Knock sensing and retarding ignition

[RichM]

The problem here may be the signal levels, if you're trying to trigger the
LM1815 from a hall effect sensor - the 1815 needs to see the signal pass
through zero volts (it is intended to condition reluctor signals which are
AC), the output changes state at the negative going zero-CROSSING. A
hall-effect signal will not go negative, it'll be lucky to reach ground and
the LM1815 is unreliable with signals that 'just' reach ground.
Maybe you could try AC coupling the hall signal.
Cheers
Rich

----- Original Message -----
From: Joseph Obernberger <joelori at earthlink.net>
To: <diy_efi at diy-efi.org>
Sent: Friday, January 25, 2002 2:29 AM
Subject: Re: Knock sensing and retarding ignition


> Hi,
>     I too have tried the LM1815 without much success - let me know what
you find
> out!
> :-)
> What sort of ignition does this engine use?  On my car (1991 MR2 Turbo)
and on
> various other japanese cars (RX7 for example), the ignitor just takes a
nice 5
> volt pulse to fire the coil.  The pulse width is the charge time, and the
> ignitor fires on the down transition of the pulse.
> On the MR2 the ECU gets two signals from the distributor (hall) and
outputs a
> signal (5 volt pulse) to the ignitor.
> Not sure if that helps any...
>                                                 joeo
>
>
> Stephen Webb wrote:
>
> > *I have experience with pics, and I was able to interface with the MAP
> > sensor too, but I have had trouble getting the LM1815 to work with my
> > distributor.  I believe I may be playing with a bum distributor.  I
should
> > have another one in a few weeks to play with, and maybe I will get
> > something going again.
> >
> > *I'm not sure of a "good" way to trigger the ignition module from the
> > pic.  Normally it sees the signal from the distributor, which I don't
know
> > how to replicate, but I suspect there is an easy way to reliably trigger
> > the thing.  Anyone?
> >
> > The MSD unit is the easier route, but I don't know how much it costs.  I
> > can tell you that I will have $40 tied up in parts for this project, for
> > whatever that's worth.
> >
> > -Steve


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