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Questions tagged [magnetics]

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

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1answer
97 views

What is Electromagnet and inductor? [closed]

Explain electromagnet vs inductor? does inductance happens in electromagnet?
2
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1answer
111 views

How difficult is it to build a device that can read credit card data from the mag-stripe…from scratch?

I was wondering about the feasibility and difficulty of building a device that could read the information the magnetic stripe on a credit card. I think I understand the basic principles, but I'm not ...
0
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2answers
280 views

Flux density in a transformer after switch off

Consider a transformer primary driven by sinusoidal mains. In my circuit I have an NTC thermistor in series with the primary which I short out after a few cycles to limit the inrush current at start-...
3
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2answers
2k views

Air gap in switching power supply transformer

An article I have read regarding switching power supplies (https://sound-au.com/articles/smps-primer.html) says that push-pull, half-bridge, and full-bridge switching supplies don't use an air gap in ...
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1answer
113 views

Analysis of current flow at a component's edge

For one of my projects, I've designed the following component to deliver power to loads/circuits: Fig.1 The component in (Fig.1) breaks into 3 parts(a,b,c), my initial analysis of the current flow ...
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1answer
119 views

Short range wireless pulse transmission in wind anemometer

I have an old windmil-type anemometer, something like this: (Illustrative image, the real unit is 40+ year old soviet-made device with presumably no operational active components inside) My project ...
2
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1answer
69 views

How would you design an electromagnet for maximum force when you have a fixed power available?

There are number of variables like current, wire dia, number of turns, dia and length of electromagnet. The distance at which force is applied is constant The distance is nearly 12 inches. Power is ...
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1answer
65 views

acquiring conductivity through curl of magnetic field density and Ampere's circuital law

I have some question. I want to acquire conductivity and I used Ampere's circuital law. The problem is A solid conductor of circular cross section with a radius of 5mm has a conductivity that ...
1
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0answers
94 views

Why are chokes nonlinear around 0A ? What inductors do not exhibit this behaviour?

I want to demonstrate that I can control the current in the winding of my single phase motor (a limited angle torquer) with a bandwidth greater than 3kHz. The phase resistance of the motor is 20Ohm, ...
0
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1answer
126 views

hilti PX 10 TRANSPOINTER working principle

Sorry to ask this here. But I really got wondered what is this product's working principle. Anybody share what would be the core idea behind this product PX 10 TRANSPOINTER from hilti. Click here to ...
0
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1answer
390 views

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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1answer
727 views

Magnetic Lock Power Source

I have just installed a 12v 350mA 600lb Electrical Magnetic Interior Door Lock. I have tested it with a cheap 12V, 1A DC Switching Power Supply Adapter and it works just like it was designed. I have ...
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1answer
106 views

How to insert background EM noise into pathloss equation?

I am trying to understand how to add the background noise into the equation. I am trying to work out the pathloss of a radio signal over a certain distance. We have the Friis Formula for that for ...
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2answers
96 views

UAV-towed gradiometer: magnetic signal decay with water depth

I want to use an unmanned aerial vehicle to tow an airborne gradiometer. Goal is to detect historic anchors buried in the sea floor. What is the effect of (sea)water depth on the magnetic signal? Any ...
0
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1answer
115 views

Optimum physical arrangement for series connection of high-current batteries

simulate this circuit – Schematic created using CircuitLab I noticed when connecting multiple big batteries in series some people use zig zag configuration (right) instead of the one on the ...
2
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1answer
81 views

Saturation Point of a magnet given some Parameters

I know from my hard magnets (the remanent magnetization is very close to the saturated magnetization) the Coercivity \$h_c\$, the energy product \$B-H\$ and the remanent magnetization \$m_{rs}\$. Is ...
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3answers
287 views

antenna to transmit the broadband signal around 100MHz

I would really appreciate your help, since I'm not a specialist in engineering, but a biologist. I'm performing experiments where I apply RF broadband signal. I have a signal generator (Rohde & ...
-1
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1answer
71 views

Can cellphone magnetic holders affect the CPU?

My concern is mostly related to the various IC components such as CPU. I know that one of the problems of miniaturization is that electons jump to neighbouring lanes. Given how tight things are in an ...
1
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1answer
264 views

Should I remove terminating resistors in ethernet TAP?

I would like to design Ethernet TAP, with PHY, that I can connect to FPGA via RGMII interface. I know, that I could do this like there, but I would like to be able to analyze low level data in MAC. ...
0
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2answers
203 views

Can a toroidal transformer with two secondaries, inner and outer, simultaneously induce current in both?

If a toroidal transformer has two separate, concentric secondary windings, one inside the primary coil and the other outside, does the force-field which induces a current in the inner secondary, for ...
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3answers
777 views

Ethernet Magnetics Required? [duplicate]

I'm currently developing a device which require an ethernet switch on it (to provide Internet connection to a microprocessor and an iPad). One of the major goal is to make it very small. I found an ...
0
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1answer
161 views

How to choose an off the shelf transformer for DC-AC inverter?

I am designing a simple Push-Pull converter to turn ~12Vdc into ~12Vac which I then want to put into a transformer to get ~170Vac (turns ratio of 25) and then rectify it back to DC. The system will ...
0
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1answer
412 views

Two solenoid coils and ferrite rod, how to calculate mutual inductance or coupling co-eff

I have two solenoid coils, one is wounded on ferrite rod and other is wounded in larger diameter in proxmity of ferrite rod, see picture. It is used as wireless comm (simplex) between RX and TX where ...
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0answers
211 views

unstable magnetometer readings

I did the magnetic calibration here on the LSM303DLHC for a field roughly 48 uT. The method seems to have worked in that the combined bias (b) values went from ...
3
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1answer
5k views

How does a CRT television flyback really operate

I am surprised that no-one has already asked this question (unless I've missed it), because it affects all those DIY guys dealing with high voltage. I have spent hours on the web to find how to use a ...
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2answers
433 views

Why is there no attenuation in the magnetic field at the boundary of the near field?

I have used the Wikipedia FSPL formula for the farfield, and the one kindly provided by @mnsp for the near field: http://grouper.ieee.org/groups/802/15/pub/04/15-04-0417-02-004a-near-field-channel-...
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1answer
314 views

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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0answers
184 views

FSPL formula for near magnetic field?

I would like to know the precise formula for the Free Space Path Loss in case of a Magnetic Field in the Near Field region. We all know the popular FSPL formula, but this is only for the far field, ...
1
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1answer
191 views

Magnetic coupling between two coils for audio amplifier

I have a function generator that will emit an audio tone. I have two coils of wire and I'm trying to couple the audio signal from the primary coil to the secondary coil. The output of the secondary ...
2
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3answers
268 views

Designing an Electromagnet for a Digital Clock

I'm trying to design a digital clock that will use several electromagnets and iron filings to show the time. Each digit should have 7 electromagnets that turned on and off to attract the metal ...
6
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1answer
662 views

Why are there different Ethernet PHY magnetic configurations?

I'm looking at pcb-mount Ethernet ports like these: I'm seeing a few different configurations of the magnetics within the ports. On a single Wurth data sheet, there are 4: Schematic 2 is the part we ...
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2answers
139 views

Regenerative magnetic braking system [closed]

I have to work on a magnetic regenerative braking system, I already designed the magnetic brake and it works, now I need to regen the braking force (Lorentz force). What kind of motor and circuit ...
0
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1answer
77 views

Why isn't solid permalloy used for common mode chokes?

When reverse engineering a common mode choke from a line filter I found a wrap of very thin metallic foil inside the plastic housing of the toroid core. A little research on magnetic materials ...
2
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1answer
337 views

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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4answers
266 views

Can an alternating magnetic field be “informationally” shielded?

I have asked previously about the properties & shielding of the "static" magnetic field previously, where I have determined that static fields are hard to shield. However what I am really ...
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4answers
222 views

Can a “static” magnetic field carry Information? [closed]

Information is electronically represented as some energy that is changing, therefore we measure an on state (1) and an off state (0), to create a (0,1) binary representation of the information. Now a ...
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3answers
2k views

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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1answer
130 views

Switching coupled inductors in series while one is charged

I am designing a coil gun and would like to dump some energy from each coil into the next coil before (preferably) dumping its remaining energy back into its storage capacitor. If I have two coupled ...
0
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1answer
159 views

Using Linear Actuator as 'Coilgun'

If One were to have a Linear Actuator like shown below, could you efficiently use that coil as an accelerator for said Coil gun or Magnetic Linear Accelerator. I use the picture above as it is out of ...
6
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1answer
3k views

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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2answers
816 views

How does the length of a transformers core affect its properties?

I often read mentions of a transformer core's "cross-sectional area", of how it affects the transformers VA rating (although I can't find any formulas for that). But I haven't found anything ...
2
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1answer
1k views

Why are EI-cores (shell-type) most common for power transformers?

I notice that most small power transformers (single-phase, 100-240V, 50hz/60hz, laminated core) are shell-type, with an EI-shaped core. But as I understand they have relatively low efficiency due to ...
3
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1answer
1k views

Can I use an ethernet jack to send LVDS signals?

I would like to use an Ethernet jack for the form factor and CAT5e+ cable properties (shielded/twisted, characteristic impedance, etc) to send LVDS signals over a long length of cable (100+ ft). When ...
0
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2answers
236 views

Using Electricity and Magnetism to Lift non-ferromagnetic Copper Pennies

Is there any way (If you pumped a lot of current through a copper penny by shorting a circuit out through it with leads on either end) to create a magnetic field in the penny and lift it with a (very ...
1
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1answer
979 views

What do pull-up and pull-down resistors do in an ethernet PHY?

I've noticed that most ethernet physical layers (i.e. the interface between the MAC/network and e.g. an RJ45 connector with magnetics) have pull-up or pull-down resistors on the TX and RX lines. For ...
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1answer
51 views

Does calculation of resistances in parallel apply to magnetic circuits too? [closed]

Like the title says. Is 1/Rges = 1/R1 + 1/R2.... for magnetic resistances true aswell? E.g. can we say that Rpar = R1*R2/(R1+R2) with magnetic resistances in parallel?
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2answers
224 views

how to lower reactance of an electromagnet?

I have an electromagnet that I want to switch on or off quickly. After making the prototype I found that the magnetic force remains for about 1 sec after I turn the current off . This is a problem as ...
0
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2answers
181 views

Magnetic resistance of an electromagnet with varying cross section

I've been given the following problem: The magnetic flux density (B) of the air space should be 0.5T. I=5A and the coil has N=200 turns. Calculate the length of the air space e. What I've done so ...
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2answers
220 views

Why would running the coil cable straight for ~10 inches affect metal detector sensitivity?

Metal detecting enthusiast here. I have been reading various posts pertaining to sensitivity of metal detectors. It is has been suggested that instead of immediately wrapping the coil cable around ...
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4answers
2k views

What effect does Permanent Magnet have on an air-core coil?

Given an air-core coil of known inductance and a given frequency of applied voltage, you can predict the coil reactance, the current, and the voltage/current phase relationship. What effect, if any, ...