I'm trying to make this wireless charger for one of my school classes, and I don't know much about these circuits. So naturally I went to youtube and I found this link

on how to make one. A lot of things in this video seemed rather sketchy. Could someone just look at what he did and tell me if theoretically it would work? I already made the tx circuit but I just need I still need a capacitor for the rx circuit. I'm also just wondering whether when I finish it and it doesn't work it'll be because human error or someone trying to get youtube views. Thank You!!

 

Well... theoretically you will get something out...

But not much...

Prepare for disappointment.

 

Hi,

I can comment generally which would apply to most wireless chargers.

First, the transmit coil generates a magnetic field that is changing. The change can vary but the most efficient will be a sinusoidal wave. The shape of the coil is also a factor which i'll get to also.

Second, the receive coil should be as close to the first coil as possible as distance is a really big factor because the signal drops off fast as the distance increases.

Third, the whole thing is closely related and dependent on mutual inductance, and there is a coil shape that has maximum mutual inductance. That means the transmit and recieve coil would be the same size and shape. Unfortunately i dont remember what this shape was but it's on the web somewhere, but if you cant find it ill try to look it up.

Fourth, since the magnetic field intensity increases with current, the higher the current the stronger the field that gets 'transmitted' to the receive coil and hence the most current in the receiver. So it's not as much the voltage as the current. The catch is that with a certain coil with a certain resistance you still need voltage in order to get the required current level, and so of course the driver circuit has to have the right voltage and a high enough current. This means for highest efficiency you nave to match the driver impedance to the impedance of the rest of the setup which includes the primary coil, secondary coil, and charge circuit, at a presumed distance of separation. It will be best with that presumed distance but of course you may not get the exact same distance each time unless you set it up mechanically to get that result.
You may or may not be able to match them up effectively if a lot of things can change a lot, even charge current in the receive circuit.

So you can look up the best coil shapes and that should get you started. That means there is a certain cross sectional area shape for both coils relative to the diameter of them. If you cant find this information i'll try to find it in my own notes.