Re: Here comes the SCR based coil

At 06:53 PM 1/11/99 -0700, you wrote:
>Original Poster: "Bill the arcstarter" <arcstarter-at-hotmail-dot-com> 

>Where'd you get the SCR gate trigger transformer? :)
Mine were surplus from a motor drive circuit. I took the core and wound my
own. Some ferrite toroids like line noise filters may work. Just make sure
they don't saturate before you have completely turned the gate on.

Check out http://www.mag-inc-dot-com/  
I couldn't tell you what to get yet but I'm sure they would have it.

>I suppose all coilers need is a supply of primary amp*turns at the 
>appropriate excitation frequency...  
>How fast will your circuit run at this point?  What sort of output do 
>you get?
About 500pps max right now. I have been fighting some problem and learning
the hard way about magnafier output transformers. It has been difacult for
me to design a transformer with high coupling low inductance and a modest
step up ratio. My most succesful transformer so far has been an 8" pipe tape
wound with 180 turns of 4 mill poly and 1/2"x2mill copper tape. The primary
was one turn of a 3" copper strap.  With this setup I could get 8" sparks.
Kind of dissapointing. Some calculations based on the ESR of the resonator
tell me that 180 turns is too many for a good impedence match. I cut back on
the turns to no avail. The transformer by it self could produce 1.5" spark
which tells me there is some loss going on somewhere since with 1KV in I
theoretically could have 180K out. So with a little head scratching I
realized that loading on the secondary will produce loading on the primary
and thus more loss in the parasitics of the circuit. So I think I need to
increase the L in the primary so that the parasitics are less significant. I
also need to tighten up my wiring to minimize the parasitics.
  The problem with increasing the L is that the primary resonant frequency
can get low pretty quick! Especially with 2.5-30uF on the primary. I mean
like 20-40Khz!  I think that is the route I'm going to take. I have like
30lbs of #25 and maybe 10lbs of #14 and #16. I need to come up with a new
resonator (third coil) in this frequency range. At first I was thinking of
using a short squat coil to get a large inductance. Then I realized that
self C is the bane of a maggie although at these frequencies it won't be as
significant. Any thoughts on this are more than welcome.

>Since the current pulse is such a step (as opposed to a sinewave) 
>implies that substantial energy will be at frequencies far away  from 
>the secondary's self-resonant frequency.  I'm not sure there's anything 
>which can be done about that in your design.  This may be the limiting 
>factor in terms of net arc length output!

The BIG ??? diode in my schematic allows ringing. I'll see if I can post a
waveform on my website.

Eddie Burwell