Re: More suited for SEB?
From: Rich Grise (rich_at_example.net)
Date: 10/29/04
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Date: Fri, 29 Oct 2004 16:48:58 GMT
On Thu, 28 Oct 2004 23:29:30 +0000, Neil wrote:
> Hi guru's
>
> trying to avoid the US election frenzy a long time lurker muses...
>
> I'm fitting a new bathroom, and have the opportunity to fit some 'mood'
> lighting.
>
> For this, I propose to modify a shaver light fitting - basically stripping
> the 240vac lamp out (I'm in the UK) and replacing with some RGB leds. I want
> the colour output and the intensity to be variable 0-100%. Thus the
> questions...
>
> Power/Safety: I intend to use a standard 240vac bathroom approved shaver
> light fitting, powered from the lighting ring with an RCD in line. Low
> voltage circuit for LEDs would be derived via a transformer supply, isolated
> from the line. Is there an easier way?
You can't get much easier than a wall wart. ;-)
> Number of LED's to use?: Don't want it mega bright, but for arguments sake,
> say I wanted similar light output to a 100w strip incandescent at max
> intensity setting? How many RGB LEDs would I need? Anybody got suggestions
> for good LEDs I could purchase in the UK? Obviously best efficiency (i've
> got to get that PSU in after all..)
John Larkin says about 800. I've wondered that myself, but I'm
pretty sure I've seen some super-brights that could put out that
kind of light with less than 800 parts!
> Colour/Intensity
> I've written some assembly before, and think I could code a 3 channel PWM to
> control each colour in the LED 0-100%. Would this also allow control of
> overall intensity, or do I need to add another PWM channel for that?
Well, if all three channels are at 0, what's the overall intensity? When
they're all at 100%, what's the overall? What happens in between? IOW,
you already have that control, just indirectly.
>I'm
> assuming I can just connect all the individual LED drive circuits in
> parallel??
I don't know exactly what you mean here. Usually, if you have the volts
available, you'd put as many into series strings as is practical - there's
less wasted in the dropping resistors that way. I'd also get a 12V or
so wall wart, and regulate it down with a 7805 for the micro, but use
the 12V for the LEDS, or maybe even go buy a big transformer, because
you're going to need some amps.
> Should I just get some gel filters?
This is kind of a different question, but it would do the trick, if
you want to figure out a handy way to change them out for the effects.
Of course, you could use dimmed CFLs behind gels, but the control logic
would be pretty much the same.
Good Luck!
Rich
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