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Hello there! The coupling coeficient k doesn't effect the value of the inductor & capacitor (at least to first order). The value "k" gets smaller as the coils get farther apart. If you want to know the equation for the inductor and capacitor, you can read about it on this website:https://www.allaboutcircuits.com/textbook/alternat...You can always tune the values for different resonant frequencies.
Don't worry, we've already started a Makerspace! :)
Nope, unfortunately, this project won't help you with that problem!
Yes, cell phones work great as signal generators for applications like this, where harmonic distortion doesn't matter. It's great to have easy access to a signal generator!
This will not interfere with surrounding circuitry. The magnetic field intensity levels at any one location are very low. We did optimize the frequency for a couple different reasons. First, the higher the frequency, the small the capacitor, since we needed a 500V capacitor, we needed a high enough frequency to get the capacitor less than 1uF (8kHz does the trick). Second, we needed the frequency to be low enough that even cheap computer speakers would work. If, for example, we had chosen 15kHz, then we'd need a very high end audio power amp to drive it. So 8kHz is a good comprimise!
This project isn't exactly 1/r^2 loss, that is for an electromagnetic plane traveling wave radiating into a volumetric space from a monopole. This uses magnetostatic fields (which basically just means that there are only magnetic fields involved in the transmission, whereas traveling radio waves involve both magnetic and electric fields). The transmission curves fall off exponentially with distance. The math is a bit complex, since the two coils are interacting with each other, and you have to include the mutual inductance and resonant circuits. But the transmission curves are a good match for an exponential curve. In fact, if you want the exact values, here's the emperical curve fit:Voltage Out/Voltage In = 0.596e^(-0.147*distance)
Good point, we fixed that, should have been cm, not mm!!
High-Range Wireless Power View Instructable »