Operating frequency - 100 kHz. I tried 200 kHz - it didn’t get better, but key field workers (and IR2153) find it easier to work at 100 kHz. An important element of the circuit is capacitor C4, with which coil L3 forms a parallel oscillatory circuit. The coil contains only 7 turns of 1 mm wire, and without this capacitor we would have to wind significantly more turns, reducing the diameter of the wire to fit into our dimensions, as a result of which there are more losses for heating the wire, since even with a 1 mm wire the coil heats up quite strongly . And the required current cannot be obtained without this capacitor.
Resistor R2 is needed to adjust the frequency, so as not to select capacitor C4. As a result, by changing the frequency, we change the output current of the circuit. This is necessary to set the required current. Through 3 mm plastic, the memory is capable transmit current 1A, but at the same time the coils get very hot (much more than the transistors). It's better to exhibit about 0.5 A.
Charger transmitter:
The coils were wound on a collapsible plastic reel 2 mm thick:
I rolled up the receiving area without one side cover, placing a piece of paper under it and soaking it with superglue in the process. The transmitter was impregnated with zapon varnish or rubber glue - whatever was at hand. But since it will get very hot during operation, it is better to fill it with epoxy.
Charge controller I use from Eddy71, but you can also install TL431 + LM317 or, in general, a protection board against a dead battery. Or take a battery with a built-in charge controller. It’s just that the controller that I use not only charges, but also does not allow the battery to discharge below 3.1 Volts, and a tact button is connected to it, allowing you to turn the load on/off.
Power supply for wireless charging I used 12 Volt 2 Ampere, it costs 5 bucks, but inside there is a PWM controller and a field switch on the radiator. There is even a power filter, which made me happy. This is not a cheap simple electronic transformer.
Hi all. I purchased a kit on a Chinese website for wireless transmission energy, also called wireless charging. Of course, you can assemble this device yourself; there are plenty of wireless charger diagrams on the Internet. But I wanted to purchase a complete device, offered to us as a DIY device. Use as a wireless charger for mobile phone, I didn't mean to. But in robotics, I saw clear advantages over wired chargers.
The device you created in robotics can independently assess the battery charge and, if necessary, independently recharge. For example, a robot only needs to approach the charger at an appropriate distance and the charging process will begin. Very convenient, the robot wants to stay in working order and let it take care of itself.
Wireless charging consists of two parts, a receiver and an energy transmitter.
The transmitter supply voltage is twelve volts, while the receiver output is five volts. The stated maximum charging current is six hundred milliamps. There was no additional documentation on the site. After scouring the Internet, I found the following information. The receiver uses a T3168 chip
Unlike the receiver, the energy transmitter is, so to speak, filled with a compound. Accordingly, it was not possible to get to the board. The documentation for the receiver included a response circuit for the transmitter.
But I still got to the board (using a hammer), as it turned out, the circuit is different. There were two microcircuits installed on the board, without any markings. We were able to obtain scant information about the mysterious micro-assemblies on the forums. I found out it's two powerful transistor turned on in high-frequency generator mode. Subsequently, I found out that you can also buy an open board without filling.
As for the charging current. The wireless charger, as I already said, allows you to charge the battery with a current of up to 600 milliamps. But we will receive this current only in the immediate vicinity between the circuits. The table shows the relationship between distance and current.
Wireless demonstration charger and a number of others I filmed. In general, I liked the module. In the future I am going to use a wireless charger in my project.
The phenomenon of electromagnetic induction was observed even before Faraday, but the great Michael was the first to find an explanation for it and tried to transmit electric force over a distance by induction. Currently, the transmission of electricity over short distances at higher frequencies without wires is increasingly widespread; In this way, car batteries of ordinary cars and even traction batteries of electric vehicles are charged. As a result, do-it-yourself wireless charging is a request that is very popular among tinkerers. What fuels interest in the topic is that manufacturers of wireless chargers set their prices from the heart, and power receivers with wireless power supply are disproportionately expensive compared to their wired counterparts of the same type.
Wireless phone charging is very convenient: no need to fuss with wires and plugs, especially at night when your eyes are already sticking together. In addition, phones, smartphones and tablets are becoming thinner. In general, this is not bad, but the charge connector, which should pass a current of up to 2A, has become so flimsy that it can break due to awkward movement or fail, the contacts will slightly oxidize. And without wires - just put the device (gadget) on charge, and it charges.
In the induction boom, chargers for gadgets stand apart; the controversy surrounding them is extremely hot. Some consider wireless charging almost a product of hellish forces: they say, there is something built into it that zombifies the user into actively accepting certain religious, commercial or political trends, and at the same time ruins his health. Others, on the contrary, identify the electromagnetic field (EMF) of charging with the almost mystical power of Qi, which guarantees ascending reincarnation to the owner. The truth in this case lies not in the middle, but completely to the side, so the purpose of this article is to provide information about the following:
- How, being, as they say, not in the know and not wanting to bother with all sorts of intricacies, when buying exactly choose wireless charging harmless and safe. The power of Qi is already a matter of pure faith. Its existence, like any other something else omnipresent, omniscient and omnipotent, cannot be proven or refuted by the arguments of reason.
- The principle of operation and design of WPC standard chargers for gadgets.
- How to properly charge the battery of a phone, smartphone, tablet.
- Methods of transmitting electricity over a distance without wires.
- Harmful factors and dangers associated with the use of wireless chargers.
- Is it possible and how to convert an old mobile phone to the WPC standard?
- How to assemble a wireless charger at home, suitable for any WPC standard gadgets and completely safe, costing no more than $10 for components.
How to choose harmless charging
Einstein once said: “If a scientist cannot explain to a five-year-old child what he does, then he is either mad or a charlatan.” The power of Qi is the power of Qi, but all our actual achievements are based on objective knowledge that does not depend on the subject. Let's say we brought an Amazonian savage to our home, there are others like that there. They took him to the TV and said: “If you plug this thing, a plug, here into the socket, and press here, then a picture will appear here, and sound will come from here.” If the savage does everything as told, the TV will turn on, the picture will appear, the sound will play, although the savage has no idea about electricity and electronics, and considers a thunderstorm to be an indigestion for his gods. So the kettle is full, as they say, maybe choose wireless charging for your gadget, which you can use without fear:
- Make sure that the device has a WPC standard compliance icon (see below);
- Please show the charging: there, except for the indicator turning on Power or I/O, there must be a Charge indicator or indicated by the same icon as on the gadget;
- please turn it on. Power should light up, but Charge should not;
- We put the gadget on charge – Charge should light up, and the gadget’s display should show the charge;
- We lift the gadget no more than 3 cm above the charging platform - Charge should go out and the display should show that charging has stopped.
This type of wireless charging can be safely used at home if it is located no closer than 1.5-2 m from places of long-term stay of people(bed, desk, favorite sofa in front of the TV). Keep the wireless switched on in the nursery charging is not allowed, incl. and described below, which can be constantly turned on on the nightstand by an adult’s bed.
What is WPC
WPC is an abbreviation for Wireless Power Consortium, the name of the company that first brought wireless charging to the market. WPC technology is nothing new, much less supernatural; The components of WPC charging and its operating principle are shown in Fig. The familiar iron transformer also operates on the transmission of electricity by induction. The peculiarity of WPC is that the operating frequency is increased to tens of kHz or even MHz; this allows you to separate the primary and secondary windings at some distance and do without a ferromagnetic core, because The energy flux density (PED) of EMF increases with frequency; also increases with frequency technical capabilities concentrate EMF in a limited area. But at the same time, the biological effect of EMF increases with frequency, which is why small and weak wireless charging can be more dangerous than an industrial induction heating installation.
Note: WPC is still an industry standard, in our opinion; it has not yet been formalized by international agreements. Therefore, the technical data of gadgets with WPC, especially from alternative manufacturers, may differ so that they are charged only from “their” charger. If you do wireless charging with your own hands, you need to give a design margin and technological possibility modify the transmitter for a specific device, see below.
Devices designed for recharging using the WPC system are indicated by a special icon (item 1 in the figure). It means that the device has a receiving coil of 25 turns and an RF converter alternating current to permanent. A number of gadgets are available with or without WPC. Then the induction receiver is either “thrown” and located under the battery cover (pos. 2), or modular, pos. 3. In any case, a connector (item 4) or clamping contacts are provided for the WPC receiver, where you should connect the homemade receiver when modifying the gadget for WPC. The polarity is determined by the multitester when wired charging is connected, because... Wireless charging contacts are paralleled with those of conventional charging.
Note: Under no circumstances should the WPC receiver be connected directly to the battery! In the best case, an expensive battery will soon fail, because... In the device it is charged in a special way, see below. And modern lithium batteries A large capacity charge directly to the terminals can simply explode!
In some gadgets, the WPC receiver is hidden under a cover, the removal of which requires partial disassembly of the device, pos. 5. One way or another, if your model without WPC has a “twin” with wireless charging discovered by searching on the Internet, then yours will also have a cavity for the receiver: it would be too expensive to produce various parts of the case. This greatly simplifies the development of the gadget for WPC, but you need to make sure that this model Available in both versions.
About the charging mode
The battery in any gadget is charged under the control of a special controller, which first determines how discharged the battery is. If it is more than 75%, then an increased fast (boosted) charge current is immediately supplied, equal to approximately the 3-hour discharge current, if the charger provides it. No - the charging takes the current that it can provide when the output voltage drops to 5 V. Therefore, many devices from USB ports take a long time to charge, because standard output USB power supply 5V 350mA.
The forced charge is designed to eliminate the polarization of the battery electrodes, which causes the so-called. hysteresis. The capacity of the “hysteresis” battery continuously decreases, and its resource turns out to be much less than declared. A fast charge with a current of less than 3 hours does not completely eliminate the hysteresis, and the battery soon runs out. As a result, charging for a smartphone or tablet must provide a charge current of more than 1.5 A, because in “smart” gadgets, batteries are 1800-4500 mAh, i.e. their 3-hour discharge current will be 0.9-1.5 A.
After the battery has been charged for approx. up to 25% capacity, the charging current gradually decreases to the value of a small forming (recharging) current until the battery is “pumped” for approx. by 75%. Forming the battery with a small current avoids electrodegradation of the electrolyte, which also reduces the battery life. The forming current is approx. current of 12-hour battery discharge.
Finally, when the battery is fully charged, the controller passes a very tiny current through it for the minimum required time to prevent chemical degradation of the electrolyte, and only then gives a signal about the end of the charge. Therefore, keeping a gadget with a working and properly designed controller on charge for more time is not at all harmful, on the contrary. The author has an old one Motorola phone W220. For the sake of experience, it is charged all the time, except when you need to leave the house with it. Over more than 10 years of use, the battery has not noticeably lost its capacity: the 4 days of “hibernation” and 4 hours of continuous conversation specified in the phone’s passport have not decreased. And other users of the same model had to change the completely depleted battery.
Induction or radiation?
Induction
The transfer of electrical power over a distance occurs through an electromagnetic field (EMF), in which a certain energy is stored. For inductive energy transfer, in addition to the transmitter, you also need a receiver, not necessarily electronic. It could be, for example, an aluminum pan, in the metal of which the EMF transmitter induces Foucault eddy currents that heat the dishes. The currents induced in the receiver create their own EMF, which interacts with the EMF of the transmitter. As a result, a common EMF is formed between the transmitter and the receiver, which transfers power from the first to the latter. Hence the first characteristic feature inductive energy transfer - the influence of the receiver on the operating mode of the transmitter, the so-called. source response to load.
Note: EMF with the induction method of energy transfer is especially highly concentrated near the source-receiver system in the presence of ferromagnetic materials there. An example is an electrical transformer based on iron or, at higher frequencies, on a ferrite core.
It is advisable to transmit power by induction at lower frequencies, because EMF high frequency(HF) does not penetrate deep into the conductors, this is the so-called. surface effect or skin effect, and with increasing frequency, energy losses due to radiation increase. EMF energy flux density (EMF PPE) per low frequencies is small, because EMF energy in a given volume from a source of a certain intensity depends on frequency.
The first difference between power transmission by radiation and induction is that the EMF “breaks away”, “leaves” from the source, losing contact with it, i.e. is emitted. If, for example, you give an impulse with a combat laser into space, and then turn off or destroy the source, then the packet of EMF oscillations will rush and rush in world space until it hits an obstacle and is absorbed by it or dissipates in the propagation medium. The consequence is that when power is transmitted by radiation, there is no reaction from the source to the receiver. A second-order consequence is that the ability of EMF to spontaneously concentrate is also absent, because the radiation itself tends to “spread” to the sides; to assemble it in a given area, special design and technical measures are needed. Unlike the induction method, the presence of ferromagnets in the transmitter coverage area reduces the power transfer coefficient, because ferromagnets “pull” EMF towards themselves, which should get into the receiver.
The efficiency of energy transfer by EMF radiation depends on the frequency of its oscillations, because There is no on-demand field pumping by the transmitter. What is “downloaded” into the emitted packet will be there. It is possible to add energy to the consumer only by continuing the radiation. Another feature is that the material that most effectively absorbs the flow of EMF power is not a conductive material, but, on the contrary, absorbs EMF energy; these properties are used in microwave ovens. A long insulated conductor of a certain configuration (for example, twisted into a spiral), which in this case represents a receiving antenna, can also be an absorber of EMF energy.
Both
In order to meet the requirements of minimum weight and dimensions and the absence of foreign ferromagnets near the radio path of the gadget, WPC developers had to increase the operating frequency of the system; After all, tablets also have transceivers for working in a Wi-Fi environment. As a result, WPC gained the ability to work with both induction and radiation. This feature allows, in principle, to increase the range of WPC to several meters, which is what some amateurs use. Such enthusiasts, apparently, either do not know at all about the biological effects of EMFs, or deliberately ignore such information.
In this case, it is impossible to say “the problems of the Indians are the problems of the Indians”, because “Indians” may turn out to be strangers, ignorant and uninvolved people, for example, neighbors behind the wall or their own children. Before you start making wireless charging, you need to figure out under what circumstances it will be harmful or dangerous and how to avoid it.
However, a very definite intermediate conclusion can already be drawn - wireless charging must be selected upon purchase (see above) or done only inductively and spontaneously, without additional automation, switching without a receiver at the charging site to standby mode with the generator power reduced to a safe level. Of course, it’s completely convenient when the phone is lying around anywhere in the room and is still charging, but it’s healthy - you understand.
Note: There is no point in charging with a generator that turns off without a phone on charge. After all, then to charge the gadget you will have to turn it on, which reduces the convenience of wireless charging to almost nothing. Wireless charging must be done with a very sharp, as they say, acute, reaction of the generator to the receiver. There is also no point in integrating a mechanical or opto-sensor for the presence of a gadget into the charging; it can be triggered by something similar to it, but does not force the generator to reduce power.
Factors of harm and danger
The effect of EMF on living organisms also depends on the frequency of its oscillations. In general, it monotonically increases with frequency approx. up to 120-150 MHz, and then bursts and dips are observed. In one of them, visible light, we have adapted to live in the course of evolution; One of the others operates microwaves around 2900 MHz. But the microwave dip in EMF bioactivity is shallow, otherwise it will not be absorbed by the products, as long as it is technically possible and not very difficult to shield the oven from EMF radiation to the outside. Therefore, if you are planning to repair a microwave oven yourself, you need to know exactly how it works, how it works, what is possible, what is permissible to do and what is not allowed to prevent the microwave from siphoning out, and know how to determine at home whether the microwave is siphoning bake. But let's get back to the topic.
The EMF PPE also increases with frequency, so the norms for its level are tied to the PPE. In addition, individual sensitivity to PPE EMF varies within a very wide range, approx. 1000 times. In countries with frankly redneck labor and social legislation, permissible levels PES to monstrous values up to 1 (W*s)/sq. m. Approach in this case: were you warned when hiring? Do they pay for your additional medical insurance? Will they guarantee an increased pension for harmful activities after 10 (15, 20) years? The rest is Indian problems.
In PPE of this level, a person directly feels the effect of EMF: heaviness in the head, gentle warmth coming from the depths of the body. Gentle, but extremely dangerous: this is evidence of the beginning of plasmolysis of cells, which is why they can undergo malignant degeneration. “The device at half past six” is still the most terrible consequence of “picking up the bunny” PPE EMF.
In the USSR, the other extreme was in effect - 1 (μW*s)/sq. m, i.e. a million times less. The impact of such a PPE on the most sensitive subject will not affect either immediately or in the long term. Each citizen, or rather subject, of the “Council of Deputies” was actually the property of the state, but it also guaranteed his life, health and safety. At least formally.
For a market economy, such reinsurance will be unbearable, and in the current clogged airwaves, it is hardly technically feasible. Therefore, the generally accepted standard for the EMF PES level today is intermediate – 1 (mW*s)/sq. m. Such a PPE, which affects constantly and for a long time, will certainly give long-term consequences, but regular exposure to it for no more than a certain time per day is harmless and safe for the average person. Those who are overly sensitive are screened out by a medical examination during hiring, and the consequences of random deviations can already be compensated for without overtaxing social funds. Also, of course, a redneck approach, treating cancer in retirement instead of rest is not great pleasure, but at least within reason. Therefore, we will consider wireless charging potentially dangerous if it creates a PPE EMF of 1 (mW*s)/sq.m within a touch radius (approx. 0.5 m). m or more.
Safety calculation
Let's believe the advertising and buy a “super-duper” USB-powered charger (power consumption - 1.75 W), operating within a radius of 20 cm (0.2 m). The efficiency of a blogging generator (see below) of this power using a field-effect transistor is approx. 0.8; 1.4 W will go on air without a gadget lying on the site. The area of a sphere with a radius of 0.2 m is 0.0335 sq. m. PES on it will be 2.8/0.0335 = 41.8 (W*s)/sq. m(!). The PES value is inversely proportional to the square of the distance from the source. At what point in this case will it drop to the permissible 1 (mW*s)/sq. m? The calculation is simple: we take the square root of the ratio of the actual PES to the permissible one, and multiply the result by the initial radius of 0.2 m, i.e. divide by 5; we get... 20.4 m! This is what manufacturers' assurances of product safety are worth. Along with the power of Qi.
The above statement about the gadget on the site is not accidental. In this case, the charge at frequencies whose wavelengths are much greater than the gap between the emitter and the device will be inductive, if the receiver is suitable for it. The receiving coil of the gadget is uniquely suitable as an induction receiver. A gap of 3 cm (see above) will give a frequency of 10 GHz, which the generator is definitely not capable of producing; In reality the gap is even smaller. So the preliminary conclusion is confirmed: our charging should be only and only inductive. The EMF PES in the gap between the inductor and the device will then be many times greater, but this is no longer dangerous, because The EMF will naturally be drawn to the receiving coil, the diameter of which is approx. 5 cm. At a distance from it three times greater (more precisely, e times, e = 2.718281828...) the presence of EMF can only be detected by a sensitive detector, but calculations “on your fingers” cannot be done here; for the conclusion you need to use the means of mathematical physics .
Note: The fact that the WPC standard is not international makes it possible for manufacturers of wireless chargers to “go to extremes” based on safety assurances. You can refer to the safety standards of the country where production is taking place. Or the one where the company is registered, and there may be no regulation of PPE at all; there are still such state entities left in some places.
About car chargers
From the calculation above it follows that wireless car charging is definitely dangerous: their range of action reaches 1 m. These marketers would be in such PPE for life... or at least until they feel the “device at half past six”... The justification given is the relative short duration of the impact and the need to protect an expensive gadget from damage due to the fact that it is dangling on a cord under the cigarette lighter. But wouldn’t it be smarter to simply extend the cord so that the gadget could be stored in the glove compartment or other convenient location? Driving a car with a phone in your hand is still risky, and in some places you can be fined for it.
If the gadget is without WPC
There are only 2 mandatory requirements for the WPC receiving coil: the number of turns is 25 and the wire diameter is designed for a current of 0.35 A, taking into account the skin effect at frequencies up to 30 MHz. Practically - from 0.35 mm for copper (without insulation). Thicker, when there is enough free space in the case, will only be better. Configuration – any according to location. Special care in manufacturing is not required (item 1 in the figure), but it is necessary that the ratio of the largest transverse dimension to the smallest does not exceed 1.5, otherwise the efficiency of the receiver will drop and the charge will be delayed.
If charging is done for an old plump phone or for a tablet without WPC, the coil is placed in the body of the gadget. A slight bend in place (item 2) will not affect the properties of the receiver. Suddenly there is not enough space inside (you still need to tuck the electronic components of the receiver somewhere), you will have to make a flat coil “like a branded one”, pos. 4. It is convenient to lay the wire in a flat spiral using tape placed on the substrate with the adhesive side up. To ensure that the Velcro does not wrap up and does not creep, it is fixed at the edges with strips of the same tape, applied with glue down. A round boss with a diameter of approx. is placed on the tape. 1 cm and lay turns around it, pressing the wire against the Velcro. When as many turns as necessary are laid, the boss is peeled off, the finished coil is dug to fix the turns with superglue or nitro varnish, pos. 3, and remove together with tape; its excess is trimmed off.
Doing exercises
Generators of homemade wireless charging and some of the factory ones are assembled according to the blocking generator circuit, or simply blocking, see figure:
We will do charging with a self-generator of harmonic oscillations according to an antediluvian circuit with weak inductive coupling. It fell out of use in industrial equipment back in the 20s of the last century, as soon as three-point generators, inductive and capacitive, were invented, precisely because of the very acute reaction to the load, but that’s what we need! And other shortcomings of a generator with a weak coupling are either eliminated by modern element base and circuitry, or are not fatal. So, at the beginning of a forced charge, the power consumption reaches 25 W, so a separate power source is needed. But the average long-term charge of a tablet with a 3500 mAh battery constantly turned on every night does not exceed 8 W, and in a month such charging will “wind up” as much as 5.75 kW/h.
But first of all, let's deal with the transmitting coil, because... this circuit is also sensitive to the parameters and quality of the frequency-setting nodes. To set up the generator (safety is worth something, nothing can be done) you will also have to hastily make a receiving coil, see above. You can use charging for its intended purpose only when the generator is set up, but then it works more stable and safer for the gadget than charging when blocked. Therefore, you can use any gadget with this charger: it is designed for 2 amperes of charging current or more. But old phone with a 450 mAh battery, it will take no more from it than the controller “prescribes” due to the same acute reaction to the load.
Transfer coil
Drawings of generator coils with weak inductive coupling are shown in Fig. below.:
On the left – contour L2 (see below); on the right - coil feedback L3 (in the middle) and charge indicating circuit coil L1. They are etched on a plate made of 2-sided foil fiberglass laminate 100x100 mm, 1.5 mm thick, so-called. laser-iron technology LUT. There is nothing complicated about it, the idea and name are amateurish. LUT allows you to make printed circuit boards at home no worse than branded ones, signs with inscriptions, contour drawings, patterned panels, etc., see the video below:
Video: laser ironing technology
In addition to this, we can say that it is best to clean the blank for LUT with a regular school eraser. Then the scraps of copper are washed off with a cotton swab or a white, clean cotton rag, generously moistened with 96% alcohol or nitro solvent, and then, while the surface is wet, wiped dry with a microfiber cloth for cleaning glasses. The toner of any type is firmly placed on the surface prepared in this way. laser printer and even inkjet from a template on a suitable (holding, but not absorbing ink) base.
Note: do not be confused by the width of the tracks in the drawing (0.75 mm for the contour coil). The permissible current density in a film conductor on a substrate is several times greater than in a round wire, and the skin effect is weaker. Yes, the path is on printed circuit board 10 mm wide and 0.05 mm thick can easily hold a current of 20 A, and this is far from the limit. Double-width feedback coil tracks are needed because... During the setup process, you will need to resolder the tap on it. In general, LUT allows you to obtain tracks up to 0.15-0.2 mm wide.
Circuit design
The diagram of a wireless charger on a generator with inductive coupling is shown in Fig. on the left is the transmitter; receiver on the right. Its features, firstly, are the powerful active element VT3. They can only be intensifying field-effect transistor. At the generator bipolar transistor there will be low efficiency, and powerful field keys of the IRF, IRFZ, IRL series from computer power supplies or electronic ignition systems do not work in active mode.
The second is the auto bias circuit VD3 C3. For powerful amplifier field workers, the initial drain current can reach 100-200 mA or more. Without a blocking potential on the gate, it will be possible to configure the generator only for power or standby mode, but not for both, and the PES from the inductor within the contact radius will certainly exceed the permissible value. But it is also impossible to form an auto-bias by connecting a resistor to the source circuit, as in the cathode circuit in tube amplifiers: the generator will not reach full power, because As the source current increases, the displacement will also increase in absolute value. Therefore, the bias circuit is made nonlinear on the diodes: at low powers it increases in accordance with the source current, which ensures a soft start of the generator and its safety for any gadgets, and when the diodes enter saturation, the bias becomes close to fixed and allows the generator to “swing to its fullest.” The bias circuit is selected during the setup process from powerful rectifier diffusion RF diodes (PiN, KD213, KD2997 structure) and Schottky diodes (SMD structure) for a current of 6 A. The saturation voltage of the former in the current range of 0.7-5 A varies within 1- 1.4 V; second - 0.4-0.6 V.
Elements R1, VD1, VT1, VT2, C1, R2, VD2 and L1 make up the charge indication circuit. If the current transfer coefficient β VT1 is more than 80, then VT2 is excluded, and the R2 engine is connected to the VT1 base. Capacitor C3 must be film; Even better is the old paper one, because... It dissipates significant reactive power.
The receiver of this charger also has special features. The first is full-wave rectification of the received current, because harmonic vibrations. Application of this device This does not interfere with charging gadgets with built-in WPC, because... in them the received current is also rectified diode bridge for better use of the inductor radiation. The second is parallel to the accumulative electrolytic capacitor C4 is connected to ceramic C5. “Electrolytes” have a large self-inductance and a significant dielectric loss tangent tgδ, which reduces the charge efficiency at operating frequencies. Bypassing the “electrolyte” with “ceramics” reduces the charging time by approx. by 7%. For a tablet with a 3500 mAh battery, this will be approx. half an hour. Agree, sometimes it’s significant.
Finally, the VD8 diode. It protects the gadget’s charge controller if it is placed on an inductor connected to wired charging. You never know what comes to mind. Maybe someone will think that double charging will charge the device faster. The charge controller will still not allow more current into the battery than it should, but it may not be able to withstand such abuse. If such a situation is excluded, then VD8 is also excluded; then VD7 is needed for a voltage of 5.6 V. Its operating current is indicated with a large margin, because the maximum charge current never passes through it due to the acute reaction to the generator load. Practically - set any low-power junk device to the required voltage. He holds it - well, let him hold it. If it gets hot, we install something more powerful and more expensive; The charge controller also has its own overvoltage protection.
Note: without VD7, the rectified voltage will be the maximum permissible in WPC 7.2 V, which allows you to charge tricky “alternative” gadgets. It can be reduced by re-soldering the hot end L2 (see below) closer to the center of the coil, but no more than 6-7 turns.
Setting up
Setting up the generator begins with setting its quiescent current Iп without excitation. To do this, L3 is turned off, and gate VT3 is connected to the common wire (item 1 in the figure), i.e. form a zero offset. Next, selecting the VD3 chain, set Ip within the specified limits. If the drain current at zero bias is less than 50 mA, IP can be set to 15-20 mA, the generator will become more economical and safer. Suddenly the initial drain current is less than 40 mA, even better, then C3 and VD3 are not needed.
The next stage is phasing the windings. To do this, you will need a probe from the receiving coil (see above) with an incandescent light bulb connected to it, pos. 2. The generator circuit is restored, turned on, and a probe is placed on L2. The light should light up. No - swap pins L2 or L3. The coils need to be phased so that the hot (farthest from the center) end L3, pos. 3. At the same stage, measure and record the operating current consumption Ip, pos. 4.
Now you need to set the safe standby current of the generator Id; The emitted power in standby mode will drop in proportion to the square of the ratio of the operating current to the standby current. Id is set by resoldering the hot lead L3 in the positions indicated in pos. 5 limits closer to the minimum value. The return to power is checked by placing a probe on L2. The installation procedure is quite tedious. To avoid tightening it and soldering until the track peels off, proceed as follows. instructions:
- L3 is reduced by half (pos. 6);
- Id turned out to be small, or the probe does not show a return to power - we return half of the discarded turns, pos. 7;
- Id is still large - we discard half of the remaining half of L3, pos. 8;
- situation according to point 2 - we return half of the turns discarded according to point 3, but not half of all discarded, pos. 9;
- if necessary, continue the setup, following the same algorithm.
Thus, using the iteration method, setting Id takes very little time.
All that remains is to configure the charge indication circuit. To do this, assemble a receiver loaded with a resistor of such a size that the charge current is less than the forming current, but greater than the content current, pos. 10. The R2 engine is placed in the lower position, the receiver is placed on L2. By rotating the engine, you achieve the glow of VD1. They remove the receiver and see if VD1 goes out. No - the engine is turned back very smoothly and carefully until VD1 goes out.
Design
Further reduction of charging time and improvement of device safety parameters can be achieved by directing the flow of energy from the inductor upward; this technique is used in some branded wireless chargers. These can be recognized by the inductor surrounded by a ring, unless very smart alternativeists just stuck it on for sales.
In fact, the radiation direction is created by shielding the inductor from the rear side. To do this, the generator is placed in an open-top housing made of thin, no more than 0.25 mm, sheet metal. If the height of the housing is indifferent to aesthetics, the generator power source is also placed in it. In this case it must be with a transformer industrial frequency on hardware: interference from a closely located UPS will disrupt the generator settings.
Steel is needed for magnetic shielding in addition to electrical shielding, and its thin thickness is needed to prevent losses due to eddy currents. For the same purpose, frequent thin vertical slits are made in the sides of the body, and the bottom is perforated in a checkerboard pattern, see fig. The ideal option is the walls and bottom of the housing made of fine-mesh steel mesh. Cover – any radio-transparent plastic without filler: glass, acrylic, fiberglass, fluorine paste, PET, PE, polypropylene, polystyrene. An option is colorless transparent acrylic or nitro varnish in 4-5 layers, but not paint or enamel. External design can be anything. It is with this design that you can keep wireless charging for your phone, smartphone, or tablet constantly on on your bedside table. Although in today’s extremely littered ether, it is still better to stay away from any known sources of EMF.
Modern Cell Phones can't do without recharging! They need to be charged at least once a day. Even old push-button mobile phones require charging at least once a week.
Converting a cell phone to wireless charging solves a lot of problems - put the phone on the nightstand near the bed and it charges automatically. But too few phones have standard wireless charging. This is what we will fix!
So, how to make wireless charging for your phone with your own hands.
Manufacturing is not difficult and even a child can do it, but, nevertheless, I recommend practicing first on an old and unnecessary phone, just in case something goes wrong.
To make a homemade wireless charger for a mobile phone, we need an SS1 diode and copper wire 0.3-0.5 mm thick.
From the wire you need to make a coil in the form of a flat spiral as in the picture below.
You need to wind 30 turns. We place this coil directly on the battery, gluing it with 2-sided tape or glue from a hot-melt gun.
Then, using a diode, we connect the coil to the battery according to the diagram below.
All that remains is to check that back cover the phone did not damage the wire spool, if there are protrusions on it that are in the way, then the cover can be modified using a Dremel.
The wireless charger itself is quite complicated to assemble yourself. And in terms of price, such a “radio constructor” will be more expensive than buying a ready-made one, fortunately on Chinese sites these chargers cost less than 10 bucks.
In order to equip your favorite smartphone with the flagship wireless charging function, you don’t need much.
Firstly, the base, also known as the charger. Most often it is made in the form of a small round platform with an outlet for a charger. For the experiment, let's take an unnamed model with a pleasant blue backlight. Powered by a 5 V, 2 A power supply ( regular USB), is powered via a standard microUSB port. At the output, the device produces a current with parameters of 5 V, 1 A, which is enough to charge most devices even in operating mode.
The second necessary element of modernization is the antenna, with the help of which the smartphone is charged from a distance. Usually this distance is minimal, by the way, but the convenience of using wirelessly can be significant for someone. For example, the database can be embedded in dashboard car or put it on the chest of drawers near the bed: came, put it down, went to bed. And no searching for wires.
There are a lot of different universal antennas for smartphones on the market. They are also suitable for other equipment, but here you need to think about placement. The antenna (we have an unnamed Chinese copy) is a coil with a circuit board hidden in a paper-like envelope. A wire with a microUSB plug comes out of it, although if desired, it can be soldered to any other one. It is worth paying attention: the coil only works in one position in relation to the charger. Since the cable for connecting to a smartphone is flat, you may need to open the bag and flip the coil over for the antenna to work (as in our case). The coil should face the open side towards the charger.
Attention: the charging base contains required parameters power supply (in the case of the used one - 5 V, 2 A). They need to be provided for. At lower current levels, charging will occur very slowly. For adequate operation, you may need to replace the cord included with the charger, since not every USB cable can pass a full 2 A. As you can see,
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