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Wireless energy experiment

PostPosted: Wed Mar 12, 2014 12:10 am
by volta86
I am trying to gather the wireless energy from the tesla coil as much as possible to do something interesting. Today I did my first experiment. I connected an inductor, capacitor, resistor and LED in series and placed it near the coil. The LED lights up very bright as I increase Tesla coil power. It does not burn out. The arc does not strike it. There is absolutely no physical connection to the LED circuit. All the current is induced wirelessly.

I originally tried to make the LED circuit have the same resonant frequency as the coil, approximately 250khz, but I miscalculated and ended up with a resonant frequency of 61kHz. Ideally to collect as much energy as possible my LED circuit should be at the same resonant frequency as the tesla coil, and I will fix that later.

But anyway. I need a little advice on the results I got. I want to calculate the power across the resistor in my LED circuit. Here are the component values. R = 33ohms. L = 560uH. C = .47uF

Below is a scope screnshot of the induced voltage across the 33ohm resistor.

The scope is set to 10V/div AC. Its about 30 Vpp at the maximum of the decaying sinusoid.

The screenshot below shows the frequency measurement with the cursors.

This gives a resonant frequency of about 284khz.

The screenshot below shows the red LED wirelessly lit. Its pretty bright. Thats not even full power.


Here is a picture of my setup. The inductor is close to the tesla coil, and is collecting most of the wireless energy.I wonder if its getting energy from the primary instead of the secondary. Ideally the inductor should be above the tesla coil I think to get maximum energy. Link to picture is below.

So anyway my question is: What is the power going through the 33ohm resistor? I'm getting 30 Vpp. 15V peak. The RMS is 10V. The power then is 3 watts. The current is 300mA RMS. This is the series current going through the LED. Why has the LED not burned out? I realize its a decaying sinusoid at 285khz, but if you take the true RMS value of the signal somehow it seems to me that the current is still higher than 30mA (common max current of LED).

I think I need to get the true RMS value of the voltage to find out the true power in the resistor. Maybe I should try that with a different scope or multimeter

Re: Wireless energy experiment

PostPosted: Wed Mar 12, 2014 8:09 am
by volta86
To be clear, the picture below shows my setup. As I said I'm measuring the voltage waveform shown earlier across the 33ohm resistor with oscilloscope probes. Link to picture below.

Re: Wireless energy experiment

PostPosted: Thu Mar 13, 2014 12:46 pm
by Frost273
Hi. I don't really know if the light is going to be brightest on the resonant frequency.

I would like to experiment myself too.
I'm going to be guided by the following projects.

Wireless powered LEDs
One may notice single charging capacitor after rectifying diode.

Wireless Energy Demonstration Kit

The last one seems to be proprietary. But from the pictures the idea can be received:
one coil -> rectifying bridge -> 2x 5,1Ohm resistors and 6 in series LEDs + Zener diode.

Nice drawing by the way ;)

Re: Wireless energy experiment

PostPosted: Fri Mar 14, 2014 3:27 pm
by volta86
Thank you for those links. :D And yea. Nobody said engineers have good artistic skills. Thats what my architect friend "Mr Arteeest hipster" is for.

Re: Wireless energy experiment

PostPosted: Sun Mar 16, 2014 8:27 pm
by E.TexasTesla
An LED held in your hand by one lead will light up near the coil.
Polarity doesn't matter. Your calculation for current and voltage accross the LED would need to factor in RF.