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Old 06-11-2011, 11:54 PM
Farmhand Farmhand is offline
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Join Date: Jun 2010
Location: Australia
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Originally Posted by kapierenundkopieren View Post
Hi Guys! I'm interested in replicating the wireless power transmission, but i have no function generator or even a oscilloscope. Right now i'm searching for a variable 4MHz to 10MHz square wave generator schematic that would fit in, or any other oscillator that would work for this project. I was looking here: Square Wave Generator
Does anyone know if this is suitable for such frequencies?
Also, could someone more experienced than me draw a schematic for let's say a 10W or 20W output?
Or can i get any advice about this idea like what transistor to use on the output of the oscillator?

Thx in advance!

Hi Dann, I am waiting for some parts to arrive, I have some SG3525 chips coming that should work well, and will drive a mosfet directly or through a Mosfet driver, they are only capable of 0.4 Mhz though. When they arrive I will be designing a dedicated circuit for this which will have the option of an AC square wave or maybe 2 x 0.4 Mhz of DC pulses alternately which will be 0.8 Mhz I hope. If the chips do not arrive when I am ready, I will use the TL494 chips I have already.

The circuit will be PW and frequency adjustable with alternating pulses which can be utilised for driving a tranformer to make AC for a resonant Tank with the primary or the pulses summed to drive a DC resonant Tank for the primary.

I am hoping I can get the current sensing to work, to control the PW dynamically, if it is applicable.

I would prefer to use as simple a circuit as possible like the one I am using now. But simple has it's limits. So my goal is simplicity and effectiveness.

The transistor switch I am using is only rated to 100v it's a IRF540N but it is Neon protected which limits the switch voltage to about 80 volts. The circuit itself is only rated to 18 volts input but the coil can be supplied with up to 50 volts. The SG3525 chips can take 40 volts directly, as can the TL494.

As Cody said though the driving circuit can be anything really, the important thing is to wind the two transmitter/receivers well and this is the difficult part. Winding the coils require's patience and forethought so as not to end up with a big bunch of tangled wire. Some bee's wax is very usefull to make the winding surface tacky and to hold the windings for a rest. I wind all my coils by hand. I only made the surface tacky with wax for the first inch or so of the HV resonator coil former, when the first inch or so is wound the rest is easy to deal with. Make sure if you use wax that there are no big lumps or bumps just a thin smear, too much and it will end up on the outside of the coil and it won't be shiny and pretty.

I can provide the dimentions I wound mine to and the coil heights and stuff if needed but these things are never really final untill the last.

I have a feeling that big tall resonator coils "B" are not really necessary if the required capacitance could be acheived to lower the resonant frequency to below 500Khz. The peak voltage at my receiver output is about 5 to 6 x the input voltage. With bigger resonators it would be more. The higher the voltage the more reduction is needed at the receiver, but higher voltage will run different stuff. It is all relative to our needs or wants I think.

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