Questions tagged [magnetics]

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

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54 views

I thought magnets could affect the operation of chips, but I’m seeing apple use them increasing more in their products, am I wrong in my thinking?

I’m a bit confused because I used to use magnets to fix the TV monitor when it had faults in the image, but it wasn’t good to use it that much, but Apple is using magnets in their products such as ...
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105 views

Two-core transformer with three windings?

I am trying to understand how a transformer composed as pictured would function. Basically, two separate cores. Both cores go through the secondary winding. But only one of the cores goes through the ...
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1answer
33 views

Interpretation of the graph of excitation current for magnetic circuit

(From Electric Machinery, Fitzgerald) Why does the current waveform here have such a sharp peak like that?
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36 views

Discrete vs Integrated Magnetics

I am working on a design based on the TI TM4C1294 micro-controller. This is the first project that I have needed to implement an Ethernet interface on. I have been reading the system design ...
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115 views

How to design an inductor which consists of four separate windings in the same core?

I need to design an inductor such that there will be four separate windings at the input side (each input is coming from a different DC-DC converter) then these four windings are combined at the ...
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43 views

Calculating A Transformer Core Power Capability

I'm trying to build a transformer for a full bridge dc-dc converter and it's my very first time to design a transformer and I got limited knowledge. I'm checking some ferrite cores and I've found ...
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108 views

Is there a color standard for painted toroidal magnetic cores?

Is there a color standard for painted toroidal magnetic cores ? I noticed that yellow-white usually means a powdered iron core with a relative permeability of around 100 at frequencies below 10kHz. ...
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1answer
36 views

POE power pass through

Is it possible to connect the center taps of two Ethernet magnetics to each other back-to-back to pass the power from one port to another. Does it make sense? Is anything special required?
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316 views

Why are the poles of the stator and rotor taken differently in the picture below?

The rotor and stator in the picture below have the same orientation of flux lines yet the are taken as opposite that is flux lines leaving the stator is taken as a South Pole while flux lines leaving ...
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49 views

Calculation of magnetic field saturation inside coil core

I want to try to make an electromagnet, but I don't have soft-iron available. I've read that ferrite MnZn are suitable as soft-iron to create a high efficiency magnets with the inconvenient of lower ...
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76 views

Tesla Coil not working

I made a simple miniature Tesla Coil following a youtube tutorial (https://youtu.be/AehL3BodduE) As you can see in the photos, I 3-D printed a PVC pipe like piece and wound two copper wires one over ...
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50 views

Magnetic locks with paramagnetic materials

Well I was wondering why magnetic locks are made of an electromagnet and a ferromagnetic material and not an electromagnet and a paramagnetic material. The magnetic attraction between the ...
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41 views

induced voltage in coil due to moving magnet

I am trying to calculate the voltage induced in a zylidric coil by a moving permanent magnet that is placed near the coil. To simplify calculations, assume that the permanent magnet is also a zylinder ...
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1answer
31 views

Will using magnetic base test indicators with breadboards cause electrical interference?

The situation leading to the question In the Quick Tips #8 // Precision Helping Hands YouTube Video, a "helping hands" with various names such as "Magnetic Base Adjustable Metal Test Indicator Holder"...
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30 views

Magnetometer moving along a line with different measurement?

I am testing on a magnetometer and found that moving the magnetometer along a straight line within the range around 1m, and the measurement varies. From what I understand, moving magnetometer along a ...
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Why do most flyback converters / LED drivers operate under 100 kHz?

Most of the LED drivers and flyback converters I have come across operate in the 60-100 kHz range. Is there any particular reason behind this - example - ferrite cores not being able to handle higher ...
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39 views

How do I determine what magnet to use at a specific distance for a reed switch?

I have a reed switch that shows a 10AT to 15AT operate range on the data sheet. I need to determine if specific magnets will fire the switch, and at what distance. The magnets I'm looking at though, ...
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33 views

Is it possible to influence the working behaviour of a simple dc motor with an outside electromagnet?

I am using a simple DC-Motor 9V like this one. Now, I am curious about what influence an outside magnet / magnetic field would have on the working behavior of this motor? I would like to use the ...
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46 views

HR911105A or similar integrated magnetics for POE

Is it ok to use this RJ-45 socket for low power POE application (just to power the uC)? The only available datasheet : https://www.google.com/url?sa=t&source=web&rct=j&url=http://www....
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42 views

Magnetic Linear Positioning with no magnetic disturbances at all

I recently saw a machine where it used a hall sensor or a magnetometer for linear positioning (the sensor is wrapped in some opaque protection so I don't know what it actually is which is the real ...
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56 views

What to do with unused Ethernet magnetic center taps on POE?

I'm using a MAGJACK GIG PDJACK 1X1 CLASS 4 (Molex # 0857914020 - Link: https://www.digikey.com/products/en?keywords=WM9656-ND) to run POE on a 100MBit network connection. I thought this was a nice ...
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1answer
108 views

Compass-Needle steering PCB

I'm trying to think of the easiest/best way to steer a compass needle using a PCB. Specifically, placing a PCB of some kind under a compass (assume no shielding between the PCB and the compass) and ...
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210 views

How critical is the magnetics circuit diagram in a magjack RJ45?

I'm looking at an example circuit diagram from ST, and it use sa 48F-01GYDXNL part that I can't find anywhere. It's a gigabit ethernet jack with magnetics, and the datasheet shows a circuit looking ...
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1answer
229 views

Can I swap TX+ and TX- (and RX+ and RX- ) using ethernet magnetics?

I am building ethernet connectors and a switch into a product. There is a requirement to include PoE which I haven't done before. This has required the use of a new magnetics chip to expose the two ...
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1answer
48 views

measuring ac voltage drop across a resistor with a solenoid in series with it

I wanted to measure the phase difference between the current (magnetic field due to the solenoid) and the system response. I am doing this by measuring the voltage drop across the resistor in series ...
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1answer
79 views

10/100Mbps Magnetics with 10/100/1000 PHY

I have a SOC that has a KSZ9031RN PHY, that is a Gigabit PHY. But I'm going to use only in 10/100 Mode with 4 wires. Gigabit PHY datasheet recommends a magnetic for Gigabit Ethernet, that are ...
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1answer
94 views

Possible to have too much magnetics in Ethernet

I have a question regarding magnetics topology on an ethernet 1000base t channel. I'm working on a project where I have a board (board 1) with MAC, PHY, and magnetics. I have another board that mates ...
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67 views

Charging a capacitor with a ferromagnetic generator

I am doing my internship and the company is making a ferromagnetic generator which indeed uses magnetic transition to create a flux and finally EMF. I am assigned to design a circuit which takes the ...
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36 views

High speed switching electromagnet control circuit

I am not very familiar with high speed switching magnets, and need help finding a control circuit that has adjustable frequency and duration for High Rate Switching Electromagnets, with a digital ...
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1answer
46 views

Increase emf received from a coil without changing flux source

I have a situation where I'm trying to increase the amount of power received by a coil. To my understanding, I can increase the emf (voltage) by doing one of 4 things: Increase the number of coils (\$...
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56 views

What defines the maximum primary current of a (sensor-only) current transformer?

Take the Coilcraft CS1200L for example, which states the sensed current maximum is 35 A. This limit doesn't seem to be defined by the wire size which can fit through the hole (5 mm) as you can pass > ...
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172 views

Stacking M.O.T. to create an E-E core

I just came across this site looking for answers on some questions I have concerning microwave oven transformers (M.O.T.). I am currently going into my third year as an E.E. student and I am trying to ...
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Question about Biot Savart Law using vectors

This is a Biot savart law question using vectors and I tried this question and I want to check my answer is correct or not. And please show me the correct answer if wrong. I uploaded my Answer. ...
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1answer
55 views

Sending flyback current to another inductor using crossed diodes

So, here is the context. We have two electromagnets (modeled as R1 and L1, and R2 and L2), their state is dictated by a microcontroller which sends PWM to Q1 and Q2. The signal sent to Q1 and Q2 is a ...
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170 views

Bob Smith termination for Ethernet magnetics

I know that Bob Smith termination is recommended for Ethernet differential pairs. Please refer the below image for Bob Smith termination resistor placement. As far as I know, Bob Smith terminations ...
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122 views

Why is the the permeability of a ferromagnetic material given as B/H not it's slope dB/dH?

I was going through my Electromagentics book by Sadiku where it was mentioned as a point that permeability of ferromagnetic material is given by the ratio of B(magnetic flux density) to H(magnetic ...
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1answer
208 views

Should Ethernet MDI Pairs all be Length Matched (Inter-Pair) before going into magnetics?

I've been trying to find information for the above question and I can't seem to find anything. I have 1000 BASE-T lines coming from an Ethernet cable to a PCB mounted connector. I'm pretty much ...
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43 views

Are magnetically tunable surface acoustic wave devices commercially produced?

I have been reading up on studies of magnetically tunable surface acoustic wave devices, in general they note the relative velocity change or in some cases a frequency shift if it is part of an ...
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1answer
56 views

GbE Phy(88E1543) with POE+ PSE(LTC4266) design (POE+ magnetics? RJ45 with Integrated magnetics?)

I'm trying to understand how i can inject power to a 4 bank RJ45. I want to use these parts : - LTC 4266 4 ports PSE (802.3 at compliant for GbE, in type1 class3 for 13W at each port) - Marvell ...
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196 views

How can an induction motor be “self starting”

I read that all you need to start an induction motor is to apply the AC voltage, and with time the slippage decreases. How does this happen magnetically? If a rotor, connected to a moderate sized ...
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1answer
29 views

Field geometry of external magnetic core?

If there is a coil with an external core, would the polarization of the magnetic field inside it be the opposite of an internal core? For example, in the image: If DC current were applied to the ...
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1answer
65 views

At what frequency is a transformers rated impedance measured

Where transformers have a specific impedance rating for the the primary/secondary, what frequency is this measured at? For example, this transformer is rated at 40MHz - 860MHz with an impedance of 50/...
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173 views

Wireless Electricity Transmission model not working. Why?

I made wireless electricity transmission model using the principle of magnetic inductive coupling to transfer electricity between two separate coils. The model is very simple, known to everyone and ...
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145 views

Electrical model of a transformer

I would like to know what is the inductance (circled in red) of this part of this model? Is the value infinite? And only the inductance (circled in blue) is the value of the inductance of the ...
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58 views

Tuning antennas

I am working in a biomedical implant. I have to design an antenna for the wireless power transmission. The frequency that I am using is 13.56 MHz. I used some antennas found in some articles but when ...
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83 views

Can an inductor lose its characteristics permanently after short saturation?

I was testing a SMPS (boost) where I had an overcurrent due to overload for a few seconds. The inductor saturation current is 2A. Although I could not measure the current, I am quite sure that the ...
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38 views

Is there risk to using magnets on an enclosure that would have 1-2A wire assemblies leaving the enclosure

Would there be a reasonable risk to using magnets to close a large enclosure panel which has 3 motor drivers with wire assemblies that leave the enclosure to drive stepper motors? The motor drivers ...
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25 views

Confusion regarding the right hand thumb rule

I am confused regarding the use of the right hand thumb rule . There is two use cases for this rule : 1- The first when the thumb points in the direction of the current the fingers points in the ...
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1answer
64 views

Shape of a core for use in a solenoid

I am currently designing an electromagnetic accelerator meant to accelerate a spherical nickel-plated NdFeB (neodymium) projectile along a circular tube, in a similar manner to a particle accelerator. ...
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1answer
85 views

Detrimental impact of magnetic field on PCB and battery?

We are developing a small consumer electronics product consisting of a small 4-layer PCB along with a few PDM microphones and BLE chip/ an antenna, as well as a LiPo battery. We are locating a small ...

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