Re: Beginner Questions about Core and Bobbin

I just looked at this project and its not "really" a tesla coil.  True tesla
coils are air-core resonating transformers that are designed to resonate at a
specific frequency, converting the energy from the primary most efficiently
into an high frequency alternating electrical potential.

The project you're working on seems to be a AC step-up transformer that is
connected to a air-core coil.  The circuit basically turns the supply voltage
(18-24vdc) into a sinusoidal AC voltage of about the same voltage through the
primary of the small step-up transformer.  The voltage is "stepped up" by the
ratio of the primary-secondary windings and the current is reduced by the
inverse of the same ratio.  The output is then connect directly to the air-core

coil, but I don't see any benefit to this other than providing a resistive load

for the output of the secondary (inductance should be fairly low).

If it needs to be done by "this" Friday, you might go buy a old "TV fly-back
transformer" and wrap a primary of 25-35 turns of 18ga wire around the
"primary" area of the core of the coil (it might already be wound - but it
might be better to replace the existing primary.  This "should" produce a nice
1-2 inch spark at the frequency set by your driver circuit.  You might also try

using the iron pipe core, but maybe double or triple the number of secondary
winding you do.  But remember this isn't a tesla coil but more of a high-freq.
high-voltage power supply.


Tesla List wrote:

> Original Poster: "Scott Allen" <scotta-at-midusa-dot-net>
> We are two high school physics students trying to build the Tesla Coil at
> http://www.e-etc-dot-com/electronics/hivolt/tesla/tesla.htm.  We have already
> purchased all of the parts for the coil on this page and have everything
> completed except the core.
> We cannot find anybody who can supply the AMIDON EA-77-250 ferrite core and
> bobbin.  We are hoping that a cast iron pipe and iron rod will substitute
> for the core and bobbin.  Is this correct?  If not then what should we use.
> What should be the dimensions of the core and bobbin.  We have tried
> contacting the person who posted the page, but he did not write the page.
> He found it elsewhere on the net and is not able to help us.
> We don't really know for sure what the core and bobbin is.  We are guessing
> that they are similar to a pipe and rod with the core (or rod) fitting
> inside the bobbin (pipe) is this correct?
> We are reaching the panic stage as the project is due Friday.  Any help you
> could give would be greatly appreciated.
> Thanks in Advance
> Michelle and Ruth