REFLECTOR: Magneto P-lead pickup circuit

[Brian Michalk]

It's a Slick M-6088 magneto.

 Brian Michalk  <http://www.michalk.com>
Life is what you make of it ... never wish you had done something.
Aviator, experimental aircraft builder, motorcyclist, SCUBA diver
musician, home-brewer, entrepreneur and barely single


> -----Original Message-----
> From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org]On
> Behalf Of Jim Agnew
> Sent: Sunday, March 13, 2005 1:09 PM
> To: Velocity Aircraft Owners and Builders list
> Subject: Re: REFLECTOR: Magneto P-lead pickup circuit
>
>
> Brian,
>
> First it depends on what mag you are using, Slick or Bendix.  I have High
> Altitude (read high output) Bendix Mags and their P-lead wave
> form drove my
> electronic tac nuts requiring a change in the filtering circuit.
>
> The wave form is basically a very sharp peaked sine wave of decreasing
> amplitude (ringing) and some fixed number of cycles depending on
> the mag.  If I
> remember the Slicks had about 5 cycles and the Bendix 7 or 8.  It
> was a long
> time ago and a lot of time with an oscilloscope.
>
> Jim
> --- Brian Michalk <michalk at awpi.com> wrote:
> > I am working on my backup EFI circuit, and am considering a
> pickup off the
> > magneto P-lead as one of the RPM inputs.
> >
> > I machined a collar that mounts on the crankshaft that feeds the crank
> > position signal to the Autronic, an off the shelf engine computer.  The
> > Autronic provides spark and injection.  My backup spark is a
> magneto.  My
> > backup fuel injection is a system I designed myself.  It takes
> RPM and MAP
> > to determine commanded fuel flow, and then a fuel flow input to make it
> > closed loop.  I will be taking one signal off the tach drive, and wanted
> > another signal.  I can get it from the above mentioned collar,
> or from the
> > magneto.
> >
> > My thinking is that an alternator belt could fail, thrashing
> about and cause
> > my RPM sensor to fail.  Does anyone have a schematic on picking
> up a tach
> > signal off the magneto?  I have no idea what that waveform looks like.
> >
> >  Brian Michalk  <http://www.michalk.com>
> > Life is what you make of it ... never wish you had done something.
> > Aviator, experimental aircraft builder, motorcyclist, SCUBA diver
> > musician, home-brewer, entrepreneur and barely single
> >
> >
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>
> James F. Agnew
> Jim_Agnew_2 at Yahoo.Com
> Tampa, FL
> Velocity 173 Elite Aircraft Completed & Flying
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