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100W RGB LED Driver Questions

dicky98

May 18, 2015
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May 18, 2015
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Hi guys

I'm new to the forum but a bit of a vetran to electronics

Recently I've been repairing disco lights and amplifiers (I also run a mobile disco amongst other things)

I've become interested in upgrading disco lights to LED - in particular upgrading low wattage LED fixtures to high wattage

I have a second hand LED light fixture here which has the right sort of optical path (in other words I will not obstruct the optics with a large LED/heatsink and has quite a bit of room in the casing for the additional power supply

What I want to do is replace the existing RGB LED (I think it is a 10W one) with a 100W RGB LED

This raises a few questons in my head that I am not sure how to answer....

Firstly I am wondering if a 100W RGB LED is actually 33W red + 33W blue + 33W green (or some similar combination)?

The data for the LED I was thinking of fitting is this one here http://www.ebay.co.uk/itm/New10W-20...t=LH_DefaultDomain_3&var=&hash=item233cc9862f

Which tells me 100W 32-35V 3000mA Genesis's 30MilChip

I know the 100W LED needs a driver - and they are easy enough to get for a single colour LED but how about the RGB one? I mean to say - a 100W constant current driver won't work because the current would vary depending on which combination of colours are actually illuminated?

I had a look at the drive to the existing 10W LED on my scope. As I would expect there is a common anode supply of 12V then each colour is being driven (by what looks like a FET though I didn't look at the device number/datasheet) and it looks like it is using some sort of pulse drive, but the frequency seems too low (approx 13mS or about 80Hz) which is much less than I would have expected to see in a PWM drive circuit, and the duty cycle looks all wrong too (almost all on)

The vertical scale is 5V/cm (center line is 0V) - see attached pic.

The existing disco light unit switches the RGB colours on/off - it does not dim or fade the colours.

I attach a photo taken from my scope for you to study. That's not actually PWM is it?

OK so I can see I have a few issues to get over: My options would seem to be:

1. Interface the existing (PWM?) drive to switch three higher power FETs so I can control the 100W LED in the same way the 10W one is currently being driven?

2. Buy some sort of off-the-shelf 100W RGB LED driver that let's me switch the colours on and off using logic level (TTL?) which I whould be able to interface from the microcontroller on the existing driver board

3. Build my own driver as speciifed in option 2

4. - over to you guys.......


Regards cooling - the existing light has an external ront mounted heatsink. I was hoping to replace this with a CPU Heatsink/fan as these seem quite capable of dissipating some high amounts of wattage

All help much appreciated

Rich
 

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BobK

Jan 5, 2010
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What you need is 3 dimmable 3A LED constant current drivers. The dimming inputs are typically either PWM or 0-10V analog. It sounds like your existing one is controlled by a 5V PWM signal.

Bob
 

dicky98

May 18, 2015
14
Joined
May 18, 2015
Messages
14
Thanks for the reply Bob

Why do I need dimmable ones as I only need to turn each colour on or off - or are you saying I need to set the brightness to either 100% or 0% ;-)

Are such things available off the shelf that are logic controllable so I can easily interface to the existing circuitry?

Hmm this has me wondering now, if that 100W RGB LED is actually like 3 x 30W why do I need 3 x 3A drivers as each 'colour' should draw something a bit over 1A with a total of 3A when all colours are lit????

Part of the problem I seem to have is that the data I have from the ebay listing doesn't seem to tell me anything about the RGB LED, only the single colour ones - see pic

100w led.jpg

If i need three drivers then do I connect the +'ve of all the LED drivers together to the common anode and then the negative of each one to the three cathodes? Is that gonna screw up the PWM or is the PWm drive only done on the drain side of the LED with a constant voltage on the +ve?

If I had a better understanding of how the LED driver works then i may have a better chance to figure out how to do this, I'm good with electronics, but seem to have a lack of knowledge in this instance. Google is not being my friend when I search (for example) 100W RGB LED circuit diagram

Can you clarify your answer further?

Rich
 

dicky98

May 18, 2015
14
Joined
May 18, 2015
Messages
14
Aha - A Bit more info now..... different LED but it is most likely similar to the one on ebay and at least I a have a bit more data on this one

http://www.dx.com/p/90w-90-led-rgb-light-bulb-module-10-series-and-9-in-parallel-281675#.VVofpFJHNcl

I don't know if this device is common anode or common cathode though

Can anyone help me with a circuit to drive that device so I can turn the three colours on/off with a logic level signal? Then I could interface this to the existing microcontroller in the light fitting no problem :)
 
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