P3D Re: White LED efficiency.

[Tom Hubin <thubin@xxxxxxxxx>]

Greg Erker wrote:
>   This caving LED light page:
> http://www.hdssystems.com/NSSLEDArticle.htm
> 
>   has an article about LED lighting.

I just read his article. Of course, he is biased. He has a product to
sell. Most of what he says is true but he leads you to believe things
that are not true.

For example, he says that using a series resistor to limit current to a
LED wastes power. He does not say that using a voltage regulator or
current regulator wastes more power. Tsk, tsk, tsk.

As the battery dies the regulators lower their resistances to permit
full power to the LEDs. Until the battery is below some voltage and then
the regulator fails and the LED blacks out.

The series resistor does not change as the battery dies so less power
goes to the LEDs as the battery dies. The LEDs become dimmer as the
battery dies but the battery will last longer because it is being
drained at a lower current. The LEDs will remain lighted longer than
with the regulators. No sudden regulator blackout either. Fewer parts.
Cheaper parts. More reliable parts.

If you had a low loss switching voltage to current converter you could
probably get more life out of a battery. But I do not know what that
would cost or even if low loss devices like this exist. 

Tom Hubin
thubin@xxxxxxxxx

Tom Hubin
thubin@xxxxxxxxx