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Questions tagged [capacitor]

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

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Second - order circuits containing two capacitors or two inductors

Why is it that a second order circuit containing either two capacitors or two inductors can never exhibit an underdamped response?
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15 views

Direction of the electric field & displacement current within a rolled capacitor?

Considering that the direction of the E-field and the displacement current with a classical parallel plate capacitor are perpendicular to the plate's area; I'm not sure how they would be if the ...
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177 views

Battery-less solar generator

I have read a lot about off grid solar systems. Most of the reasons I have seen to not directly attach PV panels to an inverter without a battery are: Under voltage when not enough sunlight. Pulling ...
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76 views

How to tell if a capacitor is still good?

I was replacing a 400v 120uf capacitor in a power supply (ac 120v-19v DC 4.62 amps) well I was a dumb ass and stuck in backwards somehow. I tested the dc out end while it was still plugged in and ...
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45 views

Does voltage drop with discharge?

Does voltage drop with discharge? Since voltage is the potentiality between two charges to re-balance (from my understanding). I mean, once all charges are equally shared between both capacitor ...
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31k views

How to find the ESR of a capacitor

I am building a power supply circuit, and the switching regulator (L4963) calls for a low-ESR output capacitor. The capacitor in question is C3 of the evaluation board circuit. What does "low" mean? ...
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3answers
463 views

Choosing resistor and capacitor for active filter

I am new in designing the active filters though I designed Active low, high and bandpass and notch filter successfully (using Opamp, R and C). But these filters are not actually designed by me :-( I ...
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1k views

How to use Zener Diode in Parallel RC circuit

What I'm trying to do is allowing the current to move through only one component. In the circuit shown, DC voltage is running two components (Z & C), also charging the capacitor When voltage cut, ...
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1answer
182 views

RF Voltage Multiplier

My project partner and I are working on making a rf-dc energy harvesting circuit capable of lighting an LED (even intermittently) or trickle charging a coin cell battery over a long time. We are ...
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Sizing a capacitor for a 3 phase motor drive? [on hold]

How would you go about sizing the input capacitance to a 3 phase motor drive? The drive will be using sinusoidal control. The drive is being powered by a DC source (battery). Thanks
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44 views

Portable Guitar Amp - Distortion, Volume & GND

I have tried following the given schematic There are 3 things I am unsure of (what I tried): The Volume 5k Potentiometer: I have tried adding a volume control to the schematic by placing the ...
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2answers
58 views

What is the purpose of the resistor between the Vcc and discharge pins in the astable 555 timer?

In a standard astable configuration of the 555 timer, we have two resistors R1 and R2. The capacitor charges through both resistors but only discharges through R2, consequently, the high interval is ...
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43 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 ...
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19 views

DC link capacitor for induction motor drive

I am simulating FOC drive for a 5kW,400V 3-phase induction motor. The drive algorithm worked fine when inverter was fed from proper DC source of suitable value. However, in practice, the drive has to ...
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3answers
67 views

Need help understanding RC discharging through a transistor in a timer

Once I push and release a pushbutton I want a LED to light for say 10 seconds. I found a design for this on the web and tried it out: What I observed on the breadboard was that the LED lighted for at ...
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1answer
510 views

Make energy out of a capacitor in the sea

First of all sorry about my english it's not my mother tongue. Problem statement: A cylindrical capacitor is placed in the sea so that when a wave comes (the water goes up), the water becomes the ...
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2answers
97 views

How can fully charge a capacitor without having it prematurely discharge?

I am looking to power a circuit using a 5.5V, 5F supercapacitor. I want to charge it to approx. 5V but I don't want it to discharge into my circuit until it has charged to 5V. I can do this by simply ...
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Capacitor life hours

Working on an existing product which has had field failures. Design is a short (60ms) pulse is sent via microcontroller to activate / deactivate a latching switch. I have determined failure is due to ...
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4answers
32k views

Guidelines for determining shock hazard of capacitors

I'm looking for guidelines on how to identify capacitors which have the potential to cause pain, injury or death due to electrical shock if not handled correctly. I recently purchased a "getting ...
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321 views

Question on finding V of capacitor

I know this is an easy question but for some reason I'm not getting the correct answer. The question is: The current through a \$100 \mu\text{F}\$ capacitor is $$i(t)=50\sin(120\pi t)\text{ mA}$$ ...
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1answer
686 views

Formula of snubber capacitor capacitance for SCR dv/dt protection

I have a formula here for finding the suitable value of shunt capacitance to be put on an SCR snubber. \$C=\frac{1}{2L}(\frac{0.546V}{dv/dt})^2\$ where L is the snubber inductor, V is the DC supply ...
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1answer
24 views

Start ESP (Wemos D1) for short amount of time by pressing a button (no deep sleep)

How can I let an Wemos D1 boot on a button click, letting it execute an action and then shut down. I would like it to be wireless so it can be very flexible, and would love to not have to worry about ...
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1answer
56 views

Inrush current into capacitor bank

Given I am charging a 50uF film cap bank to 500V. Do I need a current limiting resistor or some sort of current regulator to minimize inrush current when i first turn on the power supply and/or limit ...
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32 views

Snubber capacitor VAC handling by frequency of C0G?

I'm looking for a suitable snubber capacitor (220 pf) for a boost converter. The semiconductor manufacturer recommends some ceramic capacitors for this http://www.mouser.com/ds/2/212/...
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1answer
112 views

Finding total energy for RC discharged capacitor at t = ∞?

Most Rc circuits are not as severely difficult as this kind of circuit. I'm trying to solve for both the time constant and the voltage V2 across the R2 resistor, both of which will hold the necessary ...
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1answer
87 views

THAT4315 audio analyzer - capacitors getting hot

I have designed a audio spectrum analyzer circuit with THAT4315 and a drivers for IN-13 bar graph nixie tube to visualize the signal level. To supply +-12V to the opamps, the Meanwell NSD15 module is ...
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3answers
4k views

Smart Light Switch power supply solution for 2-wire (without neutral) scenarios

Considering a smart switch based on a power greedy WiFi ESP8266 (800mA spikes and 100mA on idle, @ 3.3V), there is the common situation to have the neutral wire missing from the wall switch box (left ...
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2answers
47 views

LTSpice capacitor network simulation question

Below is a circuit build in LTSpice. It is capacitor network simulation. What is of interest to me is the voltage at node N005. A voltage controlled switch rises the voltage of node N003 to 29.42 ...
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1answer
37 views

Frequency dependent capacitor for AC sweep analysis in LTspice

I need to model a frequency dependent capacitor for AC sweep analysis in LTpsice. I see that it is possible for inductors with GLAPLACE component, but I don't find anything about capacitors. The value ...
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1answer
27 views

Class a amplifier load capacitance

What would happen in a class a amplifier if I connect a capacitor in series with the load resistor (between power supply and the transistor collector)? My goal was to block the dc qiescent current to ...
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42 views

Weak bass a bluetooth amp [closed]

I recently bought an all in one bluetooth amp for a portable speaker project. My problem is that the low end on it is only acceptable when I crank the base all the way up in the spotify eq. The ...
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69 views

How to make this circuit pass all conditions

I have this circuit (as part of a larger design): simulate this circuit – Schematic created using CircuitLab The resistors are with a tolerance of 1%. On the input, V1, the circuit gets a ...
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1answer
32 views

How to find voltage across resistors in RC Circuit with 2 voltage sources?

I've been struggling with this difficult RC circuit that asks for the voltage, Vo, across the R4 resistor. Edit: Assume that the switch has been opened for a long time, before it is closed at time t ...
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2k views

The function of a capacitor with the fluorescent lamp

What is the function of the capacitor across the supply to the fluorescent lamp when it is used?
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1answer
267 views

Power from a small engine magneto

I have a backpack mister (basically a leaf blower with a water tank) that is powered by a small 2 stroke gas engine. Another vendor sells an electrostatic charger which draws its electricity from the ...
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84 views

Ultracapacitors as a battery; how long will they last?

I would like a formula to be able to calculate how long it would take 6 2.7v 350f ultracapacitors connected in series to degrade from 14.4 volts to 11.5 volts given a parasitic draw of a specific load....
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2answers
2k views

How to gradually light up an LED

With a circuit of a charged capacitor, a resistor, and an LED, I can create a lighten up LED that gradually dims until the capacitor run out of charge. With a combination of a battery, capacitors, ...
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1answer
48 views

What is this solar power RC circuit doing?

I am a CSE student working on a project. We are using a solar powered microcontroller. The solar panel's power goes through a fuse and an RC circuit with a varistor to the charging system. What ...
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1answer
29 views

RC circuit with pulse input voltage; finding the time constants

I've the following circuit: Question: What are the time constants of the voltage at node \$\text{Y}_2\$ when the up part of the puls comes and when the down part of the puls comes? MY WORK: The ...
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1answer
1k views

Single Phase Induction Motor Wiring help

I have purchased a Single Phase Induction Motor that runs anti-clockwise, I require it to run clockwise however I am unable to figure how to change the wiring to do this, any help would be appreciated....
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257 views

Charge battery with AC [closed]

EDIT: Question 1: what type of current will be created when passing magnets past a coil? AC or DC? Question 2: What is the best way of storing the electricity generated with a contactless dynamo? I'...
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36 views

Will a start capacitor be damaged by an overloaded motor?

Background: A few days ago, the air conditioning unit at work began failing to start. Fans would turn, lights would be on, but no compressor start. I called a technician and he said the start ...
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2answers
325 views

Bulk capacitors/charge reservoir for large pulse current/current exceeding supply?

Say I have a battery that can provide 150-200mA of current continuously, but I have a module which is active periodically, and requires a large pulse current as well as a continuous current that ...
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25 views

Would it be adventageous to switch a generator's coils to maximize inrush current inductance at zero crossing?

I have been designing power supplies and have been reading a lot of research papers on how to suppress the transient voltage spikes and current transients created by inrush current. Would it be ...
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2answers
62 views

Do I need decoupling capacitors when I'm PWMing an LED?

I'm a hobbyist (well, less than a hobbyist really) trying to layout my first PCB design. I'm somewhat familiar with the concept of decoupling capacitors. I'm fading 3 LEDs in and out (really, it's ...
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1answer
33 views

Behaviour of capacitor while charging

When a capacitor is applied with an AC Wave in a circuit containing only capacitor, it charges to its peak value between the time period of 0 to 90 degrees. My doubt is that what happens between the ...
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4answers
89 views

High frequency response of capacitors

I have studied the fact that the capacitor does not like a varying voltage across its terminals, and it acts as a short circuit initially so that there is no voltage drop across it. If this is true, ...
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1answer
35 views

how do i know if Vc(0+) or Vc(0-) is zero?

i mean like in this picture, why is Vc(0-) = 10 v? why isnt it =0? when do i decide that there exists a voltage there even though it was in steady state? im not completely getting it.
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Low power analog timer circuit

How can I achieve the following: When a switch closes momentarily Hold a mosfet switch closed for about 15s. Then gradually reduce power to zero over about 4s Using little-to-no power when not ...
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2answers
41 views

What are the initial conditions used to find the coefficients in the current equations?

Suppose a RLC series circuit. R, L and C are in series with a battery and a switch. The switch is open. L and C are discharged. At t=0, the switch is closed and the battery (V1) feeds the circuit. I ...