WB-LED display

[bcroe at juno.com]

It sounds like you're pretty close.  No LEDs at 2.5v.  

2.75 Vout is 17.93 A/F.  That should just about turn
on 8 lean LEDs.

You should get 20 LEDs on the rich side for Stoich
minus 1.129 V, or 1.371V.  1.75 Vout is 11.2:1 A/F, 
which is about 13 rich LEDs.

Sounds like the gain is too high on the rich side and
too low on the lean side.  If you switched R3 and R14, 
it would do that.  Check that you have S + 2.5V, or about
5V on pins 6 & 7 of U2 and U10.  You might set it up
on the bench and feed in fixed votages to double 
check everything; hard to do when everything is 
bouncing around.

What color LEDs did you use?  Anything will work, but
I prefer red for lean and green for rich.

Bruce Roe

On Sun, 30 Sep 2001 23:21:50 -0400 "Mark S. Riley"
<turbotuneusltd at triad.rr.com> writes:
> I've built one of BC Roe's WB-LED displays 

> With the volt meter still hooked up and the led display also,
> I see no LED's at 2.48-2.52 volts like I should. If the voltage 
> goes up to 2.73 volts, then according to the data sheet, I'm 
> figuring I should be seeing the 6th lean led light up. 
> However it only goes to #4. 2.75 volt lights the #5 led. 

> To the rich side, 1.75 volts lights all 20 across and I figured 
> that it should be on the 13th led RICH. I measured 7.98 
> volts on the 8 volt circuit. 6.24 to the LED's. 2.50 is the ref 
> voltage out of the wide band. It's like I've gotten it too 
> sensitive somehow. I'll keep checking, maybe I've gotten 
> a resistor in the wrong place. But, it sure looks good
> even if I did do it.
> 
> Thanks, BC. I really appreciate it.  Mark
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