WB-LED display

[bcroe at juno.com]

I don't know what to say, except it works better wired right.

On Mon, 1 Oct 2001 22:37:48 -0400 "Mark S. Riley"
<turbotuneusltd at triad.rr.com> writes:
> 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? 


Check pin 8 of U8 to see if it just swings from gnd to 7V
as you go above 2.47V in.  If so R3 may be open ckt.  If
you short pins 8 & 9, and the swing becomes very small
(stays around 2.5V), U8 is probably OK.  

Bruce Roe



> 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.
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