"Terry Spragg" wrote in message
news
Steve wrote:

My understanding is that if you can provide 12VDC the bulbs will last
longer. One interesting thesis that I am not sure about but has some
element of truth was that to low a voltage is also bad because halogen
bulbs rely on getting hot enough so that some weird chemistry occurs that
allows the filament to be re-built from the boiled off metal. This
apparently is the trick to halogen bulbs and why they can get much hotter
than standard bulbs hence be more efficient.

BTW have you come across IRC halogen bulbs. They are very efficient (a
20W IRC halogen is the same light output as a standard 35W halogen). I
have just put some in and the place is like a stadium its so bright.

Steve

Glenn Ashmore wrote:

I have heard that 12V halogen bulbs do not last long running at
absorption
charge voltages. A couple of smart regulators (Ample Power being one)
have
a halogen lighting feature that limits alternator output voltages. I
picked
up a couple of 40 amp DC/DC converters on eBay and was planning to use
one
to power the electronics. Would it be worth while to use the other for
the
lighting circuits? Especially the nav lights which are harder to change
out.


Forget tungsten.

White LEDs are now common and cheap and 5 times as efficient as
incandescent, and will get better quickly. Vehicles are all going to LEDs
soon, prick these words well, Lothario.

Last week at the dollar store, I got a white LED with 2 - 3volt lithium
batteries in a plastic squeeze light for my key ring for a buck. I don't
know about the LED, current / life specs wise.

It's bright, it's white, it's compact and cool. I don't know how long it
will last, but it's a beaut!

I'm gonna make a 6 v pocket flash with a dimmer out of a cigar tube after
the lithiums cells die, just for fun.

My mini-flourescent 100Watt equivalent replacement lamp touted for long
life died in my bathroom yesterday, after about a year of ordinary use.

Rip-off!

Terry K


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?

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

"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