Re: Terry's DRSSTC - The Bridge...

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Original poster: Steve Ward <steve.ward@xxxxxxxxx>

> Just the 120VAC with ~~40 amp pulses charging the buss caps.  It would be
> cool if some triac or other simple circuit could control the voltage here
> and eliminate the variac.  I think you could control off either voltage or
> limit the current pulses.  Maybe it could even do the "soft start" for the
> buss caps...  Although this is the last of my concerns at the moment, it
> will certainly be something to look into once the thing is
> working.!  Getting rid of the variac is one thing almost begging to be 
done!!
>
> Cheers,
>
>         Terry

Terry,

My latest DRSSTC (the very tiny one) does not use a variac to control
power.  Basically my controller can vary pulse width down to basicaly
1uS or so, which is only enough for 1 RF cycle at most.  While its not
absolute zero output, it does only make about 1/16" sparks.  Anyway, i
just use a soft start (switch in a resistor on the AC line) to charge
the filter caps, then i switch out the resistor and its ready to play.
 I then control power and BPS from my little box made from an old
coffee can :-)  No variac needed.

There is no reason your TRIAC circuit would not work.  Steve Conner
built a similar power supply for his OLTC-2, no variacs there either.
But i think from my point of view... these things are unreliable
enough as is!  No need to have a questionably designed power supply
too! ;-).  Though actually, im sure it could be done very easily, but
my variac box isnt too big of a hassle to carry around, it only weighs
about 10lbs.  Though i figured i would try something new on my little
coil (thanks for the idea Jimmy).

I also did a few power measurements on the little coil.  It struck 10"
with the kill-a-watt reading 35W :-).  It took around 120W to get 14"
(just to prove that *my* coil can beat all the coils in Gary's mini
coil competition ;-) ).  Interestingly, it took a whole 200W to get
15". Note that these power levels were recorded at 120BPS at least. It
seems obvious that efficiency is really dropping off as the ON time
increases for each pulse.  What i find is that my primary (made from
wire that is WAY too small) gets very hot, quite quickly at these
higher powers.  I think that the primary may just be eating up the
extra power... its about time i make a new primary from some 12awg or
something.  I will let you know how it goes.  Sorry to get off topic
here, but im sure you might find that interesting.

Seeya,

Steve