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Luxeon LED help - Uni project

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Spadez

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Hi!

Im new to this forum and I really need help with my project. I have been given three, 3W LED's to use in a lighting project. What I am going to do is have a green one, a blue one and a red one.

I want these luxeon stars to be enclosed in a lighting unit. Then I want to control all three of these luxeon stars as one entity, using a knob or dial to change the colour when it is twisted. Another possibility is to have a digital PIC controled way of changing the colour.. It will do this by varying the brightness of the LEDS to create the different colours (i.e if the green is dimmed the light will look more purple).

I need a circuit board to do this. I also need the board to allow the luxeons to be fully lit (as apparently 350ma wont lit the luxeons to their full potential). Ive looked everywhere. Can someone please help me out.

James
 
350ma is full brightness and they will require a heatsink. Pumping more current through them may shorten their lifespan and provide only a small increase in brightness. Use more LEDs if you want them brighter. I've seen a similar RGB lamp project over at electronics lab
 
For some ideas on a PIC pwm solution look at Microchip **broken link removed**.

You should use a 3 channel, constant current (350ma), high power led driver like the LT3496 pdf (and extra associated parts), to do the rest.
 
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PWM is used to vary the brightness of LEDs. There are hundreds of RGB 'mood-lamp' projects all over the web for PC, PIC, and AVR. There are even several here in past postings if you use the search function. I haven't worked with high wattage LEDs much, couple of whites, so can't help driving them. I do know there are several driver chips available (check some of the 'free-sample' threads here), think some part numbers were given in one.
 
Hi,

Thank you for the help. Ive found this:

Electronics Lab - Community

Its very similar to what I need, except that circuit uses a single RGB luxeon star and I need to use 3 x 3 watt luxeons, one for red one for green and one for blue.

Is it possible to adapt that circuit to do what I want?
 
I was under the impression that the driver transistors might need to be changed?

The 10K base resistors will have to be changed? Is so how do i work out their value?

The current limiting resistors on the collectors (4.7/10/15) will have to be changed? If so, how do i work out what is required?

Will the hex code have to be changed as well or will that run ok without modification?

Will the PIC be able to supply enough base current for the driver transistors?

Sorry for all the questions, thanks for the help.
 
This same thread is over at Electronics-Lab now.
The High Power Mood Light project is a mess of wrong values. I corrected them but the project was never corrected.

For a university student using Ohm's Law with the spec's of whichever LEDs you are using it is easy to calculate the proper resistor values and transistors.
 
I want these luxeon stars to be enclosed in a lighting unit. Then I want to control all three of these luxeon stars as one entity, using a knob or dial to change the colour when it is twisted. Another possibility is to have a digital PIC controled way of changing the colour.. It will do this by varying the brightness of the LEDS to create the different colours (i.e if the green is dimmed the light will look more purple).
I would normally not reccommend a micro for something so simple, but off hand I can not think of a good way to control all three from a single control.
 
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