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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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Finding the voltage across a inductor in a charged RLC-circuit

Well, I've the following circuit: simulate this circuit – Schematic created using CircuitLab In the circuit I want to find the voltage \$\text{V}_{\text{Y}_1}\left(t\right)\$ as a function ...
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2answers
55 views

Voltage spike at the coil when opening the switch [duplicate]

I've the following circuit: simulate this circuit – Schematic created using CircuitLab In my book they stated the following sentence: After that the switch is closed for a long time, I let ...
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1answer
43 views

Voltage exceed source voltage over a coil when opening a switch

Well, I have the following circuit: simulate this circuit – Schematic created using CircuitLab When the switch is closed for a long time, the current that is flowing trough the resistor \$R_1\$...
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0answers
33 views

inductor/coil - time to reach a given current

I understand that there's a simple forumla for calculating the time it takes for an inductor to reach 63.2% of it's maximum current: t = L/R But is there a way to calculate how long it would take to ...
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2answers
45 views

Removing a charged coil from circuit

I have a question: If I charge a capacitor through a resistor and remove it from the circuit, the capacitor will be charged for a certain amount of time (eventually the voltage across the capacitor ...
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0answers
42 views

Control a solenoid position “in / out” with power only (no spring)

I'm going to use a < 5$ solenoid (vertically oriented) that has to press something. If I understand well, a linear solenoid like this one: moves to one precise position when powered, but when you ...
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2answers
51 views

high voltage coil protection with epoxy resin [closed]

I have a high voltage cylinder coil with iron core. I want to protect it with epoxy resin. What is a good and easy way to do it for single use in a lab environment? What are the pitfalls?
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Coilgun - IR sensors interference

I´m working on my coilgun prototype, but I have troubles with IR sensors for projectile detection. When any of accelerating coils is switched off, all sensors report false detection. I´m using this ...
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2answers
47 views

Metal detection with a coil matrix

I have an 8 x 8 grid and would like to detect where on the grid I place a metal object. I'm currently working with the TDA0161 metal detection IC, and so far have the following setup with detection ...
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2answers
25 views

Resultant voltage function through two opposing coils with mutual inductance

So my question is about the type of relationship in a particular circuit. I would like to know if it is linear or something else like a power. The circuit in question is a pair of adjacent, mutually ...
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2answers
80 views

Magnetic Field Interfering with Radio Waves

i am currently building a device that requires a NRF24L01 module to send radio waves to another NRF24L01 to be picked up and interpreted. This is a using an arduino running a code to transmit data via ...
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48 views

Tesla coil circuit troubleshooting

Ok so we are making a tesla coil. Here is the circuit diagram we are referring: Now it worked when we first made this. The light bulb lights bulb when we bring it near to secondary coil. Then we ...
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1answer
101 views

Are my calculations wrong?

So I'm trying to make relatively a large square coil antenna that will operate at 125kHz frequency. The width and height of antenna are 300mm (30cm) and wire diameter is AWG24 (0.51mm) and I'd like ...
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1answer
61 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 ...
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1answer
44 views

Protection for transistor driving a coil

I recently purchased a few electromagnets. I want to drive these with transistors, but I want to build in protection, as these don't have any available specs re: max operating temp, duty cycle, etc. (...
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1answer
58 views

Magnetic Field around step-down converters [closed]

I'm courious how strong is magnetic field around step-down conveter? My plan is to use one LM2596 @ 12V(1A at maximum load) and one LM2596 @ 5V for STM32. I Know that coils generate MF around itself ...
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0answers
82 views

Detecting both short and open circuit voice coils in coil driver

I'm building a voice coil driver for a science experiment. The coils are in an environment where both coil shorts and coil open circuits are common problems. I'd like to build in a fault indicator to ...
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1answer
54 views

How to power an electric motor

I would like to attempt to assemble an outrunner BLDC motor from scratch. Its working principle seems ridiculously simple and I'm up for the challenge. There is one thing that I would like to clear up ...
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1answer
97 views

Magnetic circuit diagramming

What software makes magnetic circuit diagrams such as the one pictured?
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1answer
85 views

How does Rühmkorff induction coil start and periodically produce sparks?

I found the following pictures and equivalent circuit of the Rühmkorff induction coil: Can someone explain the operating of this coil in a step by step fashion?
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2answers
107 views

Power output of ignition coil - 2.0 [duplicate]

There was an older question about "Power output of ignition coil". The system would not let me comment on that question. So, I'll ask here. In regards to a ignition coil (non specific). OK,you have ...
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0answers
52 views

Linear antenna: with electromagnetic coil, trap circuit

I am trying to understand the concept of the linear antennas. I have read that the linear antennas are the simplest form of the antenna in the case of asymmetrical (coaxial) feed. what happens if I ...
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0answers
90 views

Designing a Flex PCB as a wireless charging coil

I am designing an inductive charging circuit to power up a small device with an odd shape. None of the off-the-shelf coils fit the dimension specified. I figured I needed to design my own coils like ...
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0answers
33 views

Current transformer damage

Can a current transformer be damaged with an open secondary coil even if it is powered with an extremely low current? e.g a small spark gap is made, though no plasma stream is created due to the ...
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1answer
85 views

Effect of a coil before DC motor

I am wondering what effect a coil before a DC motor has. It's a 3 AA battery powered (4.5V) small RC car. I cut off the cables going to the motor and connected the motor to the battery directly (I ...
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1answer
68 views

How to measure the impedance of a given coil? [duplicate]

What's the best way to measure the resistance and inductance of a coil at a given frequency? I need these parameters for my LTSpice-Simulation which assumes an RL series circuit. The coil has 8 ...
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1answer
69 views

Output problems with lm124 opamp

I am using this circuit to supply current through R1 which is a 50Ohm coil. Opamp is Lm124 supplied as shown in the schematic. Vin is a voltage that can be between 2.5V and 3.5V. Everything works fine ...
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1answer
38 views

Coil causing spike and circuit reset?

I built a circuit that pulses a 50-ohm electromagnet when a 'trigger' magnet passes over a hall-effect sensor. This circuit swings a pendulum and simultaneously plays an audio clip as long as the 555 ...
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1answer
62 views

Control a fan motor (with PWM IC burned out) [closed]

After the IC fan controller burned out by a voltage error I pulled it out to see what the motor coils were like. They are so I think: 4 series coils, but I'm not sure if it's the 4 coils in series. ...
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0answers
47 views

RLC circuit with intial conditions

The circuit I have is given by the following schematic: simulate this circuit – Schematic created using CircuitLab I know a few things: The current in the circuit at \$t=0\$ equals \$\text{I}...
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2answers
69 views

yesinductane heating stainless steel bolts [closed]

I wish to heat 303 stainless 10 mm bolt to form an eye with 10 mm ID. My gas torch just doesn't get the bolt hot enough for me to hammer it into the shape I need. So I would like to make an ...
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1answer
51 views

Relay Circuit Explanation

I am trying to understand relay circuits better. I have two circuits in question below. Left Image I understand Pins 2 and 9 are the coil contacts. I would wire a microcontroller outpin pin to a ...
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1answer
110 views

Does the lack of a primary DC blocking capacitor cause my tesla coil driver to explode?

Lately I've been tinkering with an SSTC half-bridge driver. I've ran a couple of tests using relatively low input voltages ~50V and the IGBTS seemed to do fine, there was no noticeable heating at all. ...
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2answers
60 views

Transformer windings order

I have several transformers for audio amps, with single thiner primary and dual larger area secondary windings, for lower voltage higher current. They are toroidal, all by different manufacturers, but ...
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3answers
146 views

Xenon Flash thyristor trigger

I'm building a xenon flash unit with a power of 50Ws (300V 1000uF capacitor). I need to trigger it from a microcontroller. For that I use a MOC3041 to opto isolate my µC from the HV circuit and ...
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1answer
52 views

Magnetize a thin cobalt steel rod

I need to magnetize a 1/16" x 4" cobalt steel ( drill) rod to its maximum strength. I plan to heat the rod past its curie temp before magnetizing for maximum effect. Can I do this with straight DC ( ...
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2answers
383 views

Mutual inductance vs coupling coefficient

Question regarding this and this question about mutual inductance and coupling coefficient. I'm trying to analyse a two coil system: It consists of two coils like in the picture with 2 cm air gap ...
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1answer
48 views

Transformer safety concern

I have a a transformer for my speaker (230VAC -> 9VAC). The primary of the transformer is basically a coil. Is it not dangerous to pull out the transformer from the outlet? I know that in coils if ...
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1answer
62 views

How Does Line Frequency Affect Coils of a Contactor?

I am using a generator as my source voltage, which produces 240VAC @ 240Hz. I was planning to use the following contactor from TE: CONTACTOR 4PST 40A 240V In the datasheet it says this contactor's ...
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0answers
92 views

How to know Number of turns

In closed magnetic circuit, How many turns are when a conductor winded around a square mild steel core with permeability (Ur=2410)? The outer length is 20 cm and inner length is 16 cm. The current ...
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1answer
189 views

Tesla coil - my primary circuit doesn't work

I would like to make a Tesla coil, so I bought a 10 kV 120 W 30 mA neon sign transformer from Aliexpress. First potential problem, while playing with it, I noticed that when it stops ...
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0answers
53 views

A few questions about copper coils, magnets and induction

So I've been into electronics and electricity in general, lately. I've been trying to understand induction. Here's a few questions I had pertaining to it. In what way are coils connected together to ...
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1answer
55 views

How to optimze a coil for needed voltage?

Faraday's law for a coil is : V = A * M * N Where: V = Peak output-voltage A = Area of the cross-section of the wire M = Rate of change of magnetic flux in the coil N = Number of turns of the ...
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3answers
112 views

Amplifying a pulsed current

I need to pulse a current through a coil, to create relatively short magnetic pulses. I would like to know if I can use a function generator as the source of the pulses and amplify the current that ...
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1answer
131 views

Overvoltage protection for AC relay dilemma

I am currently designing a safety-related device that has to open a relay when a certain event occurs. During most of its life, this relay will be closed, and only open if the safety event occurs, ...
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5answers
2k 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 ...
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1answer
56 views

“3 phase” Type of winding I am not aware of, help? not wye or delta, maybe eFed up generator?

I bought a few 30 watt 3 phase motor/generators in supposedly delta configuration from a ali express. the motor did have only 3 wires coming out, plus the manual stating it, I am pretty sure this was ...
0
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2answers
55 views

Why is the common lead of unipolar motor connected to the high level voltage?

I'm trying to gain a deeper understanding of DC stepper motor because I'm using them for an arduino project. I was wondering about why the common lead of unipolar stepper motors is usually (always?) ...
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0answers
64 views

Capacitors discharging into Coil

I have 2 capacitors charging in parallel and then switching them in series to discharge into a wound coil of known inductance. My capacitors are 4nF 2000V and the charging voltage is 1000V. So at the ...
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1answer
58 views

How does adding more coils to an AM tuner coil allow it to tune Shortwave?

I have seen several tutorials about how to turn an AM radio into a Shortwave radio. They add more coils to the inductor (is that the correct name for the tuning coil?). Here is one example, https://...