[sdiy] LED matrix

[Tim Parkhurst]

If the LED matrix is multiplexed, will all 32 LEDs be on at the same time? I
don't think you'd ever see the 1600mA current, but I can maybe see the 400mA
figure. Is this right?

Tim Servo

******************************

> -----Original Message-----
> From: The Old Crow [mailto:oldcrow at oldcrows.net]
> Sent: Tuesday, May 27, 2003 3:51 PM
> 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...?).



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