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

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How detect activation loop from AMB / Mylaps transponder

I have a kart track with AMB transponder TRANX 140 and TRANX 3 decoder, That transponders has a small battery with 5 years duration, so i guess they are activated by loop just few millisecons and ...
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2answers
58 views

Ways to use electromagnets to pick up metal shavings at a distance

I work at a rotor machining plant and there is an issue for shutting a line down to clean up metal shavings, causes too much down time. I was thinking of using a strong electromagnet to have a "pick ...
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1answer
32 views

Formula for electromagnet strength parallel, outside the coil

I am working on a electromagnet project to collect metal shavings off the floor after machining. I have a formula for the magnetic strength at a distance from the ends, but not parallel to the coil. ...
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43 views

Overcoming rotor magnetic field when magnetizing stator in a Halbach motor

I am currently building a high static torque motor using electropermanent magnets arranged in a circular Halbach array as so: I've coiled magnet wire around the 12 alnico magnets making up the ...
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1answer
64 views

Magnetic switch with no moving parts

Is there a magnetic switch (like a reed switch) but with no moving parts? I need a switch that can be turned on by a magnetic field but won't move around due to tremendous shock absorption.
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3answers
58 views

Core loss appearing in buck converter ripple current

I have been told (and have also seen experimentally) that an inductor with a high core loss will introduce "glitches" to the ripple current in a switch mode power supply. I have tried researching ...
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3answers
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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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5answers
5k 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 ...
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3answers
49 views

Hall effect device for circa 1 tesla gaussmeter

I'm thinking about building an unsophisticated bench instrument for measuring magnetic field density, just to support my learning about electromagnetism and building magnetics for power electronics ...
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1answer
48 views

Externally toggle relay

Is it possible to force a relay to toggle without changing the input to the coil? i.e. if the relay (a sealed SPDT, say) has 0V on the coil such that NC is connected, it is theoretically possible that ...
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5answers
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 ...
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4answers
59 views

Suggestions for moldable ferromagnetic material?

I'm trying to build a sort of three-axis stepper motor that consists of a sphere with a permanent bar magnet embedded in it surrounded by a cube (slightly smaller than the sphere, so that the sides of ...
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3answers
55 views

Magnetic modulation/ induction

I've been looking for a viable means of communication under water (other than sonars), be it short or mid-ranged, and I have come across MM and MI. I am no engineer, so I need help with this, and I ...
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67 views

How to detect magnetic touch on a surface?

I want to restrict the detection to only sense touch with magnets. The surface is a square, about 1m² of velostat / piezo coax cable. I want to start the signal presence only if the magnet is ...
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1answer
388 views

How do electric and magnetic fields affect electronic circuits?

I have come across those requirements: "The equipment shall not be susceptible to DC magnetic fields of up to 60 μT." "The equipment shall not be susceptible to electric fields of up to 140dBuV/m ...
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2answers
73 views

Danger of Saturation of Primary Coil in a Flyback

I was reading a book, "switching power supply design - Abraham Pressman", specifically the section about flyback converters. One part I'm not quite sure I understand is where he says that the ...
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42 views

Three Phase Permanent Magnet Rotor Generator Magnetization

I have a three phase permanent magnet rotor synchronous generator. The rotor was recently removed from the machine in order to repair the shaft. The motor when when run at the same speed does not ...
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0answers
43 views

Detecting an attached magnet using HMC5883L

I am working on a project for my university using Arduino. I need to detect the change in the magnetic field when a magnet is attached to the outer body of the car. Therefore, I would like to know ...
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13answers
529 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 ...
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1answer
58 views

Will plastic influence a magnetic field?

First of all sorry for my English. If, for example I will "create" magnet by passing current through a coil. And than I will "wrap" this piece with plastic or some other material, will the "magnet ...
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2answers
137 views

Clamp Meter Working Principle

Basic theory of clamp meter to measure rms of current wave. What I have in mind is that wire creates the changing flux that induces voltage in the meter.This voltage is calibrated ? Also how does the ...
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1answer
80 views

neodymium magnet - how it affects a circuit

I am trying to develop a connector which can join both sides by a magnet. I got the idea of using a neodymium magnet , but I was thinking that if this could in one way or another affect circuit ...
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1answer
280 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 ...
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1answer
52 views

Long Term effects of saturating isolation txfr

I have a 1:1 isolation transformer that's rated for 25VA. I'm consuming 30VA, 20W. I've noticed because I'm saturating it, the txfr is no longer 1:1, it's more like 1:1.1. Other than this issue, for ...
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113 views

why cannot use permanent magnets for large electricity production

Why cannot use permanent magnets for large electricity generation as they donot require power to produce strong magnneticfield
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36 views

DC MMF and flux density variation in space

If flux density produced by DC current is sinusoidally distributed in space why do we say that DC MMF is space invariant?
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1answer
55 views

3 axis magnetometer issue in one axis

I have several 3-axis magnetometers mounted on breadboards, and they all read correctly in the x and z directions. The Y direction is very strange; when turned to read ...
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32 views

Karman Vortex Street phenomena to turn mechanical energy into electric energy at nano to mm scale?

Is it practical to use the Karman Vortex Street phenomena at a nano scale or mm level to harness the wind's mechanical energy via a carbon nano tubular structure coupled with a magnetic system to ...
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110 views

Ferrite core characterization

I need to make a dc dc converter and have some ferrite toroids but I don't have the datasheet of the cores so I need to know how much energy are capable do store the core and what current can they ...
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1answer
51 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 ...
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53 views

Is there a way to shield the fluidics of a solenoid valve from its magnetic field?

Are there any solenoid valves on the market that specifically shield the fluidics from the magnetic field of the solenoid actuation? Either by physically redirecting the fluidics around the coils or ...
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1answer
77 views

Hall-sensor replacement for reed switch

I have a device in which a reed switch is encased in potting compound. (So impossible to identify.) My problem is, that for my application the switch is too slow. I am considering replacing it with a ...
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1answer
78 views

Why don't Inductors have voltage ratings, but transformers do?

Inductors don't have voltage rating, but transformers do... why is that? Why not just put a current, frequency, and turns ratio for transformers and be done?
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2answers
125 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) ...
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43 views

Opposing EMF's with an odd change…?

A conductor in case 1 has two separate uniform magnetic fields \$B_1\$ & \$B_2\$: The magnetic fields(the blue rectangles are the field regions parallel to the conductor, while X's are the ...
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163 views

Magnet strength in dynamo design

I come from a computer background, and apologies if this question sounds elementary. While designing a dynamo, I came across a problem of how to calculate the the strength of the magnetic field, and ...
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1answer
101 views

Where can I find correct documentation of old floppy drive formats?

I have an old drum machine with an ancient proprietary 3.5" SONY floppy disk drive with no information on the device itself that I have seen. The performance is spotty and it's very picky about disks. ...
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182 views

Building an electromagnet to work over an air gap

I am currently working on a project where I am building an electromagnet that works over an air gap. Specifically a gap of about 0.3 inches. The electromagnet type was selected because I need to be ...
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2answers
338 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 ...
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5answers
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 ...
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3answers
97 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 ...
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1answer
48 views

magnetic flux cut by a magnet

I have two magnets A and B: Magnet A is movable, Magnet B is fixed. Magnet A is smaller and weaker (surface area of 1 Square cm) , where as magnet B is stronger and bigger (surface area of 4 Square ...
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109 views

Bricked IMU using a magnet?

I think I may have bricked my IMU or seriously damaged it earlier this week. I have the Adafruit 9-DOF IMU Breakout - L3GD20H + LSM303 (link: http://www.adafruit.com/products/1714) which has an ...
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2answers
204 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 ...
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2answers
24 views

Potential lose of time-dependent currents in presence of static magnetic fields

A time-dependent current (either DC or AC) that creates a changing magnetic field around the wire, in absence of other materials, only lose current in heat proportional to ohmic resistance of wire ...
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53 views

Proximity activation

My boss wants me to implement a system that only lets "allowed users" to use the machineries in our shop. Since I am an IT, I do not have any idea how to process this. I came with the idea to ...
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2answers
57 views

Can a planar transformer replace a laminated transformer for 50Hz AC conversion?

I have seen planar magnetics transformers even with isolation up to 20 kV. However those devices seem to be designed for DC/DC conversion in 100 kHz range. I am wondering whether low frequency ...
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1answer
43 views

questions on shielding static magnetic field

It seems that using ferromagnetic materials is the easiest way to shield static magnetic field. But is it still working in strong field strength(up to 5T)? Another question is that are mu-metal ...
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1answer
887 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 ...
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2answers
125 views

Flux in transformers

I have found it very difficult to find what actually happens with primary and secondary generated flux in transformers, I understand the normal transformer theory but it doesn't add up in reality! I ...