"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