Tesla Coil Project

I agree to both comments.

The lego is just a winding jig. The varnish i have is slightly glittery aswell so that might cause arc over above a certain voltage.

It'll make it look nice though!

Buy your own clear varnish and stop pinching your girlfriends!

I fully understood that the winding jig only was Lego. I again salute your creativity for using it.

Actual glitter since it is often aluminized mylar would not be a good idea to have for a varnish. An opalescence sheen in the varnish would likely not matter unless it was an actual metal powder making the iridescence. The trouble is that you will likely never be able to now before hand if the varnish is a problem before you wind. If you don't mind having to possibly rewind the coil, then go for it.

Don't forget though that working with a Tesla coil is like working with a feral animal. You can quickly get bit in so many ways. Keep a CO2 extinguisher nearby and a safe power disconnect in the circuit.

Assuming the wire for the windings are varnished, that should handle the electrical needs*, and then the nail varnish is just mechanical to keep things from slipping.

*If sizable lengths of wire then lap over or next to each other, there might be enough voltage difference to create a problem.

I do not have a girlfriend, women are much harder to understand than building a tesla coil.

I would cease the use of glittery nail varnish. Use a spar varnish or Varathane. Check out www.pupman.com to answer most, if not all, of your questions regarding Tesla coils.

I also love the use of the Legos, by the way.

Is this tesla coil too small to work? it is about 10 cm tall.

Didn't you do your math first?

To make a working Tesla coil its not just a matter of winding a bunch of random turns of what ever size of wire you have laying around.

It has to have the exact right length, inductance and capacitance all balanced out to an exact frequency all at once.

The total length of the wire has to be 1/4 of the wavelength of the frequency and the inductance and capacitance(top load plus self capacitance) have to be balanced to match resonance on that frequency.

No Tesla coil is too small to work. I have seen them only inches tall. You really need to check out www.pupman.com.

Agreed, no Tesla coil is too small to work. Now the height of the Tesla coil will limit how high the voltage can go before a spark will discharge, but... I also agree that www.pupman.com has some very good information. I particularly like the Safety Sheet. Several parts of any Tesla coil can kill.

Yah, once they get over 7,500v input it doesn't "tickle" anymore.

Have a look at http://www.extremeelectronics.co.uk/pictures/gallery/

I have almost finished winding the secondary coil and was wondering what the best power supply would be. I have a home made transformer which produces about 3000volts. Would a flyback transformer be better?

in the tesla the primary winding should be heavy like welding cable and the secondary a 20thou armature wire with a 25lb test fishing line in between windings for insulation, I made one once when had shop and time out of a linolium cardboard tube baked in oven to dry then primed with motor winding paint, after winding it got several more coats, it was powered first off a 15kv 250ma neon sign transformer and two navy ship transmitter caps the size of four cereal boxes with atwo hv diodes and crossing airgap of tungsten tig electrodes with the terminal cap a copper toilet float, it was deadly at that design since I never completed it with a laden jar cap tub to get the 980kv, it made about 150kv and when it discharged it sounded like a firecracker, Nikola Tesla was my hero, had several books on him and his designs, one was the design I just mentioned, lindsay books sold this book and is still in business, careful it can be the last thing you ever mess with, wish I had time to complete it but I took up ultralite airplanes and my time was consumed building and flying til retired,

Sincerely
Mitch retired peugeot mech

Thanks for the story, unfortunately i do not have a neon sign transformer or capacitors so i will have to make them.

You will much further ahead to just go on eBay and buy them opposed to trying to wind your own HV transformer and roll your own HV capacitors.

That all depends on the real goal here. To obtain a Tesla coil one can easily just buy a complete assembly. To gain the pride and knowledge of how a Tesla coil and all of the parts required to make it work takes a longer and more rewarding path. I suspect that since hydrogenhead has already shown some very creative effort to hand wind the coil, he/she will hand build much if not all of the parts.

I can make the coils and capacitors no problem, I just do not understand why the well insulated high voltage transformers i make arc over internally through the insulation and get destroyed.

Well I suspect that you've obviously made a few assumptions on the quality of the insulation in your transformer windings. The most common assumption I've observed that people make when working in extremely high voltage is that they forget that all things can be ionized if a sufficiently high voltage gradient gets applied. As we should all know here, once any material becomes ionized conduction instead of insulation happens. So just because your megger or my preference a Whetstone bridge allows you to calculate a very high resistance at a low voltage for your insulation does not mean that at the high voltages in your transformer the insulation is adequate. You should notice though that I said voltage gradient instead of just voltage. A thicker insulation will hold off a higher voltage. However, many lacquers become more brittle when thicker. So wrapping the windings in the coil or transformer can cause small cracks in the insulation that cannot be measured at low voltages. These cracks become paths for arcing at high voltage.

That's just two of the possible reasons that a low voltage sound insulation can turn into a disaster at high voltages.

Portions of the winding that span long lengths (many turns) of wire may have significant potential across them, and thus should be separated by insulation or distance (and some care with winding technique).

Tornado

Or would another method be to wind the high voltage transformer and completely soak it to the core with oil and leave it immersed in oil while the power is on? I have seen on various sites that oil completely eliminates corona.

Yes, immersion in oil will do several useful things. It will eliminate corona effects in the in the transformer which will minimize transformer winding arcing risks. It will also more efficiently transfer heat out of the transformer. The drawbacks of oil immersion should also be known before choosing this option. It can become messy, containment is a concern. You've added a difficult but possible to ignite fuel to a high voltage system that will be making sparks nearby (containment). With the need now for transformer containment you now need high voltage connectors that have oil seals. The electrical isolation quality of mineral oil does breakdown faster than electrical varnish but this quality is rated in years of continuous operation. Nobody I know of runs a Tesla coil 24/7, so this last drawback should not be a concern.

I do not have mineral oil, would normal lubrication oil be fine?

Not sure. Most electrical varnishes (all I have found) are formulated to not react with mineral oil. By definition going out of the box means uncharted territory. I have a vague recollection that one oil base did react with a varnish but which oil and which varnish I do not remember.

Mineral oil though should not be too expensive or hard to find.

Mineral oil insulation in transformers doesn't eliminate the possiblity of corona, it just reduces it significantly. Internal corona problems in power transformers are usually detected by the generation of hydrogen in the oil.

If you can find yourself an oil-insulated transformer in acceptable condition, you might consider it. Trying to build your own is not trivial, and if your oil is not sufficiently pure (contaminated with moisture, carbon, or other substances), you could have worse insulation then your dry wound units. However, an exploding oil-filled transformer is an environmental mess!

I could try some kind of resin, because i can't get a flyback transformer anywhere.

I have managed to get some epoxy resin and hardener. Would this be suitable for making a high voltage transformer? It needs to withstand at least 6000 volts.

I'm sure it can be used in most assemblies to easily withstand 6kV. I'm also sure that it can be part of a fabrication that arcs and ignites at just a few hundred volts. A fiber glass/epoxy circuit board standard has a voltage breakdown rating of +40kV for just a 1/16 of an inch thickness. Now is your grade of epoxy up to this standard. Could be?