Since it is for a kill switch:

Imagine a grounded spring steel strip held away from the top of the spark
plug by an electromagnet.

Signal loss occurs (or explicit kill command received), then:

1: Electromagnet loses current

2: Spring steel snaps over to top of spark plug

3: Spark shorted to ground.

4: Engine stops pretty quickly.

Bob Ammerman
RAm Systems
(contract development of high performance, high function, low-level
software)


----- Original Message -----
From: "Herbert Graf" <mailinglist@FARCITE.NET>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Thursday, August 09, 2001 4:16 PM
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
>
> --
> http://www.piclist.com hint: To leave the PICList
> mailto:piclist-unsubscribe-request@mitvma.mit.edu
>
>

--
http://www.piclist.com hint: To leave the PICList
mailto:piclist-unsubscribe-request@mitvma.mit.edu