# Questions tagged [capacitor]

A fundamental electronic component that stores energy in an electric field, commonly used in filtering applications.

592 questions with no upvoted or accepted answers
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309 views

### Is the "dc impedance" and ESR the same thing?

In a super-capacitor, what is the DC Impedance? Is it the same as ESR (Equivalent Series Resistance)?
70 views

### An SoC pulling the power source voltage

I'm trying to power a SoC with a battery as in the figure below. The SoC in question is the WeMos, based on the ESP-8226. simulate this circuit – Schematic created using CircuitLab When the ...
226 views

### Understanding how bypass caps work, mathematically

Assume there is a band of noises that you you want to filter with center frequency Fn. Then The complex voltage representing noise at frequency F is V_(F, T) = V(F) e^(i W(F) T), where V(F) is the ...
226 views

### Calculate power on time of a buzzer

I would like to use a 5v active piezo buzzer to beep for a second or two. When the relay is on NO the capacitor will charge from the dc source and when the relay is on NC the capacitor will discharge ...
582 views

### Capacitor Charge Redistribution

Consider the following situation We have two capacitors, C1 and C2, both with a value of 10μF. The capacitor C1 through some switching action now has a voltage of -Ain + Vref across it whereas C2 has ...
240 views

### Delay circuit with capacitor and transistor doesn't work as expected

I made the following delay circuit. According to the simulation, it should take in the order of seconds for the relay to switch. Instead what I find (even by varying the resistance of the second stage)...
59 views

### How capacitor values are determined in this circuit

I am following the course on control systems from edx. I have this circuit as part of practical exercise. I would like to understand how the capacitor values were determined in this circuit The 47uF ...
2k views

### why capacitor accumulate less charge in higher frequency

it always said that the higher the frequency, the less charge will accumulate because when in higher frequency, there is less time for capacitor to accumulate electrons. and in lower frequency, there ...
77 views

### Creating a blinking circuit (sensor probe)

I'm a veteran of electronics with little knowledge if that makes any sense at all. I've dabbled in electronics for about 12 years now, and have had so much going on in life that I've strayed away from ...
776 views

### Capacitor sign convention

I am a lot confused about how to assign the current of a capacitor and the sign of its constitutive relation, because usually in physics and in engineering there are different conventions. There are ...
45 views

### Building a 12V-trigger circuit

I guess this a very basic question, but I'm basic when it comes to electronic circuits. The question is somewhat audio related. I have a pre-amplifier with a 12V-trigger out and a 3 devices that has ...
85 views

### two Y capacitors used as protective impedance

Can two "Y" capacitors be in series and used as protective impedance bridging primary and secondary where the secondary circuit is accessible?
61 views

### What is the charge flow between a charged capacitor and an uncharged capacitor connected in series

What will be the charge on both the plated after bc is closed? (Imagine that both the C1=C2=C)
93 views

### LTspice simulation with capacitors

I have this circuit simulated in LTspice : simulate this circuit – Schematic created using CircuitLab Here is the graph: Why does the current flowing through R2 do that thing in the beginning (...
112 views

### Inductor - capacitor filter, load disconnected

I'm designing a power supply filter based on inductor - capacitor topology, as shown below. However, when the load is suddenly disconnected, a high current starts flowing through the capacitor, as ...
378 views

### Can I charge a super capacitor with a MPPT?

I already did some testing. I have a 220mW solar panel that charges a 3V supercap (takes a long time) which eventually powers my wifi module that needs ~1.5W (1.5 J/s) for 1 second then ~90mW (0.09 J/...
101 views

### laser --> charge capacitor?

I'm not an EE, but I do have a question that I hope isn't totally trivial. Please tell me if I have the calcs below correct: Current research on the surface photoelectric effect shows that if one ...
52 views

### Custom Test Fixture for LCR meter

I've designed and built a custom test fixture (based on Keysight's 16047A) to be able to measure multiple pin capacitors. When testing it to compare both fixtures (the custom and the original), I ...
919 views

### Battery indicator Circuit

Many of battery indicator circuits are designed using 2 or more leds like in the image above but how to design a simple battery indicator circuit using only RGB LED and transistor for 12v battery ...
1k views

### Time Constant of a Complex RC Circuit

I'm trying to model a diode as two capacitances, a conductance, and a series resistance, as shown here: In order to generate an expression for the capacitance I'm equating 1/w3db to the time constant ...
546 views

### replace ceramic capcacitor with electrolytic one

I need help, that i have a lack of ceramic capacitor value variety in my country. I need 47μF (microfarad) and 2.2μF (microfarad) ceramic capacitor and i can't get these values. So the question is,...
98 views

### How to determine capacitance

I’m looking to install a capacitor in a circuit which runs at 12V and <10A, and I want it to discharge in about 3 seconds. The discharge voltage isn’t too important, but it’s probably best if it ...
342 views

### Correct size resistor to light a 17v LED with a capacitor?

I'm very much a beginner at creating my own circuits and using an Arduino so please excuse any stupid mistakes and oversights. First of all here are the components I want to use in the circuit: ...
98 views

### If I added a Capacitor to this circuit would it charge both and would the charge led still work?

If I were to add a second capacitor to this circuit of roughly the same capacitance (120uf). Would this circuit charge both up completely, and would the LED still accurately depict if the combined two ...
2k views

### RC Circuit with dependent source

How to find i(t) t>0.I stuck.If cannot help me okey.
172 views

### The capacitance value that makes the voltage in phase with current

What's the value of the capacitor that makes the voltage in phase with current , and then what's the circuit current and power?
221 views

### Power supply for multiple solenoids

I'm currently looking to power 10 solenoids: rated (nominal) at 24VDC, 400mA, 10mm stroke, 25N. (JF-1040 no datasheet unfortunately) I will be powering with a voltage higher, (giving me a range to ...
2k views

### Problem in identifying positive and negative terminals of a capacitor

I have got a capacitor from a fan. The electrician says that it's not working, but I think he is lying. I want to test it with a multimeter. But I cannot understand which plates are positive or ...
745 views

### Current Waveform Graph

My question is as such. I honestly have no clue as to what im doing. Im not really asking for anyone to do the problem out, i would instead prefer if someone could point to a resource where i could ...
392 views

### To derive differential equation from Kcl Kvl for RC circuit

I have a RC circuit named called active realization of compensator, which is used in control systems, and is given in the following link. https://www.dropbox.com/s/zpmq5ql6qr58gjb/Circuit.png?dl=0 I ...
1k views

### Servo control without micro controller

I am trying to create a circuit that will control a servo. I need the servo arm to move from 0 to 90 degrees when the power is turned on, and then from 90 back to 0 degrees when the power is turned ...
178 views

### RC circuit help

I saw in a book that U1 = U3 I mean if we apply kirchhof rule we get U1=U3 +Ur ? or maybe its different because its a capacitor ?
68 views

### How to size a capacitor?

I want to design a PCB with some ICs and I've read that it's recommended to use decoupling capacitors to filter out voltage spikes. There are three ICs on the PCB: Arduino NANO, nRF24l01 module and ...
174 views

### Induction heater resonance working

I was reading this article on the working of a induction heater. The below is a circuit show in the article which I was not able to understand. I have 3 questions : I think that Vsupply is a ...
11k views

### How to remove the static sound in an fm transmitter

Hi I have a school project and I used the schematics from this website for our FM transmitter. Its actually working but its hard to recognize the music being played because of the static, also does ...
99 views

### Ultra electrostatic capacitor generator

Part B of ultra capacitor 1 and 2 are connected to ultra capacitor 3 to provide potential difference. Part B includes charge collector and electrode. Part A of ultra capacitors 1 and 2 include the ...
116 views

### What type of capacitor do i need for this delay?

I installed a set of LED RGB foot-well lights on my truck. When they turned on, they have a small half second glitch before staying constant. I believe that this is because the LED RGB controller ...
133 views

### Current Divider Question

Knowing all the values of resistances, capacitances and the value of the current source is there a way to find out how current is split in the two branches?
32 views

### Match the corresponding equation to the RC circuit

By trial and error, I have found that the equation for circuit 1 is the second equation listed. Can someone please take the time to explain this to me. I have been working to "combine" the circuit ...
451 views

### LDO has no output

I've been trying to get a fixed output LDO to work for the past few hours, in order to step 3.6 V down to 3.3 V, but I have been unsuccessful. I am using the MCP1824T-3302E/OT LDO. I have it wired up ...
32 views

### Danfoss ac drive output voltage unbalance

i have a problem with danfoss ac drive, i replace the output igbt module with new one, when power the drive the output voltage not balance and the input voltage balance L1: 400v,L2:400v,L3:400v, ...