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Old 06-11-2011, 02:34 PM
Farmhand Farmhand is offline
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Join Date: Jun 2010
Location: Australia
Posts: 3,389
Originally Posted by cody View Post
I prefer using AC for these small tests, you get twice the voltage on the primary that way. Even better is AC square wave, that will smack it real good and get an even greater voltage gain on the secondary. Also with AC you can insert a series capacitor with the primary to form a series tank circuit and that will ramp up the voltage on the primary much higher if designed correctly. But your setup seems to be working real good, Im not really familiar with the circuit you are using but it appears it is inputting a higher voltage than the 12V battery you are running with. Have you measured the voltage it outputs to the primary? DC setups in my opinion seem to become advantageous for overcoming the engineering difficulties of getting really high voltage onto the primary at high frequency. For your recovery on the receiver try to hunt down some 1n4148 diodes. You can usually find them in junk electronics, they are very small and glass. I find them to work great for these little setups.
Yes an AC square wave is appealing, but really high frequencies may be easier with DC.

The circuit I put together is basically Tesla's Ignition coil patent drawing modified for the transmitter, the only change is the transformer.

Tesla Ignition coil patent
NIKOLA TESL-A - Google Patents

My circuit. is the generator side of this.

If the cap is sized right the inductor discharges into the cap and charges it to above supply voltage. Then the cap discharges through the primary coil. I am trying to discover the cap inductor values for this primary, I think I am close. I tried measuring the cap it said 11.5 volts, I think this is a current amplifier because the cap is in parallel with the inductor. The energy stored in the inductor gets added to the supply but I'm not sure of the actual mechanics of it I have yet to determine that, but it is very effective.

I drew it for a spiral transmitter, before you guys showed me this one. Which I think is the better design. Especially for no spark gap because at this time I think he was just using abrupt switching as in the quote in the post above. Hence the closer coupling. i think, i need to read more.

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