I need to make a coil (250uH) with a primary of 17 turns of 26g. wire and a secondary with 102 turns of 26g. but only have a spool of 28g. wire. Can anyone explain to me how to convert this to use the 28g wire as I do not have a table or equation in my books to do so?

: I need to make a coil (250uH) with a primary of 17 turns of 26g. wire and a secondary with 102 turns of 26g. but only have a spool of 28g. wire. Can anyone explain to me how to convert this to use the 28g wire as I do not have a table or equation in my books to do so?
Go get yerself a Pocket Ref by t. glover.
A single layer coil can be determined by I=(R*R(N*N))/
9R+10L where R is the Radius of the coil and L is the length this works to about 1-2% in microhenries your wire 28g gets about 72turns per 1inch square of the above formula but who cares? just figure out the distance and the radius and start a winding.

The gauge of the wire determines the powerer carrying capacity of the coil, so it would be better to use a gauge that is heavier like #24g if space permits. Otherwise, the formula is the same, but the lighter wire will cause the coil to have higher losses and lower "Q" (quality factor). Assuming that you are in the United States, just go to Radio Shack and buy pack of magnet wire. Each pack has three small spools of different sizes, one of them being 26g, the others are heavier. I hope that helps you. Bart

:I need to make a coil (250uH) with a primary of 17 turns of 26g. wire and a secondary with 102 turns of 26g. but only have a spool of 28g. wire. Can anyone explain to me how to convert this to use the 28g wire as I do not have a table or equation in my books to do so?

So, what it all boils down to, is that all the inductor winding
equations have nothing to do with wire gauge. All the gauge is
going to do is determine the maximum number of turns-per-inch
your're going to get when the coil is close-wound. If using a
smaller gauge, you still use the same number of turns spread out
over the same distance as the original coil would have been. That
can get messy and not look so "pretty". The suggestion to go
ahead and spring for a small spool of the proper magnet wire is
a good one. It'll save you a lot of headaches.

Dean

: So, what it all boils down to, is that all the inductor winding

: equations have nothing to do with wire gauge. All the gauge is

: going to do is determine the maximum number of turns-per-inch

: your're going to get when the coil is close-wound. If using a

: smaller gauge, you still use the same number of turns spread out

: over the same distance as the original coil would have been. That

: can get messy and not look so "pretty". The suggestion to go

: ahead and spring for a small spool of the proper magnet wire is

: a good one. It'll save you a lot of headaches.

: Dean

Hi,
unless you need close tollerance, the coil should be useable with the smaller gauge wire.

I did some calculations with a similar circumstance, and the calculations for my circumstance was about 15% difference. I included a url below for your own calculations, but your coil should work. Your resonance point will be slightly higher in frequency.

If this is an old radio circuit, ie, twenties vintage, you may find that the change is for the better, as there were few standards in broadcasting, and some of those radios actually tuned down into the "Long wave" band.

http://www.ee.surrey.ac.uk/Workshop/advice/coils/index.html#turn

: I need to make a coil (250uH) with a primary of 17 turns of 26g. wire and a secondary with 102 turns of 26g. but only have a spool of 28g. wire. Can anyone explain to me how to convert this to use the 28g wire as I do not have a table or equation in my books to do so?