I agree, DRGONZO. It was certainly exciting to see this young man present his project and to see the next generation of engineers at work. I particular appreciated his desire to be innovative by looking for ways to improve the project.
Thanks. The wireless charger and coils I used delivered about 12V, so you could charge almost anything. The current, however, is pretty low, so it takes a long time to charge batteries. If you have any improvements to the power output capability or efficency of the design, I'd love to see them.
Mr. Duffy, it is up to YOU to discover that breakthrough for fast charging. I hope you do; you could be the person who finally gets all-electric vehicles into the mainstream. Nothing we've seen to date has done a good job of this.
I have gotten a slightly more powerful version (as in the video) but the main problem is that the coil's inductive resistence is high enough that no matter how much current I make avaliable, the current used is still usually below a few amps. The secondary coil is just a few miliamps.
Not knowing what knowledge this young man has, as Engineers in the field we need to be careful with what instructions we give him. While outside thinking is indeed necessary for innovation, a firm comprehension of the fundamentals is necessary. That can only be obtained through understanding and asking those with greater knowledge than the questor currently has.
With that said, I think it would help young Mr. Duffy out if others in our field that may have some thoughts on how to improve his charging circuit would share them with him as he may not know where to begin to change and experiment to attempt better charging times. It is another step to outside thinking as well. Learning from others and bouncing ideas off of more knowledgable people. Even if you run into someone who states, "Oh that can be done that way...", it can be turned into a "Because you said it couldn't I need to prove or disprove that to myself first!" philosophy.
Great Job on your first Gadget Freak Mr. Duffy! If you keep at the circuit I am sure you will find the answer. Ask everyone you can for clues, thoughts, and ideas on what might make the battery charge faster! And remember, like TJ says, don't take anyone's answers to heart unless you understand them and know that they apply to your question. While it is up to *you* to learn, others can help as well.
Jason I agree with your sentiment. Not every good idea comes from outside the box and sometimes it is wise to rely on experience. Not all experience results only in total nay saying. Sometimes it saves time. If John is not sure of the validity of the advice, then he should not abandon his plan, but if you are talking to an expert in a field and he can point to numerous failures of a particular method, why not utilize that information?
The efficency of the lantern itself is actually super high. The circuit with a fresh alkaline AA will last about a full week before running out. As for ICs I dont have acess to anything beyond my local radioshack and science surplus store. This gadget can be made from most low-end electronics stores with component parts.
If you want to transfer more power... I suggest that you use two 'horseshoe'
shaped magnetic cores with the open ends facing each other. The best case would be if you could make them touch... but even with a gap it should concentrate the flux much more than your current design.
you might look for ferrite "C" cores, there are other shapes you could use as well.
I don't see a schematic posted... but I'd caution against paralleling transistors unless you have some series resistance (usually in the emitters) or you match them for Vbe (voltage base-emitter) drop so they share current well. If not, one will probably get more current than the rest and fail first (either shorting and killing the circuit quickly, or opening and leaving the rest to run even hotter and fail slowly...)
As for the "horseshoe" cores, I dont know where to get any, and I'm not sure why the schematics werent posted. I sent them in with the build instructions. If you do want to make one, you can find the original article that I wrote on MAKE:projects. (It was written before this one was posted). The transistors actually work okay, as my current unit still runs cold after about 3 months of use. It may not be the "best" way, but it doesn't require any fancy or unusual components.
John, in order to more efficiently transfer power from the primary coil to the secondary coil, you need to have a high permiability core to concentrate the magnetic fields of the two coils. That is why transformers have iron or magnetic cores. I have a Hoemedics toothbrush that uses a dimple in the housing that allows a magnetic core from the charger to closely couple the two transformer coils. The other technique is to use resonance of the two coils by adding parallel capacitors to tune the two coils to the same frequency to allow better power transfer. Good luck with your experiments.
Yes, I had originally intended to use a core, but since the PVC cap is rounded, I cannot fit a core inside the sender coil, and the reciever coil is crowded by the circuit. Thanks for your help anyways.
Very Cool project. I wish had your motivation and drive at fifteen. The internet would have been very helpful too. Recently I discovered an open source program called "Fritzing" where you can graphically assemble a breadboard version of your circuit. Then after some frustration create files to order a PCB or boards.
Thanks for you suggestion of more coils, alzie. I have just tested a new version with a TIP120 in place of the 2n3906's, and about 5 times more turns on the primary. I currently get about 0.02A at 10V out, which is more efficent than before, which was below 0.01A at 12-14V. Once I get a Jameco.com order, I'll try to match the reasonance of the coils for efficency.
Hi John, I'm curious why you didn't identify "a magazine" as Make, where Steve Hoefer's instructional article for the "indestructible LED torch" appeared. At Make, we give credit for things like this.
We remain admirers of Design News.
John absolutely DOES give credit to MAKE in the video. Even identifying the issue number. The editors at DesignNews who did the write up on what the video was about are the ones who failed to give credit by simply stating "a magazine".
So in short, 15 year old John does it right. The professionals who's job it is to get these things right are the ones who screwed up.
Good point, Zenock. The oversight was mine. As a former small magazine publisher, I should be more atuned to giving credit where credit is due. I could blame deadlines for numbing the brain, but really there is no excuse. I'll remember this going forward.
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