Every hobbyist wanting to dabble in radio has to — at some point — wind a coil or two, be it the antenna coil of an AM radio, a coil on a toroidal core for a bandpass filter in a communications transceiver or a centrally tapped coil for use in a hartley oscillator. Winding coils is not hard but quite time-consuming. There are different methods of making coils, depending on the area of use and inductance needed.
Air cores are the most broadband but getting high inductances means using a lot of wire, they are also not the most efficient do to the magnetic field escaping the coil — this escaping magnetic can cause interference by inducting in nearby wires and other coils. Winding a coil, over a ferromagnetic coil focuses the magnetic field, increasing the inductance. Different commonly used materials have different relative permeabilities, ranging from for electrical steel used in mains transformers, through around for ferrites used in SMPS transformers and around 20 for iron powder cores used at VHF.
Each core material should only be used inside of the specified frequency range, outside of which core starts exhibiting high losses. Toroidal, multi-aperture cores, pot, and other enclosed cores enclose the magnetic field inside the core, increasing efficiency and practically reducing interference to zero.
To learn more about inductors and its working follow the link. Air cored coils are good for low inductance coils, where interference is not of utmost importance. Coils with a small amount of turns and relatively thick wire are wound over a cylindrical object such as a drill bit or canwhich is then removed and the coil supports itself, sometimes the coil is coated in resin for higher mechanical stability.
Bigger coils with a lot of turns are commonly wound over a non-ferromagnetic former, such as a hollow plastic tube or a ceramic former for high power RF coils and then secured to the former with glue.
To wind them you first need to calculate the required wire diameter, because it has a lot of influence over total coil length. If the coils are used at low power levels the wire diameter is of not so high importance, 0. If the coil is used in oscillator service the wire should be stiff, to prevent warping effects as they can change the inductance to some extent and cause frequency instability driving.
Next, you need to know what diameter the coil needs to have. If the coil will be self-supporting you can use a bolt or a screw, wind the turns inside the grooves and remove the bolt by unscrewing it while holding the wire of the coil, this makes a very even and reproducible coil.
This formula is used when winding a one-layer uniform coil with all turns being closely wound with no space between them. The units are the same as with the above formula, except d which is coil diameter in meters.
Design A Coil For A Specific Inductance
A very good calculator for coil has been made by Serge Y. To wind a regular air-cored coil you need a former, a source of wire, some fine sandpaper or a modeling knife not shown and a bit of superglue or double-sided tape to hold the wire in place.
After designing the coil it is time to wind it. Next, cut a strip of double-sided tape with the length of the coil and stick it to the former, then drill holes in the former where the coil ends and at taps, take off the cover layer on the tape and start winding, first by passing it through the hole you drilled then winding it, as usual, the wire will be held by the double-sided tape, alternatively, you can glue the begging of the coil to the former after winding a few turns with cyanoacrylate glue, wind the rest of the coil and glue every 1cm also called super glue, use gloves, it is very hard to remove from skin and causes irritation.
For taps, twist a length of the wire together, pass it through the hole in the former and continue as usual. Try to wind the turns close, after winding strip the enamel off using fine sandpaper or a modeling knife and tin the ends with a soldering iron.
Step 1: Below two pictures show the Former with a bit of tape where the wire will be wound and Holes to hold the wire in place. Step 3: Then put through a hole in the former and out the other side. Step 4: The finished coil has its wires tinned by submerging them in solder on a piece of PCB laminate.
Step 5: Finally the coil inductance is measured using an LCR meter. You can use super glue to hold the wire in place instead of double-sided.For introduce and more initial info of this cores we making a video that you can watch it from here:.
In the next we're start the designing. At the first we must know the diameter of our core. Each core have 3 diameter and it's really important in designing. So watch our next video to find out how you can measure them:. Now its designing time Toroid inductor design by using online sites. OK by watching 3 previous video you know how to design and calculate your toroid inductor, but can you tel me how you can do wiring them? By makesomethingsmarter Follow. More by the author:.
About: I and my cosine decided to making YouTube channel for making electronic project, programming, learning software, DIY, examine something new and this kind of stuff.
Hello and welcome to Toroid inductor making room!! For introduce and more initial info of this cores we making a video that you can watch it from here: introduce the Toroids In the next we're start the designing. So watch our next video to find out how you can measure them: measureing toroid diameters Now its designing time Toroid inductor design by using online sites OK by watching 3 previous video you know how to design and calculate your toroid inductor, but can you tel me how you can do wiring them?
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The following design guide may also be downloaded as a PDF. For other inquiries regarding inductor design with Magnetics ferrite cores, Contact our Applications Engineers or submit a Custom Inductor Design request. Ferrite E cores and pot cores offer the advantages of decreased cost and low core losses at high frequencies. For switching regulators, power materials are recommended because of their temperature and DC bias characteristics.
By adding air gaps to these ferrite shapes, the cores can be used efficiently while avoiding saturation. These core selection procedures simplify the design of inductors for switching regulator applications. Follow this coordinate in the intersection with the first core size curve.
Read the maximum nominal inductance, A Lon the Y-axis.
Inductor Design with Magnetics Ferrite Cores
Required inductance L, core size, and core nominal inductance A L are known. Calculate the number of turns using. There are many ferrite cores available that will support the energy required. The above curves represent the locus of points up to which effective permeability remains constant. They show the maximum allowable DC bias, in ampere-turns, without a reduction in inductance. Beyond this level, inductance drops rapidly. Example: How many ampere-turns can be supported by an 0RA pot core without a reduction in inductance value?
It is used for its properties of high magnetic permeability coupled with low electrical conductivity which helps prevent eddy currents.
Because of their comparatively low losses at high frequencies, they are extensively used in the cores of RF transformers and inductors in applications such as switched-mode power suppliesand ferrite loopstick antennas for AM radio receivers. Ferrites are ceramic compounds of the transition metals with oxygenwhich are ferrimagnetic but nonconductive.
They have a low coercivity and are called " soft ferrites " to distinguish them from " hard ferrites ", which have a high coercivity and are used to make ferrite magnets. The low coercivity means the material's magnetization can easily reverse direction with dissipating very less energy hysteresis losseswhile the material's high resistivity prevents eddy currents in the core, another source of energy loss.
The most common soft ferrites are:. As any given blend has a trade off of maximum usable frequency, versus a higher mu value, within each of these sub-groups manufacturers produce a wide range materials for different applications blended to give either a high initial low frequency inductance, or lower inductance and higher maximum frequency, or for interference suppression ferrites, a very wide frequency range, but often with a very high loss factor low Q.
There are two broad applications for ferrite cores which differ in size and frequency of operation: signal transformers, which are of small size and higher frequencies, and power transformers, which are of large size and lower frequencies.
Cores can also be classified by shape, such as toroidal cores, shell cores or cylindrical cores. Ferrite rod aerials or antennas are a type of small magnetic loop SML antenna   very common in AM radio broadcast band transistor radiosalthough they began to be used in vacuum tube "valve" radios in the s. They are also useful in very low frequency VLF receivers,  and can sometimes give good results over most of the shortwave frequencies assuming a suitable ferrite is used.
They consist of a coil of wire wound around a ferrite rod core usually several inches longer than the coil, but sometimes over 3 feet long . Other names include loopstick antennaferrodand ferrite-rod antenna. From Wikipedia, the free encyclopedia. This article is about transformer cores. For the computer memory technology, see Ferrite core memory.
Electronic components. Potentiometer digital Variable capacitor Varicap. Capacitor types Ceramic resonator Crystal oscillator Inductor Parametron Relay reed relay mercury relay. Authority control GND : Categories : Electromagnetic components. Namespaces Article Talk. Views Read Edit View history. Help Learn to edit Community portal Recent changes Upload file.
Download as PDF Printable version. Wikimedia Commons. Wikimedia Commons has media related to Ferrite cores. GND : There are many different articles and videos to be found online that will teach you how to build a Joule Thief circuit and power LEDs off of dead batteries. Most of them, however, call for some form of coil made using a ring, or toroid, made of ferrite. This can be rather daunting to newcomers to electronics, as "ferrite toroid" sounds rather impressive and exotic at first.
The truth is that a ferrite toroid coil is just a simple coil with two windings wrapped around a ring made of ferrite iron. Toroids are often used because the ring shape is very effective at storing electromagnetic energy, but you don't actually need a toroid to make a Joule Thief. A simple coil with two windings around a central core will work just fine. Note: If you have any common sense, you will likely not get hurt in the making or usage of this project.
If you do, however, it is you own fault and I accept no responsibility for any harm incurring as a result of your attempt at this project.
The image on the Intro step is not mine. It comes from this video herewhich provides a good tutorial on how to make a basic Joule Thief. A magnetic core. Anything that will stick strongly to a magnet will work.
Make a Joule Thief Coil Without a Ferrite Toroid
I used a hacksaw to cut the end off of an old drill bit, but a bit of a nail or other iron object will work. You might try the piston from an old sprinkler valve solenoid. Try and make it about a centimeter long, cutting it if you have to obviously, be careful. Two buttons. I took these off of a dress shirt. You could also use some little discs or squares of plastic or even carboard if you want. These will serve as endstops to keep the wire wrapped tightly around the core.
You might also want to use a bit of adhesive to secure the wire on the coil after you finish winding it.This is obviously a great skill to learn as sometimes your design may call for a very accurate inductance that may be otherwise hard to find. Making your own inductor may seem daunting. He also provides all the formulae needed to calculate the inductance in the video below. Changing the inductance with a wiper changes the frequency of the radio: this is a variable inductor.
This video is great for understanding the foundations of inductors. Good article. No worries, Jack. Hard to keep track of them all. Not bad, but it is a definitely a simplified design calculator.
When using ferrous cores, the relative permeability of the core is non linearly dependent on the materials permeability and the length to diameter ratio of the core.
Also left out is the distributed capacitance of the windings which will dictate the resonant frequency of the coil. This in important because it limits the frequency range you can tune in. Some crystal radios tune by sliding a ferrite core into the coil. The coil has a high voltage across its length and the conductive content in the core would be shorting it out — or maybe not if the core is made of isolated conductive particles.
Cheapo ones normally use PVC and it works great. Your right about breakdown to the core being a problem if you used a ferrite core in a tesla coil. Tesla coils are RF transformers and thus a bit different from regular transformers.ferrite bead on sparkplug wire
This site uses Akismet to reduce spam. Learn how your comment data is processed. By using our website and services, you expressly agree to the placement of our performance, functionality and advertising cookies. Learn more. Changing the inductance with a wiper changes the frequency of the radio: this is a variable inductorThis video is great for understanding the foundations of inductors. How Smart Is The Grid? Report comment. Inductors are notoriously hard to get right.
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