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More suited for SEB?

Discussion in 'Electronic Design' started by Neil, Oct 29, 2004.

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  1. Neil

    Neil Guest

    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?

    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..)

    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? I'm
    assuming I can just connect all the individual LED drive circuits in
    parallel??

    Should I just get some gel filters?
     
  2. John Larkin

    John Larkin Guest

    Oh, 800 or so.

    John
     
  3. Rich Grise

    Rich Grise Guest

    You can't get much easier than a wall wart. ;-)
    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!
    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 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.
    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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