Blowing dimmers in triggers, gap behavior

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "jpeakall by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jpeakall-at-mcn-dot-org>

Howdy All,

Blew my 700 watt dimmer. Same as the last one, small wire inside crisped, no
other damage. I could fix it. However, when it blows, it seems hard on the
system i.e.. safeties fire like crazy and so on. A 1000 watt dimmer gets
pricey, and I bet I can blow one of them too. Any alternatives to the
dimmer? Even something non-adjustable? Or what about a variac, I have a
little 4.5amp.

Initially I was having trouble adjusting the gap so that the trigger could
start the arcs, but the NST couldn't start arcing unaided. The tolerances
were very close, and I couldn't get it adjusted to fire reliably. I decided
that my ordinary IC wasn't arcing far enough, so I went and got a HEIC. Now
my problem is that the trigger arc jumps my safeties, and initiates an arc
there. Stopped messing with it, as the cold medicine I was taking was
making me dopey. I found myself reaching for a hot wire. HV and cold
medicine don't
mix!

Thanks,

Jonathan Peakall


----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Wednesday, August 01, 2001 6:08 AM
Subject: Re: Triggered gap and safety gaps


> Original poster: "Bert Hickman by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<bert.hickman-at-aquila-dot-net>
>
> Richard and all,
>
> I don't think that kickbacks will be a problem as long as you use
> relatively small (500 pF) doorknob caps in series with the trigger and
> return to the trigger coil to serve as blocking caps. The worst case
> kickback that can couple back into the secondary side of the trigger
> circuit will be of the order of .05 Joules since it will be "limited" by
> the charging of the doorknob caps. A failure of a blocking cap could cause
> the tank circuit to back up into the secondary of the trigger coil, but as
> long as the "low" end of the coil was grounded, even this should not
create
> a significant problem - the turns ratio of the trigger coil will reduce
the
> amplitude on the primary side as Richard indicates. Safer trigger phase
> adjustment "on the fly" can be done by simply making a suitable extension
> of the plastic knob from a drilled out plastic rod or even a chunk of heat
> shrink tubing slipped over the knob of the pot of the dimmer. Finally,
> using MOV's on the mains side to ground should suppress any abnormal
> nasties from getting back into the mains...
>
> Best regards,
>
> -- Bert --
> --
> Bert Hickman
> Stoneridge Engineering
> Email:    bert.hickman-at-aquila-dot-net
> Web Site: http://www.teslamania-dot-com
>
> Tesla list wrote:
> >
> > Original poster: "Richard Wayne Wall by way of Terry Fritz
> <twftesla-at-qwest-dot-net>" <rwall-at-ix-dot-netcom-dot-com>
> >
> > I think Dave Sharpe's optical isolator scheme will be ultimately the
safest
> > solution not only for the triggered gaps, but also for a wide variety of
> other
> > future variables we may eventually wish to change on TCs "on the fly".
I
> look
> > forward to his input.
> >
> > Having said all that, I have a few observations.  Since an automobile
spark
> > coil is simply an auto transformer, if there was to be a 5-10 J HV kick
> back of
> > say 12 KV pulse, then the voltage differential across the two inputs
> should be
> > way lower.  Maybe  ~120 volt pulse which is presented to the triac --
just by
> > transformer action of the auto transformer.  (These numbers are not
accurate
> > and are for illustration only.)  If the grounded terminal is connected
> closest
> > to the HV winding on the auto transformer, the HV pulse would be most
likely
> > shunted to ground.  Also 140 volt MOV's could be place on he low voltage
side
> > before and after the triac.
> >
> > Any thoughts?  Bert, Jim, Terry, list?
> >
> > RWW
> > >
> > >
> > >
> > > Original poster: "David Sharpe by way of Terry Fritz
> > > <<mailto:twftesla-at-qwest-dot-net>twftesla-at-qwest-dot-net>"
> > > <<mailto:sccr4us-at-erols-dot-com>sccr4us-at-erols-dot-com>
> > >
> > > Terry, Ted, ALL
> > >
> > > I think in lieu of the following posting, that the SCR - Variac
controller
> > > I was
> > > posting a while back should be made available as a triggered gap
> controller.
> > > The advantage is the unit can be optically isolated.  I much prefer
that
> > > approach
> > > to turning a knob that might have a 5-10J impulse coming back into the
> > > ignition coil.  Bert Hickman posted awhile back about using a 500 pf
> > > (there-about)
> > > 30-50kV cap between trigger electrode and ignition coil to isolate
from
> main
> > > gap pulse.  The control circuit would be nothing more then a variable
> > > illumination
> > > on a CdS photo resistive element is series with back to back SCR's.
> > > Isolation
> > > could be accomplished with a fiber optic at that rate.  Ted's comment
> is well
> > > founded, we should avoid adjusting running coils, especially on the HV
side
> > > while the system is running.  One mistake could be someone's last.
Let me
> > > make several corrections, and I'll post the EDN circuit via Terry.
> > >
> > > Regards
> > > Dave Sharpe, TCBOR
> > > Chesterfield, VA. USA
> > >
> > > Tesla list wrote:
> > >
> > > > Original poster: "Ted Rosenberg by way of Terry Fritz
> > > <<mailto:twftesla-at-qwest-dot-net>twftesla-at-qwest-dot-net>"
> > > >
> > > > Mike:
> > > > I am close to the point of setting one up. Waiting on a part from
> McMaster.
> > > > I plan to have the dimmer in a standard AC box and connected by a
> line cord
> > > > to the cap and ignition coil (a remote config). However, I can
assure you
> > > of
> > > > one thing: I will NOT attempt any adjustment of the dimmer/T-Gap
while
> > > > anything is powered. Period. Ain't worth it!
> > > >
> > > > Safety First...Really!
> > > >
> > > > Ted
> > > >
> > > > Subject: Re: Triggered gap and safety gaps
> > > >
> > > > Original poster: "by way of Terry Fritz
> > > <<mailto:twftesla-at-qwest-dot-net>twftesla-at-qwest-dot-net>"
> > > > <<mailto:CHURCHMON-at-aol-dot-com>CHURCHMON-at-aol-dot-com>
> > > >
> > > > Hi Johnathon and list ,
> > > > I too am concerned that if I build one of these triggered gaps that
I
> could
> > > > get back
> > > > lash from the tank circuit if I come in contact with the dimmer
knob.
> > > > Has any one else experienced any from these type of trigger circuits
?
> > > >
> > > > Thanks ,
> > > > Mike Church(CHURCHMON)-at-aol
> > >
> > >
> > >
> >
> >
> > --- Richard Wayne Wall
> > --- <mailto:rwall-at-ix-dot-netcom-dot-com>rwall-at-ix-dot-netcom-dot-com
> >
> >
>
>
>
>
>