Questions tagged [coil]

A coil is an electrical conductor such as a wire in the shape of a coil, spiral or helix. coils are used in applications where electric currents interact with magnetic fields, in devices such as inductors, electromagnets, transformers, and sensor coils.

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47
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2answers
7k views

Why don't electrons take the shorter path in coils?

Below is a copper coil, presumably forming an electromagnet. From my understanding the electrons travel around the coil to produce a magnetic field. But why don't the electrons jump the wires and take ...
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4answers
57k views

How to properly wind coils for a solenoid?

I need to wind a small electromagnet "solenoid?". About 3cm high and 2~5cm wide running at 5V/0.5A. This magnet will be put into a desk bell so it pulls the clapper down and rings the bell. I have ...
13
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2answers
2k views

If I used the primary coil as an inductor, does the secondary coil affect it?

I've read this question. It's about how to obtain the maximum inductance from a transformer: How do I use a transformer as an inductor? Now, I would like to use the primary coil only as an inductor ...
11
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2answers
2k views

Why use aluminum wire in an (old) TV degaussing harness

I used to take TVs apart for fun (and parts, and learn.) Some of the degaussing coils were beautiful -- nice, thick copper. Others were made out of aluminum wire. If I were engineering it, though, I ...
11
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1answer
3k views

Why do I need to remove a part of the insulation on a copper wire on a simple electric motor?

Why do I need to remove a part of the insulation on one end of a copper wire in making a simple coil electric motor? How does removing only a part of the insulator makes the motor spin freely? ...
11
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1answer
13k views

Controlling an electromagnet strengh with arduino

This previous question Controlling an electromagnet with Arduino deals with binary control (ON or OFF) only. On my side I need to choose the strength of the magnetic field. It is a home made ...
10
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5answers
3k views

H-Bridge with emitter followers

I am currently reverse engineering a circuit which requires controlling of a magnetic field. For that, the circuit has a pair of D882 and B772 each. The PCB traces suggest that the transistors are ...
10
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5answers
75k views

What are the differences between an AC and DC coil relay?

If a DC coil was just a coil, it would saturate. If an AC coil was just a coil, the magnetic field would drop to zero at 120 Hz and the relay would chatter. Presumably the designs in some way prevent ...
8
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5answers
7k views

What do you call a relay that self-opens on power loss?

I'm programming the simulation of some circuitry. These are relays that will open automatically when they lose power: Do relays such as this have a particular name? "power hold relay"? "single ...
8
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6answers
10k views

Can the wire of a high voltage power line be used as the primary coil of an air cored transformer? [duplicate]

Back in the 90's I heard this story of a guy who in the 70-80's lived remotely near the power lines and that he was very good in electrical engineering and that he had free electricity by using the ...
8
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1answer
3k views

Making a nail electromagnet with bare copper wire?

When creating a simple electromagnet, all you need is a nail and some copper wire, and a battery. I did this using non-coated copper wire, and after thinking about it for a bit, I was confused as to ...
8
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4answers
1k views

How to identify an ordinary coil? Can I use some tools do identify its value?

I did a big mistake and damage an electronic coil in my PCB. The only information I did have is the coil itself! There are two identical coil in it. This is my PCB. It is the UCD-210M. This is the ...
7
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2answers
561 views

Measuring faint varying magnetic fields with a coil

Disclaimer: I’m computer scientist. I want to measure a faint varying magnetic field with a coil. The frequency domain I’m interested in is ultra low (< 10kHz). The source of the varying magnetic ...
7
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2answers
2k views

How to measure coils without inductance measuring device?

I have a multimeter that can measure capacitance, resistancr, voltage and current. If I have a known coil and unknown coil, can I measure the ratio between the inductance of the two coils? Is it ...
7
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1answer
228 views

How susceptive is an inductor to frequency and current?

According to Coilcraft - Testing Inductors at Application Frequencies the inductance of a coil changes with frequency and current. Most datasheets don't give a frequency-inductance plot and current-...
6
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2answers
10k views

Reduce noise from a Hall effect sensor

I am currently working on a magnetic levitation project using a Hall effect sensor for distance measurement. I drive the coil using two 12 V car batteries in series to form a 24 V DC source, ...
6
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2answers
1k views

How to compare a magnetic loop antenna to a conventional antenna

I want to build a compact 1 MHz receive coil (antenna for very near field). For that I need to make a choice on whether to build a simple RF coil only consisting of wire and capacitors or using a coil ...
6
votes
1answer
719 views

Why my two coils don't repel each other?

I'm experimenting with two coils. I drive them with two MOSFETs and one consumes around 1A and the second ~0.7A (12V power supply able to deliver 15A). While the coils work with permanent magnets and ...
6
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2answers
966 views

UHF Tesla coil powered by low voltage?

I want to know if it is possible to use a 2.4 GHz magnetron as a oscillator for a Tesla coil circuit. The idea is to use a oscillating relay-driven step up transformer (12 V to 10 kV) and then charge ...
6
votes
1answer
6k views

increasing metal detector range

I am working on my senior project. As part of my project I need to use a metal detector. I am using the following circuit schematic. The principle is based on the properties of inductor coil: $$L=N^...
5
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3answers
3k views

Need to create a magnetic coil (no core) for low frequency field (20Hz-100Hz)

I am doing some experiments with pulsed magnetic fields. I am using an audio amplifier as a power source, and a simple software as my frequency generator. I use mostly square waves and sometimes sine. ...
5
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5answers
5k views

Can a Tesla coil's secondary wiring overlap?

I am building a small tesla coil just as a proof-of-concept using a bug-zapper circuit. I unwound some enamel copper wire off a transformer and put it on my 12 cm length x 2 cm diameter PVC pipe and ...
5
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3answers
12k views

Relay inrush current consumption

I am asking what happens, from the power/current consumption point of view, when I energize a relay. In theory as relays are coils and like to hold current there shouldn't be a current spike when I ...
5
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3answers
14k views

How to build a self-made Qi compatible (wireless) charger

So I recently discovered that my phone, a Nexus 5, has Qi wireless charging capabilities. I was wondering if it is possible to make my own charging coil with 24/26awg wire that would look something ...
5
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1answer
963 views

Any simple short range metal detector?

I'm looking for a simple short range metal detector. I've looked everywhere and I can find only complex metal detectors circuits to find metal at several cms of distance, most over 60cm, they are an ...
5
votes
1answer
383 views

How to choose the right frequency when measuring coil inductance with LCR meter

I would like to drive a 12V DC hydraulic valve coil using a high side driver (VN7140AJ). The driver datasheet specifies the maximum demagnetization energy (page 24), and I would like to make sure that ...
5
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2answers
3k views

Induction heater circuit problem

I am trying to build induction heater with the help of the following schematics(taken from this page): So I am using 220:10Vrms(15Vpeak) transformer with fullbridge rectifier and a capacitor to get ...
5
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1answer
2k views

How to measure self resonance frequency of coil using CRO?

I have antenna coil for tuning an antenna. I want to measure self resonant frequency of the antenna coil. Can anyone tell me how to measure it with an oscilloscope? What will be the experimental ...
5
votes
2answers
213 views

What makes conical coils that good in microwave circuits?

Conical coils are often used in microwave technology. Can someone explain what makes this shape so unique? How does this shape affect parasitic capacitances? Some conical coil photos: This is NOT ...
5
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2answers
619 views

Another 'What is this component?' question

I have looked through all the other 'what is this component' questions and have not found my component. I am looking for the component in the red box. It is from a rectifier circuit off a 1973 9.8 hp ...
4
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5answers
194 views

Relay coil fast demagnetisation

In the past few days, I've encountered an application note on the Maxim Integrated website about rapid demagnetisation of an inductive load: https://www.maximintegrated.com/en/design/technical-...
4
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3answers
6k views

Does a dashed line mean "when energized"?

I'm having a hard time understanding this circuit diagram: I'm interested in the following component sates, and how they affect power distribution: the breakers: the buses: the AVIO MSTR ...
4
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2answers
760 views

Are there 2D-Transformers?

I need to create a PCB with a transformer on it, and in this case, I unfortunately can't solder on a regular one. I was wondering if there was anything akin to a 2d transformer, or just generally a ...
4
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4answers
2k views

Measured Q factor of LC circuit does not correspond with calculated and simulated

Still having a problem with measured value of Q factor of parallel LC circuit. My measurememt setup looks like on the picture below. I use Function generator SFG-1003 and Oscilloscope Rohde-Schwarz ...
4
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4answers
5k views

Make an electromagnet attract and repel

I bought an electromagnet online hoping to make it attract and repel metals by changing the polarity of the voltage on it, but I ended up experiencing attraction all the time. Is there any way to ...
4
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2answers
9k views

Why wrap wires around a magnetic donut on a wiring loom?

Can anyone tell me why you would wrap wires around a magnetic donut on a wiring loom? There are 3 wires running on the loom, they run from a power source to the stator of a direct drive washing ...
4
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4answers
1k views

Accurately measure high quality factor coils

What would be the most suitable way to measure the quality factor of high-Q coils under the following conditions? Specifications Frequency: 5 MHz to 15 MHz, the target application is wireless ...
4
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3answers
1k views

Rotating a wireless power mechanism

I got this simple wireless power mechanism: http://dx.com/p/diy-wireless-charging-transmitter-receiver-solution-module-green-golden-dc-5-12v-194469 If I'll have the receiver end rotating at about 30 ...
4
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2answers
1k 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
420 views

What are these coil components with three legs?

A couple of weeks ago I dissassembled a Panasonic DVD-recorder and salvage some components including these little guys. I tried to figure out what these are but cannot find a datasheet by searching ...
4
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3answers
2k views

How can we measure the voltage at the coil of a Slayer Exciter?

How can we measure the voltage at the coil of a Slayer Exciter? We have built a simple 9V Slayer Exciter for a school project. We are examining the conservation of energy at the transformer. The ...
4
votes
1answer
102 views

What will be the behaviour of superconductors if they are used as core or coil?

Superconductors are strong diamagnetic in nature so if they are used as core of any coil do magnetic lines of forces pass through them – I mean inside them just as with a soft iron core? Secondly if ...
4
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2answers
3k views

How does the Accutron Spaceview work?

I am wondering how the electronic circuit used to drive the tuning fork in the Accutron Spaceview watches worked. The page at The Accutron 214 gives a brief explanation and some diagrams. I am most ...
4
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1answer
204 views

can I use a choke 150uH inductor for my AM transmitter circuit?

I am trying to develop an AM transmitter but I am having problems with getting a variable capacitor and inductor (for the rf circuit) in my location. I was able to find a choke coil with an inductance ...
4
votes
1answer
151 views

optimal low pass by trial and error?

After opening an old webcam I found a lens with a magnetic socket, which is used for autofocus. A coil moves the lens in and out to adjust sharpness. I recently mounted that feature onto the ...
4
votes
1answer
2k 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
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5answers
22k 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
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3answers
424 views

How to optimise wire gauge selection for electromagnetic applications?

Disclaimer: Hobbyist "maker" with limited experience and no relevant education. Please considerate and answer in detail. Feel free to skip to "Question". Context I have an ...
3
votes
4answers
3k views

Can I use a supercapacitor (like Maxwell boostCAP 3000F) on a coilgun?

Can someone tell me if I can use a supercapacitor (like Maxwell boostCAP 3000F) on a coilgun? I want to obtain a very intense magnetic field for a project, and I'm not sure what capacitors should I ...
3
votes
3answers
72 views

Induction Motor Wire Size

Capacitor Run Single Phase Induction Motor have very high starting currents, possibly in the order of 35-40 Amps upon startup for a 1 hp device, whereas the nominal current usually lies in the order ...

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