DIY_EFI Digest V5 #385

Chad Clendening clendenc at execpc.com
Wed Nov 15 16:23:01 GMT 2000


1) The regulator really needs to be a 8 volt variety.  Even with a good op amp,
the 5 volt regulator didn't have enough headroom.  The V+2.5 and -2.5 are not the
actual voltages present.  It was more like v+3 and v-5
The artificial ground isn't evenly split since more negative current is needed
than positive current.

2) The early data was taken with a earlier prototype and the I to V amp was wired
differantly.  It was taken as a meter was laying around doing nothing.

Chad

>
> Date: Tue, 14 Nov 2000 20:37:59 -0500
> From: "NickG" <nikog at mediaone.net>
> Subject: DIY EGOR plans
>
> I've been looking over the plans of the DIY EGOR tonight (thanks Bruce!).
> I'll throw some questions/comments out regarding it:
>
> 1) it looks like the circuit needs a positive AND negative voltage supply
> (+2.5v and -2.5v relative to ground). I'm thinking of either using a 555
> timer or an astable oscillator to make a switching power supply using a
> small transformer. Comments? Easier methods?
>
> 2) In the Data(2) sheet of the UEGO Data spreadsheet has some conflicting
> information. Cells G6-G20 go from negative to positive voltage (as the
> mixture gets leaner), while cells D31-D44 go from positive to negative
> voltage as the mixture gets leaner. Which is correct?
>
> Thanks,
> Nick
>
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> ------------------------------
>
> Date: Tue, 14 Nov 2000 21:05:07 -0500
> From: Barry Tisdale <btisdale at cybersol.com>
> Subject: Re: DIY EGOR plans
>
> At 08:37 PM 11/14/2000 -0500, you wrote:
>
> >1) it looks like the circuit needs a positive AND negative voltage supply
> >(+2.5v and -2.5v relative to ground).  Comments? Easier methods?
>
> Plans have a vreg (incorrectly shown as 7808 - should be 7805) feeding an
> LM324 - what could be simpler than that?
>
> >2) In the Data(2) sheet of the UEGO Data spreadsheet has some conflicting
> >information. Cells G6-G20 go from negative to positive voltage (as the
> >mixture gets leaner), while cells D31-D44 go from positive to negative
> >voltage as the mixture gets leaner. Which is correct?
>
> Seems to me like they track each other; realize the AFRs aren't in
> completely sorted order.
>
> Barry
> >
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> ------------------------------
>
> Date: Wed, 15 Nov 2000 17:31:03 +1100
> From: Peter Gargano <peter at techedge.com.au>
> Subject: Re: DIY EGOR plans
>
> NickG wrote:
> >
> > 1) it looks like the circuit needs a positive AND negative voltage supply
> > (+2.5v and -2.5v relative to ground). I'm thinking of either using a 555
> > timer or an astable oscillator to make a switching power supply using a
> > small transformer. Comments? Easier methods?
>
> Nick,  If you look closely at U1A pin 1, you'll see that it's output
> is "grounded" and the schematic indicates it's at 0 Volts - What's
> really happening is that the U1A op-amp is "dividing" the voltage
> between pins 2 and 3 of the 7808 (perhaps this should be a 7805?)
> regulator, into a "positive" and "negative" voltage of magnitude that
> depends on where the wiper of R46 is. The Voltage shown as V-2.5 is
> really at the "gnd in" potential and is presumably the vehicle's GROUND,
> and the V+2.5 voltage is at the potential of the regulated five volts.
>
> Put another way, U1A produces a "ground reference" that other signals
> are measured from. You don't need a negative voltage generator!
>
> Peter.

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