[sdiy] Driving LEDs

[Harry Bissell Jr]

How about shift registers and a cueue'd serial
connection... you'd send out a clock and data
from the pic on two pins.  You could clear the
whole thing by writing out more zeros as data than the
length of the register...

Or... if you have D/A out capacity, stack two
LM3914 chips in "dot" mode.  You can series the
strings, use a divider to get 1/2 the supply voltage
and then buffer that to the middle of the divider
string. That would compensate for the possibly
different
internal resistor values.  (contact me offlist
if you're interested and didn't get what I just
suggested)

Prlly the shift register is the cleanest

H^) harry

(does this mean I get a free one when its built ???
:^)



--- John Blacet <blacet at blacet.com> wrote:
> OK, here's the problem:
> 
> I need to drive 20 LEDs from a PIC type uC. The LEDs
> are on a separate
> board so I want to keep the number of interconnects
> small. I only need
> one LED at a time to be on. So, I seem to need a
> decoder with 5 lines in
> to 20 out. Most of the stuff I see is 3 to 8. Any
> ideas?
> 
> --
> Regards,
> --/////--
> John Blacet
> Blacet Research
> http://www.blacet.com
>
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