In 1997, I became interested in the Tesla coil and decided to build my own. Unfortunately, I lost interest in it before I could launch it. After a few years, I found my old coil, counted it a little and continued building. And again I abandoned it. In 2007, a friend showed me his reel, reminding me of my unfinished projects. I found my old reel again, counted everything and this time completed the project.

Tesla coil is a resonant transformer. These are mainly LC circuits tuned to one resonant frequency.

The high voltage transformer is used to charge the capacitor.

As soon as the capacitor reaches a sufficient level of charge, it is discharged to the spark gap and a spark jumps there. A short circuit occurs in the primary winding of the transformer and oscillations begin in it.

Since the capacitance of the capacitor is fixed, the circuit is adjusted by changing the resistance of the primary winding, changing the point of connection to it. When properly tuned, a very high voltage will be at the top of the secondary winding, resulting in impressive discharges in the air. Unlike traditional transformers, the ratio of turns between primary and secondary windings has little or no effect on voltage.

Construction stages

It is pretty easy to design and build a Tesla coil. For a beginner, this seems like a daunting task (it also seemed difficult to me), but you can get a working coil by following the instructions in this article and doing some small calculations. Of course, if you want a very powerful coil, there is no way other than learning theory and doing a lot of calculations.

Here are the basic steps to start with:

1. Choice of power supply. Transformers used in neon signs are probably best for beginners as they are relatively cheap. I recommend transformers with an output voltage of at least 4kV.
2. Arrester manufacturing. It might just be two screws screwed a couple of millimeters apart, but I recommend putting in a little more effort. The quality of the arrester greatly affects the performance of the coil.
3. Calculation of the capacitance of the capacitor. Using the formula below, calculate the resonant capacitance for the transformer. The capacitor value should be approximately 1.5 times this value. Probably the best and most efficient solution would be to assemble the capacitors. If you don't want to spend money, you can try making your own capacitor, but it may not work and its capacitance is difficult to determine.
4. Manufacturing of a secondary winding. Use 900-1000 turns of 0.3-0.6mm enamelled copper wire. The height of the coil is usually 5 times its diameter. PVC downpipe may not be the best coil material available. A hollow metal ball is attached to the upper part of the secondary winding, and its lower part is grounded. For this, it is advisable to use a separate grounding, because when using common house grounding, there is a chance to damage other electrical appliances.
5. Manufacturing of the primary winding. The primary winding can be made of thick cable, or better still, copper tubing. The thicker the tube, the less resistive losses. 6mm pipe is sufficient for most coils. Remember that thick pipes are much more difficult to bend and copper will crack with multiple bends. Depending on the size of the secondary winding, 5 to 15 turns in steps of 3 to 5 mm should be sufficient.
6. Connect all the components, tune the coil and you're done!

Before you start making a Tesla coil, it is strongly recommended that you familiarize yourself with the safety rules and work with high voltages!

Also note that no transformer protection circuits have been mentioned. They have not been used, and so far there are no problems. The key word here is for now.

Details

The coil was made mainly from those parts that were in stock.
These were:
4kV 35mA transformer from neon sign.
0.3mm copper wire.
0.33μF 275V capacitors.
I had to buy a 75mm PVC downpipe and 5 meters of 6mm copper pipe.

Secondary winding

Secondary winding top and bottom covered with plastic insulation to prevent breakdown

The secondary was the first component to be manufactured. I wound about 900 turns of wire around a drain pipe about 37cm high. The length of the wire used was approximately 209 meters.

The inductance and capacitance of the secondary winding and the metal sphere (or toroid) can be calculated using the formulas that can be found on other sites. With this data, you can calculate the resonant frequency of the secondary winding:
L = [(2πf) 2 C] -1

When using a sphere with a diameter of 14 cm, the resonant frequency of the coil is approximately 452 kHz.

Metal sphere or toroid

The first attempt was to make a metal sphere by wrapping a plastic ball with foil. I couldn't flatten the foil on the ball well enough and decided to make a toroid. I made a small toroid by wrapping aluminum tape around a corrugated tube that was coiled into a circle. I was not able to get a very smooth toroid, but it works better than a sphere because of its shape and due to its larger size. To support the toroid, a plywood disk was placed under it.

Primary winding

The primary winding consists of 6 mm diameter copper tubes spirally wound around the secondary. The inner diameter of the winding is 17cm, the outer one is 29cm. The primary winding contains 6 turns with a distance of 3 mm between them. Due to the large distance between the primary and secondary windings, they can be loosely coupled.
The primary winding together with the capacitor is the LC generator. The required inductance can be calculated using the following formula:
L = [(2πf) 2 C] -1
C is the capacitance of the capacitors, F is the resonant frequency of the secondary winding.

But this formula and calculators based on it give only an approximate value. The correct coil size must be experimentally selected, so it is better to make it too large than too small. My coil has 6 turns and is connected on 4 turns.

Capacitors

An assembly of 24 capacitors with a 10MΩ damping resistor on each

Since I had a large number of small capacitors, I decided to assemble them into one large one. The value of the capacitors can be calculated using the following formula:
C = I ⁄ (2πfU)

The capacitor value for my transformer is 27.8 nF. The actual value should be slightly more or less than this, as a rapid rise in voltage due to resonance can damage the transformer and / or capacitors. Damping resistors provide little protection against this.

My capacitor assembly consists of three assemblies with 24 capacitors each. The voltage in each assembly is 6600 V, the total capacitance of all assemblies is 41.3nF.

Each capacitor has its own 10 MΩ damping resistor. This is important because individual capacitors can hold a charge for a very long time after the power has been disconnected. As you can see from the figure below, the rated voltage of the capacitor is too low, even for a 4 kV transformer. To work well and safely, it must be at least 8 or 12 kV.

Arrester

My spark gap is just two screws with a metal ball in the middle.
The distance is adjusted so that the arrester will only spark when it is the only one connected to the transformer. Increasing the distance between them can theoretically increase the length of the spark, but there is a risk of destruction of the transformer. For a larger coil, it is necessary to build an air-cooled arrester.

Instructions

Determine the type of coil you intend to make. Depending on conditions of use and coil design inductance are divided into low-frequency and high-frequency. For a low frequency coil, you need to make a magnetic core (core) from steel plates. In high-frequency coils, the core is either not used at all, or it is made of a non-magnetic material. Such a core allows changing its inductance without changing the turns of the coil.

Pick up the wire for winding the coil. As a rule, in both types of coils, copper wire of various cross-sections is used (copper has a low resistance). Select a wire with appropriate insulation, depending on the coil (in most cases, enamel insulation should be preferred). To reduce losses, coils used in the high-frequency part of the short-wave range are wound with bare wire.

Determine the diameter of the wire in order to evaluate the possibility of its application in the coil. In the absence of a micrometer, wind several tens of turns of wire on or another suitable rod (tightly, turn to turn), and then measure the total length of the winding with a ruler and divide by the number of turns. The more turns and the tighter the winding, the more accurate the measurement result.

Make a coil bobbin. In the design of homemade equipment, the frame can be made of paper, organic, cardboard. Make small-sized frames from photographic film, from which the emulsion must first be removed. Use multiple layers of film for stiffness. From the same film, make the cheeks of the frame, gluing them with celluloid glue.

Winding the wire on coil produce manually or on a special winding machine (depending on the type of frame and core). The coil, made on a ferrite ring, is wound using a special device (shuttle).

If it becomes necessary to solder the enamelled wire, remove it first. This can be easily done by holding the wire in the flame of a burning match, stripping it with a sharp knife or wiping the wire with cotton wool dipped in acetone.

Related Videos

Sources:

• Coils and transformers
• manufacture of inductors

The Tesla coil, also known as the Tesla transformer, is a unique device that is not at all like ordinary transformers, the condition of which is self-induction. For a Tesla transformer, it is quite the opposite: the less self-induction, the better. Very interesting and inexplicable effects appear when it works. But despite all the mystery, it is easy to assemble it yourself at home.

You will need

• Copper wires, plastic pipe, high voltage source, capacitor.

Instructions

Take a copper wire about 10 millimeters thick.

Next, take a piece of plastic about 50 millimeters in diameter and wind a coil on it, turn to turn, with a wire of 0.01 millimeters. The number of turns can be from 700 to 1000. This will be the secondary winding of the transformer, it is placed inside the primary. To start the device, it is necessary to supply high-voltage in the form of pulses to the primary winding of the transformer.

When the voltage is applied, the capacitor will start charging, as the voltage on its plates increases, until a breakdown occurs in the spark gap, then the voltage abruptly, and it will start charging again. This is the pulse shaping cycle applied to the primary winding of the transformer.

note

A voltage of the order of several thousand volts is applied to the primary winding. Remember that this is dangerous.

Helpful advice

By adjusting the capacitance, you can adjust the frequency of impulses, because the smaller the capacitance, the faster it charges, and by adjusting the gap in the spark gap, the voltage changes.

Sources:

• tesla how to make

Coil inductance is a coiled conductor that stores magnetic energy in the form of a magnetic field. Without this element, it is impossible to build either a radio transmitter or a radio receiver for wire communication equipment. And the TV that many of us are so used to without a coil inductance unthinkable.

You will need

• Wires of various sections, paper, glue, plastic cylinder, knife, scissors

Instructions

Magnetic cores concentrate the magnetic field of the coil, thereby increasing its inductance. At the same time, you can reduce the number of turns of the coil, which entails a reduction in its size and dimensions of the radio device.

Sources:

• Inductor

For the manufacture of some devices, it is necessary to use devices that convert currents and alternating voltages - transformers. In addition to step-down transformers, there may be a need for powerful step-up devices. One of such converting devices is the induction coil - the Rumkorf coil. Winding core an induction coil is a quite feasible task and does not require special knowledge or equipment.

You will need

• - copper wire with a diameter of 1.5 mm with double insulation;
• - threads;
• - paraffin;
• - cardboard or thin fiber;
• - wire PSHO or PE with a diameter of 0.1 mm;
• - paraffin paper;
• - insulating tape;
• - wire;
• - alcohol varnish

Instructions

Make a core. For these purposes, iron wire is suitable. Heat the wire until it is dark red, then place it in the hot ash and let it cool down. Clean off the incandescent thoroughly and carefully coat with alcohol varnish. Fold the wire into a bundle and wrap it tightly with electrical tape. Roll up several layers of paraffin paper.

When winding core you should first make the primary winding, and then the secondary, boost. Take the copper wire. Measure 10 cm, leaving this end free. Fasten the wire on the core, at a distance of 4 cm from the end with a thread.

Start winding the wire clockwise. Try to fit coil to coil as tightly as possible. Wrap the core completely with one layer of wire.

Make a loop. The length of the loop should be 10 cm. Secure the wire with thread. Wind the second layer of wire in the same direction. Secure the end of the winding securely with. Fill the entire wrapping with hot paraffin wax.

Take a thin fiber. If you do not have this material, then cardboard will do. The thickness of the cardboard sheet should be 1 mm. To improve the insulating properties, it is necessary to pre-boil the material in paraffin.

Craft 10 spools. The diameter of the inner hole of the coils must match the diameter core with primary winding.

Take insulated wire PSHO or PE. Wrap the secondary sections carefully. All sections should be wound in the same direction. The winding of each of the sections must be finished at a distance of 5 mm from the top board. Make a small puncture in this place in the coil cheek. Secure the wire, leaving an end 6-7 cm.

Carefully cover the wrapping with paraffin paper in several layers, and then with electrical tape.

Wrap the primary wrapping with 2 layers of paraffin paper. Carefully, in the correct order, slide on the sections of the second winding. Connect the ends of the winding sections in series.

Solder one piece of wire, 15 cm long, first to the beginning, and then to the end of the secondary winding. Fill the coil thoroughly with paraffin. Make sure that there are no voids left between the sections. The induction coil is ready.

Sources:

• Rumkorf coil in 2019

How good it is to go fishing early in the morning! The fresh smell of wildflowers, the chirping of birds and the first rays of the sun have a pacifying effect on the human psyche. To maintain this state of mind, you need to avoid any troubles while fishing. And for this, even the day before, it is worth taking care, including the correct winding cord on the spool of the fishing reel.

Tesla transformer is a device invented by Nikola Tesla and bears his name. It is a resonant transformer that produces high voltage at high frequency. The device was claimed by the US patent dated September 22, 1896, as "Apparatus for the production of electric currents of high frequency and potential."

Pros The simplest Tesla transformer consists of two coils - primary and secondary, as well as an arrester, a capacitor, a toroid (not always used) and a terminal (shown as an "output" in the diagram). The primary coil usually contains several turns of large diameter wire or copper tubing, and the secondary about 1000 turns of smaller diameter wire. The primary coil can be flat (horizontal), tapered, or cylindrical (vertical). Unlike conventional transformers, there is no ferromagnetic core. Thus, the mutual induction between the two coils is much less than that of transformers with a ferromagnetic core. The primary coil, together with the capacitor, forms an oscillatory circuit, in which a nonlinear element is included - a spark gap. The spark gap, in the simplest case an ordinary gas one, consists of two massive electrodes with an adjustable gap. The electrodes must be resistant to high currents flowing through the electric arc between them and have good cooling. The secondary coil also forms an oscillatory circuit, where the capacity of the toroid and its own turn-to-turn capacity of the coil itself play the role of a capacitor. The secondary winding is often coated with epoxy or varnish to prevent electrical breakdown. The terminal can be a disk, a sharpened pin or a sphere and is designed to produce predictable spark discharges of great length. Thus, a Tesla transformer consists of two coupled oscillatory circuits, which determines its remarkable properties and is its main difference from conventional transformers. For the transformer to work properly, these two oscillatory circuits must be tuned to the same resonant frequency. Usually, in the tuning process, the primary circuit is adjusted to the frequency of the secondary by changing the capacitance of the capacitor and the number of turns of the primary winding until the maximum voltage at the output of the transformer is obtained.

1. DIAGRAM OF THE TESLA TRANSFORMER

As you can see, there are a minimum of elements in this scheme, which does not make our task any easier. After all, in order for it to work, it is necessary not only to assemble it, but also to configure it! Let's start in order: MOTS: there is such a transformer in the microwave. It is a conventional power transformer with the only difference that its core operates in a mode close to saturation. This means that despite its small size, it has a power of up to 1.5 kW. However, there are also downsides to this mode of operation. This is a large no-load current, about 2-4 A, and strong heating even without a load, I am silent about heating with a load. The normal output voltage of the ILO is 2000-2200 volts at a current of 500-850 mA. All ILOs have a “primary” wound at the bottom, a “secondary” at the top. This is done for good insulation of the windings. On the "secondary", and sometimes on the "primary", the filament winding of the magnetron is wound, about 3.6 volts. Moreover, between the windings, you can see two metal jumpers. These are magnetic shunts. Their main purpose is to close a part of the magnetic flux created by the "primary" and thus limit the magnetic flux through the "secondary" and its output current at a certain level. This is done due to the fact that in the absence of shunts during a short circuit in the "secondary" (with an arc), the current through the "primary" increases many times and is limited only by its resistance, which is already very small. Thus, the shunts prevent the trance from overheating quickly when the load is connected. Although the ILO heats up, they put a good fan in the stove to cool it down and it does not die. If the shunts are removed, then the power delivered by the trance increases, but overheating occurs much faster. Shunts from imported MOTs are usually well sealed with epoxy and are not easy to remove. But it is still desirable to do this, the drawdown under load will decrease. To reduce heating, I can advise you to stick the ILO in oil. Amateurs, I ask you to give up this job. Danger High voltage. Deadly to life. Although the voltage is small compared to the line operator, the current strength, a hundred times greater than the safe limit of 10mA, will make your chances of staying alive practically equal to zero. I can upset some people by reporting that the ILO, although an ideal power source for Tesla coils (small-sized, powerful, does not die from HF like NST), but its price ranges from 600 to 1500 rubles and more. In addition, even if you have that kind of money, you will have to pretty much run around the radio markets and shops in search of him. Personally, I never found an imported ILO, not new, not used. But I found the ILO from the Soviet microwave "Electronics". It has a much larger size than imported ones and works like a normal trance. It is called from TV-11-3-220-50. Its approximate parameters: power about 1.5 kW, output voltage ~ 2200 volts, current 800 mA. Decent parameters. And on it, in addition to the primary, secondary and filament, there is also a 12 V winding, just to power the cooler for the Tesla spark. The author of our Tesla used the following motes:

CAPS: High-voltage ceramic capacitors are meant (series K15U1, K15U2, TGK, KTK, K15-11, K15-14 - for high frequency installations!) The most difficult thing is to find them. Introducing the composite sketch:

High-frequency filter: respectively, two coils that perform the function of high-frequency voltage filters. Each has 140 turns of lacquered copper wire 0.5 mm in diameter. Very clearly distinguishable in this figure:

Spark: Spark is needed to switch the power supply and excite oscillations in the circuit. If there is no spark in the circuit, then the power will be there, but there will be no fluctuations. And the power supply starts to siphon through the primary - and this is a short circuit! Until the spark is closed, the mouthguards are charged. As soon as it closes, oscillations begin. Therefore, they put ballast in the form of throttles - when the spark is closed, the choke prevents the current from flowing from the power supply, it charges itself, and then, when the spark gap opens, charges the caps with doubled anger. Yes, if there were 200 khz in the outlet, the spark gap would naturally not be needed.

Tesla coil is a flat spiral, which, along with inductance, has a large inherent capacity. The patent for the invention was filed in January 1894. The author, naturally, was Nikola Tesla. The transformer is widely known under this name, the principle of operation of the device is based on oscillatory circuits.

War of currents

Today it reads like a scientific novel, but at the turn of the 19th and 20th centuries, there was indeed a war of currents. It all started when the company did not pay a penny to the young Tesla for setting up a generator in Europe. Although the promised reward is solid. Without thinking twice, Tesla leaves his homeland and sails to the USA. On the path of the explorer, failures pursue, as a result, the journey ended well. Take the episode when all the money is lost on the road. Refuse? No!

Tesla miraculously makes his way to the ship and half the way is under the auspices of the ship's captain, who feeds the traveler in his own dining room. The relationship cooled a little when young Tesla was seen in the center of a scuffle that arose on the deck, where he handed out from the right and left, thanks to his impressive height (with a low weight). As a result, Tesla arrived ashore and on the first day managed to help a local merchant with a generator repair, earning a small reward.

With letters of recommendation in hand, Nikola goes to get a job in a company where he works day and night, spending time sleeping on a couch in the laboratory. Edison played a bad joke with the young future counterpart: he promised a solid reward for improvements in the operation of electrical equipment. The difficulty was quickly resolved, and the inventor of the lamp base thread cited a commercial joke. Tesla had already mentally distributed the promised reward for conducting experiments, and the joke did not evoke a warm emotional response from the inventor. The young immigrant leaves the company with the aim of starting his own.

At the same time, Tesla cherishes ideas for the fight against the fan of practical jokes. While walking with a friend, he suddenly realizes how to implement Arago's theory of a rotating field: two phases of alternating current are required. At the time of the 80s of the XIX century, the idea was considered truly revolutionary. Previously, motors, incandescent light bulbs (under development), and most laboratory experiments used direct current. This is what Georg Ohm did.

Tesla takes a patent for a two-phase motor and claims complex systems are possible. Westinghouse is interested in ideas, and a long story of righteousness begins. Edison, as usual, did not skimp on funds. There are stories that he took an alternator and tortured animals to death with it. The alleged electric chair was invented by Edison in collaboration with an unknown person. Moreover, the first designer accidentally or deliberately made a mistake, so much so that the convict suffered for a long time, to top it off, he literally exploded, splashing out the internal organs.

Westinghouse's lawyers managed to save the second poor fellow, replacing the execution with life imprisonment. Salvation did not stop Edison, who set out to invent a chair in addition to a table. Tesla tried to demonstrate a retaliatory move, putting forward a number of arguments:

Enterprising American businessmen even issued playing cards, which featured the aforementioned war of currents. For example, the famous Wardencliff tower is placed on the image of the joker, science fiction writers and directors of similar films were guided by the structure. Historical facts clarify how intense the struggle turned out to be - the reason for the brilliance of inventive genius. The Tesla coil, twisted of 50 turns of thick cable, was structurally part of the Wardencliff tower ...

Tesla coil design

This is an amazing opportunity to save on capacitor units by laying the coils of copper wire in a special way. If readers are in the subject, they've heard about phase correctors to reduce energy costs. These are capacitor units that compensate for the inductive resistance of the consumer. Especially relevant for transformers and motors. Excessive spending is shown only by the reactive power meter. This is an imaginary energy that does not perform useful work for the consumer. Circulating here and there, it heats up the active resistances of the conductors. In areas where full capacity metering is kept (for example, enterprises), this significantly increases bills for payments to electricity suppliers.

Now it is easy to understand how Tesla's invention was planned to be used in industry. The inventor, in US Pat. No. 512340, cites two similar coil designs:

• The first drawing shows a flat spiral. One lead of the Tesla coil is located on the periphery, the second is taken from the middle. The design is easy to operate. With a potential difference between the terminals of 100 V and the number of turns in a thousand, on average, 0.1 V falls between adjacent points of the spiral. To calculate the figure, divide 100 by 1000. The intrinsic capacity is proportional to the square of 0.1 and will not be too large.
• Then Tesla offers to look at the second drawing, where the bifilar coil is presented. It is a flat spiral, but the two wires are twisted side by side. Moreover, the ends of the second circuit are short-circuited and connected to the output of the first one. It turns out that the alternative filament has the same potential along its length. If you imagine that 100 V is applied to the structure, the result will change. Indeed, now there are wires of two different threads running nearby, and on the only one in length - only zero. As a result, on average, the potential difference is 50 V, and the intrinsic capacity of the Tesla coil is 250,000 times larger than that of the previous circuit. This is a significant difference and it is obviously possible to find advantageous network parameters. For example, Tesla worked at frequencies of 200 - 300 kHz.

The inventor indicates that he has tried various shapes and configurations. In terms of utility, the square does not differ from the circle or rectangle shown in the figures. The designer is free to choose the shape. Tesla coils are not widely used today. Entrepreneurs opposed the inventor. The conversation that took place between the businessmen and Edison is unknown, but, being listed as shareholders of the new hydroelectric power station, the tycoons heard that the Vordencliff tower, built in a convenient place, could become the first bird in the transmission of energy over distances without wires.

The construction sponsor was the owner of the copper factories and just wanted to sell the metal. The wireless method of transmitting power is disadvantageous. If J.P. Morgan had known that today most of the cables are made of aluminum, he might have reacted differently, but it turned out that Nikola Tesla was completing the tower in splendid isolation, and the design did not take the intended scope.

According to the second version, Nikola Tesla conceived to create energy out of thin air, which they gossip about on YouTube. A certain inventor proves that the ether energy is drawn into the core of the magnet, at an equal distance from the poles, and it is required to be able to convert it into electricity. Tesla's idea is briefly stated. The self-taught master, who dared to present a 13 kW free energy generator at the exhibition, disappeared in an unknown direction along with his family. Facts like this suggest that the Wardencliff Tower has far more opponents than is commonly thought.

Tesla envisioned 30 factories in the world. They would generate and receive energy, broadcast broadcasts. Apparently, it was considered that this would be the collapse of the local economy, although Bedini engines are still being built using Tesal's theories. So, the coils were at the heart of the transmitting and receiving devices: the design is identical. But today these curious inventions are reliably forgotten, except for microstrip technologies, where square and round spiral inductors of a similar kind meet.

Tesla transformer

It was said above that Tesla coils were at the heart of the transmitting devices, it is permissible to call resonant transformers. A high potential is pumped into the Tesla coil by means of a transformer coupling. The charge goes on until the spark gap breaks down, then oscillations begin at the resonant frequency. If one transformer coupling through a coil with a large number of turns transfers high voltage to the emitter or arrester.

Anyone is free to make sure that the design of the Wardenclyffe tower resembles a mushroom, but at the base is a flat Tesla coil. A large-volume torus with capacitive resistance is used as an emitter. In its modern form, the intermediate circuit contains conventional capacitors, tuned to the parameters of the "donut". A great advantage of the design is the absence of ferromagnetic materials.