1 A current be divided into 50 ohm and 100 ohm resistance? Also why i=0 at t=1.5ms?
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1answer
28 views

Miller's Theorem - Input Capacitance

Please see attached image. I've become confused if the answer to this question, which uses Miller's Theorem is correct as it should not be a minus, rather it should be a plus. Please see my working ...
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0answers
27 views

Determine voltage limit from load capacitance limit?

I want to add a NTC thermistor (a.k.a. inrush current limiter, or ICL) to a circuit. But the manufacturer only specifies the following (and I'm giving sample values for the component I'm considering):...
3
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1answer
94 views

How long should 8, 1.5V batteries last for?

I purchased a GPS tracker from Amazon and instead of wiring it to the car battery I would like to simply attach my own power battery pack. I am a complete noob when it comes to electronics and I ...
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1answer
72 views

How must be real transistor model? [closed]

Transistors have some capacitance value. So where do i must put that capacitance when i want to draw real model of transistor. Also second question same about diodes? Can anyone draw simple real model ...
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38 views

Series Gate Resistor needed at low Capacitance?

even though this question has been answered before for various scenarios, I would like to ask for a generic advice. So I want to drive a certain resistive load from a microcontroller pin. Let MCU be ...
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2answers
91 views

Would the frequency of LED be equal to that of microcontroller

Suppose I have a simple LED driving circuit i.e. an LED and a resistor in series which is driven by a pin of a microcontroller. Now I set the frequency of this pin to say 1Khz, will the LED flash with ...
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1answer
23 views

Calculate capacitance i.a. via reactive power

The ampermeter of the following circuit shows 10A (AC) and the voltmeter 220V (AC). Furthermore its known that: $$ cos\varphi=\frac{2}{3} \\ f=50Hz $$ I calculated the following: $$ P=UIcos\...
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1answer
36 views

How to get the same output signal but with an increased capacitive load?

I'm designing a CMOS circuit of a VCO and it works perfectly fine when tested independently. Now when I cascade an other block like a divider to it, the output isn't the same as before. Rather its ...
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1answer
66 views

Will A Logarithmic Potentiometer Linearise A Capacitor Charge Curve?

I want to use a rising voltage on a capacitor to set more than one trigger points for events via comparators; that is when the voltage reaches a certain level, the comparator goes high. For ease I ...
3
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2answers
152 views

Choosing crystal, strangely narrow requirements in MCU datasheet?

I am making a prototype using the Atmel ATSAM4S2B microcontroller, but I am having trouble choosing a crystal. I need a 12MHz crystal to use the integrated USB module. The problem is, in the ...
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3answers
78 views

Does mutual capacitance increase for two positively charged plates when brought close?

My understanding is that any two charge carriers will exhibit what is known as mutual capacitance. That is, there is an amount of charge that can be stored between any two objects, which is called ...
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1answer
64 views

What happen if i connect the capacitors with few LED Strip in parallel?

I want to make my LED Strips which connected in parallel to dim out slowly. Therefore, i thought of using few capacitors (in parallel) to make this possible. if i"m using 12V batery as power supply ...
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1answer
58 views

I have this timer circuit. Push and release vs push and hold give me different times

I have a timer circuit which I slightly modified from the one in this link I have an image below of what my circuit looks like. My problem is this: When I push my start button and immediately let go,...
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2answers
50 views

Getting the numerical value of a capacitor's impedance

I understand that the impedance of a capacitor is \$\frac{1}{j\omega C}\$. For the circuit above, I have \$\frac{1}{Z_V} = \frac{1}{Z_{V1}} + \frac{1}{Z_{V2}} + j\omega C_V\$ and \$V_V = \frac{Z_V}{...
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1answer
84 views

Is it practical to measure an unknown capacitance by measuring its impedance?

I've recently seen some fourth year engineering projects at my school (University of Waterloo) and one that I found interesting was this novel pressure sensor that uses nano silver separated by a di-...
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1answer
48 views

Cable-to-cable crosstalk (Capacitative Coupling)

I'm having some difficulty understanding the solution to this question. Compute the cable-to-cable crosstalk due to capacitive coupling in a harness between two cable pairs having an average ...
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2answers
169 views

Capacitive touch insulation problem?

I have an "U" shaped metal profile that is 2 meters long each side is 1.5 cm. It is sprayed with acrilic color. and i want to use it as indirect light profile/enclosure for a 12v Led strip. While ...
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1answer
58 views

Does this speed controller alter resistance or capacitance?

The attached image is of a ceiling fan speed controller module I brought online. It seems the attached circuit mainly consists of some capacitors. This makes me believe that the 4 different settings ...
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1answer
62 views

Sensing a touch of a metal

Assume there is a piece of metal. I would like to identify, with a microcontroller, if another metallic object is touching this piece. I want to apply this for a smart hook that "knows" if a ...
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4answers
806 views

Why do we use two parallel capacitors in a voltage regulator circuit? [duplicate]

C1 and C2 are parallel capacitors and their total capacitance is 1000.1 uF. I think C1 is ...
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1answer
27 views

C4D capacitively coupled electrode sensing - circuit simplification

I am trying to make a detector to pick up small changes in capacitance. Basically both electrodes have a common ground and are closely spaced. One is driven by oscillator at 0.1-1MHz and the other one ...
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1answer
52 views

How to find the sketch energy of the capacitor (let's say versus time) with the q-v plot shown below?

I wonder what is the plot of the energy of the so-called capacitor,it's will be 0 except in 2 and 3 that is a delta function but when we want to calculate it's energy we don't know the exact value of ...
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3answers
299 views

If the voltage doesn't kill you, does the current capability matter?

Trade electricians often work on live household circuits carrying 120V AC. I've gotten shocked by accidentally touching such hot wires often enough to recognize the 60Hz AC buzz. Fortunately, human ...
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2answers
98 views

Find the equivalent capacity of this circuit [closed]

I wonder how to obtain the equivalent capacity of the circuit below.I think adding a voltage source and using KVL would be a nice idea but I don't know how to apply it.any hints would be appreciated.
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1answer
53 views

Glove Breach Detection

I'm trying to design a circuit that would be fitted inside large plastic gloves. That when the gloves are cut the circuit produces a signal. Currently I'm considering having a metal (probably ...
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3answers
166 views

Definition of equivalent capacitance [duplicate]

I know that equivalent capacitance of multiple capacitors in series is $$ C = \left(\frac{1}{C_1} + \cdots + \frac{1}{C_n}\right)^{-1} $$ and in parallel is $$ C = C_1 + \cdots + C_n. $$ But there are ...
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89 views

Capacitance node calculation

I am trying to calculate the equivivalent capacitance to ground of a 3 phase LCL filter with capacitors to ground. Inductors removed from circuit as I assume they will be ignored by the meter... ...
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1answer
183 views

Have I damaged my multimeter by applying voltage in resistance mode?

I have an VC97 digital multimeter. In resistance mode, I applied the multimeter leads to a battery with a 4.2V charge. I did this twice, and also did so in capacitance mode. I didn't notice any ...
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2answers
56 views

Measuring small (and small changes in) capacitance

I would like to measure the capacitance between two random pieces of metal. Also, I would like to monitor the changes in such capacitance as people walk by those metal objects. Can a cheap off-the-...
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2answers
125 views

Physics explanation of charging time by increasing dielectric constant

I am having a problem understanding in physics of the relationship between charging time and dielectric constant of a parallel plate capacitor. I'd like about physics aspect not based on time ...
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1answer
67 views

Understanding the Difference Between Two Capacitance Sensors

I'm slowly beginning to understand more about how these work thanks to answers I have received on this site. I believe one area of confusion for me has been I've looked at two differently designed ...
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1answer
93 views

Can I use any capacitor for a 2 phase AC motor?

So recently I got my hands on an old pump motor, unfortunately the connection diagram is missing. I have already determined this is a 2 phase motor, and that in order to make it work I need a motor-...
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1answer
84 views

Design challenge: Detect finger-to-finger touch with nothing in between

I'm trying to build something quite challenging and seem to be getting nowhere. Maybe you'll help. I'd like to detect a touch of two naked fingers with no materials or sensors in between (simple ...
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1answer
76 views

Capacitor Help -> Will stacking of dielectric and metal foil increase capacitance?

I'm new to this forum, so forgive me if I am missing something. I am building a capacitor, and I want to know if stacking dielectric and metal foil will increase the capacitance, and if so At what ...
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1answer
108 views

aluminum foam capacitor

Sorry if this question is in the wrong community but anyway, why don't people use foam aluminium for capacitors? Its got a large surface area to my understanding (however probably not as much surface ...
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1answer
63 views

Power factor correction AC motor

Four 240v, 50Hz, 16kW motors are installed in a factory. Each has a power factor of 0.86 lagging and efficiency of 78.2% while running. Determine the shunt capacitance required to deliver unity power ...
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Electrometer mode of universal amplifier [closed]

Explain why a high resistance is used in electrometer mode. A voltmeter can also be connected to amplifier but what is the use of high resistance in universal amplifier electrometer mode. The circuit ...