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

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19
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2answers
3k 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 ...
16
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3answers
723 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 ...
10
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3answers
333 views

How is the state of a bit position on a hard drive measured?

Firstly, I am not the EE type, but I do have a petty good foundation on physics work on a pretty low level. I was wondering what mechanism it is that measures the magnetic indentation on hard drive ...
9
votes
5answers
1k views

How big a magnet do I need to wipe my portable HDD?

According to this article, I need a really big magnet to wipe the data off my HDD. Thing is, I don't know how strong a "laboratory degausser" is, so I'll ask it in my own terms: I have a pair of ...
9
votes
2answers
2k 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 ...
9
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2answers
507 views

How to check whether a component can work in strong magnetic fields?

I want to design my PCB to operate nicely even when we place it next to a neodymium magnet. How to check whether my component can work in such condition without shielding? Edit: I haven't face any ...
8
votes
5answers
4k views

Does magnetism affect SD cards?

Would a strong magnet have any effect whatsoever on a thumb drive (I'm assuming not) or on an SD card? It seems unlikely, but I'm hoping someone can give me a definitive answer, since I'd rather not ...
8
votes
4answers
345 views

How to track motion of a moving ovendoor

At work, we are measuring various parameters to test out a newly designed oven prototype. To make things more efficient, I am trying to create an electronic setup to automate the measurement, in ...
8
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3answers
414 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 ...
8
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2answers
499 views

Using the audio input port as a voltmeter

I'm a physics undergraduate currently studying electromagnetism. I have no experience at all with playing with electronics. I'm trying to see the effect of a changing magnetic field on a closed ...
8
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1answer
522 views

Differences between a planar coil and coplanar waveguide to create a local 1D AC magnetic field

Coplanar waveguides (for example picture look here) are often used in research to create a local in-plane magnetic field. Now if compared to a planar microcoil like this, driven by a AC voltage in ...
7
votes
3answers
996 views

Magnet that needs power to turn off? Inverse coil?

I have never heard of such thing. But it would really suit my needs. I'm inventing a device and during it's operation, it should be able to catch an iron object any time (with a permanent magnet). ...
7
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2answers
2k views

Saturation current of my inductor not agreeing with formulas

I have wound my first inductor and I have verified the inductance with 2 methods. However, when I test its saturation current, its much lower than the formula gave me: \$B_{peak} = \dfrac{V\cdot ...
7
votes
2answers
471 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 ...
6
votes
5answers
715 views

What is the difference between the magnetic H field and the B field?

Wikipedia provides a mathematical explanation. Can I get the intuitive one? I'd like to, for example, understand a ferrite datasheet. These usually have graphs of H vs B, and the definition of ...
6
votes
2answers
271 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
146 views

Fine-grained sensing of distance between two permanent magnets

(disclaimer: bit of an electronics newbie here) I have a bunch of little magnet ball-bearings that I was playing around with the other day. I formed them into a strand, then fixed both ends leaving ...
5
votes
2answers
428 views

How do I determine safe distance from a choke to prevent accidental coupling?

In most of my power converter applications, I end up with a choke of some description, somewhere in a steel chassis. I have seen and heard tell of situations where the choke couples to the steel of ...
5
votes
2answers
803 views

Sensing magnetic pulses from a rowing boat impeller

I'm a mechanical engineer at uni who has some basic experience in electronics and programming. I'm building a system for my rowing boat to help me with my training. This will give me feedback on a ...
5
votes
1answer
363 views

Magnetic field strength and bldc rotor

As a background to this project, I have taken an off the shelf bldc stator and incorporated it into a small pump, and then built my own rotor using discrete neodymium magnets. At first, everything ...
5
votes
1answer
320 views

How to choose a reed switch and magnet?

I need to use a reed switch and a magnet on a shaft. When it get turned to a specific degree the magnet will trigger the reed switch. The shaft only turns one way and is turned by hand. The problem ...
4
votes
1answer
897 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 ...
4
votes
3answers
2k 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 ...
4
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2answers
94 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 ...
4
votes
3answers
823 views

For remoting 1000Base-T ethernet connector, is it better to remote PHY from magnetics or magnetics from connector?

I'm in need of remoting the gigabit ethernet connector from the main board to a back end board that has all the other connectors. I plan on doing this with a high speed board to board connector ...
4
votes
3answers
127 views

Current source for milliohm loads?

I've been working on a model maglev train as my Grand Hobby Project; something around the H0 scale. The initial idea was to use the Inductrack mechanism to keep it simple. To summarize, a Halbach ...
4
votes
3answers
109 views

Magnetic Field Transmission

I have heard from here that if you put 1 turn of wire around your house, you can hear music all around inside your house. It doesen't tell me very much on all of the components etc. to drive but I am ...
4
votes
1answer
146 views

Maximizing force of magnetic mass accelerator

I am planning to build a coil gun to fire small neodymium magnets out of a pipe. For this I am planning to use a large 400 Farad 2.7 Volt capacitor. I am wondering how many coils of wire I should ...
4
votes
1answer
4k 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 ...
4
votes
2answers
55 views

Thickness of low frequency Mu shield calculation

I am dealing with a low frequency varying magnetic field, say 10 - 100Hz with a magnitude of 0.8T. It seems shielding at this frequency gets tricky. Even though Mu is capable of doing it, there should ...
4
votes
1answer
252 views

Simulating a magnetic field in Spice

I am trying to simulate a circuit that involves pickup coils in Spice. How would one simulate the magnetic fields that the pickup coils can sense? Additionally, how would one get a frequency response ...
3
votes
5answers
904 views

What is the best way to make a speaker louder

What are the pros/cons of adding more coils or getting a stronger magnet for a speaker? Are there other methods to make them louder keeping the power supplied to the speaker the same?
3
votes
3answers
2k views

How to convert a three wire hall effect sensor to a 2 wire sensor?

Would there be any possibility to convert a three-wire hallsensor to a 2-wire equivalent. The connections are a V+, GDD and OUT. The voltage between V+ & GDD would be 24V and the OUT port would ...
3
votes
2answers
396 views

Sending data over a magnetic field

I need to find a way to trigger this Hall Effect Sensor with a non-permanent magnet. Does anyone know if an inductor's magnetic field would be strong enough? Or am I going to have to build an ...
3
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1answer
172 views

Automobile ignition coil (spark coil)

Question: How is this possible to get 1:1000 electric potential scale while primary/secondary loop scale is only about 1:100?
3
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2answers
303 views

What are the specifics of PoE ethernet magnetics

I have a PoE powered design, and it is currently equipped with magnetics not labelled as PoE, HX1188NL. There is also a transformer with a similar topology, HX2019NL. However, the only difference I ...
3
votes
2answers
273 views

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, ...
2
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3answers
657 views

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 ...
2
votes
2answers
275 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
2answers
2k 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 ...
2
votes
1answer
128 views

Polarity of the induced voltage on inductor for an applied magnetic flux according to the Lenz's Law

I'm trying to visualize the Lenz's Law on a practical inductor. The Lenz's Law says that $$ \mathcal{E} = -\dfrac{\partial \Phi}{\partial t} . $$ Now, assume that there is a magnetic flux inside ...
2
votes
1answer
137 views

Increasing the surface area of an electro magnet

I am trying to design an electro magnet with a large surface area at the end. The first design used a 1/4" rod wound with magnet wire resulting in about 10 ohms of resistance driven with 12 V. This ...
2
votes
1answer
411 views

Digital Compass: Can it be calibrated/shielded to prevent normal operation in the presence of ferromagnetic materials

I am currently working on a hobby project, for which I would need a reliable compass that should work in as wide a range of environments as possible (i.e.: In a field, in a car, on a train, possibly ...
2
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1answer
122 views

Electromagnet interference with motorcycle

I just got a sport bike which the frame is aluminum the engine is aluminum the swing arm as well. Basically this bike is made up of mainly aluminum and plastics with very little steel or any other ...
2
votes
1answer
67 views

Electromagnet for string vibration

I recently read a lot about guitar sustainers, for those who don't know what are they - it is basically an electromagnet with an amplifier. It takes an input from pickup, amplifies it and then ...
2
votes
2answers
118 views

Back EMF and opposing current of a super conductor?

A 5 meter long super conductor carries 100 Amps, and it passes through a 1 Tesla magnetic field at 0.010 seconds, Is EMF = - (BL) / (t)? And since the resistance of the super conducting wire is zero, ...
2
votes
2answers
166 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
votes
1answer
223 views

Controlling temperature of a water bath with induction plate

I am thinking of building a sous-vide cooker using some kind of prebuild heater, controled via an AVR and temperature sensor like the LM35. There are a lot of references around using rice cookers, ...
2
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2answers
110 views

Calculation of inductance of rectangle coil

I'm currently working on a project about inductance. I want to calculate the inductance of a rectangle-shaped coil with a pitch different from zero. I tried this by applying the law of Biot-Savart. If ...
2
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0answers
388 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 ...