Tony Nixon wrote:
> Mark Boyce wrote:
> >
> > Hi all,
> >
> > Hope this isn't too off topic for people :-)
> >
> > I need to be able to switch/dim some lighting from a pic
> > controlled system.
> >
> > The actual target lighting will be pairs of 12v halogen spots
> > such as you find in most low-voltage desk lamps or alike.
> >
>
> Correct me if I am worng, but aren't halogen lights designed to work at
> full power to generate enaough heat to function properly.
>
> --
> Best regards
>
> Tony

They seem in my experience to work pretty well dimmed (I ran a pair of
300W units in the ex-girlfriends' front room, from 1% or so at night, to
75% all evening every evening, only up to full power for occasional high
lighting needs.)  We used an X-10 controller (She could run that,
barely), I think we had to replace 1 bulb in 2+ years or so?

I have to replace 60W bulbs here at home, FAR more often than that <G>

You CAN set your place on fire, if you put fabric too close to a Halogen
light (Don't!)

To run 12V halogens (24V or 12V), another (less efficient) way to go
would be to use an LM317, these can be rigged for digital control using
multiple resistors (See the data sheets/app notes.)  A PWM PIC is a
better way to go, I now know, when I did that LM317 project I was just
starting to learn PICs, back in the early PIC Mists of time <G>  Needed
something fast & foolproof, it worked but DID get sorta warm in
operation <G>  (It's a linear regulator, so you get Ithrough * Vdrop
watts dumped, lost as heat, in the regulator.  A heat sink's one
solution, PWM is more efficient though.)

I *really* think you meant 24V not 240V to operate a pair of 12V
halogens, right, Mark?  <G>

  Mark

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