measuring hall output

[auditude at neta.com]

On 22 Feb 2002, at 15:37, Orin Eman wrote:

> > Hence, my question about if I can just calculate the position, by
> > telling the ecu vendor that the falling edge is 20 degrees ahead of
> > 62 btdc, and the rising edge is 20 degrees after 62 btdc.
>
> Yes, if the distributor is properly set which it won't be.
> To be honest, that measurement wasn't particularly accurate, so
> just use one edge of the signal.

Okay, if the ABOVE is the answer to my specific question "in it's
entirety", and the rest of the post BELOW is about "something
different", then I understand totally.  Thank you very much!

I believe the rest of your post BELOW is describing to me what I
will have to do LATER, once I get the aftermarket ecu in hand and
need to set it up.  If this is true, then I am not confused (any more).

However, if the rest of your post, below, has anything to do with the
CURRENT task at hand, such as understanding the output of the
hall sensor, then I'm confused again. (and I can send one of the
first two emails I drafted that try to understand what you have
posted.  I think they are based on a misunderstanding of what the
"intent" is of procedure you describe.)

>  Let me make this perfectly clear...
> you will have to set the distributor position with a timing light if
> you are using it to drive the ignition.  The ECU will set a particular
> timing at idle, you put a mark on the flywheel at that point and you
> rotate the distributor until that mark is at the bellhousing reference
> as seen with the timing light when idling.  There is no need for
> anything fancy to place the mark - each flywheel tooth is 2.7 degrees.
> Count teeth from the zero and interpolate as necessary.
>
> There is nothing magic about the positioning of the hall sensor window
> if you aren't using the timing pin.  It's just that if you use the
> existing reference marks on the distributor, that's where the window
> will be.

I understand the rest of that post, above, AS LONG as you are
describing to me what I will have to do to setup the aftermarket ecu
after it is configured, delivered, and installed.  You are describing
how to "exactly center" my distributor, so that the location of the
hall sensor leading/falling edge, matches up with what the
aftermarket ecu is expecting (based on my specs).

If you are telling me what I think you are telling me, then I totally
understand that part.  It is exactly what I intended to avoid with that
circuit idea that I'm not pursuing.  The timing is relative to
distributor location.

If you are describing anything that has to do with my CURRENT
stage of the project, which is to understand the output of the hall
sensor, then I'm confused again, sadly.

I was confused at first, because I thought you were describing how
to do something to get data from the hall sensor signal, while idling
with the stock MAC11.  It was the fact that ignition timing shouldn't
change relative to the distributor location with the stock setup
(right?), that helped me to understand you are talking about "later"
and not "now".

See, I'm learning how to read your emails! :-)  It takes me a few
tries, for me it hasn't been intuitive.

I'll confirm they can use just the leading/falling edge of the hall
sensor for the sync pulse.  I did speak to the vendor today, and he
confirmed that everything is the same, just waiting for me to provide
the trigger data.

Thanks Orin!

Ken