switching circuit for crank ref. signal needed (please help)

[Orin]

> Orin wrote:
> 
> > The actual Audi input circuit for the timing reference sensor is out
> > on the ftp site incoming directory in mac11schem.zip.  This is the
> > order of complexity required to process that signal.  A 4066 could be
> > snuck in on the input side, but I'd gate the output from the
> > comparator with the hall sensor signal.  A 74x00 would be enough -
> > even if both inputs and output needed inverting...
> 
> The idea was to use the 555 to enlarge the time window of the cam reference
> pulse, I wrote without thinking. Enlarging the physical window in the
> distributors trigger wheel is a better option.

Trouble with the 555 idea is that the time window depends on RPM.
The window in the wheel is 20 cam degrees anyway and you can position
it by rotating the distributor.

> > > I have thought about another option, if all three stock sensors are
> > > connected to a small microcontroller you could let the
> > microcontroller count
> > > the teeth on the flywheel and keep track of the two sync
> > sensors. That way
> > > you could simulate a suitable trigger setup.
> >
> > Easier to leave the stock ECU connected and pull the signals out of it
> > after signal conditioning.  Not too hard to do given the schematic.
> > I've pulled these signals out for my data aquisition board
> > without a problem.
> 
> True, but not effective if you do a turbo transplant on a 80q. You wouldn't
> know how to extract the knock signal from the ecu, would you?

Well, I've made the ECU output a signal when it detected knock, but it
required a change to the code.  I've done it two ways, set an unused
output and wire up an LED and turn the check engine light on for 0.5
seconds when knock is detected.  This assumes you are running the MAC11
for ignition timing - or at least give it enough inputs to produce the
ignition signal.

> When my rpm trigger failed I could not find a single suitable trigger on any
> of the local junkyards, other people here in Sweden has had the same
> problem. There is a strong demand on these triggers.

We gained some from blown up engines, so haven't had a problem yet.
Some day I'll see if the sensors in the electronics catalogs would work.

Orin.

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