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

[Orin]

> I doubt it. But you really want to count 270 teeth per cam rev... But if the
> link can do it you only need to make sure that the cam ref occurs before the
> crank ref. When the cam ref passes the hall sender you let that trigger a
> 555 timer that activates an analog switch to let the signal from the crank
> through to the ecu. A 4066 quad analog switch should work fine.

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...

> 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.

> The downside is that all 15years old very expensive Audi triggers will have
> to be kept;)

They are pretty ordinary variable reluctance sensors.  Timing and
flywheel tooth sensors are interchangeable (part numbers may be
different, but that's only the color coding of the plug on the end).
Easy to find in junk yards and also used well into the '90s.

Now the Hall Sensor tends to die more often than the timing sensors...
and officially that requires a new distributor.  But there is a
Honeywell hall sensor that looks like it will fit if you drill out the
rivet holding the original sensor in place.

Orin.

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