# Re: Top Toroid

```In a message dated 97-02-05 03:38:52 EST, you write:

<< John and all

- snip-

I use only neons. The charge current is absolutely limited by the neon
to either 60 or 120ma(depends on neon being used). It would be
interesting if someone out there can calculate the time it actually
takes to charge a cap from a current limited neon. I have been unable to
come up with a formula which satisfies me. The formula would have to
assume a rated neon voltage and current and incorporate those parameters
in a formula which includes the cap value. With the timing determined ,
it would be easy to determine if multiple firings are even possible.

By the way , in some testing I have done, it appears that the neon will
put out its max current only when the input voltage is at maximum. At
say 60 volts input you can only get 30 ma from a 60ma neon. This must be
taken into account in any formula and has been a stumbling point for me.

Help anyone!!!!

Skip
>>
Skip,

It takes 5 time constants (if I remember correctly) to get to full charge.  I
don't remember the specs on your system.  My new 3" coil uses two 3,000 ohm
series resistors to help protect the 15 kv, 30 ma transformer.  Using 6,000
ohms and .0047 mfd, one TC = 2.82 x 10 -5 seconds.  5 TC = .14 ms.  One half
cycle is 8.3 ms.

For a current limited transformer, I think we really need to use the
effective impedance of the transformer for R.  In this case it would be
500,000 ohms.  So one TC = 2.3 ms and 5 TC = 11.75 ms.  If one half cycle at
60 cycles is 8.3 ms, then my cap will never get fully charged.  I think I am
misssing something here.

Fr. McGahee, what's the deal here?

Ed Sonderman
```