"Meindert Sprang" wrote in message
...
"Gordon Wedman" wrote in message
news:Naa5f.17849$y_1.2003@edtnps89...
Meindert, Terry, Chris
Thanks for the info. Didn't know they would take something simple and
complicate it. Switched to save power? How much power are we trying to
save anyway?

Ok, I'll do some math: A typical high-power LED draws 500 mA at 3V. If I
use
a ballast resistor to connect this LED to a battery at 12V, 9V will drop
across the resistor at 500mA, which produces 4.5Watts of heat, which is
quite substantial. The total power drawn from the battery is 6 Watt.

With a switched regulator, there is (hardly) no voltage drop, so the power
the LED uses (3V * 500mA = 1.5Watt) is the same as the power drawn from
the
battery. So more efficiency and the regulator also compensates for varying
battery voltage which results in longer LED life. LEDs are quite picky on
the proper voltage. 1/10th of a volt more than specified can shorten their
lifespan from 50,000 hours to a few 100. This regulator prevents this.

Meindert

Not to be argumentative but.........
It seems to me that a typical masthead lamp uses about 20 watts. So with
the simple LED setup we are going from 20 watts to 6 watts. Not good enough
though.
We have to add some electronics to get it down to 1.5 watts (and add $$$ to
the cost). Oh by the way, you can't transmit on your VHF now.
It just seems that some companies are gold plating the faucets and then not
doing a proper job of it too boot.
Lastly, how big is a 5 watt resistor? I don't think this is all that much
heat. What about the heat from the 12 and 20 watt cabin lamps?