How to Build a Spark Gap Tesla Coil (SGTC)

Shoot foot-long bolts of lighting through the air, light fluorescent tubes without wires, and power yourother high voltage experiments with the aid of this tabletop-sized Tesla coil! Once the parts have arrived,it comes together in about a weekend, and for less than $200 even for those without a big bin of spareparts. I built this coil for fun over a few weekends during 10th grade, juggling eigenvalue problems andEuropean history for drilling and soldering high voltage components.

The key to this coil's performance on such a tight budget is that all of its components are designed towork well together. Using some basic concepts from AC circuit design, the components are matched toperform well without requiring massive amounts of power. Some "coilers" use microwave oventransformers to pump kilowatts of energy through poorly matched circuits, resulting in large losses andmediocre performance. This instructable will show you how to avoid making such mistakes and how toproperly design a spark gap Tesla coil.

UPDATE: This Tesla coil is now on sale on eBay for a starting bid of $99.99, less than the cost of the

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About This Instructable

Posted:Jul 10, 2011

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My name is Daniel Kramnik - I likebuilding Tesla coils, quadrotors, and robots!

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How To Build A Spark Gap Tesla Coil (SGTC) by Xellers (/member/Xellers/)

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How To Build A Spark Gap Tesla Coil (SGTC) http://www.instructables.com/id/How-To-Build-A-Spark-Gap-Tesla-Co...

1 of 27 09-04-2013 19:46

materials! http://www.ebay.com/itm/250-000-Volt-TESLA-COIL-Assembled-2-Foot-Tall-8-12-Sparks-/180826521311?pt=LH_DefaultDomain_0&hash=item2a1a19bedf (http://www.ebay.com/itm/250-000-Volt-TESLA-COIL-Assembled-2-Foot-Tall-8-12-Sparks-/180826521311?pt=LH_DefaultDomain_0&hash=item2a1a19bedf)

For contest entry details on this instructable, see step 10.

UPDATE: New diagrams for primary capacitor, primary coil, and spark gap construction have beenadded. Click the top left information icon to view them in full size.

Featured on Hacked Gadgets (http://hackedgadgets.com/2011/09/04/diy-spark-gap-tesla-coil/)!

Please don't forget to rate!

(I named it the "Valentine's Day Tesla Coil" in this video because I finished it over Valentine's Dayweekend 2011)

To read more about this project, visit my website: http://xellers.wordpress.com/tesla-coils/sgtc-ii/(http://xellers.wordpress.com/tesla-coils/sgtc-ii/)

Step 1: Theory and Warnings

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2 of 27 09-04-2013 19:46

Although I don't want to spend too much time talking about exactly how a Tesla Coil works, I think that arudimentary description is worthwhile given the amount of misinformation that exists on Instructablesand elsewhere on the web.

Essentially, a Tesla Coil is a type of alternating current transformer that operates almost like any other(transformers are found in many electrical and electronic devices and are used to step up or step downthe voltage of an alternating current signal). However, it relies on the principle of electrical resonance inorder to massively increase the voltage of the alternating current signal.

One comment misconception is that the primary circuit (capacitor and inductor) "amplify" the signal fromthe high voltage transformer and that the ratio of turns between the primary and secondary coil is thenused to create a high voltage. However, this is not quite the case.

During each alternating current half-cycle, the transformer charges the primary capacitor until thevoltage across it exceeds the breakdown voltage of the spark gap. At this point, the capacitor andprimary coil are connected and momentarily form a series LC circuit. Because the capacitor has aninitial charge from the transformer, the LC circuit will oscillate much like a stretched spring will moveback and forth once it is released. In fact, the differential equation describing a stretched spring movingback and forth with friction is virtually identical to the one that describes an LC circuit with an initialcharge on the capacitor oscillating with stray resistance in the wires of the circuit.

These oscillations can exhibit three different types of forms: overdamped, critically damped, andunderdamped (second image). In the overdamped condition (high damping factor, ζ), the current decayswithout crossing zero, while in the underdamped condition (low damping factor), it crosses zero manytimes and oscillates before decaying. This last condition is the one we hope to achieve in our coil.

Once the circuit is oscillating, the rising and falling magnetic field around the primary coil will inducecurrent into the secondary coil. The goal is to maximize energy transfer between the primary andsecondary coil and minimize energy lost to heating as a result of stray resistance.

The secondary circuit also acts as an RLC network. Its impedance, or resistance to an alternatingcurrent, will change as a function of the frequency that the primary circuit oscillates at. The third pictureshows this relationship. If the frequency of the primary circuit matches that of the secondary circuit, thenthe amplitude of the secondary voltage will increase dramatically because the secondary impedance willbe very low. Once the oscillations in the primary circuit have decayed, the transformer will switch polarityand recharge the capacitor, causing the cycle to repeat. This is similar to what happens when you try toforce a sping to move back and forth; if you're not at the correct frequency, then it resists your push, butif you do manage to hit the right frequency, then even a small application of force can quickly increasethe amplitude of its oscillations.

If you want a more mathematically rigorous explanation, be sure to take a look at this paper:http://tayloredge.com/reference/Machines/TeslaCoil.pdf (http://tayloredge.com/reference/Machines/TeslaCoil.pdf)There's actually quite a bit more going on than I made it sound like, so consider taking alook even if you're going to skip the mathematics.

SAFETY WARNINGS (READ THESE):

That said, I want to give a few warnings to anyone who is considering this project. Tesla coils and otherhigh voltage devices are extremely dangerous in the wrong hands and can easily injure or kill anyonewho does not practice proper high voltage safety. I am not responsible for any accidents that may occuras a result of these instructions.

I also do not guarantee that your coil will work or that you will be satisfied with the results. Only attemptthis project if you are willing to face failure on your first attempt and don't cut corners - if that capacitorhas to be rated to a certain voltage or that wire has to be enameled, don't try to get an inferior productfor less. It's better to wait and save up for the higher quality part than to end up with a pile of cheap,burnt out components.

Be sure to read the entire instructable and completely understand what you will have to do beforeattempting this project!

Step 2: Gather Materials

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3 of 27 09-04-2013 19:46

The materials that you will need for this project should cost you no more than $200 and you can easilyspend less than $100 if you invest some time into searching for good deals. Here is how I distributed mymoney:

Electrical Parts:

$35 - (1) 9kV 30mA Neon Sign Transformer$35 - (100) 1.5kV 0.01uF Polypropylene Film/Foil Capacitors (the type of capacitor, in addition to it's

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4 of 27 09-04-2013 19:46

value, is critical)$5 - (100) 10M 1/2W Resistors (I actually bought 200, but didn't use half of them)$20 - 680 Feet of 23 AWG Enameled Wire

Hardware Parts:

$15 - Wood from Home Depot - I cut a large piece into (2) 13" x 16" x 3/4" pieces for the base$3 - 20" Long 3.5" Diameter PVC pipe for the secondary coil former$2 - (1) 2' long 1" diameter PVC pipe for the primary coil former$2 - (8) Nuts and bolts to hold the primary formers down - I used #8-32 x 1 - 1/4" Machine Screws$0 - Primary Coil Wire - I used some relatively thick insulated wire I found at a recycling center, onecould easily use flexible copper tubing or thick speaker wire for this purpose$0 - (1) 1' by 1' piece of acrylic - I had some extra pieces from a laser project, but any moderately-sizedsheet of plastic will do$0 - (2) Metal objects to form a spark gap - I used a pair thick nuts and bolts for this$3 - (1) 6" Styrofoam ball for the topload former$0 - Aluminum foil to cover the topload$0 - Spray-on Polyurethane Varnish or Shellac

TOTAL COST: $120

Coil Specs.

Power Supply: 9kV 30mA NST (270W)Primary Capacitor: 10nF 15kV MMCSpark Gap: Single static gap made from a bolt and a washerPrimary Coil: Flat spiral coil made from 9 turns of 10AWG wire tapped every quarter turn with 0.25"spacingSecondary Coil: 3.5" by 18" winding of 23AWG enameled wireTopload: 6" Styrofoam sphere covered in aluminum foilMax. Spark Length: 14" to ground, 11" to air

Step 3: Build the Primary Capacitor

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5 of 27 09-04-2013 19:46

Because most neon sign transformers do not have the same output voltage/current ratings, eachtransformer transfers different amounts of energy into the primary capacitor during each operating cycle.Since we want the capacitor to charge and discharge completely during each cycle, this implies that itmust be "matched" to the transformer's output characteristics in order to maximize the coil'sperformance.

To do this, we set the output impedance of the transformer equal to the reactance of the capacitor:

X = 1/(2πfC)

X = E/I

Therefore, if X = X , then

C = 1/(2πfX )where f is the frequency that the capacitor is being charged at (the mains frequency); this isstandardized to 60Hz in the United States.

For my particular transformer, a 9kV 30mA NST, the optimal capacitor value was calculated as follows:

C = 1/(2π*60Hz*9000V/0.030A) = 8.8nF

Here is a convenient online calculator that automates this procedure: http://deepfriedneon.com/tesla_frame6.html (http://deepfriedneon.com/tesla_frame6.html) (select "Capacitor to TransformerMatch")

In reality, however, it is undesirable to use a perfectly matched capacitor because if the spark gap failsto fire, then the "resonant rise" of voltage across the capacitor and transformer will almost certainly leadto a transformer breakdown. You can read more about this here: http://www.richieburnett.co.uk/resonant.html (http://www.richieburnett.co.uk/resonant.html)

I chose to use a slightly larger than resonant capacitor value of 10nF in my coil. It's better to have someextra capacitance than it is to have a bit too little because this way, some of the energy storage capacityof the capacitor is wasted, while in the latter case, some of the energy from the transformer is wasted.

Next, in order to calculate the necessary voltage rating of the primary capacitor, we find the peak ACvoltage of the transformer. Because V = 1.4 * V , the peak voltage for my transformer is 1.4 *9000V = 12600V. Since we don't want to run the capacitor right at its maximum allowed voltage, weusually add several kilovolts of headroom. Ideally, the capacitor should be rated to twice the RMSvoltage of the transformer. I decided to build a capacitor rated for 15kV due to financial considerations.With my 10nF 1.5kV capacitors, this works out to 10 strings of 10 series capacitors, giving me exactly10nF at 15kV, perfect! (DeepFriedNeon also has an MMC calculator that you can use to find the bestprimary capacitor configuration)

Finally, each capacitor should have a 10 megaohm resistor in parallel with it so that the bank does notstay charged once the coil is turned off.

Physical construction of the capacitor bank is not very critical. I used a square of plexiglass that I drilledwith 200 holes to mount the capacitors and resistors (see first picture). However, to make things easier, Idrew a diagram (image 2) that explains how I drilled the board and mounted the components. View thefull size image for better readability.

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6 of 27 09-04-2013 19:46

Step 4: Wind the Primary Coil

Together with the primary capacitor, the primary coil makes up the LC resonator that drives thesecondary coil. Because we want to transfer the energy in the primary circuit to the secondary circuitover several RF cycles, allowing the primary circuit to resonate, the coupling between the two coils isrelatively low. This is why many spark gap coil primary coils are flat wound (this is not the case in solidstate coils where the goal is to switch as much energy into the secondary circuit as possible with eachcycle).

At this stage, you can use DeepFriedNeon's LC frequency and secondary coil calculators in order to finda combination that suits your components or you can use ScanTesla in order to "scan" for theconfiguration that will maximize the coil's perormance, however, I will not cover these approaches here. Ithink that I have found a primary/secondary combination that works reasonably well and if this is yourfirst coil, I would advise you to follow what I did before you experiment on your own.

For my primary coil, I used a flat spiral made of 9 turns of thick stranded wire with 0.25" spacing tappedevery quarter turn for tuning. If you can afford to use a flexible copper tube, then I recommend you do sobecause it is easier to tune and work with than insulated wire.

I used 4 supports made of 1" by 6" PVC pipe bolted down to the wooden base. Here is how I markedand drilled them to support the primary coil: http://www.loneoceans.com/labs/teslacoil2/sep9_pridesign.gif (http://www.loneoceans.com/labs/teslacoil2/sep9_pridesign.gif) (with 5 tubes insteadof 7 and 0.25" spacing instead of 0.5")

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7 of 27 09-04-2013 19:46

While you should wind the primary coil as neatly as you can, my coil worked fine even though thestranded wire didn't form a perfect spiral. See picture 5 for a diagram:

Step 5: Build the Spark Gap

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8 of 27 09-04-2013 19:46

While a well-quenched multiple segment spark gap is desirable for this type of coil, two bolts held abouthalf an inch apart will do just fine at first. My spark gap use one L bracket and two nuts on one side tosecure a bolt that can be used to adjust the distance of the gap and another L bracket with a nut andbolt to secure a washer on the other side that can be rotated "reset" the gap after it corrodes with use.This is particularly useful in long demonstrations where the corrosion on the bolt and washer caneventually reduce the performance of the coil. See pictures 3 and 4 for building instructions for this typeof spark gap.

Another popular type of gap known as an "RQ mutliple gap" uses several copper tubes bolted in a circleinside of a PVC pipe with a fan at one end for cooling and quenching. It can be adjusted by tapping thegap after different numbers of tubes to alter the total arc distance. This is the type of gap that I hope toconstruct sometime in the future. Here is a helpful diagram: http://www.capturedlightning.org/hot-streamer/stk/tc/cylndr.gif (http://www.capturedlightning.org/hot-streamer/stk/tc/cylndr.gif)

Pro Tip: Don't stare at the spark gap during operation. It produces dangerous amounts of ultraviolet lightthat can damage your eyes. Seeing as there is no need to operate this coil for more than a few minutesat a time, it won't need to be covered, but it can still be dangerous if you look directly at it.

Step 6: Wind the Secondary Coil

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9 of 27 09-04-2013 19:46

Winding the secondary coil is probably the most tedious part of this exercise, however, the 23 AWGsecondary wire that I used in the coil is thick enough that it should not cross over windings without younoticing or rip if pulled too hard. All you have to do to wind the secondary coil is tape the wire downabout an inch from one end of the 3.5" diameter PVC tube and spin the tube so that you get an evenand tight winding from one end of the tube to the other (see second picture).

If you are using 680 ft. of wire, a standard size you can buy on eBay, then all you have to do is keepwinding until it runs out. This should give you a winding with about 18 inches of length. Cut the tubeabout 1 inch above the end of the secondary winding and leave several inches of wire at each end tomake connections.

Once the wire is wound and taped at each end, apply a few heavy layers of spray-on polyurethanevarnish or shellac to make sure it doesn't break or unwind.

Important: some websites may tell you to drill holes at each end of the secondary to thread the wirethrough so that it is more secure. While this may work for a smaller coil with a long secondary winding, itis generally considered bad practice as it leads to arcing inside of the PVC tube in more powerful coilsand will cause permanent damage (ie. burns and carbon trails inside of the tube) that will render thesecondary unusable. Varnish and a piece of masking tape should easily be enough to keep thesecondary coil from unwinding.

Also, recently, I have found that I am getting roughly the same performance from a 14" winding of28AWG wire on 2.5" PVC pipe as from my previous 18" winding of 23AWG wire on 3.5" pipe, but it looksmore impressive because the sparks are larger with respect to the secondary coil. In fact, because ituses less materials, you might want to start with the smaller secondary if your budget is limited. Iencourage you to experiment!

Fatter, shorter secondaries tend to work better to a certain extent, but if they are too short, thenproblems with primary - secondary arcing can arise. One common error that Tesla coil builders oftenmake is to wind a very long and thin secondary coil. The misconception that these secondaries wouldgive better results was started in the early to mid-20th century by hobbyist magazines that featureddiagrams like this one: http://amasci.com/graphics/tcoil1.gif (http://amasci.com/graphics/tcoil1.gif).

Step 7: Make the Topload

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10 of 27 09-04-2013 19:46

The topload is easily the simplest part of this project. I used a 6" Styrofoam ball from A.C. Moorecovered in aluminum foil with a piece of wire taped to the top for a breakout point. It isn't pretty, but itworks well. Alternately, you could spend several dozen dollars on a machined aluminum toroid on eBay.This should increase the performance significantly (if you buy the right size), but I haven't had thechange to try it out due to financial limitations. A small volleyball or soccer ball wrapped in foil also worksif you can't find any Styrofoam.

An alternate method of making simple toploads is to use conductive spray paint to coat a sphericalobject like a lightbulb. I have not tried this yet, but it should give better results than anything you canmake with aluminum foil. Here is an example of this approach: http://www.instructables.com/id/Van-De-Graaff-Electrostatic-High-Voltage-Generator/ (http://www.instructables.com/id/Van-De-Graaff-Electrostatic-High-Voltage-Generator/)

Remember, the Tesla coil I describe is relatively small and adding a huge topload made of aluminumducting will not increase the spark length. The key is to get just the right sized topload, large enough thatthere are no problems with multiple breakout or coronal discharges at the top of the secondary windingsand small enough that it doesn't decrease performance.

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11 of 27 09-04-2013 19:46

Picture 1 is of the 6" sphere sitting on top of the 3.5" secondary and picture 2 is of the same toploadsitting on the 2.5" secondary.

Step 8: Make Connections

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12 of 27 09-04-2013 19:46

At this point, all of the electrical components have been assembled and all that remains is to connectthem together and mount them on a base. I chose to use two 1' by 1' wooden boards nutted and boltedtogether with 0.25" nuts and bolts to make a small box to screw or nut/bolt everything into. Have plentyof nuts and bolts, they're cheap and they come in handy when you're assembling the base!

Once the parts are mounted, use 10AWG or thicker insulated wire to connect everything correctly (seeschematic). If this seems too confusing, then perhaps you should try a simpler electronic project first tofamiliarize yourself with reading and following electrical schematics. Make sure you keep theconnections as short and tight as you can to minimize stray inductance and resistance that can hurt yourcoil's performance. Specialized high voltage wiring is not necessary unless you plan on sticking yourfingers into the coil while its operating (bad idea!).

While you can use alligator clips to test everything before you mount it, be aware that the performanceof the coil will decrease and you risk destroying your clips due to overheating. I melted multiple alligatorclips this way - they often fail where the wire is soldered to the clip and can usually be fixed byresoldering the two together.

If you are building a significantly more powerful Tesla coil than I did, it may not be the best idea to usewood in your design. Wood is not an insulator at high voltages and on a humid day, you might find thatyour primary circuit will arc through the wood and start a fire. At the very least, do not mount anyelectrical components directly onto the wooden base, use plexiglass, acrylic, or plastic or ceramicinsulators wherever possible. This is not a concern unless you are pumping a kilowatt or more into yourcoil. (A 9kV 30mA NST only draws about 270W).

Step 9: Fire it Up!



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13 of 27 09-04-2013 19:46

Once all of the connections have been made, you're almost ready to go. Before you start, made surethat you have a good RF ground for your secondary coil. At first, if you are building a relatively smallcoil, then the earth ground on most electrical sockets will do. If you live in an old house, the earth groundin the socket may only be connected to the electrical box in the wall and not actually to the ground.Make sure you know before you run your coil. To run larger coils, you will need to use a grounding rodhammered several feet into the earth. Also, be sure to run your coil outside or in a well-ventilatedenvironment as it will product dangerous amounts of ozone that can quickly cause lung irritation.

Remember that the first time you turn the coil on, chances are that it will be completely out of tune andwill not make large sparks. Be patient and slowly adjust the primary tap until the sparks reach theirmaximum length. The "sweet spot" in my coil is only about half a turn wide and it took about half an hourof tuning to find. Be patient!

Once the coil is in tune, it will also be necessary to adjust the spark gap. While you are tuning, it shouldbe set to 1/8" or 1/4" separation (if you are using a single gap). Then, once the coil is in tune, slowlyincrease the length of the gap. The goal is to keep it as wide as possible, thus allowing more energy tobe stored in the capacitor before the gap fires, while still firing regularly at 120Hz. If the gap doesn't fireregularly or doesn't fire at all, then there is either too much corrosion or the separation is too wide, orboth.

If you are using a very smooth polished aluminum toroid or sphere as your topload, then the coil mightbreak out on its own at one point and no breakout point will be required. However, if you are using atopload made with aluminum foil, then the coil will probably break out in multiple places, reducing theoverall spark length. To combat this problem, you can tape a short piece of wire to the top or side of thetopload so that the output is concentrated there.

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14 of 27 09-04-2013 19:46

I have found that if the breakout point is too short, then there will still be multiple sparks across thetopload, so make sure that it's a few inches long and very sharp at the end. The breakout pointconcentrates the sparks to one point because the sharp end of the wire creates a larger electric fieldgradient and promotes breakout there more than anywhere else on the topload.

If you still have problems with multiple breakouts or coronal discharges at the top of the secondarywindings, then you need a larger topload. On the other hands, if you think your sparks are too small,then try using a smaller one. The key is to experiment.

Good luck and have fun!

To read more about this project, visit my website: http://xellers.wordpress.com/tesla-coils/sgtc-ii/(http://xellers.wordpress.com/tesla-coils/sgtc-ii/)

This is what first light looked like for me:

Step 10: Contest Entries



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15 of 27 09-04-2013 19:46

Don't worry, this is not a construction step! This is where I will justify why I have entered this instructableinto various contests:

1. Space Contest

If bolts of lightning shooting into the air aren't already sci-fi enough, see picture 1!

Result: Winner!

2. USB Contest

See picture 2 to better understand how my Tesla coil "interfaces" with various devices via USB.

Result: Finalist!

3. 2nd Annual Krylon Contest

(/files/deriv/FFJ/SXHB/GPVEVV3F/FFJSXHBGPVEVV3F.LARGE.jpg)

(/files/deriv/FBJ/5TI2/GPVEVRDJ/FBJ5TI2GPVEVRDJ.LARGE.jpg)



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Post Comment

(/member/sciencetor2/)

Apr 20, 2012. 7:48 AM Reply (C112Y7WH18FJVEW)

(/member/The+MadScientist/)

Mar 23, 2013. 11:02 PM Reply (C88NALBHELXCMHC)

8(/member/agod/)

Aug 15, 2012. 2:14 PM Reply (CBKO3A0H5TU8LU5)


Aug 19, 2012. 8:13 PM Reply (CLTQ4CMH5EDV7JO)


Apr 29, 2012. 7:47 PM Reply (CBTCPN4H1JUGT44)

Apart from the secondary coils being painted with spray-on varnish, the background in the space contestphoto is a piece of cardboard spray-painted black to make the sparks more visible - I use it all the timein my Tesla coil photography.

Result: None.

1-40 of107

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sciencetor2 (/member/sciencetor2/) says:

found these capacitors on ebay, they're from a supplier so they should be around for a while.

http://www.ebay.com/itm/380266725123?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649#ht_1854wt_811

all the info you would need isn't there, but with a bit of research done after i recieved my order, theyappear to be the crimped version of these

http://www.panasonic.com/industrial/includes/pdf/ECW-H_C_New_Product_Introduction_Sheet.pdf

which should(probably) be suited for coil use, though the specs are slightly different from theinstructable, so you would need to change your MMC configuration. i will probably go with a 12x8setup(12 per string, 8 strings in paralell) which yields a capacitance of 0.01uF and a voltage rating of19200v(19.2kV). i will let you know how it goes when i finish my coil.

The MadScientist (/member/The+MadScientist/) says:

Hi. I am just wondering whetherthese capacitors(http://www.ebay.com.au/itm/100pcs-CBB-Metallized-Film-Capacitor-0-022uF-223J-2KV-/290562041937?pt=AU_B_I_Electrical_Test_Equipment&hash=item43a6d8e851#ht_762wt_1163would also work?

Cheers

agod (/member/agod/) says:

could you give a link for the resistors you used. Thanks.


yep :) here you go! happy coiling!

http://www.ebay.com/itm/10-Meg-Ohm-Bleed-Resistors-Tesla-Coil-Capacitors-/360313237049?pt=LH_DefaultDomain_0&hash=item53e457ae39


ok, just finished my tesla coil and ranit, these capacitors work great!highly reccomend them for theirprice, amount, and continuous



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17 of 27 09-04-2013 19:46

(/member/intellectualbean/)

Dec 26, 2012. 4:46 PM Reply (CSYCCF7HAWSHS9H)

10(/member/Xellers/)

Dec 26, 2012. 6:20 PM Reply (CR8TALIHAWSLK7B)

(/member/james34602/)

Oct 29, 2012. 7:40 AM Reply (CNPM1GFH8CVGPL6)


Oct 29, 2012. 11:23 AM Reply (CK8TU2NH8RVD0T3)

6(/member/seraine/)

Oct 16, 2012. 6:12 PM Reply (C95UQ21H8CVHUA6)


Oct 16, 2012. 6:19 PM Reply (C3ONFNJH8CVFOY6)

6(/member/seraine/)

Oct 16, 2012. 6:25 PM Reply (C2G52XWH8CVHUAW)

8(/member/agod/)

Aug 1, 2012. 2:21 AM Reply (C493VLSH58P2W85)


Aug 12, 2012. 4:51 PM Reply (CJ7JUPLH5F2ZQG8)

availability.

intellectualbean (/member/intellectualbean/) says:

(removed by author or community request)

Xellers (/member/Xellers/) (author) says:

Did your spark gap ever firecorrectly with the capacitor bank andNST connected? If the NST is justarcing over the gap and nothing elseis happening, then a connection tothe capacitor bank is broken.

james34602 (/member/james34602/) says:

How can I build a quiet spark gapAlways it was loud


Build a solid state or vacuum tubecoil :P

seraine (/member/seraine/) says:

I need 17 0.15 uf capacitors, and these appear to be perfect for my Tesla Coil

http://www.digikey.com/product-detail/en/B32023A3154M/495-3802-ND/1648119

Can a MMC use polypropylene metallized film capacitors?


Yes - those are precisely the kind ofcap you'd want to use (unless youcan afford CDEs).

Good luck!

seraine (/member/seraine/) says:

Thanks for the speedy reply!


Would a circuit board like a pcb or breadboard work to hold the capacitor bank?


i doubt it, as a breadboard would notprovide enough insulation to containsuch high voltages unless youmodified it by removing un-neededrows, and then it may heat up, a pcbcould work if it was custom for yourbank, a pre punched prototypingboard might arc, but i dont know


Ä° will be running my tesla coil in a science competition indoors ( in a basketball court) where there is



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18 of 27 09-04-2013 19:46

Aug 1, 2012. 8:27 AM Reply (C9WBLNEH58P2X7U)

8(/member/agod/)


Aug 12, 2012. 4:45 PM Reply (CJ96D4QH5F2ZQG3)

8(/member/agod/)

Jul 13, 2012. 8:41 AM Reply (CUSC5ECH4AGKB4L)


Jul 13, 2012. 9:06 AM Reply (C38XTYQH4AG59SI)


May 6, 2012. 10:21 PM Reply (C7HWTJDH1WHV8HV)

no access to a place to puta large metal spike in theground so i was wonderingif it would be ok to groundit to the ground in anoutlet. Ä°t is exactly thesame as yours execpt mysecondary is 4 inchs wideand i am using 30awgwire. Thanks.


well, provided the electrical systemis properly grounded, you CAN, idid... but be sure to filter everythingwell with a specialized RF filter, asby grounding it to the outlet you cancreate potentially damaging RFinterference that can damagesensitive things like flat screen tvsand computers and such if leftunfiltered.


my transformer is the same as yours but 60ma. what will i need to change in the cappacitor bank?THanks


See the step on building the capacitor- I discuss how a value is selectedthere. You'll need to run thecalculations yourself. Good luck!


built a working Tesla Coil from this instructable :D made a few modifications due tonecessity/improvement/budget/availability, but it works great! (still a bit out of tune though since I havebeen crazy busy) here is a video of it running

,

and pictures below.



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(/files/deriv/FDL/N12Q/H1JUINWM



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(/files/deriv/FC0/AE1X/H1KHA3HN



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22 of 27 09-04-2013 19:46


May 6, 2012. 10:40 PM Reply (C0I40URH1WHV8KJ)

/FC0AE1XH1KHA3HN.LARGE.jpg) (/files/deriv/FDY/NN77/H1JUINWO/FDYNN77H1JUINWO.LARGE.jpg)

(/files/deriv/FV9/DGKH/H1O5DCY5/FV9DGKHH1O5DCY5.LARGE.jpg)


Other quick note: in the video I useda PVC pipe with GTO high voltageinsulated wire taped to the end, andthe other end of the wire connectedto the main ground, as a groundingrod to attract the arcs. while this isall well and good in this particularspark gap coil, i have read severalplaces that other varieties of coilssuch as vaccum tube tesla coils canbe damaged or destroyed by groundstrikes such as this.

Also, while this grounding rodworked safely, as a general rule you



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23 of 27 09-04-2013 19:46


May 6, 2012. 10:27 PM Reply (C1JNTT6H1WHV8JI)

(/member/kdbacho/)

Jan 20, 2012. 6:33 PM Reply (C6HNOHBGXL5OSX4)


May 6, 2012. 10:29 PM Reply (CGPKWUIH1WHV8JW)


May 1, 2012. 5:41 PM Reply (CHR7VS9H1JUIURB)


Apr 14, 2012. 12:05 PM Reply (C2UWTQ0H0OIVCP6)


Apr 14, 2012. 11:27 AM Reply (CMHGSPFH0OIVCME)


Apr 11, 2012. 7:49 AM Reply (C89HR0NH0OIZVWG)


Apr 11, 2012. 3:10 PM Reply (C20KRI4H0OJ6GTI)

Apr 10, 2012. 4:47 PM Reply (CB70EX1H0URBXL8)

shouldn't really be attracting the sparks to you, as this can be dangerous or deadly. animproperly constructed, or improperly used grounding rod could cause electrocution, so DONOT ATTEMPT! I AM NOT RESPONSIBLE FOR INJURY OR DEATH RELATED TO THISMETHOD!


also a quick note on the capacitorbank, due to the unavailability of theexact capacitors in the instructable,the ones I used had a capacitance of.015uF, and a voltage rating of1.6kV, i posted an ebay link to theseearlier, but due to the slightlydifferent capacitance, they must bearranged in 8 rows of 12 capacitors,rather than the 10 rows of 10directed in order to achieve the0.01uF necessary for this coil. Thisconfiguration also has a max voltagerating of 19.2kV.

kdbacho (/member/kdbacho/) says:

just to ask two questions. why were there insicions in the speaker wire and is the secondary coilconnected to the primary. because i dont know were to put the loose ends


also, the "incisions" in the speakerwire are where the insulation wasstripped to connect the test clip, inorder to experimentally tune thecoil i believe.


Bottom of secondary is connected toa ground, top wire is taped to the topload, or bolted to the toroid if youwent fancy


sorry to be bothering you so much, but i also cant find any capacitors rated for 1.5kV 0.01uF... wheredid you get yours?


i take it the resistors need to have a max voltage rating of around the same as the capacitors? whatwas the rating on yours and where did you get them?


ok, im back, Found what appears to be a REALLY great deal on a pair of 9kv 30 mA very-used-but-still-working-guarunteed neon transformers, the only problem is they have GFI, but seller claimsthey have a switch to bypass it, would they be suitable? (id show you the auction but I'm afraidsomeone will grab them first looking at the comment, email?)


daniel (dot) kramnik (at) gmail (dot)com

I can't guarantee that I'll be right, but Ican try to tell!


Ok so I'm going to try and build one of these coils, should be pretty impressive, but I noticed you listedthe price of the neon transformer as $35, I have not found one for anything under $90, and that is a



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24 of 27 09-04-2013 19:46



Apr 10, 2012. 7:02 PM Reply (CNWLC53H0OJ6AAK)

(/member/OzoneLab/)

Feb 26, 2012. 12:21 PM Reply (C3K7W3KGYZNVLKT)

(/member/calamityofwar/)

Jan 11, 2012. 5:26 PM Reply (CP2S4SVGXB2RWZ7)

(/member/calamityofwar/)

Jan 14, 2012. 6:40 AM Reply (C6QDSEEGXEI6EBS)

(/member/Electrodude/)

Jan 13, 2012. 11:38 AM Reply (CSLQIXGGXBK8ADW)


Jan 13, 2012. 1:09 PM Reply (CO6H8V0GXBK8AJP)

(/member/Bumba+Lodh/)

Dec 29, 2011. 10:08 PM Reply (C3BFU9XGWRN4VEZ)

substantial price jump as I'm trying to stay under or around $150. can you suggest a supplier of a $35transformer? or better yet, a link? also, i have not found capacitors of the appropriate exact typeanywhere on ebay, so a link would be nice for that too if possible. Thanks!


I had to wait several months to findthat deal on eBay - it was the wholereason I decided to make an SGTCin the first place!

Given that you could make thedifference between $35 and $90 ina couple days' work, that's probablythe best idea if you want your coilproject to happen in the near future- I'm sorry if this is the not responseyou wanted to hear! =/

OzoneLab (/member/OzoneLab/) says:

Hi-To any one not willing to build there own tesla coil or wants to support Xellers, (if I wasn't so poor afterbuilding my own four inch TC, I would) he has posted a listing on ebay for this coil running up to feb28, 2012.Go to: http://www.ebay.com/itm/250-000-Volt-TESLA-COIL-Assembled-2-Foot-Tall-8-12-Sparks-/180826521311?pt=LH_DefaultDomain_0&hash=item2a1a19bedf#ht_500wt_1303

Xellers- great coil sad to see it go, though.

-OzL

calamityofwar (/member/calamityofwar/) says:

http://www.ebay.com/itm/015uF-015-uF-1600V-5-Radial-Film-Capacitors-100-/380266725123?pt=LH_DefaultDomain_0&hash=item5889a9bf03

.015uF .015 uF 1600V 5% Radial FilmCapacitors (100)

$24.99

Will these work?

calamityofwar (/member/calamityofwar/) says:

Yes these are Metallized PP FilmCapacitor's from the manufactureswebsite (panasonic). PP =polypropelene

Electrodude (/member/Electrodude/) says:

would an electrolytic capacitor work?


Nope

Bumba Lodh (/member/Bumba+Lodh/) says:

i live in India so ebay not possible.Should iuse same type of capacitor that you usedin this project???


Does nobody on eBay ship to India?



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25 of 27 09-04-2013 19:46

Dec 29, 2011. 10:32 PM Reply (CC6MBMJGWF5U7IB)


(/member/Bumba+Lodh/)

Dec 28, 2011. 10:01 PM Reply (CAZBDJTGWQVQCZ8)


Dec 29, 2011. 8:25 AM Reply (CYF2CCQGWF5U49I)

If you can findan Indiansupplier of thecapacitor youneed, thatshould workjust as well,however. I'mafraid I won'tbe able to helpyou find a partdistributor inIndia, though. Ifyou find acapacitoryou're not sureabout, you canpost a link andI'll help youdeterminewhether it issuitable.

Have youregistered on4hv.org? If not,that's the placeto start when itcomes to Teslacoils - youmight even beable to findsomeone elsein India whoknows whereto get the partsyou need.

Bumba Lodh (/member/Bumba+Lodh/) says:

Hi,I built a TESLA COIL with 5kv 30manst.Primary coil made with 4mmcopper tube with 10 turns secondary madewith 2inch PVC pipe.Windingheight 10.2inch(0.315mm enameledcopper wire used) also made Capacitorbank with 2kv 0.15uF polyester filmcapacitor.But the problem is myCapacitor burnt several times but the coilworks with LEYDEN JARcapacitor.Why the capacitorburning??????

Please Help Me!!!!!!!!!!!!!!!


Polyester capacitors will not work ina Tesla coil because capacitanceand voltage rating are not the onlyimportant parameters that you areinterested in. Only polypropylenefilm/foil construction capacitors canhandle the peak pulse currents inthe primary circuit, especially atTesla coil frequencies.

eBay is a good place to start, justbeware, there appears to be awhole line of non-polypropylenehigh voltage capacitors advertisedas "Tesla coil capacitors" that youdo not want to buy.

Good luck!

nerd7473 (/member/nerd7473/) says:

this is so cool i would love to build one



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Oct 26, 2011. 12:47 PM Reply (C6E6KX0GU84TW79)

6(/member/nerd7473/)

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Documents

How to Build a Spark Gap Tesla Coil (SGTC)