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Tesla Tube Coil

Hamsters welcome you friends.

Today's post will be about high voltage. Tesla Tube Transformer is the quietest construction of all existing options. Here, a powerful pentode GK-71 is used as a generator of high-frequency oscillations, thanks to which it is possible to obtain beautiful, fairly long discharges in the air. In the course of this work, we consider the main structural elements, learn the secrets of setting up the circuit, and visualize the signal from the high-voltage winding to the screen of a Soviet oscilloscope. Further work will consist in the compact placement of all elements in one housing. In general, everything is as you like. Simplicity, reliability and low cost make this coil available to anyone who wants to assemble it.



The beauty of Tesla's lamp coil is that one part of the parts for it can be taken out of a conventional microwave, and the second from the nearest electrics store. There may be a problem with the pentode, the thing is old and has not been released for a long time, but the one who seeks will always find it. In the future, you will understand that it can be replaced with any other lamp of a similar design.



GK-71 is selected due to aesthetic beauty and low cost. Who did not pay attention, the anode in this evacuated tube is completely composed of graphite, a good implementation for dissipating large powers, according to the passport data, this figure is 250 watts. The nominal anode voltage is 1.5 kilovolts. The maximum frequency is 20 MHz.

This copy was released in 1981. Got a new one right out of the box. Continuous working time on documents is 1000 hours. This is approximately 42 days. In a year, on a constantly working device, it is necessary to change 8 such comrades. According to some estimates, the GK-71 Lamp produced at one time will last for at least another 200 years.



Glow is the part that breathes life into any radio tube.The voltage for the GK-71 pentode is 20 volts, but the current should be at least 3.5 amperes. In general, the glow is 70 watts. A domestic transformer TN54-220-50 was purchased on the market for a symbolic amount. With the correct connection of the windings, you can get 85 W from it without any financial costs.



The next element is a high-voltage transformer from a microwave; bourgeois call it the ILO. The voltage at its output is 2 kilovolts, the current is about 1 ampere. A rather powerful and dangerous thing can send you to a meeting with the creator, so do not get carried away.



The following is a brief list of the elements needed to assemble the structure:
2 oil capacitors from the same microwave, voltage 2.1 kV, capacitance 0.95 uF. HYR-1x diode assembly, its maximum allowable voltage is 12 kV, current 500 mA, according to the passport it is able to withstand a pulsed current of up to 30 amperes. A real beast of its kind. Resistors like PEV-10-20 W, you can use any other analogs of bourgeois production.

Resonant high-frequency capacitor type KVI-3, the voltage can vary from 5 to 20 kV, several such comrades with different capacities on board were purchased for tuning. For winding the inductor, a multicore copper wire of the PVA type was purchased, section 1.5 square. The length is about 16 meters. The communication coil has a different color and length of 10 meters. All wires are taken in length with a margin.

Knife switches commuting power units, took with an allowable current of up to 15 amperes, do not ask why so much, the stock pocket is not tight.



Now the secondary high-voltage winding, it is also a "resonator". Winding up this detail takes a lot of time and patience. Here a copper lacquered wire 0.2 mm thick was used, a coil is wound to a coil on a cardboard basis from food wrap. The diameter of the pipe is 55 mm. The winding height was 35 cm. The turns in this case should not intersect and overlap each other.

After winding procedures, the result should be covered with a dielectric layer to avoid breakdown of the winding.Epoxy is applied in two layers for reliability. As a result, a glossy, iridescent tube will come out, which will take away part of your precious life. A second duplicate of the coil was wound on a 50 mm diameter plastic sewer pipe. PVC is a more reliable dielectric, we will soon see this. The frame for the inductor was taken from the same cardboard only with a larger diameter, about 80 mm.



For further work, it is necessary to place transformers, capacitors and other nonsense on some solid basis as compactly as possible. Particleboards have been lying around for a long time, so you should mark them up and use a jigsaw whose operation and sounds nobly affect the life of your neighbors, especially on weekends.

The design will be two-story.Below, transformers with capacitors will be placed, and on top we will place the Pentode and the Tesla coil itself. Long thought how to fasten the first floor with the second, I decided to use wooden caps. Reliability here of course turned red and went to drink after conscience. Some kind of jelly. We put on pink glasses and saw a hole under the radio lamp. Then, on the reverse side, we make holes for the wires.



Now about the inductor. Now we do not know exactly how many turns are needed, we wind 40, when setting it up, you still have to wind it down to find resonance. The feedback winding is wound in one direction with the inductor. The number of turns is two times less, that is 20. This ratio is found in many Tesla tube coils.

A moment that did not quite understand.In some circuits, the coupling winding is located at the bottom of the Tesla transformer, where the highest currents develop, and in some, above the inductor. I don’t know which location option is better, but in this scheme it is placed on top.



We could not find a socket for installing a pentode, a rather rare thing, because the mounting alternative is a terminal block for a wire with a hole diameter of 4 mm. The clamps in it perfectly fix the legs of the pentode. Plywood, which was a magnet on the refrigerator door, was used as a decorative stand.

Now is the time to connect the wires to the glow transformer, and see if everything works.We feed and observe the ammeter. 3 amperes, as prescribed by the passport. As it warms up, the current consumption drops slightly. The camera, alas, could not convey all the beauty of the red-hot strings inside this glass eggplant. Hefty lamp ... Well, they knew how to do it!



The whole circuit of the device is quite simple and looks something like this:AC high voltage from the motor is rectified through the diode and charges the capacitors from the microwave, they are connected in series to increase the operating voltage. In this case, the total capacity goes half a microfarad. The oscillatory circuit of the inductor is connected to the anode of the lamp through a throttle consisting of 10 turns. All control grids of the GK71 lamp are connected together, from this moment the pentode turns into a triode. The oscillator circuit starts to work at very low voltages at the input of the motor. The 2.2 nF capacitor at the output of the filament transformer serves to filter crosstalk and high-frequency emissions, although the first = second, the second = first, somehow. We pay attention to the connection of the windings in the primary circuit. The point is the bottom terminal of the winding.



In principle, the assembly turned out to be quite compact.Her work can easily be demonstrated in physics classes, remembering the life of that dude, thanks to whom we have alternating voltage in sockets.

Tesla Transformer requires good grounding. The battery is not the best solution for these matters, but in the absence of anything more suitable, it will do. The contact must be reliable, three meters of wire should be enough to reach anywhere within the same room.

In new homes, such a trick may not pass due to plastic pipes in the heating system. Therefore, we check the presence of voltage between the phase and ground, it should be 220 volts. Some allow grounding through grounding, also a suitable option. There is a potential of 3.7 volts between zero and ground, Creosan recently talked about how you can steal electricity in this way, charge the phone and turn on the light bulbs, but I just forgot to mention the fact that modern digital meters count energy consumption both in phase and in zero. The maximum that you win is the visit of the inspector to visit you.

So, turn on the power of the filament circuit. The lamp enters the mode quickly enough, 5 seconds is enough for this matter. The second switch supplies power to the mot.In no case should you apply a high voltage to the anode of the lamp, without the glow on. The input voltage on the motor is regulated by LATR, it gives a voltage from zero to 220 volts. An irreplaceable thing in working with similar schemes. We increase the voltage and see that the generator is working. With the advent of the high-frequency electric field, the LED lamp mounted under the shelf starts to glow a little and blink.



At the tip of the screwdriver, which serves as a terminal for the exit of lightning, a small streamer appeared.As the voltage increases, its size grows, but the discharges are somehow thin and not impressive. Change the position of the connection winding, move it a little down. We look at what has changed in the work. Gradually increase the voltage ... we see that the discharges have become more confident, thicker, longer and brighter. The sound is pretty impressive, like a dull roar of a sports car.

The search for resonance was carried out either by unwinding the coils, or by selecting a resonant capacitor. He began to unwind coils. An increase in discharge power indicates that we are on the right track. The discharges are more powerful, thicker, longer, the most interesting thing happened when I began to increase the capacitance of the resonant capacitor. The discharge increased, and in the eyes began to decrease. It smelled of burning paper.



A detailed examination revealed that the cardboard began to burn.And if a small burnout appears, then it gradually turns into a large one, since the carbon obtained as a result of the combustion of something becomes an excellent conductor. In general, this is gangrene, which must be immediately amputated. We get rid of the problem area using a hacksaw for metal. A couple of minutes, the problem is solved, and the hand is pumped up.

Since the resonant circuit changed its characteristics by reducing the length of the secondary coil, again we roll and unwind the coils of the primary. Power is increasing. The mood is excellent, a couple of seconds of joy and the design begins to fail. Resales breaks into the primary. The windings are too close to each other. Assumptions were that this could happen, but not so fast. The first day of setup, and many hours of work is sent to the trash. If desired, this pipe can be cut in half, and make for example a Brovin kacher on a transistor.



At first I wanted to isolate the secondary with a plastic bottle, but as practice shows, this collective farm does not lead to anything good.We dress up sneakers and move to the nearest plumbing store behind a 10-cm drain pipe. Such a diameter will reduce the coupling coefficient of the windings, which is good in this design. The dielectric ability of such a cylinder is much better than that of ordinary cardboard.

We wrap a layer of paper over the pipe, we lay the turns of the inductor and the windings of communication on it.Paper allows you to safely move the windings along the entire length of the pipe. It is convenient to install the coils on the plugs, they come from the same plumbing store and allow you to observe the alignment of the entire resonant circuit. A little effort and the design is ready for work again. Repeat the inclusion procedure. At the beginning we apply power to the glow, wait a couple of seconds, and then turn on the anode voltage. It is now at zero and regulated by a laboratory autotransformer. Turn it on and gradually raise the voltage.

Discharges with an increase in the coupling coefficient have become larger and more beautiful. At this point, it was probably worth completing the post, the circuit worked, the discharge we saw. But according to tradition, this is just the beginning.



For the final and more correct operation, the oscillator must be configured on an oscilloscope.We will configure the system according to the maximum signal amplitude. We will not connect the oscilloscope probe directly to the circuit; to configure it, place it at the level of the torus and watch the broadcast signal. All interference, waveform, frequency and amplitude of the signal will be displayed on the oscilloscope. In this scheme, this information will be more than enough to configure. Turn on the glow. We apply anode voltage. We regulate the voltage with an autotransformer ... but for some reason nothing happens ... we understand what is wrong !? Yeah, we forgot to connect the ground, it happens, we fasten it in its place and repeat the switching procedure. Turn the knob and the signal comes to life. This is our indicator in the world of customization. The input voltage on the mote is only 50 volts, excellent, we do not need discharges in the air right now.

An alternative to detecting high-frequency fields is an ordinary neon bulb. The amplitude of the signal cannot be determined by it, but it can be judged on the operability of the device as a whole, whether it is correct or not - this is another matter.

So, during the setup process, we managed to identify two interesting operating modes. The first is a smoothly damped pulse with a small amplitude, in contrast to the second mode. Now we transfer the wires to different turns of the inductor and observe how the signal changes. Attention is a question for connoisseurs. What mode of the oscillator gives the greatest discharges: option “a” - with a smoothly damped signal, but small amplitude, or option “b” - with a large amplitude, but short pulse?



Resonance tuning with capacitors.These samples have different capacities, how to choose the right one? It's simple, we alternately connect the capacitors parallel to the inductor and look at the signal. One must be careful in this case, large currents develop here that can cause fatality to your hand. Dead electronic engineers do not need anyone. If the capacitance is too large, it simply dampens the entire amplitude of the signal.

At the beginning of the release, I promised to tell why such massive contacts on capacitors are needed. During operation, especially at resonance, huge currents develop in the inductor, on the order of several hundred amperes, if such a current goes through the thin legs of a conventional capacitor, they simply blow out like a jumper in the fuse. In this circuit, the KVI3 capacitor at 1500 pF 10 kV took root well. Year of release 1978, a rarity of its kind, 10 years older than me.

The oscillator circuit operates in a forced interrupt mode with a network frequency of 50 Hz, if the damped oscillations are stretched in time, the frequency of the oscillator can be calculated. We synchronize this old junk and proceed to the calculations.



Now, the division time switch on the oscilloscope is in the 0.5 µs position. This means that one cell on the screen scale is 0.5 μs. One period of a sinusoid takes 5 cells, therefore 5 times 0.5 we multiply equal to 2.5 μs. The frequency is found by the formula: 1 divided by period. We count. 1 / 2.5 μs equals 0.4 MHz, which equals 400 kHz. Hence the conclusion, the resonant frequency of the tuned Tesla coil is 400 kHz.

Calculations could be more accurate with modern equipment, but for this scheme it is simply not needed.After setting, we adjust the position of the inductor and the coupling winding so that the signal amplitude on the oscilloscope is maximum. At this stage, the setting of the Tesla lamp coil can be considered exhaustive. The power consumption of the circuit without a glow circuit is 720 watts.



There is something surprising in the operation of the lamps when you pick them up and return to those distant warm times. Transistors and other modern electronics become boring over time, becoming boring. You can look at the lamp forever, or for 1000 hours until the electron emission disappears and the cathode becomes impoverished. Now is the time to see how it all works.



During the operation of the circuit, the lamp does not overheat and can work for a long time, say 10 minutes without interruption. But there are craftsmen who put multi-quantitative assemblies of microwave capacitors at the output of the motor, the power of the circuit increases, the lamp starts to work at the limit of its capabilities. Naturally, the graphite anode of the lamp heats up to red, the cathode consumes its life. This mode will work, but not for long.

To increase the lamp life at high powers, breakers are used. This is roughly a switch that briefly starts the Tesla generator. A second of work, a second of rest, something like that. Modes can naturally be changed.



The glow of various light bulbs in high-frequency electric fields is generally a separate issue, some samples are so beautiful that they claim a separate post.



We heard about the fact that various salts can be used to tint the color of the fire, now let's check it in practice. To do this, take ordinary table salt and dilute it with a small amount of water. The resulting porridge is applied to the electrode. Sodium ions should tint lightning in orange color, and now we will see.



This design is easy to repeat, and elementary to set up. There are no expensive parts in it, although the price is a relative matter, the cost of all elements is about 65 bucks not including LATR for adjusting the input voltage in the anode circuit.

In one of the following posts, we will consider a semiconductor system, there we will learn how resonance is calculated, how to control iron and other nonsense that is little-known to a normal person.



For reference. The filming of today's release, along with post processing, writing, and other processes, took 2 months. This can be called a quick release. In the comments you often write that we shoot material in the field of physics and electronics, this is happening now, but there is a flip side to the coin, time. Now the issues will come out less often than usual, I hope you understand everything.

As popular wisdom says: work and labor will grind everything.


Full project video on YouTube
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