Starter Tooth Sensor Question

[Bernd Felsche]

bcroe at juno.com tapped away at the keyboard with:
> On Tue, 11 Dec 2001 14:14:08 +1100 Peter Gargano <peter at techedge.com.au>
> writes:
> > bcroe at juno.com wrote:
> > > A counter of the same module could keep track of
> > > crank position.  But another sensor is needed to sync
> > > the thing.  I have some hall effect devices that adjust
> > > themselves to the signal level.

> > This is the job for a small "intelligent" device like a PIC.
> > It can also easily distinguish missing (or extra teeth) easily
> > (eliminating a separate sync pickup). Less than US$5 for
> > 5 MIPs - amazing!

> Yes, even if a tooth is a bit battered, it only represents
> a couple of degrees.  Battered or not, it will not be 
> moving into the position of an adjacent tooth.  And the
> the shaft runout should be pretty small compared to 
> tooth dimensions.  

> A PIC ought to do it, if it can match the top RPM rate.  
> But I won't be knocking a tooth off it, so something 
> else will be needed for sync on the flywheel, and a 
> second crude sync from the cam/distributor.

Anybody who wants to try this could save themselves re-inventing the
wheel by reading SAE Paper 1999-01-0203 "Enhanced Engine Position
Acquisition & Treatment" by Patrick Leiteinturier and Joseph Benning
of Siemens. It describes how to eliminate errors resulting from
tooth geometry and other factors. The maths looks complicated but
can be understood if accompanied by a glass of wine or three.

The paper also appears in SAE publication SP-1418 "Electronic Engine
Controls 1999" (which is where I found it). The latter also contains
papers on integrated in-connector control electronics for NOx
sensors, ion current sensing, individual cylinder fuel control with
a switching oxygen sensor; and a dozen other similar papers. Only
three or four of the papers are probably too obtuse to be relevant
to diy.
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