Questions tagged [capacitance]

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

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3answers
125 views

Parallel Capacitors with different voltages

Let's consider a capacitor precharged to 5V. Now immagine to put it in parallel with a capacitor which has no charge. What does it happen? They reach a voltage in the middle? Does it depend on their ...
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1answer
58 views

Pass Transistor: discharging of the capacitance

let's consider this pass transistor logic: Let's assume that the MOSFET is always active (CK = high for a N-MOSFET). Now, immagine that at the beginning Vin = 10V and Vx = 0: the capacitance Cx will ...
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1answer
50 views

Collector-Base capacitance in simple FM transmitter

Here is a schematic of a simple FM transmitter. I understand that this work in the following way: the sound picked up by the mic is translated into a voltage at the base of the Q1 transistor. As the ...
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3answers
60 views

Cap touch measurement using digital pin?

I have previously used dedicated touch pins and connected them across an electrode and been able to easily detect touch. Usually in such a case one wire directly from the pad to the dedicated touch ...
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2answers
52 views

RC circuit intuition

How to intuitively guess the output waveform of a rc differentiator to a ramp input? I know it will be a constant value if RC is very small but that's from calculation. How can I intuitively guess it? ...
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1answer
2k views

Capacitors with a “/” on schematic

I'm looking at a schematic for an old turntable that I am needing help on when viewing the capacitor values. All of the polarized caps will have 2 values written next to symbol i.e. ...
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0answers
53 views

Possible damage to PLC on 5 axis machine due to cable capacitance? [closed]

I have built a machine that has 5 axis. I am using an 150' 48 conductor cable to connect the pulse train outputs from a Siemens Simatic PLC to the 5 motors. Each motor has Step, Direction, Enable and ...
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1answer
67 views

How to run electricity through metal wire to (safely) act as a stylus?

I’m trying to make a robotic arm draw a lowercase ‘i’ on my iPhone’s drawing app without lifting the stylus. The robot arm bit is another story, my current focus is trying to make a stylus out of a ...
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53 views

Is diode reverse recovery time related to diode capacitance?

The title. Is there some relationship between the two parameters? For example, fast diode recovery time indicates low capacitance, or even farther, can one be calculated from the other? Thank you in ...
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0answers
47 views

Opamp isolation resistor calculations for a capacitive load

I want to add a capacitive filter for pulse shaping to the output of a transimpedance amplifier using an OPA847. Without the filter, the amplifier works great. With the filter, I get some ...
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0answers
27 views

Test circuits for testing input and output capacitance of an NMOS spice model?

As the title states, I'm having trouble finding resources online for confirming the capacitances of an N-MOS spice model. If there are any resources someone could point me to to learn more or test ...
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2answers
72 views

Is it a mistake in AD725 and other datasheets?

During my research of the RGB video and encoders I see two ways chip manufacturers/circuit designers treating the outputs (several examples below): AD725 (Analog devices): capacitor then resistor ...
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1answer
80 views

How large can capacitive sensors be if made of tin foil? [closed]

Based on a similar version of this: https://www.instructables.com/id/DIY-3D-Controller/ What are the limits to the size I can make this foil area? And the larger I make it, what does the area need? ...
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0answers
26 views

How to reduce noise for arduino capacitive sensing

I have an artistically-painted 5mm-thick wood panel that I want to use as a light switch without alteration to the image. My solution was to (try to) make a specific region on the panel touch-...
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0answers
40 views

Load capacitance of the crystal: what is the practical difference between devices?

There's a lot of info and guides on how to select and calculate load capacitors for the parallel resonant circuits. They all assume that people do already possess crystal, and know its CL. That CL ...
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2answers
260 views

Mutual capacitance sensor behaviour

In a typical mutual capacitance touch sensor when finger approaches sensor it draws electrical field in effect decreasing the capacitance of the sensor (which is described here and here, for example). ...
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2answers
105 views

How to find the right smoothing capacitor for rectification circuit

I am creating a power supply which will need to convert the 24vac to 5vdc. I am thinking of using a rectifier to convert ac to dc, then a capacitor to smooth out the voltage, then an LM2596-5 to drop ...
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2answers
64 views

Ultracapacitor, capacitance higher than rated?

Broadening my knowledge and experience about ultracapacitors I've made a test bench that was described in here. I've used an IEC methodology to calculate the capacitance: $$ C = (I_d*t_d) / (\Delta U) ...
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1answer
35 views

Advice on getting a stable analog reading of capacitance

I would like to detect the presence of a person's hand in a project. I am aware that one can use a capacitive touch system to do this. I have used a TTP223 module in the past and this works great ...
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1answer
40 views

Choosing a capacitor capacitance for a quartz resonator (ATMEGA328P)

I am designing a controller based on an ATMEGA328P-AU chip. For the chip, I provided an external crystal oscillator at a frequency of 16MHz. As a resonator I use YSX321SL His description refers to ...
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2answers
88 views

choosing crystal when tracks are very close together

This is a circuit I am having trouble with. I made 20 units with the exact same setup. Three units with this setup managed to work with 33pF ceramic caps with 20% tolerance and a crystal from Ebay. ...
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0answers
26 views

What type of capacitor should last longest in an led driver / dimmer?

I have several LED light panels and after about 3 years, they are beginning to flicker and go out. About half of them within a few months of each other. They are 15w panels and the drivers are also ...
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0answers
58 views

How to calculate stray capacitance on PCB

I use a 0.4mm spacing between PCB traces (including 0.4mm space between crystal pads and ground) and I believe that's causing stray capacitance. My circuit board is typical (1 ounce copper on FR4 ...
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2answers
43 views

How I can simply measure interwinding capacitance in a transformer with electrostatic shield

I want to measure which is the effect of the connection of the electrostatic shield (between primary and secondary) to ground (or to neutral) in reducing the interwinding capacitance in my transformer....
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3answers
68 views

Failed to plot junction capacitance versus reverse voltage in LTspice

The 1N4001 diode's junction capacitance versus reverse voltage plot is given as follows: I guess to measure this capacitance they applied 1MHz 50mV pk-pk sine wave signal as reverse biased and varied ...
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1answer
108 views

Capacitor value denoting

Hello I'm trying to understand the value in microfarads of capacitor labelled, C791 103(2) And how to calculate if the SI unit is not given thanks.. diagram below One more question if you don't mind ...
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1answer
29 views

Capacitance to useful signal conversion

Working on a project, where we need to measure the change in capacitance(capacitance change roughly from 0.5 pF at the start, to 20 pF at the end of the measurement). On the variable cap, only the ...
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1answer
99 views

Eigenfrequency of a toroidal resonator

All units are in the SI I'm doing my task from vacuum electronics - for the given klystron with a toroidal resonator[ Resonator: I have to find the $h$ parameter, that will satisfy given ...
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0answers
21 views

Hover Stylus for capacitive touchscreen [duplicate]

Capacitive touchscreens are designed to react to the capacitance of a human body. To my understanding the touchscreen is measuring local distortions of the electric field. Is there a way to influence ...
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2answers
67 views

what does Loss Tangent means in capacitor?

As we know the definition of Loss Tangent in capacitor which it is: When a sinusoidal alternating voltage is applied to an ideal capacitor, the current advances by pi/2 in phase. In the case of a ...
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0answers
37 views

How capacitance of human skin varies with frequency?

I want to know the variation of the capacitance of human skin as frequency is increased. Also how it affects the impedance of the skin?
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0answers
42 views

Moving a capacitor in a time varying or non-time varying magnetic field?

1) If a simple parallel plate capacitor connected to a circuit, and discharging, were to move in an exterior magnetic field, what would happen to the interior region? Interior region components: ...
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2answers
110 views

Soil Moisture Sensor Design

I am working on the development of a low-cost capacitive soil moisture sensor which uses dielectric permittivity changes to estimate moisture. I want to use FDC2214 for Cap to Digital Conversation. ...
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1answer
61 views

Questions about capacitive sensing

I'm trying to use the FDC1004 capacitance-to-digital and I have a few questions: Why do we (our fingers or another part of our body) act as the other conductive plate - don't we have a very large ...
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1answer
78 views

Powering phone using LDO regulator on battery terminals - what reservoir cap to use?

I have rigged up an old phone that does not run without a battery by attaching an AMS1117 regulator to the battery terminals. The regular is fed from +5V USB, and outputs 3.3V. The regulator comes on ...
6
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1answer
130 views

Using only stray capacitance for MCU oscillator circuits

I've included a diagram of typical Pierce oscillator circuit taken from ST Application Note AN2867: The note suggests that C_L1 and C_L2 should be chosen such that the following equation holds: ...
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2answers
88 views

Can I add output capacitance to a dc/dc boost converter to help with current spikes?

I have been playing around with achieving better power in my 30-year old RV. I want to create both AC and DC systems to provide power. This has essentially 3 routes from my battery to device: Samlex ...
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1answer
61 views

Why is the upper part of a Leyden jar terminated with a small sphere?

I often see pictures of Leyden jars that have a small ball attached to the end of the upper connector, was it just a question of aesthetic ?
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2answers
117 views

How does placing cap between signal GND and earth GND solve common mode noise?

Thanks in advance for your time. I am reading several articles about differential mode noise and common mode noise. Among which I found the below 2 pretty instructive: https://www.murata.com/~/media/...
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2answers
1k views

Estimate capacitor parameters

I am thinking of making a capacitor, just for fun/for studying purposes. And I thought of the following exercise. In my local store, there exists rolls of polyethylene food film and aluminium foil. ...
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2answers
80 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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2answers
91 views

How to remove 50 Hz, 100mV noise? [closed]

I am getting 100 mV noise signal at 50 Hz. I do not know the origin of the noise. What should I need to do to remove it?
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2answers
220 views

RC-Circuit With Two Capacitors that are neither in parallel nor in series

Background In our course, we have covered everything related to RC-RL-RLC circuit, however, all questions were based on the fact that you either have parallel or series connection. I've not taken ...
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1answer
67 views

Converting “MPR121 capacitive keyboard” sensor filter data into capacitance values?

The project that I'm working on, the MPR121 capacitive touch sensing keyboard connected with a 8051 microcontroller, my first intention when I started implementing the project was to measure the ...
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0answers
70 views

Focusing on Frequencies with Guitar Pedal Capacitors

I just built my first guitar pedal (a Bazz Fuss fuzz pedal), and now I'm messing around with the electronics a little bit. I was just wondering how I could target specific frequencies with the pedal. ...
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0answers
88 views

Imaginary Capacitance and Imaginary Inductance interpretation and relations with circuit theory

Today I came across with Complex Capacitances and Inductances for the first time: $$L(j\omega)=L_{real}+jL_{imaginary}$$ $$C(j\omega)=C_{real}+jC_{imaginary}$$ So I started looking at their meaning ...
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0answers
95 views

Mitigate parasitic capacitance coupling

First conceptually: Assume you placed two metal electrodes/tags on a fencer's body: one on the torso (large, the lamé), one in the hand (small, the guard). Equipped with a Capacitive Sensor located ...
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4answers
58 views

Point of contact with a capacitor plate & rolled design?

With a simple parallel plate design for a capacitor, does point of contact(to the external circuit) matter? I imagine any point(a - e) would yield the same feature in storing/discharging charge. ...
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0answers
79 views

Measuring a small distance via capacitance

I am interested in measuring a small \$d\$ between two objects shown below by measuring the capacitance between the Terminals denoted as T0 and T1: The distance \$d\$ is roughly 1mm +/- 0.5mm ...
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4answers
2k views

Capacitor electron flow

Well I was just wondering, a capacitor is made of 2 metallic plates separated by insulating material. During the charging of the capacitor electrons flow towards the opposite direction the battery's ...