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I am new to electronics, want to prototype a LED light with 3 red led, 3 blue led and 3 white led. All the led are 1W high power LED. Each group of color can be controllable respectively and I want to change each group of color intensity through PWM.

I am using one arduino uno board, I have some questions about the design of this circuit

  1. so it is likely I need to use 3 PWM ports to control all three groups of LED, but since I have some other devices to link to the PWM pin, is it possible that I use 1 PWM pin to act like 3 PWM, any chips needed in between arduino and LEDS.

  2. and because it is high power led, how can I decide the right current regulator in between the LED and arduino.

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You could use a demultiplexer to split off a voltage into what's essentially a PWM signal for your LEDs. You mentioned that these are 1W LEDs, you're not driving it directly from the Arduino right? Anyways, assuming you're not driving directly from the Arduino, you could give a demux an input signal of HIGH and split it out into three branches, for each color. However, this also means that you will only be able to drive any single color at full brightness if the other two are completely off, and each change in one color's brightness will change the others as well. What you could do is limit each color to 33% duty cycle, but there will be some trialwork in getting the timing right. The TI TLC5940 is a popular LED driving IC that you might find useful, which uses a 3-wire serial interface to drive its LEDs.

If you're using a resistor to limit the current, you will want to figure out much current you want going through the LED (find it in the datasheet) and calculate out the value. Make sure any resistors are rated for the wattage they'll be running at. You can also look into constant current drivers for high power LEDs, they might work better. If you go with the TLC5940, I don't think you'll need extra resistors on the outputs.

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  • \$\begingroup\$ Hi,@justinrjy, I just looked the TLC5940, it is a 16 channel LED driver, does it mean I can control the intensity of 16 different LED lights individually \$\endgroup\$ – user824624 Apr 27 '15 at 15:05
  • \$\begingroup\$ Yes, you can control each of the 16 channels individually. The timing charts and control method is shown in the datasheet. \$\endgroup\$ – justinrjy Apr 28 '15 at 7:04

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