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Tesla Coil Presentation

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oucivileng

Mon Apr 13 2009, 11:47PM

Registered Member #1772 Joined: Tue Oct 21 2008, 05:23AM
Location: Athens, OH
Posts: 71

In a couple of weeks, I'm taking my SGTC to an event called "Young Engineers and Scientists Days" where I will be presenting to junior high and high school students, their teachers, and possibly parents. I've never used it anyplace but outdoors on my driveway so I'm a bit nervous about running it safely and responsibly in a classroom and in front of teenagers. Can anyone offer any advice? I'm worried that I'll forget some important detail. Here's my plan:

My coil will be set on a table, unless the ceiling is too low (don't want strikes to anything in the ceiling) for people to view easily.

For a secondary ground, I'll run jumper cables through the window to a copper pipe that I'll drive into the ground.
*could i drive another pipe into the ground nearby to connect the other jumper cable for a primary ground? otherwise I plan to just use mains.

I'll tape a square box on the floor around my coil where nobody is allowed to walk to avoid anyone touching it.

All computers or sensitive electronics in the room or on the same circuit will be unplugged

A few questions:
-Do I need to ask anyone with pacemakers to leave the room?
-Is there a possibility that nearby cell phones would be damaged? Should I ask that electronic devices be left in a closet or something nearby?
-When I first built my coil, it ran on much lower power. We used to hold a 4ft fluorescent bulb in a leather-gloved hand and let the electricity arc to it. I'm now at almost twice the power and have arcs around 30" more or less. Could I possibly do it again safely indoors? I'm not going to try it unless somebody can convince me beyond a reasonable doubt that it's safe.
-Do I need to bring a box of safety glasses for people in the front rows?

My coil specs:

Power: 2x 12kv/20ma nst's (=12kv/60ma)
protected by a safety gap and lowpass RC filter
Tank cap: 1 string of 8x cde940 rated at 3000v and 0.15uF ea (=24kv, 0.019uF)
Spark Gap: Five 1" OD copper pipe fittings quenched by a computer fan
Flat primary coil made from 1/4" copper tubing
Spark length: ~30" - I haven't checked recently. Could grow because I haven't really tuned it yet

Thanks!

Download

Tue Apr 14 2009, 12:15AM

Registered Member #561 Joined: Sat Mar 03 2007, 02:46AM
Location: Adelaide Australia
Posts: 230

It would be better to leave the computers/electronic plugged in but turned off as the earth pin and the metal case will protect the computers

Don't bother with safety goggles, what are they going to protect you from?

Ask people to turn of mobile phones, I've never had a problem with my phone near a Tesla coil

If you attach an earth wire to the opposite end of the tube you should be fine

I'm not sure about pacemakers, you should consult a doctor on that one

aonomus

Tue Apr 14 2009, 12:27AM

Registered Member #1497 Joined: Thu May 22 2008, 05:24AM
Location: Toronto, Ontario, Canada
Posts: 801

Things to watch out for:

- Biomedical devices
- Eager kids and ignorant soccer moms
==============================
- Do have a minimum safe distance well separated and clearly defined by a barrier of some sort, have several people helping you watch and on kill swithces, just in case.
- Do announce before and after that this stuff is very dangerous, will kill you if you make a mistake, that they should not try this at home. (Remember, both before *and* after).
- Do notify other booths that you will be a gigantic wideband RFI source, just incase someone has a sensitive engineering project, they know to be a little more careful when you are around.
- While safety goggles for yourself are not really required, dependon on how loud your coil is, you may want to consider hearing protection.
- Find a safe area that is as far away while still observable for anyone with biomedical devices (not just pacemakers, also includes hearing aids, insulin pumps, etc.). An elevated location like bleachers or a balcony may be a safer area.
- Do set up a proper RF ground, make sure that it won't get mucked up or damaged by other booths, and that no one could get shocked.

Proud Mary

Tue Apr 14 2009, 01:44PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

You are very right to think about Health and Safety issues, and how you will explain them. As a scientist, you may be quite sure the device is not nearly so dangerous as it looks, but to others the sparks will look like instant death, and they may take some persuading!

Renesis

Tue Apr 14 2009, 02:10PM

Registered Member #2028 Joined: Mon Mar 16 2009, 08:13PM
Location: Norway
Posts: 319

If you really want this to be safe, you can run it inside a RF-grounded faraday cage. I wont be as impressive as running it in the open, but definately safer. Adding a breakout-point will also make it easier to control the sparks.

I would check out the possibilities of setting it up outside. A TC looks way more impressive when it is run freely in the open, and not confined to a faraday cage. It would also reduce the risk of people getting ill by the ozone, and reduce the length of the ground wire.

I would not tell people that being struck would be instant death. I think people know that electricity hurts, exept children tho, be aware of them. Being told that this device is a lethal weapon they might see you as a mad scientist, and loose faith in you. Just put up a barrier of some kind to keep people at a safe distance, they wont cross it if you tell them not to. Remember that a crowd of people is like a heard of sheeps, Ã³ne big stupid mind.

A safetyfeature that should be mandatory on all tesla coil is a hand-held emergeny stop switch that you or another trusted person is in charge of. One of those big red buttons, you know. If a hyperactive kiddie makes a run for your coil you could quicly turn it off.

Still you should warn about pacemakes and such, and advice people to turn off their cell phones. If an old man dies, or a cell phone explodes, then at least they was warned.

Plasma Lover

Tue Apr 14 2009, 03:09PM

Registered Member #1911 Joined: Mon Jan 05 2009, 06:30PM
Location: Salem, Oregon, USA
Posts: 165

Renesis wrote ...

If an old man dies, or a cell phone explodes, then at least they was warned.

Well, that's pretty dang morbid. At this point you might as well say 'If an old man explodes, or a cell phone dies...'

I'm sure that nobody is going to die, and a broken cell phone can be replaced, however, if one is broken, then he wouldn't be liable if he had warned them of the possible danger.

It's true about a crowd of people being similar to a flock of sheep; people when saying 'Ooooh' and 'Ahhhh' tend to all want the same thing - more. I agree about the big red button idea. Make sure that people know that if they cross the tape, or what have you, that the coil will be immediately shut off. People don't seem to understand that there's a reason that you give warnings - that there's a real danger.

oucivileng

Thu Apr 16 2009, 12:42PM

Registered Member #1772 Joined: Tue Oct 21 2008, 05:23AM
Location: Athens, OH
Posts: 71

Thanks for everyone's great input. I really appreciate it!

Unfortunately, I am not able to do my presentation outdoors. I'll have a classroom to myself though and groups of students will come and go throughout the day. It'd probably be too bright out for them to get a good look at it anyways. I don't have time to build a faraday cage and my little mig welder is about 100 miles away right now so that's out of the question.

I have built a simple on/off safety switch out of an extension cord and one of those boxes that sits in the wall behind outlets and lightswitches.

Does anybody know of anything interesting that I can do besides turn the thing on and let them watch? I was planning on bringing some fluorescent bulbs for some students in the front to hold so they can see them light up, but that's all I can think of.

aonomus

Thu Apr 16 2009, 02:19PM

Registered Member #1497 Joined: Thu May 22 2008, 05:24AM
Location: Toronto, Ontario, Canada
Posts: 801

Find the caretaker, ask him for some 'dead' fluorescent tubes to light up (and then give them back so you don't have to deal with disposal).

Also if you have the power, melting a metal breakout point is fun...

Renesis

Thu Apr 16 2009, 04:12PM

Registered Member #2028 Joined: Mon Mar 16 2009, 08:13PM
Location: Norway
Posts: 319

Well, that's pretty dang morbid. At this point you might as well say 'If an old man explodes, or a cell phone dies...'

I lol'd and then felt really bad about it. I guess I am pretty dang morbid

Of course this was ment as a joke, and im sure you all got that. TC streamers dont turn old men into explosives

Make sure that people know that if they cross the tape, or what have you, that the coil will be immediately shut off. People don't seem to understand that there's a reason that you give warnings - that there's a real danger.

Good point, it seems whatever you say people dont listen unless you give them a good reason.

Does anybody know of anything interesting that I can do besides turn the thing on and let them watch? I was planning on bringing some fluorescent bulbs for some students in the front to hold so they can see them light up, but that's all I can think of.

If you can, start your coil at very low power, and then gradually increase it. People dont know how long sparks you can generate, so steadily increasing streamer lenght and noise level could kinda put them in a state of "Constant surprice"

Drawing sparks with an insulated rod with a grounded piece of metal on the end looks impressive, but i guess you could do that with the fluorescent tube?

I myself like the sight of a rsgtc starting with its spark gap motor shut off, and the coil coughs and aches until the spark gap starts revving up and the whole thing goes crazy. Like this:

However i am not shure wether this is harmful for the coil.

oucivileng

Fri Apr 17 2009, 01:34PM

Registered Member #1772 Joined: Tue Oct 21 2008, 05:23AM
Location: Athens, OH
Posts: 71

When I used to hold the fluorescent tube and draw an arc, it wasn't grounded. My friends and I got a kick out of it partly because it feels like ants are crawling through your skin. I'm guessing that it wasn't really a good idea so I'll probably just use the insulated rod with a grounded piece of metal from now on. Can I ground it to the same copper pipe I connect to my secondary?

I've seen pictures of different colored sparks (I think from TeslaDownUnder?) and I'm guessing he was using some salts or chemicals of some kind on his breakout points to do this. Does anybody know exactly what he was using? Also, can I easily purchase it or should I start begging some chemistry professors?

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