Questions tagged [capacitor-charging]

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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 ...
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2answers
42 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: ...
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1answer
36 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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2answers
999 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 ...
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3answers
114 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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1answer
42 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 ...
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1answer
37 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 ...
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1answer
41 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 ...
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1answer
85 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 ...
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1answer
28 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 ...
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1answer
48 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 ...
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1answer
89 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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1answer
174 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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3answers
174 views

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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2answers
123 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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0answers
41 views

Joule Thief powered HC-SR501 PIR Motion Sensor & LED string

Following BigCliveDotCom's YouTube video, I was able to build a joule thief. I then built a HC-SR501 PIR Motion Sensor lighting a 4.5v string of LED fairy lights powered by either a 5v wall wart. or ...
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1answer
70 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 ...
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0answers
44 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 ...
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2answers
92 views

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 ...
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5answers
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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2answers
54 views

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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0answers
92 views

Transfer of Energy from Initially charged capacitor to uncharged Capacitor

I have started to learn about LC circuits, Specifically, I am simulating a case where the initial conditions are where one large capacitor (100F) has previously been charged to 1.3V, considering the ...
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2answers
116 views

Crockcroft-Walton Voltage Multiplier Large Voltage Loss

I have a CW voltage multiplier that uses 30kV, 1nF capacitors and doubled 20kV, 5mA, 100ns diodes (for a total of 40kV). My ac source is a sine wave (viewed on the primary side of the transformer ...
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1answer
62 views

Low power device with high current peak

I'm creating power supply for controller that usually operates with very low power consumption, but sometimes needs high power. To make the situation harder there is "sometimes" external power present ...
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2answers
229 views

LTSpice - Capacitor Charging/Discharging Circuit not working right

I am trying to do a charging and a discharging Circuit. R8 is the load that Capacitor C1 needs to discharge into when P12V_IN is low. My question is Why is Vsolenoid low in the interval shown on the ...
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1answer
48 views

Multistage capacitor charging

I am currently building my first coilgun. I already have MOSFETs rated at 100V, and 50V 470uF capacitors I can wire in series to obtain 100V. I know this voltage will not result in a very high ...
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2answers
396 views

Charging a high voltage capacitor with power supply. How exactly?

I have a semi-serious hobby project with a couple of friends where we need to charge a pulse operated capacitor rated to around 4kV with 1500nF capacitance. For this I need a high voltage supply and ...
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0answers
57 views

Ultracapacitor doesn't charge

I am concerned about an ultracapacitor (2.7v, 3000F) that I received today. I set my power supply to 2.5v with a current limit of 1A, then connected a diode to the positive lead such that current ...
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1answer
99 views

How do I charge a capacitor?

So I have a 270uF 350v capacitor that I am trying to charge. The schematic shows a the right size for a 22uF, how do I know what size resistor i need to charge it? What type of transistor do I ...
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2answers
517 views

Solar powered LED via capacitor?

I am building a large garden peice in wood, which I hope to illumine from within, powered by a small, (perhaps 90x65, 6v, 0.6w 100mA as space is limited) solar panel. After testing, I noticed that ...
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3answers
2k views

How to Measure Very Large Capacitance e.g. Super/Ultra Capacitors

I have recently acquired a couple of mysterious ultra/super capacitors from my brother. Apparently he doesn't remember any of the specifications or even brand... To further complicate matters, they ...
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0answers
157 views

Marx Generator For Quick Discharge of Capacitors On Inductor

Hello guys! My goal was to charge these two capacitors with a dc generator as shown in the schematic using a Cockcroft-Walton generator which has worked in the lab perfectly. The capacitors are ...
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2answers
1k views

Supercapacitors in series

Can I charge series of 4 Maxwell BCAP3000 supercapacitors with constant current method using an adjustable Power Supply, and exceed the voltage rated for single cell? What I mean is to charge the ...
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3answers
97 views

Capacitor not reaching supply voltage with LED in series

Totally new to electronics here. Without the red LED "charging indicator", the capacitor charges fully to 10V, but with the diode the capacitor maxes out at about 8.42V. I don't understand why the ...
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2answers
571 views

Why is the voltage of a capacitor equal to the voltage of a battery connected it?

I am confused by this question. If we connect a resistor in series to capacitor then the voltage will drop across the resistor and now voltage across the capacitor is less than the source, then why ...
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1answer
475 views

How do I charge a 2100v 0.95uF capacitor? [closed]

I'm trying to make a rail gun, and I am using 4 microwave capacitors for the extra kick but I don't know how to charge them. I would like to know how charging capacitors works and what I'll need to ...
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1answer
88 views

Can someone explain the working of this Surge Suppression Circuit

This is an old circuit which is still being used. I am curious to understand that if 600 VAC is applied to AC side of the three phase rectifier which has diodes, and on the DC output side of the ...
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0answers
87 views

Capacitor for handling startup current of DC-DC converter shows different behavior

I’m using a 5V DC-DC converter to step-up a coin cell (Nominal Voltage: 3V) to 5V which did not work. I suspected that the high startup current of the converter was causing the Cell voltage to drop, ...
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2answers
130 views

Is driver necessary to drive P-FET Buck Converter using Microcontroller?

I'm building a buck converter to charge an ultracapacitor from Hydrogen Fuel Cell. I'm having some issue with the gate switching for the converter. Currently I'm testing the buck converter with a ...
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1answer
44 views

Capacitor Charging Voltages

I am trying to create a capacitor bank and don't know what voltage to put through. Do i add the voltage of all the capacitors up and apply that or just provide the voltage for one. e.g. If I have 10 ...
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1answer
80 views

Self powering torch - boost converter calculation

I was implementing the TPS61200 Voltage Boost Converter from Texas Instruments in my circuit to boost the voltage output from some Peltier tiles to then power a supercapacitor which would then power ...
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2answers
665 views

ZVS driver charging capacitor bank

I built this ZVS driver to make some big high voltage sparks a while ago. It worked off three voltages 24V, 50V, and 80V and had no issues. The only part of it that got really hot were the 1kohm 3W ...
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0answers
97 views

Suitable Capacitor

I am wondering what voltage rating I need for the capacitor in the attached circuit. Its basically the front end of a Tesla coil. The voltage source is a neon sign transformer 3kV open circuit at up ...
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3answers
2k views

Discharging one side of a capacitor?

What I'm asking about is if it's possible to discharge one side of a capacitor. I've found a question about that, but I also found the answers to be a little unclear or questionable. I imagine that ...
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1answer
3k views

Creating a timer in an RC circuit

In the book "Electronics For Dummies" there is a paragraph called "Creating a timer". If you’ve got a buzzer that requires a voltage of 6 volts in order to sound off, and you’re using a 9-volt ...
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1answer
74 views

24vdc current boost?

I have a access control system that applies 24vdc to a solenoid to unlock a door. The power supply is 24vdc 16a inrush, 1a constant. Due to the wire size and distance it doesn't always pull it ...
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1answer
2k views

Simple Capacitor charging and discharging question

Below is a circuit consisting of a capacitor, voltage supply and resistors. There is a switch that lets the capacitor charge and discharge. I have also uploaded the given answers below; I understand ...
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1answer
385 views

Op-amp bias issue to to charging of DC blocking capacitor

We're using the above circuit to drive a sinusoid with constant current into a custom sensor which is best modeled as a series capacitance & resistance (~100ohm, 1uF). The op-amp is single supply, ...
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1answer
318 views

Does this capacitor discharge? SCR and capacitor doubts

I'm having some doubts about this circuit and about capacitors charge/discharge in general SCR CIRCUIT; Igt= 100MicroAmps;Vgt = 0.7V Ok I have like 5 questions 1) Is flowing current through R2 and ...
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3answers
720 views

Does resistance affect a capacitor charging from another capacitor?

Consider two capacitors connected to each other, where one is charged (5.0V) and the other has no charge stored: When they are connected, current flows to even out the charge and the resulting ...