Questions tagged [capacitance]

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

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27 views

What determines the upper limit of the capacitive load on a DAC?

I need to drive a number of piezoelectric actuators. The AD5535B seems promising because of the high number of channels and low cost (and I happen to be able to borrow one for testing) but sadly, the ...
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54 views

Low capacitance diodes

I was reading the datasheet of DALC208 which is a low capacitance diode array. It is designed to protect components which are connected to data and transmission lines from over voltages caused by ...
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68 views

What is the capacitance of this Maytag fridge capacitor?

I have this capacitor in a Maytag fridge freezer. The fan stops when the fridge is on but works when the freezer alone is on. I am assuming the problem is the capacitor not bring able to boost power ...
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3answers
131 views

Can you get shocked if you touch a hot wire whilst perfectly electrically insulated?

Okay this issue has been bothering me immensely so hopefully someone will be able to help me out or steer me in the right direction. Lets say hypothetically I possessed an absolutely perfectly ...
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2answers
46 views

How to determine SMD capacitor rating

I am trying to fix my robotic sweeper, and I saw this highly suspect capacitor on the PCB, I presume it is gone and needs to be replaced. However I dont see any rating over this unit, so I am not ...
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5answers
150 views

How to emulate a capacitor discharge curve using a microcontroller output pin?

I require a configurable amount of capacitance, without using a bank of dozens of actual capacitors and some kind of complicated switchboard, like this: Not only would this be an unwieldy solution, ...
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1answer
2k views

shunt capacitance the same as stray capacitance?

I need a crystal for my project and I found this crystal: https://mouser.com/ProductDetail/TXC-Corporation/9C-16000MAAJ-T?qs=sGAEpiMZZMsBj6bBr9Q9aWUu9Vmt5DeozjX1gZsyHq8%3D To calculate the two ...
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Measuring MOSFET input capacitance?

Am I calculating total input capacitance or gate capacitance or none of the above? And are my calculations even correct to begin with. The point of this is that I want to know what gate capacitance im ...
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1answer
953 views

Capacitive touch screen sensitivity question

I have a question about capacitive touch sensing. I have read a few related questions already (here, here and here) and I think I understand the basics. From my understanding, when a human uses a ...
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2answers
2k views

Equivalent circuit to use when calculating the impedance of an electrical cable from its datasheet parameters

I'm trying to work out the impedance of a cable (specifically a single twisted pair of Lapp Kabel 0035836). The datasheet quotes the following information: ...
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293 views

ring-capacitor design

I created a simple design, based on the fundamentals of a parallel plate capacitor. Making a co-axial/tubular design: Front view: The "Air gap" is there to allow current flow in one-direction, from ...
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3answers
5k views

Balancing Resistor Values for Series Capacitors

I just wanted to confirm my rough calculations are correct in selecting balancing resistors for 2 capacitors in series. Here are the specs: 2x 10,000uF Capacitors with 500V rating in series. I ...
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In a parallel plate capacitor, how does placing a metal in between the plates reduce the capacitance?

This source claims that putting a metal plate in between the capacitor plates greatly reduces the capacitance. How is this possible? Two equal capacitances in series decreases the capacitance by ...
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1answer
161 views

Selecting true crystal settings for 328P [7.3728 MHz]

I want to make a new board working with 115200 (gsm modem) UART. so I want minimum baud error rate. I look at https://cache.amobbs.com/bbs_upload782111/files_22/ourdev_508497.html table and decide ...
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4answers
8k views

How to Derive Capacitive- and Inductive Reactance Formula

I've been searching around the internet to find out how to derive the reactance formula for capacitors and inductors. But I couldn't really find anything, so I thought why not make a post about it. ...
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70 views

Does a 4 pin smd crystal need external capacitors to work properly?

My understanding of how this works is quite poor, I've tried reading many sources but just got even more confused by the terms crystals, crystal resonators, ceramic resonators, oscillators, crystal ...
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1answer
57 views

Off Grid Storage Capacitor Calculations

I'm thinking about using a very large home made capacitor as an energy storage device for a light duty off grid application, running some led lights and some 500w loads for a few hours each evening. I'...
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338 views

Crystals, capacitors and W5100

Background: I have built a number of devices based on the W5100 chip, all them were (are) working more or less decently. However last batch currently in testing show faulty behavior - almost all of ...
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1answer
64 views

In need for high variable capacitance

I am constructing a Chebishev or Butterworth audio filter (low and high pass), but I need to have all parameters highly adjustable - especially Fo and Q. For this purpose i would need to be able to ...
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6answers
777 views

Why does wire not have large capacitive reactance?

For capacitive reactance, I am presented this formula: $$X_C = -\frac{1}{2\pi fC} $$ Where clearly, the capacitive reactance is inversely proportional to the capacitance. This confuses me. We usually ...
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29 views

Ac Fan motor capacitor value

I have a bad 350v 2 uf fan capacitor. I managed to find a 400v 6.3uf cap in my locality, would this work instead of the 2uf one? Thanks.
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1answer
37 views

Can the capacitance of a proximity sensor be increase by adding layer to the capacitor?

Would adding layers to the capacitor of a proximity sensor from lets say 1 (A) to 4 layers (B) help with increasing the capacitance and at the same time the distance that can be sensed with a ...
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1answer
196 views

How long of a wire and how big of a load can I have for SPI bus?

I have a system where I will connect up to 128 identical magnometer ICs up to an FPGA. I am trying to decide between SPI and I2C for comms. If I use SPI the setup will require 128 + 3 wires IF all ...
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3answers
68 views

Capacitance of 2 angled conducting plates

I have to determine the capacitance of 2 conducting plate (fringe fields are ignored) with a certain area (5m^2 here) with a gap separating them (4mm here). The second plate is inclined at an angle of ...
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2answers
74 views

I need to measure the impedance of the system, is it better to measure the resistance or capacitance?

The goal of this project is to measure Retinol levels in the blood. To do this I will be use two electrodes, one of which will be coated in nanowires. These nanowires will then have antibodies that ...
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78 views

Analog circuitry for measuring capacitive touch

I'm interested in adding capacitive touch input to a project I'm working on. Ideally I would like a tapered shape so that a finger can slide up as if it's a mixing desk fader or something like that. ...
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1answer
48 views

Can you use 'Rubber,' Specifically Liquid Electrical Tape Between The Plates of a DIY Capacitor

The above is pretty much all there is to the question. By "can you," I mean will it be properly effective / are there any tips? If not, why? It seems that this ought to work, but I can't ...
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70 views

Capacitance of semi-cylindrical plates?

For a visual reference of what I mean by semi-cylindrical plates check the diagram below. EDIT: The above diagram is not what I intend to implement. It is just to show anyone trying to answer the ...
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1answer
2k views

Why must USB low-speed devices use a captive cable?

The USB 2.0 spec says: "A low-speed device is required to have a captive cable." However, I can't find a good explanation for why this is the case. I have seen hints towards two possible ...
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1answer
58 views

What effect does the thickness of metal plates have on capacitance?

Clearly a decrease in thickness of the dielectric increases capacitance, but how about the metal plates on a parallel plate capacitor? If you increase or decrease the thickness too much will you see a ...
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2answers
94 views

Endless oscillator [closed]

Can we create an endless oscillator? simulate this circuit – Schematic created using CircuitLab The diodes will only allow a tiny current to move through the tank circuit-> the power loss ...
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1answer
43 views

Would bypass capacitors of a voltage regulator which powers an I2C device and the bus cause issues?

I'm planning on powering a 3.3V I2C sensor and its pull up resistors with a linear LDO regulator. http://www.farnell.com/datasheets/2108564.pdf The output of the LDO aswell as the sensor's power pins ...
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1answer
44 views

Can multimeter measure 3200µF if capacitance measuring range:10p…40n/400n/4µ/40µ/200µF?

A multimeter that has this specifications: Capacitance measuring range:10p...40n/400n/4µ/40µ/200µF will not be able to measure a 300µF or 3200µF capacitor? That's how it sounds, but I want to make ...
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22 views

Charge through a time-varying capacitor

If a capacitor has a time-varying capacitance, such that C(t) = C_0 + Kt, where K>0 is a constant. Then is charge-voltage relation, Q(t) = C(t)V(t) = (C_0 + Kt)V(t), valid? It should be noted that ...
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1answer
37 views

How is capacitance found when there are 2 different regions with dielectric in the in 2 parallel plate capacitors connected in series

The two capacitors are part of a capacitive pressure sensor, I am curious with reference to electrostatic theories how would capacitance be found in respect to the dielectrics. The two capacitors have ...
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Solve for junction capacitance from diode's SPICE parameters

I am trying to calculate maximum junction capacitance (or depletion capacitance) \$C_j\$ for the BAT62-02L diode from this datasheet based on its SPICE parameters: \$I_s=\$ IS \$=\$ Saturation ...
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4answers
122 views

How do capacitors in series work?

If capacitors are connected in series with a vltg source, then how would each plates get the polarity? For a single capacitor, the electrons from one plate are pumped by the source towards the other ...
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1answer
90 views

Measuring resistance with ohmmeter over resistor and capacitor in parallel

In "Teach Yourself Electricity and Electronics, 6th Ed." [Gibilisco] (2016) a test question reads as follows: A DC ohmmeter will give us a correct reading for a component in isolation (not ...
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How would you determine the Miller input and output capacitance for the amplifier in the figure?

When I calculate the Miller input and output capacitance I get; Cin(Miller) as 6.38pF and Cout(Miller) as 5.66pF. However, these values are incorrect.
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Button debounce ringing

I have a circuit where I am using a tactile switch to pull 3.3v down to ground and investigating debouncing the button. My relevant part of the circuit is The 100nF cap does work here my signal has ...
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1answer
44 views

Substituting a capacitor of different capacitance [duplicate]

If a circuit calls for a capacitor with a specific capacitance, what happens if a capacitor with a different capacitance is substituted? I have a circuit that calls for a 250uF capacitor to power a ...
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2answers
53 views

Isolation Capacitance (Cio)

How I can find a practical value of CIO barrier capacitance (primary to secondary side) in digital isolators?
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4answers
10k views

Crystals and load capacitance

If a crystal has a rated load capacitance of 6 pF, is the right thing to do to put a 6 pF capacitor to GND on either leg of the crystal? I'm using it as the clock source (TOSC) for an XMEGA and it's ...
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1answer
44 views

Calculate the capacitance equivalence in the circuit across terminals A and C

Greeting friends I am having some trouble to calculate the capacitance equivalence in this circuit due to the short circuit? Calculate the capacitance equivalence in the circuit across terminals A and ...
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28 views

How to calculate gate capacitances (Cgs,Cgd) of a GaN HEMT?

I have calculated Cgd and Cgs using an analytical model, And I found that the second one is negative for Vgs < Vth, where Vth is threshold voltage and Vgs is the applied voltage. could this be ...
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1answer
41 views

How to estimate I2C bus capacitance?

In my current project, I need a microcontroller to retrieve the temperature of 60 temperature sensors which are located on the same PCB with distances not exceeding 50 cm. The temperature sensor's ...
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3answers
417 views

Capacitance Measurement With Oscilloscope

simulate this circuit – Schematic created using CircuitLab I'm trying to determine the capacitance of a sensor, but the oscilloscope's internal capacitance is loading the measurement too much. ...
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1answer
27 views

How to control a capacitance control panel from a Raspberry Pi

I have a touch control panel with only one lead going to each "button" on the glass, it is not a full circuit only half of one. I have concluded if i ground one of the pins (ex: power), it senses and ...
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2answers
438 views

Approximate Capacitance of a Multilayer Solenoid Coil

I'm interested in an expression for the capacitance or resonant frequency of a Helmholtz like coil (the windings are parallel to the plane of the coil) of circular or square cross section and of the ...
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2answers
66 views

Why can't the equivalent capacitance be calculated like the method 2?

Question Three capacitor with \$C=100\mu F\$ and \$50V\$ are series connected,and connected with the \$10V\$ voltage source,what is the equivalent capacitance of this circuit? Method 1 \$C_{eq}=...

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