[Diy_efi] WB 36 LED Display dimmer

[bcroe at juno.com]

1 Apr 2004  "Daniel R. Nicoson" <A6intruder at adelphia.net> writes:
 
> Is there a simple modification that would allow me to add a dimmer 
> to the LED's?  That display is great but sometimes could use a 
> dimmer.  I haven't had a chance to pull the data sheets on the chips 
> involved.

> Dan Nicoson

I KNEW someone would ask that, sooner or later.  The brightness
is controlled by resistors R2, R4, R5, and R8.  Note 2 & 4 are 3/4s 
the value of 5 & 8, due to different voltage across them.  Say, 
doubling values would half their current, which would also half 
all LED currents.  I would try 1st putting in values like 8 times 
these and see if thats the right dimming.  Once adjusted, 
connect  a resistor like the original to pin 6-7 of each LM3914.  
Tie the other end of each resistor to the anode of a 1N4004.  Tie 
the 4 '004 cathodes together.  When the 4 cathodes are grounded 
by a switch, the second resistors will increase the brightness.  

You could also get a linear control using a 4 output current 
generator, or a pulse width modulated LED supply.  A lot more 
complicated.

Bruce Roe
_______________________________________________
diy_efi mailing list
diy_efi at diy-efi.org
http://lists.diy-efi.org/mailman/listinfo/diy_efi