--- brusque@hotpop.com wrote:

> Hello,
> 
>      I'm working on a project that is basically a high intensity LED 
> sign. My actual design is using some 74HC595 to power the LEDs the
> LEDs:
> 
>      Controller        long data                LEDs
>         unit              cable                 unit
>      ,---------,                            ,---------,
>      |         |                            |         |-------LED1
>      |     DATA|----------------------------|         |-------LED2
>      | PIC     |                            | 74HC595 |-------LED3
>      |       CK|----------------------------|         |-------LED4
>      |         |                            |         |-------LED5
>      |    LATCH|----------------------------|         |-------LED6
>      |         |                            |         |-------LED7
>      |         |                            |         |-------LED8
>      '---------'                            '---------'
> 
>      However, the maximum currente at the '595 outputs are 6-8mA and
> I need to power the LEDs with 20mA, to have more luminosity.

I've used Philips and SGS HC595's up to 19 ma no problem with 150ohm
current limiting resistors.  The big thing is to be sure your power
supply can handle it. I was driving a bar of 40 LED's at ~20ma each.
(800ma) If you still are nevrous with this thought. Then observe this
site:
http://www.allegromicro.com/
in particular you might be interested in this selection
http://www.allegromicro.com/ic/
These source drivers
http://www.allegromicro.com/ic/source.asp
or 
these sink drives
http://www.allegromicro.com/ic/sink.asp
> 
>      I've been thinking about the MAX6966, but it's expensive and not
> easily available. Another possibility would be to use some PIC16F627A
> on the LEDs unit just to control the LEDs.

See above! Happy hunting :)


Stephen

=====
Stephen R. Phillips was here
Please be advised what was said my be absolutely wrong, and hereby this disclaimer follows.  I reserve the right to be wrong and admit it as well. :)


		
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