Wireless Charging and How to Make Wireless Charger

(Last Updated On: September 12, 2021)

Wireless charging:

Wireless charging at least in its current state is kind of misleading compared to wireless internet or a wireless game controller. Wireless charging requires such close proximity between your phone and a pad that to be honest a better name would just be contact charging. A wireless charging is a different ballgame altogether and it is already here sort of so the current standard is something that we call QI wireless charging and it works with two coils one that has to be built into the phone and the other that comes inside the wireless charging pad put those two coils close to each other provide some power and you have got an electromagnetic field between the two which your phone can then convert back to power. So that’s great but with a total range of about four centimetres. It is not really solving the problem of you having to put your phone somewhere for it to start charging add to this if you want to pick your phone up to type something the charging has to stop. Whereas with a wired connection your phone can keep going the point is just that the current generation Chi Tec is just not that great but there is a company called  Energous who is doing something a little bit different instead of converting electricity into an electromagnetic field they have built a hub that converts it into radio frequencies which can then be fired up to 15 feet away almost any kind of device can pick up these frequencies and convert back to electricity that is huge and to be honest smartphones are one thing but it’s bigger than that if you think about your home. It is probably filled with lots of gadgets that slowly sip away a batteries all the time you have got things like wireless headphones game controllers hearing aids these would never need to be charged again by installing a true wireless charging hub. You could constantly be providing power to every device in a room it could even work in a car you could sit down put your phone in a cup holder put your headphones on the seat next to you and by the time you’ve reached work in the morning they would both have more battery than when you left. In fact things get even cooler when you think about the potential future here if we reach a stage where there’s wireless power everywhere your smartphones your laptops your gadgets don’t need to have a battery built into them. so theoretically you could have a full quality flagship phone that weighs no more than 80 and has no more than three millimetres thick and we’re getting there in fact spigen has already announced the forever smartphone case which will release in 2020 and can be wirelessly charged from a distance of 12 feet worth bearing in mind is that this tech isn’t quite very yet there’s a reason it’s been in the works for over 10 years now and we still have barely seen a retail ready product.



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Fast Wireless Charger, NANAMI Qi

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TOZO W1 Wireless Charger

Thin Aviation Aluminum Computer Numerical Control Technology Fast Charging Pad Black (NO AC Adapter). Supports all enabled wireless charging devices or devices with receiver such as for iPhone 12/12 mini/12 Pro/12 Pro Max/11/11 Pro/11 Pro Max/XS MAX/XR/XS/X/8/8 Plus/SE2/Airpod/Airpods Pro; Samsung Galaxy S20/S20+/S10/S10+/S10E/S9Galaxy Note 20/20+/10/10+/S9/S9+/S8/S8+; Google Pixel 4/4XL/3/3XL, Google Nexus 7 ; LG G7/6/6 plus/S6/S6 Edge/S6 Edge Plus/Moto Droid Turbo, Nexus 5/7/4, Nokia Lumia 1020/920/928, MOTO Droid Maxx/Droid Mini and Other Enabled Phones and Tablets.

Belkin 3-in-1 Wireless Charger

(Wireless Charging Station for iPhone, Apple Watch, AirPods) Wireless Charging Dock, iPhone Charging Dock, Apple Watch Charging Stand. Works with iPhone SE, 11, 11 Pro, 11 Pro Max, XS, XS Max, XR, X, 8, 8 Plus, Apple Watch 5, 4, 3, 2, 1, AirPods 2, AirPods Pro.

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Problems in the wireless charging:

The first problem and to be honest the biggest problem is the fact that the radio frequencies that are fired off by the base station they lose energy very quickly as they travel through air which means that by the time your device receives those waves it’s not getting the same amount of energy that was initially provided to the charger take this product the mother box marketed as the world’s first true wireless charger and the concept is beautiful the product looks great and when your phone is that close to it an charge with a full 10 watts of power which is fast by wireless charging standards. How quickly this power Falls with distance it all seems reasonable enough until you realize that by the time this power output has fallen from 10 watts to just 2 watts. You are only 16 inches away or about 40 centimetres that’s barely enough to even use your phone on your bed even if the charger was on a bedside table right next to you so when we move beyond these distances we are talking milliwatts which mind you is enough to keep a game controller juiced up but not enough to charge a phone from across the room in fact your phone on standby will consume more power than this box can feed from a distance. So all you’d really be doing is slowing down how fast the battery is draining not actually increasing the battery percentage there’s also a second caveat because this whole system works based on a transmitter and a receiver until it becomes mainstream enough for companies to start building the receivers inside the gadgets you’re gonna have to use something external and it doesn’t look pretty some sort of pad that you need to keep plugged in to your gadget or like I showed you earlier a case which is not the worst solution but the thing to remember is that it’s a transitional phase just like we’ve seen with notches on smartphone displays it doesn’t look pretty.




How to make wireless charger from coils:

We will take a copper wire and make a coil of 15 + 15 turns such that one terminal of the wire will get after 15 turns and another terminal after 15 turns. We will have three terminals in the coil. We will connect one terminal of the coil with the adapter, one terminal with the 2n2222 transistor base and the third terminal of the coil with the collector of the 2n2222 transistor. The emitter of the transistor is connected with the other terminal of the adapter.

Wireless Charging

Now we will make the receiver for the mobile for which we will make another coil of 20 turns and connect the micro USB plug with it. Connect one terminal of the USB cable with the coil one terminal and another terminal of the coil with another terminal of the USB plug

Wireless Charging



Wireless charging working:

Nowadays when it is time to charge your phone using a micro USB cable is not the only available option anymore. There also exist wireless charging stations that can transfer sufficient energy literally through the Air. A Close relative to such wireless chargers is the well-known Transformer which can also transmit energy without the need of a wired connection as well. But the question is how we can alter the booking behaviour of this big and heavy transformer in order to transmit energy solely through the Air. Let’s find out First of let’s talk about the working behaviour of the transformer Just like every other common one it consists of a primary coil and a secondary coil that are placed inside a closed iron core. By applying a 50 Hertz sine wave voltage to the primary coil current flows through it which therefore possesses a magnetic field strength and creates a magnetic flux density. But most importantly it creates a magnetic flux which flows through the entire core and thus reaches the second coil. Nevertheless a very small portion of this flux though will not reach the other coil and thus create a leakage flux. You can actually compare this behaviour to an electrical circuit while the iron core has a relatively low resistance due to its magnetic permeability of around three hundred to ten thousand. The air around the iron has a much higher resistance due to its permeability of only one. Since current on this case the Magnetic flux choose the way of least resistance. Most of it will flow through the iron but leakage flux still does exist and because we originally apply the sine voltage to the primary. We have created a sine current and sine flux which is luckily just what we need to induce a voltage into the secondary. After hooking up a load to it we can observe that we successfully transferred energy wirelessly. As soon as I lifted off the iron section and furthermore even removed the coils from the iron core the dream of wireless charging through the Air fell apart rather quickly.

Wireless Charging

To find a solution to that problem Let’s go back to the traditional transformer setup the “T” equivalent circuit diagram describes the working behaviour of our Transformer well enough to understand the main problem. The resistance of the primary and secondary Coil will represents the copper losses. The leakage inductance of the primary and secondary will represent the leakage flux and finally the losses of the iron core through Eddy currents and the hysteresis.

If no load is attached on the secondary most current will flow through the cross impedance. This way the input current will have a phase shift of 90 degrees compared to the voltage. Because the inductive component of the iron core dominates which is also the main reason for the output voltage. If you would short circuit the secondary coil most current would flow through the serial impedance which is proven by the phase shift of the input current which is now almost zero degrees because the leakage inductances are rather small. But if we go back to the no load circuit and remove the i section of the core the voltage on the output collapses because even though the inductance of the coil decreases drastically with this removal the leakage inductance is no bigger than the cross impedance. This means according to a simple voltage divider almost all of the input voltage will drop across the leakage inductance instead of the cross impedance and thus the voltage on the output decreases drastically. This leakage inductance is dependent on the coupling factor which basically describes how much of the primary flux will reach the secondary coil.



In our case though the coupling factor will always be small due to air coupling so the solution is to add a capacitor in series which will near its resonance frequency cancel out the effect of the leakage inductance. In my case my 1.1 milli henry coil will receive a 100 nano farad capacitor which should equal a resonance frequency of around 15.2 kilohertz. After adding a small load on the secondary and powering the primary with my function generator. Near the resonance frequency we can see pretty much nothing what I forgot was to add another 100 nanofarad capacitor in parallel to the secondary to achieve the same effect as with the primary. This time the led finally lights up and showcases that you can actually put a decent distance between the primary and secondary. Even bigger loads like this 1W led can be lit solely by using my – let’s be honest not well tuned resonator circuit.

Wireless Charging

Modern Wireless charging stations are definitely a bit more advanced. But also use a high resonance frequency in this case of slightly above 130 kilohertz.

But that does not mean that they are perfect while charging my smartphone with the traditional wire connection the charging process required 9283 milliwatt hours. Now if I repeat that same charging process with the wireless energy transfer it required 15168 milliwatt hours that is around 1.6 times as much and clearly shows that the efficiency is certainly not the best at the moment. Additionally the utilized Qi standard contains a communication protocol which makes it almost impossible to rebuild a Qi charging station by ourselves.

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About the Author: Engr Fahad

My name is Shahzada Fahad and I am an Electrical Engineer. I have been doing Job in UAE as a site engineer in an Electrical Construction Company. Currently, I am running my own YouTube channel "Electronic Clinic", and managing this Website. My Hobbies are * Watching Movies * Music * Martial Arts * Photography * Travelling * Make Sketches and so on...

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