[Diy_efi] Jitter Filter for 36 LED bar graph display

[bcroe at juno.com]

Quite a few 36 LED display boards have gone out to those 
using the DIY-WB and possibly other WB units to tune their 
GM ecms, motorcycles, etc.  I have gotten some more 
feedback from the field on the display.

As designed the 36 LED display pretty much shows whatever 
the WB unit generates.  However, this includes quite a bit of 
jitter or flicker of the exact point.  Maybe 3 LEDs worth.  After 
some experimentation, it appears some signal filtering will 
stabilize the display (but not affect logging) WITHOUT affecting 
the practical matter of tuning.  

Some have asked about the optional C9 in the display board, 
this is its purpose.  The question was, HOW MUCH filtering?
The answer received, is C9 should be a 1 mfd non polar (don't 
use electrolytic/tantalum cap).  Use .47 mfd for less filtering.  
For more filtering, increase R6 from 4.7K to 10K or possibly 
18K (5% is fine).  Or just put extra resistance in series with 
pin 10, it adds to R6.  A Dig*key 1 mfd cap is BC1139CT-ND

Bruce Roe


On Fri, 26 Apr 2002 00:33:24 -0500 bcroe at juno.com writes:
> As you may know, I have made available a bare PC board 
> for a 36 LED bar Graph Display specifically to read out the 
> signal from the DIY-WB project.  

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