Anyone ever built a Tesla coil?

Aside from electronic stuff, I also like playing with high voltage. Here's a Tesla coil we built about 6 years ago. It stands about 6 feet tall and throws 7+ foot sparks. It consumes about 7.5 KW and 14.4 kilovolts from a 10 KVA pole transformer. Check out the video here if interested.

Stu

Greetings!

I have never built any, but I have always been fascinated with plasma devices. I have a few plasma devices and a lava lamp in my cube.

Those are neat too. Pretty pricey though. I guess I could build one. Maybe some day...

Stu

Greetings!

Let me amend that... Very small plasma devices...

Hehehe... that looks fun . I've always wanted to build some high voltage generators. Natalie, my girlfriend bought me a book called Homemade Lightning for Christmas which has got lots of projects in it. One day I'll get the time to build some of them.

The nearest I've got was when I used to rig up an old valve signal generator to a car's ignition coil. I'd set the signal generator to 10.4kHz (the coil seemed to give it's maximum output at this frequency) and grab hold of the output terminal of the coil. I used to get a continuous spark jumping between my mate's finger and mine of about 5mm IIRC. We couldn't do it for long 'cos it used to burn a hole in our fingers . I could pick up a fluorescent tube and it would glow quite nicely - like a light sabre . Nothing like the scale that you've done but fun none the less.

I shudder to think of what God has built...
Some wild stories were told over B&B (beer & barbeque) at Robs place at this years European meet...

/Michael

I thought he was more into explosives and flame.

Well, yes and no... it's usually the scale of the effect that he's into.

For example: Patrick (aka GOD - I am regretting starting this now, but NOOOO, my stupid felt tip has a mind of it's own...) finds an old Magicube flash box. Now you and me, maybe we go and find an old car battery, and just for a laugh we would flash the terminals to see them go FUMPHH!!! and then stagger about blind and giggling for five minutes, remembering the good old days of Kodak 110mmm flash photography.

Patrick's version: "I suddenly get the idea that I could make the biggest flashbulb in the universe: so I dig out that old 25 gallon glass pin bottle, stuff it full of magnesium wool, poke two electrodes through a cork and wax it into the bottle neck. Then I go to the top of the bluff overlooking the town and THEN I get out my old car battery, and just for a laugh I flash the terminals....."

Oh my GOD

...okay...

...scary...

...and he is still alive, obviously...

No offense, but there is a very thin line between genius and insanity. A genius will win the respect and admiration of his peers and maybe a Nobel Prize if he is lucky. A really lucky insane person might get a Darwin Award...

No, don't worry about Patrick's sanity. When/if you meet him, it will all become so clear...

I thought he was more into explosives and flame.

That too... But IIRC there was a Tesla coil (or something else that used bigass caps) involved when his sister interfered somehow (funny how fuzzy the details are :-).
Tossed him across the room - said it instilled a bit of respect for electricity in him... I have my doubts

Or that jar of nitrogen tri-iodid impounded and locked in the school safe... But that might have been his friend - as I said the details are fuzzy...

/Michael

Will it become clear before or after you've been blinded by the giant flashbulb?

Where do you even get that much magnesium wool anyway???

- Trevor

But IIRC there was a Tesla coil (or something else that used bigass caps)

The one in the video uses an 80,000 volt .05 uf cap. Fairly large I guess.

Where do you even get that much magnesium wool anyway???

I was wondering the same thing.

Stu

Now, don't exaggerate. It was only a five-gallon jar, and you forgot the step of flushing it with pure oxygen before sealing it.

Very long wires are also a good idea...

pca

That was when I was around 12, and it was only about 4-5kv at no more than 30mA or so. Yes, I still have the scar from the pencil-end-sized black-rimmed hole burned clear to the bone on my right forefinger, and the blisters on the other hand from the neutral wire, but no permanent harm was done Of course, if my sister hadn't wanted to watch TV and plugged in that particular extension cable, everything would have been fine.

I've never been able to do a thirty-foot backwards somersault from a seated position again, though.

I have to admit, I consider myself lucky to have gotten off so lightly. One lives and learns...

I wouldn't recommend this sort of thing as a hobby. It hurts.

The nitrogen iodide incident was around the age of fourteen, and was entirely the fault of a loopy friend, and a vice-principal who didn't follow instructions on the safe storage of unstable chemicals. I TOLD him to keep the container the right way up, but would he listen? Teachers!

pca

Where do you even get that much magnesium wool anyway???

Why, you scrape it off your 15Kg bar of pure magnesium, of course. Don't you even know the simplest things?

pca

Yep, a little one (50cm high, 60cm sparks).

And a 7 foot Van de Graaff generator (8 foot sparks), and a nitrogen laser, and a CO2 laser, and various plasma devices, and...

When I was 8 I rebuilt my fathers garden rotavator into a go-kart that the local cops told me to stop driving at 40 miles an hour on the sidewalk. They seemed to find the incident with the 80-foot purple mushroom cloud funny, though...

pca

The big Van de Graaff is something I always wanted to build- probably a dual (half to positive, the other to negative) with 3 foot spun aluminum terminals ($$$).

Your title of "God" seems well earned!

the local cops told me to stop driving at 40 miles an hour on the sidewalk.

As a teenager, I always found it thrilling to speed on my bike under my own power. Never got a ticket though .

Stu

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Teachers!

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I'll never forget the time my GCSE Chemistry teacher told me about time he nearly got fired on his first day. Apparently he was cleaning out a store cupboard with a colleague and came across a very old jar containing the biggest lump of sodium (i think it was sodium). Anyway, the other guy bet that it was so old it wouldn't be particularly reactive, so he filled an old wastepaper bin full of water, took it outside, dropped the sodium in and ran like hell. Anyway, about thirty seconds passed and nothing had happened, so he was walking back to the lab and was about to get his wallet out when he heard the most almighty bang. He turned round to see the bin had exploded, pinning a 1st year PE group against the wall with the force of the blast. Needless to say, he was one of my favourite teachers! .

He also came in very usefull when I was in the sixth form and had discovered home brewing. It turns out he has a post-graduate degree in Brewing. Cool eh?

My fifth-form teacher did something similar, only with about 5 pounds of white phosphorus. This was in the late 70s/early 80s, when the powers that be were cracking down on interesting lessons by banning all the stuff that was easy fun. For some reason he had amassed a really huge amount of WP, way more than was necessary for normal experimentation and demos in class.

He had to dispose of it, and being the sort of guy he was (quite a lot of fun, generally), he decided the best way was to go round the back of the chem block and build a small fire, then dump the WP on it and retire to a safe distance.

It worked, all right.

When the fire brigade finally turned up, the entire school campus was effectively hidden from enemy observation behind the largest cloud of white smoke you've ever seen. It could be seen for miles, and was so opaque visibility was about two feet. Took hours to dissipate.

All in all very funny, but the authorities weren't totally impressed.

pca

Yes I have built a Tesla coil. It used a neon sign transformer(10kv) to fire the primary side of the coil through a couple of homemade capacitors made out of 1 foot square glass plates and aluminum foil. The primary was about 20 turns as I remember. The secondary was a couple thousand turns around a wooden dowel. The secondary sat in the middle of the primary "donut" and was air gap. I think this thing produced a couple of million volts in the micro amp range. This was wired as an auto transformer. I built it when I was twelve. I remember my Mom taking me to the sign shop to buy the neon sign tranformer. I paid fifteen dollars for it. The rest I built from scratch. I could light fluorescent lamps from 5 feet away. If you drew a line with a pencil on a piece of paper and then held the end of the trace to the top of the coil while holding the other end of the trace you could see the graphite sparkle. You didn't want to run this for too long at a time though as it produced a lot of ozone.

You see? You see? Mix in 10-20 semi-sloshed empeggers, a dark night, a good barby, cold beer - well, I'm sure you can imagine the result

Hey, it wasn't ME letting off the cannon at 11PM in the middle of a residential area

pca

Ooops - yes, I conveniently managed to forget about that

By any chance are insurance premiums rather high for everybody around your area?

- Trevor

My 5th/6th year chemistry teacher used to be very useful - if he saw us doing something incorrectly he would always try and teach us how todo it properly.

So...trying to blow the doors off cupboards led to gas containment devices and fuses/igniters, a small experiment with sodium led to a demonstration of the reactive combination of potassium and sulphuric acid which demolished the safety glass which was supposed to protect the class.

I seem to remember him letting us play with Mercury as well - but this was the Eighties and they didn't seem to be too worried about us back then

Having relatives with easy access to industrial solvents and chemicals makes for good barbecue lighting, although I have yet to try the classic liquid oxygen method.

My high school chemistry teacher (who had a PhD in Biology -- go figure) would fill a balloon with hydrogen and light it with a match as some sort of experiment (I think she was just bored). This was because the principal made her stop mixing it with oxygen first. Apparently, he became disgusted when cracks started appearing in the windows.

My college chemistry professor decided to make thermite in a flowerpot one day, apparently a common classroom experiment. He turned out the lights for drama, I suppose, and all was going well, until a latecomer wandered into the classroom about two feet from the burning fuse and became confused at the darkness and all the people yelling at him to go away. I think he came within inches of having molten iron splattered on him.

In just having a quick browse around related topics, I like this idea for cooling your beers!

My God... How similar guys are across the planet... I too, built a million+ V Tesla, a jacobs ladder, a potato gun, burned all the skin off my left ring finger knuckle with white phosphorus, made shaped-charges out of M80's, sucked gasoline through a tube-style vacuum (very cool, btw). I have a 2 inch hole in my desk from burning phosphorus ribbons (in my bedroom, with a little loop in the ribbon - DUH). Burned a hole in the street at 2AM with thermite, and all sorts of idiotic, I can't believe I'm still alive, kinds of stupid ideas when I was younger. Haha...

BTW, the FCC get's rather picky about you setting off a large (or even relatively small) tesla coil for any amount of time as it REALLY interferes with all sorts of communications, as in TV, Cell phone, Radio, EMS and POLICE FREQUENCIES, etc etc etc.

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BTW, the FCC get's rather picky about you setting off a large (or even relatively small) tesla coil for any amount of time as it REALLY interferes with all sorts of communications, as in TV, Cell phone, Radio, EMS and POLICE FREQUENCIES, etc etc etc.

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It helps to employ heavy grounds dedicated to Tesla coil use, especially if you make a habit of running a beast like our 7.5+ KW unit. We also use 200 AMP EMI filters between each line going back to the electric grid. In our case we can actually watch TV while it is running out in the driveway at 7 - 8 KW. The noise is as much an issue as the interference. Ours measures ~120 dB from 20 feet away.

Ever shrunk quarters or other coinage with capacitive discharge? Haven't tried that but it certainly is tempting.

Stu

Your nonchalant description ("running ours out in the driveway while watching TV") makes me wonder...

What are tesla coils actually good for? Other than fun demonstrations of high voltage arcs and shrinking coins. Are they actually used for anything?

I can't believe that you never played C&C:Red Alert. I intend to mount on on my car to ward off potential thieves.

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Your nonchalant description ("running ours out in the driveway while watching TV") makes me wonder...

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If you are implying that we leave it running unattended, then you would be mistaken. That would result in an almost guaranteed lawsuit. Actually, what I meant was that while I am at the "controls" outside, other members of the family are still able to watch TV inside the house.

As far as what they are used for, well I guess there is no practical purpose. It's just very impressive to see in operation. The ozone, the buzzing, and big bolts of "lightning" are quite an experience. The inventor, Tesla used them to transmit electricity wirelessly, by tuning the coil to the point where it no longer made sparks. He could then power things in the vicinity of the coil just by grounding them. At least that's my take on it. It probably wasn't the safest concept and never really caught on.

Stu

> Ever shrunk quarters or other coinage with capacitive discharge? Haven't tried that but it certainly is tempting.

This is a fascinating thread. You people are insane...genius, but insane. I had no idea about some of this stuff. If anybody is wondering about coin-shrinking like I was, there is a good page here with pictures and coins for sale.

From PBS's Tesla: Master of Lightning:

Applications

If, as happened in practice, Tesla made an antenna of the high-voltage end of his secondary, it became a powerful radio transmitter. In fact, in the early decades of radio, most practicable radios utilized Tesla coils in their transmission antennas. Tesla himself used larger or smaller versions of his invention to investigate fluorescence, x-rays, radio, wireless power, biological effects, and even the electromagnetic nature of the earth and its atmosphere.

Today, high-voltage labs often operate such devices, and amateur enthusiasts around the world build smaller ones to create arcing, streaming electrical displays—it is not difficult to reach a quarter million volts. (One of the very first particle accelerator designs, by Rolf Wideroe in 1928, generated its high voltage in a Tesla coil.) The coil has become a commonplace in electronics, used to supply high voltage to the front of television picture tubes, in a form known as the flyback transformer.

Ah, a flyback transformer is a Tesla coil. Okay, now I'm clear on it.

The practical application, basically, is that it can generate a looooot of voltage.

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it can generate a looooot of voltage.

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FYI:
According to someone in the business making Tesla coils, it takes a 9 foot spark to achieve 1,000,000 volts. This figure was derived from measured quantities of x-rays generated by x-ray tubes coupled in some way to an operating Tesla coil. Similarly, a 5 foot spark represents 500,000 volts, indicating a nonlinear relationship between spark length and voltage output.

Stu

I use to build a ton of tesla coils. They work great for defending your base...

That's about right.... electricity takes about 10,000 volt to jump an inch through non-ionized air. 1MV / 10kV =100

So 100 inches for 1,000,000 Volts. = 8.33 feet

I was amazed this thread made it this long with a Command and Conquer stab.

Wasn't there one earlier?

I realize this thread is a month old now, but I saw this and thought it was pretty crazy:



More here

My God... How similar guys are across the planet... I too, built a million+ V Tesla, a jacobs ladder, a potato gun, burned all the skin off my left ring finger knuckle with white phosphorus, made shaped-charges out of M80's, sucked gasoline through a tube-style vacuum (very cool, btw). I have a 2 inch hole in my desk from burning phosphorus ribbons (in my bedroom, with a little loop in the ribbon - DUH). Burned a hole in the street at 2AM with thermite, and all sorts of idiotic, I can't believe I'm still alive, kinds of stupid ideas when I was younger. Haha...

man... why weren't you MY friend when i was a kid... all we did was pour gas or alcohol on our skateboards and ride them flaming down the street. Then there was the gunpowder we removed from all those shotgun shells.... but thermite!! Come on man! That's where the real fun is.

You may be glad you weren't my friend growing up. Some of them have scars too.