Here’s my small spark gap Tesla coil, so called because there’s this spark gap here,
as opposed to a solid state circuit. This one is also tunable, for best results,
to some extent. In this video I’ll show you step-by-step how
to make it and tune it. Note that this is my first Tesla coil,
even though it’s around version 5 of it, so I’m giving you what I’ve learned up to
this point. Check the video comments for any corrections
or useful suggestions from others. Also note that though tuning is done,
it’s done in a limited way and so resonance cannot be gauranteed. One key part, and the hardest to make part,
is this power supply here. I’m using my Cube high voltage, DC power supply.
I won’t go into detail on how to make it here. I have this other video explaining how to
do that instead. Click on this annotation or the link in the
video description. The rest is fairly easy to make and consists
of two resonant circuits. The first is called the primary circuit and
consists of these capacitors, this spark gap,
and this primary coil. The second is called the secondary circuit
and is just this much taller coil and this ball on top covered in almuminum
foil, which is called a topload. Note that I called them resonant circuits.
They both resonate on their own, at some frequency, moving energy around between their capacitors
and their coils. The capacitor in the secondary circuit
is the capacitance within the tall coil itself, and in the ball and the surroundings. The details of how it works would take a whole
other video but for here what’s important to know
is that you want the resonant frequency of the primary circuit
to be as close as possible to the resonant frequency of the secondary circuit. One approach to getting the frequencies the
same is to start by designing your Tesla coil using
an online Tesla coil calculator, then making it,
and then tuning it since what you make won’t exactly match what
you calculated. The online calculator I used is this very
popular one called JavaTC. I didn’t use all the features of this calculator.
Just the things in the top section. What I was shooting for was that when I click
on its RUN JAVATC button, the two frequencies it gave me here would
be close to the same. This is the resonant frequency for the secondary
circuit and this is the resonant frequency for the
primary circuit. Doing these calculations is an iterative process.
You try some values for what you think you can make,
then click on the RUN JAVATC button to see if you get frequencies that are close
together. If they’re not then you try new values,
and keep doing that until you come up with something you can make.
I try to get a primary resonant frequency that is a little less,
at most 10% less, than the secondary resonant frequency.
That’s a rule of thumb that’s intended to account for the fact that
the spark gap will heat up over time, affecting the actual frequency. For the units I chose cm, or centimeters,
or the metric system since it makes things easier.
But I’ll give dimenstions in inches too. Before going further,
I fill in the dimensions for the room the Tesla coil will be in. Now to start making it. First, the secondary coil. Since they’re easy to find,
I decided to use a paper towel tube and a toilet paper tube taped together.
The top and bottom radius are both 2.2 centimeters, and that goes in the calculator here. I’m using 26 gauge, enamel coated wire.
This is available in electronics stores and can be salvaged from old motors and electronics.
I’m putting on 750 turns, which works out to a 34.425cm long coil.
I used another online calculator to get the total wire length needed,
which is 103 meters, but make sure to have a little extra for the
two ends for connecting to things.
That’s all in the calculator here. Rather than count turns while winding it,
I just mark the length on the tubes. I poke holes at either end,
and push one end of the wire through one hole, securing it with tape.
I start winding. There are faster ways of doing that that take
some set up, but I can do it while a good science documentary,
so I continue by hand. In the end it takes only around two hours.
Notice that then ends don’t have to be very long,
and shorter is better. I trim the top end of the tube,
and carefully strip off the insulation. Some tape on the inside,
and/or some glue, like this super glue from a hobby store,
will help keep it in place. For the topload,
I’m using this 8 centimeter in diameter Christmas tree ornament
from a craft store. Pretty much any round ball will work.
A rule of thumbs is that it should have a larger diameter than the
secondary coil. But make sure you include its dimensions in
the online Tesla coil calculator like I did.
The Sphere Center Height is from the bottom of the Tesla coil
to the center of the sphere. Once you’ve filled it all in and selected
topload, click on add to add it to the list of Sphere
Objects. The outer surface has to be electrically conductive,
so I wrap it in kitchen aluminum foil, trying to make it as smooth as I can.
After triming it inside, I tape the two halves together,
making sure that the foil on one touches the foil on the other.
Next, I tape the wire from the coil to the topload.
And then I hot glue the topload to the end of the tube.
Tape also works. Next I need to make the primary coil.
I made two of them. At first I made one using 12 gauge insulated
wire and then to try tuning it better I made another
with 16 gauge bare wire. The resulting output is around the same
so I’ll show making the 12 gauge insulated wire one,
since it’s easiest. From playing around with the calculator I
found that a 4 centimeter radius with 7 turns of
wire gives me the needed resonant frequency.
I calculate the height of the coil by measuring the diameter of the wire
and multiplying it by 7, which gives me around 2.5 centimeters. Before winding the coil
I need to make the cylinder that it’s wrapped on.
So to make the cylinder I need a piece of cardboard that’s 2.5 centimeters
high by 23.5 centimeters long,
but after adding extra for playing around with any overlap,
I decide on 4.5 centimeters by 30 centimeters. I cut it out,
and then I make a mark at 23.5 centimeters. I wrap it around a can to make it roundish,
and tape it such that one end stops at the 23.5 centimeter mark,
with the overlap on the inside. But I also want to be able to move this up
and down for tuning purposes. So I cut another piece of carboard that’s
one centimeter taller, but when I tape it,
I size it to fit snuggly inside the first one.
Now the first one can slide along that one. Time to wrap the wire onto it.
I start by putting two pieces of tape beside each other
that span the height of the cylinder. I also put another piece on the opposite side.
Near the bottom of one tape, I tape the wire in place,
and start coiling it around. I also tape the first turn on the other side.
And then I keep coiling until I get to the last turn.
I tape that one on the other side, and finish it by taping it beside where the
first one started. The two ends sticking out are called the leads,
and are represented in the calculator here. As I said I made another primary coil using
16 gauge bare wire, with the same dimensions,
to try some additional tuning. But once I’d tuned it,
it gave comparable results, meaning my 12 gauge insulated one was already
well tuned. For the spark gap,
I cut the top off a plastic soda bottle and I make two holes on either side,
being very careful not to stab myself. I’ll be fitting some nails in and I want the
fit to be fairly tight. Then I cut slots down the side.
That’s so that I can put the nails in with their flat heads facing each other.
Notice that the gap between them is easily adjustable.
You want the spark gap to be in air as much as possible like this
so that the surrounding air can help keep it cool. And the last part is the primary circuit’s
capacitor, or capacitors in this case.
From playing with the calculator, I know I need 0.004 microfarads, or 4 nanofarads,
of capacitance. To get that I’m using four of these ceramic
capacitors, 1 nanofarad each and rated for 20,000 volts.
I bought them from amazing1.com but you can find them on ebay and other places
for low prices. Having four 1 nanofarad ones allows me to
try different combinations. To connect them together I have this terminal
strip, or terminal block.
There are holes on both sides and these holes are connected together,
these holes are connected together and so on.
You can solder the the capacitors together if you prefer
or use some other method. I prepare these wires and
put them in these holes along with two capacitors
and that connects them both in parallel. It doesn’t matter which way they go,
there’s no plus or minus to the capacitor legs.
The screws on top hold them in place. I insert two more capacitors on the other
side. Make sure they’re all in tight.
When it’s all finished, this wire
and all these legs of the capacitors are connected together.
And this wire and all these legs are connected together.
All the capacitors are now in parallel, causing their capacitances to add up for a
total of 4 nanofarads. Finally I can cut the terminals from the rest
of the strip. I need a base and some way to hold the secondary
coil up. For that I cut a piece of paper towel roll,
and cut a section out along its length. That gets hot glued to one end of a board.
That’s so that it’ll fit snugly inside the secondary tube
with enough of a gap for the wire to fit through. It fits on nicely. Time to put the whole Tesla coil together. I start by removing the secondary coil from
the base and slipping the primary coil over it.
Then it’s just a matter of putting the secondary back in place,
and lowering the primary. The nice thing about this design
is that it’s easy to try different primary coils. This wire coming from the bottom of the secondary
coil needs to be connected to ground.
For that I have this standalone plug which I bought from a hardware store,
and inside it I’ve connected just one wire to this long prong,
In North America, that’s ground. After plugging that into a wall socket,
I connect the other end of that wire to the wire coming from the primary.
A more premanent connection can be done by soldering it
or you could put some sort of spade or butt connectors on the wires. Then I connect one end of the primary coil
to the wire coming from the high voltage power supply.
That’s also connected to one side of the capacitors. The other side of the capacitors goes to one
side of the spark gap, but notice that connection is made using an
alligator clip that’s part of a wire going to the power supply’s
negative. And lastly,
the other end of the spark gap goes to the other end of the primary coil.
Done! Check that there’s a gap in the spark gap,
and that the primary coil is centered around the secondary coil.
Turn on the power supply and turn it up. The loudness depends on the size of the spark
gap, a bigger gap is louder,
and less frequent, but more powerful each time.
So you can play with that. To tune it, get a long plastic stick, perhaps
even a ruler, and tape a wire to one end of it.
I’m using a clamp to hold the stick vertical. At the top, attach a needle.
The other end of the wire can just hang down. Turn on the power supply.
Then slowly adjust the distance between the tip of the needle
and the topload such that you get a non-continuous spark.
Slowly move the needle closer until the spark starts being continuous.
Your body can interfere with all this, so you can step away a meter, or a yard,
after each time you move the needle. Next, turn off the power supply.
Make a discharge stick by taping a wire to the end of a stick,
with perhaps another of those plugs on the other end of the wire.
With it plugged into ground, discharge the spark gap,
and the topload. Be careful not to move the topload when you
do this, since that will interfere with the distance
to the needle. Now that everything’s safe, raise or lower
the primary coil. This changes the coupling between the two
circuits. Turn the Tesla coil back on.
Move the needle closer or farther until you get a non-continuous spark again,
and then closer until you start getting continuous sparks again.
If the distance between the topload and the needle is farther than before
then you’re moving the primary coil in the right direction,
otherwise try the other direction. Keep doing this until you get the longest
continuous sparks. Another form of tuning
involves changing the number of turns on the primary coil.
Here’s another primary coil I made. The main difference is that it uses bare 16
gauge wire, the key being that it’s bare wire.
It has the one extra turn for extra adjustability. Since there’s no insulation, there’s a gap
between each turn. Just like the other primary coil,
this one has one end connected to the high voltage power supply.
But the other end goes nowhere. Instead, one end of the spark gap is connected
to the coil via this wire with alligator clips.
By moving this alligator clip elsewhere on the coil
I can change the number of turns, and therefore the frequency more directly. But after doing that,
I find that I still get the longest sparks between the topload and the needle when I
have around 7 turns, just as calculated.
So using this easier to make coil is just fine. And that’s one way to make a small spark gap
Tesla coil. Well, thanks for watching! See my youtube channel, rimstarorg for more
interesting videos like this. That includes one with more demonstrations
of this Tesla coil in action. Also, the one I mentioned about how to make
the Cube power supply. And for variety,
one on how to do wireless transmission of electricity
using a joule thief circuit. And don’t forget to subscribe if you like
these videos, or give a thumbs up,
share with your social media, or leave a question or comment below. See you soon!