Questions about EGOR

[garfield at pilgrimhouse.com]

On Wed, 06 May 1998 15:30:59 -0800, Ludis Langens <ludis at cruzers.com>
wrote:

>What sort of power source does EGOR need (not counting the heater)? 
>12V?  5V?  Both?

Hey, Lulu.

Lemme say a couple things about what Sandy and I have discussed so far
about EGOR's "home", or the pc-board Sandy's gonna layout for us all. It
will be his design discretion and call, of course, but my request to him
was to make it a "module" that could be either plugged into a board
(with suitable 0.1" headers/sockets) for those wanting to make
"instruments" like meters, dataloggers, etc. and ALSO could be soldered
onto/into thru holes in a larger board, for those making engine managers
(where vibration won't allow insertion force connections to be reliably
used). Since most all the devices, excepting the idea I mention below,
can be had in surface mount, the entire EGOR board is likely gonna fit
in something WAY shorter than a 40-pin 0.6" DIP. Yep, you heard me
right, it's that small.

I haven't discussed these niceties with Sandy yet, partly cuz he's an
old hand at this already (grey hairs, maybe?), but if the 5V regulator
is left as a thru-hole device, then if you didn't have 12V available,
you could leave the regulator out, treat the regulator pin that would
normally source the 5V as another module pin, and so you can use either
12v or 5v. My own preference would be that you'd use 12v and this
regulator, cuz the regulator spec'd in the design is a special one for
automotive, that has all kinds of protection, including load dump,
double battery, reverse battery, ALT field collapse protection, blah
blah blah. It's made for automotive, let's put it that way. And it needs
less than 1V headroom to maintain regulation, so it will work well below
lowest, coldest weather, crummiest battery cranking voltage. So IF you
have BAT+ available whatever your app, I'd say stick with that and use
this regulator. The precision references run off this 5V, so I'd want a
good regulator looking over them.

Beyond that, suffice it to say that EGOR uses the most wunnerful op-amps
yet to grace the earth for engine electrics guys, Analog Devices OP-x96
family (in EGOR's case OP-496's, quads). They are true rail-to-rail,
super-low power, VERY low drift and noise floor (not meant to be used
above say 100KHz practically speaking, perfect therefore for automotive,
which is how they get the noise figure down so low), and of course
single supply, all the way from 3V to 16V if memory serves. So they are
just perfect, I use em ALL the time, and they work just swell on 5V,
especially protected by that NatSemi LM2930 regulator.

>How much current is needed at 5V?  Putting this another way, is the
>current draw low enough to use an ECM's regulated 5V output meant for
>sensors (TPS & MAP)?

Yeah, I think you can count on that, if you NEED to. It's so low, I
didn't bother adding it up, but I'd say way below 50mA @ 5V. But again,
I'd prefer you going off B+ like another other sensor, rather than a
slave off the ECM, cuz there's plenty of room on EGOR, the regulator no
way needs even a heat sink the load's so small, and that way you don't
add to the load budget of the ECM. Always best to stand alone off BAT+
if you can.

>Could EGOR use dual 5V supplies - one for internal circuitry, and one
>for the source of current sent to the O2 sensor?  The idea is to protect
>against short circuits in external wiring.  If the O2 harness gets
>mangled by a fan, or melted by a manifold, thus shorting all the wires
>to ground, the sensor supply can shut off.  The internal supply can keep
>working, allowing an error code to be reported.

Nope, it's way too intertwined for the isolation yer hoping for. A noble
goal, but in this puppy's case, especially since NTK & the HONDA
bean-counters decided to save an extra wire from the sensor harness, the
Ion pump and O2 VsCell sensor are commoned on one lead, so tryna isolate
the supplies for the Ip Cell and the VsCell leaves you with just one
lone op-map that's free of danger. If the Ion pump connector gets
shorted to gnd, you're gonna spill 13mA at most into the crapper, and
WAY less in the case of the VsCell bias, so not to worry about EGOR
hemorrhaging.

I understand the thot process, and coulda saved ya several synapses if I
had mentioned earlier how low power this whole operation actually is.
Suffice it to say, the main worry about pranging the harness, is
shorting the HEATER supply lines, which have to be fused for greater
than 5A at startup. So, you needn't worry about poor ole EGOR bleeding
all over the place if his lifeline is severed. As far as setting error
codes, as with anything like this (I'm assuming you've brought this up
cuz you're thinkin bout yer own engine manager), when you can't use
POWER issues to tellya when somethin's rotten in Denmark, probably
oughta watch for lack of "changes". This is a tradeoff we have to make
with wider dynamic range, in that EGOR's gonna swim all the way from
deep to shallow end, cuz he can swing rail-to-rail to give max range of
leanNrich, but as a result, you can't anymore say, "if at rail, then
fault". Price you pay for "glory", I guess.

This brings up another pet peave of mine, in that lots of stuff has
apparently been designed assuming op-amps would always be as lame as the
80's, so designers used the idea that "above a certain level" was
"out-of-range". This is a totally bogus design idea, and these guys
obviously were living for the moment. Everyone knew that FET technology
was gonna do away with that "diode junction" crap, but they went ahead
and designed it into systems as if it was a law of nature. As a result,
we've inherited from older auto systems, the loss of over 1V gnd/supply
headroom, outta 5V. 20%+ loss of system range is alot to give up to a
temporary artifact of bipolar technology, but it's there. The pits,
dudes.

Another example of this "food-chain paradigm" we're all suffering from;
these guys probably figured by the time reality caught up with them,
they'd be "managers" and therefore immune to technical criticism. Hey,
life in the fast lane, everything changes in 5yrs, and if you're in a
diff. place by then, not to worry. What a bunch of irresponsible
horse-pucky. As my father used to say, "Old man WRONG goes down the road
and waits for ya". Them guys oughta have their cars croak on them
routinely as a reward for their intrepid devotion to the art. Snarl.

>Is EGOR's 0 to 5V signal output range a "natural" range?  How much of a
>load can the output drive?  It appears that GM ECM's often have an
>unused analog input with a 1000 ohm pullup to 5V.  Can EGOR drive this?

"Natural"? that's a new one on me. Is that similar to "Organically
grown"? EGOR's output will be exactly the same as the NTK box, if you
want to plant Virtual Ground/Stoich on 3.0V like NTK does, OR (my
personal preference) on 2.5V as any sane analog guy would do. I believe
NTK picked 3.0V to give them some more "range" on the rich side, cuz
they weren't able to use rail-to-rail amps, and so were somewhat limited
with say 2.0V of swing for the rich side. With EGOR's better innards,
you could "do the right thang, analog-wise" and plant the virtual gnd at
2.5V (i.e. mid-supply) like all the big boys do.

As far as your GM ECM's 1K/5V "free input", I'd say any system that
expected ANY output to be able to drive 1K into 5V is really asking for
disgusting jokes about their mama. That's pretty low impedance. BUT, yes
EGOR can handle that, since the final voltage output stage is a fully
buffered unity-gain follower, just for them turkeys that think
everything rotates around them. Sheesh. 1Kohm input impedance; da vewy
noive! Harrumph. Course, you gonna pay for that with increased supply
load, but it's still only another 10% of budget, so no sweat.

>Can EGOR be designed with an output range of about 1 volt?  This would
>allow EGOR to directly drive an ECM's existing O2 input(s).  (It's a
>trivial matter to edit a PROM to handle a different O2 input voltage
>profile.)

NO, this ISN'T gonna be possible, and for an even better reason than
just "levels" issues. If you read the previous posts, the output of
these Ion Pump interfaces is in NO way similar to a stock O2 sensor.
Additional, albeit simple, interface circuitry is required. I can't take
the space AGAIN to outline this; suggest you climb back up the thread a
day or two's worth and see the discussion about how EGOR is gonna be
pin'd out to allow use in ALL kinds of diff. apps. It discusses things
like what you've asked about interfacing to diff. kinds of systems.

>Alternately, does it make sense to monitor one of EGOR's O2 cells using
>an ECM's existing (differential input) O2 amp?
>
>How big will EGOR's circuit board be?

All answered in the aboveNbeyond.

>I went to a library and looked up how Honda wires their "LAF" O2
>sensor.  This sensor is used only on the 49 state '92-'95+ Civic 1.5
>VTEC.  The California emissions version of the same car&engine gets a
>standard 4 wire heated O2 sensor.

Bzzzzzzzt. I can't cite you chapterNverse of the year/model of the VX
Civic, but I've BOUGHT sensors for our year/model range IN CALIF, and
they ARE 5-wire and suitable. What exactly are you after here? I've
ALREADY posted the Honda part number. You wanna argue with THAT, or
what? I don't get yer drift, mate.

Thanks for sharing the questions; I trust millions were served. Heh.

Garfarkle