Nikola Tesla invented this high current device in an attempt to recreate the oscillations of the sun's radiation. This he believed would allow for the recreation of the suns rays on earth so that there would be sun light in the dark. Although he never accomplished this task he managed to create a device which is very intriguing, along with the idea of wireless energy transportation and the fluorescent light tube.
Toroid
This is a Toroid, it can come in two different forms a sphere or donut shape
(actually called a toroid), because a metal sphere can replace the toroid, a
sphere is also called a toroid when used as a discharge sphere on the tesla
coil. Classically the donut shaped toroids are used. The toroid gives the extra
variable of capacitance in secondary coil. Which helps to improve spark length
because a greater charge is held on a larger toroid.
If the toroid is too big instead of increasing spark length it will yield to arcing in between the windings of the secondary coil, which is very bad because secondary coils not only have very thin insulation which is burned off easy enough but also the difficulty and expense of winding a secondary coil makes it essential that the coil be preserved in the best condition possible.
Here is a picture of a a simple toroid built from flexible metal ducting. It is about 30 cm at the diameter.
Secondary Coil
The secondary coils is what receives the resonating charge from the tank circuit (the primary
coil, high voltage power supply, spark gap, and capacitor are all the components
of the tank circuit). The secondary has no electrical connections to the tank
circuit, and it is connected at the bottom to electrical ground, and at the
top it is connected to a toroid.
This is the Secondary on my coil it was wound with #21 gauge insulated copper wire. The coil is about 21 inches in height and 4 inches in diameter wound around pvc piping that was a bit longer.
The shape and form of this coil is very important, although the coil may work with a bad primary coil it will loose much energy if the shape is deformed from a relative circular winding. Some people like to wind their primaries in conical forms which tends to work very well but it can become very difficult to build.
I have constructed my Tesla Coil's primary coil with a standard cylindrical form because it proved to be the easiest means of building it.Here it is:
This coil was wound with thick twisted copper wire which was then placed inside a 1/2 inch outer diameter, plastic tube. I made a slice down the tube to insert the copper into, then it was would around the eight pvc supports that I had screwed into the wood platform. recently I have cut off the excess tubing and the coil was properly glued into place.
In the center there is a white disk (the bottom of a plastic bucket) this is to hold the pvc supports in place, the hole was made for the primary coil to fit in.
The best part about using the tubing on the primary was that it allowed the wires to be laid as close to each other as possible.
The spark gap is one of the most difficult components in the Tesla Coil. The spark gap must be able to hold up to extremely high temperatures caused by the arcing. This means that the best metal is tungsten, but the hardest part is that this metal is extremely difficult to cut and is not readily available.
My tesla coil is built with the type of spark gap known as the "Richard Quick" spark gap. This gap is very easy to put together all that is needed is a five inch piece of pvc tubing and a approximately 3 inch long pieces of 1 inch diameter copper tubing. The tubing is then screwed on to the pvc pipe so that the curved sides of each piece are facing each other, and they are set apart appropriate distances for arcing, the resistance of the spark gap can be reduced or increased by removing or adding more copper tubes.
Here is mine:
I used the plugs found on electrical circuits connecting wires to connect the spark gap to the rest of the TC.
The capacitor can be readily made with a bunch of beer cans. tinfoil, and salt water. At the moment this is what powers my TC, and it does it quite reliably, but that does not go for efficiency. This type of cap has many sharp edges, cased by the tinfoil, and it also needs allot of wires which leeds to loss in the inductance of the primary coil. A better cap is made by using Mica, glass, or several layers of plastic, all with alternating layers of metal, preferably copper but tinfoil works as well. In the case of beer bottles the glass is the dielectric which insulates the conductive salt water from the tinfoil, and keeps the charges on either side from arcing.
The power supply for TC's is generally a high voltage neon sign transformer about 10-15 kv. But smaller power supplies can be strong together to give a higher voltage. This is usually done with Microwave Oven Transformers (MOT). But the MOT is usually much more dangerous than the neon sign transformer which has a current limiting capability.
Please let me know what you think: viziard@hotmail.com
