REFLECTOR: Magneto P-lead pickup circuit

[Brian Michalk]

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