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33 votes
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How to calculate air gap in flyback transformer?

Power output and energy per switching cycle An output of 265 volts at 5 mA is a power of 1.325 watts and this means that the energy that needs to be transfered each switching cycle is 1.325 W divided ...
Andy aka's user avatar
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30 votes

Help with homemade electromagnet

20 AWG wire is about 33 mΩ/m, wikipedia so I'd estimate the resistance at around 3.3 Ω Into that load, your 9 V batteries are acting as current sources, not voltage sources. You will get a better ...
Neil_UK's user avatar
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25 votes
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Why do most flyback converters / LED drivers operate under 100 kHz?

There are many reasons: - Cost: This is probably the biggest reason. The lighting market is quite competitive. There are lots of Chinese players offering aggressively cheap prices. This forces the ...
Rohat Kılıç's user avatar
25 votes
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Why use aluminum wire in an (old) TV degaussing harness

In consumer electronics there is only one reason. Price Saving 10c each on a run of 100,000 devices saves $10,000 the degausing coil doesn't need to be compact or have to low skin-effect losses so ...
Jasen  Слава Україні's user avatar
23 votes
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Very small transformer powering a microwave oven

If you double-check your wiring diagram you will find that is NOT a transformer. That is a common mode choke to keep RFI from being transmitted out through the mains power cord. There is no way (with ...
Richard Crowley's user avatar
23 votes

Why does a permanent, non-moving magnet, stuck to a long piece of metal generate a voltage?

You are not actually measuring anything about the circuit because the leads are plugged in incorrectly. The negative black lead is stuck into multimeter current measurement input, and positive red ...
Justme's user avatar
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22 votes
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How does Ethernet magnetics work?

There are a few bad things that the system was designed to mitigate, one is ESD, noise and ground loops. The first transformer (up down one) is an isolation transformer, it passes the high frequency ...
Voltage Spike's user avatar
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20 votes

Very small transformer powering a microwave oven

As an amplification of Richard Crowley's answer, I'd do this in a comment but there is no way to include a circuit diagram. Your circuit actually looks like simulate this circuit – Schematic ...
WhatRoughBeast's user avatar
18 votes
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Where are Ćuk converters

There are a few reasons. Polarity Ćuk converters must always have opposite input and output polarity. This makes them somewhat inflexible and would prevent them from being used in any application ...
metacollin's user avatar
18 votes
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Why does a permanent, non-moving magnet, stuck to a long piece of metal generate a voltage?

My guess is it's a Galvanic cell. One electrode is your metal strip (maybe nickel), the other is your magnet whatever it's made of (or coated). The electrolyte is probably sweat or saliva (you used ...
Nyos's user avatar
  • 462
16 votes
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Does Shielding "Electrically" shield "Magnetically" too?

You would not be alone in this one. This is an often misunderstood phenomenon. Static magnetic fields can not be shielded. They can be re-directed using ferrous materials but even those will not ...
Trevor_G's user avatar
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16 votes
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Sampled 100 Hz sinusoidal signal from Hall sensor shows 10 Hz sidelobes when sampled at 500 Hz

If the sensor is set to 500 Hz sampling, and you have a MCU timer also set to 500 Hz to read the results, this is never going to work, because nothing is ever exact, especially devices with internal ...
Justme's user avatar
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15 votes
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Construction for a homogeneous field using permanent magnets

The magnetic field in the region between the arms would be relatively uniform in direction, but non-uniform in intensity. Below, I've attached an image of the field that I made using very simple ...
Hearth's user avatar
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15 votes

Why use aluminum wire in an (old) TV degaussing harness

Reasons for using aluminium wire in a CRT degaussing harness: The lower electrical conductivity of aluminium (only 63% that of copper) would be good enough for the degaussing application. The lower ...
vu2nan's user avatar
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15 votes
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Why does this metallic magnetic core have so little core losses up until 100s of kHz?

Take a look at this cross section of a tape-wound core from https://www.magneticmetals.com/products-materials/tape-wound-toroidal-cores : I have added the arrow to show the direction of the eddies ...
John Birckhead's user avatar
14 votes
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Why do Rogowski coils work for measuring current?

A Rogowski coil is not a current transformer. The current in the main conductor generates a magnetic field round itself. The Rogowski coil samples the field, generating a voltage as the field changes....
Neil_UK's user avatar
  • 168k
14 votes
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What does this beautiful 8-winding magnetics do?

This could be part of an electron beam stigmator. A solenoid with an axial magnetic field can focus/defocus an electron beam. If you have 2nd order and higher astigmatism to correct, you need higher ...
tobalt's user avatar
  • 22.3k
14 votes

How to design a 12V to <100mV 15A DC-DC converter?

Your requirements are quite close to the CPU VRM found on a PC motherboard, which outputs around 1V at huge current (50-100A). So you should be able to find the same parts, which are available and ...
bobflux's user avatar
  • 79.2k
13 votes

Help with homemade electromagnet

"The Cool Magnet Man" provides an excellent tutorial on the practical aspects of the design and winding of your own electromagnets here This is a summary of his procedure: Before you can ...
tlfong01's user avatar
  • 2,916
12 votes
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Can I swap TX+ and TX- (and RX+ and RX- ) using ethernet magnetics?

As long as the RJ45 connector line pinout adheres to the standard, you shouldn't have any problems. The magnetics are a passive device, they don't care about RX + or RX-. You can even get away with ...
Lior Bilia's user avatar
  • 7,590
12 votes
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How do I build an electromagnet?

I'm sorry, but you need to find a new project. Lifting a paper clip at 8 inches will require an extremely powerful magnet. If you still want to see what you can make, you need to change your wire ...
WhatRoughBeast's user avatar
11 votes
Accepted

Does this experiment show that Kirchhoff's Law hold when there's a changing magnetic field involved in a circuit?

The lumped component models to which KVL is applied are just that--models. Like all models, they are only accurate to the extent that they represent the relevant characteristics of the system they ...
ajb's user avatar
  • 3,434
10 votes
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low frequency 1-10Hz transformer

You can use a mains transformer at lower frequency, but you have to lower the input voltage to keep it below saturation. At normal operating frequency the inductive reactance of the primary winding ...
Bruce Abbott's user avatar
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10 votes
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How can single phase induction motor's direction be reversed?

Typically reversing the fan motor is done like this, an SPDT switch changes which end of run capacitor is connected to the feed, and in doing so changes which winding sees the advanced signal. ...
Jasen  Слава Україні's user avatar
9 votes
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Is magnetic hysteresis present even with a DC bias?

By adding a DC bias, you are just shifting the hysteresis loop to another operating point. You are not eliminating it. The smaller the AC component of the current, the smaller the hysteresis loop and ...
Lars Hankeln's user avatar
  • 2,763
9 votes

How do I build an electromagnet?

Here's an example electromagnet you can buy: ELECALL electromagnet. The datasheet shows that the most powerful model (the ELE-P100/40) can run at 12 volts at 1 amp (12 Watts). The lifting force at ...
Xavier's user avatar
  • 191
9 votes
Accepted

What to connect to center-taps of Ethernet magnetics?

The basic way PoE works is there is a pair of transformers on each end. On the end that sends power (PSE - Power Sourcing Equipment) the secondary of the transformers are center tapped and voltage is ...
GodJihyo's user avatar
  • 24.4k
9 votes

Why does this metallic magnetic core have so little core losses up until 100s of kHz?

Vitroperm is not a metallic material, it's an nanocrystalline alloy (ultra fine grains of FeSi are embedded in Nb and Cu additives). Transformers made of this type of materials are commonly used in ...
Ken Grimes's user avatar
  • 1,309
8 votes
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What is the purpose of perpendicular "smaller" magnets in between the main magnets in a rotor of a motor? had never seen this before. Do they help?

This is more or less just transferred from Wikipedia, however: As @HarrySvensson indicates, this is a Halbach array, apparently used to create a magnetic field that is stronger on one side than the ...
K H's user avatar
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