Controlling multiple 1W LEDs with Arduino

Hi,

I am currently working on a project that requires me to control multiple 1W LEDs with an Arduino Uno. However, as the Arduino Uno is incapable of supplying the required current to power up multiple 1W LEDs, I am currently looking for a cheap and good LED driver to drive them.

Any suggestions would be welcomed as I have been stuck with no progress for weeks. It would be great too if I can be linked to any website that sells fabricated boards to drive multiple 1W LEDs as I am limited in my knowledge of electronics.

Thanks!

8 LEDs or series chains of individual LEDs per chip, you generally need 300 mA, for a 1W LED; the chip is rated to sink 500 mA per output and you need a current limiting resistor for each chain (or single LED) to determine that current.

1W LEDs are a sort of "boundary" case where you lose significant power in the current limiting resistor (or device) but it is generally not worthwhile providing individual switchmode regulators.

1W LEDs are a sort of "boundary" case where you lose significant power in the current limiting resistor

No you are wrong, the boundary is way lower than this and the problem is not one of wasting power but one of maintaining the required current in the face of the changing value of the forward voltage drop. With a current of 500mA using a resistor would mean a 6R resistor which it stupidly low to expect to act anything like a constant current.

Some links you might be interested in are:- http://forum.arduino.cc/index.php/topic,199156.0.html http://shop.elcojacobs.com/highpowerleds/powerleddriver https://www.tindie.com/products/Conceptinetics/4-channel-pwm-high-power-led-shield-for-arduino-035-07-1a/

shengye: .... 1W LEDs, blah blah 1W LEDs...

Some info on the LEDs might be usefult. "1W" isn't much of a description.

shengye: Any suggestions would be welcomed as I have been stuck with no progress for weeks. It would be great too if I can be linked to any website that sells fabricated boards to drive multiple 1W LEDs as I am limited in my knowledge of electronics.

http://www.ebay.com/itm/370632520478

Thanks for the replies everyone.

I am using a 3W total RGB LED (1W each) which consumes 350mA of current. (Is there anything more that I need to provide, sorry pretty new to such stuff)

Also, I am working with an Arduino Uno. I initially bought two TLC5940 to increase the number of PWM outputs but I realized that I need stronger LEDs. Which leads me to the 3W RGB LEDs. However, from the data sheet, it seems that the TLC5940 is unable to sink such high current ( Correct me if i am wrong).

Would it still be possible to use TLC5940 to increase the PWM outputs and then use a driver to drive the LED?

shengye: Would it still be possible to use TLC5940 to increase the PWM outputs and then use a driver to drive the LED?

Yes.

2n5551 transistors will handle 600mA of current - enough to give you some headroom over your 350mA requirement.

Thanks! Will check it out. So I can just use the TLC5940 to act as a PWM to control the on/off freq of the transistor which in turn controls the brightness of the LED right?

shengye: Thanks! Will check it out. So I can just use the TLC5940 to act as a PWM to control the on/off freq of the transistor which in turn controls the brightness of the LED right?

Yes. You'll need a pullup resistor on the transistor base, eg. 330 Ohm then connect the base to the TLC.

Almost any transistor will handle 350mA (eg. BC337, 2N2222 are very common).

shengye:
Thanks! Will check it out. So I can just use the TLC5940 to act as a PWM to control the on/off freq of the transistor which in turn controls the brightness of the LED right?

No you still need something to limit the current through the LED, as I have said before a resistor is not sufficient and the constant current sink in the TLC5940 will not come into play in that configuration.

Grumpy_Mike:

shengye: Thanks! Will check it out. So I can just use the TLC5940 to act as a PWM to control the on/off freq of the transistor which in turn controls the brightness of the LED right?

No you still need something to limit the current through the LED, as I have said before a resistor is not sufficient and the constant current sink in the TLC5940 will not come into play in that configuration.

This, too...

You still need an LED driver for each LED. The TLC is only there to increase the number of PWM outputs.