"Steve" wrote in message ...
Gordon Wedman wrote:

Sure, these things are cheap but try making a masthead tri-colour out of
LEDs. Current price is something like $300US compared to $6 for a
halogen version.

Regulating the voltage going up the mastehead sounds like a good idea.
Since this does not involve that much current, certainly not 40 amps, I
wonder if you could build a small voltage stabilizer using a 7812
regulator IC for just the mast lighting circuit?

A 7812 will probably not provide a good solution because as the battery
voltage drops closer to 12V the thing will not beable to regulate
properly. I think it need about 2V about output voltage (i.e. 14v) which
your batteries will not be able to provide.

There are plenty of low-dropout regulators that only need a tenth of a volt
or so differential.

A better solution would be something with a switching regulator (see
national semiconductor page). This would be able to not only provide 12V
from a fully charged battery but also provide 12V when the battery drops
below 12V.

That would be either boost-buck converter or a buck-boost converter. I
like the boost-buck (Cuk) personally.

It would require a few more components but it would also be quite easy to
make big enough to support a large current.

Quite a few more compoonents. But keeping the switching noise out of your
radios is a headach for such a simple application.

Switching regulators are also more efficient than standard in-line regs
but if you are only looking at the mast head light it probably doesn't
matter too much.


Steve

"Doug Dotson" dougdotson@NOSPAMcablespeedNOSPAMcom wrote in message
...

"Meindert Sprang" wrote in message
...
"Doug Dotson" dougdotson@NOSPAMcablespeedNOSPAMcom wrote in message
...
How can running hotter be more efficient? I would think for a light
bulb,
the most energy dissipated as heat rather than light, the less
efficient
it
would be.

First, the hotter, the higher the content of visible light. The spectrum
of
emitted radiation simply moves up to shorter wavelengths when the
filament
is hotter, therefore a larger portion is in the visible range and less
in
the IR range.

Doesn;t less in the IR region equate to cooler running?

Not if you move "up" to the shorter wavelengths, which are indicated with a
higher color temperature.
The confusing thing is: higher color temerpatures are considered "cooler"
colors

Meindert