Wireless transmission for delivering electricity has the ability to deliver major advances in industry and applications that depend on the physical contact of a connector. It, in turn, can be unreliable and lead to failure. The transmission of wireless electricity was first demonstrated by Nikola Tesla in the 1890s. However, it has only been in the last decade that technology has been used to the point where it offers real, tangible benefits for real-world applications. In particular, the development of a resonant wireless power system for the consumer electronics market has shown that inductive charging brings new levels of convenience to millions of everyday devices.

The power in question is widely known by many terms. Including inductive transmission, communication, resonant wireless network and the same voltage return. Each of these conditions essentially describes the same fundamental process. Wireless transmission of electricity or power from a power source to load voltage without connectors through an air gap. The basis is two coils - a transmitter and a receiver. The first is excited by an alternating current to generate a magnetic field, which in turn induces a voltage in the second.

How the system in question works

The basics of wireless power involve distributing power from a transmitter to a receiver through an oscillating magnetic field. To achieve this, the direct current supplied by the power supply is converted into high frequency alternating current. With specially designed electronics built into the transmitter. The alternating current activates a coil of copper wire in the dispenser, which generates a magnetic field. When the second (receiving) winding is placed in close proximity. The magnetic field can induce an alternating current in the receiving coil. The electronics in the first device then converts the AC back to DC, which becomes the power input.

Scheme of wireless power transmission

The "mains" voltage is converted into an AC signal, which is then sent to the transmitter coil via an electronic circuit. Flowing through the winding of the distributor, induces a magnetic field. It, in turn, can spread to the receiver coil, which is in relative proximity. The magnetic field then generates a current flowing through the winding of the receiving device. The process by which energy is distributed between the transmitting and receiving coils is also referred to as magnetic or resonant coupling. And it is achieved with the help of both windings operating at the same frequency. The current flowing in the receiver coil is converted to DC by the receiver circuitry. It can then be used to power the device.

What does resonance mean

The distance over which energy (or power) can be transmitted increases if the transmitter and receiver coils resonate at the same frequency. Just like a tuning fork oscillates at a certain height and can reach its maximum amplitude. It refers to the frequency at which an object naturally vibrates.

Benefits of Wireless Transmission

What are the benefits? Pros:

• reduces the costs associated with maintaining direct connectors (for example, in a traditional industrial slip ring);
• greater convenience for charging conventional electronic devices;
• secure transmission to applications that must remain hermetically sealed;
• electronics can be completely hidden, which reduces the risk of corrosion due to elements such as oxygen and water;
• reliable and consistent power supply to rotating, highly mobile industrial equipment;
• provides reliable power transmission to critical systems in wet, dirty and moving environments.

Regardless of the application, eliminating the physical connection provides a number of advantages over traditional cable power connectors.

The efficiency of the considered energy transfer

The overall efficiency of a wireless power system is the single most important factor in determining its performance. System efficiency measures the amount of power transferred between the power source (i.e. wall outlet) and the receiving device. This, in turn, determines aspects such as charging speed and propagation range.

Wireless communication systems vary in their level of efficiency based on factors such as coil configuration and design, transmission distance. A less efficient device will generate more emissions and result in less power passing through the receiving device. Typically, wireless power transmission technologies for devices such as smartphones can reach 70% performance.

How efficiency is measured

In the sense, as the amount of power (in percent) that is transmitted from the power source to the receiving device. That is, wireless power transmission for a smartphone with an efficiency of 80% means that 20% of the input power is lost between the wall outlet and the battery for the gadget being charged. The formula for measuring work efficiency is: performance = direct current outgoing divided by incoming, the result obtained multiplied by 100%.

Wireless methods of power transmission

Power can be distributed through the network under consideration in almost all non-metallic materials, including, but not limited to. These are solids such as wood, plastic, textiles, glass and bricks, as well as gases and liquids. When a metallic or electrically conductive material (i.e. placed in close proximity to an electromagnetic field) the object absorbs power from it and heats up as a result. This in turn affects the efficiency of the system. This is how induction cooking works, for example inefficient power transfer from the hob creates heat for cooking.

To create a wireless power transmission system, it is necessary to return to the origins of the topic under consideration. Or, more precisely, to the successful scientist and inventor Nikola Tesla, who created and patented a generator that can take power without various materialistic conductors. So, to implement a wireless system, it is necessary to assemble all the important elements and parts, as a result, a small device will be implemented. This is a device that creates a high-voltage electric field in the air around it. At the same time, there is a small input power, it provides wireless transmission of energy at a distance.

One of the most important ways to transfer energy is inductive coupling. It is mainly used for near field. It is characterized by the fact that when current passes through one wire, a voltage is induced at the ends of another. Power transfer is done by reciprocity between the two materials. A common example is a transformer. Microwave energy transfer, as an idea, was developed by William Brown. The whole concept involves converting AC power to RF power and transmitting it in space and re-to AC power at the receiver. In this system, the voltage is generated using microwave energy sources. such as klystron. And this power is transmitted through the waveguide, which protects from the reflected power. As well as a tuner that matches the impedance of the microwave source with other elements. The receiving section consists of an antenna. It accepts microwave power and an impedance matching circuit and a filter. This receiving antenna, together with the rectifying device, may be a dipole. Corresponds to the output signal with a similar sound alert of the rectifier unit. The receiver block also consists of a similar section consisting of diodes which are used to convert the signal into a DC alert. This transmission system uses frequencies in the range of 2 GHz to 6 GHz.

Wireless transmission of electricity with the help of which the generator realized using similar magnetic oscillations. The bottom line is that this device worked thanks to three transistors.

The use of a laser beam to transmit power in the form of light energy, which is converted to electrical energy at the receiving end. The material itself is directly powered using sources such as the Sun or any electricity generator. And, accordingly, implements a focused light of high intensity. The size and shape of the beam are determined by the set of optics. And this transmitted laser light is received by photovoltaic cells, which convert it into electrical signals. It usually uses fiber optic cables for transmission. As with the basic solar power system, the receiver used in laser-based propagation is an array of photovoltaic cells or a solar panel. They, in turn, can convert the incoherent into electricity.

Essential features of the device

The power of the Tesla coil lies in a process called electromagnetic induction. That is, the changing field creates potential. It makes current flow. When electricity flows through a coil of wire, it generates a magnetic field that fills the area around the coil in a certain way. Unlike some other high voltage experiments, the Tesla coil has withstood many tests and trials. The process was quite laborious and lengthy, but the result was successful, and therefore successfully patented by the scientist. You can create such a coil in the presence of certain components. The following materials are required for implementation:

1. length 30 cm PVC (the more the better);
2. copper enameled wire (secondary wire);
3. birch board for the base;
4. 2222A transistor;
5. connection (primary) wire;
6. resistor 22 kΩ;
7. switches and connecting wires;
8. 9 volt battery.

Tesla Device Implementation Stages

First you need to place a small slot in the top of the pipe to wrap one end of the wire around. Wind the coil slowly and carefully, being careful not to overlap the wires or create gaps. This step is the most difficult and tedious part, but the time spent will give a very high quality and good coil. Every 20 or so turns, rings of masking tape are placed around the winding. They act as a barrier. In case the coil starts to unravel. When finished, wrap a tight tape around the top and bottom of the winding and spray it with 2 or 3 coats of enamel.

Then you need to connect the primary and secondary battery to the battery. After - turn on the transistor and resistor. The smaller winding is the primary and the longer winding is the secondary. You can optionally install an aluminum sphere on top of the pipe. Also, connect the open end of the secondary to the added one, which will act as an antenna. You need to create everything with great care not to touch the secondary device when you turn on the power.

There is a risk of fire if sold by yourself. You need to flip the switch, install an incandescent lamp next to the wireless power transmission device and enjoy the light show.

Wireless transmission via solar power system

Traditional wired power distribution configurations typically require wires between distributed devices and consumer units. This creates a lot of restrictions as the cost of system cabling costs. Losses incurred in transmission. As well as waste in distribution. Transmission line resistance alone leads to a loss of about 20-30% of the generated energy.

One of the most modern wireless power transmission systems is based on the transmission of solar energy using a microwave oven or a laser beam. The satellite is placed in geostationary orbit and consists of photovoltaic cells. They convert sunlight into electrical current, which is used to power a microwave generator. And, accordingly, realizes the power of microwaves. This voltage is transmitted using radio communication and received at the base station. It is a combination of antenna and rectifier. And it is converted back into electricity. Requires AC or DC power. The satellite can transmit up to 10 MW of RF power.

If we talk about a DC distribution system, then even this is impossible. Since it requires a connector between the power supply and the device. There is such a picture: the system is completely devoid of wires, where you can get AC power in homes without any additional devices. Where it is possible to charge your mobile phone without having to physically connect to the socket. Of course, such a system is possible. And a lot of modern researchers are trying to create something modernized, while studying the role of developing new methods of wireless transmission of electricity at a distance. Although, from the point of view of the economic component, it will not be entirely beneficial for states if such devices are introduced everywhere and replace standard electricity with natural electricity.

Origins and examples of wireless systems

This concept is not really new. This whole idea was developed by Nicholas Tesla in 1893. When he developed a system of illuminating vacuum tubes using wireless transmission techniques. It is impossible to imagine that the world exists without various sources of charging, which are expressed in material form. To make it possible for mobile phones, home robots, MP3 players, computers, laptops and other transportable gadgets to be charged on their own, without any additional connections, freeing users from constant wires. Some of these devices may not even require a large number of elements. The history of wireless power transmission is quite rich, and, mainly, thanks to the developments of Tesla, Volta, and others. But, today it remains only data in physical science.

The basic principle is to convert AC power to DC voltage using rectifiers and filters. And then - in the return to the original value at high frequency using inverters. This low voltage, highly oscillating AC power is then transferred from the primary transformer to the secondary. Converted to DC voltage using a rectifier, filter and regulator. The AC signal becomes direct due to the sound of the current. As well as using the bridge rectifier section. The received DC signal is passed through a feedback winding which acts as an oscillator circuit. At the same time, it forces the transistor to conduct it into the primary converter in the direction from left to right. When current passes through the feedback winding, the corresponding current flows to the primary of the transformer in the direction from right to left.

This is how ultrasonic energy transfer works. The signal is generated through the sensor for both half cycles of the AC alert. The sound frequency depends on the quantitative indicators of the vibrations of the generator circuits. This AC signal appears on the secondary winding of the transformer. And when it is connected to the transducer of another object, the AC voltage is 25 kHz. A reading appears through it in a step-down transformer.

This AC voltage is equalized by a bridge rectifier. And then filtered and regulated to get a 5V output to drive the LED. The 12V output voltage from the capacitor is used to power the DC fan motor to run it. So, from the point of view of physics, the transmission of electricity is a fairly developed area. However, as practice shows, wireless systems are not fully developed and improved.

Do-it-yourself wireless transmission of electricity

I offer one of the ways to transfer energy without wires at a distance.

Several components are needed to conduct experiments on wireless energy:

• Fits almost any coil of wire
• fit many NPN transistors
• resistor 1 kΩ
• Power supply and LED.
• The device diagram is very simple.

To make the transmitter coil, first 15 turns are wound on the frame you like with the wire you have, then a tap is made and we continue winding in the same direction for another 15 turns. Thus, a branch is obtained from the middle of the winding. The coil is ready. As a frame, I used a frame of masking tape, and as a wire - a core from a UTP cable, but it is better to take the wire thinner and in varnish insulation, for example, from an old transformer.

Further, a resistance of 1 kOhm is soldered to any end of the transmitter coil, to which the base of the transistor is soldered. The transistor collector is soldered to the other end of the transmitter coil. The transmitter is ready!

Now we connect the power according to the diagram in the video, namely PLUS to the tap from the middle of the winding, and MINUS to the emitter of the transistor.
For experiments with different transistors, a power supply with smooth voltage regulation is used, therefore, using different transistors and smoothly increasing the voltage, you can observe different thresholds for different transistors.

For this video I used 2SC2625 transistor

And a 2N3053 transistor. The frequencies of the transmitter with different transistors are different.

For the manufacture of the receiver, 30 turns are wound with the same wire and preferably on the same frame. But you can use various existing coils.

In fact, in the 1970s, he technically realized the dreams of NATO and the United States of constant air patrols of Iraq (Libya, Syria, etc.) with drones with cameras, hunting (or fixing) "terrorists" on-line 24 hours.

In 1968, the American space research specialist Peter E. Glaser proposed placing large solar panels in geostationary orbit, and transmitting the energy they generate (5-10 GW level) to the Earth's surface with a well-focused beam of microwave radiation , then convert it into energy of direct or alternating current of technical frequency and distribute it to consumers.

Such a scheme made it possible to use the intense flux of solar radiation that exists in the geostationary orbit (~ 1.4 kW/sq.m.) and transmit the received energy to the Earth's surface continuously, regardless of the time of day and weather conditions. Due to the natural inclination of the equatorial plane to the ecliptic plane with an angle of 23.5 degrees, a satellite located in a geostationary orbit is illuminated by a flux of solar radiation almost continuously, except for short periods of time near the days of the spring and autumn equinoxes, when this satellite falls into the Earth's shadow. These periods of time can be accurately predicted, and in total they do not exceed 1% of the total length of the year.

The frequency of electromagnetic oscillations of the microwave beam must correspond to those ranges that are allocated for use in industry, scientific research and medicine. If this frequency is chosen to be 2.45 GHz, then meteorological conditions, including thick clouds and heavy precipitation, have little effect on the efficiency of power transmission. The 5.8 GHz band is tempting because it allows you to reduce the size of the transmitting and receiving antennas. However, the influence of meteorological conditions here already requires further study.

The current level of development of microwave electronics allows us to speak of a rather high efficiency of energy transfer by a microwave beam from a geostationary orbit to the Earth's surface - about 70% ÷ 75%. In this case, the diameter of the transmitting antenna is usually chosen to be 1 km, and the ground-based rectenna has dimensions of 10 km x 13 km for a latitude of 35 degrees. SCES with an output power level of 5 GW has a radiated power density in the center of the transmitting antenna of 23 kW/m², in the center of the receiving antenna - 230 W/m².

Various types of solid-state and vacuum microwave generators for the SCES transmitting antenna were investigated. William Brown showed, in particular, that magnetrons, which are well mastered by the industry, designed for microwave ovens, can also be used in transmitting antenna arrays of SCES, if each of them is provided with its own negative feedback circuit in phase with respect to an external synchronizing signal (so called Magnetron Directional Amplifier - MDA).

The most active and systematic research in the field of SCES was conducted by Japan. In 1981, under the guidance of professors M. Nagatomo (Makoto Nagatomo) and S. Sasaki (Susumu Sasaki), research was started at the Space Research Institute of Japan to develop a prototype SCES with a power level of 10 MW, which could be created using existing launch vehicles. The creation of such a prototype allows one to accumulate technological experience and prepare the basis for the formation of commercial systems.

The project was named SKES2000 (SPS2000) and received recognition in many countries of the world.

In 2008, Marin Soljačić, assistant professor of physics at the Massachusetts Institute of Technology (MIT), was awakened from a sweet sleep by the persistent beeping of a mobile phone. “The phone would not stop, demanding that I put it on charge,” Soljacic said. Tired and not going to get up, he began to dream that the phone, once at home, would start charging by itself.

In 2012-2015 University of Washington engineers have developed technology that allows Wi-Fi to be used as an energy source to power portable devices and charge gadgets. The technology has already been recognized by Popular Science magazine as one of the best innovations of 2015. The ubiquity of wireless data transmission technology itself has made a real revolution. And now it's the turn of wireless power transmission over the air, which the developers from the University of Washington called (from Power Over WiFi).

During the testing phase, the researchers were able to successfully charge low-capacity lithium-ion and nickel-metal hydride batteries. Using the Asus RT-AC68U router and several sensors located at a distance of 8.5 meters from it. These sensors just convert the energy of an electromagnetic wave into a direct current with a voltage of 1.8 to 2.4 volts, which is necessary to power microcontrollers and sensor systems. The peculiarity of the technology is that the quality of the working signal does not deteriorate. It is enough just to reflash the router, and you can use it as usual, plus supply power to low-power devices. One demonstration successfully powered a small, low-resolution covert surveillance camera located more than 5 meters away from a router. Then the Jawbone Up24 fitness tracker was charged to 41%, it took 2.5 hours.

To tricky questions about why these processes do not negatively affect the quality of the network communication channel, the developers replied that this becomes possible due to the fact that a flashed router sends out energy packets during its work on unoccupied information transfer channels. They came to this decision when they discovered that during periods of silence, energy simply flows out of the system, and in fact it can be directed to power low-power devices.

During the study, the PoWiFi system was placed in six houses, and the residents were invited to use the Internet as usual. Load web pages, watch streaming video, and then tell them what's changed. As a result, it turned out that network performance did not change in any way. That is, the Internet worked as usual, and the presence of the added option was not noticeable. And these were only the first tests, when a relatively small amount of energy was collected over Wi-Fi.

In the future, PoWiFi technology may well serve to power sensors built into household appliances and military equipment in order to control them wirelessly and carry out remote charging / recharging.

Relevant is the transfer of energy for UAVs (most likely, already by technology or from a carrier aircraft):

The idea looks quite tempting. Instead of today's 20-30 minutes of flight time:
→
→

Let me explain:
-exchange of m / y drones is still necessary (swarm algorithm);
- the exchange of m / y drones and aircraft (womb) is also necessary (control center, correction of knowledge base, retargeting, command to eliminate, preventing "friendly fire", transfer of intelligence information and commands to use).

Who's next in line?

Note: A typical WiMAX base station radiates at approximately +43 dBm (20 W), while a mobile station typically transmits at +23 dBm (200 mW).

Permissible levels of radiation from mobile base stations (900 and 1800 MHz, the total level from all sources) in the sanitary-residential zone in some countries differ markedly:
Ukraine: 2.5 µW/cm². (the most stringent sanitary standard in Europe)
Russia, Hungary: 10 µW/cm².
Moscow: 2.0 µW/cm². (the norm existed until the end of 2009)
USA, Scandinavian countries: 100 µW/cm².

The temporary allowable level (TDU) from mobile radiotelephones (MRT) for users of radiotelephones in the Russian Federation is defined as 10 μW / cm² (Section IV - Hygienic requirements for mobile land radio stations SanPiN 2.1.8 / 2.2.4.1190-03).

In the USA, the Certificate is issued by the Federal Communications Commission (FCC) for cellular devices whose maximum SAR level does not exceed 1.6 W/kg (moreover, the absorbed radiation power is reduced to 1 gram of human tissue).

In Europe, according to the international directive of the Commission on Non-Ionizing Radiation Protection (ICNIRP), the SAR value of a mobile phone should not exceed 2 W / kg (with the absorbed radiation power given to 10 grams of human tissue).

More recently, in the UK, a level of 10 W/kg was considered a safe SAR level. A similar pattern was observed in other countries as well. The maximum SAR value accepted in the standard (1.6 W/kg) cannot even be safely attributed to “hard” or “soft” standards. The standards for determining the SAR value adopted both in the USA and in Europe (all the regulation of microwave radiation from cell phones in question is based only on the thermal effect, that is, associated with the heating of human tissues).

COMPLETE CHAOS.

Medicine has not yet given a clear answer to the question: is mobile / WiFi harmful and how much? And what about the wireless transmission of electricity by microwave technology?

Here the power is not watts and miles of watts, but already kW ...

Links, used documents, photos and videos:
"(JOURNAL OF RADIOELECTRONICS!" N 12, 2007 (ELECTRIC POWER FROM SPACE - SOLAR SPACE POWER PLANTS, V. A. Banke)
"Microwave electronics - prospects in space energy" V. Banke, Ph.D.
www.nasa.gov
www. whdi.org
www.defense.gov
www.witricity.com
www.ru.pinterest.com
www. raytheon.com
www. ausairpower.net
www. wikipedia.org
www.slideshare.net
www.homes.cs.washington.edu
www.dailywireless.org
www.digimedia.ru
www. powercoup.by
www.researchgate.net
www. proelectro.info
www.youtube.com

Wireless electricity has been known since 1831, when Michael Faraday discovered the phenomenon of electromagnetic induction. He experimentally established that a changing magnetic field generated by an electric current can induce an electric current in another conductor. Numerous experiments were carried out, thanks to which the first electrical transformer appeared. However, only Nikola Tesla managed to fully realize the idea of ​​transmitting electricity at a distance in practical application.

At the World's Fair in Chicago in 1893, he showed the wireless transmission of electricity by lighting phosphor bulbs that were spaced apart. Tesla has demonstrated many variations on the transmission of electricity without wires, dreaming that in the future this technology will allow people to transmit energy in the atmosphere over long distances. But at this time, this invention of the scientist turned out to be unclaimed. Only a century later, Intel and Sony became interested in Nikola Tesla's technologies, and then other companies.

How it works

Wireless electricity is literally the transmission of electrical energy without wires. Often this technology is compared with the transmission of information, for example, with Wi-Fi, cell phones and radio. Wireless power is a relatively new and dynamically developing technology. Today, methods are being developed to safely and efficiently transmit energy over a distance without interruption.

The technology is based on magnetism and electromagnetism and is based on a number of simple operating principles. First of all, this concerns the presence of two coils in the system.

• The system consists of a transmitter and receiver that together generate an alternating, non-constant current magnetic field.
• This field creates voltage in the receiver coil, for example, to charge a battery or power a mobile device.
• When an electric current is directed through a wire, a circular magnetic field appears around the cable.
• On a coil of wire that is not directly supplied with electric current, electric current will begin to flow from the first coil through the magnetic field, including the second coil, providing inductive coupling.

Transmission principles

Until recently, the magnetic resonance system CMRS, created in 2007 at the Massachusetts Institute of Technology, was considered the most advanced technology for transmitting electricity. This technology provided the transmission of current over a distance of up to 2.1 meters. However, some limitations prevented it from being launched into mass production, for example, a high transmission frequency, large dimensions, a complex coil configuration, and high sensitivity to external interference, including the presence of a person.

However, scientists from South Korea have created a new electricity transmitter that will allow energy to be transmitted up to 5 meters. And all appliances in the room will be powered by a single hub. The resonant system of DCRS dipole coils is capable of operating up to 5 meters. The system is devoid of a number of disadvantages of CMRS, including the use of rather compact coils with dimensions of 10x20x300 cm, they can be discreetly installed in the walls of the apartment.

The experiment made it possible to transmit at a frequency of 20 kHz:

1. 209 W at 5 m;
2. 471 W at 4 m;
3. 1403 W at 3 m.

Wireless electricity allows you to power modern large LCD TVs that require 40 watts from a distance of 5 meters. The only thing from the mains will be "pumped out" 400 watts, but there will be no wires. Electromagnetic induction provides high efficiency, but at a short distance.

There are other technologies that allow you to transmit electricity without wires. The most promising of them are:

• laser radiation . Provides network security, as well as a long range. However, line of sight between receiver and transmitter is required. Working installations powered by a laser beam have already been created. Lockheed Martin, an American manufacturer of military equipment and aircraft, has tested the Stalker unmanned aerial vehicle, which is powered by a laser beam and stays in the air for 48 hours.
• microwave radiation . Provides a long range, but has a high equipment cost. A radio antenna is used as a transmitter of electricity, which creates microwave radiation. On the receiver device is a rectenna, which converts the received microwave radiation into electric current.

This technology makes it possible to significantly remove the receiver from the transmitter, including the absence of a direct need for line-of-sight. But with an increase in the range, the cost and size of the equipment increase proportionally. At the same time, high-power microwave radiation generated by the installation can be harmful to the environment.

Peculiarities

• The most realistic of the technologies is wireless electricity based on electromagnetic induction. But there are limitations. Work is underway to scale up the technology, but there are health concerns.
• Technologies for transmitting electricity using ultrasound, laser and microwave radiation will also develop and will also find their niches.
• Orbiting satellites with huge solar arrays need a different approach, it will require targeted transmission of electricity. Laser and microwave are appropriate here. At the moment there is no ideal solution, but there are many options with their pros and cons.
• Currently, the largest manufacturers of telecommunications equipment have joined together in a consortium of wireless electromagnetic energy with the aim of creating a worldwide standard for wireless chargers that operate on the principle of electromagnetic induction. Of the major manufacturers, Sony, Samsung, Nokia, Motorola Mobility, LG Electronics, Huawei, HTC provide support for the QI standard on a number of their models. QI will soon become the unified standard for any such devices. Thanks to this, it will be possible to create wireless charging zones for gadgets in cafes, transport hubs and other public places.

Application

• Microwave helicopter. The helicopter model had a rectenna and rose to a height of 15 m.
• Wireless electricity is used to power electric toothbrushes. The toothbrush has a completely sealed body and has no connectors, which avoids electric shock.
• Powering aircraft with a laser.
• Wireless charging systems for mobile devices have appeared on sale, which can be used everyday. They work on the basis of electromagnetic induction.
• Universal charging pad. They allow you to power most popular smartphone models that are not equipped with a wireless charging module, including conventional phones. In addition to the charging pad itself, you will need to buy a receiver case for the gadget. It connects to a smartphone via a USB port and charges through it.
• Currently, over 150 devices up to 5 watts are sold on the world market that support the QI standard. In the future, medium power equipment up to 120 watts will appear.

prospects

Today, work is underway on large projects that will use wireless electricity. This is the power supply of electric vehicles "over the air" and household electrical networks:

• A dense network of autocharging points will make it possible to reduce batteries and significantly reduce the cost of electric vehicles.
• Power supplies will be installed in each room, which will transmit electricity to audio and video equipment, gadgets and household appliances equipped with appropriate adapters.

Advantages and disadvantages

Wireless electricity has the following advantages:

• No power supplies required.
• Complete lack of wires.
• Eliminate the need for batteries.
• Less maintenance required.
• Huge prospects.

The disadvantages also include:

• Insufficient development of technologies.
• Distance limited.
• Magnetic fields are not completely safe for humans.
• High cost of equipment.

The principle of operation is clearly shown in a simple handicraft, in which the LED can light up wirelessly at a distance of 2 cm from the energy source. A circuit that acts as a boost converter as well as a wireless power transmitter and receiver can be improved and implemented in many brain projects.

Step 1: We need

NPN Transistor - I used a 2N3904, but you can use any NPN transistor (337, BC547, etc.), a PNP transistor will work too, just be careful about the polarity of the connections.
winding or insulated wire - about 3-4 meters (wires can be "obtained" from many devices, transformers, speakers, motors, relays, etc.)
1 kΩ resistor - will be used to protect the transistor from burning in case of overload, you can also use resistors up to 5 kΩ, you can even without a resistor, but then the battery will discharge faster.
LED - anyone will do, the main thing is to follow the scheme.
1.5V battery - do not use batteries with a higher voltage so as not to damage the transistor.
scissors or knife.
soldering iron (optional).
lighter (optional) for removing insulation from wires.

Step 2: Watch the process video

Step 3: Summarizing the video

So, we wind a coil of 30 turns on a cylindrical object, this will be coil A. Next, we wind a second coil of the same diameter, but at the same time we wind 15 turns and make a tap, and then another 15 turns, this is coil B. We fix the coils from unwinding with any in a suitable way, for example, simply making knots from the coil leads. An important point: for the correct functioning of this crafts the diameters of both coils and the number of turns must be the same.

We clean the conclusions of both coils and proceed to soldering the circuit. We decide on the emitter, base and collector of our transistor and solder the resistor to the base. We solder the other output of the resistor to the free output of coil B, not to the output-outlet. The second free output of coil B, again not a tap, is soldered to the collector.

For convenience, you can solder a small piece of wire to the emitter, so it will be easier to connect the battery.

The receiver circuit is easy to assemble: solder the LED to the terminals of coil A. And brain trick ready!

Step 4: Schematic Diagram

Step 5: Visual Drawing

Step 6: Testing

For a cast homemade in a working state, we connect the tap of coil B to the “plus” of the battery, and the “minus” to the emitter of the transistor. Then we bring the coils parallel to each other and the diode glows!

Step 7: Explanation

Let me explain a bit how it all works.

transmitter in our handicraft this is the oscillator circuit. You may have heard of the "stealing Joule circuit" which is strikingly similar to our transmitter circuit. In the “stealing Joule circuit”, the electricity from the 1.5V battery is converted into a higher voltage, but pulsed. The LED requires 3V, but thanks to the “stealing Joule circuit”, it glows perfectly from 1.5V.

"The chain that steals Joules" is known as a converter and generator, the circuit we created is also a generator and converter. And the energy is supplied to the LED through the induction that occurs in the coils, which can be explained in brain example conventional transformer.

Suppose the transformer has two identical coils. Then, during the passage of electricity through one coil, it becomes a magnet, the second coil enters the magnetic field of the first and, as a result, current begins to flow through it too. If the voltage in the first coil is variable, therefore, it impulsively loses its magnetic properties, which means that the second coil impulsively enters the magnetic field of the first one, that is, an alternating voltage is formed in the second coil.

In our homemade the transmitter coil creates a magnetic field into which the receiver coil is connected to the LED, which converts the received energy into light!

Presented brain trick converts the received energy into light, but it can be used in more diverse ways. You can also apply the principles of this homemade to create magic tricks, fun gifts or science projects. If you vary the diameters and the number of turns on the coils, then you can achieve maximum values, or you can change the shape of the coils, etc., the possibilities are not limited!

Step 9: Troubleshooting

When creating this homemade the following problems are possible:
The transistor is too hot - check the value of the resistor, it may need to be increased. At first I did not use a resistor, and the transistor burned out in the process. Or alternatively use a heatsink for the transistor, or maybe another transistor with a higher gain value.
The LED does not light up - there can be many reasons. Check the quality of the connection, whether the base and the collector are soldered correctly, make sure that the coils are of equal diameter, if there is a short circuit in the circuit.

Today's experiment with induction is over, thank you for your attention and success in your work!