Building a stimulator

[goonie.gordon at talk21.com]

Fair point Bevan - I didn't read the mail properly - I was having a browse over lunch...
:o)

>  from:    Bevan Weiss <kaizen__ at hotmail.com>
>  date:    Wed, 10 Apr 2002 02:14:20
>  to:      diy_efi at diy-efi.org
>  subject: Re: Building a stimulator
> 
> I think that at these kind of frequencies an analog filter just wouldn't cut
> it, the passband of the filter would be too great(without talking bout
> crystals/ceramics).  And that's even if you can get an adequately stated
> passband.  After all if you try and filter out the harmonics for a 1000RPM
> signal, then surely you wouldn't be able to pass a 2000RPM signal, let alone
> a 5000RPM signal.  And only a couple of harmonics are needed before the
> signal doesn't look very sinusoidal anymore...
> 
> I would be more inclined to think that the reason that the ECU isn't being
> fooled is that it's expecting a negative shoot, the waveform should go
> sharply negative then positive (or vice versa).  However a zero crossing
> should occur, and I would believe that it's this that the ECU would trigger
> on.  You could do several things...
> 
> Use the sqaure wave to trigger a seperate transistor which could drive an
> inductor to create a ringing whenever a pulse is applied.  This will give a
> zero crossing, but may give more than one...
> 
> Possibly use some kind of DC offset (with reference to the detector circuit)
> so that when the pulse is applied the detector see's a zero crossing.
> 
> (NB: This all assumes an inductive 2 wire pickup is normally used to create
> the signal.  ie it would go negative as the ferous material comes closer to
> the pickup, and then positve as the ferous material goes further away from
> the pickup)
> 
> PS: I haven't done as much in the EE field as some others on this list, so I
> would take other advice (esp: Bruce's) over mine.
> 
> ----- Original Message -----
> From: <goonie.gordon at talk21.com>
> To: <diy_efi at diy-efi.org>
> Sent: Tuesday, April 09, 2002 2:36 PM
> Subject: Re: Building a stimulator
> 
> 
> > Hi Wayne,
> >           I'm surprised that the square wave does not register as a
> trigger.  If you want to convert into a sine wave then it's easy as a square
> wave is made up of harmonics of the basic sine wave - All you need to to is
> make up an active unity gain low pass filter with some capacitors, a couple
> of resistors and an op-amp.  Anyway the filter should pass only the
> fundametal frequency and hey presto one sine wave.
> > This stuff should be easliy picked up from academic text books on
> electronics but if your having trouble I could look out some examples.
> > :o)
> >
> > >  from:    Wayne Macdonald <wmcdonal at optushome.com.au>
> > >  date:    Tue, 09 Apr 2002 13:24:48
> > >  to:      diy_efi at diy-efi.org
> > >  subject: Re: Building a stimulator
> > >
> > > I am building a stimulator to run a Sagem ECU on a test bench, I want to
> > > generate the crank trigger from a micro but I am having problems.
> > > The ECU expects to see a waveform from a normal two wire crank trigger,
> The
> > > square wave I am generating does not seem to fool the ECU.
> > > Can someone help me with the circuit required to convert a square wave
> into
> > > a sine wave.
> > >
> > > Thanks
> > >
> > > Wayne
> > >
> >
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