3W RGB driving questions.

I'm working on making four RGB LED lights for my room. I already have a program working to control the lights with my computer. The problem now is I don't know exactly what to get to power the lights and the best way to wire them up.

I'm looking at 4 of these LEDs http://www.superbrightleds.com/moreinfo/component-leds/vollong-3w-rgb-high-power-led/899/ so each LED would be 1 light. I know I need some kind of transistor to control these with the Arduino, but I'm not sure what kind exactly. I want to be able to control each light individually so I'm thinking of using 12 pins (3 per light) and I do have the Mega so I have enough PWM pins to do that. Most people seem to put the transistors after the LED so I want to run four wires to each light with the positives being common and then the negatives each go to a transistor and are controlled by a pin. Are there any concerns with wire gauges running about an amp through the common positive?

As far as powering them, do I need a specific LED driver or can I just use something like this http://www.mouser.com/ProductDetail/Condor-SL-Power/CENB1060A0551F01/?qs=sGAEpiMZZMtpkqKkT5w3uoo7j8gXTa779gfYRbfBccQ%3d ? 7 amps should be more than enough and gives me room to add more lights in the future.

I plan on putting the LEDs on a piece of aluminum sheet that's about an eight inch thick with a pattern similar to this http://www.acehardwareoutlet.com/ProductDetails.aspx?SKU=998013046. Would this be enough of a heat sink for these, or do I need more?

You need to check the voltage, some power LEDs can run directly from 5 volts, for instance 2 red 3W LEDs in series. Very often a constant current drive indeed is used.

I’d doubt you can directly run R and G and B directly from 5v.

I’d also recommend to use a cooling grid with integrated fan, maybe not the way like seen in my photo (4x 3W LEDs), but this is about the cooling capacity of these grids. Having the fan running at moderate speeds, the grid heats up to maybe 60 C where the LEDs are, and all of the assembly heats up to 40/45 C.

If you only use passive cooling, you need much more area/much larger cooling grid. Only a sheet maybe works for smaller 3W LED, not running at full power, if you have 10W LED, it’s difficult to handle the heat only having a metal sheet.

By the way the electronic transformer in the photo just made “pop” after some weeks, I wasn’t able to locate the broken part but I guess it’s the switcher IC. Rated for 50W but I highly guess, built using cheap components (When I just bought it, also the bridge rectifier burned out after 2 minutes).

I don’t know if maybe I sent too much current through the LEDs but they are rated for upto 2.8 volts.

The official way indeed is to use a constant current driver.

And don’t use transistors, you loose too much power, use digital MOSFETs, they have much less voltage drop.

About the wires one time I used ordinary bell wire for 240 volts @ 3 or Amps, it can carry nearly a kilowatt. Thin PCB traces maybe can’t carry high currents. If you make some loops of the wire when it is carrying the current, and it heats up a little, you can get an idea. Also if the wire has no air circulation, the current it can carry is less. Shouldn’t be a concern for 3W LEDs.

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if you can wait out the shipping time.. I think dealextreme has these for a bit cheaper (and free shipping)

@takao I will wire up the LEDs in parallel to the power supply so the voltage shouldn’t be a problem, and each LED draws about 1 amp at max power so 7 amps should be plenty. I just don’t want to have to spend like $70 on a constant current LED driver if it’s not absolutely needed.

Also what MOSFET would you recommend because I know very little about those?

PWM pins... means pulse width modulation .... that gives very gud effects in RGB... 1st birthday party ideas

Would a MOSFET like this work http://www.newark.com/vishay-siliconix/irl510pbf/n-channel-mosfet-100v-5-6a-to-220/dp/63J7799 ?