Hey guys I've been looking for a while and I can't find what I need. I'm looking for a 3 channel LED driver board with an output enable for all three channels (or something similar) so that it can be easily controlled from an arduino. I want it to be powerful enough to control a 3w rgb led like this one http://www.dealextreme.com/p/3w-led-emitter-on-star-multicolored-rgb-4530 but it would be nice if it had enough power to control more than one (in series probably). I don't want anything super complicated or expensive, the 10 dollar range would be nice. A mockup of what I'm looking for is below. I've had enough bad experiences with supplying power to high power LEDs that I just want to use a premade board.
I guess driving several RGB-Leds with common Anode/Cathode will be a problem. The only way you can drive those is parallel (which needs a driver able to cope with more mAs). If you find a led giving you access to all individual anodes/cathodes you can drive multiple when connected in series.
Search for a 4 channel 'Motor Drive Shield L293D'.
Your LED will need a heat sink and 3 current limiting resistors otherwise it'll be a dazzling light display for a fraction of a second, and then nothing but the darkest darkness.
Search for a 4 channel 'Motor Drive Shield L293D'.
No please don't, this it a totally unsuitable way to drive a high power LED, you need a constant current source NOT a current limiting resistor.
The drive requirements for LEDs are the same regardless of power. Choose resistors that limit the current at 100% PWM to less than the published spec.
If you want high stability for subtle colour mixing then constant current is the way to go because it negates the thermal effects of the adjacent LEDs.
The drive requirements for LEDs are the same regardless of power.
I don't know where you get such rubbish.
No they are not.
The forward volts drop will change over a much wider range with a power LED, not least caused by the wider range in temperatures. Also the resistor value is going to be much lower and therefore will act much less like the constant current supply of higher values. In other words the linear section of the circuit has a much smaller influence the smaller it gets.
these are good. maybe a bit expensive depending on what your doing but very versatile. The link is for a 1000mA version but they come in a good rage. For a 3w i think you would need around 350mA i think. Check the different mA for the different colors and make sure you get the right one's. But the great thing is you need no external components. They have a PWM input at 1.25 volt so you do need some resistors on your outputs but that's it. The say they are 95% efficient which has got to be better than getting a load of big resistors hot. They also go up to 20 volts or more depending on which one you get so you can string a load in series if you want as well.
Choose resistors that limit the current at 100% PWM to less than the published spec.
This works ok in some situations but not well with power less. Not only do you have all of the problems that grumpy_Mike mentioned you would also need a fat resistor with a big heatsink for a power led. If your less are 30 watts you will need a 30w or higher resistor which arent that cheap, and are definitely not very efficient.
And I've learned from experience what happens to power less with only resistors. It's not pretty
As suggested, use a constant current source. If you go for a transistor resistor configuration or a linear regulator you are going to be dissipating a lot of heat. The first link on eBay looks very much a constant current driver. There are many other manufacturers that have even more compact solutions like the ones posted on the farnel link or from recom.
