WB-LED display

[Mark S. Riley]

I sent this last night but my mail server must have been down and bounced it
back.  Yes, the gain is correct now. Works great. Mark

I found it. Bad solder connection on R3/C11 where they connect to pin 9 on
the LM2902. I didn't actually connect them to the pin but put them on the
leg of the resistor R11. It now works great. Looks like the gain is correct
both ways now but I'll check it some more. But it looks much closer than my
earlier mess. I like it!! Put it in a box from Radio Shack part # 279-1804.
6" X 2" X 1". Cut a slot in the side for the led's to stick out. Will try to
take pictures tomorrow.

----- Original Message -----
From: "Mark S. Riley" <turbotuneusltd at triad.rr.com>
To: <diy_efi at diy-efi.org>
Sent: Monday, October 01, 2001 10:37 PM
Subject: Re: WB-LED display


> I was starting to look at it when your message came in. Yes, I did reverse
> R3 and R14 along with pins 3 and 12 on the LM2902. Also had the 2 leads
from
> the rich side and lean side LM3914 to pins 5 and 10 on the LM2902. All
> backwards and it still worked not bad. Well, I straightened it all out.
What
> I did was not reference the right pins from underneath the perf board. Got
> almost all of them backwards. Changed them to correctly match the wiring
> diagram but I still had the J3 and J4 backwards. Seemed like the steps
were
> right but now the display was backwards. Switched the J3 and J4 wires so
> that now they were connected to the correct pins on the LM2902, J3-pin 3
and
> J4- pin 12. Now the rich side steps correctly, 1.75 volt  is about 12 or
13
> from center. But, now from 2.47 volt up, the entire lean side is lit
> continously unless the voltage drops down to or below 2.47 volt. Then the
> rich side looks normal but as soon as the voltage goes up to 2.48 or more
it
> lights all 20 lean led's. Have I blown the LM2902? Or what else do you
> think?  I'm going to get it right yet. Thanks for the suggestions. Mark
>
> Oh, and by the way, I got the red and green backwards. red to rich and
green
> to lean. I don't know how I was looking at it, in a mirror I guess.
> ----- Original Message -----
> From: <bcroe at juno.com>
> To: <diy_efi at diy-efi.org>
> Sent: Monday, October 01, 2001 5:03 PM
> Subject: Re: WB-LED display
>
>
> > 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



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