Any Tesla Coil fans out there?

[BrownOut]

Have you used those bottle capacitors for anything? I've heard tell they will work for a TC, but not the best.

 

[DerStrom8]

I've tried them with a few different transformers, but the capacitance is extremely low. I think I would need about 15 of them to get the right capacitance, which would be difficult because I don't drink. The construction of the bottle caps is also very picky and demanding, as the aluminum foil must be perfect without many wrinkles or holes, and the saltwater solution inside must be perfect to get a decent capacitance.

P.S. Besides, I'm running out of Aluminum foil

 

[RCinFLA]

For what it may or may not be worth back in '64 Popular Electronics did a few Tesla Coil articles called Big TC and Lil' TC. I built the big tc and with some tweaking finally got it working. I used a 15 KV 30mA neon sign transformer. The capacitors were hand made and I remember using copper foil snanwiched between plates of glass all mounted in wood. Each cap I used 3 plates of glass, I remember that much. I found this old refrence to the article on Big TC. If you google enough you might find more on the article(s). However, the caps were home brew with trips to the hardware store.

The Lil' TC was sort of cool and useds a vacuum tube (valve) as an oscillator driving an old B&W TV flyback transformer.

Ron.

Built that rig. Used tin foil glued on a single piece of plate glass about 22"x22" square. Two nail points for spark gap. Hell of a racket. Wiped out any radio for in a quarter mile radius.

 

[DerStrom8]

Built that rig. Used tin foil glued on a single piece of plate glass about 22"x22" square. Two nail points for spark gap. Hell of a racket. Wiped out any radio for in a quarter mile radius.

Haha my first working high-voltage capacitor was made out of three soda bottles connected in parallel. I had it hooked up to my 9kV NST with a spark gap, and every time I fired it up, the RF set off my smoke detectors, my answering machine, and did something to my phones. I had to disconnect the main phone lines and reconnect them five minutes later just to get everything working again. It also annoyed the heck out of my family when they were listening to radio or watching TV!

 

[Boncuk]

Hi DerStrom8,

may be you'll get some good ideas here:

https://www.tesladownunder.com

Here is an image published on the site.

Boncuk

 

[DerStrom8]

Hi DerStrom8,

may be you'll get some good ideas here:

https://www.tesladownunder.com

Here is an image published on the site.

Boncuk

Thanks, Boncuk. I've been to that site various times before, and it never fails to inspire me

 

[Reloadron]

Built that rig. Used tin foil glued on a single piece of plate glass about 22"x22" square. Two nail points for spark gap. Hell of a racket. Wiped out any radio for in a quarter mile radius.

Yeah, I hear that. I built my first novice ham rigs in '63 and then that coil in '64. My dad who was a ham and an EE did not appreciate my creativity. There was no cable TV in those days and every time I keyed something up within a few min the damn phone would ring. That was followed by my fathers voice... "Ronald, turn that damn thing off"! My little science experiments were later regulated to between midnight and 6 AM when TV stations were off the air. Damn neighbors!

Building the caps was pretty cool though. Yeah, aluminum foil also worked well.

Something I am unsure of is the newer neon sign transformers that are solid state. Not sure those will work well but never tried. I still have an old 9 KV 30 mA transformer lying around here. The original was 15 KV 30 mA. That thing got with it!

Ron

 

[DerStrom8]

Something I am unsure of is the newer neon sign transformers that are solid state. Not sure those will work well but never tried.

I have heard that these don't work very well, as the output is at a higher frequency than mains. I read that it is very difficult to get them to work.
I have a couple of NSTs similar to the ones in your photos, and I also remembered that I have a 7kV, 30mA transformer, as well.

 

[gary350]

Have you used those bottle capacitors for anything? I've heard tell they will work for a TC, but not the best.

YES bottle capacitors do work but they have a 70% power loss. Fill a bottle with salt water wrap the outside with aluminum foil. Set all the bottoms on a sheet of metal to connect all the bottles. Insert a wire down inside each bottle and connect them all together. This will work it gets you some small shinny sparks. Swap the bottles for come good capacitors the spark length increase 3 times and they turn into white hot lightning bolts.

 

[DerStrom8]

This will work it gets you some small shinny sparks. Swap the bottles for some good capacitors the spark length increase 3 times and they turn into white hot lightning bolts.

Unfortunately, I haven't been able to try this myself--no real capacitors
My first real tesla coil was about 10cm. tall and ran with a single beer bottle capacitor and my 9kV NST. Yeah, I know it was overkill, but it worked! I got a good 9-10cm arc from the topload. Here are a few photos:


This was actually my best tesla coil until I tried mounting the primary. For these photos, it was just 12 AWG copper wire coiled up in a cone, sitting on a few bottle caps. When I tried to mount it to a piece of wood, it changed the coupling and it didn't work very well, if at all. Then my cat knocked over my capacitor (which I spent a long time on to get everything right) and spilled it all over my workshop floor. I have just had the worst luck with this coil!

 

[BrownOut]

Damn cat! Maybe when you mounted your secondary, you changed the resonate frequency. That always needs to be checked.

 

[DerStrom8]

Damn cat! Maybe when you mounted your secondary, you changed the resonate frequency. That always needs to be checked.

That is probably true. I mentioned coupling because the shape of my primary changed when I mounted it. I found a "Tesla Coil Tuner" from RMCybernetics that I have been meaning to try, as well.

 

[BrownOut]

From the little I know about TC, resonance is more important than coupling.

 

[RCinFLA]

Generally you want them to operate in the 30 kHz to 100 kHz range. The more capacitance the lower the frequency, and the higher the output voltage. You don't want to go too low as they become more dangerous with deeper skin penetration with lower frequency.

The output is a dampened ringing waveform at the resonance of the primary LC tank circuit. For each spark jump (120 Hz) there is a 'kick in the pants' of the tuned primary circuit. It rings with an exponential envelope decay. The rate of decay is dependent on resonant tank Q. Loading from corona discharge from secondary loads the primary and increases damping rate. Output voltage drops off with higher frequency because the harmonics of the spark impulse drop off in amplitude with frequency.

New Tesla coils are being built with high frequency solid state switching power supply primaries, but all you get is high voltage corona arcing spray from secondary. The new solid state units just don't have the full human sensory impact of a loud snapping arc of the spark gap on an old 60 Hz unit.

 

[DerStrom8]

From the little I know about TC, resonance is more important than coupling.

I agree that resonance is very important in a tesla coil, but with improper coupling, the efficiency of the circuit decreases. If the coupling is too loose, less of the energy from the capacitor (discharged through the primary) is transferred to the secondary by means of the electro-magnetic field. This loss of energy reduces the efficiency of the overall circuit, thus decreasing the output voltage.

 

[DerStrom8]

Generally you want them to operate in the 30 kHz to 100 kHz range. The more capacitance the lower the frequency, and the higher the output voltage. You don't want to go too low as they become more dangerous with deeper skin penetration with lower frequency.

The output is a dampened ringing waveform at the resonance of the primary LC tank circuit. For each spark jump (120 Hz) there is a 'kick in the pants' of the tuned primary circuit. It rings with an exponential envelope decay. The rate of decay is dependent on resonant tank Q. Loading from corona discharge from secondary loads the primary and increases damping rate. Output voltage drops off with higher frequency because the harmonics of the spark impulse drop off in amplitude with frequency.

New Tesla coils are being built with high frequency solid state switching power supply primaries, but all you get is high voltage corona arcing spray from secondary. The new solid state units just don't have the full human sensory impact of a loud snapping arc of the spark gap on an old 60 Hz unit.

Thanks for this info, RC. It makes much more sense now. I appreciate your explanation!
As for the solid state tesla coils, I would sometime like to build one of my own, as my major interest is "smaller" electronics, which comprise the driver circuit. Unfortunately, at this point, my budget is rather low, and it is quite difficult to scrounge together the parts I would need for a SSTC.

 

[Rbeckett]

Funny Tesla should come up again. Just watched a History Chanel show on AC and Nickola Tesla. History will run it again @ differeng times for about a month so if you missed it you can probably get it agin soon. It's History Chanel so it will be worth watching if you have the time.
Bob

 

[DerStrom8]

Funny Tesla should come up again. Just watched a History Chanel show on AC and Nickola Tesla. History will run it again @ differeng times for about a month so if you missed it you can probably get it agin soon. It's History Chanel so it will be worth watching if you have the time.
Bob

That sounds very helpful! I don't get the history channel myself, but I'm sure I could find a site that would let me stream it. Thanks!

 

[DerStrom8]

Okay, here I go again...
I found **broken link removed** one on ebay. The seller includes in the description that it can be used for a tesla coil, but a lot of people who say that have no idea what they are talking about. So, everybody, what do you think? Is it tesla coil worthy?
Many thanks!

EDIT: I see that it is rated for 20kV DC, but I don't believe it is polarized. However, I may easily be wrong

 

[killivolt]

Your plan is to run 2 in parallel then ? 02uf @ 20kv

Edit: The overall physical size seem ok, but then again do you want to eat up $24 or so shipping and handling on an experiment.

Edit:Edit: I didn't see the make offer "excellent"