[sdiy] LED matrix

[Bert Schiettecatte]

Hi Crow,

I don't see why I would need so many amps to drive the matrix. I'm just
going to turn on each led a very short time and cycle through all of them.
I was hoping to use an Atmel microcontroller for that. Thanks for the
suggestions on the UDNxxxx... I'll check those out!

bert

-----Original Message-----
From: owner-synth-diy at dropmix.xs4all.nl
[mailto:owner-synth-diy at dropmix.xs4all.nl]On Behalf Of The Old Crow
Sent: woensdag 28 mei 2003 0:51
To: synth-diy at dropmix.xs4all.nl
Subject: RE: [sdiy] LED matrix



  You can use 4051s to select the columns and rows, but the drive current
for columns/rows will need to be something hefty.  I myself would use
the venerable UDN2981/ULN2003A current source and sink arrays: source to the
anodes, sink to the cathodes.  For reasonable brightness a multiplexed LED
needs a narrow (2ms) pulse of something like 50mA.  Eight of these would
need 400mA, and 32 of them, 1600mA.  I have a very large led matrix
display (something like 80x320 LEDs) that uses a 5V at 30A power supply.  It
uses power transistors in place of darlington arrays, as each column of 80
must sink 4 amps.  I think the ULN2003 is good for 500mA per section, so
eight LEDs at full pulse brightness is no problem.

Crow
/**/

On Wed, 28 May 2003, Bert Schiettecatte wrote:

> A totally other question : I'm not an expert on CMOS/TTL IC's, I'd like
> to use a couple of 4051's to interface a big 32x32 discrete LED matrix
> to my AVR. Is this possible? Does anyone have a more efficient way of
> doing this interfacing? I'd like brightness control over each LED
> (through PWM...?).