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Tesla's Candlestick: Wireless Electricity

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Tesla coil Instructables are not uncommon--I've written one myself--but in the following Instructable I'd like to not only describe building a simple upright coil, but also suggest some easy ways to assemble Tesla system components. Sometimes the parts of a Tesla coil system are harder to get than the coil itself. Then, at the end, I will demonstrate (in a small way) how Tesla coils can transmit electrical power through the air without wires.

The essence of this Instructable is simplicity rather than brute power or maximum efficiency. Because my coils are small, indoor models, I prefer to follow a modular method of building them. Most Tesla coils are unitized--everything packaged together in a single unit, just plug and play. I like to build in modular fashion so I can switch components around, try different coils, capacitors, or power supplies. Consequently my designs are clipped together with alligator clips and length of high voltage wire. If you
prefer the unitized approach, you can certainly adapt this design that way.

This Tesla coil system consists of these parts:

A high voltage (7,500 volts, 30 milliamps) AC transformer

A pressurized spark gap

A capacitor array

The coil itself, consisting of a primary and secondary coil on some kind of supporting
frame.

A "top load," or terminal

Wire to connect everything

Optional components you will want include a variable transformer (variac), and a small
hose-type vacuum cleaner.

Fluorescent light tubes, with stands

Each of these topics will covered on a separate page.
 
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twotower1 year ago
Hi Paul,

I built my own Tesla coil web page. Hope you like it.
http://www.twotowers.com/tesla/tessie_1_tesla_coil.html

Steffan
twotower1 year ago
Hi,

I love your "Instructable"! You use of suction to quench the spark gap was very helpful. I did not use your design, but rather modified the design I am using with a 120V computer fan, sucking (rather than blowing) air onto the spark gap. My spark output doubled! Thank You!

I completely disagree however about the necessity of a safety gap. At least with a larger NST. My TC is powered by a 15,000V 60mA NST. I fried my first NST after about 5 minutes of operation because of a voltage spike from the primary and secondary coil. I do recommend implementing a safety spark gap in your coil! The safety gap installs across the capacitor. Depending on how you assemble your MMC, this can be very easy to make and adjust.

I would be happy to upload a photo of my MMC capacitor if anyone wants to see it. I got the idea for my MMC from www.thegeekgroup.org. The Geek Group is another great resource for anyone wishing to build their first tesla coil. They have a series of videos that walks you through the whole process. They skip over a couple details in their videos that I believe are important, but it's mostly all there. I also used their idea for a secondary coil winding jig. With someone operating the variable speed drill motor at one end of the jig, I was able to wrap 33 inches of secondary coil in about 10 minutes.

Thanks again!
Mr. Apol (author)  twotower1 year ago
Thanks for writing. It doesn't matter which way the wind blows, as they say, as long as you quench the spark gap. It's a surprisingly easy way to boost the output of a coil.

There's nothing wrong with using a safety gap. I would under other circumstances. One reason I have never needed a safety gap is that I use fairly small NSTs--typically 7,500 V. They are current limited, and I always power them through GFI outlets via a variac or isolation transformer. Because I do almost all my experiments in my kitchen, I keep things small scale. I've never burned out a transformer or damaged anything except for toasting a few inappropriate capacitors. A 15KV/60mA NST is a bit of a brute to fire up inside the house.

Hardcore coilers prefer Cornell-Dubilier 942 series flash rated caps. They're rather expensive and not always easy to find. At the power levels I run, ceramic doorknob caps work fine. I also make my own dry Leyden jars--see my Instructable for Leyden Jar Battery for Tesla Coils. Those have never failed me.

Paul
I just started building the candle stick coil based on your instructable. I already have the secondary coil wound. We have that same paper towel dispenser with that same metal ball on top, so it looks like I have my top load. I wound the secondary coil using either 26 or 28 magnet wire onto 1 1/2" PVC SCH40 pipe. The 1 pound spool I used to wind the secondary had been laying around for 20 years and the label was long gone. As I am 52, my eyes are not as god as they used to be. Believe it or not, I wrapped the entire 1 foot coil going mostly by feel. It took about 1.5 hours. I calculated that my secondary has 1152 winds and 495 feet of wire. I will be using a 7500V NST. Any suggestions? Comments?
Peace
Mr. Apol (author)  sheydon1 year ago
Sounds good. I wrap my coils by hand too. What will you use for your primary winding? Do you have capacitors in mind? I recommend you run your final set of specs through TeslaMap to get an idea how much capacitance you will need.

Paul
sheydon1 year ago
Yes that is my MMC down there and it is constructed of the Cornell Dublier capacitors you mentioned.
IMG_0156.jpgIMG_0158.jpgIMG_0189.jpg
sheydon1 year ago
I did have problems when the fan was blowing instead of sucking?? Maybe I did something else too that increased the performance. Yes, my first tesla coil is a beast and it puts out 3.5 foot sparks. It is right in the middle of the living room. It certainly is a statement.
IMG_0212.jpg
MakerTony1 year ago
I built a small coil following this entry. Worked pretty well. The doorknob capacitors had trouble keeping up and burned out though. Might be something better out there.

I think the copper tube coil around the base would be better than insulated wire to enable tuning primary/secondary. I used at 15k NST. Never reached much corona from terminal, but I figure that was a tuning issue. Work in progress.

Watch a demo of my coil:
https://vimeo.com/63262916

Also article I wrote afterwards on Tesla:
http://pgavdestinations.wordpress.com/2013/04/22/nikola-tesla-a-world-without-wires/
Mr. Apol (author)  MakerTony1 year ago
Congratulations on your coil. As a rule of thumb, builders usually use caps with double the rating of their power source; in your case, 30KV when using a 15KV NST. I burnt out polypropylene radio capacitors like popcorn until I adhered to this rule.

Copper tubing be too thick for a small coil like this. It might be hard to get a good number of turns if you use a helical form. (That's why a lot of coilers make flat spiral primaries). You can of course cut tuning notches in the insulation of your primary. I prefer to vary the capacitance to achieve tuning. I also vary my top load to affect tuning too. Good luck!

Paul
Paul, good advice. Thank you!!!
Tony
Mr. Apol (author)  MakerTony1 year ago
Watching the video of your coil, I have a couple of questions. How is the coil grounded? Did you use an external ground, or did you run it as an autotransformer (did you connect the lower end of the secondary to the bottom end of the primary?) Did you use a program like TeslaMap to calculate how much capacitance to use with the configuration you built? My coil this size runs best with about 2nF, but I am using a much smaller NST--only 7500 volts/30 mA--and using the 15KV NST will definitely change your capacitance demands. Try upping the capacitance in stages about 1nF at a time and see what you get.

Paul
Paul,

Thank you for watching the video. What may not be apparent is that during the test, the corona discharge began to lose power to nil output. In the video you can see the capacitors begin to flame out (right-hand side of visual). This would seem to coincide diminished output from terminal. For this demo, the system was grounded as lower end of secondary to bottom end of primary. I did not use the TeslaMap, but certain I was under capacitance. I believe I was using 5 doorknob caps at 530 pf's each. Are doorknob caps a good choice for a small Tesla coil like this one? I had also tried salt water filled leyden jars, but discovered I had built them incorrectly as they seemed to not carry a charge. Surprised that you discourage the copper coil. I was thinking 1/4" copper tube turned 6x into a 30 deg angle (cross section). Not better? The assembly is actually in an exhibit at the moment so my tests are on hold for the moment.

BTW, have you seen the work that these guys are doing Teslatronix? http://www.teslatronix.com/

Thanks again Paul.

Tony
sciman11 year ago
VERY NICE! any interest in colab on a slayer exciter?
rimar20002 years ago
Brilliant work!
I haz agreed. ;-)
Mr. Apol (author)  rimar20002 years ago
Thanks! I don't do many, but I try to make them worthwhile.

Paul
OMG so awesome! Wish I had the materials to build.
Hi, I like your design (please forgive any spelling and grammar errors). I am looking to design a tesla coil and was hoping you could help with one with a 20 inch foot print, total height of 15 inches as well as encased in a conical shape. Only the primary and secondary coils would be encased, cap bank, spark gap, transformer would be placed in a separate area. also interested to know if several tesla coils can be daisy chained or would require separate power sources be required? one more question how would one connect a variable frequency generator output to the coil, if possible? any help would be appreciated, P.S. I know these are strange questions...just looking to expand the horizons.
Mr. Apol (author)  deirhntr_19991 year ago
I'm not sure I understand some of your questions . . . you want to encase the coil in housing, conical in shape, with the top terminal protruding?

It is not uncommon to add a third coil to a Tesla coil system. This is called a magnifyer, or extra coil. Tuned properly, it can vastly increase the output. There's no reason to actually series-connect full coils through; I don't believe that would work. As for variable frequency generators, do you mean a variable frequency oscillator, or some kind of audio equipment?
Higgs Boson2 years ago
Are doorknob caps the only ceramic capacitors you should use in an MCC, or could you also use high voltage ceramic disc with a high enough voltage rating put together for the right capacitance?
Mr. Apol (author)  Higgs Boson2 years ago
Disc caps will work (if you get the voltage rating and capacitance right) but they won't last as long as doorknobs; the intense pulsations of a Tesla coil circuit are hard on them. Pulse rated caps are best of all, but they can be pricey.

PBT
If you touch the electrical discharages will it kill you
Mr. Apol (author)  crazy-blender2 years ago
It wouldn't be good for you. This coil is being run as an auto-transformer, with the secondary ground being connected to the lower end of the primary. That's not something I would ever want to touch.

PBT
softairdude2 years ago
So, I'm currently using a bug zapper circuit to power a flyback transformer. My setup is power supply -> bug zapper -> capacitors -> spark gap -> flyback. My question is can i use this flyback to power a tesla coil, with modifications of course. Also, the capacitor on the bug zapper has .33uF capacitance and im wondering if thats way to much or if I should add more capacitors since i have them. Thanks for any help!
Mr. Apol (author)  softairdude2 years ago
It's funny, two comments about bug zappers in less than week; is there something going on? ;-)

I have no experience with DC coils, and that's what flyback transformers put out, high voltage DC. People do make battery powered Tesla coils, but it takes 12 volts at car battery levels to do it. I would check around for advice on DC coils. All my efforts have been made with household AC current.

Good luck,

Paul
harbor freight carries them for 3.99$ now. Cheap enough to be perfect for testing stuff out like this. There is just not enough documentation out there about DC coils. hmmm.
skier572 years ago
So i am looking to make something to be able to cheaply and easily light up house hold light bulbs wirelessly. Will this work? Or is there something better out there?
Mr. Apol (author)  skier572 years ago
No, this scheme to power lights and appliances wirelessly is not practical. A Tesla coil makes unacceptable amounts of toxic ozone and nitrogen oxide pollutants when run very long, it's punishingly loud, and the amount of RF energy radiating into the air over time would soon bring the FCC down on you. The massive interference would damage sensitive equipment--digital TVs, computers, cell phones, etc. Even if you could assiduously tune and screen your Tesla transformer for interference, it's just not an efficient way to distribute power. That's the real truth behind Tesla's downfall as an inventor. It's not that his ideas were wrong, or scientifically unachieveable--they just weren't practical.

PBT
I only need it on for like thirty seconds
Mr. Apol (author)  skier572 years ago
Well, you can do that--but it only works on fluorescent bulbs, not incandescent types.

Paul
OzoneLab2 years ago
Mr. Apol
I can't remember where but I remember you offering a high voltage soviet era capacitor for sale- do you have a way of contacting me about this?
thanks, OzL
Mr. Apol (author)  OzoneLab2 years ago
I did, a while back on the TCML. It's already gone though. Sorry.

Paul
~KnexBuild~2 years ago
Would a 9,000V 30mA transformer work instead of a 7,500V 30mA transformer?
Mr. Apol (author)  ~KnexBuild~2 years ago
Absolutely. You'll have to calculate what sort of capacitance you'll need, but in general, more volts means bigger sparks and more power output. Be sure your transformer does not have GFI (ground fault interrupt).

PBT
Ok, thanks for the info. How do I calculate the needed capacitance?
Mr. Apol (author)  ~KnexBuild~2 years ago
The simplest way to calculate your needs is to use a program like TeslaMap or JavaTC. They work like spreadsheets; you input the details of your coil and they will compute how much capacitance you need to achieve maximum resonance.

TeslaMap: http://www.teslamap.com/download.html

JavaTC: http://www.classictesla.com/java/javatc.html

Paul
genious boy2 years ago
i have make a vaccum cleaner out of a cola bottle,powered by 12v adaptor.can u gide me how to upload this instrucable for winning a prize
sourcand452 years ago
How much does this cost to build?
Mr. Apol (author)  sourcand452 years ago
Let's see: the cardboard secondary tube was free; various PVC parts ran about $5 in all. 24 gauge wire, about $5, 10 gauge was 49 cents a foot (about $3.50). Salvaged microwave oven wire, free. Topload sphere came from a paper towel holder that cost $14. Parts to make the spark gap, $4. Ceramic capacitors, used, off eBay set me back $1 each ($4). NST, used, off eBay, $16 including shipping.

Total for Tesla coil system, $51.50. This does not include the fluorescent tubes, etc.

Another benefit of building the coil modular fashion is that the components are easily reusable in other projects.

Paul
Thank you :)
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