What display for DIY WB

[bcroe at juno.com]

As others stated, saparate output devices are working
for bar graph, digital, and RS232.  No board for the bar
graph just yet.

The brightness of the LED bar graph display is directly
controlled by  the resistor from pin 7 of each LM3914 to
ground, R2, 4, 5, & 8.  If you double the value, the LED 
current will be halved; triple will cut to 1/3.  Perhaps a
second resistor of 1.5 times the value between the above 
and ground will do the job.  You could put 4 diodes from 
the junction of each pair and switch the other side of all
4 diodes (cathode) to ground for higher brightness.

There is more than one way to skin a cat, but right now
I don't see an obvious better way to drive those 36 LEDs
than LM3914s.  Those outputs are current regulated.

The 2 18 ohms are there because a 9 ohm 1 watt is much
harder to find.  If they are increased much the LM7808 
will run out of headroom and regulation when every green
LED is on.  If you elect to REDUCE the resistors mentioned
to 1/2 half for maximum brightness (20 ma), you would need
4 18 ohm in parallel and twice the heat sink on the LM7808.

Bruce Roe

On Sun, 9 Dec 2001 23:31:15 +1000 "Con Torrisi" <mini at bretts.com.au>
writes:
> Hi everyone,
> 
> After several attempts to build a reasonable narrow band Mixture 
> meter with
> limited success I've decided to have a go at the WB project.
> 
> I've downloaded the project details but at first glance I can't see 
> what
> display is used. How do you tell what the AFR is?
> 
> Thanks
> 
> Con Torrisi.
----------------------------------------------------------------------------
To unsubscribe from diy_efi, send "unsubscribe diy_efi" (without the quotes)
in the body of a message (not the subject) to majordomo at lists.diy-efi.org