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

learn more… | top users | synonyms

1
vote
2answers
40 views

Why is HV kept open in OC test of transformer?

Why is HV kept open in OC test of transformer? Also, why is LV shorted in SC test of the transformer? (Generally this is preferred - why?)
2
votes
2answers
128 views

How build coil for respiratory magnetometer or find a better option (hall effect)?

I am trying to build an respiratory magnetometer. This device is no longer widely used even thought it was well liked. The reason it is no longer used is due to the fact that the coils used in it were ...
1
vote
1answer
108 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 ...
1
vote
0answers
25 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 ...
0
votes
1answer
32 views

Inductor Core Loss: Volt-uS vs. Irms vs. Switcher Frequency

For DC to DC application, I see these charts often for inductors, but I don't understand what they actually mean. What does this chart mean, and how does it relate Volt-uS, Irms, & Freq? Edit: ...
2
votes
3answers
105 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 ...
2
votes
1answer
42 views

Create a vest to detect contact

I want to make a laser hunt type game with my son using Nerf Guns. I can modify the Nerf bullet to put some sort of device on the top of the bullet (obviously something not too heavy). It would be ...
3
votes
1answer
533 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 ...
1
vote
1answer
32 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 ...
0
votes
0answers
125 views

Two RJ45s one PHY

Is it possible connecting two RJ45s to a one port ethernet magnetics? If yes, Does it require just turns ratio adjustment or other issues have to be taken into account? Thanks!
1
vote
1answer
50 views

Magnetic contact circuit

Which is the best circuit for using a magnetic contact for turning on a LED strip? I would like to turn on a strip led with 12V 7A battery, but: 1 - if I use only the magnetic contact it will be ...
0
votes
0answers
32 views

Shielding of magnetic flux with copper plate

Where in the copper plate do the eddy currents lie, and what are their phases, relative to the source current? Does this phase vary with frequency? 1) As far as i know the eddy currents will be on ...
-3
votes
2answers
60 views

Extend an rj45 Jack

I want to extend the Ethernet port (of my raspberry pi) using a short bit of cable plugges in into the Ethernet Port and solider to another rj45-jack. In the jack I have here, are some built-in coils ...
0
votes
1answer
36 views

Which is the best material to create a magnetic field?

I'm trying to create a magnetic field and I'm also trying to induct electricity wirelessly to a light bulb. What I have to do is create a round coil but I'm not sure what is the most conductive ...
1
vote
1answer
335 views

How to Estimate Rotational Velocity of a Beakman's Motor?

What is the equation to determine the rotations per second of a Beakman's Motor (a.k.a. half-motor or single pole pulse motor, composed of a power source and a single coil with 1/2 exposed coil leads ...
-1
votes
1answer
70 views

Motor without magnetism [duplicate]

Every electric motor I know, takes electricity and converts it over a magnetic field, for generating movement. Is it possible to generate significant movement, based only only on electrons movement? ...
0
votes
1answer
128 views

Super fast magnetic field by an electromagnet?

Was wondering about the possibility of creating a magnetic field in milliseconds or less? I know it's possible based on certain labs achieving 60-100 Tesla and more. But what about creating a 2 - 5 ...
9
votes
3answers
185 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 ...
0
votes
2answers
123 views

Magnetic equivalent circuit with permanent magnets

I am fighting to understand how permanent magnets are inserted in magnetic equivalent circuits. In the image below is an example, at the left, the physical representation of an Iron core with a ...
1
vote
1answer
37 views

How to determine the minimum proximity of magnet to an AC line for no electrical impedance?

As the title says, I am wanting to calculate the minimum proximity for a magnet to be near a AC line for no electrical impedance. My scenario is this: I have a theoretical device like MagSafe ...
0
votes
1answer
34 views

Mitigate the effects of magnetic induction heating in a three phase AC system

To mitigate the effects of magnetic induction heating in a three phase AC system, it is common practice to group the conductors and to keep them in the same raceway. Also, three phase power is ...
2
votes
1answer
164 views

Help building electric generator?

I am in the process of building an electric generator for the first time, and I have found out most of what I need to do, except the following things. Can I have 2 rows of magnets linked together ...
2
votes
2answers
287 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 ...
0
votes
1answer
43 views

Bit persistence on a Hard Disk Drive

I was wondering if there was a time limit to the "persistence" of bits on a hard drive, a classical SATA for example. If I'm correct, bits are written by a magnetizing head in some cells on the hard ...
0
votes
1answer
55 views

Magnetic flux outside a solenoid perpendicular to the direction of axis of solenoid

I know that using straight forward Biot-Svart law it is possible to calculate field inside a solenoid or at a point on an axis away from the circular coil. Now is it possible to calculate the Flux ...
4
votes
1answer
187 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
2answers
75 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 ...
1
vote
1answer
47 views

Would proximity to water affect a magnetometer

I'm using an InvenSense MPU9150 as a tilt-compensated compass in an autonomous sailboat. I'm trying to decide where to put the the control board, with options being in a dry box on top of the "deck," ...
1
vote
1answer
142 views

Can I increase inductance using permanent magnet ?

I know that when I insert a ferromagnetic core inside an air-cored coil, the inductance increases. What if I inserted a permanent magnet with a cylindrical shape into an air-cored coil, does the ...
1
vote
1answer
97 views

Why is the Litz Wire twisted?

I understand that dividing a wire into multiple insulated pieces reduce the Eddy Currents, and that reduces the magnetic field inside the wire, which leads to increased skin depth. But why do they ...
8
votes
2answers
857 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 ...
3
votes
2answers
431 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, ...
4
votes
1answer
307 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 ...
8
votes
3answers
2k 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). ...
1
vote
0answers
39 views

Is it necessary for EM fields to be dependent & co-exist in static conditions? [closed]

I was having a discussion today with one my colleagues in the lab about the independence and co-existence of EM fields. My argument: In time-varying fields: EM fields are necessary dependent, and ...
0
votes
3answers
112 views

How to select and use Strong Magnet together with hall sensor and amplifier?

With reference hall effect IC sensor (hopefully on topic as normal EE work) used together with these silver color magnet, as this example of 20 by 10 mm from ebay, Do they have different ...
1
vote
4answers
482 views

How do I determine the distance from a magnet using Magnetometer?

I have a triple-axis magnetometer and a magnet, and I am trying to calculate the relative position of the magnet from the magnetometer. The magnetometer outputs the strength of any fields detected in ...
2
votes
1answer
103 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 ...
3
votes
2answers
368 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 ...
0
votes
1answer
381 views

How to design a magnetic vibrator?

I plan to create a magnetic vibrator to shake a small container. What I plan is to buy Two "Magnet Wire 14 AWG Gauge Enameled Copper 1.5lb 118ft 200C Magnetic Coil Winding" a custom made container ...
2
votes
3answers
2k views

Which type of Ethernet magnetics should I choose for PoE?

I'm trying to find a suitable PoE MagJack for use with my Phy, KSZ8051MNL. The problem is that I can't find one with the same suggested magnetics topology. The closest one I can find has one extra ...
4
votes
3answers
150 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 ...
8
votes
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 ...
-1
votes
1answer
143 views

Magnetic shielding

http://www.kjmagnetics.com/blog.asp?p=shielding-materials I understand from the diagrams that the magnetic field is redirected through the shield (and not canceled out.. etc) Suppose I cover one ...
0
votes
2answers
210 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 ...
1
vote
2answers
217 views

How does the shape of the coil relate to the magnetic field around it?

I want to know if the shape of the coil affects the path of the magnetic fields around it. The two different shapes that I have are Helical coil and a spiral coil (in a plane).
8
votes
3answers
521 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 ...
0
votes
3answers
365 views

Electromagnet duty cycle

I have a project where I would like to use an electromagnet to lift an item for a longer period of time. I was looking at a magnet like this one: ...
-1
votes
1answer
259 views

How to implement a radial encoder with a diametrically magnetized magnet using a hall-effect sensor?

I want to implement a rotary encoder that doesn't use optical sensing or physical contacts. I found the following solution using a diametrically magnetized magnet on the shaft, and a dual axis hall ...
7
votes
5answers
2k 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 ...