LED question...

[Sender]

I'm going to hook up 2 white LEDs to act as a 'backlight'. I want to limit them to 10mA. So I'll be using a 700ohm resistor for current limiting (15V source, with 8V of voltage drop [4v for white times 2]).

The question I have is about the Vmax parameter of the LED. How do I work around 5V max volts if I have a 15V supply? Am I going to have a make a voltage divider to step down the 15 to 5. If I do this, the voltage drop is going to be more then supply voltage..... :?

Help!!!

 

[bcarso]

LEDs are essentially "current-controlled" devices---you are not applying 15V to them, and you will be fine without anything more than the dropping resistor.

 

[NewYorkDave]

I'm not sure I understand the question. The current limiting resistor should be sized so that the desired operating current is passing with the nominal forward voltage across the LED. The voltage across each LED will not reach Vmax unless they stop conducting.

 

[Sender]

[quote author="NewYorkDave"]I'm not sure I understand the question. The current limiting resistor should be sized so that the desired operating current is passing with the nominal forward voltage across the LED. The voltage across each LED will not reach Vmax unless they stop conducting.[/quote]


Thank you, you've answered my question.