Minor details on coil design and operation

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Original poster: Davetracer@xxxxxxx 



   I have a few relatively minor questions ...

(1a) Should the safety gap on top of the neon sign transformer be as 
physically _sharp_ as possible (for example, two nails pointing at one 
another), to help ionization and zapping across, or should it be a Jacob's 
ladder shape (gentle curve), or even moreso, smooth curves, something like 
doorknobs?

   The reason I ask is that it seems to me in this application you'd want 
the safety gap to fire sooner, not later, and I believe that sharp 
electrodes will do that a bit faster. On the other hand a smooth shape may 
give wanted capacitance. I don't know, so I'm asking.

   (1b) Also, is it necessary to run two safety gaps, each "side" of the 
NST to case ground?

   (1c) Should the case of the NST be grounded, and if so, to what? Earth 
or wall-socket ground?

(2) Something I have always wondered. I've run a wire to earth ground. As 
it nears the coil, a corona appears from it and will jump to the coil / 
toroid if I give it a chance.

    I had always thought that earth ground was a nice electrical sinkhole 
except in rare situations, like a lightning strike, or possibly the Denver 
Broncos going to a SuperBowl. Anyway, could someone explain how this is 
happening? Is it just a closed circuit going 'round the secondary?

(3) I'm going to attempt to take some pictures of the coil's output on my 
scope and post them, and ask if they look correct. This may take a little 
doing, but any comments are appreciated!

(4) Can anyone tell me what sort of prices NST's are going for in Denver, 
if they are available at all? Last time I looked was right after the ban on 
big signs, so there were things like 15/60's available, but nowadays, I 
have no idea. I'd appreciate any feedback.

    Thank you,

    Dave Small