Some questions on DIY EGOR schematics

[Marteney, Steven J.]

Admittedly, I went into refinement mode on many points, bad habit.  But the
use of a 7808 to generate +/- 2.5V is counter-intuitive.  Until I build
mine, I'll assume the voltages were really meant to be labelled as +/-4V.
This will make it easier to best-guess a level-shifter circuit for removing
the +/- swing and placing it on a 0-5V (or other) scale for some add-ons I'm
planning.  Of course, these will be shared with the group.

Steve :-)

-----Original Message-----
From: Bruce Plecan [mailto:nacelp at bright.net]
Sent: Tuesday, November 21, 2000 4:57 PM
To: gmecm at diy-efi.org
Subject: Re: Some questions on DIY EGOR schematics


> 1) Noticed the use of an op-amp and 7808 for generation of +/- 2.5V by
> setting a virtual ground point.  Is this meant to be a 7805?

Nope you want the 8v version

Just wish a few folks would build them as is and refine it as we go rather
then trying redsign it before even trying it.
Bruce


 Splitting an
> 08 in two would yield +/- 4V rails, correct?   Or, is that circuit just
for
> simulation purposes in the schematic tool?
>
> 2) Also, noted 8V used on pot (R44) to set a voltage.  Seems one could use
> 12V, or a regulated 5V, since the voltage set point doesn't seem to appear
> to be greater than the +/- 2.5V range of the amp (???) (I may be missing
> something here.)
>
> 3) I assume the ground on the heater schematic page is different than the
> ground on the controller page that it is generated by op-amp U1A and the
> 7808?  (Which makes me curious about yesterday's questions about using a
> max232 to generate a negative voltage.  Seems the schematics account for
> that with the virtual ground point.)
>
> 4) Further adding on to the virtual ground point, it is connected to
vs_gnd
> on the sensor.  Is the sensor happy with having a system ground
potentially
> on its case (via exhaust pipe ground) and basically a DC bias on the
vs_gnd?
> (I don't know anything about the internals of this thing.)
>
> 5) The sensor pinout lists the wire colors of 5 pins, which I believe I
can
> reference to the schematics.  The pinout also lists Power, Ground, and A/F
> output.  Are these not used on the sensor (ala 5-pin O2 sensor) or is it
an
> 8-pin connector with only 5 wires coming from it?
>
> 6) Is there a datasheet on the sensor used?  I haven't been able to get
very
> far on the NGK site.  One on DIY site?
>
> This is awesome work!!!  The Excel tables will be infinitely helpful I'm
> sure.  Thanks to Bruce, Chad, and all the little guys!!!
>
> Steve (will be giving thanks for the release of DIY EGOR :-)
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