Tesla Coil

[Lance]

Don't be sorry.

 

That should be fine.

[RICHARDBATTY]

"Will the spark gap produce bad uv probs for your eyes?"

 

Yes' date=' but its bright enough that you won’t want to look at it anyway. Its too bright to be able to make out any shapes.

 

"and what’s the potential for x ray production"

 

I don’t think there is much of any.

 

"Has anyone ever tried to build a silencer exhaust around the spark gap"

 

I have not heard of one. I think it would make the gap too hot.

 

"and what about using a rotating gap to keep it cool."

 

Yes that works too. It just takes a bit more work than two nails.

 

YT can probably answer some of these better.[/quote'] Thanks muchly

[sanjaygeorge]

What is the formula for calculating the frequency of primary coil and secondary coil??

[Lance]

Looks like all the formulas are written out here.

 

I prefer calculators myself.

 

Doh! There is a formula for saltwater caps. Sorry! But like a said, most beer bottles dont have a constant thickness.

 

 

Leyden Jar Capacitors

 

C = capacitance in microfarads

K = dielectric constant

D = diameter of jar in inches

H = height of jar in inches

T = thickness of jar in inches

[sanjaygeorge]

Can we connect TEsla coil with saltwater cap to AC power 220v to transformer???

[ultimax]

Lance, YT,

 

I've finished building my coil! It took me ~5 full days from start to finish but it's done! I'm testing it in school tomorrow. Hopefully it'll work. Will post pics soon. Maybe a video too!

 

THanks for all your help guys. You guys have been wonderful and were really forthcoming with answers and suggestions! Can't say the same for some coilers I emailed for help ...

[YT2095]

Please Please Please, do NOT FORGET your Earth strap!!!!

 

a good solid Ground connection is essential! A) for good coil performance and B) for safety of local equip AND your coil! )

 

all the best dude, and I really hope everything pans out nicely for you )

[sanjaygeorge]

Can we make tesla coil with igination coil??? who long will the sparks be? what is the amphere of the igination coil?? I am in a caos. I have my Science Exbhit in 3 weeks and I did'nt get any NST. It's nowhere to be seen. Any substitude???? Can we use the TV transformer????? I need help urgent..

[ultimax]

Hi YT,

 

what exactly is an earth strap? The RF ground connection from the secondary coil?

 

thanks!

 

Please Please Please' date=' do NOT FORGET your Earth strap!!!!

 

a good solid Ground connection is essential! A) for good coil performance and B) for safety of local equip AND your coil! )

 

all the best dude, and I really hope everything pans out nicely for you )[/quote']

[YT2095]

yeah the RF ground

 

Don`t use the one supplied for your house!

[ultimax]

Hi everyone,

 

tested my coil out in school today and it worked right away, much to my relief. Here are some of the specs of my coil :

 

Transformer : NST, 15kV, 30mA

 

Diameter of secondary coil: 90mm

Diameter of magnet wire: 24 AWG, 0.51mm

Number of turns: ~883

 

Toroid: 2 aluminium wok covers joined together with aluminium tape.

Estimated dimensions: 310mm in diamter, 210mm in height.

 

(I'm probably gonna construct a traditional toroid as I can't calculate the capacitance of this toroid, and I'm not sure if it's any good in the first place)

 

Inner diameter of primary coil: 140mm

Diameter of copper tubing: 1/4"

Spacing between coils: 1/4"

Number of turns: 13-14

 

Spark gap:

Number of electrodes: 7

Material used: Aluminium curtain rails

Spark gap: ~1.5mm between each rail, ~9mm in total.

Cooling mechanism: 80mm computer fans, blowing into the spark gap housing, rather than sucking air out.

 

Total construction time: ~7 days from start to finish.

 

Photos:

 

 

My coil in the lab. Note the atypical toroid.

 

 

The spark gap. I removed the last rail as I needed a wider spark gap. The fans limited how far I could go with 8 rails. So I now have 7.

 

Performance:

 

The good news is, everything worked from the start. There was some arcing on the capacitor bank because of a poorly soldered connection, but that was soon fixed. Other than that, the coil generated a good amount of noise, ozone and streamers.

 

The transformer was connected to a variac, and we never went above 150V (the transformer's rated at 240V).

 

After the initial satisfaction of having everything work, discontent took over. My prof was very happy with the streamers, but seeing how other coils using similar NSTs have generated sparks 2-3 times the length of what I saw today, I was somewhat disappointed haha.

 

It's funny that we didn't run the coil "as is" ie. without an electrode at the top of the toroid. So I don't know if breakouts are possible from the toroid. But anyway, max streamer length of the day was abt 200-250mm. Maybe 180mm's a more conservative estimate.

 

Here are some pics! My 1.3 megapixel camera is really bad with shots in the dark, so pls excuse the quality. It barely captured the streamers!

 

 

 

 

QUESTIONS and improvements.

 

Yes, more from me! The general question is (as if it isn't already obvious haha), how do I improve spark length? Where do I start? Is there a methodical approach?

 

More specific questions:

 

1. How do I calculate the capacitance of this atypical toroid?

 

2. WOuld a traditional doughnut shaped toroid work better?

 

2. DOes it matter if the fans blow into the spark gap housing, or suck air out (the traditional way). I find there's more air flow with the former than with the latter.

 

3. How impt is using a stake in the ground as the RF ground? Does the length of the stake really matter? Like 3m VS 5m?

 

We were in a lab (on the 5th storey of a building) so we hooked the coil up to a ground wire. I have no idea where it's connected to, but it definitely wasn't from a socket. Anyway, if you don't have access to a patch of dirt/grass, what's the best ground to use?

 

thanks!

 

Shu

[YT2095]

WELL DONE!!! )))

 

I`m impressed! nice pics too.

 

1. no idea how to calculate it (I use trial and error method as I hate maths).

 

2. the shape isn`t all that critical in my experience, so long as it`s smooth without sticky outy bits

 

2. it doesn`t matter and the airflow will be the same either way. I prefer your method anyway, the fan doesn`t get any heat, Ozone or NOx gasses through it, extending its life

 

3. the Ground is essential, the better the ground the better the results (up to a point) a 3m or 5m copper pipe in the earth wont make any diff on a small coil, 1 meter would be plenty. as for indoors the cold water pipe is the best ground you`re likely to get, make sure it`s not tank fed water though, by law all Kitchen cold water supplies have to be direct, so there`s your best bet

 

again, Well Done that man!

[ultimax]

Hi YT,

 

thanks for the compliment!

 

I'm probably gonna go ahead with the traditional toroid. Just to make sure it's not the toroid which is the obstacle to having longer sparks.

 

I'm prob gonna redo the spark gap...again. My Prof pointed out that the rubber tubes I used to strap the aluminium rails down may lose their elasticity with time. I'm prob gonna cut my casing horizontally into 2, and sandwich the rails between them. the 2 halves will be joined by a plastic hinge on one side, and maybe leather or a piece of vinyl on the other. I'll also shift the fans to the top of the housing so that they're blowing down onto the fans, thru the gap. Right now most of the air is blowing across the bottom of the rail. Only a bit makes it thru the gaps between them. So who knows ... maybe quencing will be better and we'll see bigger sparks?

 

I'm also gonna take the coil home and borrow a variac from the lab. I'm suspicous of the ground connection we used in the lab. I'm not sure where it's from, or what it leads to, but I wanna try running the coil with a good ol' copper stake in the ground!

 

Shu

 

P.S. How good is an average coat of polyurethane? I'm trying to get my gap to spark in the middle, rather than the ends, so I'm thinking of dipping both ends in polyurethane? As it is, the sparks are sort of shielded from the air flow by the plastic supports they rest on.

 

 

WELL DONE!!! )))

 

I`m impressed! nice pics too.

 

1. no idea how to calculate it (I use trial and error method as I hate maths).

 

2. the shape isn`t all that critical in my experience' date=' so long as it`s smooth without sticky outy bits

 

2. it doesn`t matter and the airflow will be the same either way. I prefer your method anyway, the fan doesn`t get any heat, Ozone or NOx gasses through it, extending its life

 

3. the Ground is essential, the better the ground the better the results (up to a point) a 3m or 5m copper pipe in the earth wont make any diff on a small coil, 1 meter would be plenty. as for indoors the cold water pipe is the best ground you`re likely to get, make sure it`s not tank fed water though, by law all Kitchen cold water supplies have to be direct, so there`s your best bet

 

again, Well Done that man![/quote']

[Lance]

It looks great ultamax.

 

I'm sure you have already done this but did you tune it? Make sure to adjust the spark gap distances along with changing the primary turns. I think that even with a crapy ground you should be able to get larger sparks than that. Also keep in mind that your input was only around 9.5kv when you tested it.

 

Sorry I can’t be more of a help than that.

[ultimax]

It looks great ultamax.

 

I'm sure you have already done this but did you tune it? Make sure to adjust the spark gap distances along with changing the primary turns. I think that even with a crapy ground you should be able to get larger sparks than that. Also keep in mind that your input was only around 9.5kv when you tested it.

 

Sorry I can’t be more of a help than that.

 

so how should it go? More turns = wider gap? What's the relationship between gap length and increasing the length of the primary?

 

hey you've already been a great help. thanks a lot!

[Lance]

so how should it go? More turns = wider gap? What's the relationship between gap length and increasing the length of the primary?

 

I would only change one variable at a time. First I would find the best number of primary turns then I would mess with the spark gap.

[ultimax]

I would only change one variable at a time. First I would find the best number of primary turns then I would mess with the spark gap.

 

Hi Lance' date='

 

well I fiddled arnd with the spark gap length and blew a capacitor haha. Thank god I had spares, and that the rest of the bank was unaffected

 

I've tuned it somewhat and have gotten another inch or two. I think I'll leave it at that. Next, I'll try it with a proper ground connection. What do you think of hooking hte coil up to the lightning rod's ground strap? Good idea? Or bad idea?

 

Here's another photo:

 

[img']http://web.singnet.com.sg/~shuhuang/tesla_maltese_cross.jpg[/img]

[YT2095]

What do you think of hooking hte coil up to the lightning rod's ground strap? Good idea? Or bad idea?

are you on the top floor and the last connection to the strap??

 

if not then NO WAY do it! it`ll radiate upwards and out too, at best you`ll get TVI for several 100 yards, I live on the the 13`th floor (the top floor too) and I still cause probs if I use it

 

cold water plumbing seems to work alot better for some reason

[5614]

as im thinking of building one (but it will have to wait a bit because im busy at the moment) anyway... why is ultimax's sparks not as long as in other photos (google searches, other websites etc)???

 

basically what im trying to get at is what are THE most essential thing(s) for me to have to obtain maximum length sparks?

[YT2095]

basically what im trying to get at is what are THE most essential thing(s) for me to have to obtain maximum length sparks?

ALL of it!

[5614]

"All of it"??? hmm, thats gonna be hard, i was gonna skip out the electrical part, guess i'll have to include it now!

 

OK, i'll be more specific....

 

1) Is the shape of the toroid very specific, or can any circular-ish shape do?

 

2) Is more and bigger caps better? (presumably yes)

 

3) Is the voltage crucial?.. now dont be stupid here! like is there a mega difference between say 18KV and 25KV and 35KV? - obviously there will be some difference, but is it big enough to say, if you want a decent tesla coil then you must use at least xKV (where x is a variable!).

[Lance]

1) Is the shape of the toroid very specific' date=' or can any circular-ish shape do?

 

2) Is more and bigger caps better? (presumably yes)

 

3) Is the voltage crucial?.. now dont be stupid here! like is there a mega difference between say 18KV and 25KV and 35KV? - obviously there will be some difference, but is it big enough to say, if you want a decent tesla coil then you must use at least xKV (where x is a variable!).[/quote']

 

1) The toroid just can’t have any sharp points. That’s why toroid and spheres work best. You want the highest break-out voltage possible so a higher voltage will build up before you get sparks.

 

2) No! You must use a bank that’s around resonance. There are plenty of calculators to figure this out. A lot of people think that smaller caps are better because this creates a higher frequency and therefore larger arcs. If you use bigger caps eventually the frequency will get so low that there won’t be any output at all from the secondary.

 

3) Generally you want a lower voltage because extremely high voltage transformers can not supply any current. This is why neon sign transformers are used which range from 7.5kv-15kv. All of which will work great. Higher voltage transformers will likely not work at all. On the other hand if the voltage is too low you wont get a reliable spark gap working.

 

Although individual components of a tesla coil are not critical they all have to work together. Although you can use just about any cap bank or transformer they have to work together. You may buy a suitable transformer and a suitable bank but when you put them together they don’t work at all. This is why I suggest downloading Teslamap so you can calculate all of this stuff.

[5614]

i have got and used Teslamap... you recommended it to me (i think) in the SFN chatroom.

 

is there a difference between toroids which are, well, toroid shapes! and those which are circular or frying pan ones!

 

also, good point with the voltage, although presumably a 15KV would bring up a larger spark than a 7.5KV, although you wouldnt want to go much higher than 15KV?

[ultimax]

Hi YT,

 

I was in the garden the other day and noticed the lightning rod's ground strap terminating at what appears to be a solidly constructed stake pounded into the ground. Was wondering if I could make use of that instead of pounding another stake into the ground. That would save me some time and money.

 

It's just a thought. If it doesn't work well I can always go back to the ol' fashion way.

 

are you on the top floor and the last connection to the strap??

 

if not then NO WAY do it! it`ll radiate upwards and out too' date=' at best you`ll get TVI for several 100 yards, I live on the the 13`th floor (the top floor too) and I still cause probs if I use it

 

cold water plumbing seems to work alot better for some reason [/quote']

[ultimax]

as im thinking of building one (but it will have to wait a bit because im busy at the moment) anyway... why is ultimax's sparks not as long as in other photos (google searches' date=' other websites etc)???

 

basically what im trying to get at is what are THE most essential thing(s) for me to have to obtain maximum length sparks?[/quote']

 

My toroid's sort of small, and the coil was connected to a mysterious ground wire in the lab, not a proper ground roud. Come December, my coil will have a traditional, larger toroid, and I'll be testing it at home with a copper stake in the ground. I can't say I'll get bigger sparks, but I'm hopeful

 

As for the Crookes Tube photo, the sparks are short because I placed the tube near the coil