> -----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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