[sdiy] switching LEDS

[ASSI]

On Monday 11 January 2010, db wrote:
> Now I want to switch very big LEDs like 5-10 watts, so I'm sure I
> need to add something like a relay to keep it all safe and
> isolated. I guess I could use small relays, but is the best way to
> use some kind of solid state relay?

Driving high-power LED is tricky business if you want to use them 
anywhere near their maximum output.  You can't just "switch" them as 
they really need a constant current source.  Trying to provide this 
via a resistor would create a space heater and a linear regulator 
would still throw a considerable amount of heat.  You'll be much 
better off using a dedicated high-brightness LED driver IC that 
creates a constant LED current via DC-DC-conversion.  They come in 
many different configurations, you'll likely want to use one that has 
a single LED enable (so you don't need a digital interface like I²C or 
SPI just to switch the LED on or off) an analog dimming signal to 
optionally regulate the brightness.


Achim.
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