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Registered Member #1946
Joined: Sat Jan 31 2009, 11:37AM
Location: India
Posts: 43
Fraggle wrote ... All of the information you could possibly need is available from Google, I think you ought to spend a few hours reading and you`ll be sorted.
no actually I did spent a few hours looking for capacitor banks and similar terms on google, but all I found was the already made pics etc. and no real knowledge on how to make them, or abt the resistors and all :(
can u guide me to article or any useful pice of information thx:-)
PlasmaLover wrote ... .0285µF? That doesn't work out right. Are you thinking that each bottle is 2nF? It seems that you are, since you said yourself that your one cap is about 1nF. So, if you have 1nF and you put fifteen in series, you get 15nF. But, if you're making the caps yourself, I suggest you test them with a meter (if you have one on-hand) in order to make sure that they capacitance is right. The meter on a multimeter will work fine, just get wires small enough to stick into the holes on the meter. That's the tough part! =) It takes a little while to get it all set up.
Keep us updated!
By the way, in the future, I recommend using the CDE caps, as well, but since you don't have much time, that wouldn't work well.
oops sometime I scare myself too with the silly mistakes I make Oh well Ok, the 15 nF will be equal to 0.015 mF. still awesome enough I guess :)
I have a digital LCR meter at college which i use to measure them :)
and well I just took the permission of my teacher and wow you wont believe but I just came across one of those caps (the CDE), one of my classmate bought one of them for his own project, and I saw I calculated and I found that using them will be more cheaper than MMC cpas and more reliable too :) and now you also recommended them :D
The caps I found were rated at 4mF and 440 V AC
if I connect 27 of them in series, I get 12 kV voltage as required and also 0.148 mF capacitance
wont that be awesome? coz that will look good too and I guess more efficient than the bottle caps right?
I have a full tomorrow, whatever I have to do, I have to do tomorrow, the saturday as my teachers said is reserved for testing or maybe small work but not for a full fledge work day so Ill have to be very quick tomorrow
I now wanna know how to add resistors
Like this??
and can you tell me how to calculate the value of resistor across each capacitor??
pls tell me as soon as possible, ill check ur msgs before going to college tomorrow :)
and yeah I measured the inductance of secondary today it's 25.1 mH :)
is it good enough??
thanks again guys you guys have been very very helpful without you I would not have reached even till here, I hope to finish it tomorrow
Registered Member #1946
Joined: Sat Jan 31 2009, 11:37AM
Location: India
Posts: 43
LithiumLord wrote ...
Well, in fact a bottle is around 1-2nF, however I don't like bottle MMCs due to higher loss factor and really heavy weight.
>fifteen in series In parallel (I know this was a typo as I kept sometimes mixing words myself like this - but just to make it more clear)
>and the small cap across output you said, whats that for? pf improv? Nope, I mean one between the neutral terminals - it will exclude the chance that some ground faults would cause RF to form up against the coils of the NST, eventually heating it or causing a damage or internal flashover.
wow so even just one bottle capacitor is good enough as per voltage? and we need multiple just for the capacitance?
and I am sorry I feel dumb to ask this but can you mark the position of the capacitor you were asking mew to add pls thx
400 pixels max image width, it's the board rules d00d! thx again:-)
Registered Member #1225
Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253
It is not absolutely required, but it seems that people say to switch the capacitor and spark gap position. It will be so that the primary and capacitor are in series, connected parallel with the NST, and the spark gap is parallel with the NST.
Registered Member #480
Joined: Thu Jul 06 2006, 07:08PM
Location: North America
Posts: 644
Kashish -
It's pretty obvious that you do not have even the most basic understanding of what a Tesla coil is, how it operates, or how a Tesla coil circuit is configured. Without gaining some understanding of these topics, your chances of getting a Tesla coil assembled, tuned and operating are just about nil.
For a start, go to Richie Burnett's extremely informative Tesla coil website (still the world's best) at: and read up on Spark Gap Tesla Coils. Richie's site will explain the purpose and function of each component in a Tesla coil, what their electrical characteristics are, and the theory of operation. Without gaining at least a minimal understanding of what a Tesla coil is and how it operates, you won't be successful in getting one running.
A few other comments:
1. With your 6KV @ 30ma transformer, you need a tank capacitor value of around .018uF. Your 4 microfarad @ 440 VAC capacitors are unsuitable because their capacitance value is far, far too large. You would need over 200 of them connected in series to achieve your target capacitance value. Do you understand how to calculate the value of series and parallel connected capacitors? If not, you absolutely need to gain some knowledge of basic electronics.
See: for info on series and parallel connected capacitors, and how to calculate their values.
2. Your best option for a low-cost, readily available tank capacitor will be to use an array of salt-water bottle caps. A typical beer-bottle salt-water capacitor will have a capacitance value of around .0007uF to .001uF, and will withstand 20KV. If you assemble an array of 15-18 of these bottles connected in PARALLEL, you will be near your target capacitance value. Empty beer bottles and a few meters of scrap copper wire can be salvaged or obtained at very low cost.
3. Your sketch of your MMC shows the bleeder resistors in SERIES with the capacitors; this is incorrect. If you understood that a Tesla coil tank circuit has to carry large pulses of current, you would immediately see that your sketch is completely wrong, and that the high-value resistors would effectively prevent ANY useful current from flowing in the circuit. In an MMC tank capacitor array, each individual capacitor has a bleeder resistor connected in PARALLEL with it, not in SERIES between capacitors. The value of a bleeder resistor is based on the time constant of the circuit (how rapidly you want the capacitor to discharge). For typical MMC capacitors used in Tesla coil circuits, a value of 10 megohms (10 million ohms) works well.
4. Your sketch of the Tesla coil circuit shows the tank capacitor connected across the HV transformer. This arrangement may apply higher stresses to the transformer's secondary insulation than if the spark gap were connected across the transformer. Interchange the positions of the tank capacitor and the spark gap, and your transformer will have a better chance of surviving.
Really, your best option at this point is to spend some MORE time reading up on Tesla coil design and theory of operation. You absolutely MUST have some basic understanding of what a Tesla coil is, what the various parts do, and especially about how a coil is "tuned" to achieve resonance. A Tesla coil may appear to be just a few coils of wire, a spark gap, a capacitor, and a transformer, but in actuality the operation is a quite bit more complex. It's absolutely essential that you understand what RESONANCE is, and how the primary and secondary circuits are "tuned" to achieve resonance, to be able to get your coil operational. Richie's website provides a very detailed but easily undestood explanation of what resonance is, and how it is achieved.
(Also, it's OK to just say "Hello, I'm Kashish, I'm 14 years old, I live in India, I saw a Tesla coil on the Internet and now I want to build one." Telling us that you are just about to "graduate" from Electrical Engineering college, and need to build a Tesla coil as a condition of graduation, doesn't seem to be truthful. The people on this forum are very willing to help you in any way possible, regardless of your age, location, schooling, or background.)
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
Thanks for the valuable input, Herr Zapp and LithiumLord. I'd have liked to help out too, but one of my New Year's resolutions was to ignore any thread with a smiley in the title.
Herr Zapp already said this, but I'm going to repeat it. Don't put resistors in series with your capacitors! It's completely wrong. Your coil will hardly work and/or the resistors will go on fire.
Tesla coils might be hard to optimize for ultimate performance, but it's pretty easy to slap together something that "kind of works". My favourite is the Trashy Tesla: If this guy can do it, so can you.
Registered Member #1946
Joined: Sat Jan 31 2009, 11:37AM
Location: India
Posts: 43
Herr Zapp wrote ... Also, it's OK to just say "Hello, I'm Kashish, I'm 14 years old, I live in India, I saw a Tesla coil on the Internet and now I want to build one." Telling us that you are just about to "graduate" from Electrical Engineering college, and need to build a Tesla coil as a condition of graduation, doesn't seem to be truthful. The people on this forum are very willing to help you in any way possible, regardless of your age, location, schooling, or background
I want t clear this out first y birth date is 7th november 1990, I am in college - Mehr Chand Polytechnic College, I am final year electrical engg. student with 2 months to go before my college ends. IDK where you read that 14 year old thing, but I am ready anytime to show myself on cam if you want, I would never lie in my life to people I am gonna ask for help.
and yeah thanks for your post mate, really very very helpful :) Ill reply again in like half hour, I am reading the site articles and all you gave.
and yeah this is the first time I am engaging in any kind of practical job, that's why I am being very silly at some places, its just the study structure of our country, very theoretical, very few college gives good practical info. :)
Registered Member #480
Joined: Thu Jul 06 2006, 07:08PM
Location: North America
Posts: 644
Kashish -
Take a look at a new thread on this forum titled "Need your Help please", by Tareef.
He has constructed a very nicely made Tesla coil, using what appear to be all the correct components. However, has has not yet been able to get this coil "running".
It might be useful for you to take a close look at his coil design, and follow the steps as we help him troubleshoot this coil, determine why it will not run, and what needs to be corrected to get it running properly.
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Tesla Coil Help!! Got only 3 days left to complete my project, plsss help
