# Questions tagged [capacitor-charging]

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### Dealing with inrush current - input resistor?

I've got a circuit that's having problems at startup with inrush current, leading to large spikes on VCC (parasitic inductive of the power supply / leads etc) that sometimes results in smoke coming ...
• 115
417 views

### Charging supercapacitors with reversed polarity

I bought six supercapacitors and connected them in series to get a total voltage of 16.2 VDC. The product's Mouser No is: 723-BCAP0450P270S18, Mfr. No is: BCAP0450 P270 S18, the datasheet can be found ...
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59 views

### Capacitor current in parallel network with ESR and parallel resistance

So this might be a very simple question and I've got a knot in my brain but I've been at this for days and don't see how I could solve this problem. I'm trying to find the solution for both ucA, ucB(t)...
946 views

### LTSpice: Why are my capacitors half charged at simulation start?

This is my first time using LTSpice, and I am trying to simulate what should be a very simple RC circuit ladder. I've gone ahead and set the initial state of each capacitor to zero using the .IC ...
1 vote
100 views

### Output voltage of capacitor discharged in other capacitor?

Considering this circuit. How can I compute the maximum voltage across the resistor ? In this example, the capacitor on the left is initialy charged with 10 V. The second capacitor (on the right) is ...
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1 vote
66 views

### Why is my capacitors' leakage current much higher than it should be?

I have a capacitor bank consisting of five 3.3 mF electrolytic capacitors. (Itelcond 400 V 3300µF datasheet here.) The five capacitors are connected in parallel and there's a charging circuit with a ...
• 307
84 views

### Does the 555 timer 50% duty cycle capacitor discharge not affect the output voltage?

I'm new to the 555 timer and I'm trying to understand the configuration shown in the image below. The tutorial mentions that the capacitor C1 now charges and discharges through the resistor R2. The ...
55 views

### Precharging my capacitor manually - looking for feedback [duplicate]

This is my plan, to pre-charge my capacitor of my electric vehicle manually, to prevent sparks occuring when connecting my heavy duty battery. The cables can easily handle 600A as well. Im asking here ...
84 views

### Charging capacitor trips breaker

I am designing a circuit to drive a DC motor from rectified mains voltage. For that, I have added a 1200uF capacitor. My problem is that this circuit is supposed to work on a user's home power plug, ...
83 views

### Are my capacitors working properly or not?

I've bought some capacitors because I needed to generate a current pulse into a coil. The idea was to charge a capacitor separately and then connect it to the coil to have a strong and brief magnetic ...
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40 views

### Component protection and charge optimisation for Solar + Supercapacitors

What are the best protective practices for solar cells and supercapacitors when they are used for small outdoor projects? Moreover, are there any way of widening the useable voltage output range of a ...
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148 views

### Short-circuit current through disconnected capacitor

I have a large capacitor made of two smaller 200V rated 560uF capacitors. If I charge this capacitor to 30V with 4.5A from a bench power supply and disconnect it after around 7 seconds, how do I ...
77 views

### Briefly switching a coil

We are going to build a telegraph which can communicate to an other telegraph. One of our communication systems exists out of a bell. The idea is that the sender can press a button and the receiver ...
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### Choosing the right capacitors for multiple sub-loads in the system when the main power source is unreliable

Hello there, I'm working on a system that has unreliable power source like solar cell (that why I put a switch in the schematic to indicates that).The general idea of the system is breaking out the ...
902 views

### RC circuit with a constant current source

I am trying to simulate a series RC circuit excited with a constant DC current source in LTSPICE. The expectation is that it should linearly charge the capacitor with a constant current flowing ...
219 views

### Parallel connection of DC DC Converters with different output to charge the battery

Generally, in connecting power supplies parallel one can follow current control or droop control rather than voltage control to regulate the output of a dc dc converter. If the output of both the ...
82 views

### 555 timer capacitor charging order

I have a question about the standard 555 circuit below. I understand to some degree the "insides" of the timer. In particular, I understand the role the comparators play and I am fairly ...
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### How can this circuit be best described?

Here, the green waveform is the input waveform(V1) and the blue waveform is the potential drop across Vc1 and Vc2. To me it seems like a peak detector getting clamped, but then the first half cycle ...
60 views

### What is this circuit with increasing voltage of full rectified wave?

{ The first image is original circuit.} { The second image is the output across RL resistor with ac source amplitude voltage 5V. } {Simulated circuit with output measured between A and B nodes.} To me ...
105 views

### Why does AC charge the capacitor?

I know that capacitors charge and discharge at the same rate. As the total the there will be no charge or no energy stored. When I connect a fan capacitor to the AC home source for few seconds and I ...
59 views

### Since current through capacitor (between the plates) is displacement current, what is the current flowing to the leads of a capacitor called?

Since there is no conduction current through the capacitor, what is the current that flows between the battery and the leads of the capacitor while the plates are charging (or discharging) to their ...
• 576
101 views

### Bezier curves in hardware? (X-Y-mode on oscilloscope)

As I am exploring how to use an oscilloscope as a raster display in a question yesterday, and building the circuit, I am finding that with about the same (even less) components I could build a vector ...
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85 views

### Parallel Diode in RC charging circuit

When button is pushed , active low RES pin is activated till Vc reaches 2.5 Volts. I have two questions here 1. What is the role of Diode which is connected reversed biased? 2. Which loop capacitor ...
380 views

### Charge a capacitor with negative pulse [closed]

What will happen if I apply a negative pulse to the capacitor? Is the capacitor voltage increase positive or negative? The pulse which is shown in the below picture is the output voltage pulse from ...
350 views

### Power ESP8266-12e for .5 seconds after power cut

I have an ESP8266-12e (ESP1) that is connected to Blynk with a momentary button. When the button is activated it makes pin D5 HIGH which goes through a transistor and powers the set side of a ...
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145 views

### How to model/get a capacitor to discharge slowly at first?

Typically, a capacitor discharges fast at first, and then discharging slows down until it approaches 0. Is there a way to slow the initial phase of discharging, so the capacitor does not immediately ...
1 vote
183 views

### How do we explain the voltage doubler operation by analogy?

The idea behind the Greinacher voltage doubler is so clear and intuitive that it can be explained, like any brilliant circuit idea, in a very simple way. I did it yesterday in a similar question where ...
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1 vote
327 views

### How does the voltage doubler work at the startup?

I have no particular interest in power electronics but I am always impressed by such clever circuit solutions as the Greinacher voltage doubler. The idea behind it is so clear and intuitive that it ...
• 9,151
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### Capacitor Current–voltage relations conceptual doubt

I understand that a capacitor stores energy on the form of voltage. However, looking at the equations for the current and voltage on the capacitor, we have the following: I was thinking here that if ...
153 views

### Charge distribution on switched capacitors

Computing the voltage and charge of these capacitors in series and parallel, I come up with a situation in which I couldn't explain why the circuit is behaving as it is. The circuit is the following: ...
174 views

### Multisim does not simulate the capacitor charge correctly

If I simulate this circuit in Multisim everything works fine, but in reality the LEDs burn, if I put a 1k resistor in series with the capacitor the LEDs no longer burn I think the LEDs are burned by ...
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1k views

### A question about relaxation oscillator

I was studying the function of this simple relaxation oscillator based on a single transistor, 2N4401. The schematic looks like this: From ...
259 views

### What happens when the voltage applied to fully charged capacitor becomes lower than initial voltage?

I have 24 volt capacitor and I charged it fully using 24 volt power supply. What happens if the power supply voltage becomes 20 volt which is connected to the capacitor that is fully charged at 24 ...
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1 vote
53 views

### Using a compartator to make an LED light up. How do I make the LED light up?

This is my circuit that lights up an LED for less than 4 seconds of volts using 4V. How do I make the LED light up? I thought the output of the comparator was the comparators supply voltage, and that ...
42 views

### Am I calculating the V(t) and I(t) of all of the elements in this RC circuit incorrectly? (two resitors and 1 cap connected to 10V DC)

Am I doing something wrong calculating the current and voltages at time t for the RC circuit? I put these equations on google sheets and the voltage across all of the elements passes 10V between 4 and ...
144 views

### Transistor activation / deactivation voltage in

The capacitor was allowed to discharge completely when the transistor was activated with the 3.4 V. The capacitor is allowed to charge again when the conduction from the 5 V line through the ...
1 vote
101 views

### Charging three individual capacitors with one AC power source

I'm trying to charge three capacitors by using my country's net voltage of 230V (60Hz) AC. The net voltage is connected to a diode bridge, which thereby results in approximately 325V DC. Each ...
41 views

### RC discharge in two ways, solving for time constant

Are the two underlined equations at the bottom correct (can I calculate an equivalent resistance for the time constant)? I understand how to find voltage and current for each element at time t ...
84 views

### Why should we charge the capacitor halfway in 555 timer circuit(as given in datasheet)?

In the Texas Instruments datasheet for LM555 IC, at Page 11 below Figure 15, the calculations for charging and discharging of the capacitor are given. In those calculations, the capacitor is made to ...
114 views

### 60A current drain on supercapacitors in series?

We have a project to build an RC car from scratch and are only allowed to use NiMH batteries, no LiPo. We're hoping to power the car with an EDF (https://hobbyking.com/en_us/durafly-vampire-v2-rcaf-...
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1 vote
2k views

### Why do the polarities of the capacitor change while discharging?

I was going through the working of class D commutation and the article said: As soon as the capacitor completely discharges, its polarities will be reversed but due to the presence of diode the ...
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### How to cut or remove the unwanted waveform?

I want to remove unwanted signal at particular time from the input signal. But I am not sure how to start this. I used capacitors to reduce the unwanted signal. It worked OK, but not well. By seeing ...
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802 views

### Why doesn’t voltage drop to 0 when a capacitor becomes fully charged?

This is my understanding so far of what capacitors are and how they work, if it helps to answer my question at a level I can understand: A capacitor is composed of two equally sized conductive plates ...
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155 views

### Simple RC Circuit question: how does a precharged capacitor interact with a lower voltage source?

So, I have this simple question to solve, but I am uncertain about some details. The circuit I have to solve is the one on the image below: I have a circuit with one capacitor(C = 1/4 Farad), two ...
61 views

### How to calculate a capacitor's discharge time? [duplicate]

How do i calculate a capacitor with a specific capacitance loaded with a specific resistance discharge time and reach a specific voltage? So let's say i have a 22uF capacitor charged with 12 volts ...
• 15
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### Current flow through capacitor

How does the current through capacitor and resistor network be decreasing from maximum, when the voltage across them is increasing from minimum? And also to my knowledge the charge that's get reside ...
2k views

### Heat lost in ideal capacitor charging

If we use an ideal capacitor to charge another ideal capacitor, my intuition tells me no heat is generated since capacitors are just storage elements. It shouldn't consume energy. But in order to ...
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### Active Discharge Options

More and more frequently I am faced with a specification that requires the ability to discharge an output capacitance to a safe level X, in time Y. The circuit I am currently working on is 2000uF @ ...
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