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-   -   How to make my own inductors? (http://www.diyaudio.com/forums/everything-else/4885-own-inductors.html)

 hugobross 29th July 2002 11:17 AM

How to make my own inductors?

Hi all,

can anyone tell me how I can simply make my own inductors to place in series with the load of a dimmer?

*)how many turns?
*)is a metal "?kernel?" needed? (I don't know if this is the right word)

thanks,

HB.

 Gabevee 29th July 2002 01:10 PM

Hi hugobross,

There are two types of inductors one can have: Air core and Iron (or some other metal) core.

Air core inductors offer the user a lower chance of saturation. The price one pays is one needs to make them larger and with many more turns.

Iron core OTOH allows one to make efficient smaller inductors. But they can saturate, or reach a peak, sooner.

Now, the kind of inductor you need depends on the application. You can make single layer coils, or multilayer coils. The following equation (and there is another that many will quote. This one I got from a book I have from the 70's) is for a single layer coil:

L=N^2Aµµ0/l

Where:

L = inductance

N = number of turns

A = cross sectional area of coil form (inner diameter)

µ = permeability of core (air = 1, iron = 1000-5000)

µ0 = absolute permeability (1.26 x 10^-8)

l = length of coil

Rework it to find out how many turns for a single layer coil, knowing the dimensions (length, cross sectional area, air or iron) and one comes up with this (SqRt = Square Root):

N= SqRt (Ll/Aµµ0)

I had reworked the equation to work for me for multilayer coils, AKA pi windings. I surmised that it was called pi winding because when I did my experiment to figure out an equation for it, Pi was part of the factor. The following are for air and iron cores respectively:

N= (SqRt (Ll/Aµµ0)) / (Pi/2) (for air core)

N= SqRt (Ll/Aµµ0) * (1000*Pi) (for iron core)

As things go, these equations aren't perfect, and one would need an inductance meter to add or remove windings to get exact inductances. But this gets you very close. I know, because when I needed to rebuild an oscillator coil for an antique radio, it brought me to within two turns of exact inductance.

Hope this helps. It would help you to also read up on what inductors do and how they do what they do before going any furhter.

Gabe

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