Questions tagged [magnetics]

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

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13
votes
2answers
6k views

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 ...
16
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4answers
28k views

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 ...
13
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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 ...
0
votes
1answer
1k views

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 ...
12
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3answers
822 views

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 ...
6
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1answer
9k views

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 ...
12
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3answers
5k views

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 ...
9
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2answers
7k views

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 ...
3
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2answers
9k views

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 ...
4
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1answer
3k views

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 ...
19
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2answers
6k views

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 ...
14
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2answers
4k views

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 ...
2
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1answer
2k views

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 ...
6
votes
2answers
729 views

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 ...
6
votes
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? ...
5
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4answers
2k views

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 ...
20
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3answers
1k views

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 ...
9
votes
1answer
2k views

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/...
5
votes
2answers
863 views

Homebuilt magnetic tape head

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 ...
2
votes
2answers
526 views

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) =...
1
vote
1answer
189 views

Cable Side and Physical Side of a PoE Magnetics

I am reading the datasheet of PoE Magnetics. I am not able to understand which side belongs to cable side and which belongs to ...
1
vote
1answer
2k views

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 ...
3
votes
1answer
162 views

Approaching an ideal inductor

It is common to see capacitors in parallel, with smaller and smaller capacitance, in order to reduce the parasitic ESR (and the equivalent series inductance). This allows obtaining relatively big ...
3
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2answers
1k views

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 ...
2
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2answers
367 views

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 ...
2
votes
2answers
8k views

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 ...
2
votes
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 ...
2
votes
1answer
1k views

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 ...
2
votes
1answer
2k views

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 ...
1
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1answer
3k views

How internal capacitor stud finders work?

I don't understand how can a non magnetic object like wood be detected using a stud finder For instance, stud finders find wood from dielectric constance, but I don't understand the princible. The ...
1
vote
2answers
632 views

How is the current induced in this circuit?

Rectangle FBCE is the conducting wire. The circle is where magnetic field exists.The perimeter of the circle is NOT a conducting wire. R1,R2,...are different resistances. If the magnetic field(B) is ...
1
vote
3answers
508 views

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
2answers
2k views

RFID + permanent magnet

A project I'm exploring requires placing a permanent magnet in close proximity to an RFID tag (within a cm or so). Can an RFID tag be read when there's a permanent EM field so close to it?
0
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2answers
92 views

Energies carried by electric and magnetic fields in plane waves

This is a newbie question. I'm trying to understand what I think must be a very basic concept with an obvious answer, but I want to be sure. Do plane wave electric and magnetic fields of equal ...
0
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3answers
76 views

The electric and magnetic components of far field EMR and shielding thereof

This is a newbie question. I'm pretty sure of the answer, but I would like confirmation. I found this thread in this forum that came close to what I was looking for, but I think my question is ...
0
votes
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 ...
0
votes
2answers
485 views

Value of inductor

I need to wind an inductor with a value between 47uH - 200uH. I have a 10 mm (in diameter) ferrite core from an RF choke used in an old radio (probably lossy ferrite). The core is 3 cm long (I also ...
0
votes
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 ...
0
votes
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 ...
-1
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3answers
199 views

Magnetic Field vs E-M Field

I have got some questions on this topic based on the best answers I get to these: -1- If magnetic fields arise due to electric currents in conductors, we say they are not E-M waves in nature; it is ...