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Registered Member #1630
Joined: Sat Aug 09 2008, 11:36AM
Location: Seoul Korea
Posts: 115
You might not get exactly the inductance from the coil you want, but you have more current to play with. Expect brighter hotter sparks. Maybe a little bit shorter streamers?? that's my guess. Anyways we will see :)
Registered Member #480
Joined: Thu Jul 06 2006, 07:08PM
Location: North America
Posts: 644
Come on all you "experts" who are offering "help": take a little time to read and interpret what Tigeris is saying, and double-check the "suggested help" that you are offering to make sure it makes sense, and doesn't add further confusion.
Its highly unlikely that Tigeris has a ".01pF", 100Kv capacitor; has anyone here ever seen a .01pF capacitor?? More likely, he has a .01uF, 100Kv capacitor by FCI, possibly like the ones sold by Fair Radio years ago. These large, white, rectangular plastic-cased capacitors used polyester dielectric, and were oil-filled. This was the capacitor I used in my first Tesla coil, and even though it supposedly utilized poleyseter dielectric, I was able to obtain 30" streamers with a single 15/60 NST and a simple copper-pipe static gap.
Coronafix, many successful Tesla coils have been built using "doorknob" capacitors. Some types of doorknob capacitors ARE rated for RF use, and even the doorknob capacitors designed for DC applications will work adequately in small coils. For an example of a nicely designed small TC using a DC doorknob capacitor, see Bill Wysock's Model 1 at TTR.com.
Seoul Laser, you state that since Tigeris is using a transformer rated at 360VA, he must use a tank capacitor rated at a MAXIMUM of 36Kv. This is nonsense; there is no relationship between the VA rating of the HV supply transformer and the voltage rating of the capacitor. Additionally, there is no "maximum" voltage rating for the tank cap; for reliability, feel free to use the highest voltage that is economically feasible within a reasonable physical size factor.
Also, you state that a 100Kv capacitor cannot be "properly" charged by a 12Kv power supply. Again, this is nonsense. In a Tesla coil circuit, the ability of a 12Kv power supply to "properly" charge a 10nF capacitor is based on the charging current that the transformer can provide. Actually, a .01uF capacitor is just about a perfect match for a 12Kv, 30ma NST static-gap Tesla coil (a safe "LTR", or Larger-Than-Resonant capacitance value).
Especially since Tigeris stated that his first coil was a total failure, we should try to take care not to further his pain by providing invalid or inaccurate "advice" for his second attempt at building a coil.
Registered Member #160
Joined: Mon Feb 13 2006, 02:07AM
Location: Melbourne, Australia
Posts: 938
Herr Zapp wrote ...
Its highly unlikely that Tigeris has a ".01pF", 100Kv capacitor; has anyone here ever seen a .01pF capacitor?? More likely, he has a .01uF, 100Kv capacitor by FCI, possibly like the ones sold by Fair Radio years ago. These large, white, rectangular plastic-cased capacitors used polyester dielectric, and were oil-filled.
This may be correct, but he stated that it was pF and not nF. Concerning the doorknobs, it is my understanding that most will not survive TC use. I expect Bill to know which types of doorknobs will work but not most people. Before you start putting down those trying to actually help Tigeris, you might want to get off your high horse and supply some help yourself. I don't see your points as being particularly helpful.
Registered Member #1630
Joined: Sat Aug 09 2008, 11:36AM
Location: Seoul Korea
Posts: 115
Herr Zapp wrote ...
Come on all you "experts" who are offering "help": take a little time to read and interpret what Tigeris is saying, and double-check the "suggested help" that you are offering to make sure it makes sense, and doesn't add further confusion.
Its highly unlikely that Tigeris has a ".01pF", 100Kv capacitor; has anyone here ever seen a .01pF capacitor?? More likely, he has a .01uF, 100Kv capacitor by FCI, possibly like the ones sold by Fair Radio years ago. These large, white, rectangular plastic-cased capacitors used polyester dielectric, and were oil-filled. This was the capacitor I used in my first Tesla coil, and even though it supposedly utilized poleyseter dielectric, I was able to obtain 30" streamers with a single 15/60 NST and a simple copper-pipe static gap.
Coronafix, many successful Tesla coils have been built using "doorknob" capacitors. Some types of doorknob capacitors ARE rated for RF use, and even the doorknob capacitors designed for DC applications will work adequately in small coils. For an example of a nicely designed small TC using a DC doorknob capacitor, see Bill Wysock's Model 1 at TTR.com.
Seoul Laser, you state that since Tigeris is using a transformer rated at 360VA, he must use a tank capacitor rated at a MAXIMUM of 36Kv. This is nonsense; there is no relationship between the VA rating of the HV supply transformer and the voltage rating of the capacitor. Additionally, there is no "maximum" voltage rating for the tank cap; for reliability, feel free to use the highest voltage that is economically feasible within a reasonable physical size factor.
Also, you state that a 100Kv capacitor cannot be "properly" charged by a 12Kv power supply. Again, this is nonsense. In a Tesla coil circuit, the ability of a 12Kv power supply to "properly" charge a 10nF capacitor is based on the charging current that the transformer can provide. Actually, a .01uF capacitor is just about a perfect match for a 12Kv, 30ma NST static-gap Tesla coil (a safe "LTR", or Larger-Than-Resonant capacitance value).
Especially since Tigeris stated that his first coil was a total failure, we should try to take care not to further his pain by providing invalid or inaccurate "advice" for his second attempt at building a coil.
Regards, Herr Zapp
I don't know what you are on about, firstly i think it is you who don't understand. 100Kv capacitor cannot be charged to 100Kv off a 12Kv neon in a TC .. this is indeed correct. ..why .. your gap is get to fire at 20-25Kv ~2.3cm. If he set it to fire at 10cm.. yes. I also NEVER mentioned VA had anything to do with capacitance. What planet are you on. I made a comment to do with the 12Kv transformer being 30mA @ NPF = 360VA . I think you'd better read again. -- Wrong about the Doorknob caps, you can use them but they aren't efficient. Barium Titanate is about the only ceramic that can handle RF reasonably well without cracking. It is poor for larger applications.
Registered Member #480
Joined: Thu Jul 06 2006, 07:08PM
Location: North America
Posts: 644
Gentlemen -
Please CAREFULLY read what I said, and stop with all the whining about hurt feelings, high horses, etc, etc. No one is being disparaged or "put down" here. Our objective should be to help Tigeris understand how a Tesla coil operates, and help him achieve successsful first light with his coil, without inadvertantly adding confusion or misinformation. At the end of my post I tried to summarize this, but apparently it just didn't get through to everyone:
"Especially since Tigeris stated that his first coil was a total failure, we should try to take care not to further his pain by providing invalid or inaccurate "advice" for his second attempt at building a coil."
McConner: Thank you for understanding the point I was trying to make about the improbability of a ".01pF" capacitor. Please tightly replace the cork in your bottle of hydrogen atoms so they do not escape and conceal other small parts on your workbench.
Coronafix: You stated "OK, doorknob caps are a no no, no good for pulse work such as a Tesla coil." This type of blanket statement IS inaccurate and misleading. If you know enough about ceramic doorknob caps to be offering "advice" about their suitability for use in a TC circuit, then go ahead and provide some insight into the different types of HV ceramic capacitors, the different dielectric materials used, the different dissipation factors, how to differentiate between the different types, and the risks and disadvantages of using a DC rated ceramic cap as the tank cap in a Tesla coil circuit. This type of information would be useful to Tigeris. As proof that ceramic doorknob capacitors CAN be successfully used in a TC, I provided a pointer to Wm. Wysock's Model 1 TC, including photos of the coil in operation. Incidentally, I believe the Sprague ceramic doorknob cap Bill used in this particular Model 1 is a DC-rated cap, not a low-loss RF-rated cap, and he does happen to have it connected directly across the NST secondary. Thanks to pioneers like Terry Fritz, who worked very hard to replace "tribal knowledge" and years of assumptions with real-world test data, we know that this circuit topology may not be the best for reducing stress on the cap and/or NST, but it does "work".
Seoul - This is EXACTLY what you wrote: "There are a few problems i can see here." 1# a 12 Kv NST 30mA runs 360VA --- you should be running a maximum of 36kvdc rated capacitor."
There is no "maximum" voltage rating for a TC tank cap - the higher the voltage rating, the better. Perhaps you meant a "minimum" voltage rating of 36Kv, but that's not what you wrote.
Additionally, you ranted about a 12Kv NST not being able to charge the capacitor to 100KV. This should be obvious to everyone on this list. I made absolutely no claims that a 12Kv RMS power supply could magically charge ANY capacitor to 100KV. We are talking about Tigeris' setup, with what I am assuming is really a .01uF tank capacitor, and a 12Kv, 30ma NST. Given these components, the 12Kv NST is perfectly capable of providing enough input power to a .01uF capacitor to run a small TC. Assuming reasonable losses, a healthy NST, and a properly adjusted spark gap, the tank cap should be capable of being charged to at least 15Kv.
Dr Spark - I agree with you fully that Tigeris may not have done enough background research to REALLY understand TC design and construction. If he is experiencing serious problems just getting the tank circuit set up, he may have a much more serious problem understanding the subtle factors involved in tuning the coil, especially if he lacks test equipment. I have helped numerous first-time coil builders debug their coils, and many of them had a very limited understanding of resonance and how it is achieved. Most naively thought that a TC was like a battery and a light bulb: if you just hook up the wires correctly, it MUST work.
Tigeris - If you have not already done so, I suggest that you spend several hours diligently studying Richie Burnett's Tesla coil website at:
In my opinion, this is still the world's best source of information for a beginning Tesla coil builder. There is a tremendous amount of information here, so focus initially on the sections covering spark-gap coils. After you really have a good understanding of what every individual component in a Tesla coil does, and how a coil operates, then use a Tesla coil design program to completely design (ON PAPER), your coil. Start with a very simple program like Wintesla, then when you understand what's going on, and how different variables interact with each other, graduate to a more sophisticated program like JAVATC. Then, when you have a design finalized, run it back through this forum for a free "design review" before you start procuring more parts, or before you actually start construction. Many of us have learned "the hard way" what works, and what doesn't, and we may be able to help minimize your frustration with your "next" coil.
Also, and perhaps most importantly, carefully study, memorize and adopt the safety guidelines for dealing with high voltage apparatus, and especially with capacitors charged to high voltage. One good compilation of Tesla Coil Safety guidelines can be found at the home page of the Tesla Coil Mailing List at:
See the link to the "Safety Sheet" at the LH side of the page.
Registered Member #1535
Joined: Wed Jun 11 2008, 11:37PM
Location: Northeastern Pennsylvania - USA
Posts: 117
For what it's worth...
I also finished a tesla coil using a 12,000vac 30ma transformer. My tank capacitor is 24 942C20P15K-F in series. This brings my tank capacitance to 6.25nf. This is close to the recommended 6.6nf. 48kvdc rating as wired in series. The coil puts out near two feet.
Take the advice given in this thread, because it only takes seconds or less to smoke a nice bank like mine...
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Help with tesla coil
