TESLA COIL

So where would I purchase two of those "bullet proof" caps. Sounds like that might be the best way to go. May not have time to find them and use them before his science fair is due (Feb 17th). But if he gets wimpy streamers, I'm sure he'll want to mess with this thing to get more bang for his buck.

He's also been very impressed with pictures of people somehow routing the lightening through their bodies and shooting bolts of lightening from their fingerstips. He's found pics on the internet where people have done that. I told him we had no way to test the current and no equipment to check if it would be safe (basically, keep your grubby hands off). It is my understanding that at the high voltage, it would kill him so fast he'd never know he'd been zapped. He's already been bitten by that transformer. It made an impression. He's been a lot more careful since that transformer bit him

Special protective gear and specific knowledge allows that. Even with the right stuff and the proper know-how, one tiny mistake and you're suddenly either very dead, or reduced to the mental capacity of an eggplant, the mobility of a rock, and breathing only with the help of a respirator.

He's found pics on the internet where people

Good concept until he knows a *WHOLE LOT* more than he currently (no pun intended, but since it's there...) does.

The frequency makes it safer - Note *SAFER*, not *SAFE* - to be messing with it, but the voltages and current levels involved are more than capable of killing if there's even a small mistake.

--
Don Bruder - dakidd@sonic.net - New Email policy in effect as of Feb. 21, 2004.
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Blackbeard wrote: (snip)

It will be going full blast in no more than .008 seconds ( a half line cycle) after it is powered on. You can try it in the house, but I would turn the computer and television off, first. Run it for a few seconds and turn it off, unplug it, short the capacitors out with a bit of high voltage wire and look everything over for signs of heating, arching or other problems. Work your way up to longer tests, but keep them under a minute and leave a few minutes cooling off between them because this thing will probably wipe out television and radio reception (including police, air traffic control and ambulance) for the neighborhood.

--
John Popelish

I posted those pics in alt.binaries.schematics.electronic titled Tesla Coil Science Fair Project

I wish I knew more about how to help the kid succeed. He's had a fairly tough tumble through school. He gets his attention by showing his ass. He's never received any recognition for doing good work. That's why I'm bugging you guys. If this thing works for him, this will be the first time in his life that he'll get to experience real pride up close and personal. I'm keeping my hands off this one and just sorta guiding him along the best I can. When he flips that switch and at the science fair, I think he's going to get their attention. It could be the start of this kid realizing that real praise feels pretty damn good vs. the snickering approval he gets from his classmates for making an ass out of himself.

At this point, I think we have the thing just about finished. He's wrapped 6 beer bottles with aluminum foil and filled them with salt water topped with oil. He re-did the spark gap with 2-mm of space between each piece of copper. I think all he has to do now is run a little wiring and turn it on.

Anything special I need to know? Can he turn this thing on inside the house or do we need to carry it out into the yard and use a drop cord? After he turns it on, what should we expect? Will it take a few minutes to fire up or will it start shooting sparks pretty quick? I'm pretty excited for the kid. I sure as hell hope he pulls it off.

thanks for all the assistance you guys have offered. It's helped fill >Blackbeard wrote:

What John said, but personally, I'd go with *OUTSIDE*, *AWAY* from any conductive "stuff" that isn't absolutely needed in the immediate vicinity. It might be a good idea to take a metal folding chair with any rubber/plastic on the legs removed, and place it nearby as a place to encourage any sparks to go should it fire up spectacularly on the first attempt, but *DON'T* get the hopes up real high at first. As Mark (I think it was) mentioned, tuning a coil can be tricky until you get a feel for the one you've got in front of you. It may take some substantial fiddling to get it tuned up the the point of doing more than buzzing and maybe glowing. But that's half the fun, sez Don :)

If it doesn't fire up at first, make sure to POWER DOWN AND SHORT THE CAP USING A HEAVY, VERY WELL INSULATED WIRE BEFORE DOING ANYTHING THAT EVEN RESEMBLES TRYING TO ADJUST IT! Personally, I'd suggest building a conveniently placed "Short-out pad" somewhere so you can just use a broom handle (Wooden, of course...) to mash a tab into contact with a button and positively drain the cap.

Trying to adjust one of these guys while it's powered up is a good recipe for a Darwin award if you don't know what you're doing, and do it exactly right. Even the folks that pass as experts (as much as anyone can be said to be an expert on Tesla coils, anyway) on these things won't mess with a "live" one without *VERY* specific circumstances being met, and the utmost caution. And with good reason! You truly are playing with "miniature lightning", and just like the full-sized version, it'll kill you deader than last week's chicken dinner before you can bat an eye if you don't deal with it as the potentially deadly item that it is.

--
Don Bruder - dakidd@sonic.net - New Email policy in effect as of Feb. 21, 2004.
Short form: I'm trashing EVERY E-mail that doesn't contain a password in the
subject unless it comes from a "whitelisted" (pre-approved by me) address.
See  for full details.

The OBITs can be obtained secondhand from oil fired boiler maintenance companies, scrapyards (free?) etc. The caps... Well, tell us the value you need and we/I can tell you what you need to buy. You need Pulse caps of anything over 600v each ideally and values of 0.1uF,

0.68uF, 0.47uF are good starters. I've used all of the above values, each rated at 1500V. Ten of these in series will give 15000V working voltage. Really, you need at least 15 in series to keep the cap safish from breaking down. However, all of these caps in series will make the value quite small and to bring the value up, we need to have lots of these "strings" in parallel. Therefore, working with some of the coils I've built using similar values and voltages, 45 - 60 caps (assuming you're using 1500V ones and not a lower value) would be a good ballpark figure you should budget for. At 50pence/cents per cap £23 - $23 to £30 - $30 for a reliable capacitor's not too bad a price for success. Of course, the bottle cap would be free.

Don't do the Electric Man stunt! Ever! A few people in the TCBOUK do this using sophisticated wire harnesses and power engineers chain mail suits/gloves. It's not all it seems and these days we have a better understanding of the "skin effect" and the human body. The skin effect is for metal conductors and not humans. You also have to take into account that the high frequency streamer can have a 50/60Hz component. Not to mention if there's a fault and you get a primary to secondary strike with a good high current 15000V straight up the secondary. Unless someone would like to put me right of course. Cheers. Mark.

I've run 2" coils indoors and bigger at Teslathons. However, the garage or other such place is best. Outside in the UK is generally a pain. Wind can reduce streamers, I know from experience. And damp? Always a worry. The other thing to remember, apart from keeping it away from any electrical appliance, is to use a good RF earth, not connected to the house wiring or plumbing. A good length of copper pipe in the damp earth is good. Also remember that moving a coil from location to location can change the tuning. Always have a tweak for best performance in 1/4 to 1/2 turns on the primary. Never adjust a coil when energised and always discharge the caps to RF earth via a wand and thick wire. Leave the wand attached to the primary or cap when the coil is being worked on. The caps will probably be electrically leaky and the charge will possibly bleed off quickly, but that is an unknown in the is case. Aklways manually discharge. Good luck. Mark H.

Not much electronics in this post. You've been warned.

From what you've written about this, I hope it does not become a disappointment or problem. So I offer this unsolicited advice:

Your son, or somebody on his behalf, should get this demonstration approved before the big day. If this has not been done, with safety procedures and signs in place that are satisfactory to whoever is in charge of the fair, there is a good chance that somebody in chage will freak out when the Tesla coil is run, and shut it down for the day. And I would not count on such people to be technically savvy enough to know what the real hazards are versus imagined hazards. That is why some early discussions are in order.

--
--Larry Brasfield
email: donotspam_larry_brasfield@hotmail.com
Above views may belong only to me.

Larry, Thanks for your thoughts regarding safety. Once we get "first light" we've already arranged a face-to-face meeting/demonstration with the electronics instructor at the community college. The guy has a PhD and lots and lots of experience. This fellow is our last stop before my son placed his project in the science fair. The school gave us a couple of extra days because they agree the this meeting will be important.

In addition, the instructor at the community college has already shown him how to read the wiring diagram. He's learned quite a bit from this one project. We're putting on our final touches today (I hope). Our first 1/2-dozen attempts failed to produce streamers. But I think we're close.

We went ahead and found a plastic storage box that houses all the high voltage stuff nicely and keep them out-of-reach from the curious. He's pretty jived by this whole thing. He's already talking about building his next coil and he hasn't finished his first.

The is another fellow who is an electrical engineer who has given him some help. He's also talked to a motor shop where they re-build electric components. So he's doing all the footwork. Can't figure out why it hasn't worked yet. But I think it's going to be pretty great when it does.

thanks mike