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After learning that some devices can be charged up wirelessly through inductive means (which https://powerbyproxi.com/wireless-charging/ illustrates), I want to try to invent a simple one myself, but I have a few questions.

  1. For the charger circuit, could I get away with creating a simple one-transistor transmitter? If so, what frequency will I need to set it at and why? and will I always get better results if I use high-value inductors?

  2. I assume for the receiver circuit (circuit to be charged) that the frequency must match, but should the inductance also match or be different?

  3. How is it possible that such technology works if a dead battery powers the receiver? does one have to solely rely on crystal radio technology and have the transmitter almost sandwiched next to the receiver?

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closed as too broad by laptop2d, uint128_t, Daniel Grillo, CL., Dmitry Grigoryev Jan 9 '17 at 17:50

Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

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    \$\begingroup\$ You've asked over 70 questions yet you have only formally accepted about ten and if you want more people to help you, you should consider playing the game and rewarding folk for good answers. If in all of those 60+ questions you have raised you can't understand the answer, then ask why. \$\endgroup\$ – Andy aka Jan 3 '17 at 18:19
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It's not worth inventing your own. You want to look at Qi (pronounced "Chee") wireless charging, which has a standard protocol. Charging not only involves power transfer between the transmitter and receiver, but also a wireless communication back and forth between the two.

I recently successfully designed wireless charging into a product using a bq51050B High-Efficiency Qi Wireless Power Receiver and Battery Charger which is available on Digi-Key for $4.32 in single quantities. It is designed to charge batteries like a 3.7v Li-Poly that are used in cell phones.

The only gotcha is that it is available in only VQFN and BGA packages, which are not very hobbyist friendly. There are breakout boards, like this one, which will convert from a QFN-20 to a DIP layout, bit it costs twice as much as the chip!

The advantage to using a standard receiver chip is that you don't need to build a transmitter; they are available fairly cheaply from places like Amazon. I used this one, which costs $13.

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