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1 vote

Capacitor in AC

The 4 diode switches or a diode full-bridge rectify the positive current with twice the input frequency and almost the same voltage minus the 2 alternating diode pair forward voltage of 0.7V x2 ...
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0 votes

Old sewing machine motor filter/capacitor schematic/wiring

About: Can anyone help me decipher the schematic so I can replace it using individual capacitors? I found here this quad-capacitor showing the diagram more clearly - just in case, I marked the ...
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2 votes

Capacitor in AC

I don't understand what is the reason that the value of the capacitor amperage decreases after every phase? I was supposed that the amplitude would be the same in each phase, but it decreases. After ...
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1 vote

Replacing blown out capacitor in old projector

About the capacitor and pictures in the link, I did this collage, highlighting the C1 you mentioned in the lower right side. I also saw another Capacitor - an Electrolytic one, inserting a zoomed view ...
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1 vote
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Why do audio amplifiers have many capacitors in rows?

Polar e-caps tend to be selected for ultralow resistance, ESR to improve the attenuation of RF from the series L and DCR resistance. The actual equivalent circuit of most caps looks like this. Keep ...
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7 votes

Why do audio amplifiers have many capacitors in rows?

One reason is that large value capacitors tend to be taller, using multiple shorter ones allow them to fit into the same height as the rest of the circuitry. Another reason is that capacitors have ...
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3 votes
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Interview Question

The input signal, say \$V_{in} \$, is the non-inverting input to the transconductance amplifier. To determine the OLTF, remove the feedback path, giving, $$\frac{V_{out}(s)}{V_{in}(s)}=\frac{10^{-4}}{...
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2 votes

Interview Question

I was thinking to find the Transfer function but the problem is no input is given. Inputs are "given", because the two inputs are the inputs of a "substractor". I have simulated &...
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2 votes

Capacitor circuit - thinking about electrons

Electrons chug along fairly slowly and so to get, for example, a bulb to light almost instantly when a switch is closed requires that many, many electrons are being delivered to the bulb at any one ...
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9 votes

Capacitor circuit - thinking about electrons

Your premise that a 'single electron flows into the plate' is false. While electrons are discrete, electric fields are continuous and are made up of the influence of a very large number of electrons. ...
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5 votes

Confusion In RC circuit

Were you to solve the differential equations for this circuit, you would find that the voltage across the capacitor always is predicted by this equation: \begin{align} V_C(t) &= V_\mathrm{f} + \...
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5 votes
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Confusion In RC circuit

I can't say where you went wrong with your math but, in this simple example of an RC network, whenever the voltage source instantly rises to 5 volts from 0 volts or instantly falls to 0 volts from 5 ...
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2 votes
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Series and Parallel Capacitors in Circuit Analysis

This is what you have after step 4: Two \$10 \mu F\$ capacitors in series: \$5 \mu F\$ Two \$5 \mu F\$ capacitors in parallel: \$10 \mu F\$ The previous result in series with \$6 \mu F\$ and \$3 \mu ...
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1 vote

Designing a common emitter audio pre-amplifier

Why are you overloading the circuit with a 350 ohms load? An audio preamp usually drives an amplifier with an input resistance that is 20 times or more the output impedance of the preamp. Then your ...
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7 votes
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Designing a common emitter audio pre-amplifier

Re-drawing of schematic For my own clarity, if that of no others, I'm re-drawing your schematic as follows: simulate this circuit – Schematic created using CircuitLab I'm keeping the schematic ...
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0 votes

Distortion Pedal Design

Those are DC blocking capacitors. The op-amp has DC bias voltages on it, the capacitors keep those from affecting, and being affected by the rest of the circuit, while still passing the AC audio ...
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0 votes

Series capacitor not blocking DC voltage

Think about the basics that depend on time constants and duration and the possible differences between your schematic and your actual circuit that would cause 50 to 100 mA current spikes on each edge ...
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0 votes

Series capacitor not blocking DC voltage

Your circuit has a DC voltage on the right hand side of the capacitor because the diode shunts away part of the voltage during part of the cycle. In essence, the diode is taking what would otherwise ...
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3 votes

Does the conductivity or resistance change the capacitance value if I use other material for my capacitor plates?

Without going deep the way Sir @Neil_UK answered your question, my quick answer to your question is: No. Changing plate material (thus changing the plate resistance) will not change the Capacitor's ...
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2 votes

Does the conductivity or resistance change the capacitance value if I use other material for my capacitor plates?

Lower conductivity in the plates of a capacitor increases the power losses, without changing the capacitance. This effect only becomes significant when the operating frequency is high enough that the ...
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0 votes

Does the 7809 need an input bypass capacitor if it has large output capacitors in parallel?

You may want to check that 78xx schematic. To the best of my knowledge, pin 2 is GND and pin 3 is OUT. I stumbled upon this looking up the pinout on google and it might confuse some folks, causing ...
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0 votes

Can a non-electrolytic capacitor be made from activated carbon?

Maxwell supercaps that have the same carbon electrode material, they say are "non-polarized in theory". But in practice, it makes a difference in the long term even though in the short term ...
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-3 votes

RC Timer Circuit (fundamental) Misunderstanding

In electricity, there are two types of devices. Ohm's Law devices, and switch-type devices. (The things they never tell you in formal education make life so much more difficult for the uninitiated to ...
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0 votes
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To decouple or not to decouple these LEDs/drivers?

The first device is a simple analog circuit and does not depend on supply impedance (including the need of bypass capacitors). The second one seems to have more active circuitry inside it, but also ...
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2 votes

How can I generate 1200 kV with a 15 kV 30 mA 60 hertz NST?

Beyond about 10:1 the multiplier method gives rapidly diminishing returns with reasonable assumptions. Read a paper on it maybe 25 years ago (Cockcroft-Walton type). Neon sign transformers have ...
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0 votes

Why is a capacitor considered a short circuit at start up?

We get the differential equation for capacitors, \$i(t) = C\frac{dv(t)}{dt}\$ from physics. I really like Greg Durgin's videos on applied EM. As others have mentioned, the voltage across the capacitor ...
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0 votes

Vdc in ripple factor

Vdc = Vac RMS x SQRT2/(1+1/2frc) ac, rectifier, capacitor filter, load resistor. f is ripple frequency after rectifier, c is Farads, r is OHMS.
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8 votes
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Why is capacitor discharge time higher when an LED is included?

The short answer is the "voltage drop" of the diode, but the longer answer is the non-linear I-V characteristic of the diode. In hand-wavy engineering we resort to a simplified piecewise-...
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5 votes

Why is capacitor discharge time higher when an LED is included?

If you’re putting the LED in series with the resistor then the discharge current will be significantly lower, and will drop almost to zero when the capacitors discharge to the forward drop of the LED.
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11 votes
Accepted

What is the meaning of temperature characteristics in capacitor datasheet?

It refers to the capacitance variation over temperature for Class 2 ceramic capacitors for a Y5T dielectric. Here's a table from Wikipedia on Ceramic Capacitors: The +22/-33% rating tells you that ...
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2 votes

Problem with building -12/12 V power supply and AC/AC converter

Are you actually measuring an AC voltage here? If you are using a basic multimeter, it may be misleading you. The simplest way to measure AC is to feed the AC voltage through a precision rectifier, ...
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4 votes

Problem with building -12/12 V power supply and AC/AC converter

Your circuit looks fine. You shouldn't get 20V output even at no load. You likely have something mis-wired. Certainly if the diode is backwards that would account for it. If you're not sure it's ...
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4 votes

Problem with building -12/12 V power supply and AC/AC converter

"I wonder if the problem is with the converter schematic or with the power supply?" My money is on the schematic. 7812/7912 regulators aren't actually specified at no load. Try connecting a ...
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5 votes

Problem with building -12/12 V power supply and AC/AC converter

AC voltage is normally stated as an RMS (Root Mean Square - a "sort of" average value). If you rectify an AC voltage with a diode and capacitor, the resulting DC voltage will be about 1.4 ...
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4 votes

Why is a capacitor considered a short circuit at start up?

This clearly is a contradiction. Can someone explain how this theory works? Let's try to explain using fundamentals. Here's the basic capacitor current-voltage relationship: $$ i_c(t) = C \ \frac{d}{...
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4 votes

Why is a capacitor considered a short circuit at start up?

When the circuit is powered off, the capacitor sees a 0 Hz (zero hertz) signal which, by chance, is at level 0 V (zero volt). When you power on, there is a transient: 0 volts change to X volts. That ...
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17 votes

Why is a capacitor considered a short circuit at start up?

You are mixing up two very different concepts. When you talk about impedance you are implicitly examining the behavior of the system in an AC steady state condition, i.e. when excited by a sinusoidal ...
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3 votes

Why is a capacitor considered a short circuit at start up?

Because you do not have infinite energy. The voltage across a capacitor is proportional to the charge on its plates. This means that during a transient, such as the charging at start up, the voltage ...
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6 votes

Why is a capacitor considered a short circuit at start up?

This phenomenon can be better explained in time domain than in frequency domain. Strictly speaking, a capacitor is not a short connection since its terminals are separated by an insulator. It rather ...
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6 votes

Why is a capacitor considered a short circuit at start up?

You are mixing up two different operating regimes for the capacitor. In the case where a constant AC sinusoidal waveform is put across a capacitor the impedance = 1/2.pi.f.C. In the case where a DC ...
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1 vote

Measuring capacitance with STM32

In order to use measure capacitance and inductance we use AC sources. Emulate a AC sine source using the microcontroller , make a Sauty bridge then feed the differential input of the Sauty bridge to ...
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1 vote

Measuring capacitance with STM32

The proper way to measure capacitance is with a constant current or by impedance ratios at some frequency. Consider the timer method. Use two threshold voltages, (one could be 0V) with a difference ...
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2 votes

Will this charge a capacitor?

A nail in the dirt is not a ground. In any case, no grounding is required. Here are three ways for you to charge the capacitor. Using a single diode. Using two diodes. Using four diodes. It should ...
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4 votes

Measuring capacitance with STM32

You have the GPIO going to the capacitor through a 1 Meg resistor, and then you've connected the ADC input to it. What is the impedance of the ADC input? If I read the datasheet correctly it is 50 k. ...
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0 votes

Will this charge a capacitor?

Sure the C T is the accepted way to go .Sure the 4 diode fullwave bridge will do this when a CT is not present .If you want to use just 2 diodes with no CT you could place 2 resistors to ground one on ...
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2 votes

Will this charge a capacitor?

Somebody removed the grounded center-tap:
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1 vote

DC-DC booster functionality

The inductor alternately stores energy as magnetic flux, and releases energy as current. transistor on: ‘charging’ L1 (building flux) transistor off: ‘discharging’ L1 (collapsing flux) During that ...
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