Re: Triggered gap and safety gaps

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

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