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Wireless Cellphone Charger Circuit

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.

The Objective

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.

The Transmitter (Tx) Coil Specifications:

The transmitter circuit for this wireless cellphone charger is the crucial stage and must be built accurately, and it must be structured as per the popular Tesla's pancake coil arrangement as shown below:


Making a PCB version of the above Pancake coil.

Inspired from the above theory, the smaller layout  of the same coil can be etched over a PCB as shown in the following diagram, and wired as indicated:

Wireless PCB version of Pancake coil

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, also 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.

Making a Practical Prototype

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:

modified wireless cellphone charger circuit and the prototype images
Wireless cell phone charger circuit
wireless cellphone charger circuit
wireless cellphone charger circuit testing results
how to make the coil

About the Author

I am an electronic engineer (dipIETE ), hobbyist, inventor, schematic/PCB designer, manufacturer. I am also the founder of the website: https://www.homemade-circuits.com/, where I love sharing my innovative circuit ideas and tutorials. If you have any circuit related query, you may interact through comments, I'll be most happy to help!

262 thoughts on “Wireless Cellphone Charger Circuit”

  1. Howdy, Friend! Interested to Learn Circuit Designing? Let's Start Discussing below!
  2. Hi,
    I’m beginner in this… But i made one(Transmitter) but ended up frying the 2N2222A Transistor(I think so), it got hot and kind of I think smoke was produced when connected to 5V 1.2A mobile charger…
    Well, I didn’t made a receiver as my phone has wireless charging feature in-built.
    Can you help me solve this riddle… It would be great if you did so…

    • Hi, If you built it exactly as per the shown diagram, then it should work. The transistor will burn if its pins are wrongly assigned or if the coil terminals are wrongly wired…please recheck everything and try again.

      • Actually, how many turns is required for the coil, i only made 15 turns with speaker wire…
        I used a 330ohm resistor instead of 220ohm….
        i joined the first wire from the outermost layer and second wire from the innermost layer and connected it to the positive of usb. And connected Left terminal( or emmitor of transistor to negative of usb) . And connected the middle terminal (or collector) to the resistor which is then connected to the first from the innermost layer.
        And then connected the left terminal(or base) of transistor to the first wire in the outermost layer of the coil…

        I hope the connections are okay… Please correct me if there is any mistake…

          • Hi it’s me again,
            I tried again as the diagram but still ended up melting the transistor 2n2222a(it’s outer part got melted). And eventually the coil became an electromagnet…
            Do I need a capacitor, usually a capacitor is required for resonance to happen….
            Can you help me…

            • Hi Joshua,
              the number of turns, the diameter and the compactness of the coil all are crucial for proper functioning of the circuit, check whether all theses parameters are satisfied or not. Also, try TIP35 instead which is a 25 amp transistor and might be impossible to burn with a cell phone charger unless the pins are wrongly connected.

              The diameter of the transmitter coil is around 16 cm.

              A resonance capacitor might improve the results, but it will need to be fixed with some trial and error.

          • Hi, can you tell me one more thing… What kind of wire is used to make the coil to get exactly 16cm diameter with only just 20 turns…

            • Hi, 16 cm is not a critical value, it may be 16, 17 or 18, depending on the diameter and the insulation thickness of the wire, just make sure it is not less than 20 turns and is tightly wound as shown in the image.

          • And one more thing I thought of using 1mF capacitor which is 63v , would that be okay with this circuit…

            • where did you use the capacitor? if it’s for resonance then you may have to calculate it correctly otherwise it may reduce the efficiency of the circuit

  3. i wont do this project but dose it realy work,(i wanna know if it realy works cause i tried it with a wireless electricity circuit and it didint work so ended up having to use a one transister circuit).

    • coil turns, supply voltage and current all these will need to be optimized to increase the range… to a certain extent

  4. Sir what is the use of Tesla coil since i have made the transmitter and receiver coil as that of the receiver coil in the practical version shown by mr narottam. I have connected the receiver ends directly to led and phone in parralel but only led glows and as soon i connect to phone led turns off.Therefore does adding a capacitor in parallel to inductor and then setting to resonant frequency would increase the voltage in receiver than the initial voltage i produced.I am using a turbo charger moto g5 s plus.Thanks in advance and sorry for such a long comment.

    • Hi Pra, yes definitely, the resonance is the key factor in all wireless power transfer concepts, without this your system will not work with the required efficiency level. Therefore fixing maximum resonance is very crucial to get optimal results. The other factor is determining the wire turns and thickness as per the load specs, for low voltage high current load such as cellphone, the coils must have lower number of turns, lower operating voltage and higher current supply.

      • Here the Tesla coil’s special configuration allows the use of a single transistor for forcing the oscillations in it, and it allows the Tx to become flat and sleek.

      • Thanks for such a swift delivery of the solution.Sir correct me of i am wrong,from my understanding it is the voltage in the secondary coil that determines the current to charge the battery.But in mutual induction if i increase the voltage in secondary coil the current would become less and vice versa.Therefore my question is that, mutual inductance should be increased or decreased ,or say it that way should i increase the no of turns in secondary coil or decrease?Thanks and please bear with me since i am a novice school boy curious to know everything.

        • since the above concept is a kind of transformer, mutual induction is the only way to transfer power here. In any transformer mutual induction can be improved by using improving the core efficiency and winding methods, since here there’s no core therefore there’s no way to enhance mutual induction, that is why we have to introduce the resonance concept so that the two winding are able to latch-in for genearting maximum efficiency.

          The main thing that needs to be tweaked is the Tx coil and frequency matching, once this is achieved the secondary Rx coil can be experimented and optimized with much ease, by trying different number of turns and distances from the Tx coil

          • Thanks sir for your advice.I understood that resonance frequency is the best possible option for maximum efficiency.To match resonance frequency of Rx by Tx there are two option first of by trying different no of Tx coil turns and second the variable volatge supply.For the first one i am not sure how to change the no of turns again and again but for variable voltage should i use the variable voltage regulator just like LM317T. Thanks in advance sir you are a true help to me.โ˜บ?

            • I am glad you are understanding Pra, yes you can use LM317 variable voltage and begin testing with the lowest voltage may be 3V and gradually increase the voltage until you find sweet spot where the self oscillating frequency strikes the resonance point of the LC tank, or as long as the transistor temperature does not cross the tolerable limits. Make sure to use a BIG heatsink for the LM317

  5. Sir , i went through all the comment and found that maximum are facing the problem due to heating of the transistor …. So i want to ask u that if i take all the components with the the same specs ….what should be maximum input voltage and current in the transmitter to protect 2N2222 transistor from getting hot ….plz reply sir and thankyou for sharing this beautiful idea

    • Prasoon, people are having trouble because they are using mismatched figures, the transistor will heat up if the circuit does not oscillate optimally at the resonant frequency, and this can be reached only when the voltage and the number of turns are perfectly matched, which will in turn ensure the correct resonant frequency. since these parameters are not critical, it can be achieved with some understanding, patience and skill, by tweaking the coil diameter, number of turns, and the voltage level…..

      the easiest way is to start with the lowest (3V) application, and slowly increase it to the maximum until the right resonance is struck, having said this one must remember that the Tranmitter (Tx) coil is the crucial element here which must be built accurately otherwise the system will simply not work, causing heating up of the BJT and damage.

    • Jomar, it can be perhaps done by adding a calculated resistor in series with the Tx power supply, and adding an LED in parallel with this resistor….when the mobile is connected, the current will increase which in turn will give rise to a potential difference across this resistor illuminating the LED.

    • Hi,
      I have connected everything as per the diagram with a TIP122 transistor and 330ohm resistor with speaker wire pancake coil. But the problem is that I couldn’t even light up an led in secondary coil. Also I have connected an led on the power supply of the transmitter but it is blinking every second what’s the reason for all that?please reply soon……Thanks in advance..

      • Hi, your system must oscillate, and oscillate at the resonant frequency, only then you will be able to get the results correctly….it will be difficult for me to troubleshoot your circuit because I cannot judge what you might have missed in your design.

        you can refer to the comments above for getting more info regarding the concept and the circuit…or you can try watching some related youtube videos for the same…

        • Hi,
          These are my components please find what is missing
          For tx,
          One 330ohm resistor
          One TIP122 transistor
          Speaker wire pancake coil(30 turns)
          For RX,
          One 100 micro farad capacitor
          One 1n4007 diode
          Coil made of speaker wire(10 turns)

          • Your parts may be right but they should be correctly configured and especially the coil, which is very crucial, a slight mistake in the col configuration will stop the circuit from working….

            In the original diagram a Darlington transistor was not used so you can replace the TIP122 with any ordinary 1 amp BJt such as a 2N2222 or even 2N3055 will do…try this…and begin adjusting the voltage from 3V and gradually increase it until hopefully you are able to touch the resonance level.

    • Hi,
      I have connected every thing and I powered it and I could detect high magnetic field with EMF detector will it mean that my tx is working properly….. ๐Ÿ™‚ ๐Ÿ™‚

      • yes then it could be working, you can test it by keep another coil right on the Tx coil, and connect an LED across the ends with a 100 ohm series resistor…if it illuminates then you can be sure it’s working

            • check with a frequency meter whether your circuit is generating frequency or not!. or try increasing the voltage slightly and check the response!

          • Hi,
            I have changed the led to 1watt led and added a resonant capacitor to it when I keep it above the tx and power on, when I shake the circuit it blinks
            Is it necessary to use the same wire as secondary coil that is used in tx coil?
            Any way thank you very much for your guidance ….:)
            Please reply soon……

            • So it seems now you are able to light up the LED on Rx, right?

              if you have added a resonant cap then try to further adjust its value until you can get the maximum efficiency and maximum brightness on the LED from maximum possible distance.

              same wire spec is absolutely not necessary, the wire thickness is related to current of the load, however the Rx coil turn nos should preferably match with the Tx.

              you are welcome!

          • Thank You very much….
            Iam using mobile phone adapter of 5v 2A . Is it OK? I will provide a link later after I upload a video on this project on youtube, If you can solve the problem it will be very helpful for me………

            • I think the power supply should be a variable type so that you are able to vary the voltage and adjust it for getting the best possible outcome….sure, I’ll be glad to see the video.

    • Hi,
      I have changed the circuit and added 555timer and FET MOSFET with resonant capacitor as I couldn’t light up an led in the given diagram that is with a single transistor , I think that when I connect the two terminals then the supply is shorted so when I shake it it blinks for a second then cutoff. Iam giving you a link so that you could check the diagram I followed…… I will put the video tomorrow…..

  6. Sir,
    I made a pancake coil with 30turns out of a normal speaker wire. Can I proceed with placing a TIP transistor , diodes and capacitors as shown in the diagram.
    Please reply soon, its for my ‘wireless charger for Mobile phone’ project for my Science exhibition.

  7. 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.


    • 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

  8. 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?

    • 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.

    • 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:


      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

  9. 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

    • Sampath, please see the following diagram


      as soon as the transistor triggers the 3V is sucked in by the transistor collector which inhibits the 3V towards the transistor base.

    • 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….

  10. sir,
    can you tell me the voltage and current wave forms through the coils?
    also why a center tapped coil instead of a normal one?
    thank u

    • 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.

  11. 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

  12. 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

  13. 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

    • 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.

  14. 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

    • 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,

  15. 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

  16. Sampath
    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

  17. 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

    • 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

  18. 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

    • you can try winding 3 or 4 numbers of 30 SWG wire in parallel, and check out the response…

      a single 18 SWG will not be efficient…

  19. 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

    • 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….

  20. 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

    • 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.

  21. 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

    • 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.

  22. 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.

    • 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

  23. 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

  24. 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

  25. Sir, I got small voltage in the receiver, How to make it 5v? What I did is I made a total of 30 turns in tx and the same in rx. Thank you very much!

    • 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.

  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.

  27. 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.

    • 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.

  28. 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

  29. 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

  30. 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 โ˜บ

  31. 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

  32. 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.

  33. 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.

  34. 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 ๐Ÿ™‚
    Best regards, Julien

    • 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….

    • 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 ๐Ÿ™‚
      Have a good day,
      Best regards, Julien

  35. 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.

  36. 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. ๐Ÿ™‚

  37. 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 !

  38. 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

  39. Hello sir. Is it okey we use #18 wire for transmitter and #26 wire in receiver? How about the ideal number of turns for the coil? Do we need to compute?

    • 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

    • 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.

    • 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.

  40. 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!

    • 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.

  41. 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 ?

    • 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

  42. 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

  43. 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.)

  44. Hi sir I have a new idea regarding this project . why we not use this circuit as a hand gulf . how future stoic it look .

    Please make some comments on this idea

    • 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.

  45. 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

    • 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.

  46. 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.

    • 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,

  47. Hello sir i made this circuit it is working good but I use 2N3904 and it get hot on few minute so please give name of a better Transistor .I also use BD139 but it not work

  48. 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

    • 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.

    • 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

  49. 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.

  50. 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 ???

    • 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.

  51. 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.

    • I have checked it myself and it worked for me, see the video above for more info, if still you cannot make then sorry i can't help.

  52. Hello watched that video
    Done editing but still there is no output in my secondary coil .
    BTW i m using a old samsung mobile adapter as power source whose output is 5.13vdc.plzz help

    • 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.

    • 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.

  53. 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.

    • 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.

    • Chara, I have tested it using flexible wire coils, but not with PCB yet, but I am sure it will work in this mode too, if optimized correctly.

    • 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.

    • 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..

  54. 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

    • Thanks Michael, It looks like a typo in the article, it should be 1 amp actually, or may be 2 amps….not more than that.

      I'll correct the mistake soon.

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