# Tagged Questions

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

5k 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 ...
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 ...
7k 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 ...
2k views

### Why are reed switches made in glass tubes?

Why are reed switches made in glass tubes? Reed switches sense magnetic fields, and glass is not the only material not affected by a magnetic field. They can use plastic for example. Why are most of ...
3k 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 ...
2k views

### Can a transformer work if the core is not circular?

I am trying to build a transformer to convert 12V AC power to 5V AC. Here is what I have right now: I haven't adjusted the coil ratio yet but I tried it just to see if there would be any output ...
765 views

### Tracking rotation with extremely high accuracy

I would like to track the angular position of a fairly slow motorized rotating arm (direct-drive; see illustration below) -- but require angular accuracy of under 0.05°, and similar resolution. As @...
418 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 ...
1k 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 ...
13k 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 ...
4k 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 ...
2k 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 ...
4k 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 T_{...
307 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 ...
974 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 ...
9k 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 ...
6k 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). ...
540 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 ...
765 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 ...
849 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 ...
686 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 ...
444 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 ...
175 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 ...
3k 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 ...
118 views

### Where are Ćuk converters

According to "the art of electronics" (p 651) and other internet sources, the ćuk switch converter has the most desirable properties: continuous input and output current waveforms, boosting and ...
604 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 ...
1k 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 (...
1k 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 ...
846 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 ...
867 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 ...
119 views

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 ...
236 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 ...
252 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 ...
136 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 ...
150 views

### 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 ...
388 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 ...
5k 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 ...
106 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 ...
501 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 ...
8k 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?
2k 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 ...
4k 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 ...
779 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 ...
278 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?
1k 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, ...
497 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 ...
497 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 ...
215 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 ...