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Wireless Cellphone Charger Circuit

In this post we will try to wireless cellphone charger circuit for facilitating a cordless cellphone charging without employing a conventional charger.
Here the cellphone is required to be installed with a receiver circuit module internally and connected to the charging socket pins, for implementing the wireless charging process.

Once this is done, the cellphone simply needs to be kept over the wireless charger unit for initiating the proposed wireless charging.

In one of our earlier posts we learned a similar concept which explained the charging of a Li-ion battery through a wireless mode, here too we employ a similar technique but try to implement the same without removing the battery from the cellphone.

Also, in our previous post we comprehensively learned the basics of wireless charging, we’ll take the help of the instructions presented there and try to design the proposed wireless cellphone charger circuit.

We’ll begin with the power transmitter circuit which is the base unit and is supposed to be attached with the mains supply and for radiating the power to the cellphone module.

wireless cellphone charger circuit
Dimensions: 10 inches by 10 inches, bigger size might enable faster charging and better current output

The figure above shows the power emitter or radiator design, recall the circuit diagram from our previous post, the above design utilizes exactly the same circuit layout, although here we do it through a PCB by etching the winding layout over it.

A careful observation shows that the above layout has a pair of parallel coiled copper tracks running spirally, and forming the two halves of the transmitter coil, wherein the center tap is acquired with the aid of the linked red jumper wire across the ends of the coils.

The layout allows the design to be compact and effective for the required operations.

The track layout could be in the form of a square, or oval on one side and squarish on the other in order to make the unit even sleeker.

Rest of the portion is quite straightforward and is as per our earlier diagram, where the transistor is 2N2222 included for inducing the required high frequency oscillations and propagation.

The circuit is operated from a 12V/1.5 amp source, and the number of turns (coils) may selected approximately in accordance with the supply voltage value, that is around 15 to 20 turns for each halves of the transmitter coil. Higher turns will result in lower current and boosted voltage radiations and vice versa

When switched ON, the circuit may be expected to generate a strong magnetic flux around the coiled tracked, equivalent to the input power.

Now the radiated power needs to be absorbed using an identical circuit for executing the wireless power transfer and the intended cell phone charging.

For this we need a power collector or receiver circuit for collecting the radiated power, this may be devised as explained in the following section:

Dimension: 3 inches by 3 inches or as per the accommodation space available inside your cellphone

As may be witnessed in the above receiver design, an identical layout of the coil may seen, except that here the two concentric spirals are connected in parallel to add current in contrast to the transmitter layout which incorporated a series connection owing to the center tap restriction for the design.

The design is supposed to be small enough to fit inside a standard cellphone, just below the hind cover, and the output which is terminated through a diode may be connected either with the battery directly or across the charging socket pins (internally).

Once the above circuits are built, the transmitter circuit may be connected with the indicated DC input, and the receiver module placed right over the transmitter board, at the center.

An LED with a 1k resistor could be included at the output of the receiver circuit in order to get a instant indication of the wireless power conduction process.

After the operation is confirmed, the output from the receiver may be connected to the socket of the cell phone for checking the response of the wireless charging effect.

However before this you may want to confirm the output to the cellphone from the wireless receiver module…it should be around 5 to 6V, if it’s more, the black wire could be simply shifted and soldered a few coils towards the top until the right voltage is achieved.

Once all the confirmation are complete the module could be accommodated inside a cellphone and the connections done appropriately.

Finally, hopefully if everything is done correctly the assembly might allow you to keep the cellphone directly over the transmitter set up and enable the proposed wireless cellphone charging to happen successfully.

 

The above wireless power transfer concept was successfully tried and tested with some modifications, by Mr. Narottam Gupta who is an an avid follower of this blog.

The modified wireless cellphone charger circuit and the prototype images can be witnessed below:

 

 

 

 

203 thoughts on “Wireless Cellphone Charger Circuit

  1. hello sir, avid reader, first attempt at one of your many informative circuits. Just to clarify the main power source for the transmitter reads 12.5 volt 11.5 amp in description but in the picture it shows only 1.5 amp since the 11.5 might have an extra accidental one only because I've never heard of such a high amp DC power source sorry to bother and please never stop teaching, your ability to clarify electronic circuitry has been second to none a long overdue thank you is owed , sincerely Michael Shoop

    1. sir i tried it by making different four coils every two coils joining required points but not placed like you showed but when i connect 6volts source transistor burnt.i connected all elements as you showed in picture.What can i do to perform surely?please help me.

    2. Mohammad, I am not sure exactly how you might have connected the elements, but you can try correcting or troubleshooting the circuit by first using a 3V supply and by checking the response of the Rx at touching level..if it works then you could increase the voltage gradually until the transistor is felt warm…then you could increase the turns for reducing the warmth on the transistor and proceed so on..

  2. Hello again sir. I tried to constuct the circuit on breadboard but it is not working. I think theres a problem with the coil. is the number of coil turns on the transmitter the same also with that of the receiver. Sir please help me out. Thank you.

    1. Hello chara,

      you made the coils on breadboard?? please explain your prototype so that I can locate the fault.

      you need to do exactly as shown in the above article, if you are not able to make the PCB layout coils, then replicate it with wire coils which should be exactly identical to the PCB configuration.

      the receiver coil numbers is not crucial, more number of turns will more voltage and vice versa.

    1. Back EMF occurs in between transistor switching, when the magnetic field of the coil collapses (which is what makes it self-oscillate). This back EMF can be a spike of high voltage depending on the coil design. I suspect this is what is burning out your transistor. Try placing a 1N4001 or 1N4007 diode between the collector and power supply. This blocks the back EMF current from re-entering the collector. You may also want to protect the emitter/base junction with a 1N4001 by wiring the striped side of the diode to the base and other side to the emitter. For an example, just look on google for any "Bedini SSG" circuit which protects the transistor in the same manner.

    2. I don't think back EMF could be the problem, because it's a self oscillating circuit and not induced by an external agent, I have never seen a diode being used in self oscillating circuits for back EMF protection….may be because the coil turns are significantly less and the frequency is high.

      the problem could be due to a wrong wiring, or wrongly connected coil, or a mismatch between number of turns and input voltage.

  3. hello sir, why its not work in my project. i was trust your tutor but not work. i make coil 18 turns in transmiter n power adapter 12v/1,5amp, in receiver i make coil 24 turns. but its not work 100% . pls help 'me.

  4. Could the transmitting coil be made on transparent printer film (like the film used to transfer toner to PCB when making your own boards) and conductive ink? I was thinking of the cost of copper clad or having a 10×10 inch PCB made which would cost a lot. My idea is to use 2 sheets (legal paper size) of the transparent film and use conductive ink to draw the coil design on one sheet. Then insulate by placing another sheet over it. Use solar panel tabbing/wire to make connections with conductive glue or tape. This would also be a very thin design. Question is … could it handle the current? I'd probably have to draw the traces pretty thick and wide. Ideas ???

    1. That's possible if sufficiently thick and wide tracks are created with the ink, because the track thickness and width will determine how much current it can handle and can be manipulated by the designer….or alternatively the receiver section can be simply implemented using a pancake kind wire assembly, as shown in the video, because the compactness of the receiver may be not so important.

  5. I've taken the time to design this on a 4×4 inch PCB in Eagle CAD if anyone's interested. Willing to share as long as the files are not altered in any way. DRC rules pass for production @ OSH Park.

  6. Hello sir I have many question regarding this post .Are you tested this circuit. I have not more knowledge but I think than induce current is only for AC current . Sir you use 12 volt 1.5 amps. Can I use an invertor battery of 12v/180amps .

    Please clear me what is SWG Number of copper wire and number of turns .

    Please reply soon .
    Thanks in advances

    1. Hello Kuldeep, please go through the comments, and you'll also find video link which you can refer for more info.

      if you are new then I would recommend NOT to try this circuit because it can be very difficult for anybody who does not have a thorough practical and theoretical knowledge of electronics.

    2. I am glad you could succeed with the project, the cell phone might not be charging because of low current, try increasing the input current and check the response….or you can also try decreasing the distance between the Rx and the Tx

      sorry the distance range cannot be increased by much, that will strictly affect the performance of the output

    1. That's great Kuldeep, however BD139 should also work may be it's faulty or not connected correctly.

      you can try the other alternatives as suggested in the previous comment…a TIP122 can also be tried

  7. Sir,
    I made it but one problem,
    I get sufficient voltage in receiver but current is not sufficient. So showing the mobile is charging but mainly it's not charging or charging too slowly.

    So,plz tell me how can I increase the receiver end current ?

    I used 12V, 1Amp transformer for power supply.

    1. Narottam, try adding more number of coils parallel with your existing receiver coils, this will help to induce or absorb more current from the transmitter…also make sure the Tx transmitter is supplied with sufficient current from the power supply.

      I am afraid 12v 1amp will not do….use a 15V 3amp or 5amp..

      I would be interested to see the pics of your design with full details…it would help the many readers to understand the concept better,

  8. sir me Kuldeep Tripathi i make this circuit but i have a question related this circuit . When I supply 3 volt and 1000 milli amp so the reciving volt is 6 v please help me i want to charge my mobile of 1800 milli amp

    1. Vaibhav, do you mean to say you are getting 6V at the receiver end? If it so then you can still use it for charging your cell phone by adding a 5 ohm resistor in series with the output.

    1. Good day sir Narottam. What 2 core copper wire did you use? And what awg of receiver did you use and how many turns did you apply? Sorry for the questions but I am currently needing your answer. Thank you and have a great day.

  9. Sir,
    In transmitter circuit how can produced high frequency power ?
    By using transistor, but for transistor switching needs a continuous pulse,here the transistor from where get that type of pulse ?

    Please explain…

    (Actually my teacher asked me that type of question but I can't explain properly.)

  10. Hi sir. I wanna make a wireless charging which is like yours, but I uses Galaxy S6 from Samsung and it has a NFC to it which also can be use for wireless charging. So did I still need a receiver module or I can directly put my phone on top of it? If you got the answer please send it to my email on letsmake0470@gmail.com

  11. Sir I'm a novice at this, I did everything exactly as I saw it except my coil doesn't have up to 15 turns, when I power it my 2n222a gets very hot and burns, is it because of the coil or is there anything else I can do about it ?

    1. Michael, yes it could be because you reduced the number of turns…in that case you can try reducing the supply voltage to a lower value and check the response

  12. Pardon me sir. With all due respect, how can this be a wireless charger if usb cable is still needed to be connected to the receiver?

    Thanks btw for your informative thread. We need more people like you sir. Salute!

    1. Good observation Mharlee, thanks! The shown experiment using USB wire is just a prototype which confirms two things: the wireless power transfer concept and the successful charging of a cell phone using this concept….the USB wire can be ultimately eliminated once the receiver circuit is somehow accommodated inside the cellphone back cover…once this is done, the cellphone will not require any form of wire and could be charged just by placing it over the transmitter unit.

    1. If you did everything right, then it should have worked.

      I have referred a video link in one of the above comments, please watch that video, it might help you troubleshoot your design.

    1. Sagarneel, please go through all the comments, I am sure it will help you understand the issue and find a solution…or you can try with a lower supply voltage and try increasing it only upto the point where your transistor is not heating up.

    1. hello domnic, there's no ideal number,because the coil dimension is strictly related to volatge frequency, and current…so all these needs to be perfectly optimized through some trial and error to get the maximum efficiency.

      technically wire gauge must be thinner for the transmitter and thicker for the receiver

  13. My 2n2222a keeps burning out, and I have to replace it every time .
    What do I do about that, if I'm to reduce the power or voltage, how do I do it .
    PS, my power source is usually my laptops USB port

  14. Sir I made the revised one with the TIP35C and we got an ouput of 5.4 V and 1.4 amp in the receiver end and the phone is charging but the problem is the transitor is getting very hot to the point that it emits smoke. We tried heat sink and it failed. Our source is 12V 2 amp. Thank you !

    1. Carmelita, the transistor will become hot if the inductor and the transistor does not oscillate at an efficient rate, which might lead to the consumption of excess current by the transistor.

      Try increasing the number of turns of the transmitter coil or try reducing the voltage until the transistor operates at a cooler temperature

  15. i would like to know how can i parallel my transmitter coil? i want to add more turns so instead of making another one from scratch i want to create a coil and then add it to the one im using. thank you very much. 🙂

  16. sir thanks for your quick response, i have another question. What transistor can i use instead of tip35c? i want a transistor which can hold more heat. im using a 12v 2amp adapter. I had an output of 5V and 1 amp and a coil distance of almost 1 1/2 inch.

  17. Hello Sir,
    Thank you very much for all the useful information you spend time and knowledge to spread on your website !

    I'd like to get out of the "trial and error" area, as I need to design a reliable circuit that could receive 9V at 400mA (minimum values) from a 12v power source on the emitter side. Coils diameter must be <40mm and the two coils will be distant of 1 millimeter.

    I assume that there are laws and equations behind the transmitting efficiency, voltage levels, and efficient commutation frequency for the transistor, but couldn't find it yet… If you know them and don't mind sharing, it would be greatly appreciated 🙂
    Best regards, Julien

    1. Hello Julien,

      The most efficient response can be detected and found only through a practical trial and error method….because formulas can have issues due to incorrect selection of the parameters, but a practical approach will always be precise.

      The efficiency will hit the max when the two coils oscillate at their resonant frequency…the resonant point must lock across the coils, that's the critical thing we have too consider while optimizing the two.

      Instead of the transistor/inductor "blocking" type of oscillator you can try other forms of oscillators using IC 555, IC 4060, or through half-bridge driver ICs which will allow you to investigate wider ranges….

    2. Hello Swagatam,

      Thank you again for your detailed answer. I perfectly understand that real tests are the most efficient way to get reliable results, but I would have liked to save time, by approaching the optimized config with calculations…

      Thank you for pointing out other methods, I'll have a look further if I can't make it with the blocking oscillator principle…
      I may come back to you soon if I find something interesting 🙂
      Have a good day,
      Best regards, Julien

  18. what should be the number of turns in the transmitter coil as well as the receiver coil? and what is the SWG of both the coils? Please, sir tell me as soon as possible. I making this project in college. Help me.

  19. Hi Allen, the leads are obviously connected with the (+)(-) terminals of the coil output (after the diode), it is not visible because it's shown as being inserted from the other side of the board.

    For details please refer to the images which are posted at the end of the post, the one which is drawn with pen.

  20. sir i did all that shown on video but when i cnnct to mobile phone it charging for two minutes then after adopter getting hot and it stops working when i use small led it working continuosly

  21. sir im getting output at a distance of 2 inches i used 12v 1.5A adopter and tip 35c transistor and coil which is shown on the video u posted above but when i connect mobile phone its just chrgng for 2min then after adopter getting hot and stops working i think supply will be less can i use 12v 4A for tip35c transistor

  22. Sir, i appreciated you noticing my question. Another question sir, in your 1N4007 rectifier diode, what is the specific voltage of that rectifier? Your answer is very much appreciated. Have a good day ☺

  23. sir is there any alternative without using other adopter is there any other reason for adopter heating sir give me formulas and theoretical derivation sir in pdf any link

  24. sir iam using 30swg for transmitter and receiver for tx 18 turns two core flat spiral coil and for rx nearly 60 turns like wound coil is there any method to reduce the adopter heating by changing the windng turns or other

  25. Sir, I was able to light a LED using the modified circuit however, the TIP35C gets really hot. Can you share substitutes for the TIP35C that can bear the electrical flow? by the way, my aim is still to charge the phone. I hope you can give me answers and it will be much appreciated.

    Best regards.

    1. Allen, TIP35 is not the problem, in-fact TIP35 is an overkill, your circuit should work even with a TIP31 transistor.

      make sure the coil turns are tightly wound without gaps within the turns, and try increasing the number of turns with respect to the center tap, and see if that cools the transistor.

  26. Sir, thank you for answering. i now have a clearer concept. i will tighten wind the turns later.

    I am currently using TIP35C. I am using 470 ohm resistor and have 18 turns. Will that be enough for the circuit to work? Thank you so much. have a great day.

    Best regards.

    1. Ronnel, move the Tx coil it closer to the Tx coil and see if the voltage in increasing or not….if not then your assumption regarding the wireless transfer might not be correct…first confirm this then we can move ahead.

  27. Hello sir iam adnan. iam also working of wirless power transfer. i made a project in which i have charge a mobile but now iam want to increase its effeciency so that it will able to charge a laptop and i used tesla bifilar coil for transmitting with a radius of one feet and unifolar recieving coil of nearly 8 inches power recieve will be aproximately 8wat. can i increase this power level by using multiple coils on recieving side or any other advise so you give me to achieve my goal. kindly reply i will wait for your suggestion

    1. Hello Adi, the transmitter and the receiver coils should be designed to resonate at optimal levels, that's the key to make the most efficient and powerful wireless transfer.

      The concept explained in the following link is similar to wireless power transfer and you can replicate the concept for your specific application….however the wire gauge must be correctly calculated as per the current demand of the system.

      http://www.homemade-circuits.com/2016/09/designing-induction-heater-circuit.html

  28. Hello sir,

    is it necessary to connect capacitor and diode in receiver circuit. I am connecting only led with two coils of copper wire in receiver section and it's not glowing.
    Please help me…
    Thank you

  29. Dear sir,
    i had test you circuit it is working well. i didn't use 7805. i check with LED. it is glowing.
    now i want to ask you, can we use 5volt mobile charger instead of 12volt 1.5A charger? it will help to remove 7805.

    1. Ninad, a cellphone charger could be much weaker with its current and voltage so the LED would also illuminate dimly….the receiver output will be directly proportional to the transmitter output which in turn will depend on the power of the supply used

    1. Iqbal, it won't be possible due to lack of time, the concept has been discussed elaborately above which you can go through and design it yourself through some trial and error.

    1. Iqbal, how do you want to connect the coils? One above the other, or separately for different receivers?

      To use it separately you may have to use separate circuits for each of the coils.

  30. Sampath

    If u don't mine Sir can u explian the concept clearly in detail please I have made the circuit can u explain me how the currents and fields flow in the coils in detail please

    1. The process is exactly similar to our transformer concept, the only difference being the coil distances which are completely isolated in wireless transfer concept, whereas in transformers the cols are wound one over the other.

  31. Sampath
    1.Sir i want to know the transistor internal operations how currents going through switching of base collector emitter plz help me this out how it is converting Dc to ac in the above CkT
    2.Plz tell me is it possible with 18 guage copper for greater output in the circuit u have shown above

  32. Sampath
    1.Sir i want to know the transistor internal operations how currents going through switching of base collector emitter plz help me this out how it is converting Dc to ac in the above CkT
    2.Plz tell me is it possible with 18 guage copper for greater output in the circuit u have shown above

    1. Current enters the center tap of the coil and reaches the base of the transistor through one of half winding of the coil.
      This triggers the transistor which instantly shorts the center tap current to ground through the other half winding, which removes the current from its base.

      This forces the transistor to switch OFF, reverting the circuit to its initial position and the process repeats itself causing a rapid push pull oscillation on the coil….

  33. Sampath
    Sir how much guage wire u used in above circuit you made I made it with 30 guage copper wire but it not geting Better current output it getting output very less is it possible with 18 guage wire for greater output in the above circuit

  34. Sampath
    Sir I'm saying that I used 30 guage wire for transmitter and same for receiver also I saying that I want to use 18 guage wire for transmitter for greater output ,replacing 30 guage wire with 18 guage wire is it possible high output with which wire

    1. use 3 or 4 numbers of 30 SWG wire in parallel (together) and wind the coils, and check out the response…

      a single 18 SWG will not be efficient…

      I hope you understood what I am trying to suggest??

      but anyway you can try a single 18 swg also, it's your wish

  35. Sampath
    Sir
    U made the above circuit is u used PVC or super enamel copper wire if u used PVC then what no. Of cu.Guage wire I should use or if use super enameled cu wire then tell me the guage no. I m making new one
    2.whats the use of resistors at the base why

  36. sorry sir iam asking about the operation of resistor which is connected at the base is by connecting the resistors at the base more current is drawn at the base of transister, sir tell me that what is the use for by connecting the resistors at the base can u reply me fast sir

  37. Sir I understood that base resistors r used to limit the base current of the the transistor sir how did u calculate the resistor value 220ohms for 2n2222a transistor , I used tip35c with two 220ohms resistors in series at the base as shown in the video can u show me the calculations sir reply me quickly sir

    1. Sampath, it was not calculated, it was referred from other online examples….although it can be calculated using the following formula.

      R = (Us – 0.6)Hfe/Load Current,

      Where R = base resistor of the transistor,

      Us = Source or the trigger voltage to the base resistor,

      Hfe = Forward current gain of the transistor,

  38. Sir is it possible greater output I used tip35c transistor in the place of 2n2222a transistor in the above circuit
    And I used 2 220ohms base resistors can I reduce the base resistor for greater output sir reply me

    1. Sampath, greater output can be achieved by matching resonance between the Tx and Rx, which can be done by adding capacitors across the coils. Using higher power is a secondary option which can be tried after fixing the resonance.

      I'll soon publish a detailed article explaining this.

  39. Dear sir Swagatam, I am really interested in this post. Would u like to send me the newest diagram circuit and detailed information please. I would appreciated it. Thanks

  40. I'm trying to build wirless mobile charger using the following circuit but I can't figure the no of turn of the transmission and receiver coil can u please find it for me.can i have your email coz i can't attach the photo into this comment

    Please reply ASAP
    Thank u

    1. Lochana, the waveform can be confirmed only through an oscilloscope, most probably it should be a distorted square wave or sawtooth type.
      without center tap this oscillator will simply fail to oscillate, because one of the winding of the coil helps to maintain the required feedback for sustaining the oscillations.

    1. for the above design don't add to the transmitter…add only to the receiver coil, and keep tweaking value until you find the highest achievable voltage output from the Rx….

  41. Sir I got doubt that u said that current enters center tap coil through one half winding say winding 1 reaches base which triggers transistor means on which shorts collecter and emiiter current flows collector to emitter to gnd through other half winding say winding 2. how can base current removed from which half winding to turn off transistor

    1. begin by applying 3V and then slowly increasing until the point where the transistor begins getting hot.

      make sure the circuit is oscillating through a frequency meter.

      alternatively you can try adding more turns until the transistor stops heating up.

    1. Sir,I did this project and got the output.I just need to give a presentation on it by tomorrow wherein i will be questioned about how exactly every component is used.U asked me to watch for blocking oscillator but i cudnt relate it to this ckt.Can u please give me a detailed info about how exactly every component from both transmitter and receiver is used. It will save me from the presentation tomorrow.

    2. DP, that's great and congrats to you.

      The design of the above wireless transmitter circuit is exactly of a blocking oscillator, you can compare the diagram shown in the following article with the above concept and you will find them to be exactly similar:

      http://www.homemade-circuits.com/2017/04/blocking-oscillator-circuit-how-it-works.html

      a comprehensive explanation of the circuit functioning is provided in the above linked article, however it looks much too elaborate and complex for any newcomer

  42. 1n4007 is too slow diode for this circuit. It is designed for 50Hz and 60Hz line frequency rectification. A fast diode like UF/SF4007 or 1n4148 would work better.

  43. Dear Guru,
    Since there is no PWM fed to drive the transistor then at what frequency a single transistor when wired to self oscillate put out?

    On the receiver coil which configuration rectifier would work best?

    What could be done in order to regulate the output voltage from the coil?
    Thanks

  44. Hi Sir
    If I am increasing the number of turns of the sender coil than should I also have to increase the receivers coil.
    And also if I am increasing no. Of turns of sender coif than should I have to increase the battery source.
    Can I use a Normal Samsung Data cable charger .
    I am using 2N2222 transister will it be able to hold the charge produced by a mobile phone charger.

    SIR PLEASE REPLY AS EARLY AS POSSIBLE
    THANKYOU SOO MUCH

    1. Hi Parth, the transmitter coil and receiver have no direct connection. The receiver coil parameters can be increased for optimizing more current and voltage.

      whereas the transmitter coil parameters may need to be optimized for better resonance so that maximum current can be transfered to the receiver coil.

      therefore both are independent of each other and they may be tweaked for achieving different specifications.

      however exchanging optimal current across th etwo cols is the main requirement.

      remember if you change the transmitter coil turns then you may have to change the supply voltage accordingly and check the response until you get the best possible frequency and resonance for the coil

  45. Hi , I would like to know if could be possible to share the picture of the coil of the transmitter part without the wires and transistor. I want to print on a PCB the spiral coil to test it.
    Thanks in advance.

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