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# Plans for a Mini 120V Tesla coil ( Science Demo style )

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You guys do realize that if we all come to a conclusion that this device does not fall inline with the definition of a true Tesla coil, every science department and physics demo is going to have think twice about what they call this little unit on display.

I have allot of scrap units kicking around I can cut them open or do any form of measurement needed. Just let me know what you would like.

I also have a 40KV meter as well.

This may help in the mystery, 10,000 to 50,000 V, 500 kHz

So it is converting 60Hz to 500Kz

*Output: Between 20,000 to 45,000 vts, at a frequency of approx. 500 kHz.

*Current output of the spark is about 1 mA.

*This model is a variation of the tesla coil. It has a primary coil which
produces an output voltage of about 1200 V at the input line frequency,
50 or 60 Hz. This output voltage is interrupted by a vibrating contact,
energized by this coil at twice the line frequency. The output voltage of
this primary coil is connected to capacitors, which are then discharged
into a high voltage coil.

*The capacitance, resistance and inductance of this circuit is designed
to oscillate, or ring, at a very high frequency, in this case 500 kHz. The
output of this high voltage coil is adjustable by varying the distance of
the vibrating contacts, which is user adjustable, by means of a knob on
the end of the unit.

*Applications include pinhole leak detection, as in linings of tanks and other
similar metal objects, and in plastic welds, where a test metal backing is
applied. Other applications include ionizing a gas inside a lamp, neon sign,
double-pane insulated windows, pharmaceutical vial, or similar glass vessel
where a deep vacuum is contained."

*Output: Between 20,000 to 45,000 vts, at a frequency of approx. 500 kHz.

*Current output of the spark is about 1 mA.

*This model is a variation of the tesla coil. It has a primary coil which
produces an output voltage of about 1200 V at the input line frequency,
50 or 60 Hz. This output voltage is interrupted by a vibrating contact,
energized by this coil at twice the line frequency. The output voltage of
this primary coil is connected to capacitors, which are then discharged
into a high voltage coil.

*The capacitance, resistance and inductance of this circuit is designed
to oscillate, or ring, at a very high frequency, in this case 500 kHz. The
output of this high voltage coil is adjustable by varying the distance of
the vibrating contacts, which is user adjustable, by means of a knob on
the end of the unit.

*Applications include pinhole leak detection, as in linings of tanks and other
similar metal objects, and in plastic welds, where a test metal backing is
applied. Other applications include ionizing a gas inside a lamp, neon sign,
double-pane insulated windows, pharmaceutical vial, or similar glass vessel
where a deep vacuum is contained."

Thank you very much for that DJ. That is just what I needed to know. It sounds like they took the theory of a tesla coil and combined it with a capacitive discharge coil driver that you might find in an automotive ignition system. Seems like an interesting idea. At least they said in the description that it is a variation of the Tesla coil. However, it is still quite different from what you have. Unless I'm reading the schematic wrong, I don't see an LC circuit that could constitute the high frequency "ring" that makes a tesla coil work. You have the interrupter, but I'll need to look again at the schematic

[EDIT] After looking over your schematic again, it does actually appear to be a circuit very similar to that of a real tesla coil. The only difference seems to be the low voltage input, which of course makes a real spark gap impossible. However, with the circuit interrupter that takes place of the spark gap, the same oscillation appears to occur between the capacitors and primary. I guess I owe you an apology DJ--It does appear to be a real tesla coil after all, at least from my last look. The only real difference is that the voltage input is lower, which would explain the lower output voltage. I imagine if you connected this thing to 480vac 50/60 hz, you'd get a slightly higher output.

Something to consider though--changing the interrupter distance does no better job at adjusting the output as a regular spark gap would in a classical tesla coil. All the real magic happens between the capacitors and the primary. Try changing out the values of the caps a bit and try tapping your primary. I would expect you to get a better output at some point if this thing actually does operate like a regular Tesla coil.

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This thread got me to dig out my Tesla coil literature. The coil in question is ( I think) from some old Lindsay book reprints called a "Oudin coil" it also has a "kicker coil" in it. The "kicker coil" is the iron core coil/vibrator part. In a way this is also like the original Model"T" Ford ignition coils also.

https://www.smokstak.com/articles/buzz_coil.html

This thread got me to dig out my Tesla coil literature. The coil in question is ( I think) from some old Lindsay book reprints called a "Oudin coil" it also has a "kicker coil" in it. The "kicker coil" is the iron core coil/vibrator part. In a way this is also like the original Model"T" Ford ignition coils also.

https://www.smokstak.com/articles/buzz_coil.html

Thanks shortbus. I think you're right. I've seen Oudin coils before, and this one does indeed seem to fit the description. Oudin's coil is, of course, loosely based on Tesla's high voltage coils, but designed for lower voltages using an interrupter.

Wow, I had completely forgotten about the Oudin coils.... Thanks for the links--I think you may have just solved our discussion!

Our large 45,000 Watt coil has a similar top load to a Oudin coil, and ours is over 100 years old now.

Another interesting read, Looks to have the same schematic as well, I have not had time to read through it yet but will post it up and get back to it.

So I did some testing on one this evening, I went from 120V up to 220V using my large power supply I built the output is increased but not dramatically.

I also ran the coil at 120V DC full wave rectified as well as tried it cap filtered or smooth 120V DC and it still worked the same! haha same frequency and everything.

I then tried 240V DC worked for about 3 sec, the small little contact can not break 240V DC just not large enough, so it made an arc welder lol.

I pulled just the vibrator from another coil, I will run this on the scope to see the output I am very curious.