# Questions tagged [magnetics]

Important to inductors, transformers, generators, motors, magnetic fields, inductive heating, magnetic storage, permanent magnets

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### Ethernet Without Magnetics?

How / can you connect Ethernet devices together without magnetics? How do you wire it up? What sorts of practical limitations are there on doing this? To clarify, I'm not trying to connect two ...
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### Why is inductance (L) proportional with turns-square (N²)?

We start from the Maxwell's Equation $$\mathbf{\nabla} \times \mathbf{B} = \mu \mathbf{J} + \overbrace{\mu \epsilon \dfrac{\partial \mathbf{E}}{\partial t}}^0.$$ We take surface integration of both ...
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### What is the difference between a transformer and a coupled inductor?

Transformers and coupled inductors seem very similar. Is there a difference in construction? Or only in use? This question asks something similar, but the answers don't address my question: Coupled ...
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### Powerful electromagnet?

Is it possible to produce over 1000 lb of magnetic force over a distance of 4 inches(0.101 meters), using an electromagnet? How difficult would it be? Explaining the general spec's of such an ...
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### How to calculate air gap in flyback transformer?

I’m designing (or at least trying to design) a flyback converter on LM3478. I chose the EFD20/10/7-3F3 core [1]. Using a PDF from Infineon [2] I calculated that I need a primary winding inductance of ...
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### Does Shielding "Electrically" shield "Magnetically" too?

I know it sounds like a newbie question but I can't wrap my mind around it. An electromagnetic field is electric + magnetic field. So this means that when shielding an equipment offensively, for ...
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### How does a transformer transmit power from the primary to the secondary?

I'm trying to get my head wrapped around transformer operation and in the process regretting the times I snoozed in my Electromagnetics class as a EE student back when I was a lad :) I'm looking for ...
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### Appropriate models to model magnetic components in LTspice and what are the pros and cons?

I'm looking for appropriate models to model magnetic components, mostly transformers and perhaps for chokes as well, for use in LTspice. I've heard briefly of some models, like Jiles-Atherton-model (...
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### How do skin-effect and proximity-effect behave for flat-conductor power inductors?

Here is a Digikey search showing flat-conductor power inductors. And here is a picture of three power inductors found there: In this answer, by Rohat Kılıç, towards the end of his answer he explains ...
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### Electrical Machines based on Electric Fields

Our teacher asked us this question during the lecture for Power Electromagnetics. We know that Electric Fields and Magnetic Fields are easily transformable into one another. And they are used greatly ...
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### Does this experiment show that Kirchhoff's Law hold when there's a changing magnetic field involved in a circuit?

In this video, the electrical engineer and youtuber Mehdi Sadaghdar (ElectroBOOM) disagrees with another video from professor Walter Lewin. Basically, professor Lewin shows in an experiment that if ...
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### Ethernet: distance from PHY to magnetics

I am confused as to the preferred placement of Ethernet PHY and magnetics. I thought that in general, the closer the better. But then SMSC/Microchip app note (http://ww1.microchip.com/downloads/en/...
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### Ethernet: how important is the magnetics topology?

I have some Ethernet issues with a set of boards (6/10 are bad). They're possibly just assembly house mistakes... but I'm very concerned about my magnetics jack. I could have sworn I saw a example ...
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### How does Ethernet magnetics work?

If you refer to Figure 14 of http://www.analog.com/media/en/technical-documentation/application-notes/EE-269.pdf. There are 2 transformers on each data pair. Can someone help explain how they work? ...
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### Permanent magnets near wifi device

Background I have a small circuit that consists of a microcontroller operating on 14Mhz and a wifi module. This circuit is enclosed in a small plastic box. I am considering gluing a few magnets on ...
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I have seen a lot of projects that use a tape head, but there is very less information about how to build one yourself. Is this possible? I know that basically it is a metal core, with a coil around ...
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### How to properly wind a high frequency / high voltage transformer?

Please, is there any practical tip / caveat I should be aware, when winding a high-frequency transformer? I'm used to wind 50/60Hz transformers and they do work ok, but now I'm trying to make a high ...
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### Why is HV kept open in OC test of transformer?

Why is HV kept open in OC test of transformer? Also, why is LV shorted in SC test of the transformer? (Generally this is preferred - why?)
• 149
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### Electromagnet with iron core seems to attract strong neodymium magnet when I want to repel

I purchased suction electric solenoid cylinder electro-magnet from Amazon and I purchased neodymium magnets as well. I connect the magnet to a 12V supply and give it ~560mA. I then put the small ...
• 111
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### Core loss of an inductor

I have been trying to calculate the core loss of my inductor E70 core but I was not able to calculate it. I calculated the operating flux density of my inductor which is 104mT and compared with the ...
4k views

Just for fun, I decided to build what I was hoping would be a relatively powerful electromagnet. I used this copper wire (20 AWG, entire 1 pound spool) and this soft iron core (0.5 in diameter, 6 in ...
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### Do magnetics connectors exist?

Conventional connectors, where the plug and socket have metal parts which touch, suffer from the following problems: Limited mating cycles or expensive plating. Impedance mismatch (relevant for high ...
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### Magnetometer dynamic calibration

I am working on a Magnetometer AK8975 being a part of an IMU. Which seems to be very tricky for me. This chip gives a 3D vector as output describing earth's magnetic field at any place on earth or ...
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### How does this iPhone app measure the power flowing through an AC appliance cord?

My electric utility released an iPhone app called "DTE Insight" which (among other things) measures the amount of power flowing through an appliance's power cord by asking you to hold the cord against ...
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### Why do most flyback converters / LED drivers operate under 100 kHz?

Most of the LED drivers and flyback converters I have come across operate in the 60-100 kHz range. Is there any particular reason behind this - example - ferrite cores not being able to handle higher ...
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### What are the physical mechanisms of core loss, and how can they be minimized?

Suppose you have an inductor in a boost converter. The core gets hot. Why? What are the physical mechanisms that cause core loss? Eddy currents? Magnetic domains flipping? Coupling to materials ...
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### How to compare a magnetic loop antenna to a conventional antenna

I want to build a compact 1 MHz receive coil (antenna for very near field). For that I need to make a choice on whether to build a simple RF coil only consisting of wire and capacitors or using a coil ...
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### How important is the number of cores in RJ45 jacks with magnetics

While searching for RJ45 jacks with magnetics (MagJacks) in Digikey, we found that there is a selection criteria which says "Number of cores per jack". Though we have been using MagJacks previously, ...
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### How to route Gigabit Ethernet, remote PHY or remote RJ45 connector?

I need to design a 10/100/1000 BASE-T “backplane” board that contains multiple PHY outputs from Ethernet controller chips. On the board ,the LAN specifications are very strict in regard to how the ...
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### Why does a permanent, non-moving magnet, stuck to a long piece of metal generate a voltage?

I was just messing around with a very small permanent magnet (round) stuck to a piece of metal. The magnet is round, ~6 mm in diameter. I guess 1 mm thick. (I lack precision tools where I ...
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### Controlling an electromagnet with Arduino

I'm just starting up with electronics and looking to control an electromagnet with the Arduino. I'm wondering what hardware setup will make the most sense to use to turn the electromagnet on and off ...
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### How a switching PSU inductor overcomes the problem of saturation current?

If you open a switching step down converter like the one used in your desktop computer, you will only find that a relatively small torroidal transformer ultimately provide the power to the user. Sure,...
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### Hall effect sensor operational distance from magnet

I want to use a this hall effect sensor to detect the presence of magnet. I'm pretty sure I understand how to use the hall effect sensor, but I'm not sure how to calculate the distance the sensor can ...
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### magnetics for ethernet PIC18f

I need to add ethernet connectivity to a PIC18f66j60. The datasheets tells about magnetics. But I know only very little about that. Do you know any surface-mount magnetics suitable for this use ? I ...
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### My DIY solenoid does not work

DESCRIPTION: Hi there, I don't know lot about electricity and I`m having problems with my first solenoid-prototype, I tried to build it watching you tube videos. I have attached the pictures of the ...
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### How does flux exist in a transformer?

What I understand about working principles of ideal transformer: We apply an alternating voltage at the primary side. This creates a flux inside the transformer core ($\Phi_p$). Some voltage is ...
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### Magnetization Inductance vs. Transformer Inductance

what is the difference between transformer inductance and magnetization inductance, as I know transformer inductance is calculated with magnetization current but I've never seen magnetization ...
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### Push pull converter magnetizing current during both switch off state?

In a push pull converter during turn on a switch magnetizing current and load reflected current build up. So magnetizing inductance store energy. During both switch off state secondary coil does not ...
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### SMPS Transformer Area of Product

I've calculated the area of product needed for transformer, it's 71cm^4, but in core datasheets there is not value with cm^4 unit for example: https://www.tdk-electronics.tdk.com/inf/80/db/fer/...
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### Magnetic Encoders - Tips and Tricks

I am new to encoders in general and I am thinking about using a magnetic encoder in a personal project were I will need to make my own servo, and thus get an absolute position reading (instead of the ...
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### Turns for saturating a toroid at a particular frequency

I need to know the winding turns required to saturate a toroid for a particular drive frequency. The toroid I have is having the following dimensions OD = 19 mm Thickness = 8 mm Effective Area (Ae) =...
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### POE external Magnetics Alternative to magnetic RJ45 jack ieee803af

I can't use a magnetic jack for this POE PD (ieee803af), because we use another connector (M12). Looking for components to replace the internal magnetics, I found that almost all components and ...
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### Generating a magnetic field with an electromagnet

I want to generate an AC magnetic field. However, when trying to do this with a ferrite rod electromagnet, the measured field strength (via magnetometer) was much lower than I expected. I found out ...
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### What does limit transferable power through a transformer?

Assume that there is a transformer as in the image above. The applied primary side voltage $E_1$ is always AC. We design the transformer so that the magnetizing flux $\Phi_m$ does not saturate the ...
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### How do internal capacitor stud finders work?

I don't understand how a non-magnetic object like wood can be detected using a stud finder. For instance, stud finders find wood from the dielectric constant, but I don't understand the principle. The ...
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### ESD protection on 10/100/1000 ethernet

I am designing a PCB with an RJ45, discrete magnetics and an ethernet phy that can support 10/100/1000 speeds. I am considering the implementation of ESD/TVS diodes. For this I gathered the following: ...
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### What mechanism happens inside an inductor from the point when potential difference is applied?

What happens when a potential difference is applied across an inductor? I am trying to get a picture of mechanism from start, just after potential difference is applied in detail? In resistor we can ...
1 vote
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### How to increase an electromagnet's magnetic field size?

I made this electromagnet out of a microwave oven transformer by taking out the secondary coil. It very strong but it can only attract the metals if I bring it really close. How do increase the ...
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