Nikola Tesla is a legendary person, and to this day they still argue about the meaning of some of his inventions. We will not go into mysticism, but we’ll talk better about how to do something spectacular according to Tesla’s “recipes”. This is a Tesla coil. Seeing her once, you will never forget this incredible and amazing sight!
General information
If we talk about the simplest such transformer (coil), then it consists of two coils that do not have a common core. The primary winding should have at least a dozen turns of thick wire. At least 1000 turns are already wound on the secondary. Keep in mind that the Tesla coil has a transformation ratio that is 10-50 times greater than the ratio of the number of turns on the second winding to the first.
The output voltage of such a transformer can exceed several million volts. It is this circumstance that ensures the appearance of spectacular discharges, the length of which can reach several meters at once.
When were transformer features first shown to the public?
In the town of Colorado Springs, once a generator completely burned out at a local power station. The reason was that the current from it went to power the primary winding of the invention of Nikola Tesla. During this brilliant experiment, the scientist first proved to the community that the existence of a standing electromagnetic wave is a reality. If your dream is a Tesla coil, it is most difficult to do the primary winding with your own hands.
In general, making it yourself is not so difficult, but it is much more difficult to give the finished product a visually attractive appearance.
The simplest transformer
First you have to find somewhere a high voltage source, and at least 1.5 kV. However, it is best to immediately count on 5 kV. Then we fix it all to a suitable capacitor. If its capacity is too large, you can experiment a little with diode bridges. After that, make the so-called spark gap, for the sake of the effect of which the entire Tesla coil is created.
To make it simple: take a pair of wires, and then twist them with electrical tape so that the bare ends look one way. We very carefully adjust the gap between them so that the breakdown is at a voltage slightly higher than that for the power source. Do not worry: since the current is alternating, at the peak the voltage will always be slightly higher than declared. After that, the entire structure can be connected to the primary winding.
In this case, for the manufacture of a secondary one, only 150-200 turns can be wound on any cardboard sleeve. If you do everything correctly, you will get a good discharge, as well as its noticeable branching. It is very important to ground the terminal from the second coil well.
Here's a simple Tesla coil. With your own hands, everyone who has at least minimal knowledge of electrics can do it.
We construct a more "serious" device
All this is good, but how is the transformer arranged, which is not ashamed to show even at any exhibition? To make a more powerful device is quite realistic, but for this you will need to work a lot more. First, we warn that for such experiments you must have very reliable wiring, otherwise trouble can not be avoided! So what should be taken into account? Tesla coils, as we have said, need a really high voltage.
It should be at least 6 kV, otherwise you will not see beautiful discharges, and the settings will constantly get lost. In addition, the spark should be made only from solid pieces of copper, and for the sake of your own safety, they should be fixed as firmly as possible in one position. The power of the entire "economy" should be at least 60 watts, but it is better to take 100 or more. If this value is lower, then you definitely won’t get a truly spectacular Tesla coil.
Very important! Both the capacitor and the primary winding must necessarily ultimately form a specific oscillatory circuit that enters the state of resonance with the secondary winding.
Keep in mind that the winding can resonate in several different ranges at once. Experiments have shown that there is a frequency of 200, 400, 800 or 1200 kHz. As a rule, all this depends on the condition and location of the primary winding. If you do not have a frequency generator, you will have to experiment with the capacitance of the capacitor, as well as change the number of turns on the winding.
We remind you once again that we are discussing the Tesla bifilar coil (with two coils). So the issue of winding should be taken seriously, because otherwise nothing sensible will come of it.
Some Capacitor Information
The capacitor itself is better to take not too outstanding capacity (so that he has time to accumulate charge in time) or use a diode bridge designed to rectify the alternating current. Just note that the use of the bridge is more justified, since you can use capacitors of almost any capacity, but you will have to take a special resistor to discharge the structure. Shocks from him very (!) Strongly.
Note that the Tesla coil on the transistor is not considered by us. After all, you simply will not find transistors with the necessary characteristics.
Important!
In general, we remind you once again: before assembling the Tesla coil, check the condition of all the wiring in the house or apartment, take care of the availability of quality grounding! This may seem like a boring exhortation, but they are not joking with such tension!
It is absolutely necessary to isolate the windings very reliably from each other, since otherwise you will be guaranteed to break through. On the secondary winding, it is desirable to make insulation between the layers of turns, since any more or less deep scratch on the wire will be decorated with a small but extremely dangerous discharge crown. And now - to the cause!
Getting to work
As you can see, you will not need so many elements for assembly. You just need to remember that for the correct operation of the device you need to not only assemble it correctly, but also configure it correctly! However, first things first.
Transformers (MOTs) can be removed from any old microwave. This is almost a standard power transformer, but it has one important difference: its core almost always works in saturation mode. Thus, a very compact and simple device can very well produce up to 1.5 kV. Unfortunately, they also have specific disadvantages.
So, the value of the idle current is approximately three to four amperes, and the heating even in idle time is very large. In an average microwave, the ILO produces about 2-2.3 kV, and the current strength is approximately 500-850 mA.
Characteristics of the ILO
Attention! For these transformers, the primary winding starts at the bottom, while the secondary is at the top. This design provides better insulation of all windings. As a rule, on the “secondary” there is a filament winding from a magnetron (approximately 3.6 Volts). Between two layers of metal, an attentive master can notice a pair of some metal jumpers. These are magnetic shunts. What are they needed for?
The fact is that they close on themselves some part of the magnetic field that the primary winding creates. This is done to stabilize the field and the current itself on the second winding. If they are not, then with the slightest closure, the entire load goes to the “primary”, and its resistance is very small. Thus, these small parts protect the transformer and you, as they prevent many unpleasant consequences. Oddly enough, is it still better to remove them? Why?
Remember that in a microwave oven, the problem of overheating of this important device is solved by installing powerful fans. If you have a transformer in which there are no shunts, then its power and heat dissipation are much higher. For all imported microwave ovens, they are most often thoroughly coated with epoxy. So why do you need to remove them? The fact is that in this case the "drawdown" of the current under load is significantly reduced, which is very important for our purposes. What to do with overheating? We recommend placing the ILO in transformer oil.
By the way, a Tesla flat coil generally dispenses with a ferromagnetic core and a transformer, but needs to supply an even greater voltage current. Because of this, trying something like this at home is strongly discouraged.
Safety again
A small addition: the voltage on the secondary winding is such that electric shock during its breakdown will lead to guaranteed death. Remember that the Tesla coil circuit assumes a current strength of 500-850 A. The maximum value of this value, which still leaves a chance of survival, is ... 10 A. So when working for a second, do not forget about the simplest precautions!
Where and how much to buy accessories?
Alas, there is some bad news: firstly, a decent ILO costs at least two thousand rubles. Secondly, finding it on the shelves of even specialized stores is almost impossible. There is only hope, perhaps, for collapses and “flea markets,” which will have to run a lot in search of the desired one.
If possible, be sure to use the ILO from the old Soviet microwave oven, Electronics. It is not as compact as imported counterparts, but it also works in the mode of a conventional transformer. Its industrial designation is TV-11-3-220-50. It has a power of approximately 1.5 kW, produces about 2200 volts at the output, and the current strength is 800 mA. In short, the parameters are very decent even for our time. In addition, it has an additional 12 V winding, ideal as a power source for a fan that will cool the Tesla spark.
What else do you need to use?
High-quality high-voltage capacitors made of ceramics of the K15U1, K15U2, TGK, KTK, K15-11, K15-14 series. Finding them is difficult, so it's best to have professional electricians in good friends. What to do with a high-pass filter? You will need two coils that can reliably filter out high frequencies. Each of them should have at least 140 turns of high-quality copper wire (in varnish).
Some information about the spark
The spark is designed to excite oscillations in the circuit. If it is not in the circuit, then the power will go, but the resonance is not. In addition, the power supply starts to “punch” through the primary winding, which is almost guaranteed to lead to a short circuit! If the spark is not closed, the high voltage capacitors cannot be charged. As soon as it closes, oscillations begin in the circuit. It is to prevent some problems using a throttle. When the spark closes, the inductor prevents current leakage from the power supply, and only then, when the circuit is open, accelerated charging of the capacitors begins.
Device characteristic
Finally, we will say a few more words about the Tesla transformer itself: for the primary winding, you can hardly find the copper wire of the desired diameter, so it is easier to use copper pipes from refrigeration equipment. The number of turns is from seven to nine. At least 400 (up to 800) turns must be wound on the “secondary”. It is impossible to determine the exact amount, so experiments will have to be made. One output is connected to the TOP (lightning emitter), and the second is very (!) Reliably grounded.
What to make a radiator from? Use an ordinary ventilation corrugation for this. Before you make a Tesla coil, the photo of which is here, be sure to think about how to design it more original. Below are some tips.
In conclusion…
Alas, this effective device has no practical application to this day. Someone shows experiments in institutes, someone makes money on this by arranging parks of "miracles of electricity". In America, a very wonderful comrade made a couple of years ago a Tesla coil ... a Christmas tree!
To make it more beautiful, he applied various substances to the lightning emitter. Keep in mind: boric acid gives a green color, manganese makes a "Christmas tree" blue, and lithium gives it a raspberry color. There is still debate about the true purpose of the invention of a brilliant scientist, but today it is a common attraction.
Here's how to make a Tesla coil.