Build a Tesla Coil (the way Tesla built them)

Calculations and Preparations

Starting guide: wind a coil with a height-diameter ratio around 1:1 with an air-gap between turns of at least half the wire diameter.

Calculating Wire Length https://Hakasays.com/DollardTeslaCoilCalculator
or:
297/F = L
F = frequency in Mhz
L = wire length in feet

Note that due to dielectric effects, a Tesla Extra coil has a higher frequency than is predicted by normal 1/4 wavelength formulas. We call this the ‘velocity factor’ and it is directly related to the height-to-width ratio of the coil.


Framing Material Selection

  • Best: UHMW, HDPE, LDPE, PTFE(Teflon), PP
  • OK: Polystyrene
  • Meh: Polycarbonate, Acrylic, Epoxies, PVC, Wood
Sadly, this means that hardware store plastic sheeting just aren’t going to cut it. But HDPE buckets from the paint section…….
  • 3/16″ to 1/4″ thickness works good for coils 3-12in in diameter
  • Plastic sheeting is usually sized in 12×12″ sections, so cost-efficient diameters are around 5-5.5″ and 11-11.5″
  • White/light plastic have lower loss characteristics
  • Material selection has a higher impact at higher frequencies

Wire selection:

The general goal here is to get the lowest resistance practical.

Obviously few people can afford 100ft of 0 gauge copper bus-bar to wind a coil, so compromises must be made. Generally we recommend not going below 20awg though as the loss characteristics begin to compound making a very high Q coil difficult to achieve.

  • Silver-coated Teflon wire
  • Silicone-coated wire
  • Litz wire
  • Coax cable can also be used to create a large effective diameter coil by using the outer ground conductor (per Eric Dollard)
  • Coax cabling can also be used to create a large effective diameter coil by using the outer ground conductor (per Eric Dollard)

Construction

‘Jigsaw method’

Cheapest/simplest tools required:

  • Drill + drillbit set
  • Jigsaw / router / hand saw
  • Hand files

Cutting the top+bottom disks. Best practice is to use a circle-cutting jig on a jigsaw/router, but many techniques could be used to do this.
Notching the disks. Notch width = thickness of your material. Depth is not critical but should be at least 2x the thickness of the notch.
Notching+grooving the vertical risers. This is the best time to cut the wire grooves, which can be done with a hand saw in a pinch.

Now you’ve finished your first Tesla Coil. What do I do with it?

Testing and Tuning (coming soon)

4 thoughts on “Build a Tesla Coil (the way Tesla built them)”

    1. For testing you can use a function generator or HAM radio transmitter (if it is on the right frequency).

      The most efficient power supply would be a class E amplifier, which would look like this:
      https://www.researchgate.net/figure/Schematic-of-69MHz-Class-E-amplifier_fig2_320623200

      The inductor on the right would be your Tesla Extra coil,
      instead of a filter cap and resistor you would have a bridge rectifier and capacitor filter.

      Feel free to email me @ bakahsay@gmail.com or discord @ Hakasays#7694 and I can try to help you get something together. 🙂

  1. Hi Hakasays (I don’t know your name). I am utilizing your TeslaCoilCalculator to build my first tesla coil. There are two spacing parameters listed in the output: Wire Spacing and Ideal Wire Spacing. The Ideal Wire Spacing is much closer than the Wire Spacing parameter. Which parameter should I use to wind my coil?

    Where are the detailed calculations for the calculator output stored? May I have access to these formulas and the associated references?

    Thanks and have a great day,

    Breck.

    1. The equations were pulled from Eric Dollard’s “crystal radio initiative” project, which I believe is an Ebook and a couple videos.
      Some useful bits here: https://kupdf.net/download/crystal-radio-initiative_5af89140e2b6f5131fd54e23_pdf

      Ideal wire spacing is 62% of the wire diameter. So a 1mm wire would be 1.62mm from center-to-center. (Wire spacing has a bug that I haven’t patched-out yet, sorry about that)

      I do intend on posting the formulas driving the calculator online at some point, just been busy with other side-projects like the telluric work.

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