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On Thu, Nov 15, 2007 at 12:58:03PM +0800, Xiaofan Chen wrote:
> On 11/15/07, Peter Todd <pete@petertodd.ca> wrote:
> > Researching this is looks like for large panels the usual way is to use
> > high voltage DC, often rectified directly from the 120VAC and use
> > massive strings of leds. For instance the NUD4011 low current led driver
> > is used to regulate current in such setups directly off of rectified AC.
> >
> > I'm not much of a high voltage engineer, so I would rather keep to
> > something below 48V.
> 
> High voltage may not be that difficult to deal with if you use Supertex
> or some other parts.
> 
> http://www.supertex.com/feature_LED_general.html

I gotta admit I'm nixing high voltage not because of difficulty in the
circuit itself, those linear regulator based circuits look fairly
simple, but rather because I'm selling this stuff to other people and I
have no qualifications what-so-ever in anything safety related. If, say,
the plexiglass cover on the PCB falls off or cracks I'd rather
everything be touch safe.

That said, they make some very interesting chips, especially the fixed
current source ones like the CL25. One part for a temperature controlled
25ma current source could save me a lot of parts. The online store to
order them is reassuring too.

- -- 
http://petertodd.org
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