Can this wireless charger somehow be workable?

Thread Starter

testuserabcdef

Joined Jul 12, 2016
127
I was following this webpage:

http://www.homemade-circuits.com/2015/09/wireless-cellphone-charger-circuit.html

and it pointed me to this circuit:



So then I decided to wire it up with 6VDC instead of 3 because that's what I had.
For the resistor, I tried 330 ohms and then 1K.
In both tests, each 2n2222A transistor burned up.
For L1, I used two separate 10uH inductors with a leg from each one connected together.
For L2, I just used 10uH.
I used the DF04M chip in place of the 4 diodes and 2.2uF for capacitor.

Is there a way this circuit can be improved with using minimal parts to create a
better wireless charger?

I want to eventually charge up two 3.6V phone batteries.
 

ronv

Joined Nov 12, 2008
3,770
So basically I need to make a super high-gain oscillator and replace the speaker with a tank circuit?
To build a good one you will probably need a scope. Do you have one?
The trick is the resonant circuits that optimize it for the frequency of operation.
If I were going to do it I think I would build an oscillator out of a simple 555 ic. Then vary it's frequency until the transmit coil was in resonance.
Then I would buy a receiver coil like this one:
http://www.mouser.com/ds/2/427/iwas3827-268728.pdf
Then tune the receiver for maximum.
 

Thread Starter

testuserabcdef

Joined Jul 12, 2016
127
I will admit I use small coils. I also did build a 555 circuit like you mentioned with an LM386 op-amp added. I tested with an 8 ohm 4.5W speaker and the audio is correct. I then replaced the speaker with a tank circuit and on the receiving side, I used the same tank circuit but my voltmeter reports no voltage when I measured the coil. I tried both 10uH and 0.3uH coils. Right now the oscillating frequency is about 10hz. Maybe I should up it. but to what?
 

Thread Starter

testuserabcdef

Joined Jul 12, 2016
127
But I want to invent a wireless charger to bind into another circuit to eliminate the need to constantly plug in/remove a wall adapter and/or replace batteries when better power is required
 

RichardO

Joined May 4, 2013
2,270
I will admit I use small coils. I also did build a 555 circuit like you mentioned with an LM386 op-amp added. I tested with an 8 ohm 4.5W speaker and the audio is correct. I then replaced the speaker with a tank circuit and on the receiving side, I used the same tank circuit but my voltmeter reports no voltage when I measured the coil. I tried both 10uH and 0.3uH coils. Right now the oscillating frequency is about 10hz. Maybe I should up it. but to what?
The Vishay coil linked to in post #5 is about 10uH and is specified to run at 200KHz. I doubt that the LM386 will work very well at 200 KHz. Maybe a MOS-FET gate driver would work.
 

Reloadron

Joined Jan 15, 2015
7,580
But I want to invent a wireless charger to bind into another circuit to eliminate the need to constantly plug in/remove a wall adapter and/or replace batteries when better power is required
You are a little late with the "invent" part. However, the guy you want to talk to about this would be Nikola Tesla. Unfortunately you are a little late for that also.

You are still going to need a wall adapter of some sort to act as a transmitter and the battery powered device needs some form of receiver. The wall adapter is not going away. There are already wireless charging pads and in the case of my phone for example it matters not. The phone (or any other battery powered device) needs to be placed on the pad. I can just as easily plug my phone into any 5 volt USB source.

Ron
 

Thread Starter

testuserabcdef

Joined Jul 12, 2016
127
You are a little late with the "invent" part. However, the guy you want to talk to about this would be Nikola Tesla. Unfortunately you are a little late for that also.
I know that but I have an existing circuit that uses 5VDC in which I don't want to replace the batteries nor hook up an external wall adapter to it to charge it up each time.

You are still going to need a wall adapter of some sort to act as a transmitter and the battery powered device needs some form of receiver. The wall adapter is not going away. There are already wireless charging pads and in the case of my phone for example it matters not.
Ok, then that's what I need to come up with... a wireless charging pad. I mean I can make an oscillator but its the matter of sending power wirelessly and i don't know the optimal frequency to use for the coils for either carrier or oscillator.
 

Reloadron

Joined Jan 15, 2015
7,580
OK, chargers like this are known as "inductive charging circuits". Earlier I mentioned my electric toothbrush uses one. They are popular for bathroom and kitchen locations because they are easily made intrinsically safe. The downside or disadvantage to these circuits is the inductive coupling is air, this limits the current we can easily get. With this in mind a Google of "inductive charging circuit" will bring up plenty of circuits ranging from simple to more complex oscillator circuits. Another good suggestion is a Google of "electric toothbrush charger circuits".

When all things are considered many of the circuits for inductive charging use hand wound coils which are not to difficult to make. Anyway, the earlier posted circuit or any of the ones which come up on Google should work. Each has their good and bad points. Inductive charging circuit is what you want, just be aware of their limitations and why they have limitations.

Ron
 

ronv

Joined Nov 12, 2008
3,770

tcmtech

Joined Nov 4, 2013
2,867
Unfortunately you are just now taking the first step on what is honestly a very very long and rough road of learning toward your end goal.

There are people with decades of applied electronics knowledge and experience would have trouble making a workable wireless power transfer system. :oops:

The first thing to start studying is Radio Frequency LC tank (inductor Capacitor type) system design and how they work together for both transmitting a signal of any kind and how to pick one up as well.

This alone should keep your head spinning for weeks. https://www.google.com/search?q=rf+...0j69i57j0l4.7939j0j7&sourceid=chrome&ie=UTF-8 :eek:

So yes it can be done and I have done it but its complicated and to do anything well you need to be able either build very well matched transmitter receiver circuits or have the capacity to just throw raw power at things and take what sticks.
Years ago I dug into it and did it with about half of each largely using Tesla's designs ( multi hundred watt HV spark gap driven transmitter) with some modern day updated system components on the receiver side and it still took a long time to get working sort of well. (~10 watts at ~ 15 - 20 feet.)
 
Last edited:

Reloadron

Joined Jan 15, 2015
7,580
The circuit should work as drawn. I don't see an output diode as drawn but there are a pair of 1N4148 low power signal diodes which allow the 555 oscillator to generate a symmetrical square wave. They are required.

The 2N2222 transistor is introduced to make sure that while adjusting the resonance, the 2N3055 is never subjected to an over current situation. In case this tends to happen the over current develops an equivalent amount of triggering across Rx sufficient to activate the 2N2222, which in turn shorts the 2N3055 base to ground inhibiting it from conducting any further and thus preventing the device from a possible damage.

Rx may be calculated using the following formula:

Rx = 0.6/Max current Limit of the transistor (or the wireless power transfer)

Adding a voltage regulator for charging the battery:

In the above diagram, the output from the receiver should be attached with a voltage regulator circuit such as using an LM338 circuit or an opamp controller circuit for making sure that the output can be safely fed to the intended battery for charging it.
The 2N2222 is a low power switching transistor and the 2N3055 is a power transistor. They are both required as drawn. The 2N3055 is what drives the transmit coil. Both coils are the same and coils just like them show up in the links I posted.

The merit to higher frequencies for the oscillator is you can get more power, much like to keep things light in aircraft they use 400 Hz AC systems rather than 50 or 60 Hz. We are inductive coupling and that is why we have two (transmit and receive) LC (L Inductive C Capacitive) circuits.
When an inductor or capacitor are placed in series or parallel they will have a resonant frequency which is determined by the design equation below. LC resonant circuits are useful as notch filters or band pass filters. The are also found in oscillator circuits. 2*pi*F= 1/sqrt(L*C)
Anyway, for the circuit to function it needs all the parts. I can't say how well this specific circuit will work as I never built it. It should work is about all I can say. Note that the AC out from the receiver needs rectified and should be run through a VR (Voltage Regulator) not shown in the drawings.

Ron
 

Thread Starter

testuserabcdef

Joined Jul 12, 2016
127
Ok I'm going to work with the latest circuit I posted since someone says its workable. Now I'll just have to play with it a bit.
The closest thing I have to a 2N3055 is a TIP31 but looking at datasheets suggest that the maximum specs (voltage/current) of TIP31 are lower than 2N3055.
I might as well hit ebay (again).
 

tcmtech

Joined Nov 4, 2013
2,867
Why does something about the deep end of the pool come to mind?
Kinda like scuba diving in the deep end of the pool. Even those who can swim there don't all get to the bottom and play with the really deep stuff to any degree. :oops:

I am pretty sure I could replicate and likely improve on what I was playing around with 10+ years ago given I have greatly improved my tools and related fabrication skills and resources for making the coils and other specially components but I still have serious doubts that I could do it easily or quickly even knowing what I was actually aiming at. :(
 
Last edited:

Reloadron

Joined Jan 15, 2015
7,580
Ok I'm going to work with the latest circuit I posted since someone says its workable. Now I'll just have to play with it a bit.
The closest thing I have to a 2N3055 is a TIP31 but looking at datasheets suggest that the maximum specs (voltage/current) of TIP31 are lower than 2N3055.
I might as well hit ebay (again).
The 2N3055 is a very, very common and old power transistor. The 2N2222 is another very common transistor. Both have been around for many decades. You should have no problem finding any of the parts in the last drawing.

Ron
 
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