Tank Capacitor Calculator
Line Frequency (FL):	50 Hz 60 Hz0 Hz
Output Voltage:		V
Output in Milli Amperes:		mA
*Click on last field (C=) to update result.
C = : MFD (uF)

If one wishes to calculate the ideal MMC capacitance with a standard calculator, please see the equasion below.

60Hz is the frequency of our Line Voltage
15,000V is the voltage of my NST
.06 Amp is the amperage of my NST (60mA)

π (Pi) = 3.14159265358979

C (Capacitance) =

                       1                                            1
_________________________ = ________________ = 0.00000001061033 = .0106uF

(2π * 60Hz * 15000V / 0.06A)       94247779.6076938

Based on this calculation, .0106uF "SHOULD" be the capacitance of my MMC. Mine and Beachley's MMC is calculated to be .015 MFD which is a little higher than what was recommended by the above formula.

How to calculate the capacitance of capacitors connected in series:

In order to better visualize what a Series Configuration looks like, imagine a string of 10 children hand in hand, where each child's right hand is held by the left hand of the child to it's right and so on. All the children are facing forward. Now imagine that each child is a capacitor. This is considered a Series Configuration. When capacitors are hooked up in series, the voltage rating of each capacitor is added together to create a combined voltage rating that is equal to the sum of all of the the capacitors. This is just related to voltage. The general misconception is that the capacitance does not change in a series configuration. This is incorrect. The capacitance for individual capacitors hooked up in a series string actually drops significantly. There is a formula to calculate this below.

The formula to calculate the combined capacitance of capacitors hooked up in series is as follows:
Add the reciprocals of each capacitor. Divide that number into 1.
We can use my 40 Cornell Dublier caps as an example:
For my Tesla coil we have 2 sets of twenty 0.15 MFD capacitors in series that are then hooked up in parallel with each other. If you are confused, just keep reading as it will make more sense below.

1/.15 + 1/.15 + 1/.15 + 1/.15 + 1/.15 + 1/.15 + 1/.15 + 1/.15 + 1/.15 + 1/.15 +
1/.15 + 1/.15 + 1/.15 + 1/.15 + 1/.15 + 1/.15 + 1/.15 + 1/.15 + 1/.15 + 1/.15 = 133.33

Total capacitance of each string of 20 capacitors = 1/133.33 = .0075 MFD

Connecting capacitors in parallel:

When capacitors are hooked up in parallel, add the value of each capacitor to arrive at the total capacitance.

In order to visualize what a Parallel Configuration looks like, imagine a line of 10 children with their arms slightly outstretched. Each child standing in front of the other facing the same direction. Add a long rope that connects all ten children with their left hands. Now add another rope connecting all of the children's right hands. Now imagine that each child is a capacitor and that the rope connecting the children on either side is a copper wire. This is a parallel configuration.
For our Tesla coil we have two separate strings of 20 capacitors, each with a total capacitance of .0075 MFD. When we combine these two strings in parallel we get a total capacitance of .015 MFD (.0075 + .0075 = .015 MFD)

The capacitance of the MMC used in this Tesla coil is 0.015 MFD

OK, to confuse matters a little, here is a link to another web page that calculates our tank capacitor to be 0.02 MFD. Click Here Which one is correct? How much difference does it make?

The Primary Coil

Above: My clip for the primary. You want something smooth with maximum surface contact. I built this one out of 3/8" copper tubing. I pounded it flat. Then I bent it around screw driver and clamped it in a vice to shape it.

I will soon be building a new primary coil for my Tesla coil. As soon as that happens, I will post photos to go with the text. The cunstruction of the primary coil involves two basic steps; making the base to hold the primary and secondary coils and then cutting the four supports that actually hold the copper tubing for the primary coil in place. It may be easier to design and construct the entire support structure for your tesla coil before beginning this step.

The wooden framework for my Tesla coil consists basically of two support levels and is constructed entirely of 3/4 inch plywood. The first level holds the NST, MMC, HV filter, and the spark gap. The second level is created by four risers that are positioned just in from the four corners and are pointing towards the center. Each of these four risers along with the center circle will be the foundation for the the primary and secondary coils. There are many ways to build the support structure for your Tesla coil. Looking at the photos on this page will give you a pretty good idea as to how I designed and built the support structure for my tesla coil. To help the reader under stand what I'm talking about, I drew up the image below on the computer. The lower platform was cut to 23 inches square (recommend 25"). The four main risers for the upper support surface were cut to 9.5 X 11 3/4 inches. Your measurements may vary. The center for the top surface is an 11 inch circle. See diagram below. Enough space must be provided around the toilet flange protruding through the bottom of the center circle for the PVC pipe to fit completely down on top of it.

The primary coil generates the magnetic flux needed to allow all of your components to work together. As current is pushed through the primary coil, it will resonate at a certain frequency, coupling it to your secondary coil. It is necessary to be able to tune this resonance for the best results, so I took that into consideration when coming up with this design.

Your first step should be to acquire a 50' roll of 1/4" copper refrigeration tubing. This kind of tubing can be found at Home Depot or at online vendors like ebay, if you prefer. Be careful when working with the tubing, it can be easily kinked. When you purchase the tubing it will be wound into a circle, do not unwind it. Instead, you will use this shape to your advantage and gently start to spread the layers of copper tubing apart to form your coil.

Each turn of the coil is going to need to be separated by a 1/4" gap. In order to accomplish this make 4 plywood support braces measuring 5 inches X 12 inches each. Please use high grade plywood for this purpose. One can see in the diagram above that the center line for the row of orange holes is set below the surface of the wood. Because of this, the opening in the wood above each hole is less than the outside diameter of the tubing. This is intentional and when the time is right you will actually snap the tubing in place.

You will need to use a drill press and a table saw for this process.

1. To start, measure 1.5" up from the bottom of each piece and extended a line down the entire length.

2. Next number pieces, 1, 2, 3 and 4.

3. On all pieces make a line across the width at 2 inches. This will mark the area reserved for the strike rail.

4. On piece #1 now on the opposite end, draw a line across the width at .5 inches. Then continue to make lines in the same fashion every 1/4" until one reaches the line that was drawn on the opposite end (10 inches).

5. Next, make an "X" between the first two vertical lines drawn in the previous step. I then leave a gap and make an "X" in between the next set of vertical lines, continuing this pattern until one reaches the end.

6. Finally, using a drill press along with a fence clamped to the table, drill a 9/32 of an inch hole at the line wherever there is an "X". For greater accuracy and cleaner results start with a small drill bit like 1/8 of an inch and then expand the hole to 9/32. It is important to work slowly and be precise when drilling these holes. For cleaner looking holes, place a piece of scrap wood under your work.

7. Follow the same procedure on pieces 2, 3 and 4 , except that on piece 2, the first line is made at .625" in., On piece 3 at .75" in., and on piece 4 at .875" in. Feel free to download a printable template in png format for these measurements.

8. One will notice that the first vertical line of each piece is offset 1/16". This way, as the copper tubing makes one complete turn, it will form a 1/4" gap between rows.

9. Now using a table saw one will cut just enough off of the top of the holes that were just drilled so that one can snap the 1/4 inch tubing into place. Stop about 1 1/2 inches before our line at two inch mark, turn the saw off, and cut the rest with a hand saw or band saw. If one does not cut deeply enough the tubing will be too difficult to snap in place. Cut too deeply and there will not be enough wood to hold the tubing in place. I like to use a test piece to set the fence distance from the holes. That way one reduces the chances of ruining a good piece of wood. The copper tubing should fit nice and snug into the holes. Occasionally one might need to used a dab of hot glue for extra support.

11. All four of our coil supports should have the same dimensions. Now lets determine where the hole will be for the strike rail. The strike rail will be made of 3/8 inch copper tubing. Measure down 1 inch and place a mark directly in the center (see Hole for Strike Rail in diagram above). Using a 1/2 inch brad point drill bit drill a hole in this location on each of the four supports.

The next step needs to take place after the Tesla coil's support structure has been completed.

Attaching the Primary Coil Supports to the Base and Winding the Primary Coil

12. With your secondary coil in position over the toilet flange, place primary support #1 in place. Position it so that the copper tubing spiral begins at 7/8 of an inch from the secondary coil surface. Using a pencil, make a mark where the support meets the base. Make a mark in the same location for the other three supports. Next glue support #1 into place with hot melt glue, holding it in position until the glue has cooled. Remove any excess glue with a utility knife. Now one needs to determine the direction of the winds. One might want to consider winding the primary in the same direction as the secondary. Mine is not wound in the same direction and it works just fine. Once one has determined the direction of the winding, go ahead and glue support 2, 3 and 4 into place.

13. Before attempting to snap the primary coil into place, be sure to figure out how you want to come up through the center circle to tie the wire coming from the spark gap to the first turn of the primary. One can see in the photo below that I drilled a hole in the center circle in order to bring the wire up from below and connect to the primary. The wire simply has a long stripped lead that is wrapped around the copper tubing several times and is fastened into place with rubber splicing tape.

13. Now take the 50 foot role of 1/4 inch copper tubing and place it over the secondary and onto the Primary coil supports. The beginning of the coil will start at the support with the .5 Inch mark. See image below.

Note: Soft copper tubing is very flexible but only for one or two bends and then it gets stiff very quickly. This is called work hardening. If your copper tubing for some reason has gotten so stiff that it is unbendable without kinking it or breaking it, then you can heat the tubing up with a propane torch, getting it red hot. Once it has cooled down, it will be soft again.

Next the tubbing will snap into the next support that has it's first hole drilled at .625 inch. Then it will snap into the support that has its first hole at .75 inch. Finally to complete the first turn, snap the tubing into the 4th support that had its first hole drilled at .875 inch. Continue the process until the entire coil is created. You will discover that if executed slowly and patiently, that the tubing bends and adjusts easily and you will be able to wind the entire coil with relative ease.

When creating the strike rail, it is very important that the copper tubing does not form a complete circle. If it does, it could throw off the resonance of the primary. One should be able to purchase just enough 3/8 inch copper tubing from the local hardware store to make the strike rail. That tubing will simply feed through the four holes to make a mostly complete circle. Leave about and inch between the two ends. When wiring up the tesla coil, you will attach a ground wire to it and tape it up with rubber splicing tape like was done on the first wind of the primary coil.

Attaching the Copper Tubing to the Primary Coil Supports

Above: Close-up of how I came up through the wood below to meet the primary at the beginning of the first wind. I wrapped the wire around the copper tubing and then secured it with rubber electrical splicing tape.

The Secondary Coil

I followed thegeekgroup.org Tesla videos to learn how to build the secondary coil and to build the winding jig. They show you how to build the winding jig, but then later wind the secondary coil using a CNC Lathe. If you can forget that they are using a CNC lathe and just pretend they are using the winding jig they showed you how to build in an earlier video, you will be OK. I also actually believe the drill motor works better than the CNC lathe for winding the secondary coil.. Use your finger as a guide for the magnet wire. Your sense of touch is as important as your eyes in this procedure. If a wire crosses over, you will feel it right away and you can back up to correct the overlap. In thegeekgroup videos, they apply a helix of double sided scotch tape onto the PVC tube prior to winding. This does a very good job of holding the magnet wire in place and keeping it taught and from slipping as you do your wind. All will be revealed when you watch the videos.

Above: A view of the 4" toilet ABS flange that is protruding through a hole in the wood floor below. The Toilet flange is bolted to the bottom of the floor below using 1/4" nylon screws and washers. Get a toilet flange that has a test plug in it. As you can see in the above image, the test plug is serving as a base for a 1/4" acrylic disc that is resting on top. The acrylic disk has a 5/16" bolt running through the middle of it. The absolute minimum should be protruding into the tube for the secondary coil when it is in place! The bolt and washer shown in the above photo is used to connect the wire coming from the bottom of the secondary coil.

View of the toilet flange from the bottom. One can see the ground wire that is attached to the bottom of the bolt. One can also see the wire from the secondary coil that is on the other side of the clear acrylic insulator.

Above: View showing how the wire for the secondary coil goes through a small hole to the inside of the tube. Note how the bottom of the secondary coil is at the same level as the primary coil.

Note: Observe that the secondary coil and the primary coil are wound in the same direction. I never here anyone talk about that, but I am fairly sure this little detail is important.

Above: This photo shows the use of a piece of tape to hold the secondary coil wire in place for winding and finishing. After the first coat of finish, one can peal the tape off. There seems to be some argument as to weather or not it is best to keep the secondary wires on the outside or inside. I keep mine on the inside for appearance purposes.

Above: A nice view showing the 1/4" nylon screws used to secure the toilet flange to the wood above. The grounding lug for the secondary is also visible and is attached right next to the toilet flange. From the lug, you can see a HV NST wire that goes to ground. The wire coming off of the bottom of the secondary coil goes to ground.

Above: Another really nice view showing how I constructed the support mechanism for the primary and secondary coils, allowing maximum access to the primary coil. The circular piece of wood you see is the actual base for the secondary coil support. It is held in place with hot-melt glue and by the base for the primary coil. No nails or metal screws were used in this area. One can see the 1/4" nylon screws I used to fasten the toilet flange to the secondary coil's base.

The Top load or Toroid

Above: Following the thegeekgroup's instruction video, I created my top load using a 20" bicycle rim, a large box of 4" flexible dryer duct (15'), a large role aluminum duct tape and 1 role of electrical tape. It works surprisingly well. You will notice that the 4" cap is shorter than what you would normally see at the hardware store. I carefully trimmed it off using a table saw. I left 1" of contact surface on the inside of the cap. This is offers plenty support for the toroid, but at the same time makes it easier to get it on and off. If you try this on your own, for sure, wear safety glasses, keep your blade as low as possible, and watch your fingers. It was the only way I could think of to get a perfectly smooth cut. The Toroid should be between 4 and 6 inches above the secondary coil.

I removed the original axel and bearings out of the bicycle rim and replaced them with 5/16' threaded rod that was tightened into place with washers and nuts. You can see in the photo above that I used a fender washer and bolt over the aluminum tape to finish the toroid. Every piece of tape going across the bicycle rim went over the CENTER axel. I had to cut a hole into the center of the tape for every piece. In the thegeekgroup video, the Chris Boden applies the tape around the axel. I did not like that. When you watch the video, you will know what I'm talking about.

If I were to do it again, I would build a different toroid (click on link) using a more rigid fllexible aluminum duct and two aluminum plates. It will be cheaper and much faster to build! The only thing I would do differently is to use a metal threaded rod instead of Nylon for use with my coil. http://www.youtube.com/watch?v=z30RFaJ2bY8

The Winding Jig

The next few images are of my secondary coil winding jig. I got the idea from thegeekgroup.org videos. It worked flawlessly. You need one person to help wind the coil.

Above: My secondary coil shortly after it was wound and the first coat of polyurethane had been applied. To apply the finish, run the drill motor at low speed and paint (or spay) the finish on with a brush. This is a fantastic way to apply the finish to the secondary coil. Once a new coat of finish has been applied, one can simply set the drill motor on low speed and tape the trigger in place so it will keep the secondary coil turning on its own. The weight of the drill motor handle, keeps the drill motor from spinning around. I applied some mineral oil in the places where threaded rod touches the wood for lubrication. To complete the job, I put 10 coats of polyurethane onto my secondary winding.

This synchronous rotary spark gap will soon replace the static spark gap that is currently connected to my Tesla Coil. As soon as I have my tesla coil working with the new upgrades I will post new photos and video links!

Determining the Resonant Frequency of a Tesla Coil

How to determine the resonant frequency of a tesla coil.

The resonant frequency of a tesla coil is determined by the inductance of the secondary coil and the capacitance of the Tesla coil's top load.
We will be using a total of 3 calculators found at the following URL in order to determine the resonant frequency of my tesla coil.
http://deepfriedneon.com/tesla_frame6.html

1.) The Helical Coil Calculator
2.) The Topload Calculator
3.) The Frequency of LC Circuit Calculator

Designing The Secondary Coil

According to information on the the Deep Fried Neon web site, we wish to aim for around 800 to 1000 turns of wire for the secondary coil. So to begin, let's just arbitrarily say we want a 900 turn secondary coil. I did not have this information when I wound my coil. I simply used 22 gage heavy coated magnet wire to wind my secondary coil. I was aiming for 30 inches long and when it was all done it turned out to be 33.125 inches (33 1/8"). The nice thing about doing these calculations first, is that one can predetermine the secondary coil size and the tesla coil's frequency by plugging in different variables into the helical coil calculator. If I were to do it again, I might use 23 or 24 gage heavy coated magnet wire to wind my secondary coil and make it just a little shorter. It would be helpful to find accurate wire size specifications from a retailer or manufacturer in advance so that one can easily plug wire and insulation specifications into the calculator. If one has samples of various magnet wire sizes, one can use a precise caliper to measure the magnet wire. Take one measurement of the wire thickness with insulation. Then burn some of the insulation off, gently clean it and remeasure to determine the thickness of the insulation and the turn spacing.

In my case, 22 gage magnet wire may have been a little thick, but it actually worked out well in the end, because it made a somewhat long secondary coil which in turn positioned the top-load a good distance from the primary coil. One thing we want to avoid is having a secondary coil that is so short, that arching occurs between the top-load and the primary coil. This can quickly and easily destroy your power supply and even your MMC capacitor.

Below you will find the criteria necessary to calculate the inductance of the secondary coil.
Variables are:
• Diameter of secondary coil form
• Number of turns on the secondary coil
• Wire diameter
• Turn Spacing. Turn spacing is the amount of actual space between the magnet wire created by the wire's insulation. The quick and dirty way to calculate the turn spacing is to use the 10% rule. After you determine the total thickness of the magnet wire, you can simply multiply that by .10. That will give you an estimate of the turn spacing. Keep in mind that a sloppily wound secondary coil with lots of spaces between the wires will significantly add to the overall turn spacing.

Specifications for my secondary coil are as follows. I used 22 gage magnet wire for my secondary coil. Using a precise caliper I was able to determine the magnet wire thickness and the thickness of its insulation. The thickness of the wire with the insulation is .027 inches. The thickness with the insulation burned off is .025 inches leaving a difference of .002 inches. .002 divided by 2 is .001 inches, which is the actual thickness of the insulation of a single strand of my magnet wire. Multiply .001 X 2 = .002 and we arrive at the turn spacing, or in other words, the insulation thickness of two wires side by side.

Using a tape measure I was fairly accurately able to determine that there are 19 turns per inch. 19 X 33.125 = 629.375. This indicates that I have approximately 629 turns on my secondary coil.

The secondary coil was tightly wound around a 4.5 inch outside diameter PVC pipe.

Now we have all of the variables to plug into the helical coil calculator.

Discharge Terminal or Top-Load:

There are only two variables for calculating the capacitance of the top-load; its diameter and thickness.

The discharge terminal acts as a capacitor and forms part of the secondary LC circuit. Its value is dependent on its shape and size, and can be worked out with the above Top Load' Calculator.

Determining the Resonant Frequency of Secondary Circuit
To plug in the the numbers into this calculator you will first need to convert microhenries (uH) to millihenries (mH). Use the following web calculator to make the conversion.
http://www.unitconversion.org/inductance/millihenry-to-microhenry-conversion.html

Then you will need to convert Pico-Farads (pF) to Micro-Farads (uF). You can use the conversion chart at the bottom of this page to do that. An Example would be 22 pF = .000022 uF

By plugging in the inductance value of the secondary coil and the capacitance of the top-load into the Resonant Frequency LC Circuit Calculator, we can now determine what the Tesla coil's resonant frequency is or will be. Please keep in mind that the resonant frequency will change depending on the proximity of grounding sources close to your Tesla coil as this changes the capacitance of the top-load. As you can see in the results below, the resonant frequency of my Tesla coil is about 327 kHz.

Additional Tidbits

22 Gage Magnet Wire - 516 Feet per Lb. -
DIA with insulation .027 inches
DIA without insulation .025 inches
Insulation Thickness - .001 Inches
Turn Spacing - .002 inches (plus any human error)

AWG Wire Specifications
Measurements do not include insulation