How to make a powerful ladder Jacob transformer from the microwave with his own hands

The desire to write this post was prompted by this photo from the student conference of the technical university.



- Seen what the students showed at the conference? - asked comrade, showing a photo.
- Wow! This is a full *****! And you were there?
- Yes, I approached them, talked, but they did not listen to me. What could I do???

And indeed, what can you do. After talking with friends, it was decided to write this post, in which we will tell you a little about “Jacob’s Ladder”, our own experience in making these installations, and explain why this photo caused so much emotion.



Jacob's Ladder is an installation consisting of a high-voltage power supply unit and two electrodes located in a vertical plane at an angle to each other. So the bottom distance between them is less than the top, and was chosen depending on the voltage of the power source, so that the air breakdown between the electrodes occurs independently. During its operation, the formation and movement of an electric arc from the bottom (bottom) to the top of the electrodes can be observed. This effect is explained by the fact that the arc consists of plasma heated to 5000–7000 ° C, it heats the air around it and, thanks to the convection currents of the heated air, rises upward, drawing the arc cord with it. If you take a long exposure shot of a discharge, you can get an unusual photo (see above), which will resemble a staircase from biblical history:


Landscape with a dream (from a dream) Jacob, Michael Vilman, apprx. 1691

Jacob's ladder spectacularly demonstrates a whole chain of physical phenomena. And I cannot remain indifferent to this installation, since I love physics, since student times I have been a staunch popularizer of science, and in recent years I have been developing exhibits for science museums. Some readers of Habr will probably remember that we made the largest Tesla coil in Ukraine . Those who read the article noticed that the most attention was paid not so much to the manufacture of the coil itself, but to security issues.

In the photo at the beginning of the post, we see how the bare electrodes are directly accessible to the conference participants. Anyone who accidentally (out of curiosity) touches the electrodes is likely to die. However, Sergei Alexandrovich, a hobby player with a vast experience in manufacturing Tesla coils, Jacob's ladders, ionophones, voltage multipliers, and just a big fan of transformers of all shapes and sizes, will tell you better about the obvious and unobvious dangers of high-voltage installations :)

On Habré he under the nickname Frost273 , this, by the way, he is the author of the largest Tesla coil in Ukraine. Next will be its text.

It can be said with confidence that every modern person, in a given situation or another, has come across phenomena of electricity, and sometimes not when he himself desired it. If we take into consideration the young (if not already body, then soul) and bearded (are there any girls who are fond of electrical engineering?) Techies, namely, they are primarily attracted by the title of the article, then there is no one who has not experienced an electric shock, whether it is a disassembled power supply, or not a discharged capacitor, the fact remains. And since you, friend, are now reading this article, it means that you are still alive, and you can tell about your experiences in the comments.

However, with some working electrical installations, inattention becomes the last mistake in life. Experiment with the manufacture of Jacob’s ladder is also a dangerous class of devices.

Especially Jacob’s ladder, “in the heart” of which there is a high-current power source, is a microwave transformer, which can deliver under 500 mA (0.5 amps) depending on the microwave oven model.

And now, for a moment, the table, to refresh the memory of such a familiar subject as OBZH.


The impact of electric current on a person

And I am ready to confirm that even such small quantities of alternating current flowing through the fingers of 0.001 amperes (1 mA) can hardly seem like a pleasant sensation to anyone. And the more unpleasant this feeling will be, the more suddenly it will arise. This I found out when I was a teacher in a higher educational institution, when I had the desire and audacity to diversify the lessons of electrical engineering for 3rd year students by conducting applied experiments with electricity.

Returning to the table, you can see that for any alternating current flowing through the body of more than 15 mA there is a threat to the health and life of a healthy person. A person who has heart defects is already at risk for smaller values.

I also want to note that the variation in the values ​​in the table, for example, for non-release currents (10 ... 15 mA), depends on a combination of five additional factors, in addition to the magnitude of the current itself:

• voltage;
• the resistance of the skin of the person (there is also affected by damage to the skin and the contact area);
• duration of exposure (counting goes on a fraction of a second);
• frequency of electric current;
• flow path through the body .

From the last point it follows that the current will flow through the body and vital organs only in the case when there are two points of contact with different potential. As an example, I think you can all remember how the birds were seen sitting on the wires of power lines, while there could be as much as 380 V and 10 kV or higher. Such invulnerability of wildlife objects that are in direct contact with the wires is due to the fact that they acquire the electrical potential of the wires and the current does not flow through them. And in connection with the dimensions of the birds, the magnitude of the leakage current through the surface of their bodies into the environment is safely small. Mortality occurs only when the bird wants to clean the beak of the traverse. Alas, such incidents have frightening proportions . Even distracted ...

I wanted to convey the idea that in this topic there is no place for the romanticization of death from an electric shock. The experimenter with a probability of 100% will not be Dr. Manhattan.



Yes, and soon will be no one, although it is not accurate. Since the chance to stay alive, though small, but there is. But the high probability of which there is is:

1. To experience irregularities in the work of the cardiovascular system, respiratory system, nervous system ...
2. Get an electric burn (a harmonious combination of heat and chemical burns).
   With an electric shock, the resistance of our body does not play into our hands, because a sufficiently large amount of current in the tissues is converted into heat, which causes coagulation necrosis at the points of entry and exit on the skin, as well as in the muscles and blood vessels through which current flows. That in turn leads to the development of thrombosis, often in places remote from the surface of the body, which significantly slows down the process of tissue regeneration. Moreover, the blood plasma itself undergoes electrolysis when current flows, which makes it unsuitable for performing its direct functions of transporting oxygen.
   
   In addition, there is a danger of clothing ignition when in contact with an electric arc. And imagine how uncomfortable it is to extinguish your clothes with paralyzed limbs.
   
   
   Photo of the affected by the electric current of the human body (there is censorship)
   
   One should not expect that the electric arc will leave a beautiful burn in the form of a Lichtenberg figure on the surface of the body, since such a form of damage is possible only when struck with static electricity, following the example of a thunderstorm lightning.
   
   I want to remind you that the level of voltages used in the experiment “Jacob’s ladder” is initially focused on the formation of an electric arc.
3. Get retinal burns as a result of exposure to harsh ultraviolet radiation from an electrical discharge.
   
   I have to admit that I used to indulge in this device myself, of course, observing safety measures, and additionally equipped with UV protection glasses, but the unprotected parts of my face that had not seen the sun during the long winter months remained completely unaesthetic. spotty tan.

Something like this.

Now, reader, hang one's curiosity on one side of the scale, and on the second the features of the ladder-Jacob-structure listed above. Wouldn't it be safer to watch a vidosik with electricity on a cozy YouTube?

Preparation for assembly

If you are still determined to try your hand at making this wonderful installation, here are the first necessary points:

Item 0 (main). Do not use mot
Item added as recommended by Neuromantix , lorc and Firelander

The ILO (Microwave Oven Transformer, or a microwave transformer) is an incredibly dangerous device. Do not use it ever! The use of other high voltage sources with less current will significantly reduce the likelihood of killing someone. Nevertheless, the danger of causing irreparable harm to health remains.

Point 1. We select insulation



This may not be obvious, but the usual insulating materials that will perfectly cope with voltages up to 500 V stop working at kilovolts. At high voltages, paper, wood, plywood, chipboard, fiberboard, cardboard, and even dust on the PCB surface can become conductors! Wires must also be selected with insulation designed for appropriate voltages. So, the cable from the extension is not suitable!

Point 2. Prepare the room

It is necessary to assemble the installation on a dry, non-combustible, non-conductive floor. There must be empty space around the installation so that in the event of electrodes falling, nobody and nothing will suffer. Here is an instructive video where the installation was going on the table and fell right on the experimenter:



Fortunately, due to the flimsy attachment of the electrodes, the chain broke and the hero of the video did not have time to die. However, not everyone is so lucky, just recently the news slipped, as a schoolboy was killed when self-assembling Jacob's stairs in the garage . Neither cats, dogs, birds, nor other animals can be kept indoors. At the most inopportune moment, they can hook up / overwhelm the installation, divert, or corny to the wires.



And the most important thing is that none of the outsiders have the physical ability to get into the room, and not only for the period of work, but also for the time while the installation is there.

Item 3. Building

It is necessary to think over the design of the case in advance so that no one physically could touch the electrical components of the operating installation, especially the electrodes. When we made Jacob’s first ladder for the center of science, we placed it behind the lattice with the lock and behind the glass:



When there is no separate room, we assemble the installation in a protected building, with the following rules:

1. A source with a current up to 30 mA is used.
2. Installation is removed from the observers, they can not touch the body.
3. Next to the installation is always the person in charge.

Item 4. Do not work alone

First of all, it is necessary that in all test launches there should be a person who is ready to de-energize the installation and to provide emergency medical care. Secondly, there must be an adult who is ready to take responsibility for fire, injury, or even death, which can occur under unfavorable circumstances.
Perhaps this is not a complete list, I invite you to add it in the comments, I will add important points to the article.

Schemes, and assembly instructions

Forgive me, dear reader, I deceived you - there will be no instructions and schemes, and I am not at all ashamed. I am sure that this is all you can easily find on the Internet. The design is so simple that any student can assemble it. However, before you start assembling, ask yourself, are you ready for the fact that your loved one may suffer?

PS
Yes, the title is yellow, and the post does not carry new information for the target audience of Habr. Nevertheless, I hope that the article will take a worthy place in the search results and will be read by many enthusiasts, and perhaps even save the experimenter from death.

UPD 1: The first findings of the survey and comments

As of 23:59 14.06, the results of the survey are as follows:



It may seem that everything is not so scary - people are beaten by high voltage and everyone is alive and healthy, especially since 77 comments confirm this. However, this is not quite true. Because there is a survivor's mistake , because only the survivor could tell about their experience. Moreover, I carefully read the comments and could not find a single case when someone was hit with a high voltage for real. Overwhelmingly in the comments share the experience of contact with 100-220 V. Only a few have experienced a very short-term blow from the discharge of a capacitor, which is not as bad as continuous contact with the secondary ILO.
I should add that only one person I knew had experience of interaction with high voltage. When we were children, he made his way to the substation ...
... He was dying very painfully from a huge amount of burns in about 15 minutes. And it looked awful. Perhaps that’s why I’m painfully concerned about a severe violation of TB.