[sdiy] Driving LEDs

[Chris Williams]

You could use two 4-16 line decoders (CD4514 I think) and use the 5th
bit to control the inhibit line of each decoder - you'd need some
inverters also.

That way, if the 5th bit is high, enable the second decoder, otherwise
enable the first decoder. Wire the 4 other bits to both decoders.

Someone let me know if I'm smoking crack, but this should work.



-----Original Message-----
From: owner-synth-diy at dropmix.xs4all.nl
[mailto:owner-synth-diy at dropmix.xs4all.nl] On Behalf Of John Blacet
Sent: Tuesday, 23 December 2003 1:09 AM
To: synth-diy at dropmix.xs4all.nl
Subject: [sdiy] Driving LEDs

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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