# RGB LED controller



## reedlaw (Mar 19, 2010)

I bought this controller to change RGB LEDs to different hues as a mood lamp:






It takes 12V DC and puts out 12V DC. It is supposed to support up to 6A of current. I have successfully tested it with low powered LEDs, but because the different colored LEDs take different voltages, they don't add up to exactly 12V so I tried adding a resistor. The resistors got very hot and some burned out.

Now I've got 3 of each of 1W red, green, and blue LEDs and I want to make a bright lamp but I'm not sure if I need a constant current driver. The online LED calculator says my circuit requires too much power and can't match a resistor to my needs.

My question is, can this PWM controller be used to power a 12V constant-current LED driver? I've seen some pretty cheap ones (I'm in China) that look like they were designed for flashlights (they have two pins at the bottom):





Should these work fine with a PWM source such as my controller or an Arduino?


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## Neondiod (Mar 19, 2010)

Hello!

I think the constant current regulator shall power the pwm unit.

Br


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## reedlaw (Mar 19, 2010)

The PWM unit is powered by a transformer like a laptop power supply--220V AC in, 12V DC out. I want to use the constant current driver _after_ the PWM controller to drive the high-powered LEDs. The controller outputs 12V DC which I hope can power the driver inputs which can then power the LEDs. What I'm unsure of is if the PWM signal will still affect the LEDs when the driver has a large capacitor and all those electronics in the path to the light.


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## TorchBoy (Mar 19, 2010)

The two pins of the driver are a standard MR16 12 V bulb fitting, but it seems to me to be rather unfair of you to expect anyone to guess from the photo exactly what the driver is and thus to be able to give you a definite answer. However, the capacitor and 4 diodes (acting as a rectifier) on the input side of the driver are because the driver can be used with AC. You don't need that, and it would get in the way if you were to feed it PWM DC.


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## Neondiod (Mar 22, 2010)

With the reservations I cant tell if your device work the same way: I have a similar rgb controller with an ir remote. It doesn't regulate the current or voltage, what I put in, it put out but hacked up in a pwm signal. It is rated 12V 4A, so this means that it can handle that power through it. 

It may be possible to have the current limiter after the rgb controller but I don't know if it can react fast enough or it will be some kind of interference? I would connect the latop power supply to the current limiter and now you have a defined voltage and current. This defined power I would put into the rgb controller and that should be whats comes out from it in a pwm signal, ready to drive a LED that can handle the current set by the constant current driver. 

BR


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## reedlaw (Mar 22, 2010)

In that case, could I dispense with the laptop power supply altogether? There are some constant current drivers designed to directly power 9 high-powered LEDs. But in this case, it seems there would be no way to ensure the voltage supplied is within the range of the PWM controller.


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## jason 77 (Mar 22, 2010)

where did you get that controller?

I would think that if that controller is putting out PWM voltages on each of the "color" outputs you could us those in as brightness controls for a constant current supply to each color LED... like below 






One of Dan's circuits from

http://www.instructables.com/id/Circuits-for-using-High-Power-LED_s/step8/a-little-micro-makes-all-the-difference/


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## Illum (Mar 22, 2010)

hmm...having a non-isolated power controller that eats AC sounds dangerous:candle:


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## Neondiod (Mar 23, 2010)

reedlaw said:


> In that case, could I dispense with the laptop power supply altogether? There are some constant current drivers designed to directly power 9 high-powered LEDs. But in this case, it seems there would be no way to ensure the voltage supplied is within the range of the PWM controller.


 
Yes, you should be able to dispense the laptop power supply if you choose to use a dedicated constant current driver that can be feed from mains. Why would't it be no way to ensure the voltage is in the range? The constant current driver should be market with current and voltage output.


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