Spark Gap Coil Modification

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Spark Gap Coil Modification

Postby Burdman111 » Wed Sep 24, 2014 1:17 pm

I recently joined the physics club at my university. I was pleasantly surprised to learn that they have a tesla coil built already, but it was in need of modifications (non-ventilated spark gap collects ionized gas way too fast). I figured while we're replacing the spark gap, we might as well make it a solid state coil, which would require swapping out the transformer as well (it maxes out at 60hz).

I was shot down pretty immediately for suggesting we do this. It seems that nobody in the club really has much of a clue about how the thing works except for one guy, who insists that it would be too much work to modify the coil we have into a solid state coil, and that we're probably just going to built a second (smaller) solid state coil and just go with the spark gap replacement on the one we have.

I don't have the voltage of the coil on hand at the moment, but its a big coil. At least four feet. I just want to know if this guy is right, and that modifying it would be too hard, or if theres something else going on. I'm not super well versed in the differences between the two designs (other than knowing we'd need a better transformer and a pair of transistor where the spark gap is) so I don't know if rewiring/replacing components would be that difficult or if this other guy in the club doesn't know what he's talking about either.

Anyone have any advice?
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Re: Spark Gap Coil Modification

Postby Frost273 » Sat Sep 27, 2014 8:04 am

IMHO that guy is right.
You may end up with a single non-working coil after modifications are made.
Better leave it as it is and build a smaller solid state one for training.

SGTC and SSTC don't really have much in common, except secondary and primary coils.
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Re: Spark Gap Coil Modification

Postby Alex » Sat Sep 27, 2014 3:54 pm

Designing a solid state coil is much more work than a spark gap coil. It's also a lot more money!

You should replace the spark gap on the coil you have so it still works instead of experimenting and trying to convert it to solid state.
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Re: Spark Gap Coil Modification

Postby Burdman111 » Sat Sep 27, 2014 10:26 pm

Thanks for the responses. I found them very useful.

The coil has an output power of around 200,000 volts I've found out. I just thought that might be important.
Other than swapping out the transformer and placing a new circuit where the spark gap is, what other modifications would have to be made. This guy is convinced the whole thing would have to be rewired and all the capacitors would need to be replaced. I don't think thats right. I think the capacitors (and their wiring) are fine. Could the transistor assembly be made on a permaboard and then wired in to where the spark gap is, or would more modifications have to be made? I have no problem experimenting with a solid state coil on a smaller assembly, but I think that this one would make a better solid state coil than spark gap. On that note, the guy also says that the ratio of primary to secondary coil windings is different in a solid state coil than a spark gap. Is this correct?

Thanks for your help guys.
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Re: Spark Gap Coil Modification

Postby Alex » Sun Sep 28, 2014 7:56 pm

The two systems can share the same resonator setup, though solid state can be a little bit more particular about its specs. What are the specs for the coil you have now? Solid state coils have a lower voltage rated primary.

depending on the size of your coil you won't be able to get away with a perfboard assembly. Transitors cost anywhere between $7 to $250. You also need driver circuitry for the transistors, which would usually be a UD by Steve Ward.

You can see my coil at http://www.personal.psu.edu/ahy5028/DRSSTC3.htm
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