[sdiy] Driving LEDs

[Jay Schwichtenberg]

John,

Use a matrix driver like your driving a seven segment display with multiple
digits. Use a 3 to 8 and 4 driver pins (7 PIC bits) to form a 8 x 4 matrix
which 20 LEDs are in. Use a common anode or cathode thing on a string of 8
LEDs and control each string with the driver bits. You would need to cycle
through the 4 strings fast enough that the user wouldn't notice.

Jay

> -----Original Message-----
> From: owner-synth-diy at dropmix.xs4all.nl
> [mailto:owner-synth-diy at dropmix.xs4all.nl]On Behalf Of John Blacet
> Sent: Monday, December 22, 2003 9:09 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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