In message <9507282115.AA02041@superior>  writes:
> This is a question for the "electronically inclined" out there. How
> difficult would it be to set up a three LED indicator that would tell the
> driver if the O2 Sensor is reading rich, lean, or "stochiometric" for one
> and three wire FI systems? Such
> a device might be helpful as a way of assessing basic driving habits and
> engine tune.
> 
> Thanks  for any ideas.
> 
> DC

I'm by no means an expert on O2 sensors, but I just happened to have a reprint 
of an article titled "Lambda closed-loop control" on my desk that I've been 
perusing.

I quoteth: "The voltage supplied by the lambda sensor as a result of the oxygen 
content in the exhaust reaches 800...1000 mV with rich mixtures (lambda <1), but
it is only about 100mV with lean mixtures (lambda >1). The transition from the 
lean to the rich range lies at 450...500 mV." Reaction time is <50 mSec.

Soooo, you should be able to do it easily with a regulator and something like an
LM3914 to drive the LEDs. You might like more than 3 to get the resolution you 
need. This is a pretty simple circuit if you've ever breadboarded a circuit. If 
not.......

I think someone on the list has a commercial version of this. If you build it 
yourself, the materials would be less that $10.

Happy (exhaust) trails.

-Erik

NSC Analog Automotive Systems  Tel. (408)721-3476  Fax (408)721-8292  M/S C2611