I believe you have misunderstood the engine in question, it has no breaker
points, no distributer, it's a small 2 stroke single cylinder engine. Please
correct me if I'm wrong. TTYL

> -----Original Message-----
> From: pic microcontroller discussion list
> [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Douglas Butler
> Sent: Thursday, August 09, 2001 16:16
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: [PIC]: Building a Servo
>
>
> I think you misunderstand how a spark coil works.
>
> The spark coil has three terminals.  One is ground, one is for the spark
> plug, and the third goes to the breaker points.  When the points close
> the coil builds up energy in its magnetic field.  When the points
> suddenly open the energy from the magnetic field causes a pulse of high
> voltage at the spark plug terminal.
>
> The terminal for the points has low voltage, maybe 100V max.  That lead
> you can run to a relay.  If you have a megneto you can simply short the
> points to kill the engine.  If you have an automotive type system
> powered from a battery I would put the relay in series with the points
> in which case opening the relay kills the engine.
>
> Sherpa Doug
>
> > -----Original Message-----
> > From: Herbert Graf [mailto:mailinglist@FARCITE.NET]
> > Sent: Thursday, August 09, 2001 4:16 PM
> > To: PICLIST@MITVMA.MIT.EDU
> > Subject: Re: [PIC]: Building a Servo
> >
> >
> > > -----Original Message-----
> > > From: pic microcontroller discussion list
> > > [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Douglas Butler
> > > Sent: Thursday, August 09, 2001 15:50
> > > To: PICLIST@MITVMA.MIT.EDU
> > > Subject: Re: [PIC]: Building a Servo
> > >
> > >
> > > >         I might also add a redundant kill switch with a
> > > > second transmitter and
> > > > receiver, the only problem, and this is something I was
> > > > planning to ask, is
> > > > how do you stop a gas engine remotely? I thought about
> > > > disconnecting the
> > > > spark plug but how would I do that considering the
> > voltages involved?
> > > > Cutting the fuel flow is a second idea but my experience with
> > > > two stroke
> > > > engines is that they keep running, without any fuel flow for
> > > > at least 30
> > > > seconds, long enough to cause damage. Anybody have a better
> > > > idea? Thanks,
> > >
> > > How about some relay contacts across the breaker points for
> > the ignition
> > > coil, assuming you have mechanical points vs. electronic
> > ignition?  The
> > > voltages there are reasonable and without spark the engine
> > should stop
> > > quickly.
> >
> >         I was thinking about something like that but it may
> > be hard to find a relay
> > that can do it. The problem is that if the relay contacts
> > aren't far enough
> > apart a spark will simply develop across the relay contacts
> > AND the plug!
> > :( The motor I am using (and no I can't change the kind of
> > motor being used!
> > :) )uses a "coil flying by a magnet really quickly" approach
> > to develop the
> > spark.
> >
> > Why I don't really like this idea either is that assuming I
> > find a relay
> > with contacts far enough apart it is still possible that on
> > say a humid day
> > the spark WOULD jump across the contacts. I guess I could
> > heavily modify a
> > relay so the contacts are say 1cm apart, I believe that would
> > be enough, but
> > being a safety device I'd rather go with something a little
> > more "sure". :)
> > TTYL
> >
> > --
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> >
> >
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