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

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How do I prevent a capacitive touch from registering?

I'm looking for a thin cloth-like material or something that I can treat materials with that will prevent a capacitive touch from occurring. Everything I've tried either is too thick, or still ...
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15 views

Rise time degradation by connecting to an input buffer

Suppose I have an imaginary 1.8V lvcmos output buffer and I know from the datasheet that it has an unloaded 10-90 rise time of 1ns. Now I'm going to hook up 6" of trace, to an input buffer who has an ...
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35 views

LC tank circuit feeding on op-amp, no oscillation?

Based on what I learned during this experiment I've built the following circuit using an op-amp configured as a buffer... simulate this circuit – Schematic created using CircuitLab The ...
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1answer
25 views

How to simulate parasitic reactances in a circuit

Does parasitic capacitance of a microstrip trace add to the value of a physical capacitor on the same trace? If one sees it as a series element, then it would seriously reduce the value of all ...
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26 views

Finding the input capacitance of this critical path

Hi so I'm trying to find the input capacitance of this critical path and then find the EF, Electrical Fanout, Cout/ Cin. Cout is given to be 10pF Okay here's my attempt at solving this. We know ...
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3answers
61 views

How to properly connect and drive varicap diodes?

can someone explain me how to connect and use varicap diodes? Please consider that I am a novice, so would be ok to use a clear and an exhaustive language/terms. Thank you. I often see these ...
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1answer
47 views

Measure I2C bus capacitance

We are trying to calculate how many I2C slaves we can hook up the I2C bus. We tried to run a square wave through a serial resistor and measure the rise time but we get a strange result. More nodes ...
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1answer
40 views

Related to varactor Diode?

I'm working on my project during this i face some problems... Here i mention my problem:- I required some variable capacitance whose range is C=0.05pF to C=0.5pF. So there is any variable ...
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2answers
32 views

reading capacitance on digital meter

So I bought this digital meter from radioshack because it tests capacitance. I have several caps on a TV power board, most of which are 47uf and 470uf with various voltages. when I check with the ...
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2answers
74 views

Understanding capacitive load conditions for a microcontroller

This is from a PIC24E microcontroller datasheet. My question is understand what does "load conditions for device timing" mean ? Does it mean in order to maintain timing (say for a high speed PWM ...
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1answer
55 views

Can two capacitors be used in series to get a equivalent capacitance in a circuit?

I am building a FM radio circuit and a 27pF capacitor(Ceramic) is required in that, but i don't have one. But i do have 56pF capacitors. So i was thinking that can i use two 56pF in series to get a ...
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1answer
41 views

Stray Capacitance in my load waveform?

I have just taken this trace of my Loadwave form for PWM controlled halogen dimmer. I was wondering if anyone could identify the cause of the transients below or above zero volts for each polarity. ...
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1answer
72 views

Trouble calculating time to drain a capacitor

Introduction I'm having trouble producing an equation that involving my MAX756 boost chip, a load and my 1.5F capacitor. Basically I'm trying to find out how long it would take for a 1.5F capacitor ...
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3answers
148 views

Simple ADC alternative by using a capacitor and digital Arduino pin

I'd like to measure a dozen potentiometers with an Arduino UNO. Unfortunately, the UNO only has 6 analog pins, but it does have about a dozen digital pins. Could I effectively measure an analog value ...
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1answer
75 views

How do I deal with different XTAL pin capacitance when selecting XTAL and load capacitors

I'm trying to select a 32kHz crystal and appropriate load capacitors for Atmega48A MCU. Atmega48A specifies different capacitances for Xtal1 and Xtal2 pins: 18pF for Xtal1 8pF for Xtal2 The ...
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1answer
60 views

What is power dissipation capacitance?

This question is derived from the answer to another question What is the input current of the 74HC595 The answer makes a note to the OP, that he should also consider power dissipation capacitance. ...
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0answers
44 views

How to switch on or off capacitance on a piece of conducting material?

I don't know if this is the right way of describing it, but I need to activate an area of capacitance on a touchscreen by applying some current to a piece of conducting material like tinfoil. I am ...
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2answers
96 views

Understanding to isolating sensor input capacitance

The circuit given above is pH sensor buffer circuit, picture taken from here. This circuit have pH sensor input and gives an output that can be read by multimeter which is U2's OUT_ pin . U1 is here ...
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2answers
142 views

How to calculate a electrolytic capacitor based on current and voltage to have the smallest ripple

I have built a circuit involving LEDs powered on 230V AC. The LED current driver that is powered on 30V and contains 10 LEDs of 1W each. 10 of these modules are linked in series and are ...
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1answer
41 views

Temperature Coefficient of Capacitance

How can I find the Temperature Coefficient of Capacitance of the following capacitor series: http://www.cde.com/resources/catalogs/TAS.pdf
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1answer
90 views

factors influencing capacitance of a cable

I am out of my depth here so I am looking for a simple explanation. If you have twisted pair cables of differing makeup, varying in conductive material, diameter of the conductor, number of twists per ...
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1answer
96 views

An “operation” game sensor where the stylus is NOT attached to the power source

Edit: The person operating the catheter will be wearing latex gloves. The only human tissue the catheter would touch would be that of the patient. Also, to clear up some confusion about what exactly ...
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3answers
79 views

help with capacitors and project

Capacitors have me crazy. I cant comprehend them even after lots of research. I know that capacitors deal with resistance, voltage, current and capacitance.(ohms, volts, amps and farad) but I cant ...
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50 views

Calculating capacitance at resonance

Could someone help me please asap, New to this ! Thank you! working out for the first one , could someone confirm? first question has been confirmed thanks Second question confirmation? thanks
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3answers
123 views

How to programatically simulate a click on a capacitance-sensitive button?

I am tearing apart a SONY HT-XT1, which has capacitive buttons to put it in a different case for a project: I've taken it apart already and am now met with a motherboard with 3 pads on it. Touch ...
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1answer
110 views

Did Capacitative Loading Kill My Op Amp?

I've been playing with various constant current source configurations to help control the current output of my bench power supply and my latest efforts centred around the op amp and MOSFET approach. ...
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21k views

Measuring feline capacitance

When I pet my cat, and then touch her on the nose, I get a little shock. Sometimes, when she walks up to something, her nose sparks and she jumps back and puffs out. I was wondering how I might go ...
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1answer
84 views

What is the capacitance and/or inductance of a single straight piece of copper wire?

What is the capacitance and/or inductance of a single straight piece of copper wire? I know the answer is on Wiki, but I need for the answer to be supported. I know that Wiki provides references, ...
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54 views

Using capacitors to control the speed of a relay loop

Background: In my autoshop class at school we are required to make a circuit that uses relays. When one relay comes on the other one shuts off and it creates a loop in which they switch really ...
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2answers
129 views

Big capacitors measurement(LCR meter related)

I digged up some capacitors from amplifier and decided to test them, one of them is said to be 8200 uF, the other 4700 uF. I measured them with LCR meter and it gives very strange numbers. If LCR ...
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4answers
158 views

Capacity of a capacitor fully charged vs half charged

I read in most places, when people ask "can I replace a 10v 10uf with 100v 10uf?" and everybody answers "it's the same". Well... how can it be!?, I have a comparator circuit, that uses a little ...
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1answer
55 views

Need help with Relaxation Oscillator with Parasitic Capacitance

I am trying to build a capacitance meter using a simple relaxation oscillator with a fixed resistor R in series with a capacitor to be measured C. I am applying the formula where Freq=frequency and K ...
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3answers
146 views

Output capabilities of super capacitor

I have come across a question that is very near and dear to my heart and I am in the hopes that somebody can answer this new years eve question of mine per se. So I am wondering, if I were to run ...
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1answer
102 views

DC/DC converter/eFuse maximum output capacitance

I have some doubts about the design of this DC/DC converter circuit/PCB circuit: On the left side there is a 400V to 12V DC/DC converter (Vicorpower DC/DC Mini, 300W). The maximum output ...
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1answer
182 views

Why is the capacitance changing while measuring?

I have 2 different 100nF capacitors. Let's call them A and B. My dad told me that B is "better" than A. I've tried measuring their capacitance using a Metex multimeter which has the option of ...
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1answer
63 views

ACS758KCB Wiring Diagram

I am using the ACS758KCB Hall Effect sensor for a project. On the front page of the Datasheet it list a .1uF capacitor between Vcc and GND, in addition it lists a capacitor, Cf, between GND and ...
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1answer
57 views

Capacitance value - AC RC Circuit - Impedance Method

Here is the circuit: simulate this circuit – Schematic created using CircuitLab \$ V_i = \frac{8}{\sqrt 2} \angle0° V\\ V_c = \frac{6}{\sqrt 2} \angle45° V\\ R = 1000\space\Omega \$ ...
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112 views

How to select capacitor for my rectifier circuit

I had designed a rectifier circuit, in that I don't know how to choose capacitor. for example if I'm get in input supply as 9 V, now I want change it for 10 V, then how should I choose capacitor.
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1answer
39 views

Capacitor Units For Power Factor Correction

I have got the assignment to improve power factor of an industry. I have worked it out and found capacitance in K Vars and Micro Farads but need to know about the capacitor representation in volts?
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1answer
412 views

Crystal Oscillator not giving correct frequency

I have a 48MHz Crystal Oscillator (see here) that I am using as a clock for my microcontroller (EFM32GG332F1024). Looking at the datasheet for this crystal it seemed to me that the load capacitance is ...
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1answer
77 views

How is a reed switch used to charge/discharge a capacitor?

Ok, so there's no way to disguise this; I admit this is a question I've been set for homework but I can't find a full answer to. I know that, in brief, a reed switch consists of two metal contacts ...
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1answer
42 views

Capacitor with n electrodes

In my book it says that the capacitance in a capacitor with n electrodes is (n-1)*Co, Co is a capacitance of a two parallel plates capacitor. I know how to distribute charge when there are 3 parallel ...
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2answers
1k views

Does current flow stop when a capacitor is fully charged?

If I take a 1V battery and a 1 farad capacitor and a bulb and connect them in a circuit. Then will after the capacitor gets charged (not fully charged as that is impossible) will the bulb gradually ...
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0answers
113 views

Self tuning 125khz RFID reader

I have a RFID reader based on the EM4095 IC. I would like to make the reader self-tuning so it can handle varying inductance in the antenna due to reading tags near metal. I had thought of using a ...
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2answers
180 views

Capacitance - Voltage characteristic diagram in a Schottky diode

I 've searched the web for that diagram with no satisfactory result. Does a schottky diode has capacitance or not because of very tiny depletion (almost none) zone ?
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1answer
76 views

Do we ever use the pin capacitance of a digital circuit component (e.g ASIC, FPGA) in doing timing or data integrity analysis

As far as I understand, the pin capacitance on say an ASIC or FPGA effects the rise and fall time of the signal on it. It is also possible that the impedance offered by this capacitance to a very high ...
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2answers
1k views

How to make LC tank circuits oscillate continuously?

An LC tank circuit produces oscillations, when the capacitor is charged and connected to the inductor, but the oscillations decay gradually. How to make it continue, i.e. oscillate continuously? I ...
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85 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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99 views

Finding the value of capacitance for a given circuit

How would you know how much capacitance you should use in your circuit or is there any formula to compute on the desired capacitance you should use on your circuit? I have this circuit (figure shown ...
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1answer
63 views

Where does the power absorbed of this capacitor come from?

In my circuits book, the voltage across a capacitor is given as \$v(t)=100\cos({2\pi60t})\$. Because \$i_{ab}=C\frac{d}{dt}v_{ab}\$, we naturally compute the current as ...