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Questions about my First Tesla Coil

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bomberguy92

Thu Dec 20 2007, 11:36PM

Registered Member #1181 Joined: Mon Dec 17 2007, 10:48PM
Location: Iowa USA
Posts: 17

Sorry, I have another question just so I don't end up plowing up the $30 i spent on caps for my MMC.
Does it matter how they are possitioned went i link them together? I need 1 row of 16 caps to get the specs I need.
This is a quick diagram i drew up hope you can get what i'm trying to show you.

Does it matter witch one i use or will it work as long as they are connected together. lets call the top set #1 and the bottom #2 to make things easier. I would like your input, I bet this is probably a dumb question but I dont want to waist $30.

Thanks

Jeff Sadowski

Fri Dec 21 2007, 12:17AM

Registered Member #1185 Joined: Thu Dec 20 2007, 04:40PM
Location:
Posts: 17

I recommend beer bottle caps much cheaper and I'm getting a Terry Filter as Aaron recommended (set me back $80 from that Tesla coil store on ebay but the specs are here

) for me I blew 2 transformers already on my Tesla coil with a similar secondary. If you don't have one get a cap meter they cost about $40 but are worth every penny for high voltage experiments no cap could stand up to the abuse the beer bottle caps have withstood I blew a cap from ones I bought earlier I'll post pictures of it. I'll have to call that test 0 since it came before all the ones I mentioned ooh I got some stories to tell

this is great.

Shaun

Fri Dec 21 2007, 03:07AM

Registered Member #690 Joined: Tue May 08 2007, 03:47AM
Location: New Jersey, USA
Posts: 616

Well, the caps in a straight line will have less stray inductance, but with a spark gap coil that doesn't really mean anything.

HV Enthusiast

Fri Dec 21 2007, 11:15AM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068

MMC orientation really doesn't matter. Most are side-by-side as it takes up less room (linear)

wrote ...

Well, the caps in a straight line will have less stray inductance, but with a spark gap coil that doesn't really mean anything.

Not sure how it would differ between spark gap and SSTC. Whatever small inductance you have in there would be swamped up by the much, much larger inductance of the primary anyways, so it really wouldn't matter.

J. Aaron Holmes

Fri Dec 21 2007, 05:06PM

Registered Member #477 Joined: Tue Jun 20 2006, 11:51PM
Location: Seattle, WA
Posts: 546

EastVoltResearch wrote ...

Not sure how it would differ between spark gap and SSTC. Whatever small inductance you have in there would be swamped up by the much, much larger inductance of the primary anyways, so it really wouldn't matter.

Right. Unless you're Steve Conner and you're trying to one-up OLTC II and your primary ends up only being half of a turn because otherwise your coil's resonant frequency would be audible

Cheers,
Aaron, N7OE

bomberguy92

Sun Dec 23 2007, 01:56AM

Registered Member #1181 Joined: Mon Dec 17 2007, 10:48PM
Location: Iowa USA
Posts: 17

Just updating you on my progress:
My NST arrived today and to test it out I built a quick Jacobs ladder. I gave me a chance to test my NST and my controller. My controller consists of a 3 prong plug connected to a fuse with a built in switch that then goes to a dimmer switch. The dimmer will then go to a RFI filter as soon as I get one.

Test Results: NST works fine, Dimmer switch doesn't work (will need to get a new one), Jacob's Ladders are very touchy when being adjusted.

Here Are some pics:

Just this little Jacobs ladder was fun, it needs alot of fine tunning but it was great. I can't wait till I actually make my Tesla Coil. Just waiting on caps and I'll be all ready to go.

J. Aaron Holmes

Sun Dec 23 2007, 07:10AM

Registered Member #477 Joined: Tue Jun 20 2006, 11:51PM
Location: Seattle, WA
Posts: 546

bomberguy92 wrote ...

My controller consists of a 3 prong plug connected to a fuse with a built in switch that then goes to a dimmer switch. The dimmer will then go to a RFI filter as soon as I get one.

Jeff:

Transformer looks healthy. That's good! On the dimmer: I'm a little dubious of using those in-wall or in-cord triac light dimmers for stuff like this. It's been gotten away with before, but they're really meant for resistive loads only and hate RF. At least you describe putting the RFI filter on the NST side of the dimmer. That's probably a good idea! I'd be looking for a small 5A or 10A variac to use instead. The kind that come with an on/off switch and built-in electrical sockets. Those are nice. They're all over eBay too. Better yet: Ask Santa! (Whoops! How non-PC of me. I must want to be banned or something...

)

All that said: While a variac is good thing to have in a general-purpose power controller, it probably won't find much use in a small NST-based coil project. At least not with a static spark gap. With your gap set to take maximum advantage of your 9kV NST, your coil won't start firing until you've got the voltage turned all the way up anyway. Conversely, with a rotary-type gap, a voltage-control variac is a very effective way to control the power going into the coil because gap spacing is usually just "as close as possible" and depends much less on the primary voltage.

So keep that in mind. Small SGTC's are often just "on" or "off".

Merry Christmas (Whoops!!! I'm a goner now for sure...

)
Cheers,
Aaron, N7OE

bomberguy92

Sun Dec 23 2007, 03:55PM

Registered Member #1181 Joined: Mon Dec 17 2007, 10:48PM
Location: Iowa USA
Posts: 17

I tested my spark gap today and have a few questions about my results. My spark gap consists of 7, 3" long 1" copper pipes. connected side by side in a line on a piece of plastic fiber board making a total of 6 gaps to adjust to. after my test I could only get it to arch over the first 3 gaps (first 4 pipes). is this all the gaps I would need or do I need to adjust the other gaps closer so the arch will jump more of them.

I am also worried if when I turn my NST on and there is no arching in my spark gap or Jacob's ladder if that means that it is arching internally to complete the circut.

Oh and my spark gap is conneted to my NST with a pair of battery clips I got at the hardware store.

Thanks and I will keep you updated.

Merry Winter Break

Is that PC enough

J. Aaron Holmes

Sun Dec 23 2007, 05:16PM

Registered Member #477 Joined: Tue Jun 20 2006, 11:51PM
Location: Seattle, WA
Posts: 546

bomberguy92 wrote ...

I tested my spark gap today and have a few questions about my results. My spark gap consists of 7, 3" long 1" copper pipes. connected side by side in a line on a piece of plastic fiber board making a total of 6 gaps to adjust to. after my test I could only get it to arch over the first 3 gaps (first 4 pipes). is this all the gaps I would need or do I need to adjust the other gaps closer so the arch will jump more of them.

You won't really know how your gap is going to behave until you have your coil assembled and can charge/discharge a cap across it. But don't use a capacitor unless the rest of the coil is also present, else bad things can happen to your capacitor and/or transformer. Jumping three or four gaps is probably fine, but with 1" pipe you might find that the sparks tend to jump only at the ends of the pipes, leading to much faster fouling of the gaps and requiring you to clean them much more often. Smaller-diameter pipe may allow more even firing all over the pipes, and may also permit you to put more of them in series (spark may tend to jump just a little bit further). This is all because sparks tend to have an easier time originating from sharper surfaces than from very large, smooth surfaces. However you don't want your gap to be just two nails either (as you probably know), since your firing voltage will become extremely erratic and your gap resistance will be higher, hence increasing losses.

bomberguy92 wrote ...

I am also worried if when I turn my NST on and there is no arching in my spark gap or Jacob's ladder if that means that it is arching internally to complete the circut.

Unless you have your primary capacitor hooked up and are dry-firing it across your gap (again, very bad!), then I wouldn't be worried about it. Unless it's been damaged already by something else, the transformer should stand up to its own open-circuit voltage without self-destructing.

Cheers,
Aaron, N7OE

bomberguy92

Mon Dec 24 2007, 05:12AM

Registered Member #1181 Joined: Mon Dec 17 2007, 10:48PM
Location: Iowa USA
Posts: 17

I'm planning on building my torroid tomorrow. I am going to make it out of 4 inch ducking and pie tins. I can't seem to find just cheap normal pie tins. Guess moms need special coatings and rubber grips. So I'm wondering if I can use the disposable foil ones, or would they be to flimsy?

Thanks

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