SparkFun Forums

[azog]

I'm wondering if I can drive these Luxeon LED's directly from an AVR microcontroller, or should I use a transistor?

[leon_heller]

What are the drive requirements?

Leon

[azog]

The LED says 350mA peak; the AVR I have in mind can source 40mA directly off a port pin.

[leon_heller]

That's a lot of current, you can't just connect it to an output pin. You need some sort of driver.

Leon

[NleahciM]

The LED says 350mA peak; the AVR I have in mind can source 40mA directly off a port pin.

Didn't you just answer your own question?

[azog]

The LED says 350mA peak; the AVR I have in mind can source 40mA directly off a port pin.

Didn't you just answer your own question?

Yea, but I was hoping to get a different answer than the one I gave myself.

[daemondust]

[phalanx]

http://i18.tinypic.com/6prgm5s.png

I would not recommend driving a Luxeon with a ballast resistor. At 350mA and a 5V source you will be dissipating about half a watt in the resistor which is very inefficient. If you are using a 7805 as a power source, you will also dissipate a lot of power there too since it is a linear component.

If your MCU has a built in comparator, you can very easily make a simple current controlled buck converter to drive it with around 90% efficiency. If not, there are a number of ICs available that will do it for you with minimum support hardware. For instance, the Zetex ZXLD1350 only requires a coil, sense resistor, and schottky diode: http://www.zetex.com/3.0/product_portfo ... o=zxld1350

-Bill